June 15, 2021 • 48 mins
Daniel and Jorge go through the crazy story of missed opportunties, accidental observations that led to one of the greatest science discoveries of all time.
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Speaker 1 (00:08):
Hey, Daniel, do you know what I don't understand about
winning a Physics Nobel Prize? Oh yeah, what's that? Well,
you know, to be honest, some of them seem kind
of easy in hindsight, be easy to win a Nobel Prize. Yeah,
I mean, like for Einstein, all he had to do
is analyze someone else's experiment. It was just one idea
that he had one day and boom, Nobel Prize. I
guess that's easy if you're Einstein. Well, I mean also,
(00:31):
like the discovery of X rays was totally by accident
and it took about one day of work for them.
That's true if you happen to have X rays around,
or like the Higgs boson. You know, like college physics
major can do that kind of math. All right, you win.
I admitted getting a Physics Nobel Prize is easy, So
then why don't we have one? Because we haven't tried.
(00:52):
It's win one today, Daniel. Alright, great idea, Einstein, let's
do it. Hi. I am more hammy cartoonists and the
creator of PhD comics. Hi. I'm Daniel. I'm a particle
(01:15):
physicist and I have not yet won a Nobel Prize.
But maybe any day someday will be the day. Do
you wake up every day thinking, maybe today's to day
I'll have my great idea. I don't expect it to
ever happen, but I do love those stories when somebody
has a moment of insight or stumbles across something weird,
and that morning when they woke up and had their
oatmeal or whatever, they had no idea that it would
(01:37):
be that fateful day. Maybe that's the key. It's the oatmeal.
And maybe it's a special kind of oatmeal. Daniel like
a radioactive oatmeal. Bitten by his radioactive oatmeal, he gained
his proportional intelligence. There you go. Maybe that was a
nice secret. I think when people say you're as smart
as a bowl of oatmeal, they don't mean it as
a compliment. Well, I think that's very disparaging of oatmeal,
(01:58):
because you never know, there could be sentient genius oatmeal
out there in space. They could be our next alien overlords.
Yet another sci fi pitch for Netflix put it on
the list. All right, Well, welcome to our podcast Daniel
and Jorge Explain the Universe, a production of I Heart
Radio in which we try not to turn your brain
into oatmeal as we talk about all the amazing things
(02:19):
that are out there in our universe, all the things
that we have painstakingly uncovered in our search to reveal
the fundamental nature of matter and radiation and everything in
the universe, and all the things that science is still
picking at, all the big questions that are out there,
all the discoveries that might be far into the future
or just around the corner. That's right. The universe is
(02:42):
full of mysteries, full of big questions and wonderful discoveries
just waiting for us to find them and possibly get
a Nobel price for finding them in the congratulatory bowl
of oatmeal. And sometimes the answer to those questions is
already out there. It's beaming down at us from the cosmos,
or it's in somebody's data. They just don't even recognize it.
(03:04):
And sometimes those Nobel prizes come just from putting one
thing next to the other, from finding that the answer
to a question is already out there. Yeah, because technically
all of the secrets of the universe, all of the
great big truth about it, are out there for us
to discover. I mean, it's not like they don't exist.
They're there, which is haven't seen them or having discovered
them or having known where to look. Yeah, you know,
(03:27):
that's a really fun question, Like is it actually possible
to unravel the nature of the universe without ever leaving
the Earth? Just by watching this guy's It's sort of
incredible what we have been able to figure out about
like far flung corners of the universe, the way galaxies
expand and collide and do all sorts of crazy stuff
without ever having left the Earth. But I wonder if
(03:48):
it's possible to actually figure out like all of it,
to get all the way down to string theory and
quantum gravity without ever going anywhere else. It would be
pretty cool if all that information was beaming down on
us right now. Are you saying, like, are we maybe
in the wrong place, Like if we were somewhere else,
we could see the secrets of the universe, you know,
Or maybe they're all in one box but in another
(04:10):
part of the galaxy. Yeah. Or it might be that
you need to do some kind of experiment like smash
black holes together at very high speeds in order to
get the answer to some question. Or might be that
you need to be able to look inside a black hole,
which we can do from here. Maybe you need to
be nearby it in order to decrypt the quantum information
in the Hawking radiation. It might not be possible to
(04:30):
gather all that information from Earth. Or maybe it is.
Maybe if somebody was smart enough, they could figure out
all the secrets of the universe and just from the
data we are getting today. Yeah, hopefully not by getting
us near a black hole or by smashing a couple
of black holes together here on Earth. That's hounds kind
of dangerous. Anything in the name of science not worth
a noble prize. Well, you know, everybody makes their own
(04:51):
judgment call on that. Please, physicists, check with the rest
of us before you make those kinds of judgment calls.
I know this is important for you, all of you,
but you know, we might I'd have other priorities, your
priorities to get to name the black hole machine, right,
I want to be alive to me and to call
it that, you know. But yeah, the history of physics
and science here on Earth has a long and interesting history,
(05:13):
full of amazing discoveries. And some of them happened kind
of by accident, right, Oh, lots of them happened by accident.
People stumble across stuff they didn't even know to look for,
see things they don't understand, and only later realize that
they contain secrets of the universe. So today we'll be
covering one such story of an amazing discovery that really
kind of illuminated in a very real way the beginning
(05:36):
of the universe. Absolutely, it's some of the oldest light
in the universe, and it tells us a lot about
how the universe began and how hot and dense and
crazy it was billions and billions of years ago, and
it was almost overlooked and mistaken for pigeon poop. Wow,
that is a big oops there for the physicist. So
(05:56):
today on the program, we'll be talking about how was
the cosmic microwave background discovered? Now, Daniel, this is the
famous CNB, right, this is the famous CNB that has
taught us so much about the nature of the universe.
It's not the CNB R as they call it in
(06:17):
the Marvel universe. You have a problem with that, Well,
the scientists in the Marvel universe can call their CNB
whatever they like, but out here in the real universe,
we tend to call it the CMB. Just the cosmic
microwave background, meaning like it's the background basically of the universe.
It's everywhere, It's all around us. Photons from the early
universe plasma are zooming all over the universe in every direction,
(06:39):
no matter where you look. That's what we mean by background.
It's sort of just like always, there's everywhere. Yeah, And
it has a long and interesting history of people thinking
it was there but not seeing it, or seeing it
and not thinking it was there. It's kind of an
interesting and dramatic plotline, right absolutely. And it's the kind
of thing that could have been discovered very easily decade
(07:00):
before it was, and in fact, it was discovered several
times without even being understood, and so it's sort of
like a story of missed opportunities and the folks who
ended up winning the Nobel Prize for finding it could
very easily not have So it sounds like a pretty
intriguing story. So we'll dig into that and go over
every detail. But at first we were curious about how
(07:21):
many people know how this amazing discovery was found. So,
as usual, Daniel went out there into the wilds of
the Internet and asked people if they knew how the
cosmic microwave background was discovered. And so if you would
like to be interrogated about physics by a physicist without
the opportunity to consult any reference materials that sounds fun
to you, then please email me two questions at Daniel
(07:43):
and Jorge dot com. Here's what people had to say.
I think it was around the seventies. Whenever it was,
they feel was a very powerful telescope maybe radio telescope
to look at something else, and then they heard or thought, so,
I'm like what they thought was noise from a local source.
They even thought it was the pigeons that were nesting
in the telescope and actually had a big job clearing
(08:04):
that out, trying to get rid of it, but no
matter what they did, couldn't get rid of it. And
that but obviously eventually they realized it wasn't local at all,
but from fort almost fourteen billion light years away. The
NBA two words Hubble telescope. Okay, that's a tool, not
an answer. Aliens told us about it, and they also
told us where to look. So we pointed the Hubble
(08:24):
telescope at the cosmic magawave background radiation and that's how
we discovered it. I haven't really heard about it, just
as an assumption, maybe e when we were trying to
respond some kind of radiations. I think the background radiation
was discovered by accident. Hadn't had nothing to do with
someone using their microwave up and to make eggs. But
(08:47):
I think it was World War Two. Weren't they doing
radar experiments and they discovered this noise? But I think
it was by accident. The cosmic microwave background was discovered
by two scientists working at Bell Labs in New Jersey
who were investigating a strange buzz they picked up when
actually working on something else. I think it was discovered
(09:08):
around nineteen sixties as one of the first discoveries of
radio astronomy. After making sure it wasn't the error in
data or in measurements, there was a lot of theorizing
what did what it means and why the signal was
actually hurt quite possibly with a radio telescope. Maybe astronomers
or scientists were looking at like certain stars or something
(09:30):
they're like, hey, these guys are given off a lot
of radiation, and then they looked at the stars and
they're like, oh, it's not the stars. Put something around it.
But there's nothing around it, so they're like, oh, what
if we just focused on the space around it? And
then they focused on the space. All right, A lot
of versions of the story here from the public. A
lot of people seem to know something about how it
(09:51):
was discovered by accident. Yeah, including apparently aliens told us
about it. I like, how this president, you said two
words hubble telescope bam drops to my and aliens. Oh,
by the way, also aliens, well, how else do you
know where the point your hubble telescope? Right? The aliens
have to tell you it makes perfect sense. It's pretty
surprising how many people hadn't heard about this. And also
(10:12):
I knew a little bit about it. You know, generally
people seem to know that it wasn't like this intentional thing,
like there was some element of accident to it. That's
exactly right. And it took a long time for people
to even know that it should be there and know
that we might be able to see it. So there's
sort of like progress and back steps and forward steps
on the theoretical side as well as on the actual
(10:34):
like observational side. All right, well, let's get into this
story then, and maybe take us back Daniel, because I
imagine this story starts in the early nineteen hundreds, and
you know, we were sort of just starting to discover
how big the universe was and that it maybe came
from a big bang. You know, what were we thinking
at the time, and what did we know? Because you know,
(10:54):
I imagine that the idea that there's some background noise
in the universe is not that surprise think to think about,
but it having some special meaning maybe is Yeah, so
that we have to go back to basically Hubble. Hubble
is the one who figured out that the universe was expanding.
Before that, people thought that everything was just sort of
like hanging out in space. Things hadn't changed in hundreds
(11:16):
or thousands or billions of years. But Hubble discovered that
there were other galaxies out there and that they were
moving away from us faster and faster, and suddenly that
made the universe dynamic instead of static, like things were
definitely changing. And people had two totally different concepts of
ways to explain what Hubble saw that the universe was expanding.
(11:36):
One is the idea that's very familiar to us that
if the universe is expanding, then you run the clock
backwards in time, then it must have been more dense,
must have been more compact, must have been more squeezed
together in the beginning, and you can sort of track
it back to a very early moment when you reach
like infinite density, the singularity. So this is the big
bang idea that the universe came from some like huge
(11:58):
early expansion, and what we're now is the remnants of that,
the continued expansion of the universe. So that was one idea,
this big bang idea, right, because we we saw the
stars and the galaxies right now, they're all moving away
from us. So you know, the ideas that if you
rewind then at some point everything was crunched together. Yeah,
but some people didn't like that idea. They thought that's
(12:19):
ridiculous for the universe to have a beginning and for
it to begin in some sort of big bang. And
in fact, the name big bang came about as a
sort of like an insult, and they were like trying to,
you know, make that idea sounds silly by calling it
a big bang, and instead they preferred a steady state
theory of the universe. That's sort of hard to have
a steady state idea of the universe, that the universe
(12:40):
like isn't changing on the largest scale. When you see
that it's expanding, you know, how could that possibly be
If things are expanding, don't they get less and less dense. Well,
their idea was that there was some like source of
new stuff in the universe, that stuff was constantly being created,
and that was like refilling the universe. So the universe
was expanding but at a constant density because there was
(13:01):
some like thing that was like topping it off all
the time. That is sort of what we think of now,
but back then it seems sort of counter to the evidence. Well,
that's interesting that you say that you're right that we
know that the universe is expanding and that there is
more space being created, but the universe is getting more
and more dilute. The steady state theory involved like the
creation of more stars and galaxies and more stuff in
(13:24):
the universe to keep like the density constant. So the
steady state theory was like, well, let's figure out how
to make the universe so it's not getting more and
more dilute, that it's always been this way and live forever.
They were thinking, like, the density of the universe doesn't
change it's somehow expanding, but the density is not changing. Yeah,
because somebody's like pouring more syrup onto these pancakes all
(13:45):
the time, and so even though it's dribbling off the edges,
you're keeping the same amount of syrupe on top of
your pancakes. That's my big pancake theory of the universe.
I think you messed up that analogy. I think it's
it's more like the pancakes getting bigger, and so somebody
must be for more sarapes. There you go, all right there,
all right, right, that's a more delicious, very breakfast theme
(14:05):
physics analogy today. The oatmeal pancakes. It's the most important
physics meal the day. Wait till you hear about my
waffle based observation ideas, and might have to be another episode, Daniel,
I'm stuffed already. And so these were some of the
ideas people were bouncing around, like what does the expansion
of the universe mean? Did it come from some early, hot,
dense point or is there someplace where the universe is
(14:27):
creating new stuff so that things don't get less and
less dense as time goes on. I guess why were
they fighting this idea of a more you know, kind
of empty universe, like why couldn't the universe beginning more
and more dilute. I think they didn't like the idea
of a beginning. It seems sort of counterintuitive. They prefer
the concept It seemed more natural to them to imagine
the universe had always been here, because if there's a beginning, then,
(14:50):
as you know, there are big questions about that beginning,
what came before and what caused it? Why do we
have a beginning? You can avoid some of those things
if you imagine the universe is just always been this way.
Like if you don't accept that the universe could have
a beginning, then you have to make something up, like
where is all this syrup coming from? Yeah, there are
always more questions, but you know, it was sort of
an aesthetic preference, and so you had physicists on both
(15:12):
sides of the issue, some arguing that the universe must
have started with a big bang and others suggesting that,
you know, stuff was constantly being made in this steady state,
and so that's what people were thinking about. They were like,
where does the stuff in the universe come from? And
they were trying to understand for example, where heavy stuff
in the universe came from, Like, where does all the iron,
where does all the nickel and all that stuff in
(15:33):
the universe come from? Was it made during the Big Bang?
Or is it somehow made somewhere else and being like
poured into the universe somehow? I see, because it could
have been made in the Big Bang, right, like the
heavier elements could have been forged in that hot, tense
initial moments. That's what people thought in the early part
of the century that maybe in that incredible heat from
the Big Bang, you could have made iron, and you
(15:55):
could have made silicon and oxygen, and maybe all the
elements were fused in that initial time period. So people
spent a lot of time doing theoretical calculations of how
hot it was back then in the very early universe,
What was the temperature, what was the density? Were there
the conditions needed to make all of the heavy elements.
So that was the reason they started doing these calculations,
and they realized, Wow, in the very early universe, there
(16:18):
must have been this very very hot plasma, and that
plasma must have glowed the way plasma from the Sun,
for example, glows, And then the universe cooled, and at
some point that plasma becomes transparent because all of the
ions and it capture electrons as they cool and they
become neutral, and then it's transparent. So what they were
wondering about was all that energy, all that light that
was now flying around the universe. Was there enough light
(16:40):
there to like make the heavy elements? And they did
a bunch of calculations and they decided, no, it wasn't possible.
And now, of course we know that those heavy elements
were not made during the Big Bang. The Big Bang
mostly made hydrogen and helium and very tiny amounts of
heavier things. The heavier elements were made later in stars,
but they didn't know that at the time until they
did these calculations. But how did they know that? You
(17:02):
couldn't have made the heavier elements because there just aren't
the conditions, Like you can't make iron, for example, under
the conditions just after the Big Bang, like it needs
to be hotter and denser. You need the conditions inside stars.
But wasn't the Big Bang infinitely dance and super duper hot.
It was, but not for very long, you know, And
so like it took time for the basic particles to form.
(17:23):
You needed like quarks to shake out of it, and
then those quirks to get bound into protons, and then
those protons to find electrons and that's basically all that happened,
and then things cooled down. There was very very quick
early expansion. Remember the Big Bang itself is an expansion
that lasts like ten of the minus thirty seconds. I see.
There wasn't enough time to make the heavier elements, is
what you're saying. But just enough time to only make
(17:45):
hydrogen and helium, just enough to time to make hydrogen
and helium exactly and little trace elements of what comes next.
And so the other elements were later made in stars.
And this is where cosmologists kind of lost interest. They
were like, all right, so there must have been this
hot play and it must have generated a bunch of light,
but we're not interested anymore because that couldn't have made
the heavy elements. That was the question they were asking.
(18:08):
So they had the idea that there might be this
light from the early universe flying around, but they didn't
care because it didn't answer the question they were asking
At the time. They were more interested in, like had
the planets come about and had its stars and galaxies,
like the stuff that you can actually kind of that
is interesting to them, at least at the time in
the universe. Yeah, so it's very much motivated by like
(18:30):
what questions scientists are asking. Sometimes you stumble across an
idea and you don't realize, oh, this could actually be
really interesting and important for a totally different question. They
were focused on, you know, how do you make these
heavy elements? And on top of that, nobody imagined that
you could even see this light. Even if they thought,
well that light is cool and if you could see it,
it would prove that there was this hot, dense state
(18:51):
in the early universe. They didn't imagine to be possible
to see it today, and so they just sort of
like wrote it off and cosmologists sort of like moved on.
This is acculation is done in the forties by some
guys named Alpha and Herman and George Gammao, and they
did it, and people thought, well, I guess you can't
make heavy elements in the Big Bang, and then they
just sort of turned to other stuff. They thought the
Big Band was too boring. They're like, you know, like
(19:14):
all right, yeah, that's where the universe came from. It
was a big flash, but nothing interesting happened, nothing interesting
that we could see today. These photons, they started out
really hot, you know, like thousands of degrees kelvin, but
then they got cooled down as the universe expanded. They
got stretched out as the universe expands down to very
very cold temperatures, which means long wavelength, which means radio waves.
(19:37):
And so at the time, radio astronomy was like really
a brand new field that had just begun a few
years earlier. So nobody imagined you could actually detect these
faint signals. Nobody even bothered to propose that somebody do that.
All right, well let's get into a little bit more
detail about what they were expecting to see and then
how it was accidentally discovered. But first let's take a
(19:59):
quick break. Alright, we're talking about the cosmic microwave background
and how it was discovered. Now, Daniel, some of our
listeners might not know exactly what the cosmic microwave background
(20:21):
is or where it comes from. You want to go
as a quick recap of what it is and what
exactly it is that we're seeing when we look at it. So,
the cosmic backgrounwave background are photons from about three hundred
eighty thousand years after the Big Bang. Right, big Bang happens,
things are really hot and dense and stuck together, and
the universe expands, which means everything is getting more dilute
and more cool. And by about almost four hundred thousand years,
(20:44):
the universe had cool to the point where atoms could form,
like electrons were slow enough that they can now be
captured by protons and turned into hydrogen, for example. And
that means that the universe became transparent. So there's this
moment when the universe goes from like really hot and
glowy but opaque too, slightly less hot and slightly less
glowy and transparent. Right, it becomes like glass all of
(21:07):
a sudden. So what happens to those photons that were
made just before the universe became transparent, Well, they were
flying around and they're still flying around, and fourteen billion
years later, most of them are still flying around. And
so they were everywhere because the Big Bang was everywhere,
and this plasma filled the entire universe and filled it
with these photons. So that means that everywhere, all around
(21:30):
us are these photons not from the Big Bang, itself,
but from this hot plasma that existed about four hundred
thousand years after the Big Bang. Yeah, I'm thinking like,
it's like you're in the middle of a giant fire
and then suddenly the fire, everything are all around you
becomes transparent, and so you sort of get that one
last you know, flash of light from that fire right
(21:52):
before the universe became kind of solid. And because it
happened everywhere all at once, then there are always photons
wherever you look. Right, we look out and we see
this just in the night sky. Right, if you point
to a radio telescope to the night sky in any direction,
you see this because there's always a place where fourteen
billion years ago, almost a photon was created and it
(22:14):
has been flying towards us ever since. And as time
goes on, we're seeing these photons from further and further
slices of that early plasma. So we're always seeing it.
We always will see it. And so you were saying
that in the beginning of the Nine DS and through
the middle of it, we sort of knew this story.
We knew that's what had happened or possibly happened at
(22:34):
the Big Bang, and what happened to all those all
that light. But you're saying, nobody really cared about seeing
this light. Nobody imagined that you could write. Nobody thought, wow,
you could actually go and detect this stuff. It seemed
like it would be a really faint signal and you
need really impressive technology. And so people just sort of like, well,
I guess that existed, just like lots of other things
probably existed in early states of the universe. Doesn't mean
(22:56):
we think we can see clues of them now. It's
sort of like incredib able to imagine that you could
see today remnants of something that happened fourteen billion years ago, right,
that's sort of incredible. Most of the stuff that happened
a long time ago was gone, right, Like you can't
see most of the dinosaurs that were on Earth, just
a very few that happened to get fossilized. I think
part of it is that, you know, we were at
(23:18):
that time stuck on like visible light astronomy, right, We're
trying to look at the entire universe only through like
the visible lights spectrum. Yeah, at the same time, people
were just starting to figure out that there were other
ways to look at the universe. It was in the
thirties that radio astronomy was accidentally invented because somebody built
a big antenna to try to communicate across the Atlantic
(23:39):
and realized, oh my gosh, there are crazy radio signals
coming from space. What wise space making radio signals. And
that was the discovery, for example, of the big radio
source at the center of our galaxy, which turns out
to be from a black hole's accretion disk. And so
we had just begun to understand that radio astronomy was
a possible thing. You could do another way to look
(24:00):
at the universe. Right, everything in the university is glowing.
Everything that interacts electromagnetically gives off some kind of light,
and it just depends on the temperature. So you're not
very hot, so you don't glow in the visible light
the way like a white hot piece of metal does,
or the sun does. You and the Earth do, however,
glow in the infrared. And so if you're cold enough,
(24:22):
then you glow at longer and longer temperatures which are
not visible. So if you look at the night sky
or any sky really and look at it in the
frequency of radio waves, then you can see colder stuff,
stuff that doesn't glow in the visible things like gas
and dust and planets and other kinds of things. So
it's a different way of looking at the universe. A
different filter shows you different stuff, right, And it also
(24:42):
travels differently through space, right, which is why it's sort
of like clearer to see things in the radio spectrum.
Longer wavelengths are less obstructed by like small particles and stuff,
so radio can travel more easily through like big clouds
of gas and dust and this kind of stuff. So
let's you see through different things, because every odd is
transparent or opaque at different frequencies. Right. For example, your
(25:04):
walls are transparent in X ray, right, but opaque invisible light.
You can see through them with some kinds of light
X ray light with very high frequency, but you can't
see through them in other kinds of light, like visible light.
So that's kind of the picture that sets up the discovery.
So we knew there was this light out there where
we didn't think we could see it, and also we
(25:24):
were just discovering, you know, the radio spectrum of signals
out there in space. So then how did they finally
put the two together? So people put the two together
sort of accidentally at first, and it wasn't even realized
until decades and decades later, because it was World War
Two that really improved our radio technology. Obviously that was
important for signaling during the war, and so it gave
(25:45):
a great boost to like a lot of our electronics
and radar and radio technology. And so after World War Two,
people started playing around with radio a little bit more,
and there were folks that were like looking at the
sky and surveying it at various wavelengths. And for example,
a Frenchman named Emil LaRue in ninety five made a
measurement of radiation from the sky and he found this
(26:08):
source of radiation at just the right frequency, which we
now understand was the CMB. He just didn't understand what
it was, and nobody recognized it. I see. He just
hooked it up and he heard like a or something
through his earphones or something. Yeah. And people are looking
for sources right there, like pointing this telescope and various things,
trying to find things that generated radio waves, like the
(26:29):
center of the galaxy generated radio waves, the Sun generates
radio waves, Jupiter. You're looking for like objects. You're trying
to understand what's out there. But what they were seeing was,
in addition this noise that you hear from every direction, right,
it doesn't matter where you point at the center of
the galaxy, of the center the Solar system, doesn't matter where.
It's coming from every direction, and so that's sort of weird.
(26:50):
And people had sort of forgotten this prediction by the
theorists that there would be this like radio noise from
the early universe out there, and then they started to
hear it, and they didn't understand what it was. I see,
But I guess how did they know it wasn't just
noise like just general noisy equipment, you know, thermal fluctuations,
(27:11):
you know, noise in the air. How did they know
it was something special and not just like, hey, I
have bad equipment. Yeah, that's a great question. That took
a more detailed comparison between what was expected and what
was predicted and what was actually seen. But we'll get
there at a moment. To me, it's super fun to
look back into history and see evidence of future discoveries
(27:31):
in people's data, to see people who could have claimed
the discovery of something which later won the Nobel Prize,
they just didn't understand what they had and so this
actually happened twice for the CMB. In nine was a
meal LaRue and two years later a Russian guy named
Shamanov observed a signal at the same temperature in every
direction and didn't understand it, and they just sort of
(27:53):
like went and then moved on and never really figured
it out. Now, of course we know that was all
the data they needed to claim this every of the CMB,
they just didn't really have the context for it. Yeah,
I mean, like, is it directional this noise or is
it only coming from space? If I pointed back towards
the Earth, I don't hear it, you know. I guess
paint us a picture like if I'm in the sixties
(28:13):
and I haven't SENTTENNA, what would I be experiencing? Yeah,
so it comes from space, right. Earth actually is a
big source of radio noise, so not just electronics, but
like everything around us is constantly emitting light. Just like
we said earlier, it's glowing, and so you've got to
get rid of that by only pointing your antenna up
at the sky, so you're listening to radio from the
(28:35):
sky only. The interesting thing about this is that there
doesn't seem to be any particular source of it. It
doesn't seem like it's coming from the center of the galaxy,
doesn't seem like it's coming from Jupiter or from the
Sun or any particular source. Once you point your radio
telescope up at the sky and listen, you see it
equally from every direction, which is really weird. And it's
(28:55):
a clue that's not coming from any particular object out there.
It's just sort of like the cosmos are filled with
this bath. And of course you have to make sure
it's not instrumental, that it's not just like noise in
your electronics or something like that. And so you can
spend a lot of time trying to find that noise
and remove it and make sure you know that's not
(29:15):
from your electronics. But you can tell that it's not
from any particular object because it's coming from every direction
in the sky. It was definitely coming from somewhere, is
what you're saying. It was coming from space, right, It
was definitely not coming from Earth, all right, So then
what was the big breakthroughout it they piece it all together.
It was in the sixties when one group at Princeton
realized a whole lot of second we might be able
(29:37):
to see this radiation. They sort of like dug back
into these old calculations from the forties to think about
this light from their early universe and realize that with
the advance in radio technology, it might actually be possible.
And so this is like go back and read old
papers people, because there are great ideas out there that
people wrote down that they didn't follow up on because
(29:58):
the technology wasn't there. And so there was a guy
Princeton named Dickie who realized, you know what, we could
probably see this light. We think it's out there. It
would be evidence that the universe was wasn't hot and
dense enough to generate this light. And now we think
we might be able to see it. So let's go
build a radio telescope so we can go and look
for it. So this was Dickie at Princeton. I see.
(30:19):
It was somebody who said, like, hey, radio astronomy is
a thing. You could find interesting signals out there in
the radio spectrum, and oh, by the way, um you
should be able to see this early light, this dim
light from the universe beginning. Yeah, and it was a
great idea, you know, the technology had come around. The
question was interesting, I realized, Wow, I have the hammer
to bang in this nail. And actually, as a weird acide,
(30:43):
Dickie didn't believe in the Big Bang as the beginning
of the universe. He didn't think the universe had a beginning,
but he did think that the universe had an early,
really hot, dense state. He had this other idea. He
thought of the universe as a sort of a cycle.
He thought the universe expanded and then slow down and
crunched back together again, and he was trying to understand
(31:03):
if that crunch was sort of like intense enough to
break apart all of the matter. He wanted to find
this early radiation as like evidence of how matter was
destroyed rather than created. He thought this fireball destroyed the
previous universe and then hours was birthed out of that
what like a crunch from the Big Bang or before
the Big Bang, from before the Big Bang. He thought
(31:26):
that our universe was just like the latest and infinite
series of universes, and that before our big bang, there
was a big crunch, and that this sort of like
cleansed the universe from all the stuff from the previous universe,
you know, sort of like wipe the table and set
this for a new meal. He's thinking, maybe you can
hear the crunch or see like this crunching the current universe. Yeah,
(31:46):
and he thought that maybe this cosmic microwave background radiation,
if you could spot it, would be evidence for this
like cleansing radiation that basically destroyed the previous universe and
helped create ours I see. And what made them think
that radio would be a better way to see it
than other wavelengths. So they did this calculation. They thought
how hot was it back then? And it was about
three thousand degrees kelvin, And if that light was still around,
(32:10):
what would be its wavelength now? So it's a little confusing.
We talked about the temperature of light. What we really
mean when we say the temperature of light is we
mean the temperature of a thing which would generate light
at a certain frequency. So, for example, we say the
light was three thousand degrees kelvin, we really mean a
plasma that was three thousand degrees kelvin would glow a
(32:31):
certain frequency. Something that's colder, some that's three degrees kelvin,
for example, would glow at a much longer frequency. But
if you have a plasma for a long, long time ago,
and the glowing at three thousand degrees kelvin. It made
very high frequency light light that like zigs and zags
really quickly. As the universe expands, member space stretches, that
light gets too longer and longer frequencies. That light gets stretched.
(32:54):
Doesn't get slowed down. Light always moves to the same speed,
but the wavelengths gets stretched. So now that light is
much longer frequency, whereas we say colder temperature. And so
they did that calculation. They figured what the frequency of
the light should be, and they figured it should be
something corresponding to radiation from an object. They around three
or five or ten degrees kelvin. So they sort of
(33:16):
knew that if this light from the early universe glowed
at a certain frequency or a frequency range, it's not
like you can measure that glow in the X rays
or in the visible light, like it only glows in
that certain frequency. Yes, it would be characteristic at that temperature,
all right, And so they were poison to go look
for it basically and then realize what an amazing discovery
(33:38):
it was. So let's get into how they found it
and when they realized what they were sitting on. But first,
let's take another quick rate. All right, we're talking about
(33:58):
the cosmic microwave background and how it was discovered, and
it feels like people knew was there and this new technology,
this radio astronomy, was just coming into fashion, and so
people were ready to see it. People were ready to
see it, you know. But just like to recap the
crazy history, it was like predicted in the forties and
then ignored, accidentally discovered twice in the fifties and then ignored,
(34:23):
and then in the early sixties, Dickie at Princeton is like,
hold on a second, I bet we could see this.
Let's build a telescope to look for it. So he's
the first one to like really bring this idea together
and decide to look for this thing on purpose. But
he's not the one who actually found it. Oh really,
But did he build a telescope for it to look
for it? No, he got started and they were like
(34:43):
getting going and starting to build this thing. Meanwhile, at
the same time, totally coincidentally, sixty kilometers away from Princeton,
at Bell Labs, there was another couple of guys working
at a totally different project looking for something totally different.
They built a radio telescope because they were working from
Bell Labs and they were trying to communicate with balloons satellites.
(35:04):
Bell Labs was experimenting with like building a telecommunication networks
using floating balloons in the upper atmosphere. So they built
this thing to talk to balloons. So they had already
built one, but not to do astronomy. To do like communications,
you had to do communications. And so they had built
this thing and they were like trying to talk to balloons,
and then Bell Labs decided, you know what, we're not
(35:25):
interested in this. Let's cancel the whole project. We're not
interested in like balloons satellites as a way to build
the telecommunications network. But these guys Penzis and Wilson, the
ones working from Bell Labs, they had done radio astronomy
for their PhDs. They knew how to do that, and
they were like, all right, well we have this awesome telescope.
Why don't we point at the sky and see what
we see. We got some questions about you know, they
(35:48):
wanted to follow up from basically from their THESS and
do some more research. So they just sort of like
took advantage of this existing thing and started trying to
do some research. I see. So they were originally scientists
and they probably hoped they could use it for signs,
but they had this pesky engineering problem they had to
work on. But then when that got canceled, they could
do signs on it. Yeah, And so they had this instrument. Now,
(36:09):
Dickie was building one for himself over Princeton because he
knew what to look for. Penz S and Wilson they
already had it, but they didn't know what to look for.
