Can you spot the problem with this image?
This is the baby photo of our universe.
It shows the whole universe as it was when it was just 380,000 years old.
Ok, so that doesn’t sound very young for a baby photo, but if you consider the universe
today to be an 80 year old person, than that image is the equivalent of a baby pic taken
at 19 hours after birth.
So it truly is a baby photo.
But why can’t we get a photo from an earlier time than that?
Well, the problem is the universe before 380,000 thousand years after the big bang was so hot
that all the matter in it, all these protons and electrons was in a state of plasma.
They were all flying all over the place and any light passing through there would get
scattered or absorbed.
So the whole universe was opaque.
The light couldn’t travel anywhere, until 380,000 years when the universe had expanded
and cooled enough for the protons and the electrons to get together and form hydrogen
atoms, right, this clear gas.
So finally after bouncing around for 380,000 years like pinballs, these photons could finally
travel out through space.
And there they would go, on these photons would go for 13.8 billion years.
The whole lifetime of our universe these photons were just traveling through space, not hitting
anything until they reached our detector.
And that is how we formed this baby image of our whole universe.
Now, of course, over that time our universe expanded a lot.
So those photons which started out as ultraviolet light or visible radiation, blue light, ended
up as microwaves by the time it got to us.
They expanded along with the universe.
And that is why we can’t see the earliest light in the universe, but we can detect it
with these microwave telescopes.
These microwaves were actually found by accident.
Two radio astronomers, Penzias and Wilson, were actually trying to take radio images
of certain things in the sky, stars and galaxies, but they found there was this annoying background
noise when they tried to make their measurements.
So they thought maybe there wasn’t a cable connected correctly or maybe it was bird poop.
But it turned out it was actually the signal from the early universe.
And everywhere they pointed their telescope, they saw exactly the same signal.
I mean, the whole early universe was incredibly uniform according to their observations.
So the real early baby photo looks like this.
That was the state of the universe at 380,000 years after the big bang.
It was uniform, so incredibly uniform everywhere.
The variations were only about one part in 100,000.
So we built better telescopes and sent them into space to try to give us the detail.
I mean, we are interested in the variation, not just the fact that it is totally uniform.
So this is the first blurry baby photo that we took and we liked that one so much that
we built a better telescope and we got a better image, a higher resolution image.
Now you can clearly see that the early universe has these hot spots and cold spots.
And we liked that image so much that we built an even better telescope and got an even better
image.
This is like the perfect baby photo.
I mean, this is like seeing the eyelashes, right?
This is so much detail.
You can see the little hot and cold spots.
And those are so important to our existence, because they show that the early universe
was actually a bit lumpy.
There were places with slightly higher density and places with slightly lower density.
And that is incredibly important, because it is the places of higher density that will
gravitationally pull together the matter around them clumping into stars and galaxies and
the structures that we are a part of.
I mean, without a little bit of non uniformity we could not be here, because stars and galaxies
would never coalesce.
Now where did those lumps come from?
Well, they seemed to be the signature of quantum fluctuations, or it is the idea that we are
made of quantum fields and it is impossible to keep those quantum fields perfectly still.
They are always varying, bubbling a little bit.
You know, particles popping in and out of existence.
Heisenberg’s uncertainty principle says that we cannot keep the uncertainty in energy
down to absolute zero, which means there is always going to be some matter appearing and
disappearing.
And that seems to be what created the lumpiness in the universe that we can see.
And it is that which gave rise to all these major structures like galaxies.
So we should be thankful for this sort of crazy fluctuation because without it we could
not be here.
But focusing in on the lumps, we forget that what the true baby photo is, is of incredible
uniformity and that is the problem with this image.
It is the fact that the whole universe had basically the same temperature 380,000 years
after the big bang and that doesn’t make a lot of sense.
I mean, why should that part of the sky be exactly the same temperature as that part
of the sky?
It is kind of baffling.
And scientists were at a loss with how do we explain it.
I mean the expectation after the big bang is that everything would be in a massive jumble.
So this incredible uniformity had to be explained somehow.
