What is Time?

What is time? Seconds, minutes, hours, even days are all measures of time, but do they define time? I recently read an interested article about Sean Carroll, a physicist who is developing his own theory of time.

Carroll proposes that time is linked to entropy, the theory that the natural order of things moves from order to disorder. Carroll states, "Basically, our observable universe begins around 13.7 billion years ago in a state of exquisite order, exquisitely low entropy. It’s like the universe is a wind-up toy that has been sort of puttering along for the last 13.7 billion years and will eventually wind down to nothing. But why was it ever wound up in the first place? Why was it in such a weird low-entropy unusual state?" Hmm, the universe began in an almost perfectly low entropic state and then moved to disorder and has been moving down that path ever sense? Sound familiar?

Carroll refutes the idea that the universe began with the big band. He states that the big bang was not the beginning; there was something more and something before. He also says the universe is not all that there is; the universe is actually part of something larger. Carroll suggests, "And if that’s true, it changes the question you’re trying to ask. It’s not, “Why did the universe begin with low entropy?” It’s, “Why did part of the universe go through a phase with low entropy?” And that might be easier to answer."

Carroll proposes a multiverse theory, where you have a static universe in the middle. From that middle static universe, smaller universes pop out of the middle universe and travel in different directions, in what Carroll calls, arrows of time. Carroll believes the universe in the middle has no time at all. He states, "There’s different moments in the history of the universe and time tells you which moment you’re talking about. And then there’s the arrow of time, which give us the feeling of progress, the feeling of flowing or moving through time. So that static universe in the middle has time as a coordinate but there’s no arrow of time. There’s no future versus past, everything is equal to each other."

So, the question everyone wants to know is this: what is time in that middle universe? Carroll responds,

"Even in empty space, time and space still exist. Physicists have no problem answering the question of “If a tree falls in the woods and no one’s there to hear it, does it make a sound?” They say, “Yes! Of course it makes a sound!” Likewise, if time flows without entropy and there’s no one there to experience it, is there still time? Yes. There’s still time. It’s still part of the fundamental laws of nature even in that part of the universe. It’s just that events that happen in that empty universe don’t have causality, don’t have memory, don’t have progress and don’t have aging or metabolism or anything like that. It’s just random fluctuations."

In sum, Carroll states, "the whole point of this idea that I’m trying to develop is that the answer to the question, “Why do we see the universe around us changing?” is that there is no way for the universe to truly be static once and for all. There is no state the universe could be in that would just stay put for ever and ever and ever. If there were, we should settle into that state and sit there forever."

Carroll explains,

"It’s like a ball rolling down the hill, but there’s no bottom to the hill. The ball will always be rolling both in the future and in the past. So, that center part is locally static — that little region there where there seems to be nothing happening. But, according to quantum mechanics, things can happen occasionally. Things can fluctuate into existence. There’s a probability of change occurring. So, what I’m thinking of is the universe is kind of like an atomic nucleus. It’s not completely stable. It has a half-life. It will decay. If you look at it, it looks perfectly stable, there’s nothing happening … there’s nothing happening … and then, boom! Suddenly there’s an alpha particle coming out of it, except the alpha particle is another universe."

All of this is interesting and familiar, especially if you read your Bible regularly. I strongly encourage you to read the entire article, and if you have an interest in time, pick up his book,
From Eternity to Here: The Quest for the Ultimate Theory of Time. Blessings!