Listener Questions 36

Daniel and Jorge talk about 3-armed galaxies, the color of the Universe and its phases.

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Episode Transcript

Speaker 1 (00:08):
Hey, or hey, do you ever wish you had more
than two arms? That would be weird, but sometimes it
would be useful. You know, if you're a parent, you're
carrying around a couple of kids, would be great to
have extra arms. Well, is it more arms do you
want or more hands? I think what I want is
maybe more brains. That would be handy. Then I can
have twice a number of thoughts, or one of them

(00:30):
could think while the other one naps, and then they
can take turns. I think I already have more ideas
than my arms and hands can handle. It. Sounds like
you need less brains then, or more arms, like a
whole army of arms. That would be pretty handy. It
would be quite a handful. I am hand with cartoonists

(01:00):
and the creator of PhD comics. Hi, I'm Daniel. I'm
a particle physicist and a professor at UC Irvine, and
I'm pretty sure I could make use of a third
arm if it had a hand attached to it. Where
would you put it? Though? In your body? Like at
the top of your head, that would be useful. I
was just gonna say it top of my head, yeah, exactly.
You could like scratch your nose or scratch your back.

(01:21):
Even that would be pretty handy. Yeah, but how would
you scratch your arm? I'd have two other arms for
that job, but would they reach I think the more
interesting question is how you would call them, Like is
it your right arm, your left arm, and your top arm,
or you're like your dominant arm, your subdominant arm, and
your sub subdominant arm. Maybe you could call it like

(01:42):
your color arm or your weak heart. What if it's
extra strong though, on the top of my head anyway,
lots of fun things to think about, Yeah, because it
is a fun universe with a lot to think about.
There are a lot of stars and galaxies and amazing
objects and invisible matter and will energy out there for
us to wonder about and to have questions about. No

(02:04):
matter which arm you'd like to use to scratch your head.
Welcome to our podcast Daniel and Jorge Explain the Universe,
a production of iHeartRadio in which we dig into all
of the heads scratching mysteries about the universe, Why it
looks the way it does, what color it is, if
we can even possibly understand it, Why everything out there
seems to be spinning, and why they spin in such beautiful,

(02:25):
worly patterns. We dig into all of the mysteries of
the universe, from the tiny quantum particle to the inside
of black holes, to the edge of the universe, to
its very beginning and its very end, because we love
these mysteries, and we love marinating in our understanding and
our ignorance. Yeah, because there are beautiful patterns out there
in the universe. Patterns in color, patterns, in shape patterns,

(02:48):
also in mysteries. It seems like the universe has sort
of a recurring pattern of always having things that are
difficult to explain or that don't reveal how they work
right away. It is interesting that the universe is mysterious,
but not so mysterious that we can't make progress. It's
like we are just smart enough to understand like the
next chunk of physics, but not so smart that we

(03:10):
figure it all out right away, but also not so
dumb that it's totally a mystery to us. We seem
to be sort of like fine tuned to be entertained
by the mysteries of this universe. You're saying, we're like
the goldilocks of all species in the universe, But how
do you know this, Daniel, how do you know we're
not behind? How do you know we're not actually like
at the back of the class roster. Yeah, we could be.

(03:33):
There might be aliens out there that I figured out
the physics of the universe and about ten seconds. But
what I'm saying is that maybe this is more fun.
Maybe it's more fun to be a little confused for
a while and then figure something out, rather than just
have the entire theory of everything come to you in
a single flash of insight. That sounds like something a
student who's not doing well in school might say, like, Hey,

(03:54):
I got an F because it's it's fun. It's more
like somebody who wants to keep the mysteries on because
it's part of my job. I mean, if we like
solved physics tomorrow, then what would I do the rest
of my life? Is that what you tell the funding
Agency's like, Hey, you paid me all this money and
I haven't figured anything out, but I'm having a lot
of fun. And really what's more important than that. It's

(04:16):
the friends you make along the way to figuring out
the universe. That's right, I got an F on my
research paper, but F stands for friends and fun. Not funding.
And it's not just people like me who are wondering
about the nature of the universe and enjoying thinking about it.
It's everybody sciences of the people, by the people, and
for the people, and that includes me and you. It

(04:38):
includes anybody who thinks about the universe, wonders why it
works the way that does, and tries to figure it out.
That's right. Everybody has questions, and sometimes we even answer
those questions on this podcast, although sometimes the answer is
we don't know. All too often the answer is we
don't know, so give us some money to figure it out.
Stay tuned. But we encourage everybody out there to engage

(05:00):
with their curiosity, to look out the universe and connect
with their personal questions. You know, something that I think
maybe people don't appreciate is how science is driven by
individual people's curiosity. The reason we study this and not that,
the reason people investigate the mating patterns of South American bats,
is because somebody has decided that that's the most important question,

(05:23):
the one to dedicate their life too. So I like
to encourage people to think about what is your most
important question? If you could ask a single question of
the universe and get an answer what would it be?
And so we encourage our listener to think about the
universe and to write to us with their questions. Yeah,
we get questions all the time, and sometimes we even
answer them on the podcast. We will pull up a

(05:44):
question that we get and we'll try to give you
our best answer on the air. Answer Right. We answer
all of our questions that listeners send us to questions
at Daniel and Jorge dot com. But sometimes there's one
that I think is especially intriguing or requires a little
bit of background research, so we answer it here on
the podcast. And so today on the program, we'll be
tackling listening our questions episode number thirty six of our