They weren't looking for the cosmic marcrotwave background. They didn't
know what existed. It wasn't on their radar, so to speak,
at all. They were just trying to build a sensitive
instrument so they could listen to the sky. And you know,
they're great engineers, and they built this really awesome telescope.
(36:31):
If you look at pictures of it, it it looks kind
of funny. It doesn't look like a telescope you see
often because it's only part of a parabola. It looks
sort of like a big shovel, like a big scoop,
because it's only a little sliver of a parabola. Because
they wanted to be really careful and only pointed towards
the sky, so it's like really well shielded from the
ground and just gathers a bit of the radio waves
from the sky. Now did they set out to look
(36:53):
for this cosmic microwave background or were they, you know,
hoping to look at stars and black holes and things
like that. They were not looking for this at all.
They had no idea this thing existed as a concept,
and they had no idea that it was possible to
see it. One of them was interested in like finding
big clouds of hydrogen that were glowing, so they wanted
to look for other stuff. But they were really good
(37:13):
engineers and builders, and so they built this thing, and
they cooled it really really cold, because what you want
to do for your radio telescope is not absorbed signals
from like the telescope itself. Remember, everything glows, including your telescope.
So they had to cool the whole telescope down to
four point two degrees kelvin so they didn't like swamp
itself with its own radio signals. And then finally in
(37:35):
July nine, while Dickie is over there building his own telescope,
they turn it on and what they saw was a
lot more noise than they expected because they had done
such a good job of like cooling everything that they
expected to hear this clean signal. But really they saw
this like giant hiss in the radio wave spectrum. Yeah,
they saw this giant hiss, and they pointed their telescope
(37:57):
in different directions. It's on a big wheel, so you
could like turn it this way and that way in
the other way, and they just couldn't get rid of
this hiss. And they like took apart all their electronics
and replaced them. They like put another layer of shielding
on everything, They cooled everything down a little bit. All
this made like a very small amount of difference, reducing
the noise a very small amount. But they couldn't get
(38:17):
rid of this hiss. I see. They were trying to
get rid of the science signal, but they did because
they didn't know it as a science signal. Yeah, exactly.
They thought it was just noise that was going to
interfere with their science. And at one point they found
a bunch of pigeons that were nesting in their telescope,
and they had covered part of the electronics with pigeon poop,
or as they called it in their paper White Poultry
(38:38):
Dialectic Material, and they cleaned all that off, but it
didn't help anything, and so they were very disappointed. You know,
at the time, Wilson says, this was a huge disappointment
for us scientifically, And they spent like a year plunking
away at this thing, trying to get rid of this noise.
They had no idea what they were looking at. Well,
in a way, they were right, you know, like if
(38:58):
they were trying to get you know, radio waste, like
those from a cloud of hydrogen somewhere, this is sort
of noise that gets in the way, right, Like the
universe just has this noise. They just didn't know it
was a feature of the universe absolutely. You know, one
man's noise is another woman's signal as another woman's Nobel prize.
And we have that in particle physics. All the time
we were looking for the top cork, and now the
(39:19):
top cork is an obstacle in finding other particles. We
wish we could like turn it off and get it
out of the way so we could see other stuff.
And so yeah, it's very subjective, all right. So then
they thought they had some sort of error or some
sort of equipment failure for over a year, and then
how did they realize that this was something of interest?
So Pensis, one of the guys who built this telescope,
(39:40):
happened to run into one of his friends, Bernard Burkey,
on an airplane, who told him that Dicky over Princeton
was looking for this exact thing. So Pensis is like
complaining about how we have this his in our telescope.
Oh my gosh, we don't understand it. And he says,
you should talk to these guys at Princeton because I
think they know what you found. Oh wow, no kidding
on an airplane, on an airplane, just like by chance.
(40:01):
And I'm guessing this is, you know, the sixties, So
they were, you know, we're in ties, drinking cocktails, smoking. Yeah,
it sucking in the plane right over the loud propeller noises. Yeah.
So Pensy has calls up Dickie at Princeton and says,
I heard about this thing you're predicting. Dickie sends him
a paper written by his student John Peebles, predicting this
(40:22):
noise and explaining exactly what it should look like. And
Pensys is like, wow, this is exactly what we are
seeing in our telescope right now. They had no idea,
you know, what does it mean? What it looks like?
Should like it? Should it have a specific like signature
and when you look at the signal in the frequency spectrum,
or should it have this particular shape to it, or
what is that like? How would you recognize it? Yeah,
(40:43):
it looks like what we call black body radiation. So,
as we said earlier, everything in the universe that has
a temperature glows, and it glows at a specific frequency,
but not at only one frequency. It tends to peek
at a frequency and then have a particular shape. So
at one frequency you'll have the high it's intensity of radiation,
and then at the nearby frequencies it will sort of
fall off in a very characteristic pattern that we call
(41:06):
black body spectrum. And so what they saw was the
frequency of something at two point seven degrees kelvin glowing
with black body radiation. And so it wasn't just like
we saw a bunch of photons of this one number,
like they saw the whole shape. You know, it's like
if you saw a mountain of a very specific shape
and somebody predicted seeing a mountain of exactly that shape.
(41:27):
You'd be like, okay, you've understood how that mountain came
to be because black body radiation. I think it doesn't
just look like a bell curve, like a random noise curved.
It actually has kind of a shape twit, right, Yeah,
it has a shape. It's asymmetric around the peak, so
it's very characteristic. All right. So then Dicky's like, oh,
like I'm building the cells coope, but these guys already
have it and we've been scooped. Yeah, exactly. There's a
(41:49):
famous story where Dicky gets off the phone from talking
with Penzias and says, boys, we've been scooped. And that's
really kind of a bummer for Dicky because he's the
one who had this idea to look for it and
started building his telescope, like that was really the ingenuity,
and Penzias and Wilson just sort of like stumbled across it,
had no idea what they had found until Dicky told
them that's what you get for answering the phone, Daniel,
(42:11):
That's why I never answered my phone. It could be
somebody trying to scoop. So then they worked together. Everyone
was a very good science citizen at that point, and
Dickie like explained to them what they were looking for,
and they all agreed to publish together. So Dicky and
his crew published a paper saying, we predict that if
you looked in the sky this frequency, you could see
(42:33):
the afterglow of remnants from the Big Bang and it
would look just like this, and you can do it
and it'll be very interesting. And then in the same journal,
the next paper is Penzias and Wilson saying, by the way,
we've looked in the sky and we see this weird glow,
we think it might be explained by this previous paper
you just read by Dicky and his group. Interesting, it
was a two part series. It was a two part series.
(42:54):
And this is nice. You know when scientists who are
working on something and realize they're sort of in competition
or in working in parallel, they decided to publish together
rather than like have some crazy race to who gets
their paper in one minute before. Yeah, that's that's pretty cool.
So then, because I guess Dickie didn't have his telescope ready,
It's not like he could have just like jumped in
and found the signal. He just still ways away from
(43:16):
having a functioning telescope. Yeah, he had been scooped right,
and just by chance, if Penzias and Wilson had waited
another year or something, then Dickie could have had the
idea and the data. But he didn't, And Penzias and
Wilson went on to win the Nobel Prize in nineteen
seventy eight for this observation. Wow, and also people's gut
it to write peoples who originally had this idea and
(43:36):
wrote the paper. He won the Nobel Prize in two
thousand nineteen for like other contributions to cosmic microwave background theory.
But Dickie in the end never won the Nobel Prize.
I seem so back then it went to the people
who have discovered it, not the people who predicted that
it would be there. Yeah, because if you look back
in history, it turns out that other people had already
predicted it, right. People in the forties had the idea
(43:59):
that this would be there, And there was this other
Russian group which in the early sixties had also published
a paper saying, by the way we might be able
to see this, people should go look for it. So
that was an idea which was sort of old hand
bubbling up around the world at the same time, and
maybe by a lot of those people who had died
or something. Right that you couldn't give him the Nobel
Prize for it, that's true. You can't give the Nobel
(44:20):
Prize to somebody if they've already died. Yeah, alright, Well,
so that's how we humans discovered the cosmic microwave background.
And it's something that's pretty significant, right. It tells us
a lot about the conditions for the early universe, about
the composition of the universe. It confirms things like dark matter,
dark energy. I mean, there's a lot in that signal. Yeah.
Hawking says it's the greatest discovery of the century, if
(44:43):
not of all time. And the reason is that it
is really very, very rich, like how the cosmic microwave
background looks, and specifically how it's not exactly smooth but
has these little ripples in. It tells us a lot
about how that early universe plasma was rating what it
was doing, and like ripples in that plasma are sensitive
to things like is the dark matter fraction of the
(45:06):
universe or five, because it changes how that matters, sort
of slashes back and forth if the dark matter is
interacting or not. So, as you say, we can fit
a lot of the parameters of the universe. A lot
of the questions about what the universe is made out
of and how it came to be come from understanding
that in great detail. And you know, years later people
launched a satellite to measure the cosmic microwave background radiation
(45:28):
very precisely. That was called the Kobe satellite, and then
that one a Nobel prize. So it's like a very
rich area of research. Right. There's not just a lot
of information in it, but it also kind of basically
confirms our theories about the early universe, right, Like it
it's like perfect evidence for all these series about the
Big Bang and inflation and the you know what was
(45:49):
happening in ing in those early few seconds. Yeah, it
definitely confirms the Big Bang, right It tells us that
the steady state theory just doesn't work because the universe
was once much more dense and hot and crazy, so
rules out the steady state theory and confirms the Big Bang.
It doesn't exactly confirm inflation precisely. There are some predictions
for like weird little wiggles in the CNB, we might
(46:11):
be able to see that would confirm inflation. And several
years ago there was an experiment called BICEP two that
thought they had seen that, but it turns out they
were wrong. But in the future, there's a lot more
we can learn about the universe. Whether inflation was right,
is it the right theory of what caused the Big
Bang in the very very early universe, We still don't know,
But we hope that there's more layers of information in
the CNB that will one day reveal even more about
(46:33):
the early universe and how it all came to be. Yeah,
there might still be more noble prices in there. Yeah,
there might be information in that data right now which
you could download onto your laptop and if you knew
how to interpret, could win you a Nobel prize. Sometimes
everything you need is right in front of you, or
I guess the dangerous you could download it, have it
on your computer and then not discover something, and then
(46:55):
in the future of some physicists and a podcast saying,
see that person had that data in his or her
laptop and didn't see so better to just just not downloaded
or just don't you never hear about how you were scooped,
you'll have an easier life, all right. Well, that is
how we discover one of the greatest discoveries a few
(47:15):
in history apparently, although I would argue that, you know,
that bowl of oat meal I had this morning was
pretty good discovering as well. I think brown sugar and
oatmeal that was a pretty big discovery. No thanks, no thanks, huh,
that's a level too far. Alright, that's for the future.
