Question about time and measurement

[phyti]

I'm wondering if this is indeed correct. As you have described the thought experiment, clock 1 moves quickly from point A to point B, but it then it has to stop and wait for clock 2 to catch up, so that we can compare them. So for a period of time clock 1 is the faster moving clock, but then it stops and clock 2 becomes the faster moving clock. Do these two effects cancel each other out such that the two clocks will actually read the same time when clocks 1 and 2 reach point B? Or is the effect of increased time dilation exponentially greater as speed increases such that the faster moving clock will have actually experienced less time when both clocks ultimately reach point B?

You could have an observer at B record each reading when they arrive, or stop each clock when it arrives. The results will be the same.

 

[harrylin]

Harrylin, that is what Fiziqs was saying though.
We can't go from A to B and have this effect work. [..]

Sorry I can't follow you. As I said in my post #5, you seemed to correctly understand it in your post #1. But now you seem to say that what you said cannot be right, so that after all the explanations you now misunderstand it for a reason that I cannot follow. You seem to reason against yourself - and I give up!

 

[questionator89]

Yeah your right Phyti but that is irrelevant. Stopping the clock as it arrives, or writing down the exact time that it arrives is still recording the stopped time of the arrival. they are literally exactly the same.
the point is if you were to record both clocks at the same time (unless you did this before the first one reached its destination) there would be no time accumulation discrepancy.they would have aged the same.
If the other clock had to sit at rest and waiting for the other clock to arrive, then you recorded both clocks once the slow one arrived, they would read the same time.

Whereas if you as a 3rd observer were to record both clocks in motion before they arrived, the slow clock will have recorded many more units of time, and the fast clock would have recorded fewer.

Lets say your momentum was faster so your time is slower than both.
The journey starts , you wait 10 seconds then record how many seconds both of the other clocks experienced along the way. The fast clock will have experienced 13 seconds, but the slower clock would have experienced 35 seconds and is still farther behind than the faster clock.

 

[questionator89]

Sorry I can't follow you. As I said in my post #5, you seemed to correctly understand it in your post #1. But now you seem to say that what you said cannot be right, so that after all the explanations you now misunderstand it for a reason that I cannot follow. You seem to reason against yourself - and I give up!

I didnt understand something crucial before actually, that I do understand now. I already understood the entire concept except one thing. I falsely thought that if we were to stop something in orbit, if it were truly at rest, it would experience an infinite amount of aging.
what I forgot to piece together is that the only thing that could ever experience another object to age infinitely is something going the exact speed of light.
because we on Earth are moving, but not moving very fast, when we drop something into orbit it only experiences slightly more units of time than we do.
because we are already experiencing close the maximum rate of time passage due to how far away from the speed of light we are.

Harrylin youve been awesome I totally understand your frustration

 

[questionator89]

Anyways my original question was answered if anyone hasn't understood that.
Thanks everyone, secrest out.I am starting two new unrelated threads

-Can we determine what direction our star is traveling and at what velocity, based on time dilation
-Radiation Pressure and the weight of electromagnetic momentum

 

[Drakkith]

But I still do not understand why we can STOP the accumulation of time, but we can only speed up the accumulation of time by slightly over one second per Earth second.

What are you talking about? First, we can't stop the accumulation of time. Nothing you could do to an object will ever make it freeze in time.

Also, speed your spaceship up to 99.99999% c. The Earth is now experiencing severe time dilation and your clock will be accumulating MORE time than the Earth is.

Yet we have made the assumption that time stops?... right. So if it clearly shows time stopping at the speed of light you must agree.

Who made this assumption? Not me. Not science. I've already explained that we can't accelerate an observer to c so we can't predict what would happen if we could.

It is pretty easy to understand time stopping.
You will experience one second per second, but the next second will never come, and you will never take the time to have this thought, and your spaceship would never take the time to fire out rocket fuel or ions or whatever.
Best way to really grasp it is that you are dead for a moment because you are frozen in time.

This is wrong. This will NEVER happen. You do not experience time dilation in your own frame.

And I would much rather talk about why time cannot speed up according to you.And other physicists. (im assuming your a physicist?)

