Monday, 12 March 2012

Eternity and Thermodynamics

The three laws of thermodynamics were originally about heat engines, expanding gases and changes between different states of matter (gas, liquid, solid). Later they were reformulated to apply to all of nature, i.e. the whole universe – everything from a small group of elementary particles to a balloon full of air to a cluster of galaxies. Here they are:

1st Law. Energy is neither created nor destroyed. This means that the total amount of energy in the universe is constant. Energy can be converted to mass and vice versa, and so one could restate the 1st law as the total amount of energy/mass in the universe is constant. (NB: energy can be expressed in units of mass or vice versa using Einstein’s famous E = Mc(squared) formula, where c is the speed of light in a vacuum.)

2nd Law. Any closed physical system becomes more disordered with time. The amount of disorder is usually quantified as entropy. An example would be a small pulse of coloured gas squirted into a thermally insulated jar: as time goes on it is seen to expand to fill the whole jar. Its molecules, being more spread out, form a more disordered, higher entropy system than the small pulse. (A consequence of the higher entropy is that the system is less able to do useful work e.g. drive a miniature turbine in the jar.)

3rd Law. It is impossible to reduce the temperature of a system to absolute zero degrees in a finite number of operations. (Absolute zero = 0 deg K = minus 273 deg C.)

I invite you to consider the consequences of each of these laws if we assume the universe to be eternal, i.e. to have existed for an infinite amount of time.

1st Law in an eternal universe
The total amount of energy would have to be infinite because an eternal expanding universe would have to be infinite in extent. However, as is pointed out in   infinity, eternity and cosmology,   infinity is a meaningless concept.  (NB: the universe is manifestly not static so it would have been expanding or contracting for an infinite time. If contracting it would not now exist.) This would mean the the 1st Law was meaningless but our observations confirm that it is meaningful.

2nd Law in an eternal universe
Since the natural order, i.e. the universe, is a closed system, it would be in a state of total disorder after an infinite time. In an eternal universe an infinite time has already elapsed so everything should be as disordered as is conceptually possible and we should not be here.

3rd Law in an eternal universe
Presumably the entire universe would be at absolute zero since there would be time for an infinite number of operations. Note that every possible event would have had to have occurred in an eternal universe, which would include cooling it down to zero in an infinite number of operations and once it had reached absolute zero, as a closed system,  it would have no way of departing from that state.

A naturalist, i.e.  one who assumes there is nothing outside the natural order, has to assume the universe to be a closed system, otherwise he/she is admitting a supernatural influence.  However, as the above shows by reductio ad absurdium, an eternal universe is not possible.

Therefore the universe was created.

Comments welcome.