14May2014

What Is The Ultimate Fate Of The Universe?

 Ultimate

One question that will always be pondered about is the what is the ultimate fate of the universe? It’s a frightening question to think about. No more life, stars, planets, black holes or galaxies. Everything would be gone. Well there are a few theories on how the universe will end and none of them have any mercy. However, there are scientific theories that actually rival each other because it depends on whether the universe expands infinitely or not.

Once the Big Bang theory came into play the question of the ultimate fate of the universe became a valid cosmological question. This all depends on the physical properties of the universe such as mass, energy, average density, and the rate of expansion. In addition to answering the fate of the universe we will also answer if the universe will keep expanding forever. Well the growing consensus is that the universe is flat and will continue to grow on forever. Let’s take a deeper look and understand why.

Here are three ways our universe can look:

Shape of the Universe

Shape of the Universe- Here are 3 ways our universe can look. This all depends if it exceeds the critical density or not. Credit: NASA

The rate of expansion depends on the Hubble constant (Ho) while the strength of gravity depends on the density and pressure of mass in the universe. If the pressure of matter is low, like how most forms of mass are, then the universe is governed by the density. If the density in the universe is less than critical density then the universe will expand forever. If the density of the universe is greater than critical density then the universe will collapse onto itself.

So looking at the 3 different cases above, if the density in the universe is greater than critical density then you will have a sphere shaped universe. If it is less than the critical density then you’ll have a saddle shaped universe. In the third scenario if the density in the universe equals the critical density then you’ll have a flat universe. 

explosion

This artist’s impression shows the surroundings of the supermassive black hole at the heart of the active galaxy NGC 3783 in the southern constellation of Centaurus (The Centaur). New observations using the Very Large Telescope Interferometer at ESO’s Paranal Observatory in Chile have revealed not only the torus of hot dust around the back hole but also a wind of cool material in the polar regions. Credit: Gizmodo via NASA

There are a few ways that this universe can end (and perhaps even more). Now that we have an idea of what a closed universe (greater than critical density) open universe (less than critical density) and flat universe (equal to critical density) look like we can talk about what would happen in each type.

In a closed universe there would be a lack of a repulsing effect from dark energy so gravity in turn would eventually stop the expansion of the universe and then the universe would start to contract until all matter collapses onto itself. This would end up back to the point of singularity or the “Big Crunch”. However, if there is a significant amount of dark energy then the universe can continue to expand forever even if the density is greater than critical density.

In an open universe a negatively curved universe without dark energy would expand forever. The universe would end in a heat death (known as Big Chill as well), or Big Rip. Basically a heat death is where entropy increases in an isolated system (system = universe). Entropy should never decrease otherwise the universe will be at maximum disorder which is a place you probably don’t want to be. So since entropy is at a maximum and cannot increase any further all the energy gets evenly distributed throughout the cosmos leaving no room for any reusable energy to burst into existence. The Big Chill is similar where the temperature of the universe reaches absolute zero and it would take 1-100 trillion years for a star to form. In the end there would be nothing but black holes which would eventually disappear as well.

http://www.fromquarkstoquasars.com/wp-content/uploads/2013/03/The-Big-Rip-2.jpg

One theory of how the universe could potentially end relies on the assumption that the expansion of the universe will continue indefinitely until the galaxies, stars, planets and matter rip apart.

The Big Rip is a special case scenario or a special case of phantom dark energy. This is where the density of dark energy increases with time causing the rate of acceleration to increase with time. As a result of this, starting with galaxies, all forms of matter will be ripped apart into elementary particles and shooting away from each other. In a flat universe it has the same outcome as an open universe due to the lack of dark energy and an infinite expanding universe.

Of course there is also the multiverse theory in which there are multiple universes and there may not be an actual end to the universes as others keep popping up. It’s strongly believed that the Big Chill will most likely be the fate of our universe but of course no one will be around to let you know how it ends. Nonetheless, the universe is a scary place and the way it could possibly end is a time you probably wish you weren’t around. With more studies on dark energy we will unlock more mysteries on the fate of the universe.

 

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