All good things come to an end. This is true for bad things as well.. Whether you think the universe is good, bad or indifferent, it will come to an end…someday.
How will that happen? Will it simply die a slow death over time? Will it die dramatically in a big explosion as the universe is ripped apart? Or will we see a big bang in reverse as the universe ends in a colossal crunch?
There are three factors that will determine the ultimate fate of the galaxy: The overall shape of the universe, The amount of dark energy, And the rate of growth of dark energy
There are three possibilities for the shape of the universe – closed, open and flat. If the universe is closed, it means that it is shaped like a sphere – so even though it may be expanding right now, it will eventually stop and converge into a big crunch, which would result eventually in everything ending in a black hole type of singularity
If the universe is open, that means it is shaped like saddle, which means that it will keep expanding forever, and the ultimate fate of universe in this case – is most likely a big freeze, where galaxies would be become very far apart, such that we would not be able to see any other galaxies besides our own. The stars would eventually burn out as all the hydrogen gas in the universe is used up. The only things remaining would be black holes. And these too would eventually evaporate because of something called hawking radiation. This is where a small amount of matter is constantly being discarded and disappearing near the event horizon of black holes
The third possibility is that the universe is neither closed nor open but is flat, shaped like three dimensional piece of paper. This means it will keep expanding forever.
So what really is the shape of the universe. The most recent observations suggest that it is in fact flat. This was verified by the Wilkinson Microwave Anisotropy or WMAP probe.
For a long time, physicists thought that the big freeze is how the universe will end, even with a flat universe because Edwin Hubble discovered that the universe is expanding. So it was thought that the universe will continue to expand, the total entropy of the universe would become infinite over trillions of years, and the universe would just die out – without much drama
But all this changed in 1998, when physicists discovered that the expansion is accelerating. Normal matter can’t make this happen, so a theoretical new energy was introduced, called dark energy. See my video on Dark Energy.
Dark energy seems to have a unique property. Its density does not seem to decrease over time or space. This is not like gravity which decreases over distances and space. Dark Energy seems to remain the same or increase throughout all space. This is unusual but does not break any laws of physics.
But if the universe is expanding with the same dark energy density, this has to mean that more and more dark energy is being created as the universe expands.
So we know the expansion is accelerating. What we don’t know is whether the rate of acceleration is constant. If the rate of acceleration is also increasing then the fate of the Universe is really crazy – even by science fiction standards, because then the universe will end in something called the Big Rip.
This means that over time, dark energy would overwhelm all gravity, all forces, and even the fabric of space and time. All galaxies would be pulled apart, then all of the planetary orbits would be pulled apart, then all the stars and planets would be pulled apart into their constituent atoms.
And it wouldn’t just stop there because even all the atoms and subatomic particles like protons and neutrons would be pulled apart because even the strong force keeping atoms together would be overwhelmed by dark energy. And then finally, even the fabric of space and time would be pulled apart. So our flat paper universe would be pulled apart too.
Then what happens? Many scientists think that at the moment that space and time are pulled apart, a new big bang would occur – as if the universe would turn inside out – resulting in a brand new universe. So, from destruction, new creation – wouldn’t that be the ultimate irony of creation.
So what happens to us humans in these scenarios. Well, first of all, estimates of this happening ranges from about 22 billion years to 100 trillion years, so it won’t happen anytime soon. But what can we do to save ourselves? Some physicists have proposed that to escape this hellish scenario, we should build our own universe in some futuristic physics lab, and go into it before this universe is destroyed.
Or, who knows, in millions of years, we may even be able to figure out how to control the ultimate fate of the universe, and perhaps even become One with it.
