Welcome to Defenders, the teaching class of Dr. William Lane Craig, today, and excurses

on Natural Theology, Part 13.

For more resources from Dr. Craig, go to reasonable faith.org.

We've been looking at the Kalam cosmological argument, particularly the second premise that the universe began to exist.

And last time we finished looking at the first scientific confirmation of that premise, which is based upon the expansion of the universe.

Now if this weren't enough, there is actually a second scientific confirmation of the beginning of the universe. Now, if this weren't enough, there is actually a second scientific confirmation

of the beginning of the universe, and this one comes from the second law of thermodynamics.

According to the second law, unless energy is being fed into a system, that system will become increasingly disorderly.

Now, already in the 19th century, scientists realized that the second law implied a grim

prediction for the future of the universe. Given enough time, all of the energy in the universe

will eventually spread itself out, evenly throughout the universe. The universe will become

a featureless soup in which no life is possible. And once the universe reaches such a state, no further significant

change is possible. It is a state of equilibrium. And scientists call this state of thermodynamic

equilibrium, the heat death of the universe.

But this unwelcome prediction of the future raised a further puzzle.

If given enough time the universe will eventually stagnate in a state of heat death, then why if it has existed forever is it not now in a state

of heat death? If in a finite amount of time the universe will reach equilibrium,

then why is it not now in a state of equilibrium if it has existed for infinite

time? Given infinite past time, the universe should by now already be in a state of thermodynamic

equilibrium. But obviously it's not. We're in a state of disequilibrium,

where energy is still available to be used and the universe has an orderly structure.

The 19th century Austrian physicist Ludwig Boltzmann presented a daring solution to this problem.

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