The Illusion of Time

[studiot]

 

Several different spatial points sharing the same time coordinate simply means that they do, indeed, have the same value for t as their time coordinate

 

Are you saying that this is independent of any (potential) observer.

 

Would that not imply a prefered or absolute reference frame since the t coordinate in one reference frame will be different in another?

[JonG]

 

Are you saying that this is independent of any (potential) observer.

 

Would that not imply a prefered or absolute reference frame since the t coordinate in one reference frame will be different in another?

No, it doesn't imply a preferred reference frame. Whatever reference frame is chosen, provided that it is characterised by orthogonal axes, different points in the spatial dimensions can all have the same time coordinate. That is a consequence of the axes being orthogonal. The different points could have different coordinate values in different frames of reference, but the general statement will be the case for a particular reference frame.

Edited October 8, 2014 by JonG

[michel123456]

What I wrote:

 

By the same time I simply mean sharing the same time coordinate as denoted by the time axis.

 

 

 

 

I am not sure that elfmotat did point that out, but I do disagree that it implies simultaneity. Several different spatial points sharing the same time coordinate simply means that they do, indeed, have the same value for t as their time coordinate. It only implies simultaneity if it is also asserted that these points are observable at the same time.

 

If we consider the x-axis in a spacetime diagram, it is clearly possible for different events to have different x coordinates but have the same time coordinate. What we can't do is observe them all at the same time, so it contains no implication of simultaneity.

That is fully correct.

Draw an object in a spacetime diagram. Not a point object, but an object that extend in space.

How do you draw that?

Is it a horizontal straight line segment?

Or is it a broken segment that follows the diagonals?

 

I think it cannot be a horizontal segment, because as you said, a horizontal segment (absolute simultaneity in dt=0) is not observable.

I think an object in a spacetime diagram is a broken line along the diagonals.

Meaning by that that an object extends both in time & in space.

[TJ McCaustland]

Time is relative, that relativity changes how we perceive it. Time here on earth is often thought of as a very limited resource, and that in many ways in our lives is correct, but if you look at the big picture, it changes, bends, and flexes, all due to physical reality. So if you take a very precise clock (This was used with an atomic clock) and you put it on a jet and fly it around the world, and compare it's time to time to another atomic clock on the ground, the clock that was flown will be ahead several seconds. This phenomena is known as time dilation, and if you take a very large star and you fly around it at high speeds (Just under escape velocity) you find that time "moves" faster. Now time in physical reality should be thought of as a liquid on a sphere that we all float on, the higher up you are the slower you move, and the lower you are the faster you move. This is due to the fact that time is affected by gravity and speed, Men in jets, or men that are deeper in the liquid will move faster (Only slightly) than the rest. and men in orbit around a black hole would move MUCH faster than anyone else because they are moving at speeds near the speed of light. They are VERY deep in the liquid. So do not think of time as something to be perceived but something to be measured. And if you think about it at all do not think about it like so many other people, it is not a straight line with only so many possible outcomes, but think of it as a wibbly, wobbly ball of varying outcomes that eventually loops upon itself.

 

Quote Dr. Who, The 12th doctor (After all everybody hates a plagiarist.)

Edited October 10, 2014 by TJ McCaustland

[michel123456]

By michel123456;

 

You can't occupy T1 and T2 at the same time. That much I accept. (...)

Yes that is pretty much what I mean.

I prefer the concept "mutualy exclusive" because when you say "You can't occupy T1 and T2 at the same time" it looks like introducing "time over time" and many people will come with objections on that.

 

If T1 and T2 are mutually exclusive, it means that when you are at coordinate T2 then you have left coordinate T1 empty.

Which is truly amazing because it opens the door to a new universe.

 

Something like this below (iI have posted this before somewhere on this Forum)

 

This is a kind of spacetime diagram, time is on the vertical axis, space is on the horizontal axis.

We are the black dot at the intersection of the time & space axis. Note that the space axis travel with us in time.

The black dots are objects that travel with us in time. These are the objects that we can observe through our yelescopes. The black dots represent the universe as we see it.