No, I'm just a guy who reads a lot and has spent 3 years on PF learning from people who are physicists.

If you were to reach 0 speed, then why would you only experience 1.000004 seconds per Earth second.
you are barely aging any faster at all, but we are assuming you are not moving?

Where are you getting these numbers from? They aren't correct. Just looking at SR, two observers at rest with respect to each other will measure the other's clock as ticking at exactly 1 second per second.

I should mention that if you were in a 0 rest frame, you would just experience one second per second, while anything at the speed of light would perceive you to age to infinity.
Maybe this is where I am getting confused.
Maybe I am correct, but we are already going so slow that our accumulation of time is almost at its maximum speed.
Things moving fast already see us aging at an incredible rate.

Again, wrong. Things moving near light speed perceive us as moving at light speed instead. To them WE are time dilated.

But this being said I know that our planet is traveling very fast around a star that is traveling very fast around a galaxy that is traveling very fast (maybe).
We could probably go a bit higher than 1.0000004 seconds per Earth second by going slower.

WITH RESPECT TO WHAT FRAME OF REFERENCE?
Seriously, you need to forget everything you think you know and focus on this one particular detail until it gets hammered in. Every time you post and say something is traveling fast I want you to add in "with respect to X frame", where X is whatever object or observer.

HHHMMMMM u know what.
at the speed of light you would perceive any slower speed to age to infinity.
Maybe this is where I have not understood this?

You are not understanding it, because you keep trying to figure out what happens to an observer at c. Stop it. It's only confusing you.

Einstein says when two objects are in motion relative to each other they have no idea if one they are still and the other object is moving toward them...

Our spaceships could flash a little signal to the other spaceship to start a clock,

and the one that was moving would be like " dude, i barely felt any time at all, you must have been waiting for soo long"

So can't we gauge how fast an object is moving, by how much time it accumulates, in comparison to another object?

Of course we can. But guess what? However fast that object is moving, to it YOU are moving at the same velocity instead.

 

[questionator89]

Wow drakkith you don't even get it, you are just nit picking bad grammar.
In every scenario there is a reference so I don't see where you get lost.
There is nothing we can do to freeze time? Except go the speed of light or apparently get sucked into a black hole.

Maybe you don't get it.

Besides the question I was asking was why can't we slow something down enough to age infinitely

Now I know the answer. The only thing that would perceive any object to age infinitely is something going the speed of light, where time freezes.
Ill clarify so you don't nit pick it to death, when i say "perceive" i don't mean someone going at the speed of light has the time to think about anything because time never begins and time never ends for an object traveling this speed.

In any case, when we drop something into orbit around the Earth it experiences only slightly more time accumulation compared to Earth because Earth is already going almost a resting rate

we are already experiencing close to the fastest rate of time accumulation we can, but still perceive 1 second per second.

so the question is ANSWERED.
And as far as in respect to what when you keep asking what reference or whatever.
When I say "going fast" i mean in respect to the total light speed, or in respect to normal Earth speed.

 

[Drakkith]

Wow drakkith you don't even get it, you are just nit picking bad grammar.
In every scenario there is a reference so I don't see where you get lost.

No, you don't appear to understand reference frames and why they are important to SR, otherwise you wouldn't be asking about the movement of the galaxy and trying to slow things down.

In any case, when we drop something into orbit around the Earth it experiences only slightly more time accumulation compared to Earth because Earth is already going almost a resting rate

What frame are you comparing Earth's motion against? The Sun? If so, then Earth and the satellite have identical amounts of time dilation over a period of time at least as long as the orbital period of the satellite around the Earth.

so the question is ANSWERED.
And as far as in respect to what when you keep asking what reference or whatever.
When I say "going fast" i mean in respect to the total light speed, or in respect to normal Earth speed.

Normal Earth speed in respect to what frame? The Sun? The galaxy? And no, you can't reference "total light speed" because light travels at c in all inertial frames of reference. We cannot assign an inertial frame of reference to light.

Edit: See this thread - https://www.physicsforums.com/showthread.php?t=714274

 

[questionator89]

Drakkith,
I am comparing Earth's motion against a clock which is at rest, not orbiting. Just like what I have been talking about for the past 60 posts and over 2 threads.
Each time I post I am pretty sure I mention this single scenario.

