# Nature of time

1. Feb 13, 2009

### Parmaanu

Am a new joinee (from India). I have been thinking about time for sometime now (). So here are my questions ... and no, I don't have any background in Physics (apart from senior school level i.e.).

What is nature of time?

How is time created?

When we move to the next measuring unit of time (say a second or a minute) of the very immediate future , how does it come into existance? Initially one might think that this is due to earth's rotation around Sun & its axis .. but then if you think a bit deeper into this, even if the movement doesn't happen ... time is still going to pass .. and since time is passing, it means it is getting created .. and that is the question that I have ... how is time created?

Does time has a beginning and an end?

Was time there before the universe was created ? Or the 00:00 of time started at the time when universe was created?

Did 'time' exist before the big-bang?

2. Feb 13, 2009

### friend

Time is a measure of change. We see things proceed from one state to another and compare this change of state to other, more standard, changes of state, for example, how many waves of light are emitted from excited atom, etc.

The question is whether time as we experience it is fundamental or does it emerge from more basic effects. Could it be that time is a classical property that emerges from quantum mechanics?

In quantum mechanics, electrons (and everything else) take every possible path. And what we observe is an integrated sum of all possibilities. All possible paths exist simultaneously in superposition, and what we observe is the accumulated effect. That means we include paths that go backwards in time, and even paths that travel faster than the speed of light. We use what is called the Feynman Path Integral to account for every possibility. And what this formulation does in effect is add up every possible change from every state to every other state. Each "path" is marked off with some parameter (we call it time) as it moves from one state to the next. Thus, I think at the most basic level (the quantum mechanical level) time is just a mean of keeping track of changes in state, both forward and backward in observable time. But the linear progression we observe is the classical effect that emerges from this quantum mechanical formulation.

Last edited: Feb 13, 2009
3. Feb 13, 2009

### w3390

I think you should check out the book by Stephen Hawking, A Brief History of Time.

4. Feb 13, 2009

### tony134340

To put it in another digestible form, I see it kind of like gravity, although I guess it's nothing like gravity other than the analog I use. Imagine being a solitary person in space and nothing around for millions of miles but you and one planet. You keep heading that direction and to you, that's the only direction there is. There is no way to go away from it and all elementary particles are flowing in that direction too. It's like a river for which we don't have the power to row against because there's nothing we know of to grab on to to propel ourselves in the other direction. Perhaps time may be like a space and everything else around us is headed in the same direction and we just can't out-power it. Maybe, at a later point, it could reverse direction, but may not be an exact replication of what once was, like a river reversing direction or particles forming a planet and billions of years later, due to natural reasons, it's back to particles again. I see it as sort of a malleable material. It may seem uni-direcitonal and im-movable to us with our little physical and intellectual power but on a broader scale, it may just be malleable on another scale.

But malleable in a sense that we could take some clay and mold a shape but no matter how perfect the mold, it will never be a true particle by particle representation of the original. So in that sense, I don't see true time travel to the past by us as possible, even though I hate using the word impossible. But that's another subject which I won't go into.