February 11, 2021 • 39 mins
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Episode Transcript
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Speaker 1 (00:08):
The world around you is like an amazing mirage. That
rock you see over there, it's not actually one object,
but a collection of ten to the twenty five particles,
all shaking and buzzing and wiggling together. That star you
see in the sky, those are photons generated from zillions
(00:28):
of kilograms of hot plasma that traveled billions of light
years before hitting your retina. That chair that's holding you up,
that's not solid. It's actually a web of atoms linked
together by electromagnetic forces. Physics gives you a way to
peel back a layer of reality and figure out what's
happening underneath, to see the world in a new way
(00:50):
by understanding its nature at the microscopic level and seeing
how all the incredible complexity in the insanity in our
universe arises from the simple interactions of a small number
of pieces. It's bonkers, but it's beautiful. Hi. I'm Daniel,
(01:22):
I'm a particle physicist, and I'm in love with the
insanity of our universe. And welcome to our podcast Daniel
and Jorge Explain the Universe, a production of My Heart
Radio in which we take a mental journey through the cosmos.
We think about how everything out there works. We try
to understand the craziness of neutron stars, of black holes evaporating,
(01:46):
the tiny, little, buzzing particles that make it all up.
We try to take the whole universe and wrap it
up so that you can understand it, or at least
understand a little piece of it. Because the universe is
not something that is understood. It remains an enormous cosmic mystery.
Though we have peeled back layers of reality to see
(02:08):
that most of what we are looking at is made
of elements, and those elements are made of even smaller particles,
which are made of even smaller particles. We have dug
deep into the nature of reality, but our questions are
not yet answered. We need to understand, and we have
not yet understood, the remain enormous mysteries about the nature
of the universe. What is most of the matter out
(02:31):
there in the universe? What is driving the acceleration of
the cosmic expansion of the universe. We have really basic
questions about how things work. But those questions are not failings.
They're not a disappointment in science. They are exciting opportunities.
They are the threads that we will pull on to
help us reveal the nature of the universe. They are
(02:53):
the clues that will lead us to incredible, mind blowing
discoveries about the nature of the cosmos, just the way
that our journey through physics so far has revealed so
many times that the universe is not the way that
we thought it was, since our intuition built up from
the times that we climbed down from the trees and
walked around on two feet and tried to understand this
(03:14):
world around us, that that intuition has often led us astray,
and that when we follow the science, when we carefully
build up knowledge by asking and answering questions, is when
we reveal the true nature of the universe. And it's
crazy and it's weird, and it violates our intuitions, but
it's still beautiful and it's our universe. And that's why
(03:36):
on our podcast we love to celebrate questions, not just
questions asked by scientists working at the forefront of knowledge
peering out into the depths of the universe, but your questions,
our questions, everybody's questions, Because if you wonder about the
nature of the universe, if you yearn to understand the
truth about reality. Then you are a scientist, then you
(03:57):
are asking questions. Then you would be surprised to discover
how many of your questions are the same questions being
asked by scientists. So don't be embarrassed to ask your questions,
ask them out loud, talk to people about them, try
to find the answers, and if you can't, send them
to us, because we love answering your questions. Everybody out
(04:18):
there who has thought about a topic and not quite
understood it, or heard an explanation about something weird and
crazy and it didn't really sink in, please write to us.
We will answer your questions. We're available online. We answer
emails to questions at Daniel and Jorge dot com. We
respond on Twitter at Daniel and Jorge, and sometimes we'll
(04:40):
take some of these questions and feature them on the
podcast and so on. Today's program will be answering listener
questions about Hawking, radiation, five G networks, and wireless charging.
As you might have gathered, my co host friend and
(05:01):
collaborator Jorge him is not around today, so I'm taking
this opportunity to dig into our backlog of wonderful, wonderful
questions asked to us by listeners. So I'll be digging
into a few questions from listeners, and you have lots
of opportunities to get your questions answers. You can email us,
you can tweet us. You can also come to my
(05:22):
public office hours. I hang out on zoom and answer
questions from anybody out there who's interested in physics and
wants to understand the universe. Check out my website sites
dot U, c I, dot E, d U slash Daniel
for all the details about the next upcoming public office hours.
All right, so let's dig into it and start answering
(05:42):
listener questions. This first one is an awesome question about
hawking radiation, black holes, and dark matter. Hello Dan, My
question is about talking radiation and the operation of BLAT. So,
if there is there's matter inside my cote, what had
it been necessary for hawking radiation to interact with the
(06:03):
dark matter in order to produce like holes completely. This
is such a fun question because it gives me a
little glimpse into what's going on in somebody's mind. Somebody's
thinking about black holes and hawking radiation and wondering how
that happens, and all of a sudden they run into
a wall. They think a whole lot of a second,
this doesn't make sense. How can the products of hawking
(06:23):
radiation annihilate with the dark matter inside the black holes?
And so they come to that point they don't understand it,
and that's when they reach out. And I love seeing
people do that, taking two ideas and trying to fit
them together into one understanding, because that's what we do
in physics, right We want a single understanding that explains everything.
You can't have one explanation for this thing and a
(06:45):
totally different explanation for that. We want a complete, holistic
view of the universe. So kudos to you for asking
this question. But before I dive into the details of
dark matter and black holes and hawking radiation, let's back
up and make sure we understand the basics of what's
going on in hawking radiation, because I think there might
be a small misunderstanding in the process, which is actually
(07:07):
leading to the core of this question. The first thing
you should understand about hawking radiation is that we do
not have a good microscopic understanding of how it works.
You know, we like to look at the world and
peel it back and understand how it works. At the
particle level and sometimes work back up from the particle
level to the macroscopic and say, okay, we understand this
(07:29):
temperature is just the buzzing of particles whizzing around, or
an electrical conductivity comes from how electrons are filling their orbitals, etcetera, etcetera.
But that's not something we have yet for Hawking radiation
because it relies on two things that don't play well together,
tiny little quantum particles which obey the rules of quantum
(07:49):
mechanics and gravity, and gravity and quantum mechanics don't play
very nicely together. We do not understand gravitational effects on
individual quantum part nicles. That would require a theory of
quantum gravity, which we don't have. So Hawking radiation actually
doesn't come from a microscopic understanding of what happens to
(08:10):
quantum particles near the edge of the black holes. No,
it comes from statistical and thermal physics. It's come from
thinking about black holes as big objects made of many particles,
and thinking about them statistically, sort of the same way
we think about like temperature and pressure. For a gas
pressure doesn't make any sense, It doesn't have a meaning
for an individual particle. It's a property only of a gas.
(08:33):
So this is the way that Hawking derived this concept
of a temperature and entropy for a black hole. He
invented this field of black hole thermodynamics, and from it
came this concept of Hawking radiation. But we don't have
a microscopic understanding of what's actually happening at the particle level.
But we do have some not terrible kind of hand
(08:57):
wavy descriptions for how Hawking radiation might work. Now, they
don't actually work theoretically on the quantum level if you
try to do these calculations, but they're a good way
to sort of guide your thinking for what might be
happening and help you to think about it. Okay, so
what is our understanding of Hawking radiation at the microscopic level.
So the space near a black hole, of course has
(09:20):
energy in it. All of space has energy in it
because space is filled with quantum fields and those fields
can't relax all the way down to zero, and sometimes
that energy in the field turns into a particle or
a particle and an antiparticle. So this happens all the time.
Things turn into an electron and apositron, and then they
annihilate back and they go back into the field. So
(09:41):
this is going on all the times, this frothing at
the quantum level, even around black holes. Now, when this
happens in the vicinity of a black hole, sometimes these
particles get a little extra boost of energy because there
is more energy around the black hole. There's the gravitational
energy of the black hole. And this is the wonky
part because we don't really understand how gravity interacts with particles.
