as for how it's going to end... ummmm

Hi everyone, in Universe A, Julian here for DNews.

The Big Bang Theory is more than just a TV show my parents keep telling me I should be on.

It's our best explanation for how the universe, as we know it, started.

When Edwin Hubble looked at the night sky in 1923, he discovered that the universe was much bigger than just our Milky Way.

There were actually metric oodles of galaxies, all over the place.

Then in 1929, because he wasn't done being a science boss,

Hubble also noticed that the majority of galaxies are speeding away from us.

Logically, then, if you go backwards in time,

everything must have been smushed together in a singularity, at some point,

and I mean that both physically and temporally.

With all that phenomenal cosmic power in an itty-bitty living space,

it blew right up in the greatest fireworks display of the last 13.8 billion years.

As you can imagine, this discovery was a game-changer.

Einstein's equations on general relativity from 1917

should've mathematically predicted an expanding or contracting universe,

but the math had been intentionally fudged by a scientist who didn't want to believe the universe wasn't static

and what was that name of that idiot who ruined Einstein's math?

A man by the name of Albert Einstein.

Einstein called his creation of his cosmological constant

"The greatest blunder of his career"

and as a result, has been doomed to obscurity.

So, if the universe has a beginning, then what does that mean for how it will end?

Where is this all going?

Well that nut's a little tougher to crack.

At first, it was thought there was two possibilities.

If the universe has enough stuff in it, gravity slows the expansion, and eventually it will collapse into a singularity and maybe even another big bang.

This is elegant, and beautiful, and makes wonderful, satisfying sense.

Unfortunately, the universe is under no obligation to make sense to you.

And the other possibility is happening.

The universe isn't just expanding, it's accelerating.

What's driving the acceleration? What is making space itself expand like the surface of an inflating balloon?

We have no idea.

Our best guess is some, as yet, unexplained source of energy snappily known as "dark energy."

So, if everything keeps going the way it is, it looks like the universe could expand and exist forever.

Whether life can exist forever is a different story.

Our sun will exhaust it's fuel in about 5 billion years, while much smaller red dwarfs will use their fuel in trillions of years.

That is an incomprehensibly long time, but that time will come nonetheless.

Black holes will still be doing stuff; radiating particles back into the void,

but even supermassive black holes will dissipate after googols of years.

Eventually entropy will spread energy uniformly across the universe and it just won't be possible to do literally anything.

So life as we know it, is 'kaput'.

This is called the "Heat Death of the universe"

or "The Big Freeze"

and it looks like we're headed that way.

An international team of astronomers just studied the energy output from two hundred thousand galaxies

and discovered its half of what it was just two billion years ago.

We're apparently in the midst of a steep decline but eventually it will slow down

as only the biggest black holes are left petering out.

That is one way the universe could end ...

not with a bang but a whimper ...

but we don't know enough about dark energy to assume it's going to keep acting the way it does.

Maybe it'll slow or even reverse and we'll get a big crunch or a cyclical universe

or maybe everything, even atoms themselves, will get ripped to shreds.

Remember I said dark energy is making space itself expand?

Things aren't just moving away from us. Space itself is growing.

It stretches at about 70.4 kilometers per second per megaparsec

which means that if you had two objects a megaparsec apart with no velocities relative to each other

every second they would get 70.4 kilometers farther away.

A megaparsec is 3.3 million light years though so it's a very tiny inflation.

Over smaller distances other forces like gravity or the strong nuclear force

means the expansion of space doesn't affect atoms or solid objects.

Dark energy could become more dense, though,

and given long enough the stars, planets, even atoms, could be ripped apart.

This is called "The Big Rip."

As you can tell, dark matter is the linchpin of these two theories and there's still more possibilities.

One of them, cosmic uncertainty, essentially throws its hands in the air and says we don't know what will happen until we understand dark energy.

So, clearly, figuring out this stuff will tell us a lot about our future.

Well maybe not our future. You and I will be long gone by the time any of these

scenarios would play out and the human race itself may have vanished or evolved into something unrecognizable.

Sadly, nobody lives to see the future but it's going to be a really interesting place.

So, that covers many of the prevailing ideas on how the universe will end but what happens when YOU end?

Trace talks about that here:

Firstly, at death all your muscles relax.

It takes burning oxygen for energy to keep you tense: no O2, no tension.

This includes the body's sphincters which is why death often causes defecation and incontinence.

Where do you think the universe is going? Let us know in the comments or Facebook or Twitter @dnews.

Subscribe for more answers to life's questions big and small and we'll see you next time on DNews.