 

The red dots are (speculative) objects that travel "behind us" in time. The red dots belong to our universe but we cannot observe them, nor interact with them.

 

Click on the image, it is a gif

 

 

Note to Swansont: a photograph is an object that travel in time together with the central black dot. It is not an object that stay in time.

Edited October 12, 2014 by michel123456

[swansont]

 

Note to Swansont: a photograph is an object that travel in time together with the central black dot. It is not an object that stay in time.

 

But it records what happened at that time, and confirm the state of things at the place and time recorded.

[michel123456]

 

But it records what happened at that time, and confirm the state of things at the place and time recorded.

Yes. I didn't say the contrary.

I do not question wether an event from our past happened or not. The question is rather wether this event is somehow "frozen" in time, or if the spacetime coordinate where this event happened is now open for another event to happen.

 

Note that this hypothetical "new event" would not be observable by us.

 

All this follows from the idea of "moving" through time. in replacement of the standard concept that ressembles an extrusion, where objects translate from event to event keeping a kind of "existence" "frozen" in time.

[swansont]

Yes. I didn't say the contrary.

I do not question wether an event from our past happened or not. The question is rather wether this event is somehow "frozen" in time, or if the spacetime coordinate where this event happened is now open for another event to happen.

 

Note that this hypothetical "new event" would not be observable by us.

 

All this follows from the idea of "moving" through time. in replacement of the standard concept that ressembles an extrusion, where objects translate from event to event keeping a kind of "existence" "frozen" in time.

 

It depends on what "my ancient set of coordinates is empty" means. If someone was in Paris atop the Eiffel Tower at noon on July 1, 2010, then that doesn't stop being true at some later time. They aren't there now (at whatever time it happens to be) but they were there then. At whatever (x,y,z,t) represents that.

 

It's not open for another event, because that's not how time works.

[davidivad]

time is yet another dimension along with length and width starting at the planck scale.

so, time is a real measureable aspect. mathematically, you can present space without the dimension of time. this means everything has to be stripped of all those time frames and placed in one frame wich represents the basic unit of time. what do you get? "frozen time"... clearly we require that we have more room to move in than the plank length for time to "move" so this is only a verry useful exercise in math. in other words, time moves on reguardless of how you choose to view it. interestingly enough, massless particles have the advantage of being able to share a position. i think the best way to think of things is that the vacuum of space contains all virtual possibilities that can be had. particles are nothing more than interactions in and of themselves. they are merely events.

to say that all probable outcomes of an event exist in another universe detracts from the idea that space is simply full of nothing which is representative of everything in existence. how about them apples...

question: can pigs fly in another universe?

answer: if all conditions are met in this one....

 

all that from bubbles in a bottle of shampoo?

Edited October 14, 2014 by davidivad

[jajrussel]

I think I understand what people are saying about time, but I tend to have trouble understanding why they are saying it, sometimes.

 

For instance someone can be in front of me, and someone behind me, but why imply that the statement means that time is different for them based simply on that statement?

 

One may be two minutes in front of me, and one may two minutes behind me, but if the rate of change is the same for each of us then time dilation should be the same for each of us. It would seem that each of us would determine that we each are traveling at the same speed, and there should be no apparent time dilation.

 

If we were to determine that each has a different rate of change at what point do different rates of change become time dilation?

 

Why does neer C speeds cause time dilation while 60mph does not?

[JonG]

Why does neer C speeds cause time dilation while 60mph does not?

 

A relative speed of 60mph would give rise to time dilation, but the effect would be very small. Effects predicted by Special Relativity depend on the ratio v/c where v is the relative speed being considered and c is the speed of light. If v is very small compared to c, this ratio will be very small and so will the effect - time dilation in this case.

[swansont]

 

A relative speed of 60mph would give rise to time dilation, but the effect would be very small. Effects predicted by Special Relativity depend on the ratio v/c where v is the relative speed being considered and c is the speed of light. If v is very small compared to c, this ratio will be very small and so will the effect - time dilation in this case.