(10:05):
We can't do experiments to see the gravitational effect on
particles because particles have almost no mass and gravity is
super nuber weak, so we haven't been able to do
these experiments. But anyway, imagine that somehow this particle antiparticle
pair gets extra energy because of the gravitational field of
the black hole. Now, one of these particles happens to
(10:28):
leave the area of the black hole. They were created
outside the event horizon, so that's cool. The other one
falls back into the black hole. Let's think first about
the one that leaves. What happens to it, Well, it
flies off into the universe. Maybe it's an electron, Maybe
it's a positron. Maybe it's a top cork, maybe it's
a gluon. It can be any kind of particle because
(10:49):
the quantum field can fluctuate into any kind of particle.
There are some different probabilities based on the masses, but
that doesn't really matter. But that particle leaves and it
takes with it some energy. Where did that energy come from?
Part of it came just from the quantum field, but
part of it also came from the gravitational energy of
the black hole. And if you take the gravitational energy,
(11:11):
you are decreasing the mass of the black hole. Now
you might be thinking, hold on a second, how does
the mass leave the black hole? This particle was never
in the black hole, right, that's true, But remember the
mass of the black hole is not like the amount
of stuff in the black hole. It's like a meter
that tells you how much energy is stored in the
(11:32):
black hole. Doesn't matter what the form of that energy is.
It can be photons, it can be protons, it can
be something else super duper weird. It can be a
singularity that has no like state of matter we can
think about or calculate. The mass of the black hole
comes from the energy stored within it. So if you
remove energy from the black hole, you reduce its mass.
(11:53):
You can reduce the mass of a black hole without
carrying a particle from inside the event horizon to outside
the event horizon. And you might be thinking, hold on
a second, that's crazy. I thought black holes can never
release information, they could never lose anything. And it's true
that nothing can leave if it's inside the event horizon.
No information can escape. However, the black hole's energy goes
(12:17):
beyond the edge of the event horizon. It's gravitational influence
does not stop at the event horizon. The event horizon
is just a place after which all of your paths
now point towards the center of the black hole. It's
not the edge of the black hole's influence on the universe,
and that influence can extend to things created outside the
event horizon, and it can lose that energy once it's
(12:41):
donated it to those particles, and when it loses that energy,
it loses some mass. All right. So now we have
a sort of hand wavy understanding of how hawking radiation
might work at the microscopic level. Let's get to the question.
The question was about the particle that goes into the
black hole, not the one that escapes, and it was asking,
(13:01):
if the particle goes into the black hole, doesn't it
need to find something to annihilate with the sort of
contribute back its energy to the black hole. And if
black holes are mostly dark matter, then how can they
do that because it can't interact with dark matter. All right,
So a lot of things to talk about there. First
of all, we don't know how much dark matter is
(13:22):
in black holes. I've said on the podcast, it's almost
certain that there is some, and that's true. But remember
that dark matter has a harder time falling into black
holes because it can't get rid of its angular momentum
like other kinds of matter. It can spin around a
black hole, but other kinds of matter can lose their
angular momentum by radiating off energy, for example, or bumping
(13:43):
into each other. These kinds of interactions are crucial for
losing your angular momentum and falling into the black hole,
falling out of orbit and falling into the black hole.
Dark matter can't do that, so it stays fluffy. And
so we think that there is dark matter in black holes,
we don't really know how much. It may not be
that it's dominated by dark matter, but even still, let's
(14:03):
imagine that the black hole is filled with dark matter.
What happens to this particle that falls into the black hole, Well,
it doesn't actually need to annihilate with anything to contribute
to the mass of the black hole. Remember, the mass
of the black holes just a measure of how much
energy is stored inside it. It's not necessary for that
particle to annihilate with something else and return its energy.
(14:26):
It already has returned its energy. Everything that's in the
vicinity of the black hole contributes to the gravitational system
and therefore to the mass of the black hole. If
particles inside the black hole change from photons to particle
antiparticle pairs, it has no effect on the black hole's mass.
So if there is dark matter inside black holes, it
(14:46):
doesn't affect this Hawking radiation alright. So the things to
remember about hawking radiation are number one, that we only
have a hand wavy description of the microscopic effects. We
don't really understand how it works. Our understanding of hawking
radiation is at the level of statistical physics, talking about many,
many particles and averaging over lots of quantum details that
(15:08):
we do not yet understand. And that hawking radiation happens
outside the black hole, borrowing some of the gravitational energy
from the black hole and carrying it off with it,
because you can interact with the black hole without actually
falling into it, and that means that it's possible to
steal a little bit of its energy and therefore decrease
(15:29):
its mass. And that's sort of our understanding of Hawking
radiation and how black holes can't evaporate. All right. Thank
you for that oh wonderful question, and thank you for
thinking deeply about how black holes work and how they evaporate,
and what might be inside them and what's going on
inside the black holes. They are one of my favorite
mysteries because they potentially contain the answers just so many
(15:51):
basic questions about how the universe works, what happens to
quantum particles when gravity gets really really strong, and the
gravitational effects and quantum effects both become important. We have
almost nowhere in the universe we can probe quantum gravity
because it's so hard to study. But the center of
black holes is that place. Unfortunately, of course, we can't
(16:13):
see what's inside them, all right, So thanks to that question,
I have more questions. I want to get to but
first let's take a quick break. All right, we're back
(16:34):
in today. It's just me, Daniel. I'm a particle of
physicists by day and by night I like to answer
physics questions from the public, and today we are answering
questions sent in by listeners. We thought about something or
read something and wanted to hear it explained. And today's
episode is focused on the topic of radiation. We talked
about radiation from black holes, and here's a question from
(16:56):
listeners about another kind of potential radiation. Low Daniel Horrey,
this is a Mario from Los Angeles. While I was
listening to your show, I heard a commercial about five
G and I got curious because there's a lot of
conspiracy theories about the pandemic and five G. I was
hoping you guys could explain the effects of five G
have on our society given informed an opinion about the
(17:16):
conspiracy theories. Thank you. Okay, So this is a really
interesting question and one that actually a few people have
written to us about. So I thought it'd be interesting
to sort of take the physics point of view. What
do we know about five G networks? What are they,
how do they work, what's the physics of five G
and how it interacts with a human body, and then
you'll have everything you need to make up your own
(17:38):
mind about whether or not five G is a good idea. Alright,
so first of all, what is five G. Five G
means fifth generation cell phone networks. People have been upgrading
and improving our cell phone network to make them faster
and more reliable, etcetera. And now they have the fifth
generation which is now being installed. Five G is a thing.
(17:59):
It exists, it's out there in patches in our world.
It's not complete, it's not everywhere. They're still putting it together,
so it's sort of in its embryonic phase. And it's
an exciting technology because potentially it could deliver data to
your devices a hundred or more times faster than the
four gene networks, and so that would allow a lot
of things to happen. You can have a screen on
(18:21):
the door to your refrigerator to let's use stream movies
while you're deciding what to eat. You can have everything connecting.
You can just send a lot more data everywhere. So
if you're excited about data, then you should be excited
about five gene networks. So what's different between five G
and four G? Right, the fourth generation of network and
what makes people so interested and excited and concerned about it.
(18:44):
While there are a couple of differences about five G,
there's some sort of smaller ones, like the way they
organize the data to make it faster, in the way
they route it from tower to tower, But the major
differences are one that the antennas are directional. So an
antenna is just a bunch of electrons with going in
a conducting rod that generates electromagnetic fields, and often these
(19:04):
antennas broadcast in every direction simultaneously, so then the power
of the radiation, the intensity of the signal decreases as
you get further away from the antenna, but sort of
the same way every direction. These five G antennas are directional.
They can be focused in certain directions to provide like
longer range connections in certain directions and to black out
(19:26):
other directions. And this way you can sort of like
more intelligently decide where you want your coverage. So that's
number one, they have these directional antennas. Number two, and
this is probably the big one, is that they're using
a different frequency to communicate the wavelength of these signals
is something like ten millimeters. The frequency is like in
the range of twenty to fifty giga hurts. And this
(19:49):
is interesting, and this is new because it's ten times
higher frequency shorter wavelength than have existed in cell phones before.