Drop a clock into space at rest, do a one year orbit around the sun, find how much more time accumulated for the resting clock compared to the clock on Earth which was moving.

The difference in time dilation should also give us a difference in velocity if the velocity is unknown, because we know how much time is dilated by how fast an object is moving.

So another scenario,
An astronaut leaves Earth at an incredible rate for a period of time then stops.
You say the Earth could view it as speeding away from the astronaut, but the astronaut will view it as he is speeding away from earth. They cannot tell who moved away from who.
But if the astronaut were to speed back to Earth and compare a difference between time dilation, he would have experienced much less time in comparison to earth. Is this wrong?

So if two objects wanted to tell which object was actually moving they could just compare how much time accumulated for each of them since the astronaut left the earth, or the Earth left the astronaut. no?

 

[questionator89]

im pretty sure that light doesn't always appear to be going "the speed of light"
I have said this before too, light is constant. You are saying this as well, but I think you think this means no matter what speed you are going a laser will always shoot out at the speed of light. But when in reality if you have any momentum at all, light will go slower
This means no matter what speed you are going, light will always go the same speed, separate from your speed.
this means if you are going fast light will appear to be going slower, and if you are going slow light will appear to be going faster.

If you were traveling at 50% of the total speed of light, for light to optically appear normal to you, it would have to be going 150% the speed of light which is impossible.

And in fact there is an inertial frame of reference for light. Because light has momentum it also displays properties of inertia and mass. This is how solar sails work.
When radiation hits an object the object feels this object as if it had some mass to it because of radiation pressure or something.

 

[Dale]

So if two objects wanted to tell which object was actually moving they could just compare how much time accumulated for each of them since the astronaut left the earth, or the Earth left the astronaut. no?

No, because they could both be moving. There is no such thing as actually moving. There is only moving wrt some frame.

 

[questionator89]

So then how does time dilation appear in reality at all if what you say is true.
This means that if I were to travel around at very close to the speed of light, and come back to earth, no discrepancy between minutes felt will be notable because the Earth also could have been the object speeding around at close to the speed of light?

So time dilation does not actually appear in reality?

The big difference being between the object which actually moved is that it accelerated, traveled fast for a while, then returned to the same velocity for clock comparison.
So firstly the Earth would not have felt any acceleration, and would not have experienced any time dilation by accelerating.

If time dilation does not effect reality then why is it being discussed at all

 

[Drakkith]

Drakkith,
I am comparing Earth's motion against a clock which is at rest, not orbiting. Just like what I have been talking about for the past 60 posts and over 2 threads.
Each time I post I am pretty sure I mention this single scenario.

Which would be fine if we were talking about the exact same resting frame the whole time, but we are not. You cannot just say the clock is at rest when we have different conditions for different observers. You must specify what frame of reference you are using or things will not make sense and the conversation will be very confusing. As this thread has shown.

Drop a clock into space at rest, do a one year orbit around the sun, find how much more time accumulated for the resting clock compared to the clock on Earth which was moving.

I assume the clock in space is kept at rest with respect to the Sun's frame?

So another scenario,
An astronaut leaves Earth at an incredible rate for a period of time then stops.
You say the Earth could view it as speeding away from the astronaut, but the astronaut will view it as he is speeding away from earth. They cannot tell who moved away from who.
But if the astronaut were to speed back to Earth and compare a difference between time dilation, he would have experienced much less time in comparison to earth. Is this wrong?

It's not wrong, it's just missing the key point in that the astronaut was accelerated while the Earth was not. Both still moved away from each other, but only the astronaut was accelerated. So while he's accelerating he can observe the Earth, do the calculations, and say, "Hey, I'M the one causing us to get further apart." Thus, when the two meet back up, the astronaut is the one who has experienced less time because he accelerated to a frame of reference that was no longer at rest compared to us and then returned back to the Earth's frame.

So if two objects wanted to tell which object was actually moving they could just compare how much time accumulated for each of them since the astronaut left the earth, or the Earth left the astronaut. no?