 

Driving across the US it will give rise to about a 1 ns difference. You'd have to account for that if you had a good atomic clock.

http://blogs.scienceforums.net/swansont/archives/6

[JonG]

 

Driving across the US it will give rise to about a 1 ns difference. You'd have to account for that if you had a good atomic clock.

http://blogs.scienceforums.net/swansont/archives/6

 

I do have one, of course. But I don't wear it often.

[jajrussel]

 

A relative speed of 60mph would give rise to time dilation, but the effect would be very small. Effects predicted by Special Relativity depend on the ratio v/c where v is the relative speed being considered and c is the speed of light. If v is very small compared to c, this ratio will be very small and so will the effect - time dilation in this case.

This is the sense I got from the thought while thinking about it.

 

This would seem to mean that if earth were hurling through space art near C then my speedometer on the car would have no trouble determining 60mph as I drove down the highway.

 

This would seem to mean that time is as invariant as C. If it were not it would seem that time dilation would be impossible predict or observe.

[studiot]

 

One may be two minutes in front of me, and one may two minutes behind me, but if the rate of change is the same for each of us then time dilation should be the same for each of us. It would seem that each of us would determine that we each are traveling at the same speed, and there should be no apparent time dilation.

 

 

 

This would seem to me to be a correct statement.

 

Let us say you are referring to your 60mph road speed and you three are driving in convoy.

 

The point is that the velocity v in the formulae is not 60mph, it is the relative velocity between your three convoy cars, which is precisely zero.

This, of course, leads to zero time dilation between their clocks observed by the three drivers. So they measure their transit time across America as 180000 seconds.

 

However since swansont was standing talking to JonG by the side of the road, their clocks measured a transit time of

180000.00000001 seconds.

Edited October 15, 2014 by studiot

[jajrussel]

Okay, I am not sure where the 180000 seconds comes from, but I understand the implication of the 180000.00000001.

 

As I read the back log of the thread I am not certain that time needs an observer, actually I don't think it does, but we three could hardly know that our relative velocity is zero if at least one of us doesn't make the observation.

 

Time dilation though, seems to be dependent on two observations. The three of us are unable to make that determination simply based on our relative velocity of zero.

 

Which by the way confuses me where you point out that zero and not sixty is the relevant point in the equation. If what you mean is that zero divided by c means no time dilation then I am not as confused as I think I am.

 

Though I see the point of Swansont and JonG making an observation as they stand along side the road their observation is only going to confuse me as I determine how much fuel we need for the return trip.

Edited October 15, 2014 by jajrussel

[JonG]

This would seem to mean that if earth were hurling through space art near C then my speedometer on the car would have no trouble determining 60mph as I drove down the highway.

 

 

Regarding the above statement, the speed at which the earth is moving wouldn't have any effect on the reading from the speedometer.

 

For time dilation to be observed, two frames of reference moving at different speeds are required, and what is being observed should be an interval in time. As already mentioned, one frame of reference could be the frame of reference of the car, and another could could that of someone standing on the ground watching the car go by. These frames of reference would be moving relative to each other. The time interval could, for example, be the time it takes for the driver's hand to move from the steering wheel to the gearstick. Observer's in the two different frames of reference would differ (by a very small amount, because of the low speed of the car) in their view of how long this takes.

 

However, in the case that you refer to above, both the driver and the speedometer are in the same frame of reference - the frame of reference of the moving car - so time dilation wouldn't affect what is observed by the driver within the car. Further, what is being observed - noting the reading on the speedometer - isn't a time interval but a single event (unless you want to specify how long it takes to read the speed on the speedometer - then it could be regarded as an interval). In either case, what the speedometer reads would not be affected.

Edited October 15, 2014 by JonG

[swansont]

This is the sense I got from the thought while thinking about it.

 

This would seem to mean that if earth were hurling through space art near C then my speedometer on the car would have no trouble determining 60mph as I drove down the highway.

 

This would seem to mean that time is as invariant as C. If it were not it would seem that time dilation would be impossible predict or observe.

 

The existence of time dilation and the fact that it's been measured means it's not invariant. Observers in relative motion will not agree on the time. Both will agree on a measurement of c, though the details of their measurements and calculations might not be identical.