It's not the first time we've seen technology that emits
radiation in this wavelength or frequency spectrum. It's the same
sort of wavelength this is used in those airport scanners
when you go to the airport and they try to
(20:10):
figure out if you have something in your pocket. But
these are much lower power than those airport scanners. On
the other hand, they're kind of on all the time,
so they're sort of blanketing the world with this radiation.
And the question is about the long term exposure to
this wavelength of radiation, and that's where I think the
concern arises. And you may have heard some conspiracy theories
(20:30):
about how this has created the pandemic or responded to
the pandemic, and that, of course, is all just bonkers.
There's no connection between five G and the pandemic. There
are no microchips inside the vaccines. All that stuff is
just fearmongering nonsense. There are some interesting physics questions about
five G, and some interesting medical questions about the impact
(20:53):
of five G on the human body, and some interesting
policy questions about how to roll out of technology. How
many st you really need to have done before you
take a risk and roll out something new. That's all fascinating,
but let's push aside for now the crazy conspiracy theories
connect to the pandemic. We're in seeing lizard people using
five G to control your minds, And let's just talk
(21:14):
about the physics. So I said radiation, and I talked
about the intensity of it. Does that mean that these
things are like radioactive, that you're basically living next to
a nuclear power plant? No, no, no, Remember that radiation
is a very very broad term. It includes any sort
of wave or particle which transmits energy, including yes, radioactivity
(21:35):
from nuclear power plants. But that's not what we're talking
about today. We're talking about the kind of radiation that's
just photons, right, just a kind of light electro magnetic radiation,
which is a very very broad term. But all of
it is just a different kind of photon, and those
photons are different based on their frequency, based on the
wavelength of the photon, and different wavelength photons we give
(21:59):
different names, from very long wavelength photons, which are like
radio waves or infrared waves, up to visible light, of course,
which is just photons of a certain frequency that hits
your eyes and your brain knows how to interpret. Up
to ultra violet light, which has a frequency higher than
you can see, all the way up to X rays
(22:19):
and gamma rays. It's all part of one continuous spectrum.
The difference between a gamma ray and a photon that
makes up a radio wave is just the wavelength of
that photon, and all these photons can be used to
encode information. So we use electromagnetic radiation as a way
to pass information around, and you can think of it
(22:40):
as waves, right. We think about radio waves as waves
washing over the earth surface. TV antennas and all that
kind of stuff send electromagnetic waves, and you can think
about it as waves. That makes perfect sense. But it's
also important to remember that it's actually made of photons.
It's made of individual particles, and that's important because the
(23:00):
energy of the individual photons depends on the wavelength of
the radiation. So when we say higher frequency, we mean
there's more energy per photon, so you v photons have
more energy in them than radio wave photons. Gamma ray
photons have even more energy in them. X ray photons
(23:20):
have a lot of energy in them, more than visible
light photons. And it's broken up into these pieces, right.
You can't have half a photon or one and a
half photons. If you have a beam of light in
the X ray part of the spectrum, then each of
those photons has a lot of energy. If you have
a beam of light in the infrared, than each of
those photons has less energy. And that turns out to
(23:43):
be really important because when the photon hits your body,
it's the energy of that individual photon that determines whether
or not it can ionize something, whether or not it
can kick an electron, for example, out of an atom,
or it can break one of those bonds. And the
most damaging thing radiation can do is ionized parts of
your body. When it does this, it does things like
(24:04):
break up DNA molecules. It acts like a tiny little
bullet that shoots through your body and breaks things. So
ionizing radiation is very, very dangerous, and that's why it's
important to reduce your exposure to ionizing radiation. Now, things
like uranium and plutonium give off ionizing radiation, which is
very dangerous, and some forms of electromagnetic radiation can have
(24:27):
enough energy to ionize. The threshold for ionizing radiation is
a little bit fuzzy, depends on the material, etcetera. But
it's on the order of magnitude of about ten e
v per photon. This is like the binding energy of molecules.
And in order to have that much energy of photon
has to be in the ultra violet. That's why ultra
violet radiation u V rays are bad for you. U
(24:49):
V does cause cancer, and that's what you're blocking when
you're putting on sunscreen, and that u V light can
pass through clouds, which is how you can get a
sunburn on a cloudy day. So visible light and everything
with a wavelength lower than that, it's not ionizing. It
can't cause ionization in your body, and so it's much
much safer. Now. Five G is well below the wavelength
(25:12):
of even visible light. It's below the infrared. So from
the point of view of ionization, the most dangerous thing
that radiation can do. Five G is not a concern. Yes,
it does have a higher wavelength, and previous generations of
cell phones, but it's well below the energy needed to
do any damage from an ionizing point of view. But
(25:33):
that's not the only way that radiation can damage you.
Ionization is not the only thing that it can do.
For example, it can deposit energy in your body even
without actually ionizing. I mean, this is what an oven does.
Right when you cook a turkey in your oven, you're
using infrared photons. You're using the heat of the oven
to cook that turkey, And yeah, it certainly does damage
(25:56):
the turkey. And so you can hurt people with a
high intensity of low energy radiation. Right here, we're talking
about the intensity and microwave oven uses microwave radiation, which
is much much longer in wavelength than ultra violet photons.
But it's a very high intensity, and so it can
(26:16):
deposit a lot of energy and eventually it can hurt you.
So this is the area to focus on from a
sort of physics and medical point of view. Can being
exposed to a large amount of five G signals do
some damage to the human body. Well, it turns out
that humans have a sort of built in shield to
a lot of this stuff. Most of these photons will
actually scatter off of your skin. Your skin is like
(26:39):
a shield that will reflect a lot of this energy.
The upper layers of your skin are opaque to this
kind of photon, so most of it won't even enter
your body. There were some very early studies that showed
the amount of damage done to tissue based on the
frequency and showed the five G was in a range
that did more damage, but it neglected to take new
(27:00):
count the fact that most of that five G radiation
won't even get into your body. But the fact remains
that this is a kind of electromagnetic radiation where it's
long term exposure has not been studied on the public.
We haven't based people and the kinds of radiation that
five G will generate for long periods and seeing what
would happen. Right, So we just don't know. That doesn't
(27:21):
mean we don't have a good guess. We understand the
physics of it. We think that it's too low energy
to do any ionization damage. We think that the skin
is opaque to it and will reflect most of it,
and so we think we can do the calculations and
it seems totally safe, but we don't have direct evidence.
And the folks that are citing studies that show that
(27:42):
there's no connection between for example, cell phone towers and
cancer are missing the point a little bit because those
cell phone towers are using a different frequency than five G.
So we don't actually have direct data that shows that
five G is safe because it was just invented, right,
And so what can we do here? Science can say
we don't see a reason why it would be dangerous.
(28:04):
We think it will be safe. We do not have
direct proof, so we can't conclusively say it's safe. We
can't point to studies that prove that it's safe. We
can argue and we can make reasonable points that suggest
that it will be safe. But in the end, it's
a question for policy makers when do you make a
decision for how to roll out a new technology which
could have lots of benefits for the public, but also
(28:26):
every new technology does have some inherent dangers, and in
the end, sometimes policy makers do have to make these
very difficult decisions knowing they could help people, but they
could also potentially hurt people. So that's not something I'm
going to comment on because I'm not a policy maker,
but I think that the policymakers should at least be
informed by the science, and I hope that you guys
out there understand the signs of five G. It is
(28:49):
a new technology with higher frequency photons, not high enough
frequency to do ionizing damage, but the impact of this
frequency radiation and very low intensities, how has not been
studied on the general public. That doesn't mean that it's
caused the pandemic or that it's something that you should
worry about. Read more about it, think about it right
to your congress people or representatives, or your president or whoever,
(29:12):
if you have a deep and passionate opinion about how
to balance this question of technology versus safety. All Right,
I want to answer another question, but first let's take
another break. All right, we're back and I'm answering questions
(29:38):
from listeners. We had a question about black holes and
hawking radiation. We had a question about wireless cell phone
towers and the radiation they emit. And now we have
a question about wireless charging. Hi, Daniel, and I was
wondering how wireless charging devices work. I don't understand how
the battery is charged without a visible input into the device.