All right. Well, we hope to enjoy that story. Thanks
for joining us, See you next time. Thanks for listening,
(47:44):
and remember that Daniel and Jorge Explain the Universe is
a production of I Heart Radio or more podcast for
my heart Radio, visit the I heart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows. No
Hey, Daniel, do you know what I don't understand about
winning a Physics Nobel Prize? Oh yeah, what's that? Well,
you know, to be honest, some of them seem kind
of easy in hindsight, be easy to win a Nobel Prize. Yeah,
I mean, like for Einstein, all he had to do
is analyze someone else's experiment. It was just one idea
that he had one day and boom, Nobel Prize. I
guess that's easy if you're Einstein. Well, I mean also,
(00:31):
like the discovery of X rays was totally by accident
and it took about one day of work for them.
That's true if you happen to have X rays around,
or like the Higgs boson. You know, like college physics
major can do that kind of math. All right, you win.
I admitted getting a Physics Nobel Prize is easy, So
then why don't we have one? Because we haven't tried.
(00:52):
It's win one today, Daniel. Alright, great idea, Einstein, let's
do it. Hi. I am more hammy cartoonists and the
creator of PhD comics. Hi. I'm Daniel. I'm a particle
(01:15):
physicist and I have not yet won a Nobel Prize.
But maybe any day someday will be the day. Do
you wake up every day thinking, maybe today's to day
I'll have my great idea. I don't expect it to
ever happen, but I do love those stories when somebody
has a moment of insight or stumbles across something weird,
and that morning when they woke up and had their
oatmeal or whatever, they had no idea that it would
(01:37):
be that fateful day. Maybe that's the key. It's the oatmeal.
And maybe it's a special kind of oatmeal. Daniel like
a radioactive oatmeal. Bitten by his radioactive oatmeal, he gained
his proportional intelligence. There you go. Maybe that was a
nice secret. I think when people say you're as smart
as a bowl of oatmeal, they don't mean it as
a compliment. Well, I think that's very disparaging of oatmeal,
(01:58):
because you never know, there could be sentient genius oatmeal
out there in space. They could be our next alien overlords.
Yet another sci fi pitch for Netflix put it on
the list. All right, Well, welcome to our podcast Daniel
and Jorge Explain the Universe, a production of I Heart
Radio in which we try not to turn your brain
into oatmeal as we talk about all the amazing things
(02:19):
that are out there in our universe, all the things
that we have painstakingly uncovered in our search to reveal
the fundamental nature of matter and radiation and everything in
the universe, and all the things that science is still
picking at, all the big questions that are out there,
all the discoveries that might be far into the future
or just around the corner. That's right. The universe is
(02:42):
full of mysteries, full of big questions and wonderful discoveries
just waiting for us to find them and possibly get
a Nobel price for finding them in the congratulatory bowl
of oatmeal. And sometimes the answer to those questions is
already out there. It's beaming down at us from the cosmos,
or it's in somebody's data. They just don't even recognize it.
(03:04):
And sometimes those Nobel prizes come just from putting one
thing next to the other, from finding that the answer
to a question is already out there. Yeah, because technically
all of the secrets of the universe, all of the
great big truth about it, are out there for us
to discover. I mean, it's not like they don't exist.
They're there, which is haven't seen them or having discovered
them or having known where to look. Yeah, you know,
(03:27):
that's a really fun question, Like is it actually possible
to unravel the nature of the universe without ever leaving
the Earth? Just by watching this guy's It's sort of
incredible what we have been able to figure out about
like far flung corners of the universe, the way galaxies
expand and collide and do all sorts of crazy stuff
without ever having left the Earth. But I wonder if
(03:48):
it's possible to actually figure out like all of it,
to get all the way down to string theory and
quantum gravity without ever going anywhere else. It would be
pretty cool if all that information was beaming down on
us right now. Are you saying, like, are we maybe
in the wrong place, Like if we were somewhere else,
we could see the secrets of the universe, you know,
Or maybe they're all in one box but in another
(04:10):
part of the galaxy. Yeah. Or it might be that
you need to do some kind of experiment like smash
black holes together at very high speeds in order to
get the answer to some question. Or might be that
you need to be able to look inside a black hole,
which we can do from here. Maybe you need to
be nearby it in order to decrypt the quantum information
in the Hawking radiation. It might not be possible to
(04:30):
gather all that information from Earth. Or maybe it is.
Maybe if somebody was smart enough, they could figure out
all the secrets of the universe and just from the
data we are getting today. Yeah, hopefully not by getting
us near a black hole or by smashing a couple
of black holes together here on Earth. That's hounds kind
of dangerous. Anything in the name of science not worth
a noble prize. Well, you know, everybody makes their own
(04:51):
judgment call on that. Please, physicists, check with the rest
of us before you make those kinds of judgment calls.
I know this is important for you, all of you,
but you know, we might I'd have other priorities, your
priorities to get to name the black hole machine, right,
I want to be alive to me and to call
it that, you know. But yeah, the history of physics
and science here on Earth has a long and interesting history,
(05:13):
full of amazing discoveries. And some of them happened kind
of by accident, right, Oh, lots of them happened by accident.
People stumble across stuff they didn't even know to look for,
see things they don't understand, and only later realize that
they contain secrets of the universe. So today we'll be
covering one such story of an amazing discovery that really
kind of illuminated in a very real way the beginning
(05:36):
of the universe. Absolutely, it's some of the oldest light
in the universe, and it tells us a lot about
how the universe began and how hot and dense and
crazy it was billions and billions of years ago, and
it was almost overlooked and mistaken for pigeon poop. Wow,
that is a big oops there for the physicist. So
(05:56):
today on the program, we'll be talking about how was
the cosmic microwave background discovered? Now, Daniel, this is the
famous CNB, right, this is the famous CNB that has
taught us so much about the nature of the universe.
It's not the CNB R as they call it in
(06:17):
the Marvel universe. You have a problem with that, Well,
the scientists in the Marvel universe can call their CNB
whatever they like, but out here in the real universe,
we tend to call it the CMB. Just the cosmic
microwave background, meaning like it's the background basically of the universe.
It's everywhere, It's all around us. Photons from the early
universe plasma are zooming all over the universe in every direction,
(06:39):
no matter where you look. That's what we mean by background.
It's sort of just like always, there's everywhere. Yeah, And
it has a long and interesting history of people thinking
it was there but not seeing it, or seeing it
and not thinking it was there. It's kind of an
interesting and dramatic plotline, right absolutely. And it's the kind
of thing that could have been discovered very easily decade
(07:00):
before it was, and in fact, it was discovered several
times without even being understood, and so it's sort of
like a story of missed opportunities and the folks who
ended up winning the Nobel Prize for finding it could
very easily not have So it sounds like a pretty
intriguing story. So we'll dig into that and go over
every detail. But at first we were curious about how
(07:21):
many people know how this amazing discovery was found. So,
as usual, Daniel went out there into the wilds of
the Internet and asked people if they knew how the
cosmic microwave background was discovered. And so if you would
like to be interrogated about physics by a physicist without
the opportunity to consult any reference materials that sounds fun
to you, then please email me two questions at Daniel
(07:43):
and Jorge dot com. Here's what people had to say.
I think it was around the seventies. Whenever it was,
they feel was a very powerful telescope maybe radio telescope
to look at something else, and then they heard or thought, so,
I'm like what they thought was noise from a local source.
They even thought it was the pigeons that were nesting
in the telescope and actually had a big job clearing
(08:04):
that out, trying to get rid of it, but no
matter what they did, couldn't get rid of it. And
that but obviously eventually they realized it wasn't local at all,
but from fort almost fourteen billion light years away. The
NBA two words Hubble telescope. Okay, that's a tool, not
an answer. Aliens told us about it, and they also
told us where to look. So we pointed the Hubble
(08:24):
telescope at the cosmic magawave background radiation and that's how
we discovered it. I haven't really heard about it, just
as an assumption, maybe e when we were trying to
respond some kind of radiations. I think the background radiation
was discovered by accident. Hadn't had nothing to do with
someone using their microwave up and to make eggs. But
(08:47):
I think it was World War Two. Weren't they doing
radar experiments and they discovered this noise? But I think
it was by accident. The cosmic microwave background was discovered
by two scientists working at Bell Labs in New Jersey
who were investigating a strange buzz they picked up when
actually working on something else. I think it was discovered
(09:08):
around nineteen sixties as one of the first discoveries of
radio astronomy. After making sure it wasn't the error in
data or in measurements, there was a lot of theorizing
what did what it means and why the signal was
actually hurt quite possibly with a radio telescope. Maybe astronomers
or scientists were looking at like certain stars or something
(09:30):
they're like, hey, these guys are given off a lot
of radiation, and then they looked at the stars and
they're like, oh, it's not the stars. Put something around it.
But there's nothing around it, so they're like, oh, what
if we just focused on the space around it? And
then they focused on the space. All right, A lot
of versions of the story here from the public. A
lot of people seem to know something about how it
(09:51):
was discovered by accident. Yeah, including apparently aliens told us
about it. I like, how this president, you said two
words hubble telescope bam drops to my and aliens. Oh,
by the way, also aliens, well, how else do you
know where the point your hubble telescope? Right? The aliens
have to tell you it makes perfect sense. It's pretty
surprising how many people hadn't heard about this. And also
(10:12):
I knew a little bit about it. You know, generally
people seem to know that it wasn't like this intentional thing,
like there was some element of accident to it. That's
exactly right. And it took a long time for people
to even know that it should be there and know
that we might be able to see it. So there's
sort of like progress and back steps and forward steps
on the theoretical side as well as on the actual
(10:34):
like observational side. All right, well, let's get into this
story then, and maybe take us back Daniel, because I
imagine this story starts in the early nineteen hundreds, and
you know, we were sort of just starting to discover
how big the universe was and that it maybe came
from a big bang. You know, what were we thinking
at the time, and what did we know? Because you know,
(10:54):
I imagine that the idea that there's some background noise
in the universe is not that surprise think to think about,
but it having some special meaning maybe is Yeah, so
that we have to go back to basically Hubble. Hubble
is the one who figured out that the universe was expanding.
Before that, people thought that everything was just sort of
like hanging out in space. Things hadn't changed in hundreds
(11:16):
or thousands or billions of years. But Hubble discovered that
there were other galaxies out there and that they were
moving away from us faster and faster, and suddenly that
made the universe dynamic instead of static, like things were
definitely changing. And people had two totally different concepts of
ways to explain what Hubble saw that the universe was expanding.
