Is Time Necessary?

[JohnF]

Can anyone can tell me if time is necessary.

 

It's certainly convenient but all it seems to be is just that; convenient.

 

Has it got any purpose other than to make it easier to measure the difference between events without having to directly refer to spatial co-ordinates, velocity, acceleration and change?

 

I am wondering if it is just an abstract created by humans to help us understand reality; but in reality time does not exist.

[insane_alien]

well, if you look at relativity, you'll see that its a dimension. so asking if you can ignore time is like asking if you can ignore up and down or anything off to the side of you because you don't believe the side is necessary and its just a conveinient trick.

[JohnF]

well, if you look at relativity, you'll see that its a dimension.

 

But is it really a dimension or has the dimension of time been invented?

[insane_alien]

no, its really a dimension.as you speed up the dimensions rotate into each other. so you have time becoming space and space becoming time.

 

its also a dimension in the coordinate form. for two objects to collide they need to have the same x,y,z coordinates but also the same time coordinate. its no good if they have the same x,y,z coordinates if one object has them at 1,000,000,000 BCE and object 2 comes flying along tomorrow.

[JohnF]

That's an interesting example insane_alien but you are using time to 'prove' time. What I would like you to do is prove time without reference to it.

 

In your example you refer to the two objects having to be in the same time co-ordinates. But if there is no such thing as time then they only need to have velocity, trajectory and spatial co-ordinates that would cause them to collide. By introducing a time co-ordinate have you not changed the spatial co-ordinates without changing the trajectory or velocity?

[swansont]

Velocity includes time in it - it's a rate. You're just moving the problem elsewhere. Time is orthogonal to spatial coordinates; as such there's no amount of fiddling you can do to have the spatial coordinates describe the time coordinate.

[JohnF]

Velocity includes time in it - it's a rate.

 

You're right, but could velocity be described as the product of force applied to mass? You could then describe two objects at rest in space and give their co-ordinates. Now apply force to each object so that the objects move in a direction that will cause them to impact. These two events, original location and collision, can be described without the need for time.

[Klaynos]

You're right, but could velocity be described as the product of force applied to mass? You could then describe two objects at rest in space and give their co-ordinates. Now apply force to each object so that the objects move in a direction that will cause them to impact. These two events, original location and collision, can be described without the need for time.

 

The unit of force is Kg m /s/s Which a very very simple unit analysis will tell you that it requires time. You also get acceleration out of F=ma so you then need to apply an equation to the acceleration (which will included time) to get velocity. You can't get it out of the maths.

[insane_alien]

you do know that force is kilogram-metres per second^2 don't you? it depends on time. also, this means that if you fired any two objects towards the same spatial coordinates then they will ALWAYS collide. this is obviously not true as two people can walk through a door in different directions without colliding. if the universe only had 3 spatial dimensions then there would be a collision. if there is time then it is possible.

[JohnF]

You can't get it out of the maths.

 

I'm not trying to get out of the maths. What I'm trying to do is decide if time is a real thing, not just a concept. Space exists but the units we use to measure it are just abstract. So what I am asking is does the dimension of time exist or is the measurement of time just an abstract to allow us to more easily understand space, which has caused us to conclude that the dimension of time is real.

 

Is it really impossible to describe force or accelleration without time? All time is doing in the equation is providing a relative position in space between two events.

[JohnF]

this is obviously not true as two people can walk through a door in different directions without colliding. if the universe only had 3 spatial dimensions then there would be a collision. if there is time then it is possible.

 

Have you not used time to move them to different co-ordinates? If they are both the same distance from the door at the same time then they will collide.

 

But if they are the same distance from the door at different times they will not collide. This is the same as saying they are at different distances from the door at the same time so they will not collide.

 

Please be patient with me as I only thought about this a couple of hours ago. I ended up posting here because I couldn't get my head around questioning time without using time.

[ajb]

In physics we are almost always interested in how things change was we vary some parameters. Often this would be time.

 

Unless we are dealing with things that don't change in time, I cannot see how we could get rid of it, i.e. have no dynamics.

 

Of course in relativity we mix up space and time, so we can think of space and time as playing the same role. This is ok.

