How Will The Universe End?

How Will The Universe End? 

We all know how the universe began. For those who don't know, please come out from beneath the rock you have been living under. The big bang theory is far more than just a television show that stereotypes people who love science. To be honest,however,the term "big bang" can be very misleading at times.
Once upon a time, almost 14 billion years ago, there was a singularity. For some as yet unknown reason, that singularity then exploded into the infinite everything of the universe in an inconceivably fast moment. For the past 13.8 billion years or so, the universe has continued to expand.
The question that naturally arises from this theory of an ever-expanding , infinite universe is : when will it stop expanding?and if it does, what would be the cause of it stopping? Logically, or rather, cosmologically, this would be the point where the universe begins to die.

1.Big Crunch :

Picture Showing Big Crunch

If the crictical density of the universe is high, then the force of gravity would give rise to a positively curved, or a closed, universe. It is assumed that at some point, the gravity of dense universe would overpower the expansion forces and pull it all back inward.The big bang would be countered and negated by the big crunch, which would bring the universe back into similarity could then expand again, giving birth to new universe.

2. The Big Freeze

Big Freeze

If the crictical density of the universe is low, however,  then the effect of gravity would never be able to hold the universe in a closed shape (such as the aforementioned ballon). This would lead to a negatively curved, or an open, universe. Gravity, in this case, would not be able to restrain the expansion of the universe . The universe would continue to expand untill it runs out of energy. Everything would eventually stop spinning and flying through space and slow to a whimpering death, which is why this potential endgame is called big freeze.

Heat Death 

If the critical density is just right, the expansion of the universe will go on forever, but would slow itself down, causing a flat universe.With the use of the WMAP spacecraft, it was discovered that the actual density of the universe would lead to a flat universe.  However, that's not the only breakthrough discovery in the possible death of out universe. In 1998, a team of astronomers observed distant supernovae to get a sense of how fast the Universe was slowing down.To their surprise, they discovered that rather than decelerating, the universe was actually accelerating ! Thousands of scientists around the world groaned as one, realizing thay they needed to find a better thoery!
The question,obviously, is what mysterious force could be speeding up the process of expansion ?scintists know next fo nothing about it, and therefore call it dark energy, which presumably constitutes 68% of the universe. It behaves like an anti-gravitational force,  pushing the universe towards expansion. The weridest part about dark energy is that it seems to be a cosmological constant - as the volume of the universe increases, Dark energy expands to keep its energy density constant.
In other words, Dark energy keeps growing as the universe expands,but matter (5% ordinary matter and 27% dark matter)  doesn't. In fact,  all matter will eventually be converted into energy. According to rhis logic ,or rather cosmo-logic, the  universe will reach a stage of maximum entropy,  where energy is evenly spread throughout. If there is no difference in energy, then there will be no work. Thus, the universe will finally cease to function. This scenario is called the heat death of the universe.