(30:03):
It's baffling to me. It's like magic. Thanks all right,
thank you for this super fun question. Sometimes physics is baffling.
It defies our intuition, but you know, the universe works,
The universe follows rules. There's always a way to understand
what we see and then sometimes to use that understanding
to build awesome new technology like wireless charging. And your
(30:27):
intuition is that things need a wire because the stuff
around you uses wires. Right, either you plug it into
the wall or you connect it with a battery, because
you're used to a certain kind of way of transmitting energy.
You have energy inside a battery or energy coming in
the wires, and that's in the form of electrical energy,
and those electrons zip along and they deposit that energy
(30:49):
into your device, your phone or your camera, or your
laptop or your blender or whatever. And that certainly is
one way to send electromagnetic energy from one device to
another by using the wire, which is essentially just a
conductor where the electrons can bump into each other and
pass that energy along. However, there are lots of ways
to transmit energy, and you can transmit energy wirelessly, right.
(31:13):
What is a flashlight. A flashlight is a beam of photons.
Those photons have energy. What is a laser A laser
concertainly transmit energy, you can use it to heat something
up from a distance, right, and those photons can fly
through space, even through a vacuum. So conceptually, from a
sort of physics point of view, we understand how it's
(31:33):
possible for energy to start in one place and get
to another place without having a physical connection a wire, right,
even across the vacuum of quote unquote empty space. But
that doesn't tell us how wireless chargers actually work. How
do they get the energy from one device to the
other without the two actually being connected. There's not some
(31:55):
tiny series of lasers in their zapping energy from one
to the other. You certainly don't want your blender to
be zapped with lasers. So how does it actually work.
The first thing to understand is the whole system is
not wireless. It's just like one step there that's wireless.
Usually you have like a base which is plugged into
the wall, and then you can put your phone on
top of that base. It sits on the base and
(32:17):
it draws power from the base. And so it's that
step that we're gonna try to understand. How can you
get energy from the base which is plugged into the
wall and getting energy eventually from your power plant, how
does it get from that base and into your phone.
So this comes from the magic and the beauty of
electro magnetism. And to understand how this works, we need
to remember that electricity and magnetism feel like two different things, right.
(32:42):
Electricity is lightning bolts and electrons, and magnetism is like
fridge magnets and levitating trains. But they are actually two
parts of the same thing. Maxwell, the Scottish clerk a
hundred and fifty years ago, realized that there's a deep
symmetry between electricity and magnetism. And you note us this
because he noticed that electricity can cause magnetic field to
(33:03):
magnetic fields can cause currents, and so that's exactly how
it happens. We have two parts of Maxwell's equations working together.
So the first part is that when you have an
electric current that creates a magnetic field. If you've ever
seen an electro magnet, you know this is true. You
turn on the current, it goes through coils and those
(33:24):
coils create a magnetic field. And every electric engine, for example,
has this property inside it. When you turn on the engine,
what you're doing is turning on electro magnets inside the engine,
which are using the magnet to sort of tug on
another part of the engine and get it to move.
So the first step is to use currents inside the
base station to create a powerful magnetic field. That magnetic field,
(33:49):
in turn can cause electrical currents because another part of
Maxwell's equations tells us that varying magnetic fields caused electrical currents. Right,
So what happens to the base station is you have
this current which is going on and off, creating magnetic
fields which are on and off, and those magnetic fields
then induce a current inside your phone. So inside the
(34:12):
phone there has to be some loop, or inside whatever
device you're trying to charge, there has to be some loop,
and the magnetic fields then induce a current inside that loop.
So you have a loop inside the base station where
you create a current using power from the wall. That
current inside the loop creates a magnetic field, and that
magnetic field then creates a current inside a loop of
(34:32):
wire in the thing that you want to charge. And
so this is a way to transmit the energy from
the base station to the phone or whatever it is
that you're trying to charge without actually having to have
a wire between them. Is essension, like using a magnetic wire.
And this only works because there is this symmetry between
electricity and magnetism, because currents cause magnetic fields, which cause currents.
(34:58):
And the other awesome thing about a symmetry is that
it's the reason that we can see anything. What is light?
What is a photon? It's a ripple in the electro
magnetic field, not the electrical field, not the magnetic field,
but the electro magnetic field. And that exists because varying
electric fields caused magnetic fields, which caused varying electric fields.
(35:20):
So what a photon actually is is a field that
slashing back and forth between the electric and the magnetic field.
That's what allows it to like pass through the vacuum
of space. It supports itself, it propagates itself by going
back and forth from electro to magnetic fields. And this
was the beautiful inside of Maxwell. He saw these equations
(35:41):
and they put them together. He thought, oh, my gosh,
light looks just like a wave that's slashing back and
forth and moving at some speed. And he did the calculation.
He's like, oh, look, it moves at the speed of light.
So that was a beautiful moment, sort of in theoretical physics,
putting these two pieces together, understanding the symmetry between electric
and magnetic field. And it's that same insight that allows
(36:02):
us to do inductive powering, to use magnetic induction to
take a coil of current and transfer that energy into
another coil. Now, this is fascinating if people have done
a lot of studies to see, like how far can
it work. You're probably most familiar with charging stations at
Starbucks where you will get charged from this wireless charging station. Now,
(36:23):
the larger the coil inside the base station, the longer
the wavelength of this radiation essentially, and the larger the
distance that that power can charge. There was a record
set in two thousand and seven where somebody was able
to charge something two meters away. That's pretty awesome, Right,
two meters away is a good distance, not enough that
(36:44):
you can like drive around town and keep your phone
charge from your house, but it's pretty cool, and it's
the kind of thing where people are making strides and
eventually there'll be a breakthrough and we'll be able to
send power at even greater distances. And you know, your
phone is not the only example of this technology. G
if anybody out there has an inductive range. It's the
kind with coils in it. But those coils don't feel
(37:06):
hot because they're not transmitting the energy by making themselves
glow really really hot, like the elements inside your oven,
which would be giving off infrared radiation. Instead, they're creating
magnetic fields, which then cause currents inside a pan that
you put on top of the stove, so the pan
gets hot, but the surface of the stove itself is
(37:27):
not hot because there's no infrared heat passing directly from
inside the range to the pan. And then you have
this coil inside the range, and that coil has a
lot of electricity in it, which is creating a magnetic field,
which is creating a current inside your pot, which then
turns into heat of the pot. So it's able to
transmit this energy and heat of the pot without actually
(37:49):
heating up the stuff in between, which is pretty awesome
and it means that it's harder to burn yourself. So
thanks very much for asking that super fun question about
this cool technology. It does seem like magic, but it's
actually something that we can understand, and that's the beauty
of the universe that amazingly it seems like no matter
what happens out there, if you think about it carefully,
(38:10):
if we put our collective heads together, we can figure
it out. And so, even though there are so many
mysteries remaining about the nature of the universe and what's
going on inside black holes, and how the universe started
and what is everything made out of, at the smallest,
tiniest level, all these questions are just the possibilities for
new discoveries, the possibility to reveal something new about the
(38:31):
universe that we didn't know that would blow the minds
of our grandparents. It means that one day our grandchildren
will make these discoveries and will blow our minds. So
until then, keep thinking about it, keep asking questions, and
send us all of your questions. We love to hear
your thoughts. Thanks very much. Tune in next time. Thanks
(38:59):
for listening. Remember that Daniel and Jorge Explain the Universe
is a production of I Heart Radio. For more podcast
from my Heart Radio, visit the I Heart Radio Apple
Apple Podcasts, or wherever you listen to your favorite shows.
