What is Time?

[rogue06]

ya know, if I could keep time in a bottle...

The first thing that I'd like to do
Is to save every day...

[JonF]

Pardon my ignorance, but I've never understood why time is grouped with length, width, and breadth as a dimension. It seems obviously of a different sort than those dimensions. What am I missing?

The fact that the "grouping" naturally "falls out" of the theory of Relativity, which has been established as one of the most-tested theories of all time.

It is different from the spatial dimensions, but it belongs with them. The formula for distance in space is just Pythagoras' theorem: distance = sqrt(x^2 + y^2 + z^2). IN space-time the distance is sqrt(x^2 + y^2 + z^2 -t^2).

Yup, weirder than a snake's suspenders. But a darned good model of how the Universe works.

[klaus54]

The fact that the "grouping" naturally "falls out" of the theory of Relativity, which has been established as one of the most-tested theories of all time.

It is different from the spatial dimensions, but it belongs with them. The formula for distance in space is just Pythagoras' theorem: distance = sqrt(x^2 + y^2 + z^2). IN space-time the distance is sqrt(x^2 + y^2 + z^2 -t^2).

Yup, weirder than a snake's suspenders. But a darned good model of how the Universe works.

Or sqrt(x^2 + y^2 + z^2 -[ct]^2) if you want to consider time as the distance light travels in a time t.

[Sparko]

The first thing that I'd like to do
Is to save every day...

like a bottle of rum and again I would drink it with you!

[Carrikature]

It still is not physical - correct, and it still effects the physical? And I'm not sure if those who hold to the B-Theory of time would agree that it is an emergent property of entropy. Since in the B-Theory time is actually static. From what I understand.

It's not, at least not according to McTaggart's original work on the subject. I need to respond to that thread...

[JonF]

Or sqrt(x^2 + y^2 + z^2 -[ct]^2) if you want to consider time as the distance light travels in a time t.

You do have to use consistent units.

[Truthseeker]

Or sqrt(x^2 + y^2 + z^2 -[ct]^2) if you want to consider time as the distance light travels in a time t.

The "c" constant is only necessary if t is measured in seconds, and x,y,z are measured in say meters. One can adopt measurement standards such that the unit for t is the same as for x, y, and z (special relativity). Then if the unit for t is taken to be 1 second then so is the unit for x, y, z (divide x by c, e.g., if the original spatial unit happens to be, say, the meter [c measured in meters/second]).

[Truthseeker]

What the heck is meant by physical? If something like energy affects the thermodynamics of a hot object, why on earth is energy to be regarded as n-o-t physical!? eta and what the heck happened to E = mc²!?

[shunyadragon]

This is a quote from The Lurch's thread:



So my question is, what is time? I mean it is not made of physical things correct?

No.

Particles and such?

No

And if it is not physical then how can something physical like gravitational waves influence or have an effect on time - which is non-physical.

Gravitational waves are not time. They are observed as the relationship between energy, and matter in time and space which is the relationship between space and time in our universe.

[klaus54]

You do have to use consistent units.

Using -(ct)^2 gives the metric (Minkowski) in length units.

[klaus54]

What the heck is meant by physical? If something like energy affects the thermodynamics of a hot object, why on earth is energy to be regarded as n-o-t physical!? eta and what the heck happened to E = mc²!?

Gobble-dee-gook

[Truthseeker]

Gobble-dee-gook

Are you just kidding? If not, please explain what you think "physical" should be defined.

[firstfloor]

So my question is, what is time? I mean it is not made of physical things correct? Particles and such?

[seer]

Well I would say that an electron is clearly physical, has physical properties - when time does not.

Time and matter are linked by the Principle of Equivalence of gravity and acceleration and the uniformity of the speed of light in all reference frames.

Yes time and matter are linked - the question remains, how does something non-physical effect the physical.

[firstfloor]

Well I would say that an electron is clearly physical, has physical properties - when time does not.

Yes time and matter are linked - the question remains, how does something non-physical effect the physical.

What is a clock? Something physical, that vibrates, that keeps time. Time is just about counting vibrations of a physical object.