A big thanks to Squarespace for sponsoring today’s video!
I’m going to preface this video by saying the universe is a very weird place for us
simple mortals.
Our life spans are just a blink of an eye compared to the age of the universe, and things
we expect to be constant, like space and time, behave very differently from what you may
initially expect.
So, keep this in mind throughout the video.
To answer the question of where the Big Bang originated, I am going to have to provide
some context.
The leading theory regarding the beginning of the universe is the Big Bang Theory.
And without going into the complicated details, I’ll summarise it like this: About 13.7
billion years ago, everything that is in the universe today was crammed together into a
space the effective size of zero.
At the very beginning, not even atoms existed, it was just a hot and dense soup of fundamental
particles.
Since the beginning, the universe has expanded rapidly.
As it expanded and cooled, atoms formed, and stars were born.
Now, the universe’s expansion combined with the constant speed of light has turned the
universe into a time machine.
If we look at any region of space, we don’t see galaxies as they are, but as they were.
Galaxies we see in the foreground are much more developed, forming the more elegant and
defined shapes you see here.
That is because we are seeing these galaxies as they were only millions of years ago, they’ve
had billions of years to form since the start of the universe, and so they look much more
mature and developed.
On the other hand, as we look at more and more distant galaxies, these galaxies appear
younger.
Galaxies that are billions of light years away appear as they would have shortly after
the Big Bang, because the light emitted by them has taken that long to get to us.
They look misshapen and there is a lot of star formation going on within them.
But in reality, it’s important to remember that these galaxies are just as old as ours,
and they no longer occupy the location where we can see them, they are probably much further
away by now because of the expansion of the universe.
It is also important to realise that there is no centre of the universe, or conversely
that everywhere is the centre of the universe.
Because it doesn’t matter where you are, here or a billion light years away, everything
is expanding away from you.
Everything is expanding away from everything.
Just as a side note though, gravity combat the effects of the universe
expanding.
That’s why superclusters of galaxies exist, and the universe has a filamentary structure.
The gravity from galaxies is attempting to keep clumps of them together even though the
expansion of the universe is also pulling them apart.
What you end up with are filaments with empty bubbles or ‘voids’ in between that will
only get bigger as the universe expands further.
You may have heard of the term the ‘Hubble Constant’.
This is how fast the universe is expanding, currently thought to be around 80,000kph per
million light years.
So, for a section of space one million light years across, it expands by 80,000km every
hour.
A section one hundred million light years across would expand by 8,000,000km every hour.
The current value of Hubble's Constant implies that the entire universe is expanding faster
than the speed of light, meaning there is a sphere around us that we will not be able
to see beyond.
Past this sphere, galaxies are moving away from us faster than the speed of light, meaning
light emitted by them can never reach us.
Everything within this sphere is the ‘observable universe’, another term you’ve probably
heard before.
We can’t see or detect anything beyond the observable universe, which is why we don’t
know if the universe is infinite or finite.
Even if it is finite, it couldn’t have an edge and would have to loop around, because,
well, the universe is just that, everything that exists.
What would be beyond the edge of the universe otherwise?
So, we want to know where the Big Bang originated.
Where in the night sky do astronomers look to see where the universe started?
Well, the answer is, everywhere.
Because the universe always has been the whole universe, it has just changed in size, from
being very small to very big.
It doesn’t have specific co-ordinates, because it is an explosion of the co-ordinates system
itself.
And this is what shortly after the Big Bang looked like, albeit in microwaves.
This is what we call Cosmic Microwave Background Radiation, and you can see it anywhere you
look into space, (assuming you have a space telescope that can detect microwaves, because
Earth’s atmosphere is really good at blocking microwave radiation).
350,000 years after the Big Bang, the entire universe was hot, around 2,500°c.
Even though this heat would have emitted visible light, we can’t see it because the expansion
of the universe stretched the wavelengths of electromagnetic radiation by a factor of
one thousand, meaning the photons no longer arrive at Earth as visible light, but rather
as microwaves.
So just like seeing those distant galaxies billions of light years away using visible
light, we can see what the universe looked like before galaxies even existed by observing
these microwaves.
This makes this image effectively the oldest thing we have ever seen.
Fascinatingly, slight variations in the image are the precursors to the filamentary structure
of the universe you’ve seen earlier in the video.
We are quite lucky in that there are not really any bright sources of microwaves in the universe
apart from the Cosmic Microwave Background Radiation, which means this view is a relatively
uncontaminated view of the universe 350,000 years after the Big Bang.
Can we see beyond that?
No, not really.
Before that, atoms were just becoming a thing and light couldn’t travel through the soup
of fundamental particles.
So, the centre of the universe is everywhere, and nowhere in particular.
Look at any part of space with a microwave telescope, and you’re effectively looking
at shortly after the Big Bang.
Like I said, the universe is weird.
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