[jajrussel]

Both of you are explaining what I am thinking so much better than I can.

 

When I use the term invariant in regard to time I mean that the results are reasonably predictable. Your measurements standing along side the road will be different than mine in the car.

 

Now, if we take the measurements again and the only seemingly different variable is how fast the earth is moving we should all get the same measurements as before, because space/time dilation will adjust all the other variables within the system. Your calculation will be one nano second different than mine.

 

In essence how fast the earth is moving isn't a variable to be considered. Time dilation assures that our measurements do not change. This is what I mean by time is invariant.

 

I am not a chart person. I can not draw a chart that shows what is happening, but I suspect that if such a chart were drawn that we should be able to fold it and the resulting pattern would be the same as it was before folding.

Edited October 15, 2014 by jajrussel

[studiot]

@jajrussel

 

We are all agreed that for a relative speed of 60mph the difference is very slight.

 

I have based my figures on the travellers measuring the distance across america as exactly 3000 miles and therefore measuring their transit time as 180000 seconds and their speed as 60mph.

 

You have mentioned 'invariants'.

 

Invariants means the same for all observers, not just the two in relative motion but others (eg in a helicopter flying above the vehicles)

 

There is only one such invariant that is c the speed of light.

 

However the 60 mph is the same for both the observers in the cars and those at the side of the road.

 

Both observers subject to the same relative motion will observe the same speed (apart from the opposite signs) ie 60mph.

 

So this is not exactly invariant but it is the same for both observers here.

 

So swansont and JohnG will observe the transit time being a tad longer (as noted) and they will measure the distance across America as a tad longer than 3000 miles so that the figure of exactly 60mph is maintained.

 

It is important to realise that both distance and time must change to maintain this equal value of relative velocity.

[jajrussel]

Considering your statements my use of the word invariant with regard to time was a poor choice.

 

I have this desire to say that one observation is more accurate than the other, but it seems that if the one nano second represents time dilation then both observations have to be accurate. Well, reasonably accurate.

 

If one nano second represents difference then all observers have to be in a state of time dilation. Would you agree?

[studiot]

 

If one nano second represents difference then all observers have to be in a state of time dilation. Would you agree

 

Yes and no.

 

There is not "a (single) state of" time dilation, that implies too much (or perhaps too little?)

 

We call the measurement made by an observer about his own time (his) "proper time".

 

Any other observer in the universe would observe a dilated time if that second observer was in steady motion relative to the first.

 

Since there are an infinite number of possible relative motions (all not greater than c) there are an infinite number of possible "states of dilatation".

 

It does not actually need a real observer for this to be true, just the fact that there could be such an observer.

Edited October 16, 2014 by studiot

[TJ McCaustland]

Time is relative, that relativity changes how we perceive it. Time here on earth is often thought of as a very limited resource, and that in many ways in our lives is correct, but if you look at the big picture, it changes, bends, and flexes, all due to physical reality. So if you take a very precise clock (This was used with an atomic clock) and you put it on a jet and fly it around the world, and compare it's time to time to another atomic clock on the ground, the clock that was flown will be ahead several seconds. This phenomena is known as time dilation, and if you take a very large star and you fly around it at high speeds (Just under escape velocity) you find that time "moves" faster. Now time in physical reality should be thought of as a liquid on a sphere that we all float on, the higher up you are the slower you move, and the lower you are the faster you move. This is due to the fact that time is affected by gravity and speed, Men in jets, or men that are deeper in the liquid will move faster (Only slightly) than the rest. and men in orbit around a black hole would move MUCH faster than anyone else because they are moving at speeds near the speed of light. They are VERY deep in the liquid. So do not think of time as something to be perceived but something to be measured. And if you think about it at all do not think about it like so many other people, it is not a straight line with only so many possible outcomes, but think of it as a wibbly, wobbly ball of varying outcomes that eventually loops upon itself.

 

Quote Dr. Who, The 12th doctor (After all everybody hates a plagiarist.)

Any objections?

[studiot]

 

So do not think of time as something to be perceived but something to be measured.

 

Well I like this bit.

[TJ McCaustland]

Thanks