(06:13):
listener question series That's Right, which puts us well above
a hundred in terms of questions answered on air. And
do we have a theme for this set of questions?
This one's sort of like big questions about the big Universe.
I see the usual then everything exactly. Today we have

(06:34):
questions about questions exactly. Let's fall into the big questions category.
All right, big questions here today we have three awesome
questions about the shape of our galaxy, about the color
of the universe, and also about whether the universe is
maybe tearing itself apart. You mean emotionally or like physically.
I think first physically and then emotionally. If you tear

(06:56):
yourself apart physically, then if you want to really be
able to tear yourself a part emotionally, Yeah, that's true.
Depending on how the universe collapses, you might not have
time for an emotional response. Well, let's dig into these
questions because they're pretty interesting. The first one comes from
Matt from Indiana. Hey, Daniel and Horey. This is Matt
from Indiana. I was just reading an article which has
some of the most recent Hubble pictures now that it's

(07:17):
successfully returned to prime time. The question I have is
about the galaxy aarp m adri zero zero zero two
D five H three. NASA is saying it's noteworthy as
it only has three arms to it and most spiral
galaxies have even numbers. Why wouldn't we find an equal
amount of even an odd armed disc galaxies symmetry. I'm
perplexed on this. Thanks for your time, cheers, Matt. All right.

(07:38):
Awesome question from Matt. He's asking not about the milk Away,
but a different galaxy that the Hubble Telescope has found. Yeah,
we have imaged so many galaxies. You know, when you
look up in the night sky, you mostly see stars,
but behind those are tiny little smudges which are galaxies.
And as we saw from the recent James Webb Space
Telescope images, every tiny little dot of sky is filled

(08:00):
with galaxies, and they have lots of really interesting shapes
and characteristics. And so now we have lots and lots
of examples of what other galaxies look like. And Matt
is asking about one particular one that NASA said was
a little weird. Yeah, and he spelled out the name
of it. Maybe we should spill it out again in
case anyone wants to look it up. Yeah, that's galaxy
AARP DASH M A D O R E. Then the

(08:22):
number is two one one five dash two seven three
And we'll put a link to NASA's page about this
in the show notes. They just got a catchy name,
my daughter. It sounds like I love you or something. Well,
if you look up the image and the link on
our website, you'll see basically a picture of our galaxy.
But it looks kind of interesting because it's got two
short arms, but then a one long arm on the bottom. Yeah,

(08:43):
lots of these spiral galaxies have the same basic features
you have, like a central bar and then some arms
swirling around them. And this one is a little weird because,
as you say, it has two sort of shorter arms
and one longer arm. And that's the thing that Matt
picked up on that the fact that this has three arms,
according to this press release, having an odd number of arms,
like not two or four or six is a little weird.

(09:05):
You mean, it's a little odd you have an odd
number of arms, because I think we're kind of used
to arms coming in pairs, right, I certainly have two arms,
though i'd like a third. But if we're talking about galaxies,
then it sort of makes conceptual sense to imagine them
being even numbers, like or basically there's just two arms
because you have the central bar and then the arms
swirling off around it. But it turns out that galaxy

(09:28):
arms are a lot more complicated than you might imagine.
M Well, let's dig into it. First of all, why
do galaxies even have arms? And I guess maybe we
should define what we mean by arms. It's kind of
like a you look at a picture of a galaxy
you see a cluster of stars, but then you see
these kind of like tendrils, these rows of stars kind
of swirling from the center of it. That's what an

(09:48):
arm is. Yeah, and so we tend to call these
things spiral arms. And there's really two things going on there,
the spiral nature of them and the arms. Right, So
let's first talk about like why are these things spiraling
at all? Why is there a spiral pattern in the galaxy.
And that just comes from the fact that the galaxy
is spinning. So everything in space is spinning, and as

(10:09):
it collapses, it spins faster and faster. The things a
different distance from the center of the galaxy don't always
rotate at the same like number of angles per second. Instead,
they tend to move through space at the same linear speed.
So galaxies don't rotate like a DVD or a compact disc,
where like every point along some line rotates with the

(10:29):
same angular speed. It's more like they rotate like runners
going around a track, where people on the outside tend
to fall behind even if they're running at the same speed. Well,
maybe let's take it a step back. Because you mentioned
everything is always spinning. What does that mean? Wh are
things in space necessarily spinning or do you mean, like
everything's moving but relative to like the center of gravity

(10:52):
or the center of a cluster of stuff, you're sort
of spinning around that. So everything in space is sort
of whizzing around. And remember that spinning is relative to
an axis. You like, draw a line through space and say,
are things moving around this point? And so you can
pick any axis you like. You know, pick like the
center of the sun. That makes sense to think about

(11:14):
the motion of the Solar system, or you know, the
north south axis of the Earth. But you really could
pick anything, but it makes most sense to pick like
the center of mass of a big blob of stuff
and ask are things moving around this center of mass?
And because everything is sort of flying around through space,
it's not stationary with respect to like the center, then
all that stuff tends to add up to some spinning.