Kind of. Both objects are "actually moving" with respect to each other. But the difference lies in the fact that only one was accelerated. Plus, since this motion isn't steady, you cannot know exactly what the accelerated observer did just by comparing clocks when they return. You could only get an average velocity.

 

[Dale]

The word "move" means "change position over time". Mathematically, that is dx/dt, which is velocity. So "move" means velocity (specifically nonzero velocity). Motion (velocity) is relative, but acceleration is not. So while it is incorrect to say that one object "actually moved" it is not incorrect to say that one object "actually accelerated". The object that actually accelerated will accumulate less time.

 

[questionator89]

OOOOH .. Kay i get exactly where this translation was lost.
So if we were to all of the sudden become conscious and another object were all of the sudden to become conscious, they would have no idea which one was moving right?
But what I can't grasp is, one of these objects was accelerated to begin with and would be experiencing slower time, while the other one experienced faster time.
If when they became conscious they threw a signal to the other guy to start some ticker that accumulated ticks ( and both tickers were built so if they were at the same momentum they would experience the same rate of ticks) would the one that was actually moving have his ticker tick less? Right as they pass each other they flash the number of ticks each object experienced.

So one object would say your object is ticking fast and mine is ticking normally, while the other object thinks my ticker is ticking normally and yours is ticking slow?

Could we not, without knowing who was accelerated toward who, compare time dilation to find who accelerated?
or at least how much faster one is moving in the case that they are both not at rest.

Drakkith you are right we could only get an averaged velocity. But could we not use this to find out how fast our sun is moving (on average) around our galaxy?
And to answer your q from post 73 the clock is at rest, and the sun is at rest, and the Earth orbits the sun for one year and picks the clock up in what the Earth and the sun perceive to be the same location the clock was originally placed in.

 

[questionator89]

In that last post the part about the tickers, were going to assume that the tickers receive the signal and are automated to account for the time it took for the signal to reach the object and the starting distance.
the signal is RF so it travels at lightspeed and it won't matter how fast each one may or may not be moving

 

[Drakkith]

But what I can't grasp is, one of these objects was accelerated to begin with and would be experiencing slower time, while the other one experienced faster time.
If when they became conscious they threw a signal to the other guy to start some ticker that accumulated ticks ( and both tickers were built so if they were at the same momentum they would experience the same rate of ticks) would the one that was actually moving have his ticker tick less? Right as they pass each other they flash the number of ticks each object experienced.

You've already started on the wrong premise. BOTH objects are time dilated equally, regardless of who accelerated. This is because you have no frame other than the two which are in motion relative to one another to observe from. As such, you cannot claim that one is experiencing absolute faster time than the other. There is no "absolute" time.From wiki: http://en.wikipedia.org/wiki/Time_dilation

The green dots and red dots in the animation represent spaceships. The ships of the green fleet have no velocity relative to each other, so for the clocks onboard of the individual ships, the same amount of time elapses relative to each other, and they can set up a procedure to maintain a synchronized standard fleet time. The ships of the "red fleet" are moving with a velocity of 0.866 of the speed of light with respect to the green fleet.
The blue dots represent pulses of light. One cycle of light-pulses between two green ships takes two seconds of "green time", one second for each leg.

As seen from the perspective of the reds, the transit time of the light pulses they exchange among each other is one second of "red time" for each leg. As seen from the perspective of the greens, the red ships' cycle of exchanging light pulses travels a diagonal path that is two light-seconds long. (As seen from the green perspective the reds travel 1.73 (\sqrt{3}) light-seconds of distance for every two seconds of green time.)

The animation cycles between the green perspective and the red perspective, to emphasize the symmetry.

Could we not, without knowing who was accelerated toward who, compare time dilation to find who accelerated?

Nope. Both of you would measure equal time dilation.

Drakkith you are right we could only get an averaged velocity. But could we not use this to find out how fast our sun is moving (on average) around our galaxy?

You can, but you'd have to have a clock which is at rest with respect to the center of mass of the galaxy to measure compare with.

 

[Dale]

OOOOH .. Kay i get exactly where this translation was lost.
So if we were to all of the sudden become conscious and another object were all of the sudden to become conscious, they would have no idea which one was moving right?

Yes, although the anthropomorphization is unnecessary.

But what I can't grasp is, one of these objects was accelerated to begin with and would be experiencing slower time, while the other one experienced faster time.

Why should one of them have necessarily accelerated to begin with? Muons are created in the upper atmosphere all the time which live out their entire brief life at relativistic speed in the Earth's frame without ever significantly accelerating.

Indeed, for any object at there is a reference frame where it was at rest initially, but there are infinitely many other reference frames where it was moving initially. Thus, it is not generally true that "one of these objects was accelerated to begin with".

If when they became conscious they threw a signal to the other guy to start some ticker that accumulated ticks ( and both tickers were built so if they were at the same momentum they would experience the same rate of ticks) would the one that was actually moving have his ticker tick less?

Again, the phrase "actually moving" is simply incorrect.

So one object would say your object is ticking fast and mine is ticking normally, while the other object thinks my ticker is ticking normally and yours is ticking slow?

No. No clock ever ticks fast in an inertial frame. I thought that we had already covered this. Clocks at rest tick normally and moving clocks tick slowly. This is true in any inertial frame.

 

[questionator89]

Yes, although the anthropomorphization is unnecessary.

I agree.

Why should one of them have necessarily accelerated to begin with? Muons are created in the upper atmosphere all the time which live out their entire brief life at relativistic speed in the Earth's frame without ever significantly accelerating.

Well in the scenario the distance between them is shrinking. so either one is moving towards the other or they are both moving towards each other.

Indeed, for any object at there is a reference frame where it was at rest initially, but there are infinitely many other reference frames where it was moving initially. Thus, it is not generally true that "one of these objects was accelerated to begin with".

Ok so I can't tell, and you can tell, and I can tell that you can tell, that I do not understand something about this principle.
Is what I do not understand is that time dilation is just an optical illusion? Or can an astronaut actually travel at a fast velocity and experience less time than the planet he just left?

Again, the phrase "actually moving" is simply incorrect.

How would you word it then? We are using a scenario where there are two objects. One is moving and one is not. How do we figure out which one is actually moving.
If this is improper english I am sorry, but I do not know how to convey what I mean any better

No. No clock ever ticks fast in an inertial frame. I thought that we had already covered this. Clocks at rest tick normally and moving clocks tick slowly. This is true in any inertial frame.

 

[questionator89]

Thanks for your efforts you guys but I am unsubscribing from these threads.
I feel more insulted then helped anymore and have gotten no farther for the effort
I will read what I can on my own

 

[Drakkith]

Is what I do not understand is that time dilation is just an optical illusion? Or can an astronaut actually travel at a fast velocity and experience less time than the planet he just left?

It's no illusion, it actually happens. GPS satellites and particle colliders must deal with relativistic effects like time dilation all the time.

How would you word it then? We are using a scenario where there are two objects. One is moving and one is not.

No, you cannot say that one is moving and the other is not. Each one is moving according to the other's perspective. And they are both correct. Movement is relative!

 

[Drakkith]

Thanks for your efforts you guys but I am unsubscribing from these threads.
I feel more insulted then helped anymore and have gotten no farther for the effort
I will read what I can on my own

Well, thanks for wasting hours of our time. (or at least mine) I'm sorry you refused to listen.

 

[TumblingDice]

I've followed questionator89's threads and thread hops. Forum members - y'all have tried SO hard to help him get on track. My grandpa liked the saying, "you can lead a horse to water, but you can't make him drink."

My impression is that Q89 blew past excellent facts and references everyone worked to help with every time they didn't jive with the bad assumptions he started with. He used his own faulty reasoning to twist facts into an even worse understanding.

Q89 - I think you believe in absolute speed. I think you believe that somewhere in the universe there is a true reference frame that moves at absolute 0, and fastest reference frames move at c. That's incorrect and you have to let that misconception go before the rest makes sense. The word relative is "in relationship to something else" and relativity is about reference frames. If you can force yourself to accept there is no 'slowest' moving frame (no zero speed where time clicks fastest) and there is no absolute speed anywhere. Even c should not be thought in the sense of absolute in the classical sense. I think forum members even prefer the word invariant rather than constant, because we speak of the 'measurement' of c, and that never varies.

