Big Bang cosmology isn’t the only scientific evidence that the universe had a beginning. There are parallel laws of nature that point us to the same conclusion. We get one of them from the study of thermodynamics. This is not something that is hard to comprehend. You already understand it because you have to charge your cell phone every night.

A battery contains a fixed amount of energy. You can use that energy but you won’t get any more. If you don’t plug it in to recharge it, the battery will eventually go dead. As far as we know, the universe is a “closed system” similar to a giant battery. But it’s not rechargeable.

Barring some outside influence, this kind of process can only go in one direction. We all recognize that this is how energy works. It’s not a mystery. It’s a simple concept that is based in a couple of natural laws:

• The Law of Conservation of Energy — energy is neither created nor destroyed; it can only be transformed from one form to another.
• The Second Law of Thermodynamics — in a closed system, the total entropy of the system will always increase and this process in irreversible.

So, let’s put these together.

Don’t be freaked out by the term, “entropy.” Think of it as “level of chaos.” Just like the battery, there is only a finite amount of energy in a closed system. The amount of energy cannot be increased; it can only be transformed to a higher level of chaos. An example might help.

To Understand The Second Law Of Thermodynamics, Burn A Match

You have a match in your hand. The head of the match is made of combustible material that has the potential to create a flame. The amount of potential energy concentrated in the head of the match and is fixed. It cannot increase. When you strike the match, the potential chemical energy in the head of the match converts to heat energy in a flame. Then, the heat energy from the flame disperses into the room. Our energy system has gone from a concentrated potential energy source, to a flame, to a random dispersal of heat into the air. In other words, it has taken a more “chaotic” form. When we say that “entropy has increased,” that is all it means.

Here’s the key — the process will not go in the opposite direction. You won’t see the heat content in a room suddenly coagulate into a single flame, and then reorganize that flame into a concentrated ball of chemical energy in a single location (like the head of a match). The very idea of such a thing is ridiculous.

Thermodynamics tells us that energy only goes in one direction

The Universe – A Giant Battery

The universe works the same way. Like a giant battery, it contains a fixed amount of energy. As time marches on, the energy inside it becomes more and more useless as it disperses. The “chaos” level (entropy) of the entire system is always increasing. At some point, the usefulness of the energy will run out altogether. Scientists call this “heat death.” The universe is headed toward heat death.

This is a law of nature. It is the basis for the operation of everything from the engine that launches a rocket into orbit, to the biological machinery that runs every cell in your body. And what it means is that we know the whole system — the whole universe — must have started this energy transforming process when its “battery” was full.

The universe had to have a beginning. And, for the same reasons mentioned in our discussion of the cosmological argument, something outside the known universe must have flipped the switch to initiate the beginning of the process. Listen to Frank Turek’s short explanation for the Second Law …

… and how William Lane Craig connects it to a cosmic beginning: