Pretend you’re a perfectly flat chess piece in a game of chess on a perfectly flat and
humongous chessboard.
One day you look around and ask: How did I get here?
How did the chessboard get here?
How did it all start?
You pull out your telescope and begin to explore your universe, the chessboard….
What do you find?
Your universe, the chessboard, is getting bigger.
And over more time, even bigger!
The board is expanding in all directions that you can see.
There’s nothing that seems to be causing this expansion as far as you can tell – it
just seems to be the nature of the chessboard.
But wait a minute.
If it’s getting bigger, and has been getting bigger and bigger, then that means in the
past, it must have been smaller and smaller and smaller.
At some time, long, long ago, at the very beginning, it must have been so small that
it was infinitely small.
Let’s work forward from what happened then.
At the beginning of your universe, the chessboard was infinitely tiny and then expanded, growing
bigger and bigger until the day that you decided to make some observations about the nature
of your chess universe.
All the stuff in the universe – the little particles that make up you and everything
else – started very close together and then spread farther apart as time went on.
Our universe works exactly the same way.
When astronomers make observations of distant galaxies, we see that they are all moving
apart.
It seems our universe started very small and has been expanding ever since.
In fact, scientists now know that not only is the universe expanding, but the speed at
which it’s expanding is increasing.
This mysterious effect is caused by something physicists call dark energy, though we know
very little else about it.
Astronomers also observe something called the Cosmic Microwave Background Radiation.
It’s a very low level of energy that exists all throughout space.
We know from those measurements that our universe is 13.8 billion years old – way, way older
than people, and about three times older than the Earth.
If astronomers look back all the way to the event that started our universe, we call that
the Big Bang.
Many people hear the name “Big Bang” and think about a giant explosion of stuff, like
a bomb going off.
But the Big Bang wasn’t an explosion that destroyed things.
It was the beginning of our universe, the start of both space and time.
Rather than an explosion, it was a very rapid expansion, the event that started the universe
growing bigger and bigger.
This expansion is different than an explosion, which can be caused by things like chemical
reactions or large impacts.
Explosions result in energy going from one place to another, and usually a lot of it.
Instead, during the Big Bang, energy moved along with space as it expanded, moving around
wildly but becoming more spread out over time since space was growing over time.
Back in the chessboard universe, the “Big Bang” would be like the beginning of everything.
It’s the start of the board getting bigger.
It’s important to realize that “before” the Big Bang, there was no space and there
was no time.
Coming back to the chessboard analogy, you can count the amount of time on the game clock
after the start but there is no game time before the start – the clock wasn’t running.
And, before the game had started, the chessboard universe hadn’t existed and there was no
chessboard space either.
You have to be careful when you say “before” in this context because time didn’t even
exist until the Big Bang.
You also have to wrap your mind around the idea that the universe isn’t expanding “into”
anything, since as far as we know the Big Bang was the start of both space and time.
Confusing, I know!
Astronomers aren’t sure what caused the Big Bang.
We just look at observations and see that’s how the universe did start.
We know it was extremely small and got bigger, and we know that kicked off 13.8 billion years
ago.
What started our own game of chess?
That’s one of the deepest questions anyone can ask.