(11:36):
One is the idea that's very familiar to us that
if the universe is expanding, then you run the clock
backwards in time, then it must have been more dense,
must have been more compact, must have been more squeezed
together in the beginning, and you can sort of track
it back to a very early moment when you reach
like infinite density, the singularity. So this is the big
bang idea that the universe came from some like huge
(11:58):
early expansion, and what we're now is the remnants of that,
the continued expansion of the universe. So that was one idea,
this big bang idea, right, because we we saw the
stars and the galaxies right now, they're all moving away
from us. So you know, the ideas that if you
rewind then at some point everything was crunched together. Yeah,
but some people didn't like that idea. They thought that's
(12:19):
ridiculous for the universe to have a beginning and for
it to begin in some sort of big bang. And
in fact, the name big bang came about as a
sort of like an insult, and they were like trying to,
you know, make that idea sounds silly by calling it
a big bang, and instead they preferred a steady state
theory of the universe. That's sort of hard to have
a steady state idea of the universe, that the universe
(12:40):
like isn't changing on the largest scale. When you see
that it's expanding, you know, how could that possibly be
If things are expanding, don't they get less and less dense. Well,
their idea was that there was some like source of
new stuff in the universe, that stuff was constantly being created,
and that was like refilling the universe. So the universe
was expanding but at a constant density because there was
(13:01):
some like thing that was like topping it off all
the time. That is sort of what we think of now,
but back then it seems sort of counter to the evidence. Well,
that's interesting that you say that you're right that we
know that the universe is expanding and that there is
more space being created, but the universe is getting more
and more dilute. The steady state theory involved like the
creation of more stars and galaxies and more stuff in
(13:24):
the universe to keep like the density constant. So the
steady state theory was like, well, let's figure out how
to make the universe so it's not getting more and
more dilute, that it's always been this way and live forever.
They were thinking, like, the density of the universe doesn't
change it's somehow expanding, but the density is not changing. Yeah,
because somebody's like pouring more syrup onto these pancakes all
(13:45):
the time, and so even though it's dribbling off the edges,
you're keeping the same amount of syrupe on top of
your pancakes. That's my big pancake theory of the universe.
I think you messed up that analogy. I think it's
it's more like the pancakes getting bigger, and so somebody
must be for more sarapes. There you go, all right there,
all right, right, that's a more delicious, very breakfast theme
(14:05):
physics analogy today. The oatmeal pancakes. It's the most important
physics meal the day. Wait till you hear about my
waffle based observation ideas, and might have to be another episode, Daniel,
I'm stuffed already. And so these were some of the
ideas people were bouncing around, like what does the expansion
of the universe mean? Did it come from some early, hot,
dense point or is there someplace where the universe is
(14:27):
creating new stuff so that things don't get less and
less dense as time goes on. I guess why were
they fighting this idea of a more you know, kind
of empty universe, like why couldn't the universe beginning more
and more dilute. I think they didn't like the idea
of a beginning. It seems sort of counterintuitive. They prefer
the concept It seemed more natural to them to imagine
the universe had always been here, because if there's a beginning, then,
(14:50):
as you know, there are big questions about that beginning,
what came before and what caused it? Why do we
have a beginning? You can avoid some of those things
if you imagine the universe is just always been this way.
Like if you don't accept that the universe could have
a beginning, then you have to make something up, like
where is all this syrup coming from? Yeah, there are
always more questions, but you know, it was sort of
an aesthetic preference, and so you had physicists on both
(15:12):
sides of the issue, some arguing that the universe must
have started with a big bang and others suggesting that,
you know, stuff was constantly being made in this steady state,
and so that's what people were thinking about. They were like,
where does the stuff in the universe come from? And
they were trying to understand for example, where heavy stuff
in the universe came from, Like, where does all the iron,
where does all the nickel and all that stuff in
(15:33):
the universe come from? Was it made during the Big Bang?
Or is it somehow made somewhere else and being like
poured into the universe somehow? I see, because it could
have been made in the Big Bang, right, like the
heavier elements could have been forged in that hot, tense
initial moments. That's what people thought in the early part
of the century that maybe in that incredible heat from
the Big Bang, you could have made iron, and you
(15:55):
could have made silicon and oxygen, and maybe all the
elements were fused in that initial time period. So people
spent a lot of time doing theoretical calculations of how
hot it was back then in the very early universe,
What was the temperature, what was the density? Were there
the conditions needed to make all of the heavy elements.
So that was the reason they started doing these calculations,
and they realized, Wow, in the very early universe, there
(16:18):
must have been this very very hot plasma, and that
plasma must have glowed the way plasma from the Sun,
for example, glows, And then the universe cooled, and at
some point that plasma becomes transparent because all of the
ions and it capture electrons as they cool and they
become neutral, and then it's transparent. So what they were
wondering about was all that energy, all that light that
was now flying around the universe. Was there enough light
(16:40):
there to like make the heavy elements? And they did
a bunch of calculations and they decided, no, it wasn't possible.
And now, of course we know that those heavy elements
were not made during the Big Bang. The Big Bang
mostly made hydrogen and helium and very tiny amounts of
heavier things. The heavier elements were made later in stars,
but they didn't know that at the time until they
did these calculations. But how did they know that? You
(17:02):
couldn't have made the heavier elements because there just aren't
the conditions, Like you can't make iron, for example, under
the conditions just after the Big Bang, like it needs
to be hotter and denser. You need the conditions inside stars.
But wasn't the Big Bang infinitely dance and super duper hot.
It was, but not for very long, you know, And
so like it took time for the basic particles to form.
(17:23):
You needed like quarks to shake out of it, and
then those quirks to get bound into protons, and then
those protons to find electrons and that's basically all that happened,
and then things cooled down. There was very very quick
early expansion. Remember the Big Bang itself is an expansion
that lasts like ten of the minus thirty seconds. I see.
There wasn't enough time to make the heavier elements, is
what you're saying. But just enough time to only make
(17:45):
hydrogen and helium, just enough to time to make hydrogen
and helium exactly and little trace elements of what comes next.
And so the other elements were later made in stars.
And this is where cosmologists kind of lost interest. They
were like, all right, so there must have been this
hot play and it must have generated a bunch of light,
but we're not interested anymore because that couldn't have made
the heavy elements. That was the question they were asking.
(18:08):
So they had the idea that there might be this
light from the early universe flying around, but they didn't
care because it didn't answer the question they were asking
At the time. They were more interested in, like had
the planets come about and had its stars and galaxies,
like the stuff that you can actually kind of that
is interesting to them, at least at the time in
the universe. Yeah, so it's very much motivated by like
(18:30):
what questions scientists are asking. Sometimes you stumble across an
idea and you don't realize, oh, this could actually be
really interesting and important for a totally different question. They
were focused on, you know, how do you make these
heavy elements? And on top of that, nobody imagined that
you could even see this light. Even if they thought,
well that light is cool and if you could see it,
it would prove that there was this hot, dense state
(18:51):
in the early universe. They didn't imagine to be possible
to see it today, and so they just sort of
like wrote it off and cosmologists sort of like moved on.
This is acculation is done in the forties by some
guys named Alpha and Herman and George Gammao, and they
did it, and people thought, well, I guess you can't
make heavy elements in the Big Bang, and then they
just sort of turned to other stuff. They thought the
Big Band was too boring. They're like, you know, like
(19:14):
all right, yeah, that's where the universe came from. It
was a big flash, but nothing interesting happened, nothing interesting
that we could see today. These photons, they started out
really hot, you know, like thousands of degrees kelvin, but
then they got cooled down as the universe expanded. They
got stretched out as the universe expands down to very
very cold temperatures, which means long wavelength, which means radio waves.
(19:37):
And so at the time, radio astronomy was like really
a brand new field that had just begun a few
years earlier. So nobody imagined you could actually detect these
faint signals. Nobody even bothered to propose that somebody do that.
All right, well let's get into a little bit more
detail about what they were expecting to see and then
how it was accidentally discovered. But first let's take a
(19:59):
quick break. Alright, we're talking about the cosmic microwave background
and how it was discovered. Now, Daniel, some of our
listeners might not know exactly what the cosmic microwave background
(20:21):
is or where it comes from. You want to go
as a quick recap of what it is and what
exactly it is that we're seeing when we look at it. So,
the cosmic backgrounwave background are photons from about three hundred
eighty thousand years after the Big Bang. Right, big Bang happens,
things are really hot and dense and stuck together, and
the universe expands, which means everything is getting more dilute
and more cool. And by about almost four hundred thousand years,
(20:44):
the universe had cool to the point where atoms could form,
like electrons were slow enough that they can now be
captured by protons and turned into hydrogen, for example. And
that means that the universe became transparent. So there's this
moment when the universe goes from like really hot and
glowy but opaque too, slightly less hot and slightly less
glowy and transparent. Right, it becomes like glass all of
(21:07):
a sudden. So what happens to those photons that were
made just before the universe became transparent, Well, they were
flying around and they're still flying around, and fourteen billion
years later, most of them are still flying around. And
so they were everywhere because the Big Bang was everywhere,
and this plasma filled the entire universe and filled it
with these photons. So that means that everywhere, all around
(21:30):
us are these photons not from the Big Bang, itself,
but from this hot plasma that existed about four hundred
thousand years after the Big Bang. Yeah, I'm thinking like,
it's like you're in the middle of a giant fire
and then suddenly the fire, everything are all around you
becomes transparent, and so you sort of get that one
last you know, flash of light from that fire right
(21:52):
before the universe became kind of solid. And because it
happened everywhere all at once, then there are always photons
wherever you look. Right, we look out and we see
this just in the night sky. Right, if you point
to a radio telescope to the night sky in any direction,
you see this because there's always a place where fourteen
billion years ago, almost a photon was created and it
(22:14):
has been flying towards us ever since. And as time
goes on, we're seeing these photons from further and further
slices of that early plasma. So we're always seeing it.
We always will see it. And so you were saying
that in the beginning of the Nine DS and through
the middle of it, we sort of knew this story.
We knew that's what had happened or possibly happened at
(22:34):
the Big Bang, and what happened to all those all
that light. But you're saying, nobody really cared about seeing
this light. Nobody imagined that you could write. Nobody thought, wow,
you could actually go and detect this stuff. It seemed
like it would be a really faint signal and you
need really impressive technology. And so people just sort of like, well,
I guess that existed, just like lots of other things
probably existed in early states of the universe. Doesn't mean
(22:56):
we think we can see clues of them now. It's
sort of like incredib able to imagine that you could
see today remnants of something that happened fourteen billion years ago, right,
that's sort of incredible. Most of the stuff that happened
a long time ago was gone, right, Like you can't
see most of the dinosaurs that were on Earth, just
a very few that happened to get fossilized. I think
part of it is that, you know, we were at
(23:18):
that time stuck on like visible light astronomy, right, We're
trying to look at the entire universe only through like
the visible lights spectrum. Yeah, at the same time, people
were just starting to figure out that there were other
ways to look at the universe. It was in the
thirties that radio astronomy was accidentally invented because somebody built
a big antenna to try to communicate across the Atlantic
(23:39):
and realized, oh my gosh, there are crazy radio signals
coming from space. What wise space making radio signals. And
that was the discovery, for example, of the big radio
source at the center of our galaxy, which turns out
to be from a black hole's accretion disk. And so
we had just begun to understand that radio astronomy was
a possible thing. You could do another way to look
(24:00):
at the universe. Right, everything in the university is glowing.
