Big Bang cosmology isn’t the only scientific evidence for the universe having a beginning. There are parallel laws of nature that point us to the same conclusion and, again, it is not some earth-shatteringly complicated concept to comprehend. You understand it already because you have to charge your cell phone every night.
A battery holds a certain amount of energy within it and, unless and until you plug it in to recharge it, the battery will eventually go dead. A battery can only hold a finite amount of energy. You can use it up, but you won’t get anymore. As far as we know, the universe is a “closed system” similar to a giant battery … except that it is 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. To put it more formally, here are some principles to understand about this:
- The Law of Conservation of Energy — energy is neither created nor destroyed; it can only be transformed from one form to another.
- The 2nd 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.” 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.
You have a match in your hand. The head of the match is made of combustible material that contains 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 more random dispersal of heat into the air. In other words, it has taken a more “chaotic” form. Entropy has increased.
And 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 potential chemical energy in a single location (like the head of a match). The very idea of such a thing is ridiculous. Thermodynamics only goes in one direction.
So does the universe. Like a giant battery, it contains a fixed amount of energy. As time marches on, the energy inside it becomes more and more useless and becomes more dispersed as the “chaos” level (entropy) of the entire system has increased. At some point, the usefulness of the energy will run out altogether. They call this “heat death” and that is exactly where the universe is headed.
This is a law of nature. It is the basis for the operation of everything from the engine that launches the space shuttle 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 the “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: