What Is Time?

We all think we know what time is. We talk about time as though we understand it, but do we?

As a brain exercise, see if you can define time is a sentence or two. It’s not easy.

How did you do?

Most of our experience with time is based on the things that govern our perception of time. A day is a cycle of the sun. (Actually the Earth but you knew what I meant) From sun up to sun up is a day. When we get a day off, it’s a week. When our birthday comes around, it’s a year. When that project is due at work it’s “that’s due already?”

On a different planet, the perception of time would be different. A planet that completed 5 trips around its sun in 365 days would have very short years. If you lived there, you would perceive time differently. But perception isn’t reality. A year is nothing more than a term we use to mean 1 trip around the sun. It has nothing to do with time. For example, if you measured time in terms of travel to a location on earth rather than travel around the sun, it would be somewhat confusing. Let’s use the Empire State Building. How long would it take you to drive there and back? If you live in New York it would take you far less time that it would take me coming from California. Using a travel distance is unreliable unless the distance is fixed.

We could say that an hour is the amount of time it takes to travel 60 miles. But if the speed varies, that definition falls apart.

So what is time? To get to a definition, we need to separate the measurement from the definition. After all, we don’t define water as “something that fills a cup”. That’s merely a means to measure an amount of water. An hour is an amount of time. An hour is not what time ‘is’.

Time is entropy. Entropy, in simple terms, is a degree of disorder. A fresh deck of cards has low entropy. Use those cards and the entropy increases. The cards get out of order. There are other things that happen to the cards. They not only get out of order, they show signs of wear. A fresh deck of cards placed on a table will show signs of entropy even if left alone. The air, light, and gravity are working on those cards. Come back in 100 years and that deck will look little like the deck left on the table. The table might be gone! The building that shelters the table might be gone! That’s entropy.

The 2nd Law of Thermodynamics says that entropy always increases. (I won’t get too complicated) If that’s true, entropy and time are interchangeable.

Since entropy is disorder, wear and tear, breakdown, and erosion, time has a destructive property.

There are big consequences to that. If time is defined by increasing disorder, that means things are always falling apart! It’s true. Time is entropy.