Everything that interacts electromagnetically gives off some kind of light,
and it just depends on the temperature. So you're not
very hot, so you don't glow in the visible light
the way like a white hot piece of metal does,
or the sun does. You and the Earth do, however,
glow in the infrared. And so if you're cold enough,
(24:22):
then you glow at longer and longer temperatures which are
not visible. So if you look at the night sky
or any sky really and look at it in the
frequency of radio waves, then you can see colder stuff,
stuff that doesn't glow in the visible things like gas
and dust and planets and other kinds of things. So
it's a different way of looking at the universe. A
different filter shows you different stuff, right, And it also
(24:42):
travels differently through space, right, which is why it's sort
of like clearer to see things in the radio spectrum.
Longer wavelengths are less obstructed by like small particles and stuff,
so radio can travel more easily through like big clouds
of gas and dust and this kind of stuff. So
let's you see through different things, because every odd is
transparent or opaque at different frequencies. Right. For example, your
(25:04):
walls are transparent in X ray, right, but opaque invisible light.
You can see through them with some kinds of light
X ray light with very high frequency, but you can't
see through them in other kinds of light, like visible light.
So that's kind of the picture that sets up the discovery.
So we knew there was this light out there where
we didn't think we could see it, and also we
(25:24):
were just discovering, you know, the radio spectrum of signals
out there in space. So then how did they finally
put the two together? So people put the two together
sort of accidentally at first, and it wasn't even realized
until decades and decades later, because it was World War
Two that really improved our radio technology. Obviously that was
important for signaling during the war, and so it gave
(25:45):
a great boost to like a lot of our electronics
and radar and radio technology. And so after World War Two,
people started playing around with radio a little bit more,
and there were folks that were like looking at the
sky and surveying it at various wavelengths. And for example,
a Frenchman named Emil LaRue in ninety five made a
measurement of radiation from the sky and he found this
(26:08):
source of radiation at just the right frequency, which we
now understand was the CMB. He just didn't understand what
it was, and nobody recognized it. I see. He just
hooked it up and he heard like a or something
through his earphones or something. Yeah. And people are looking
for sources right there, like pointing this telescope and various things,
trying to find things that generated radio waves, like the
(26:29):
center of the galaxy generated radio waves, the Sun generates
radio waves, Jupiter. You're looking for like objects. You're trying
to understand what's out there. But what they were seeing was,
in addition this noise that you hear from every direction, right,
it doesn't matter where you point at the center of
the galaxy, of the center the Solar system, doesn't matter where.
It's coming from every direction, and so that's sort of weird.
(26:50):
And people had sort of forgotten this prediction by the
theorists that there would be this like radio noise from
the early universe out there, and then they started to
hear it, and they didn't understand what it was. I see,
But I guess how did they know it wasn't just
noise like just general noisy equipment, you know, thermal fluctuations,
(27:11):
you know, noise in the air. How did they know
it was something special and not just like, hey, I
have bad equipment. Yeah, that's a great question. That took
a more detailed comparison between what was expected and what
was predicted and what was actually seen. But we'll get
there at a moment. To me, it's super fun to
look back into history and see evidence of future discoveries
(27:31):
in people's data, to see people who could have claimed
the discovery of something which later won the Nobel Prize,
they just didn't understand what they had and so this
actually happened twice for the CMB. In nine was a
meal LaRue and two years later a Russian guy named
Shamanov observed a signal at the same temperature in every
direction and didn't understand it, and they just sort of
(27:53):
like went and then moved on and never really figured
it out. Now, of course we know that was all
the data they needed to claim this every of the CMB,
they just didn't really have the context for it. Yeah,
I mean, like, is it directional this noise or is
it only coming from space? If I pointed back towards
the Earth, I don't hear it, you know. I guess
paint us a picture like if I'm in the sixties
(28:13):
and I haven't SENTTENNA, what would I be experiencing? Yeah,
so it comes from space, right. Earth actually is a
big source of radio noise, so not just electronics, but
like everything around us is constantly emitting light. Just like
we said earlier, it's glowing, and so you've got to
get rid of that by only pointing your antenna up
at the sky, so you're listening to radio from the
(28:35):
sky only. The interesting thing about this is that there
doesn't seem to be any particular source of it. It
doesn't seem like it's coming from the center of the galaxy,
doesn't seem like it's coming from Jupiter or from the
Sun or any particular source. Once you point your radio
telescope up at the sky and listen, you see it
equally from every direction, which is really weird. And it's
(28:55):
a clue that's not coming from any particular object out there.
It's just sort of like the cosmos are filled with
this bath. And of course you have to make sure
it's not instrumental, that it's not just like noise in
your electronics or something like that. And so you can
spend a lot of time trying to find that noise
and remove it and make sure you know that's not
(29:15):
from your electronics. But you can tell that it's not
from any particular object because it's coming from every direction
in the sky. It was definitely coming from somewhere, is
what you're saying. It was coming from space, right, It
was definitely not coming from Earth, all right, So then
what was the big breakthroughout it they piece it all together.
It was in the sixties when one group at Princeton
realized a whole lot of second we might be able
(29:37):
to see this radiation. They sort of like dug back
into these old calculations from the forties to think about
this light from their early universe and realize that with
the advance in radio technology, it might actually be possible.
And so this is like go back and read old
papers people, because there are great ideas out there that
people wrote down that they didn't follow up on because
(29:58):
the technology wasn't there. And so there was a guy
Princeton named Dickie who realized, you know what, we could
probably see this light. We think it's out there. It
would be evidence that the universe was wasn't hot and
dense enough to generate this light. And now we think
we might be able to see it. So let's go
build a radio telescope so we can go and look
for it. So this was Dickie at Princeton. I see.
(30:19):
It was somebody who said, like, hey, radio astronomy is
a thing. You could find interesting signals out there in
the radio spectrum, and oh, by the way, um you
should be able to see this early light, this dim
light from the universe beginning. Yeah, and it was a
great idea, you know, the technology had come around. The
question was interesting, I realized, Wow, I have the hammer
to bang in this nail. And actually, as a weird acide,
(30:43):
Dickie didn't believe in the Big Bang as the beginning
of the universe. He didn't think the universe had a beginning,
but he did think that the universe had an early,
really hot, dense state. He had this other idea. He
thought of the universe as a sort of a cycle.
He thought the universe expanded and then slow down and
crunched back together again, and he was trying to understand
(31:03):
if that crunch was sort of like intense enough to
break apart all of the matter. He wanted to find
this early radiation as like evidence of how matter was
destroyed rather than created. He thought this fireball destroyed the
previous universe and then hours was birthed out of that
what like a crunch from the Big Bang or before
the Big Bang, from before the Big Bang. He thought
(31:26):
that our universe was just like the latest and infinite
series of universes, and that before our big bang, there
was a big crunch, and that this sort of like
cleansed the universe from all the stuff from the previous universe,
you know, sort of like wipe the table and set
this for a new meal. He's thinking, maybe you can
hear the crunch or see like this crunching the current universe. Yeah,
(31:46):
and he thought that maybe this cosmic microwave background radiation,
if you could spot it, would be evidence for this
like cleansing radiation that basically destroyed the previous universe and
helped create ours I see. And what made them think
that radio would be a better way to see it
than other wavelengths. So they did this calculation. They thought
how hot was it back then? And it was about
three thousand degrees kelvin, And if that light was still around,
(32:10):
what would be its wavelength now? So it's a little confusing.
We talked about the temperature of light. What we really
mean when we say the temperature of light is we
mean the temperature of a thing which would generate light
at a certain frequency. So, for example, we say the
light was three thousand degrees kelvin, we really mean a
plasma that was three thousand degrees kelvin would glow a
(32:31):
certain frequency. Something that's colder, some that's three degrees kelvin,
for example, would glow at a much longer frequency. But
if you have a plasma for a long, long time ago,
and the glowing at three thousand degrees kelvin. It made
very high frequency light light that like zigs and zags
really quickly. As the universe expands, member space stretches, that
light gets too longer and longer frequencies. That light gets stretched.
(32:54):
Doesn't get slowed down. Light always moves to the same speed,
but the wavelengths gets stretched. So now that light is
much longer frequency, whereas we say colder temperature. And so
they did that calculation. They figured what the frequency of
the light should be, and they figured it should be
something corresponding to radiation from an object. They around three
or five or ten degrees kelvin. So they sort of
(33:16):
knew that if this light from the early universe glowed
at a certain frequency or a frequency range, it's not
like you can measure that glow in the X rays
or in the visible light, like it only glows in
that certain frequency. Yes, it would be characteristic at that temperature,
all right, And so they were poison to go look
for it basically and then realize what an amazing discovery
(33:38):
it was. So let's get into how they found it
and when they realized what they were sitting on. But first,
let's take another quick rate. All right, we're talking about
(33:58):
the cosmic microwave background and how it was discovered, and
it feels like people knew was there and this new technology,
this radio astronomy, was just coming into fashion, and so
people were ready to see it. People were ready to
see it, you know. But just like to recap the
crazy history, it was like predicted in the forties and
then ignored, accidentally discovered twice in the fifties and then ignored,
(34:23):
and then in the early sixties, Dickie at Princeton is like,
hold on a second, I bet we could see this.
Let's build a telescope to look for it. So he's
the first one to like really bring this idea together
and decide to look for this thing on purpose. But
he's not the one who actually found it. Oh really,
But did he build a telescope for it to look
for it? No, he got started and they were like
(34:43):
getting going and starting to build this thing. Meanwhile, at
the same time, totally coincidentally, sixty kilometers away from Princeton,
at Bell Labs, there was another couple of guys working
at a totally different project looking for something totally different.
They built a radio telescope because they were working from
Bell Labs and they were trying to communicate with balloons satellites.
(35:04):
Bell Labs was experimenting with like building a telecommunication networks
using floating balloons in the upper atmosphere. So they built
this thing to talk to balloons. So they had already
built one, but not to do astronomy. To do like communications,
you had to do communications. And so they had built
this thing and they were like trying to talk to balloons,
and then Bell Labs decided, you know what, we're not
(35:25):
interested in this. Let's cancel the whole project. We're not
interested in like balloons satellites as a way to build
the telecommunications network. But these guys Penzis and Wilson, the
ones working from Bell Labs, they had done radio astronomy
for their PhDs. They knew how to do that, and
they were like, all right, well we have this awesome telescope.
Why don't we point at the sky and see what
we see. We got some questions about you know, they
(35:48):
wanted to follow up from basically from their THESS and
do some more research. So they just sort of like
took advantage of this existing thing and started trying to
do some research. I see. So they were originally scientists
and they probably hoped they could use it for signs,
but they had this pesky engineering problem they had to
work on. But then when that got canceled, they could
do signs on it. Yeah, And so they had this instrument. Now,
(36:09):
Dickie was building one for himself over Princeton because he
knew what to look for. Penz S and Wilson they
already had it, but they didn't know what to look for.
They weren't looking for the cosmic marcrotwave background. They didn't
know what existed. It wasn't on their radar, so to speak,
at all. They were just trying to build a sensitive
instrument so they could listen to the sky. And you know,
they're great engineers, and they built this really awesome telescope.