(11:35):
Like it's possible for a huge blob of stuff to
not be spinning, but that would require everything inside of
it to like exactly balance all of its motion. It's
sort of unlikely, like flipping a million coins and having
exactly fifty percent of them land up heads. So any
big blob of stuff tends to have some spin around
its center. Yeah, so I guess you know, things tend

(11:57):
to fly in a straight line in space. But once
you get a bunch of sort of in the same area,
it's going to have some gravity and it's going to
start pulling stuff inwards towards the center of massive that blob,
and that's where the kind of the spinning happens, right,
That's where the circular emotion happens. And so that's why
everything's kind of spinning around a galaxy cluster m exactly.
And as that's been happens, it very naturally forms a

(12:19):
spiral pattern, right, because things that the outside get left behind.
They're not spinning as fast as things closer in. Like
if you're really close to the center, it doesn't take
you as long to go all the way around the galaxy.
For example, if you're really far out and you're moving
at the same speed, takes you a lot longer to
go all the way around the galaxy. So things and
the outside tend to get left behind, and that's why

(12:40):
you end up with spiral patterns in the galaxy. But
that doesn't explain why you get arms, right, if you
just have like a big blob of stuff and it
was spinning and collapsing, it would tend to sort of
like wind itself up. You wouldn't necessarily get blobs like arms.
So the spinning explains the spiral nature, but not the arms. Right,
Like if you had a big blob of out there

(13:00):
in space and that was evenly distributed, like a hazy cloud,
and then you just got it going, you would think
it would just kind of like swirl towards the center,
kind of like a toilet, right, there'd be no clustering.
It's just like a like a tornado, like an even
swirl down to the center. Yeah, Like if you put
a fork in spaghetti and spin it, you're gonna end
up with lots and lots and lots of strands, not
like a few big clumps. But what we see in

(13:22):
galaxies is it we've got like really big chunks. We
got like two or four or three in this case,
chunks of stuff flying out in this spiral pattern, or
more like the three giant or three or four giant
spaghetti noodles, right, instead of like a bunch of little
spaghetti noodles. Somehow, the spaghetti's kind of clustering to giant
strands of spaghetti. Yeah, exactly like metapasta or something megapasta formations.

(13:48):
And so a lot of people think that when you're
looking at a galaxy and you're looking at these spiral arms,
that you're looking at structures of matter, that like, the
arms are a blob of stars like a blob of spaghetti,
and that whole arm is sort of rotating, that the
stars are moving with the arm. But that's actually not
the case. The arms are not structures of matter. They're

(14:10):
just density waves. They're more like traffic patterns in cars,
you know, like a traffic wave can move along the highway,
making some cars slow down and some cars speed up
or clump together, But the cars don't necessarily move with
those waves in the same way the arms in the
galaxy are rotating. But stars don't necessarily rotate with the arms.

(14:31):
They can be left behind by the arm, the arm
can catch up with them. The stars don't move with
the arms. Well, first of all, what do you mean,
because there aren't the arms made of stars? Like, if
we can see them in the night sky in space,
that means it's bright, and so that means we're seeing
the stars in them. Yeah, they are made of stars.
For sure, the same with the like traffic patterns are
made of cars. But the things that make the arm

(14:52):
the arm is that there's a denser spot of stars.
There's more stars there than somewhere else. But as the
arm moves, sort of moves through the stars the same
way that like waves move through water, but the individual
particles of water don't necessarily move with the wave. Right,
the wave is motion of the water. Oh, I see
what you're saying. You're saying, like if I looked at

(15:14):
a sped up or fast forwarded movie of a galaxy,
I would see it looking like it's a squirrel, like
it's spinning, But it's not actually spinning, you're saying. It
just has these waves running through it that go around.
The waves are spinning, But if you tracked a wave
and you also tracked an individual star, you would not
necessarily see them move together, like a star can be

(15:35):
part of an arm and then later not part of
an arm, and then part of another arm. Whoa, and
so how do we know this because we haven't been
looking long enough for us to see that. Yeah, it's
a really interesting idea. It's only been around for a
few decades, and it's not one hundred percent certain, though
in the last few years we've got some evidence that
this is true because we've looked at the color of

(15:56):
light in these stars. Because the galactic arms tend to
be aligned with star formation, these galactic arms are places
of greater density, which means you get more stars being
made because you're compressing the gas. So you tend to
have younger stars in the arms as they are forming,
and younger stars tend to be bluer because bluer stars
don't live as long. So anyway, the long story short,

(16:17):
you can look at the pattern of color in these
arms and you can see how sort of how old
they are and the age of stars within the arms,
and so you can sort of confirm this hypothesis, though
I should say it's not a one hundred percent totally established.
So you're saying the arms of a galaxy are actually
kind of like waves that are going through the huge

(16:38):
cloud of stars in the galaxy. But what's causing these waves?
So these are density waves, So they're just caused by
things not being totally smooth, the same way like all
gravitational effects are. If you have a little perburbation, things
aren't totally smooth. Then gravity tends to pull on that
and exaggerated, so gravity will take a little perburbation in

(16:58):
like a totally smooth clump and turn it into larger
and larger perturbations. So it's not again totally understood where
these come from and why they last so long. But
they think they come from original density perturbations and like
the central clump of the galaxy. So they are structures.
Then you said earlier that they weren't structures. So it
is there because the stuff in it is kind of

(17:20):
holding together gravitationally. Yeah, but it's a density structure. It's
not like a matter structure. It's not like the same
stars are sweeping around and staying in the arm. There
is a structure there at the density structure, right, and
that you're saying the density is caused by the gravity
between them. So let's see, I'm a planet or I'm
a star around a galaxy. What's going to make me

(17:42):
want to join one of these waves. Well, it's sort
of sweeping through the galaxy and it creates regions with
higher gravity and regions with lesser gravity, and so some
stars are like getting pulled towards these things, and some
stars are getting left behind right, And so that's how
a density wave propagates. Right, it creates regions of great
and lesser force, which tends to apply differential forces on

(18:04):
the stars. Right. But unlike a wave and water, you
have forces that pull and push, right, like something behind
you pushes you forward, but then some in front of
you pushes you back, and that's kind of how the
wave occurs. But in gravity, gravity only attracts. So what
moves the wave forward? Well, what's moving the wave forward,
Like at the forefront of the wave, it's density, So

(18:25):
it's pulling those stars towards it. Right, So the density
of the arm creates a denser region in front of it.
Oh I see, So the wave in front of it
eats up more stars, which moves the center of gravity
of the arm forward, which then leaves behind the stars
behind it exactly. And so that's how a density wave propagates.

