time

[muskan]

what's exactly is time? did it started with the big bang or it existed even earlier? we measure time, but don't know what exactly it is. 

[geordief]

Answer#1     It is just a measurement we can make.

Answer#2     As space is what prevents all things being one undifferentiated object ,so time is what prevents all events from occurring simultaneously.

Answer#3     Time can only be understood in terms of space and vice versa.

Just my attempt(and what I have heard)  ,possibly full of holes.

 

(not sure if "Homework Help " is a good pigeon hole for this question)

Edited September 27, 2017 by geordief

[swansont]

A physics answer is "time is what is measured by a clock"

 

1 hour ago, geordief said:

 (not sure if "Homework Help " is a good pigeon hole for this question)

Agree

[Itoero]

2 hours ago, muskan said:

what's exactly is time? did it started with the big bang or it existed even earlier? we measure time, but don't know what exactly it is. 

Time is imo a property of space.

[Strange]

13 minutes ago, scherado said:

If there's no Matter, then there's no 'Time'.

Well, this makes a change from the (related) "there's no time without movement". 

It seems fundamentally mistaken.

For example, we can produce solutions to the Einstein Field Equations to describe universes with no matter or energy. We can then model how space evolves over time in such a universe.

So it seems that matter may be necessary to measure time but not for time to exist.

But as we live in a universe full of matter, it seems kind of moot.

17 minutes ago, scherado said:

Given our relationship with and to 'Time', if I were to ask, what is the nature of time?, I would not be asking a philosophical question and my answer would be, it is the handmaiden of Matter.

Any question about the (ultimate) nature of anything is, by definition, philosophical. The "handmaiden of Matter" is very poetical, but doesn't really tell us anything scientifically useful.

[geordief]

19 minutes ago, Strange said:

 

For example, we can produce solutions to the Einstein Field Equations to describe universes with no matter or energy. We can then model how space evolves over time in such a universe.

 

Really?  Can you say any more about those  modeled universes? Are they entirely theoretical ?(in layman's terminology)

 

Do they bear any relation at all to any physical situation we could ever encounter? 

 

It is not a heat death scenario is it?

[Strange]

8 minutes ago, geordief said:

Really?  Can you say any more about those  modeled universes? Are they entirely theoretical ?(in layman's terminology)

Do they bear any relation at all to any physical situation we could ever encounter? 

One is the Milne model: https://en.wikipedia.org/wiki/Milne_model

And, not surprisingly, it doesn't behave the same as the universe we live in! (as ours is full of matter) And I'm not sure it could ever have applicability, but they are useful ways of exploring the limits of the theory. One problem with GR is that there are few exact (mathematically solvable) solutions to the equations and those that do exist are approximations (e.g. the ever popular Scharzschild black hole describes an eternal unchanging object in an otherwise empty universe. But that is a good enough approximation for many purposes.

[geordief]

11 minutes ago, Strange said:

One is the Milne model: https://en.wikipedia.org/wiki/Milne_model

And, not surprisingly, it doesn't behave the same as the universe we live in! (as ours is full of matter) And I'm not sure it could ever have applicability, but they are useful ways of exploring the limits of the theory. One problem with GR is that there are few exact (mathematically solvable) solutions to the equations and those that do exist are approximations (e.g. the ever popular Scharzschild black hole describes an eternal unchanging object in an otherwise empty universe. But that is a good enough approximation for many purposes.

Well beyond me to  get into but I do find it interesting to click on the"Talk" tab in the Wiki  page where one can eavesdrop on participants who presumably do know something of what they are discussing.

It can be instructive I feel to listen in to others' disagreements if only to get the lie of the land.

Edited September 28, 2017 by geordief