Time dilation (part two)

[Damo2600]

(who gives a bug what my name is. It started as a rouse so now it doesn't matter at all.)

[Queso]

i suppose, we were just trying to figure it out.

[Dark Mind]

(who gives a bug what my name is. It started as a rouse so now it doesn't matter at all.)

 

Kind of rude I think, and we care because it would be fairly easy to start another account if your having two people use one right now. It would also give your account a specific identity/personality and we wouldn't be trying to guess which person was posting what.

[C1ay]

(who gives a bug what my name is. It started as a rouse so now it doesn't matter at all.)

No one, as long as you're one person using one account and not 2 or 3 using one account. FWIW, the multiple persona thing does put a ding in your credibility. If we can't trust who or what you claim to be it puts everything you say in question.

[quantum quack]

It probably is wrong at least in part, I'm a very muddle brained individual but concidering I've spent only a small bit triffling with it before coming to the conclusion that "time" does not exsist. So I don't even worry about it. Except in the case that it makes interstellar travel difficult.

 

With good certainty I can say this. Time Dialation is a derived Equation from Length/Distance contraction. Just take a look at the Lorentz equation. In no example of GR or SR does "time" go faster or slower because time is not a measurement of velocity, it's a measurement of distance. It's all about spacetime geometries.

 

consider this outcome just for a minute or two:

 

"as the velocity increases to 'c' it's length contracts to zero and the time it takes to travel this zero distance is eternity."

SRT is much more confusing than you realise I think KAC.

 

The time and length are inversely proportional.

 

If you built a star gate using SRT you could have zero distance between two points in space but it would take for ever to get there.........so whilst time dilation is relative to distance it is inversely so.......

[bumab]

That was the subject of a Stephen King short story, I believe. A kid goes through a jumpgate thing (can't remember what they were called), and when he comes out the other side (instantly to observers), he is really old and insane, because to him it took a basically infinite amount of time to get through. Cool story, I'll try and remember the name of it...

[quantum quack]

That was the subject of a Stephen King short story, I believe. A kid goes through a jumpgate thing (can't remember what they were called), and when he comes out the other side (instantly to observers), he is really old and insane, because to him it took a basically infinite amount of time to get through. Cool story, I'll try and remember the name of it...

so I am correct that time and distance are inversely proportional in SRT when working with dilation and length contraction??

[Damo2600]

Here lies the problem I was having.

 

If I am heading away from the big clock in the sky, and the clock is stationary, it will take longer for the light to reach me so the seconds tick more slowly. The reverse would mean the seconds tick more quickly. If I am stationary and the clock is moving it matters not because whether I am moving or the clock is moving as long as the distance is proportionately equal then the clock will appear to tick in exactly the same manner. So how fast the clock ticks is directly proportionate to the distance between myself and the clock.

 

If a light is bouncing between two stationary positions and I move closer towards it I will see it move at the speed of light. In this case I would be moving from a slower time difference to a less, slower time difference. When I reach the stationary position and stop there will be no time difference.

 

I will experience time dilation and length contraction however the amount is decreasing. If I keep accelerating past the stationary light bouncing I will experience equal length contraction or time dilation as I race past if I am moving at a constant.

 

At exceptionally long distances and/or high speeds you will easily notice another time dilation where time actually does slow down. If you have a clock and are moving toward the big clock in the sky, at high speeds, you will notice that your clock is no longer equal to the big clock when you reach a stationary position next to the big clock. Why this happens I have no idea?

 

Josephine (sorry about the rouse)

 

I think relativity with regard to the speed of sound is a lot easier to understand because the speed of sound is more observable for the beginner. If a man chops wood 200m from you you don't hear the sound for a moment. The closer you get the less time difference there is. The further away you get the longer the sound takes to get to you.

[xersan]

Here lies the problem I was having.

 

If I am heading away from the big clock in the sky, and the clock is stationary, it will take longer for the light to reach me so the seconds tick more slowly. The reverse would mean the seconds tick more quickly. If I am stationary and the clock is moving it matters not because whether I am moving or the clock is moving as long as the distance is proportionately equal then the clock will appear to tick in exactly the same manner. So how fast the clock ticks is directly proportionate to the distance between myself and the clock.

 

If a light is bouncing between two stationary positions and I move closer towards it I will see it move at the speed of light. In this case I would be moving from a slower time difference to a less, slower time difference. When I reach the stationary position and stop there will be no time difference.

 

I will experience time dilation and length contraction however the amount is decreasing. If I keep accelerating past the stationary light bouncing I will experience equal length contraction or time dilation as I race past if I am moving at a constant.

 

At exceptionally long distances and/or high speeds you will easily notice another time dilation where time actually does slow down. If you have a clock and are moving toward the big clock in the sky, at high speeds, you will notice that your clock is no longer equal to the big clock when you reach a stationary position next to the big clock. Why this happens I have no idea?

 

Josephine (sorry about the rouse)

 

I think relativity with regard to the speed of sound is a lot easier to understand because the speed of sound is more observable for the beginner. If a man chops wood 200m from you you don't hear the sound for a moment. The closer you get the less time difference there is. The further away you get the longer the sound takes to get to you.

 

 

 

There is also "time contraction" in SR. In the theory of SR, the source follows the light always. Because in the train experiment, it was set so; the source takes place at the end of train and light goes away to the same direction of train. The source and the light travel to the same direction. But It is possible that, the light can go to opposite direction of its source.If this experiment is analyzied, the tempo of relative system <t'> must be faster according to Lorentz's equation. Please read #17 under the thread " No time at the speed of light".

[Bobby]

Sorry everybody I've done it again:

 

Imagine two towers.

 

Now each tower has two each tower has a conveyor belt that moves a ball at a constant rate down the side of the tower and returns back up the side of the tower. The first tower is moving toward the second tower and the second tower is staionary. An observer on each tower calculates the time it takes for the their ball to travel down the tower and up again. The second observer calculates the elapsed time of the ball on the opposite tower. All four observers record equal times i.e. proving that the both the balls are moving at a constant speed. So the speed of light is a constant speed for all observers.

 

It appears there is two ways to view the results of this experiment.

 

1/ The first observer, in the first tower, and the second observer, in the second tower, view the same object to be moving at the same time, and speed over apparently different distances. So we could say that time is slowing down for the observer moving relevant to the ball.

 

However

 

2/ Would it not be equally satisfactory to state the ball is moving at a constant, over the same distance, all at the same time speed although the velocity by which you are moving away from the ball makes it appear that the ball is moving over a longer distance.

 

Now if time dilation actually occurs, and most people accept this as a fact, then the previous statement is untrue and it should not cause any offence. You should be able to understand the above reasoning and be able to rebuke it (No one is required to respond to this post in anyway). Now the second reasoning seems to be a reverse way of looking at relativity. That light for different observers (of different velocities) only appears to be moving over different distances. Makes sense in a mental sense does it not?

 

Damien

 

I mean come on the same light ray cannot be moving at two different distances. It is only moving in one direction.

 

 

 

It is incorrect to say that one observer can measure an event in another frame of reference relative to the second event. I.E. Betty can measure Betty - Ann and Betty - Carol. Betty cannot measure Ann - Carol.

[IDMclean]

You know what I think, I think that if you could achieve the Speed of Light then you wouldn't hold together, anything that doesn't already go that fast I think would come appart at the seams as it entered Absolute Freefall relative to the universe. It would then experience a scatter effect.

 

I imagine, to someone not going that fast, they would see this as the subject annihilating in a brilliant Anti-matter-style explosion as they're bit's and peices went flying in every direction as nothing would hold them together any longer.

 

If not that then I think the Space-Time Warpage would be sufficent to reach the schwarzschild radius and the subject would collapes into a blackhole. Either way it doesn't strike me as an efficent way to travel.

[Janus]

I think the problem that many people have with time dilation is that they try and treat it like a physical action that "acts" on something.

 

Bu this isn't how it works at all, Relativity is all about the the nature of Time and Space, how we measure them, and how these measurements are made between relatively moving reference frames.

 

With that in mind, let’s try this analogy as an aide to visualizing time dilation:

 

Start with two cars, A and B. They start at the same point and drive at the same speed in slightly different directions.

How would things appear from the perspective car A?

Something like this:

 

 

Where A and B are represented by the labeled spheres.

 

The horizontal lines represent the progress of the two cars with respect to A’s own progress. Note that B progresses in the direction that A is moving more slowly than A does. IOW, if you were riding in car A, car B would be behind you, and losing ground all the time.

 

Now let's switch things around and see how things look from B’s perspective:

 

 

 

Here, it is A that is perceived to lag behind B in the direction that B is moving. If you are sitting in car B, it would be car A that was behind and losing ground.

 

The point being that each car measures the other as moving more slowly as measured against its own progress.

 

Now when we consider how this applies to time dilation.

To do this we'll replace the cars with clocks and instead of plotting two spatial dimensions we plot spatial separation against time; the vertical direction as time and the horizontal as space.

 

If we go back and look at the first diagram, we see that clock A moves straight up. Meaning that it progresses through time but not through space. In this diagram, clock A is considered at rest. Clock B moves to the right as it moves upward, meaning its distance from A increases with time and thus it is moving at a constant velocity relative to A. Note that its progress through time lags behind that of A. IOW, from the perspective in which we consider A at rest, clock B ticks slower.

 

Looking at the second diagram, clock B is considered at rest, and it is A that is moving. Here, we see that from B’s perspective, it is A that progresses more slowly, and thus A that ticks slower.

 

This is time dilation. both A and B measure the other's progess through time( tick rate) as slower than their own This is a result of how each clock measures time and how it compares the other clock against its own tick rate.

 

Further posts will show how this analogy can be applied to the Twin paradox, length contraction, and the Relativity of Simultaneity.

[Janus]

Okay, there haven't been any new reponses to this thread, so I don't know if anyone is still reading this, but let's continue anyway.

 

As the next step, let's take what we learned in the last post apply it to the "Twin Paradox". In this case, B travels out a certain distance at a constant speed and then stops, turns around and returns at the same speed.

 

From A’s perspective and plotting time against distance like we did before, it looks like this

 

B goes out, turns around and then comes back. When it returns to A’s location it is still behind A in time, and thus less time has passed for it (we assume that B matches A’s velocity at the end. Thus if the animation were to continue, B would lag behind A by a constant amount as they move upward in the diagram.

 

Now consider the situation if we assume that B, on what A considers its outward leg, is actually at rest.

 

 

During the first phase, A lags behind B.

Then B starts to move to the left(accelerates towards A). In order to intersect A, it must move to the left faster than A. Thus, from the perspective from our frame of rest, it now progresses through time slower than A. So much so, that once it intersects A, it is now behind it, and more time has passed for A, just like at the end of the first diagram. So it doesn’t matter which frame you consider “at rest” you get the same result.

 

Now let's consider how things appear if we are actually traveling with B.

 

Then we get something like this:

 

 

It starts out like the last diagram, but once we reach the turnaround point of B, we switch to the new rest frame for B. As a result, A “jumps forward in time” from B’s perspective. After which, A again progresses through time slower than B. But, because of the forward jump in time, B never completely “catches up” with A. So once again, at the end, less time has passed for B than has for A.

[Kayra]

Thank you Janus, this has explained much.

 

I am a very visual person, and your method of explanation works VERY well for me.

 

On your last diagram, would the "jump" in time (from B's perspective) be due to the fact that B was forced to decelerate, then accelerate instantly to relativistic speed?

[Janus]

Thank you Janus, this has explained much.

 

I am a very visual person, and your method of explanation works VERY well for me.

 

On your last diagram, would the "jump" in time (from B's perspective) be due to the fact that B was forced to decelerate, then accelerate instantly to relativistic speed?

 

Yes, it is B's acceleration that causes A to move forward through time. The reason it seems to "jump" forward in the animation is that the acceleration occurs between animation frames.

 

I'll post an animation that slows down the process when I get a chance.

[TheFaithfulStone]

My two cents.

 

Janus's diagrams lead us to discover that FTL travel always results in time-travel paradoxes.

 

In this diagram X is a spatial axis and Y is a time axis. The yellow "cones" represent the spead of light. Notice the different "time" lines for the A&B frame and the C&D frame, while the yellow cones are the same.

 

 

Bascially, if A & B are at rest relative to each other, and C will pass B a few seconds in the the future. D has already passed A.

 

If A sends a superluminal (the line with a circle at the end) message to B, telling him that C is coming (never mind how he knows this for now...) and B gets this message just before C arrives and is able to stop C from delivering the microfilm, or his pizza, or whatever. Well C, who is traveling at relativistic speeds to A, sends a super luminal message back to D (the other line.) It arrives BEFORE A sends his message, and the C can affect his own past. D beats A, who can't send his message. The space-time continuum is ripped apart and everyone in the universe dies.

 

However, if the speed of light is the maximum speed limit, then no matter how close you move A & B and D & C, no one can send messages into their own past.

 

If you can find a way around this, my hat is off to you.

 

TFS

[IDMclean]

Well, lets assume all these possiblities happen, have happened and will happen. Let call it destiny. Now there's a chance that the above senario happens... However, the out come is uncertain.

 

We can turn this into a vector equation and from that figure what the most probable outcome would be, we can't predict which outcome it will be but we can predict that one of them has a significant chance of occuring.