 

We can even think of generalising mechanics to have more that one time, that works. But no time, I just can't see how that would work.

 

To Swanshot; is that strictly true what you said? I mean, even on [math]\mathbb{R}^{2}[/math] thought of as a (trivial) fibre bundle, that is one copy for time and one for space there exists diffeomorphisms that are not bundle automorphisms and hence destroy the distinction between space and time.

[Gypsy Cake]

Space coordinates can only be used to describe everything's position at one specific time. And it would seem that other useful units contain time.

 

As a further question, may I ask, if is possible to have a fourth space dimension?

I don't know if anyone read that thread on the tenth dimension. But that was using time as the fourth dimension...then as the higher dimensions the idea that there are an infinity number of ways things can happen and then moving between these. Are all dimensions above the third likely to be non-spacial?

 

Thankyou.

[Klaynos]

[math] v = \frac {dx}{dt}[/math]

[math] a = \frac {dv}{dt}[/math]

 

Time is stuck in there very firmly.

 

Seconts, mins etc. are the same as the meter they are just our abstract measurement system, but time itself is a dimension, as real as the 3 spacial dimensions.

[JohnF]

Hello ajb,

 

Can you think of an example where only two changes occur, one of them being time? This might help me understand better.

[Klaynos]

Space coordinates can only be used to describe everything's position at one specific time. And it would seem that other useful units contain time.

 

As a further question, may I ask, if is possible to have a fourth space dimension?

I don't know if anyone read that thread on the tenth dimension. But that was using time as the fourth dimension...then as the higher dimensions the idea that there are an infinity number of ways things can happen and then moving between these. Are all dimensions above the third likely to be non-spacial?

 

Thankyou.

 

In normal circumstances no, only 3 spacial dimensions. But there are some 'theories' around such as string theory that requires considerably more dimensions, but these are very 'curled up' and therefore in the classical world they cannot be noticed.

[insane_alien]

Have you not used time to move them to different co-ordinates? If they are both the same distance from the door at the same time then they will collide.

 

But if they are the same distance from the door at different times they will not collide. This is the same as saying they are at different distances from the door at the same time so they will not collide.

 

Please be patient with me as I only thought about this a couple of hours ago. I ended up posting here because I couldn't get my head around questioning time without using time.

 

well, can you provide an alternative way to explain movement without a dimension that performs the exact same function as time?

[JohnF]

well, can you provide an alternative way to explain movement without a dimension that performs the exact same function as time?

 

I would need to use time to explain that. It's just whether it's a dimension or not that bothers me.

[Gypsy Cake]

In normal circumstances no, only 3 spacial dimensions. But there are some 'theories' around such as string theory that requires considerably more dimensions, but these are very 'curled up' and therefore in the classical world they cannot be noticed.

 

And would these extra dimensions be spacial or non-spacial?

Or is it undecided?

[insane_alien]

okay, back to the doors but we'll simplify it further.

 

no two objects can exist simultaneously in the same space. if we take away time then we have no two objects can exist at the same coordinates.

 

since. for practical experience, we see objects passing through the same coordinates all the time. (the doors were meant to be an example of this) then there must be another dimension to account for this. we call it time.

 

it really can't be made much simpler without losing meaning.

[JohnF]

no two objects can exist simultaneously in the same space. if we take away time then we have no two objects can exist at the same coordinates.

 

But in an expanding universe all objects are moving so there is never the opportunity for two objects to occupy the same space.

[Klaynos]

It is a thing in which we travel, what is it if not a dimension? (and the answer is not 'a car' )

[Gypsy Cake]

eerrrrrrrrr....TIME?!

was I supposed to answer that? lol.

[JohnF]

It is a thing in which we travel, what is it if not a dimension? (and the answer is not 'a car' )

 

Perhaps it's an effect. I don't really like the idea that it is something we travel in or through. It's more like something that we witness.

[insane_alien]

no we travel through it. we can slow down the passage of time (by going faster through the other three dimensions ironically) so it is something we travel through.

 

and reality doesn't care what you think. reality does what IT wants. not what YOU want.