So they proposed something called inflation, which is fairly straight forward, but a little
bit crazy.
It is the idea that right after the big bang, we may have had a totally mottled mess, right?
The big bang did not necessarily give us anything clean or tidy.
But right after the big bang all of the sudden the universe just expanded incredibly rapidly,
like the likes of which we have never seen again, just all of the sudden...
The whole universe got huge very fast.
The inflation is proposed to have started at this time and finished at this time after
the big bang.
I am not making this stuff up.
Like honestly it is nuts.
But the reason that would make the universe that we see in that baby photo is because
it would stretch out all of the wrinkles.
It would create something quite uniform.
I mean, imagine you are looking at a picture of a landscape.
You see all these different colors, different structures, right?
It is very varied.
Now imagine all of the sudden that photo is expanded in front of you, like...
Now all you are going to see is one color, because of how much that whole photo has been
blown up.
Well, it is a very similar thing with the universe.
We imagine that we could see something totally uniform and totally homogenous if right after
the big bang the whole universe just blew up.
But this is kind of a crazy idea created to deal with a problem with that picture.
I mean, is it really true?
Did inflation really happen or is it just a convenient fiction we have invented to try
to explain this baby photo?
How can we ever figure out what happened before that 380,000 year barrier?
I mean, we are not going to get any light from before then.
But maybe there is something else that we can detect, gravitational waves.
Now the idea of gravitational waves is that if you wiggle a charge you get electromagnetic
radiation, because you are varying electric and magnetic fields.
Similarly, if you wiggle some mass, you should get gravitational waves, because of how they
disturb the gravitational field around them.
I mean, that disturbance should ripple out through space.
The problem is gravitational waves are incredibly weak.
So we have been trying to detect them for a while.
Maybe gravitational waves from two stars orbiting each other really fast.
But so far on earth we have not be able to detect their existence.
But here is the idea.
If in that moment of inflation everything expands out so rapidly, then the gravitational
waves from that moment would stretch and squeeze all of the matter in the early universe.
And scientists thought we may be able to see the impact of those gravitational waves on
the baby photo of the universe.
But what we would need to take is an image so pristine that it not only records where
the hot and cold spots are, it also records the polarization of the light.
Now the polarization is basically just the way that the electric field of the light is
oscillating.
So it can oscillate back and forth this way or it can oscillate back and forth this way.
The idea is we can model what gravitational waves should do.
They should create a kind of swirl in the polarization around these hot and cold spots.
We know exactly what it should look like and that is what scientists have done.
They measured the polarization of the light coming away from the 380,000 years after the
big bang, all that plasma.
And what did they find?
Exactly what thy predicted would happen if inflation did occur and gravitational waves
have affected the plasma of the early universe.
That is what everyone is so excited about.
Essentially we are seeing that what we thought was true at the very tiny fraction of a second
after the big bang, we can see its signature in light that is only arriving at the earth
right now.
And what is more, we know that quantum gravity must work, in a way, because that is the earliest
sign that general relativity and quantum mechanics are working together, something we haven’t
been able to demonstrate before now.
So this is one of the hugest discoveries in science of all time and certainly my lifetime.
It is a fun time to be learning about science and thinking about our universe, because we
are just getting new clues into how our whole universe was born.
When you look at all of the incredible things in the universe, the galaxies, stars, black
holes, the earth, people, plants, computers, the internet, just think to yourself, in the
words of Carl Sagan: These are some of the things that hydrogen atoms do when given 14
billion years of cosmic evolution.
And, in fact, one of the things they do is create a website where you can download information
at the click of a button.
Audible.com is one of the leading providers of audio books with a vast range of titles,
over 150,000.
And this week I wanted to recommend a book by Carl Sagan called Contact which I absolutely
love, because I feel like he correctly sort of describes the experience of what it is
like to be a young scientist.
I could really relate to the main character.
So if you are into science and you haven’t read or listened to this yet, you definitely
need to.
And you can download it for free by going to Audible.com/Veritasium or you can pick
any other book of your choosing for a one month free trial.
So I want to thank Audible for supporting me and I want to thank you for watching.