(18:46):
And what's really interesting to me is that you know,
the velocity of the arms is not the same as
the velocity of the stars. That means where your star
is in the galaxy determines whether these density waves are
passing you or whether you're passing them, like for example,
our sun moves around the center of the galaxy at
a certain speed, which is basically determined by where it
is a distance from the center, And so it's actually

(19:08):
moving around the galaxy about twice as fast as the arms.
So we are catching up to arms and passing them by.
But if we were further out, then the density waves
would be passing us by, and so that's where arms
come from. Now. Matt's question was, why is it weird
that this one galaxy that we saw has three arms?
Why is it weird to have an odd number of arms?

(19:28):
So they make this comment on the page describing this galaxy.
So I chatted with a couple of experts about galaxy formation,
and they quibbled a little bit with this claim that
it is unusual. First of all, they say, it's not
even really easy to define, like how many arms a
galaxy has, you know, because it's basically just visual inspection.
You're just sort of like looking at it and seeing sorrels.

(19:50):
But you know, galaxies have more complex structure than just
like here's an arm. There's an arm. Like if you
look at the Milky Way our galaxy, it has sort
of two major arms, but lots of like little spurs
off of it. For example, we live in the Orion spur,
which is like a little offshoot from the major Sagittarius arm.

(20:10):
So is that really another arm or not. It's not
like a well defined way to count these arms. It's
just sort of like by looking at it, M I
see so's it's it's hard to define what makes an arm.
It's hard to define what makes an arm exactly. And
so you look at this particular galaxy and you're like, yeah,
I could call that three or I could call that
four maybe. And so the short answer is that I

(20:33):
don't think there's broad agreement on how to define arms
or how many arms it makes sense for galaxies to have. M.
I guess my question would be, if you look at
all the galaxies that we can see out they're in space,
what is more common? Is it more common to have
an even ish number of arms or an odd ish
number of arms. Yeah, it's a great question, and it's

(20:55):
a hard question to answer without like a systematic way
to analyze these things. Basically, a human has to look
at it and say, I think it has three, But
another human might look at the same galaxy and say, no,
I think this one has four. So to get like
enough statistics to do some analysis of that, you need
some like really rigorous way to analyze these things. And

(21:15):
people have done like for any analysis or the distribution
of density waves through galaxies, But that's really just a
way of counting like the strength of these things. Again,
you have the problem of deciding when to call it
another arm. So right now is really just mostly anecdotal.
People have seen a bunch of galaxies and they haven't
seen ones that look like this to them, And there
are ways to explain it. Like if you look at

(21:36):
a galaxy like this and you say, how did this
galaxy get this way? Well, one possible explanation is that
it recently had a strong gravitational interaction with another galaxy
that sort of messed it up. Because this one also
seems sort of asymmetric, right It's got like one long
arm on one side and two shorter arms on the
other side. So it may just be that like a
passing galaxy sort of pulled on it in a way

(21:58):
it separated those density waves. M But I mean, I
guess is it easy to pull up pictures of galaxies
that look like they have three arms? Is it maybe
harder or easier or the same as pulling up pictures
that looked like they have four arms or two. I
think it's probably true that most of the galaxies you
look at, if you've just counted them, you would probably

(22:18):
get an even number of arms. A lot of them
just look like they have two, though they're sort of
like tightly wrapped around. But look at the Milky Way,
for example, it's not easy to say, like how many
are there? Like I count one, two big ones and
at least two maybe four little ones. Although we don't
really have a picture of the Milky Way, do we.
We certainly don't have an actual image of the Milky
Way from the outside, though we can reconstruct the density

(22:42):
of stars in the Milky Way using a lot of
our observations. Right, well, could there be maybe some effects
we are talking about waves right around sort of a
fixed medium. Is it possible that, you know, given the
typical size of a galaxy with the typical number of stars,
maybe like a standing way of four arms is more

(23:02):
likely than a standing wave of three arms, you know,
like waves around the spiral of the galaxy. I read
some papers about these things, and there's are some arguments
for why you might get two or four if these
things really do come from like density perturbations in the
center of the galaxy, because you would expect that to
be somewhat symmetric, right, that it would cause similar effects

(23:24):
in one direction and in the other. And so it
makes some sort of sense for this thing that collapse
into a bar that then generates two arms, and that
those might split, but that splitting would always give you
an even number. So there are some papers suggesting that
you would expect, on average to get an even number
of arms, and I think that makes some sense, but
it's not very well established. Well, so then the picture

(23:47):
that Matt saw, he saw I did an article that
said that NASA think is weird to have an odd
number of arms? What was NASA saying there? So the
quote the article says, while most disc galaxies have an
even number of spiral arms, this one has three. But
you know, the astronomers I talked too, quibbled with that
a little bit. They didn't think it was so weird.
They've seen galaxies with three arms before. M I guess

(24:09):
we'll have to ask NASA. I mean, what do they know.
Let's have them on the podcast. All right, Well, I
think that answers Matt's question, which is like, maybe it's
maybe it's not that weird, right, It seems like some
astronomers don't think it's as weird to have three arms.
It seems like it's kind of a fuzzy thing. Anyways,
it is. But what is weird is that arms exist
at all. It's really fascinating in the dynamics of galaxies.