H
The world around you is like an amazing mirage. That
rock you see over there, it's not actually one object,
but a collection of ten to the twenty five particles,
all shaking and buzzing and wiggling together. That star you
see in the sky, those are photons generated from zillions
(00:28):
of kilograms of hot plasma that traveled billions of light
years before hitting your retina. That chair that's holding you up,
that's not solid. It's actually a web of atoms linked
together by electromagnetic forces. Physics gives you a way to
peel back a layer of reality and figure out what's
happening underneath, to see the world in a new way
(00:50):
by understanding its nature at the microscopic level and seeing
how all the incredible complexity in the insanity in our
universe arises from the simple interactions of a small number
of pieces. It's bonkers, but it's beautiful. Hi. I'm Daniel,
(01:22):
I'm a particle physicist, and I'm in love with the
insanity of our universe. And welcome to our podcast Daniel
and Jorge Explain the Universe, a production of My Heart
Radio in which we take a mental journey through the cosmos.
We think about how everything out there works. We try
to understand the craziness of neutron stars, of black holes evaporating,
(01:46):
the tiny, little, buzzing particles that make it all up.
We try to take the whole universe and wrap it
up so that you can understand it, or at least
understand a little piece of it. Because the universe is
not something that is understood. It remains an enormous cosmic mystery.
Though we have peeled back layers of reality to see
(02:08):
that most of what we are looking at is made
of elements, and those elements are made of even smaller particles,
which are made of even smaller particles. We have dug
deep into the nature of reality, but our questions are
not yet answered. We need to understand, and we have
not yet understood, the remain enormous mysteries about the nature
of the universe. What is most of the matter out
(02:31):
there in the universe? What is driving the acceleration of
the cosmic expansion of the universe. We have really basic
questions about how things work. But those questions are not failings.
They're not a disappointment in science. They are exciting opportunities.
They are the threads that we will pull on to
help us reveal the nature of the universe. They are
(02:53):
the clues that will lead us to incredible, mind blowing
discoveries about the nature of the cosmos, just the way
that our journey through physics so far has revealed so
many times that the universe is not the way that
we thought it was, since our intuition built up from
the times that we climbed down from the trees and
walked around on two feet and tried to understand this
(03:14):
world around us, that that intuition has often led us astray,
and that when we follow the science, when we carefully
build up knowledge by asking and answering questions, is when
we reveal the true nature of the universe. And it's
crazy and it's weird, and it violates our intuitions, but
it's still beautiful and it's our universe. And that's why
(03:36):
on our podcast we love to celebrate questions, not just
questions asked by scientists working at the forefront of knowledge
peering out into the depths of the universe, but your questions,
our questions, everybody's questions, Because if you wonder about the
nature of the universe, if you yearn to understand the
truth about reality. Then you are a scientist, then you
(03:57):
are asking questions. Then you would be surprised to discover
how many of your questions are the same questions being
asked by scientists. So don't be embarrassed to ask your questions,
ask them out loud, talk to people about them, try
to find the answers, and if you can't, send them
to us, because we love answering your questions. Everybody out
(04:18):
there who has thought about a topic and not quite
understood it, or heard an explanation about something weird and
crazy and it didn't really sink in, please write to us.
We will answer your questions. We're available online. We answer
emails to questions at Daniel and Jorge dot com. We
respond on Twitter at Daniel and Jorge, and sometimes we'll
(04:40):
take some of these questions and feature them on the
podcast and so on. Today's program will be answering listener
questions about Hawking, radiation, five G networks, and wireless charging.
As you might have gathered, my co host friend and
(05:01):
collaborator Jorge him is not around today, so I'm taking
this opportunity to dig into our backlog of wonderful, wonderful
questions asked to us by listeners. So I'll be digging
into a few questions from listeners, and you have lots
of opportunities to get your questions answers. You can email us,
you can tweet us. You can also come to my
(05:22):
public office hours. I hang out on zoom and answer
questions from anybody out there who's interested in physics and
wants to understand the universe. Check out my website sites
dot U, c I, dot E, d U slash Daniel
for all the details about the next upcoming public office hours.
All right, so let's dig into it and start answering
(05:42):
listener questions. This first one is an awesome question about
hawking radiation, black holes, and dark matter. Hello Dan, My
question is about talking radiation and the operation of BLAT. So,
if there is there's matter inside my cote, what had
it been necessary for hawking radiation to interact with the
(06:03):
dark matter in order to produce like holes completely. This
is such a fun question because it gives me a
little glimpse into what's going on in somebody's mind. Somebody's
thinking about black holes and hawking radiation and wondering how
that happens, and all of a sudden they run into
a wall. They think a whole lot of a second,
this doesn't make sense. How can the products of hawking
(06:23):
radiation annihilate with the dark matter inside the black holes?
And so they come to that point they don't understand it,
and that's when they reach out. And I love seeing
people do that, taking two ideas and trying to fit
them together into one understanding, because that's what we do
in physics, right We want a single understanding that explains everything.
You can't have one explanation for this thing and a
(06:45):
totally different explanation for that. We want a complete, holistic
view of the universe. So kudos to you for asking
this question. But before I dive into the details of
dark matter and black holes and hawking radiation, let's back
up and make sure we understand the basics of what's
going on in hawking radiation, because I think there might
be a small misunderstanding in the process, which is actually
(07:07):
leading to the core of this question. The first thing
you should understand about hawking radiation is that we do
not have a good microscopic understanding of how it works.
You know, we like to look at the world and
peel it back and understand how it works. At the
particle level and sometimes work back up from the particle
level to the macroscopic and say, okay, we understand this
(07:29):
temperature is just the buzzing of particles whizzing around, or
an electrical conductivity comes from how electrons are filling their orbitals, etcetera, etcetera.
But that's not something we have yet for Hawking radiation
because it relies on two things that don't play well together,
tiny little quantum particles which obey the rules of quantum
(07:49):
mechanics and gravity, and gravity and quantum mechanics don't play
very nicely together. We do not understand gravitational effects on
individual quantum part nicles. That would require a theory of
quantum gravity, which we don't have. So Hawking radiation actually
doesn't come from a microscopic understanding of what happens to
(08:10):
quantum particles near the edge of the black holes. No,
it comes from statistical and thermal physics. It's come from
thinking about black holes as big objects made of many particles,
and thinking about them statistically, sort of the same way
we think about like temperature and pressure. For a gas
pressure doesn't make any sense, It doesn't have a meaning
for an individual particle. It's a property only of a gas.
(08:33):
So this is the way that Hawking derived this concept
of a temperature and entropy for a black hole. He
invented this field of black hole thermodynamics, and from it
came this concept of Hawking radiation. But we don't have
a microscopic understanding of what's actually happening at the particle level.
But we do have some not terrible kind of hand
(08:57):
wavy descriptions for how Hawking radiation might work. Now, they
don't actually work theoretically on the quantum level if you
try to do these calculations, but they're a good way
to sort of guide your thinking for what might be
happening and help you to think about it. Okay, so
what is our understanding of Hawking radiation at the microscopic level.
So the space near a black hole, of course has
(09:20):
energy in it. All of space has energy in it
because space is filled with quantum fields and those fields
can't relax all the way down to zero, and sometimes
that energy in the field turns into a particle or
a particle and an antiparticle. So this happens all the time.
Things turn into an electron and apositron, and then they
annihilate back and they go back into the field. So
(09:41):
this is going on all the times, this frothing at
the quantum level, even around black holes. Now, when this
happens in the vicinity of a black hole, sometimes these
particles get a little extra boost of energy because there
is more energy around the black hole. There's the gravitational
energy of the black hole. And this is the wonky
part because we don't really understand how gravity interacts with particles.
