What is Thermal Equilibrium?

Imagine there is some hot coffee in a heat-blocked receptacle. Of course, this coffee will be cooled by the atmosphere and will cool rapidly. But the heat change did not occur only in the coffee. The surrounding atmosphere definitely became warmer. In the end, their temperatures will be equal. We call this condition, "Thermal Equilibrium."

From the example above, you can understand that temperatures of several substances that have different heat (coffee and the atmosphere) change towards the same temperature in an enclosed space (heat-blocked receptacle).

The universe is also an enclosed space. In that enclosed space, everything is exchanging heat energy. So, by defining the universe as an enclosed space and the elements such as stars as the substances with different temperatures, we can say that the whole universe is moving towards thermal equilibrium, just like coffee and the atmosphere.

The Universe in Thermal Equilibrium

Fusion reaction

So, what kind of physical phenomena does the universe go through in order to reach thermal equilibrium? Inside the stars, for example the sun, the inner-substances form nuclear-fusion due to its own gravity, and thus the stars emit an enormous amount of heat into universe. As a result, the heavier atoms increase in number in the universe.

Therefore, light elements such as hydrogen that formed most of the atoms in the early stages of the universe decreased rapidly, and the heavier elements such as iron multiplied. As the result of this, there is a possibility that in the future, the universe will be filled with heavy elements that are unlikely to produce energy, and there will be no reaction in universe.

In the condition where no reaction is occurring and the universe is filled with heat, when it is not in the state of thermal equilibrium, the universe dies and we call this the hot death of the universe. A universe where no stars are formed will consist only of white dwarves, neutron stars and black holes, and it is expected that this condition will arrive in the next 100 trillion years.

The Universe After Hot Death

By the time the universe reaches the hot death, every galaxy will consist only of white dwarves, neutron stars, and black holes. In the galaxy, if by any chance two stars come near each other, either of those may gain a tremendous amount of energy and jump out of the galaxy. This means that energy was taken away from the galaxy, so the galaxy becomes smaller. If this phenomenon continues for a great length of time, the galaxy will get smaller and smaller.

So the galaxy that becomes smaller in this way, consequently gets swallowed by the black hole and transforms itself into a massive black hole. Therefore, it is expected that in 10 quadrillion years, this universe will be the world of gigantic black holes and wandering stars that jumped out from the galaxy.

The Universe in Darkness

And after a long period of time, matter disappears. Matter consists of atoms and those atoms consist of neutrons, protons, and electrons. But those atoms don't necessarily remain stable forever. After a long period of time, there is a possibility that neutrons and protons change into particles called "positrons" that have the opposite electric charge of electrons. Then particles with positive charge and particles with negative charge attract, so positrons and electrons attract to form an atom called positronium.

Positronium

Positronium, if produced on the earth, is an atom that is so unstable that positrons and electrons collide and disappear in a millionth of a second. But the future universe will expand and keep increasing endlessly, and the density of the substances in the universe will become as little as zero, so that positronium in the future universe will have the distance of more than 10 billion light years between one electron and positron. Therefore the probability of electrons and positrons crashing into each other will be close to none, so positronium can exist in a stable condition.

Evaporating Black Hole

It is important to understand the evaporation of a black hole. Substances around a black hole such as gases get totally swallowed by it, so the area around a black hole becomes a vacuum. However the black hole's gravitational energy affects this vacuum and this energy is not zero, so this is called a false vacuum. Therefore, a pair of virtual particles can exist. And of course, the black hole that swallows anything gulps these virtual particles too.

When a bullet is shot from a gun, there is a strong shock towards the opposite direction of the bullet. If the black hole swallows only one of the pair of a virtual particle, the other half flies away because of the shock.

Here, the energy that caused the formation of these virtual particles, was the gravitational energy of the black hole. This gravitational energy was taken outside the black hole by these phenomena. We mean that black hole gets smaller by swallowing the virtual particles and loosing the equivalent amount of gravitational energy. This is the evaporation of the black hole. The evaporation gets more vigorous as the black hole decrease in size, and it is said that it glows like supernova explosion.
To the animation of Evaporating Black Hole by Shockwave

A Life-Form by Positronium

There is a possibility in the far future that, because of the energy gained from the black hole, a life form made from positronium will be born. That life form would consist of positronium and would be the size of 10 billion light years big. So for example, if there was a head, then what is felt by a part of the body would take 10 billion times 10 billion light years to travel to the head.

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• Test - Ikuya Yamada (Administrator) 08/19/99 02:58:02 - [Others] (0)