(24:31):
They have these things slashing and swirling around, and it
just reminds you that galaxies are dynamical objects. They're not
fixed things that have been formed millions of years ago
and unchanged. Right, they are swirling, they're crashing into each other,
they're constantly changing, just on these vast, vast time scales
that we can hardly even imagine. Yeah, and they're not

(24:52):
just dynamic, they're like wavy, right, They're rippling. That's what
these arms are. They're ripples in their structure. All right, Well,
let's get into some of our other questions. One is
about the color of the universe and the other is
about the fate of the universe. So let's get into those.
But first let's take a quick break. All right. We're

(25:21):
answering listener questions here about everything is usual, the whole
she bang, the whole universe. And our second question comes
from Genie, Hi, Daniel and Hagee. The question I would
really like to ask is did the universe have a
color after the Big Bang? If there was no color,
when was there first a color? And what was it?

(25:42):
Thank you have all the questions we've gotten, this is
the one that really threw me for a loop, Like, Wow,
a question I've never even thought of before, never heard
of before. What a super fun question. Yeah, it's a
very colorful question. Jennie asked, did the universe have a
color after the Big Bang? So I guess a big
bang happened, and I guess her maybe her question is like,

(26:03):
if there was a human present there, what would it
look like? Would it look red, purple, green, polka? Or
would it just fry your eyes? Yeah? It really is
one question what would you see if you were there? Right?
Really love this question and I think it's really fun
because it makes us think about like what is color? Anyway? Yeah,
let's dig into that. What is color? How would you

(26:24):
define it? I know it's related to the wavelength of
the light. It is related to the wavelength of light,
But I think it's important to distinguish, right, Like, photons
have a wavelength, which means like how long it takes
for them to go up and down. It's related to
their frequency, right, how many times they wiggle per second.
But the color is not a property of the photon,

(26:44):
like photons themselves don't have color. Color is something inside
your head. It's like how your brain responds to a
signal of a photon of a specific color, So it's
not part of the photon itself. It's like the taste
of salt itself. Doesn't have a taste your tongue as
a response to sensing salt. Right, I guess you're sort

(27:05):
of quivaling about the definition of things. But I mean
light does have different wavelengths, right, it does. But there
are lots of wavelengths of light that we can't see
and our brain doesn't respond to. So photons above the
visible spectrum like have no color to them. Early, they
have no color. So far, we could panically start naming
other colors, right, Yeah, absolutely, you could even imagine creating

(27:29):
a new internal response that's a different color than anybody
has ever imagined before. Right, If colors are really just
part of your mind, If there are a response to
signals from your optic nerve that in principle there's no
limitation on experiencing new colors, not just combinations of existing colors,
but like brand new colors, and so in principle that's possible,

(27:51):
and you could assign those to very high frequency light.
You could imagine like building a technological eyeball that sends
messages to your brain. Your brain would learn to interpret
those responses by giving you some new experience that would
be like a new color. Yeah. I think what you're
talking about is that you know, light has a certain
frequency that can come in certain frequencies, and let's say
like seven gig gigga hurts or something, or like seven

(28:13):
hurts might be a frequency. And when I see that
frequency of light, I think the color green, for example,
And you and I agree that if we see light
at this frequency, if we're going to call it green.
But I think what you're saying is like, maybe what
I experienced this green is different with them what you
experience is green. That's certainly true. And there's only also
a narrow band of photon frequencies that we even have

(28:36):
colors assigned to, and sort of the long history of
the universe is that it started out really really hot
and dense, and photons created in the very very beginning
of the universe after the Big Bang had very very
high energies, very high frequencies. Then the universe is cooling down,
and so the photons created get longer and longer, right,
lower frequencies, and so the universe sort of starts out

(28:58):
invisible and then passes through the visible spectrum. And so
like Genie's asking, what color was the universe when it started? Right,
And the problem is that the energy of the photons
at the very beginning of the universe don't really have
a color. They're too high frequency for us to fc right,
because the energy of a photon is related directly related
to its frequency, right, Like the higher the energy, the

(29:20):
higher the exactly, and hot stuff tends to make higher
energy photons. We've talked about this on the podcast a
few times. Everything generates photons. Everything that has charged particles
inside of it generates photons, and it generates photons based
on its temperature. So the Sun generates photons as some
temperature because of its thousands of degrees kelvin, the Earth

(29:40):
glows and generates photons at some temperature because it's much cooler,
and you generates photons at some wavelength. Your eyes can't
see the photons generated by yourself or by the Earth.
They can see the ones from the sun. So some
of these photons are visible and some of them are invisible.
But the hot or something is the higher energy the
photons it generates. Right. So are you're saying maybe at

(30:01):
the Big Bang everything all the photons that were there
were super high frequency or low wavelength. What are you
saying that? Initially at the Big Bank things were so crazy.
All the photons were super duper high energy. They were
super high energy, which means very short wavelength, which means
very high frequency, right, And so these photons were zipping

