This theory is known as the Big Bang, and it's the most widely accepted story of the creation of our Universe.

Scientists came up with this universal origin story when they observed that every single galaxy in space is moving away from us, even today.

That means that at one point in time, everything could have been condensed into an infinitely dense spot, known as a singularity.

This singularity was really hot too.

Other evidence of the Big Bang is something known as

Cosmic Microwave Background.

It's radioactive remnants from the early days of our Universe, remnants that you can only see with the help of a telescope.

But what if we have this all wrong?

What if the Universe didn't start like this?

What else were we wrong about?

This is WHAT IF, and here's what would happen if everything you knew about the Universe is wrong.

I'm sure you're not looking forward to the end of the Universe.

But glancing at its future demise could flip your understanding of the Universe and its origins.

You know that our Universe is continually expanding outward, so you might assume that it would likely continue expanding forever.

This could be true, and this is why the most widely accepted theory involves the Universe doing just that.

It's called the Big Freeze.

And what's really cool about this is a mysterious and invisible force that makes the Universe expand.

It's called dark energy, and it makes up 69% of the Universe's mass.

Another 26% of it is made of dark matter, and only 5% of the Universe is plain old ordinary matter.

If all this material originated from one point and just kept expanding, eventually, all this heat and energy would be very, very spread out.

At a certain point, everything would be so far away that the entire Universe would reach a ridiculously frigid temperature, absolute zero.

Absolute zero is the lowest temperature possible.

It translates into zero Kelvin, or if you prefer a more familiar temperature scale, minus 273 °C.

By the time the Universe reaches this super low temperature, you wouldn't be able to see any distant galaxies from your vantage point in the Milky Way.

Don't worry though, that would be at least a couple of trillion years from now.

Now, that's just one theory.

It's also possible that the death of the Universe will be the exact opposite of this.

Instead of expanding forever, the Universe could shrink back together.

Time for the Big Crunch.

All of the matter in the Universe, taken as a whole, has an unimaginable amount of gravity.

It might be enough gravitational force to battle the mysterious dark energy, and win.

If this Big Crunch were to happen, the Universe would start to contract in on itself.

Galaxy clusters far away would merge.

Eventually, stars and planets in our own galactic neighborhood would clump together too.

And this increasing density would heat up the whole Universe.

All that cosmic microwave background radiation from the Big Bang would get so heated that it would be hotter than stars.

We're talking 5,000 °C hot.

The Universe would become a scorching, chaotic mess.

As temperatures continued to rise, and more mass got crushed into a teeny, tiny region, atoms would start to break apart.

The Universe would be turning into the densest black hole possible.

While that would certainly be the end of the Universe as we know it, it might just be the beginning of a new one.

And that would be proof that our Universe is much, much older than we thought.

The Universe may have formed itself over and over again.

In this violent cycle of contraction and expansion, you wouldn't have the slightest chance of surviving to witness this epic event firsthand.

No one would.

So for now, all of this is just an end-of-times theory.

And it has a big name, the Big Bounce.

It suggests that the Universe expands and contracts all the time, just like a lung that breathes in and out, only in slow motion.

And not just once or twice.

According to this theory, there may have been billions, trillions, or even an infinite number of Universes, both before and after ours.

Each time the Universe reforms, it could create completely different laws of physics.

This would create all kinds of strange possibilities.

There could be Universes with no life, no stars, and not even an atom in sight.

Now, this is all pretty wild.

It gets wilder from here.

Some scientists debate that everything we know about our Universe is wrong.

What we know about the cosmos is based on what we can see and study in our galactic neighborhood.

Then, we assume that it works like that everywhere else in the Universe.

The idea is old, and it's called the cosmological principle.

But we may have been wrong all along.

It could be that the way our Milky Way galaxy moves through the Universe is distorting our data.

I mean, we've never had any hard evidence to confirm our theories.

So there's no way of seeing the bigger picture from where we stand.

This is where you could be starting to doubt whether any of this is real to begin with.

Surely, our Universe, the one we can see, must exist, right?

Well, not so fast.

You have quantum mechanics to thank for what I'm going to tell you next.

Scientists who study quantum mechanics theorize about the nature of the Universe on an atomic level.

And according to some scholars in this field, the Universe must be one of two things, real or local.

Bear with me here.

I know this can be mind-numbing.

If the Universe is real, that would mean that it has specific properties like color and mass that exist even when you're not looking at them.

For example, take a red ball.

If it's real, the ball is red even when there's no one around to look at it.

On the other hand, the Universe could be local.

This means that the Universe can only exist because we are there to observe it through our telescopes.

So if you think about the red ball again, without anyone around to observe it, it could have any color, or no color at all.

Only when you look at it and see that it's red does it actually become red.

That's quantum physics 101.

But there's a catch.

The Universe could be either real or local.

It can't be both.

And remember that the Universe is ridiculously big.

It could be infinite.

Our telescopes just aren't powerful enough to observe all of it.

So that means we can't know for sure if the Universe is even real.

You didn't see that coming, did you?

Well, that should be enough of a head-scratcher to keep you pondering about how everything really came to be, where it all could eventually go, and what's the meaning of it all anyway.

But hey, why stop there?

Wouldn't it be cool if the Universe were actually like a giant brain?

Well, that's a story for another What If.