(10:05):
We can't do experiments to see the gravitational effect on
particles because particles have almost no mass and gravity is
super nuber weak, so we haven't been able to do
these experiments. But anyway, imagine that somehow this particle antiparticle
pair gets extra energy because of the gravitational field of
the black hole. Now, one of these particles happens to
(10:28):
leave the area of the black hole. They were created
outside the event horizon, so that's cool. The other one
falls back into the black hole. Let's think first about
the one that leaves. What happens to it, Well, it
flies off into the universe. Maybe it's an electron, Maybe
it's a positron. Maybe it's a top cork, maybe it's
a gluon. It can be any kind of particle because
(10:49):
the quantum field can fluctuate into any kind of particle.
There are some different probabilities based on the masses, but
that doesn't really matter. But that particle leaves and it
takes with it some energy. Where did that energy come from?
Part of it came just from the quantum field, but
part of it also came from the gravitational energy of
the black hole. And if you take the gravitational energy,
(11:11):
you are decreasing the mass of the black hole. Now
you might be thinking, hold on a second, how does
the mass leave the black hole? This particle was never
in the black hole, right, that's true, But remember the
mass of the black hole is not like the amount
of stuff in the black hole. It's like a meter
that tells you how much energy is stored in the
(11:32):
black hole. Doesn't matter what the form of that energy is.
It can be photons, it can be protons, it can
be something else super duper weird. It can be a
singularity that has no like state of matter we can
think about or calculate. The mass of the black hole
comes from the energy stored within it. So if you
remove energy from the black hole, you reduce its mass.
(11:53):
You can reduce the mass of a black hole without
carrying a particle from inside the event horizon to outside
the event horizon. And you might be thinking, hold on
a second, that's crazy. I thought black holes can never
release information, they could never lose anything. And it's true
that nothing can leave if it's inside the event horizon.
No information can escape. However, the black hole's energy goes
(12:17):
beyond the edge of the event horizon. It's gravitational influence
does not stop at the event horizon. The event horizon
is just a place after which all of your paths
now point towards the center of the black hole. It's
not the edge of the black hole's influence on the universe,
and that influence can extend to things created outside the
event horizon, and it can lose that energy once it's
(12:41):
donated it to those particles, and when it loses that energy,
it loses some mass. All right. So now we have
a sort of hand wavy understanding of how hawking radiation
might work at the microscopic level. Let's get to the question.
The question was about the particle that goes into the
black hole, not the one that escapes, and it was asking,
(13:01):
if the particle goes into the black hole, doesn't it
need to find something to annihilate with the sort of
contribute back its energy to the black hole. And if
black holes are mostly dark matter, then how can they
do that because it can't interact with dark matter. All right,
So a lot of things to talk about there. First
of all, we don't know how much dark matter is
(13:22):
in black holes. I've said on the podcast, it's almost
certain that there is some, and that's true. But remember
that dark matter has a harder time falling into black
holes because it can't get rid of its angular momentum
like other kinds of matter. It can spin around a
black hole, but other kinds of matter can lose their
angular momentum by radiating off energy, for example, or bumping
(13:43):
into each other. These kinds of interactions are crucial for
losing your angular momentum and falling into the black hole,
falling out of orbit and falling into the black hole.
Dark matter can't do that, so it stays fluffy. And
so we think that there is dark matter in black holes,
we don't really know how much. It may not be
that it's dominated by dark matter, but even still, let's
(14:03):
imagine that the black hole is filled with dark matter.
What happens to this particle that falls into the black hole, Well,
it doesn't actually need to annihilate with anything to contribute
to the mass of the black hole. Remember, the mass
of the black holes just a measure of how much
energy is stored inside it. It's not necessary for that
particle to annihilate with something else and return its energy.
(14:26):
It already has returned its energy. Everything that's in the
vicinity of the black hole contributes to the gravitational system
and therefore to the mass of the black hole. If
particles inside the black hole change from photons to particle
antiparticle pairs, it has no effect on the black hole's mass.
So if there is dark matter inside black holes, it
(14:46):
doesn't affect this Hawking radiation alright. So the things to
remember about hawking radiation are number one, that we only
have a hand wavy description of the microscopic effects. We
don't really understand how it works. Our understanding of hawking
radiation is at the level of statistical physics, talking about many,
many particles and averaging over lots of quantum details that
(15:08):
we do not yet understand. And that hawking radiation happens
outside the black hole, borrowing some of the gravitational energy
from the black hole and carrying it off with it,
because you can interact with the black hole without actually
falling into it, and that means that it's possible to
steal a little bit of its energy and therefore decrease
(15:29):
its mass. And that's sort of our understanding of Hawking
radiation and how black holes can't evaporate. All right. Thank
you for that oh wonderful question, and thank you for
thinking deeply about how black holes work and how they evaporate,
and what might be inside them and what's going on
inside the black holes. They are one of my favorite
mysteries because they potentially contain the answers just so many
(15:51):
basic questions about how the universe works, what happens to
quantum particles when gravity gets really really strong, and the
gravitational effects and quantum effects both become important. We have
almost nowhere in the universe we can probe quantum gravity
because it's so hard to study. But the center of
black holes is that place. Unfortunately, of course, we can't
(16:13):
see what's inside them, all right, So thanks to that question,
I have more questions. I want to get to but
first let's take a quick break. All right, we're back
(16:34):
in today. It's just me, Daniel. I'm a particle of
physicists by day and by night I like to answer
physics questions from the public, and today we are answering
questions sent in by listeners. We thought about something or
read something and wanted to hear it explained. And today's
episode is focused on the topic of radiation. We talked
about radiation from black holes, and here's a question from
(16:56):
listeners about another kind of potential radiation. Low Daniel Horrey,
this is a Mario from Los Angeles. While I was
listening to your show, I heard a commercial about five
G and I got curious because there's a lot of
conspiracy theories about the pandemic and five G. I was
hoping you guys could explain the effects of five G
have on our society given informed an opinion about the
(17:16):
conspiracy theories. Thank you. Okay, So this is a really
interesting question and one that actually a few people have
written to us about. So I thought it'd be interesting
to sort of take the physics point of view. What
do we know about five G networks? What are they,
how do they work, what's the physics of five G
and how it interacts with a human body, and then
you'll have everything you need to make up your own
(17:38):
mind about whether or not five G is a good idea. Alright,
so first of all, what is five G. Five G
means fifth generation cell phone networks. People have been upgrading
and improving our cell phone network to make them faster
and more reliable, etcetera. And now they have the fifth
generation which is now being installed. Five G is a thing.
(17:59):
It exists, it's out there in patches in our world.
It's not complete, it's not everywhere. They're still putting it together,
so it's sort of in its embryonic phase. And it's
an exciting technology because potentially it could deliver data to
your devices a hundred or more times faster than the
four gene networks, and so that would allow a lot
of things to happen. You can have a screen on
(18:21):
the door to your refrigerator to let's use stream movies
while you're deciding what to eat. You can have everything connecting.
You can just send a lot more data everywhere. So
if you're excited about data, then you should be excited
about five gene networks. So what's different between five G
and four G? Right, the fourth generation of network and
what makes people so interested and excited and concerned about it.
(18:44):
While there are a couple of differences about five G,
there's some sort of smaller ones, like the way they
organize the data to make it faster, in the way
they route it from tower to tower, But the major
differences are one that the antennas are directional. So an
antenna is just a bunch of electrons with going in
a conducting rod that generates electromagnetic fields, and often these
(19:04):
antennas broadcast in every direction simultaneously, so then the power
of the radiation, the intensity of the signal decreases as
you get further away from the antenna, but sort of
the same way every direction. These five G antennas are directional.
They can be focused in certain directions to provide like
longer range connections in certain directions and to black out
(19:26):
other directions. And this way you can sort of like
more intelligently decide where you want your coverage. So that's
number one, they have these directional antennas. Number two, and
this is probably the big one, is that they're using
a different frequency to communicate the wavelength of these signals
is something like ten millimeters. The frequency is like in
the range of twenty to fifty giga hurts. And this
(19:49):
is interesting, and this is new because it's ten times
higher frequency shorter wavelength than have existed in cell phones before.