(30:22):
around the universe. And if your eyeball was there just
after this moment, when the universe was like at the
Plank temperature, then not only would it be cooked instantly,
but the photons that hit it it wouldn't know how
to interpret. Your eye wouldn't see them, So the universe
would just be black, even though it'd be super duper
hot and filled with photons. Yeah, Like, if your eye
could somehow survive being in a Big Bang, it wouldn't
you would see total darkness, right, because all the light

(30:45):
would be sort of like X rays, they just passed
through your eyeball. One question is would they interact with
your eyeball or they passed through like X rays, right.
X rays do interact with some parts of your body,
but not others. And as a frequency of photons change,
there are chances of interacting with you changes. But you're right,
a lot of these photons might just fly right through you,
like X rays, which are higher energy photons than our

(31:05):
eyeballs can see. But then the universe temperature changes. But
then eventually, after the Big Bang, the universe started cooling down, right,
and so you started seeing photons with a lower energy, yes, exactly.
So as the universe cools and it's really dense, plasma
gets more and more dilute, it cools down, and so
it starts generating photons with longer wavelengths. So as time

(31:26):
goes on, the temperature of the universe is dropping and
the energy those photons is dropping, and so the wavelength
is increasing. So they're like the general light of the
universe started off way too high for our eyes, but
then it gradually as it cools starts to approach the
visible spectrum. Yeah, and there's a really fascinating moment around

(31:46):
three hundred and eighty thousand years after the Big Bang
when the universe cooled so much that atoms could now form.
So you have protons and electrons whizzing around with so
much energy that they couldn't be bothered to bond together.
But after a certain time things cool down those electrons
that it no longer had enough energy to escape the
pull of those protons which have a positive charge and

(32:08):
pull on the electrons, and so you get neutral hydrogen forms.
And in this moment, the universe goes from being opaque
like a really hot plasma like the center of the Sun,
to being transparent, just like clouds of gas in space
that light could mostly pass through. So all the light
generated before this moment was just reabsorbed by the hot plasma.

(32:28):
Light generated after this moment can fly through the universe,
and like hit your eyeball, and this light is still
flying through the universe. It's the cosmic microwave background light.
We can see it with our telescopes. When it was
generated at that moment in time, the universe was still
filled with a pretty hot plasma. It was like several
thousand degrees So that was the moment when the universe

(32:48):
first became transparent and the light that were created sort
of becomes persistent. Right, But still that light is too
high energy for eyeballs to capture. Right, Like when I
look up at the night sky, I can't see the
cosmic microwave background with my eyes, can I You cannot
see the cosmic microwave background with your eyes currently. But
when it was created, it actually was in the visible

(33:10):
spectrum because remember that the wavelength depends on the energy,
on the temperature, and when that light was created, the
universe was still pretty hot. It was several thousand degrees kelvin,
which is about the same temperature as the surface of
the Sun, which produces visible light. So when the CMB
light was created, it was in the visible spectrum. You
could have seen it if Jeanie had her eyeballs back

(33:33):
in the early universe. Back then, she could have seen
the CMB with her eyeballs. Now, you're right, when you
look up in the night sky, you don't see it.
That's because it's no longer at that frequency. It's been
stretched by the expansion of the universe. Down to much
much longer wavelengths, right, and that's why you need like
infrared telescopes, right exactly. But it's too low frequency for

(33:55):
us to see, right. It started out in the visible
spectrum and got stretched out below the visible spectrum very
very long wavelengths infrared, and so that's why we need
really sensitive telescopes in order to see it, because it's
now super duper infrared. And people say the temperature of
the universe is two point seven three degrees kelvin. What
they're talking about is the temperature a plasma would have

(34:16):
to be to generate the photons that we see in
the CMB. The plasma that actually generated those photons much
much earlier, was much hotter, but then it's light got
stretched out, so now it looks like a plasma that's
much cooler generated this light. Right. So that's a cosmic
microwave background radiation which comes from the moment when the

(34:37):
universe became transparent and not hazy. But that's I wonder
if that's really what would fit into her definition of
the first light, Like, you know that the light still
existed when the universe was hazy and opaque, right, yeah, exactly,
So backing up again, the universe started out really really hot,
and then as it cools, it passes into the visible spectrum.

(34:58):
That happened before this moment when the universe became transparent,
but just about the same time. It's like an interesting
overlap here that the universe became transparent around the same
time as it became visible. The temperature for hydrogen become
neutral is about the same as the temperature of the
surface of the sun where visible light is generated. Right, So,

(35:19):
then as the universe moved into the visible spectrum, what
would have been the first color that you would have
seen if you were there and was able to survive, Like,
what's the highest frequency color that we can see with
our eyes? Yeah, it'd be like the most violet violet, right,
it'd be like super duper purply blue is the highest
frequency light that we can seem. So then the first

(35:40):
color was blue, That was right. I don't know if
purple and blue are the same, but yeah, it was
definitely very very bluey, very purply blue, ultra violet, he said,
violet blue. All right, we'll go with purple. The first
color in the universe was purple, basically, Yeah, I think
that's true. It was purple. All right, Well, Genie, thank

(36:01):
you for that question. I hope purple is your favorite
color as well, because it is apparently the universe first color.
But you know, if there are aliens out there and
they have eyeballs and their brains interpret things differently, if
they brains give them like a red experience for that
same frequency and a purple experience for very low frequencies,
then aliens would say a different color was the first color.

