Heat Death of the Universe

Heat Death of the Universe

The science of your breakfast cuppa and a whole lot more with Mizu Nishikawa-Toomey

Why does milk gradually mix itself with your tea to form the homogeneous beige colour? Why does it not remain in a small white pool on top?

This is the second law of thermodynamics at work: the amount of disorder in a system will always tend to increase. In other words, energy and matter are constantly being dissipated.  The high concentration of milk in the tea can be thought of as a cluster of energy and matter, and that cluster naturally becomes spread out evenly throughout the tea.

Some physicists even argue that the concept of time is defined as the direction that disorder increases. This would mean that a decrease in disorder of a system would be equivalent to the reversal of time – which is, of course, impossible.

In 1851, William Thomson First Baron Kelvin speculated that if energy and matter were constantly being dispersed in space, we might reach a point where no life form can exist due to the large separation of atoms and energy. This is known as the “Heat Death” hypothesis.

Stars in our universe are no exception to the laws of thermodynamics. Stars are constantly dissipating energy. Lighter elements in the periodic table can release energy when they undergo fusion and in doing so, turn into heavier elements. This energy is the source of heat and light from the stars. Eventually, when the star is composed of heavier elements, it will burst and scatter the particles away from its centre, or shrivel down in to a dense cold dwarf star.

New stars can form due to the dust produced from the explosion of the previous star. But what happens when all of the elements in our universe are extremely heavy elements, which no longer release energy when they undergo fusion?

In other words, what if there were no longer any stars in the universe? The sun produces a constant supply of light which feed our plants and keeps the earth at an optimum temperature. If no stars remained in our universe there would be no potential for any new life forms. There would not be a high enough concentration of energy or matter in one location, as it would have dispersed itself throughout the massive expanse of the universe.

To make matters worse, the universe is thought to be expanding, creating an increasingly larger expanse for the dispersion of energy and matter. Is this the fate of the universe?  It could be argued that the laws of thermodynamics only work on a small scale. The role of gravity in thermodynamics is not completely understood, as these laws are more commonly used on a molecular scale. So it may not be appropriate to apply these rules to such a large scale entity as the universe.

The fate of the universe in billions of years’ time is still not known. The laws of thermodynamics seem to be consistent with what we are observing on the large scale of things. But there are many complex systems at work between matter and energy in our universe. The laws of thermodynamics cannot govern everything.

Featured image credit: NASA / WMAP Science Team

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