It's not the first time we've seen technology that emits
radiation in this wavelength or frequency spectrum. It's the same
sort of wavelength this is used in those airport scanners
when you go to the airport and they try to
(20:10):
figure out if you have something in your pocket. But
these are much lower power than those airport scanners. On
the other hand, they're kind of on all the time,
so they're sort of blanketing the world with this radiation.
And the question is about the long term exposure to
this wavelength of radiation, and that's where I think the
concern arises. And you may have heard some conspiracy theories
(20:30):
about how this has created the pandemic or responded to
the pandemic, and that, of course, is all just bonkers.
There's no connection between five G and the pandemic. There
are no microchips inside the vaccines. All that stuff is
just fearmongering nonsense. There are some interesting physics questions about
five G, and some interesting medical questions about the impact
(20:53):
of five G on the human body, and some interesting
policy questions about how to roll out of technology. How
many st you really need to have done before you
take a risk and roll out something new. That's all fascinating,
but let's push aside for now the crazy conspiracy theories
connect to the pandemic. We're in seeing lizard people using
five G to control your minds, And let's just talk
(21:14):
about the physics. So I said radiation, and I talked
about the intensity of it. Does that mean that these
things are like radioactive, that you're basically living next to
a nuclear power plant? No, no, no, Remember that radiation
is a very very broad term. It includes any sort
of wave or particle which transmits energy, including yes, radioactivity
(21:35):
from nuclear power plants. But that's not what we're talking
about today. We're talking about the kind of radiation that's
just photons, right, just a kind of light electro magnetic radiation,
which is a very very broad term. But all of
it is just a different kind of photon, and those
photons are different based on their frequency, based on the
wavelength of the photon, and different wavelength photons we give
(21:59):
different names, from very long wavelength photons, which are like
radio waves or infrared waves, up to visible light, of course,
which is just photons of a certain frequency that hits
your eyes and your brain knows how to interpret. Up
to ultra violet light, which has a frequency higher than
you can see, all the way up to X rays
(22:19):
and gamma rays. It's all part of one continuous spectrum.
The difference between a gamma ray and a photon that
makes up a radio wave is just the wavelength of
that photon, and all these photons can be used to
encode information. So we use electromagnetic radiation as a way
to pass information around, and you can think of it
(22:40):
as waves, right. We think about radio waves as waves
washing over the earth surface. TV antennas and all that
kind of stuff send electromagnetic waves, and you can think
about it as waves. That makes perfect sense. But it's
also important to remember that it's actually made of photons.
It's made of individual particles, and that's important because the
(23:00):
energy of the individual photons depends on the wavelength of
the radiation. So when we say higher frequency, we mean
there's more energy per photon, so you v photons have
more energy in them than radio wave photons. Gamma ray
photons have even more energy in them. X ray photons
(23:20):
have a lot of energy in them, more than visible
light photons. And it's broken up into these pieces, right.
You can't have half a photon or one and a
half photons. If you have a beam of light in
the X ray part of the spectrum, then each of
those photons has a lot of energy. If you have
a beam of light in the infrared, than each of
those photons has less energy. And that turns out to
(23:43):
be really important because when the photon hits your body,
it's the energy of that individual photon that determines whether
or not it can ionize something, whether or not it
can kick an electron, for example, out of an atom,
or it can break one of those bonds. And the
most damaging thing radiation can do is ionized parts of
your body. When it does this, it does things like
(24:04):
break up DNA molecules. It acts like a tiny little
bullet that shoots through your body and breaks things. So
ionizing radiation is very, very dangerous, and that's why it's
important to reduce your exposure to ionizing radiation. Now, things
like uranium and plutonium give off ionizing radiation, which is
very dangerous, and some forms of electromagnetic radiation can have
(24:27):
enough energy to ionize. The threshold for ionizing radiation is
a little bit fuzzy, depends on the material, etcetera. But
it's on the order of magnitude of about ten e
v per photon. This is like the binding energy of molecules.
And in order to have that much energy of photon
has to be in the ultra violet. That's why ultra
violet radiation u V rays are bad for you. U
(24:49):
V does cause cancer, and that's what you're blocking when
you're putting on sunscreen, and that u V light can
pass through clouds, which is how you can get a
sunburn on a cloudy day. So visible light and everything
with a wavelength lower than that, it's not ionizing. It
can't cause ionization in your body, and so it's much
much safer. Now. Five G is well below the wavelength
(25:12):
of even visible light. It's below the infrared. So from
the point of view of ionization, the most dangerous thing
that radiation can do. Five G is not a concern. Yes,
it does have a higher wavelength, and previous generations of
cell phones, but it's well below the energy needed to
do any damage from an ionizing point of view. But
(25:33):
that's not the only way that radiation can damage you.
Ionization is not the only thing that it can do.
For example, it can deposit energy in your body even
without actually ionizing. I mean, this is what an oven does.
Right when you cook a turkey in your oven, you're
using infrared photons. You're using the heat of the oven
to cook that turkey, And yeah, it certainly does damage
(25:56):
the turkey. And so you can hurt people with a
high intensity of low energy radiation. Right here, we're talking
about the intensity and microwave oven uses microwave radiation, which
is much much longer in wavelength than ultra violet photons.
But it's a very high intensity, and so it can
(26:16):
deposit a lot of energy and eventually it can hurt you.
So this is the area to focus on from a
sort of physics and medical point of view. Can being
exposed to a large amount of five G signals do
some damage to the human body. Well, it turns out
that humans have a sort of built in shield to
a lot of this stuff. Most of these photons will
actually scatter off of your skin. Your skin is like
(26:39):
a shield that will reflect a lot of this energy.
The upper layers of your skin are opaque to this
kind of photon, so most of it won't even enter
your body. There were some very early studies that showed
the amount of damage done to tissue based on the
frequency and showed the five G was in a range
that did more damage, but it neglected to take new
(27:00):
count the fact that most of that five G radiation
won't even get into your body. But the fact remains
that this is a kind of electromagnetic radiation where it's
long term exposure has not been studied on the public.
We haven't based people and the kinds of radiation that
five G will generate for long periods and seeing what
would happen. Right, So we just don't know. That doesn't
(27:21):
mean we don't have a good guess. We understand the
physics of it. We think that it's too low energy
to do any ionization damage. We think that the skin
is opaque to it and will reflect most of it,
and so we think we can do the calculations and
it seems totally safe, but we don't have direct evidence.
And the folks that are citing studies that show that
(27:42):
there's no connection between for example, cell phone towers and
cancer are missing the point a little bit because those
cell phone towers are using a different frequency than five G.
So we don't actually have direct data that shows that
five G is safe because it was just invented, right,
And so what can we do here? Science can say
we don't see a reason why it would be dangerous.
(28:04):
We think it will be safe. We do not have
direct proof, so we can't conclusively say it's safe. We
can't point to studies that prove that it's safe. We
can argue and we can make reasonable points that suggest
that it will be safe. But in the end, it's
a question for policy makers when do you make a
decision for how to roll out a new technology which
could have lots of benefits for the public, but also
(28:26):
every new technology does have some inherent dangers, and in
the end, sometimes policy makers do have to make these
very difficult decisions knowing they could help people, but they
could also potentially hurt people. So that's not something I'm
going to comment on because I'm not a policy maker,
but I think that the policymakers should at least be
informed by the science, and I hope that you guys
out there understand the signs of five G. It is
(28:49):
a new technology with higher frequency photons, not high enough
frequency to do ionizing damage, but the impact of this
frequency radiation and very low intensities, how has not been
studied on the general public. That doesn't mean that it's
caused the pandemic or that it's something that you should
worry about. Read more about it, think about it right
to your congress people or representatives, or your president or whoever,
(29:12):
if you have a deep and passionate opinion about how
to balance this question of technology versus safety. All Right,
I want to answer another question, but first let's take
another break. All right, we're back and I'm answering questions
(29:38):
from listeners. We had a question about black holes and
hawking radiation. We had a question about wireless cell phone
towers and the radiation they emit. And now we have
a question about wireless charging. Hi, Daniel, and I was
wondering how wireless charging devices work. I don't understand how
the battery is charged without a visible input into the device.