(36:23):
And that's just because again, color is not part of
the universe, it's part of our brains. So it's a
very human thing to say that violet was the first
color in the universe. It was the first human color
in the universe, I suppose. Well, it's the first name
that the human would give it. But the frequency was
still the same, so we would all agree. I mean,
the experience I have a violet might not be the
same experience you have a violet, but we can all

(36:44):
agree that about that frequency. That's true. Yeah, though aliens
might be able to see much higher frequencies, and they
might say an even higher frequency was visible before our violet.
M I see, they might have a different first color,
assuming they call it color. Maybe they spell over the
K or something, but they put a U after the second. Oh,

(37:08):
I think you went too far there, Yeah, who would
do that? All right, well, I think then answers Jeannie's question.
Thank you, Jeanie. And so we'll get to our last question.
This one is about the universe tearing itself apart. So
let's take that apart. But first let's take another quick break.

(37:36):
All right, we're answering questions about the universe and our
last question. It's a bit dramatic, a bit drastic, it
certainly is, which is why we saved it from last.
All right, our last question comes from Courtney, and she
has a question about the universe. Hey, Daniel and Jorge,
I have a question for y'all. Is our universe tearing
itself apart? Is physics as we know and measure it

(37:58):
stable enough to be really light upon? If so, for
how long? If at the beginning of the universe the
electro week force broke in one moment, everything was whizzing
around at the speed of light, then suddenly the next
some particles experienced mass, fundamentally altering the trajectory of our universe.
Could we be looking forward to another dramatic change in

(38:21):
how our physical forces manifest themselves? Could we measure that
looking forward to hearing back? Thanks? All right, awesome question
for Corney. I think really what she's asking is does
she have to do her homework for tomorrow or do
that errente she needs to do? Or if the universe
just totally going to flip on itself or maybe she
could be doing other things today. Yeah. I did get

(38:42):
the sense that she was trying to make plans and
she wanted to know how far in the future she
needed to think, Like, if I buy this house, is
it going to be for sale in twenty years or
is the whole universe going to get shredded before that? Yeah?
Do I still have to pay my mortgage? Or can
I just buy the biggest mansion I can now because
the universe is going to end? That's right, real estate
investment advice from people you shouldn't be listening to about

(39:05):
real estate. Well, she's going to ask a multipart question.
She asked whether the universe is tearing itself apart, which
I guess maybe is related to her second question, which
is like how stable do we think the universe is? Like?
Is it going to stay like this? Forever. Can we
invest in real estate? Or is it possible for the
universe to suddenly change tomorrow or today or right now

(39:25):
and make it a whole different universe, And it maybe
that happened, we would we notice even I really love
this question because the touch is on one of the
most interesting ideas in physics that I think is not
very widely appreciated, And it's actually connected to Genie's question
about like the temperature of the universe. You know, we
think about the universe and how it works, but we're

(39:46):
really just describing the universe in one phase. When I
say phase, I don't mean like, you know, a toddler
throwing a tantrum. More like a phase is in the
state of matter. Like if you're a scientist and you're
trying to understand water, then you might have one understanding
of how works when it's a vapor, and another understanding
of how it works when it's a liquid, and another
understanding of how it works when it's a solid. Right,

(40:06):
we notice these phase transitions when water changes its behavior
pretty dramatically as it heats up or as it cools down,
and we can have a law that describes each of
those phases and in principle, if you had like the
ultimate theory of physics, you could have a single law
that describes all of them. But typically what we do
is we have effective laws to describe one phase at

(40:27):
a time. And so the universe, the whole universe is
cooling down, as we talked about a minute ago, and
so we think it's passing through different phases, and so
our current understanding of physics, a standard model of quarks,
the photons, the weak force, the Higgs boson, all that
stuff just describes the current phase of the universe in

(40:48):
the sense of like having an effective theory that describes
how things work right now, right because as we kind
of talked about a minute ago with Genie's question, the
universe kind of went through a pretty significant a change
early soon after the Big Bang, Like before this event,
everything all the matter, what's had so much energy, so
much velocity, so much going on that like not even

(41:11):
protons and electrons could hold together or come together and
stick into atoms and matter things that are just kind
of like a giant plasma. And then when things cooled,
when space expanded, things cool suddenly, like things clicked into
atoms and the stuff we see today, which is I
think what you're trying to say is similar to like
what happens to vapor or ice. It's like the molecules

(41:32):
are flying around, but at some point they lose so
much energy that some of the other forces in plate
start to click them together or to bring them together
as a liquid exactly. And what Cordy is bringing up
is another kind of phase transition, even deeper phase transition
than just like how do protons and electrons click together?
She was talking about the moment when things got mass.

(41:53):
All right, we've described the nature of the universes. We
understand it in terms of all these quantum fields that
are slashing around, and we talk about how the Higgs
field is there and it's giving mass to particles by
interacting with them and changing how they moved through the
universe and all of this stuff. But if you go
back to one of our podcasts where we talk about
the very early history of the universe, you know that
there was a moment before this happened, before the Higgs

(42:16):
field was giving mass to particles, when we still had
this description of everything in terms of quantum fields, but
effectively the universe was very different. Everything was basically mass
less electrons and quarks and all this stuff. We're flying
to the universe all at the speed of light before
the Higgs boson sort of kicked in and gave everything mass.
So that was another big phase transition in our universe.