(36:31):
If you look at pictures of it, it it looks kind
of funny. It doesn't look like a telescope you see
often because it's only part of a parabola. It looks
sort of like a big shovel, like a big scoop,
because it's only a little sliver of a parabola. Because
they wanted to be really careful and only pointed towards
the sky, so it's like really well shielded from the
ground and just gathers a bit of the radio waves
from the sky. Now did they set out to look
(36:53):
for this cosmic microwave background or were they, you know,
hoping to look at stars and black holes and things
like that. They were not looking for this at all.
They had no idea this thing existed as a concept,
and they had no idea that it was possible to
see it. One of them was interested in like finding
big clouds of hydrogen that were glowing, so they wanted
to look for other stuff. But they were really good
(37:13):
engineers and builders, and so they built this thing, and
they cooled it really really cold, because what you want
to do for your radio telescope is not absorbed signals
from like the telescope itself. Remember, everything glows, including your telescope.
So they had to cool the whole telescope down to
four point two degrees kelvin so they didn't like swamp
itself with its own radio signals. And then finally in
(37:35):
July nine, while Dickie is over there building his own telescope,
they turn it on and what they saw was a
lot more noise than they expected because they had done
such a good job of like cooling everything that they
expected to hear this clean signal. But really they saw
this like giant hiss in the radio wave spectrum. Yeah,
they saw this giant hiss, and they pointed their telescope
(37:57):
in different directions. It's on a big wheel, so you
could like turn it this way and that way in
the other way, and they just couldn't get rid of
this hiss. And they like took apart all their electronics
and replaced them. They like put another layer of shielding
on everything, They cooled everything down a little bit. All
this made like a very small amount of difference, reducing
the noise a very small amount. But they couldn't get
(38:17):
rid of this hiss. I see. They were trying to
get rid of the science signal, but they did because
they didn't know it as a science signal. Yeah, exactly.
They thought it was just noise that was going to
interfere with their science. And at one point they found
a bunch of pigeons that were nesting in their telescope,
and they had covered part of the electronics with pigeon poop,
or as they called it in their paper White Poultry
(38:38):
Dialectic Material, and they cleaned all that off, but it
didn't help anything, and so they were very disappointed. You know,
at the time, Wilson says, this was a huge disappointment
for us scientifically, And they spent like a year plunking
away at this thing, trying to get rid of this noise.
They had no idea what they were looking at. Well,
in a way, they were right, you know, like if
(38:58):
they were trying to get you know, radio waste, like
those from a cloud of hydrogen somewhere, this is sort
of noise that gets in the way, right, Like the
universe just has this noise. They just didn't know it
was a feature of the universe absolutely. You know, one
man's noise is another woman's signal as another woman's Nobel prize.
And we have that in particle physics. All the time
we were looking for the top cork, and now the
(39:19):
top cork is an obstacle in finding other particles. We
wish we could like turn it off and get it
out of the way so we could see other stuff.
And so yeah, it's very subjective, all right. So then
they thought they had some sort of error or some
sort of equipment failure for over a year, and then
how did they realize that this was something of interest?
So Pensis, one of the guys who built this telescope,
(39:40):
happened to run into one of his friends, Bernard Burkey,
on an airplane, who told him that Dicky over Princeton
was looking for this exact thing. So Pensis is like
complaining about how we have this his in our telescope.
Oh my gosh, we don't understand it. And he says,
you should talk to these guys at Princeton because I
think they know what you found. Oh wow, no kidding
on an airplane, on an airplane, just like by chance.
(40:01):
And I'm guessing this is, you know, the sixties, So
they were, you know, we're in ties, drinking cocktails, smoking. Yeah,
it sucking in the plane right over the loud propeller noises. Yeah.
So Pensy has calls up Dickie at Princeton and says,
I heard about this thing you're predicting. Dickie sends him
a paper written by his student John Peebles, predicting this
(40:22):
noise and explaining exactly what it should look like. And
Pensys is like, wow, this is exactly what we are
seeing in our telescope right now. They had no idea,
you know, what does it mean? What it looks like?
Should like it? Should it have a specific like signature
and when you look at the signal in the frequency spectrum,
or should it have this particular shape to it, or
what is that like? How would you recognize it? Yeah,
(40:43):
it looks like what we call black body radiation. So,
as we said earlier, everything in the universe that has
a temperature glows, and it glows at a specific frequency,
but not at only one frequency. It tends to peek
at a frequency and then have a particular shape. So
at one frequency you'll have the high it's intensity of radiation,
and then at the nearby frequencies it will sort of
fall off in a very characteristic pattern that we call
(41:06):
black body spectrum. And so what they saw was the
frequency of something at two point seven degrees kelvin glowing
with black body radiation. And so it wasn't just like
we saw a bunch of photons of this one number,
like they saw the whole shape. You know, it's like
if you saw a mountain of a very specific shape
and somebody predicted seeing a mountain of exactly that shape.
(41:27):
You'd be like, okay, you've understood how that mountain came
to be because black body radiation. I think it doesn't
just look like a bell curve, like a random noise curved.
It actually has kind of a shape twit, right, Yeah,
it has a shape. It's asymmetric around the peak, so
it's very characteristic. All right. So then Dicky's like, oh,
like I'm building the cells coope, but these guys already
have it and we've been scooped. Yeah, exactly. There's a
(41:49):
famous story where Dicky gets off the phone from talking
with Penzias and says, boys, we've been scooped. And that's
really kind of a bummer for Dicky because he's the
one who had this idea to look for it and
started building his telescope, like that was really the ingenuity,
and Penzias and Wilson just sort of like stumbled across it,
had no idea what they had found until Dicky told
them that's what you get for answering the phone, Daniel,
(42:11):
That's why I never answered my phone. It could be
somebody trying to scoop. So then they worked together. Everyone
was a very good science citizen at that point, and
Dickie like explained to them what they were looking for,
and they all agreed to publish together. So Dicky and
his crew published a paper saying, we predict that if
you looked in the sky this frequency, you could see
(42:33):
the afterglow of remnants from the Big Bang and it
would look just like this, and you can do it
and it'll be very interesting. And then in the same journal,
the next paper is Penzias and Wilson saying, by the way,
we've looked in the sky and we see this weird glow,
we think it might be explained by this previous paper
you just read by Dicky and his group. Interesting, it
was a two part series. It was a two part series.
(42:54):
And this is nice. You know when scientists who are
working on something and realize they're sort of in competition
or in working in parallel, they decided to publish together
rather than like have some crazy race to who gets
their paper in one minute before. Yeah, that's that's pretty cool.
So then, because I guess Dickie didn't have his telescope ready,
It's not like he could have just like jumped in
and found the signal. He just still ways away from
(43:16):
having a functioning telescope. Yeah, he had been scooped right,
and just by chance, if Penzias and Wilson had waited
another year or something, then Dickie could have had the
idea and the data. But he didn't, And Penzias and
Wilson went on to win the Nobel Prize in nineteen
seventy eight for this observation. Wow, and also people's gut
it to write peoples who originally had this idea and
(43:36):
wrote the paper. He won the Nobel Prize in two
thousand nineteen for like other contributions to cosmic microwave background theory.
But Dickie in the end never won the Nobel Prize.
I seem so back then it went to the people
who have discovered it, not the people who predicted that
it would be there. Yeah, because if you look back
in history, it turns out that other people had already
predicted it, right. People in the forties had the idea
(43:59):
that this would be there, And there was this other
Russian group which in the early sixties had also published
a paper saying, by the way we might be able
to see this, people should go look for it. So
that was an idea which was sort of old hand
bubbling up around the world at the same time, and
maybe by a lot of those people who had died
or something. Right that you couldn't give him the Nobel
Prize for it, that's true. You can't give the Nobel
(44:20):
Prize to somebody if they've already died. Yeah, alright, Well,
so that's how we humans discovered the cosmic microwave background.
And it's something that's pretty significant, right. It tells us
a lot about the conditions for the early universe, about
the composition of the universe. It confirms things like dark matter,
dark energy. I mean, there's a lot in that signal. Yeah.
Hawking says it's the greatest discovery of the century, if
(44:43):
not of all time. And the reason is that it
is really very, very rich, like how the cosmic microwave
background looks, and specifically how it's not exactly smooth but
has these little ripples in. It tells us a lot
about how that early universe plasma was rating what it
was doing, and like ripples in that plasma are sensitive
to things like is the dark matter fraction of the
(45:06):
universe or five, because it changes how that matters, sort
of slashes back and forth if the dark matter is
interacting or not. So, as you say, we can fit
a lot of the parameters of the universe. A lot
of the questions about what the universe is made out
of and how it came to be come from understanding
that in great detail. And you know, years later people
launched a satellite to measure the cosmic microwave background radiation
(45:28):
very precisely. That was called the Kobe satellite, and then
that one a Nobel prize. So it's like a very
rich area of research. Right. There's not just a lot
of information in it, but it also kind of basically
confirms our theories about the early universe, right, Like it
it's like perfect evidence for all these series about the
Big Bang and inflation and the you know what was
(45:49):
happening in ing in those early few seconds. Yeah, it
definitely confirms the Big Bang, right It tells us that
the steady state theory just doesn't work because the universe
was once much more dense and hot and crazy, so
rules out the steady state theory and confirms the Big Bang.
It doesn't exactly confirm inflation precisely. There are some predictions
for like weird little wiggles in the CNB, we might
(46:11):
be able to see that would confirm inflation. And several
years ago there was an experiment called BICEP two that
thought they had seen that, but it turns out they
were wrong. But in the future, there's a lot more
we can learn about the universe. Whether inflation was right,
is it the right theory of what caused the Big
Bang in the very very early universe, We still don't know,
But we hope that there's more layers of information in
the CNB that will one day reveal even more about
(46:33):
the early universe and how it all came to be. Yeah,
there might still be more noble prices in there. Yeah,
there might be information in that data right now which
you could download onto your laptop and if you knew
how to interpret, could win you a Nobel prize. Sometimes
everything you need is right in front of you, or
I guess the dangerous you could download it, have it
on your computer and then not discover something, and then
(46:55):
in the future of some physicists and a podcast saying,
see that person had that data in his or her
laptop and didn't see so better to just just not downloaded
or just don't you never hear about how you were scooped,
you'll have an easier life, all right. Well, that is
how we discover one of the greatest discoveries a few
(47:15):
in history apparently, although I would argue that, you know,
that bowl of oat meal I had this morning was
pretty good discovering as well. I think brown sugar and
oatmeal that was a pretty big discovery. No thanks, no thanks, huh,
that's a level too far. Alright, that's for the future.
All right. Well, we hope to enjoy that story. Thanks
for joining us, See you next time. Thanks for listening,
(47:44):
and remember that Daniel and Jorge Explain the Universe is
a production of I Heart Radio or more podcast for
my heart Radio, visit the I heart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows. No
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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