(30:03):
It's baffling to me. It's like magic. Thanks all right,
thank you for this super fun question. Sometimes physics is baffling.
It defies our intuition, but you know, the universe works,
The universe follows rules. There's always a way to understand
what we see and then sometimes to use that understanding
to build awesome new technology like wireless charging. And your
(30:27):
intuition is that things need a wire because the stuff
around you uses wires. Right, either you plug it into
the wall or you connect it with a battery, because
you're used to a certain kind of way of transmitting energy.
You have energy inside a battery or energy coming in
the wires, and that's in the form of electrical energy,
and those electrons zip along and they deposit that energy
(30:49):
into your device, your phone or your camera, or your
laptop or your blender or whatever. And that certainly is
one way to send electromagnetic energy from one device to
another by using the wire, which is essentially just a
conductor where the electrons can bump into each other and
pass that energy along. However, there are lots of ways
to transmit energy, and you can transmit energy wirelessly, right.
(31:13):
What is a flashlight. A flashlight is a beam of photons.
Those photons have energy. What is a laser A laser
concertainly transmit energy, you can use it to heat something
up from a distance, right, and those photons can fly
through space, even through a vacuum. So conceptually, from a
sort of physics point of view, we understand how it's
(31:33):
possible for energy to start in one place and get
to another place without having a physical connection a wire, right,
even across the vacuum of quote unquote empty space. But
that doesn't tell us how wireless chargers actually work. How
do they get the energy from one device to the
other without the two actually being connected. There's not some
(31:55):
tiny series of lasers in their zapping energy from one
to the other. You certainly don't want your blender to
be zapped with lasers. So how does it actually work.
The first thing to understand is the whole system is
not wireless. It's just like one step there that's wireless.
Usually you have like a base which is plugged into
the wall, and then you can put your phone on
top of that base. It sits on the base and
(32:17):
it draws power from the base. And so it's that
step that we're gonna try to understand. How can you
get energy from the base which is plugged into the
wall and getting energy eventually from your power plant, how
does it get from that base and into your phone.
So this comes from the magic and the beauty of
electro magnetism. And to understand how this works, we need
to remember that electricity and magnetism feel like two different things, right.
(32:42):
Electricity is lightning bolts and electrons, and magnetism is like
fridge magnets and levitating trains. But they are actually two
parts of the same thing. Maxwell, the Scottish clerk a
hundred and fifty years ago, realized that there's a deep
symmetry between electricity and magnetism. And you note us this
because he noticed that electricity can cause magnetic field to
(33:03):
magnetic fields can cause currents, and so that's exactly how
it happens. We have two parts of Maxwell's equations working together.
So the first part is that when you have an
electric current that creates a magnetic field. If you've ever
seen an electro magnet, you know this is true. You
turn on the current, it goes through coils and those
(33:24):
coils create a magnetic field. And every electric engine, for example,
has this property inside it. When you turn on the engine,
what you're doing is turning on electro magnets inside the engine,
which are using the magnet to sort of tug on
another part of the engine and get it to move.
So the first step is to use currents inside the
base station to create a powerful magnetic field. That magnetic field,
(33:49):
in turn can cause electrical currents because another part of
Maxwell's equations tells us that varying magnetic fields caused electrical currents. Right,
So what happens to the base station is you have
this current which is going on and off, creating magnetic
fields which are on and off, and those magnetic fields
then induce a current inside your phone. So inside the
(34:12):
phone there has to be some loop, or inside whatever
device you're trying to charge, there has to be some loop,
and the magnetic fields then induce a current inside that loop.
So you have a loop inside the base station where
you create a current using power from the wall. That
current inside the loop creates a magnetic field, and that
magnetic field then creates a current inside a loop of
(34:32):
wire in the thing that you want to charge. And
so this is a way to transmit the energy from
the base station to the phone or whatever it is
that you're trying to charge without actually having to have
a wire between them. Is essension, like using a magnetic wire.
And this only works because there is this symmetry between
electricity and magnetism, because currents cause magnetic fields, which cause currents.
(34:58):
And the other awesome thing about a symmetry is that
it's the reason that we can see anything. What is light?
What is a photon? It's a ripple in the electro
magnetic field, not the electrical field, not the magnetic field,
but the electro magnetic field. And that exists because varying
electric fields caused magnetic fields, which caused varying electric fields.
(35:20):
So what a photon actually is is a field that
slashing back and forth between the electric and the magnetic field.
That's what allows it to like pass through the vacuum
of space. It supports itself, it propagates itself by going
back and forth from electro to magnetic fields. And this
was the beautiful inside of Maxwell. He saw these equations
(35:41):
and they put them together. He thought, oh, my gosh,
light looks just like a wave that's slashing back and
forth and moving at some speed. And he did the calculation.
He's like, oh, look, it moves at the speed of light.
So that was a beautiful moment, sort of in theoretical physics,
putting these two pieces together, understanding the symmetry between electric
and magnetic field. And it's that same insight that allows
(36:02):
us to do inductive powering, to use magnetic induction to
take a coil of current and transfer that energy into
another coil. Now, this is fascinating if people have done
a lot of studies to see, like how far can
it work. You're probably most familiar with charging stations at
Starbucks where you will get charged from this wireless charging station. Now,
(36:23):
the larger the coil inside the base station, the longer
the wavelength of this radiation essentially, and the larger the
distance that that power can charge. There was a record
set in two thousand and seven where somebody was able
to charge something two meters away. That's pretty awesome, Right,
two meters away is a good distance, not enough that
(36:44):
you can like drive around town and keep your phone
charge from your house, but it's pretty cool, and it's
the kind of thing where people are making strides and
eventually there'll be a breakthrough and we'll be able to
send power at even greater distances. And you know, your
phone is not the only example of this technology. G
if anybody out there has an inductive range. It's the
kind with coils in it. But those coils don't feel
(37:06):
hot because they're not transmitting the energy by making themselves
glow really really hot, like the elements inside your oven,
which would be giving off infrared radiation. Instead, they're creating
magnetic fields, which then cause currents inside a pan that
you put on top of the stove, so the pan
gets hot, but the surface of the stove itself is
(37:27):
not hot because there's no infrared heat passing directly from
inside the range to the pan. And then you have
this coil inside the range, and that coil has a
lot of electricity in it, which is creating a magnetic field,
which is creating a current inside your pot, which then
turns into heat of the pot. So it's able to
transmit this energy and heat of the pot without actually
(37:49):
heating up the stuff in between, which is pretty awesome
and it means that it's harder to burn yourself. So
thanks very much for asking that super fun question about
this cool technology. It does seem like magic, but it's
actually something that we can understand, and that's the beauty
of the universe that amazingly it seems like no matter
what happens out there, if you think about it carefully,
(38:10):
if we put our collective heads together, we can figure
it out. And so, even though there are so many
mysteries remaining about the nature of the universe and what's
going on inside black holes, and how the universe started
and what is everything made out of, at the smallest,
tiniest level, all these questions are just the possibilities for
new discoveries, the possibility to reveal something new about the
(38:31):
universe that we didn't know that would blow the minds
of our grandparents. It means that one day our grandchildren
will make these discoveries and will blow our minds. So
until then, keep thinking about it, keep asking questions, and
send us all of your questions. We love to hear
your thoughts. Thanks very much. Tune in next time. Thanks
(38:59):
for listening. Remember that Daniel and Jorge Explain the Universe
is a production of I Heart Radio. For more podcast
from my Heart Radio, visit the I Heart Radio Apple
Apple Podcasts, or wherever you listen to your favorite shows.
H
Hosts And Creators
Daniel Whiteson
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