(42:38):
Now that one's pretty fundamental, like the universe went from
not having mass to having mass. Things having mass, and
you said, something clicked, but like the laws of physics change,
or within our laws just some sort of potential change,
or we reached the threshold where suddenly the laws preferred
to be this way rather than having no mass, so

(43:00):
that the laws we have now describe the universe now.
And also before this transition, so same laws of physics,
but you have different temperature. And so as the Higgs
field was cooling down, it got stuck in sort of
a local minimum, and that's what she referred to as
electroweak symmetry breaking. It's got stuck in this sort of
weird spot where it treats w's and z's differently from

(43:21):
how it treats photons, and it gave those particles mass,
and it gives mass to the other particles sort of
because where it got stuck as the universe was cooling,
So it's the same basic laws of physics, but as
the universe cools down, the effect of those laws changes,
and one of the effects is that the Higgs field
got stuck in this weird spot and that's why these
particles have mass. And so really, I think her question

(43:43):
is like, do we expect further similar phase transitions in
the future or the universe that could fundamentally change what
we experience. Yeah, I guess she's not asking like can
the laws change? He's more asking like, is the universe,
like you said, is the universe stable? Are we like
in a spot where the basic configuration of the universe
is going to be the same, or can it change

(44:03):
like it did once before? Though, you know, it is
possible that the laws could change, because even though we
can describe the history of the universe pretty far back
using our laws and quantum fields, there's a moment beyond
which we can't right at the very very beginning of
the universe, just after inflation with things where at the
plank temperature. We think our laws break down there, and
before that we need something else, some theory of quantum

(44:25):
gravity that's deeper. We think that even our laws of
physics that do a great job of describing the universe
today and very very far back in time. They are
just effective laws. They're like understanding water when it's a
liquid and how it flows, but not deeply understanding the
true theory of water that would explain all of its phases.
So there is a sense in which the actual effective

(44:47):
laws of physics do change over time, though we don't
know what's going to happen in the future. We think
the universe is just going to keep cooling and probably
this current effective set of laws are going to hold fast.
But even if these laws hold fast, there might be
phase transition still in our future. Right. We talked on
the podcast once about how the Higgs field is sort
of stuck in this one spot, but it's not that stable.

(45:08):
We don't know if it's going to stay stuck in
that spot or if it's going to collapse and change
the masses of everything, and that would be like another
effective phase transition. So it might be that sometime in
the future, you know, maybe spurred on by particle collisions,
that some super collider could spark a change in the
Higgs field which creates an effective phase transition in the

(45:29):
basic laws of physics. Yeah, I think we talked about
this in our book. Frequently ask questions about the universe,
But you know, is the universe is going to end
at some point? Or how is the universe going to end?
And one possibility is for this Higgs field to collapse,
because it can collapse right like, it's sitting at a
place where it can still fall down in terms of energy. Yeah,
the reason the Higgs field does what it does is

(45:51):
because it has a lot of energy still stored in it.
It's like the whole universe is cooling down, but the
Higgs field got stuck and sort of staying hot. But
it's kind of like ball that's stuck on a shelf
and it could roll off that shelf and fall further
down in temperature. We don't really understand very well how
stable the spot it's stuck in is and what it
would take to sort of nudge it out of that,

(46:13):
and so there's a possibility that it could collapse even further,
and that would mean a change in the masses of
all the particles, which would mean like chemistry out the window,
need totally new chemistry, and you know, everything that relies
on chemistry, like life and podcasts also out the window,
and I guess buying a house also along with that.
But I think you describe it as sort of like

(46:34):
a spark and a spark propagating. I know we've covered
this in the book, but it's almost like if something
happens and does cause a Higgs boson to kind of
fall over or give up its energy in one spot,
it would basically cause the entire universe to do the same,
Like it would spread out like a wave. Right, if
it happened anywhere, it would spread out like a wave
propagating at the speed of light. So it may have

(46:56):
already happened somewhere else in the universe, and that wavefront
of phase transitions is heading for us or maybe not,
and maybe it'll be stable forever, right, And you're saying
that one thing that could trigger it maybe is building
a large particle collider, maybe under Geneva or something, yeah,
or around the surface of the Moon or around the
edge of the galaxy. It sounds like we need to

(47:18):
shut those things down right away. It sounds like we
need to build one and find out. That sounds like
exactly the opposite thing. You want to find out if
you can destroy the universe. I don't know. I'm pro curiosity.
I don't know how you feel. I am pro not
destroying the universe, because once you find out that you
can destroy the universe, you've destroyed the universe, Daniel, but

(47:40):
you've learned something along the way. No, because you won't
be here. Look what I'm saying, is nobody ever regretted
destroying the universe. Well, I think the answer here for
Corney is that go ahead and buy that house you're
thinking of buying. And maybe you should write to Daniel
tell him not to destroy the universe. Send your questions,

(48:00):
your ideas, your requests to not destroy the universe. Two
questions at Daniel and Jorge dot com. All right, thank
you everyone for sending us their question. A lot of
interesting things we've learned about here. I think we can
give ourselves a pat on the back, Daniel, maybe with
a third army out at the top of your head. Yeah, exactly,
it's busy scratching my head right now. You can give
yourself three handshakes. Triple high five. It would be the

(48:21):
highest of fives. M it would be a triple five. Yeah,
it would be a fifteen. All right, Well, thanks for
joining us. We hope you enjoyed that. See you next time.
Thanks for listening, and remember that Daniel and Jorge Explain

(48:41):
the Universe is a production of iHeartRadio. For more podcast
from my heart Radio, visit the iHeartRadio app, Apple Podcasts,
or wherever you listen to your favorite shows.