When I 'let go' of my classical handcuffs that caused similar frustrations for me, I found that the things I felt wouldn't make sense actually did. If you commit yourself to start with a foundation instead of trying to understand everything all at once, you'll have a much more enjoyable time learning what you seek.

 

[Drakkith]

Q89 - I think you believe in absolute speed.

Yes, I think we finally pinned down the ultimate source of his confusion just at the end of this thread and in another one right before that. I just wish we could have hammered this point in earlier, we might have avoided 4 pages of confusion.

 

[harrylin]

[..] Q89 - I think you believe in absolute speed. I think you believe that somewhere in the universe there is a true reference frame that moves at absolute 0, and fastest reference frames move at c. That's incorrect and you have to let that misconception go before the rest makes sense. [..]

TumblingDice that misconception is yours: Lorentz believed in absolute speed and everything made sense to him, as a matter of fact he also taught SR and GR and he explained it rather well. Different metaphysical interpretations work to make sense of the phenomena that SR describes, just as with QM.

 

[TumblingDice]

TumblingDice that misconception is yours: Lorentz believed in absolute speed and everything made sense to him, as a matter of fact he also taught SR and GR and he explained it rather well. Different metaphysical interpretations work to make sense of the phenomena that SR describes, just as with QM.

This is a good example of why I've read the forum daily for six months w/o posting. I found that quite often threads involve interpretations. I come here to learn, and keep an open mind when facts can be presented.

I have ideas I'd like to float that go deeply into the concepts and layers of time, but not for a while - not until i feel that I've learned enough to contribute further based on science. I think absolute speeds may play a key role in a larger picture. But, if I understand the math of reference frames, relative motion and time, there's no way to setup an experiment to measure. Just like trying to measure a one.way speed of light. (Hope i don't ruffle feathers with that. <grin>

So I'll wait to see if other members have anything to offer regarding your correcting what I wrote. Is a new thread in order?

 

[harrylin]

This is a good example of why I've read the forum daily for six months w/o posting. I found that quite often threads involve interpretations. I come here to learn, and keep an open mind when facts can be presented.

I have ideas I'd like to float that go deeply into the concepts and layers of time, but not for a while - not until i feel that I've learned enough to contribute further based on science. I think absolute speeds may play a key role in a larger picture. But, if I understand the math of reference frames, relative motion and time, there's no way to setup an experiment to measure. Just like trying to measure a one.way speed of light. (Hope i don't ruffle feathers with that. <grin>

So I'll wait to see if other members have anything to offer regarding your correcting what I wrote. Is a new thread in order?

Indeed there is no way to measure something like that, and heated debates about interpretations regularly get people banned from this forum (check the Rules!). In the QM forum discussions about interpretations are more tolerated, perhaps because in publications on QM such interpretation issues are still discussed but not anymore in publications on relativity. The topic came up in several threads before which you can check out:
www.physicsforums.com/showthread.php?t=595021
www.physicsforums.com/showthread.php?t=574624

PS: As you see in the Rules, this forum allows discussion of the historical development of SR and GR, as found in the literature; but floating personal ideas or theories is against the rules.

 

[Drakkith]

I'm not sure I see the issue Harry. How is believing in an absolute speed not a misconception? Where do interpretations come into this?

 

[harrylin]

I'm not sure I see the issue Harry. How is believing in an absolute speed not a misconception? Where do interpretations come into this?

Did you read through the past discussions to which I linked? Believing in an absolute speed (Lorentz; impossible to disprove metaphysics) must not be confounded with believing that measured speeds are absolute* (Maxwell; disproved by experimental confirmation of Lorentz and Einstein).

*[edit. rephrasing: believing that absolute speed can be measured]

 

[questionator89]

Yah I checked in,
So even if there is not absolute speed, at the speed of light time stops. Drakkith will disagree with this by saying that we can't reach the speed of light so there is no way to know.
If we are following a pattern where time rate is slowing down, eventually it must stop.;
just like my misconception about us on Earth not be resting. The Earth (bad example) cannot go slower than 0.
and time cannot go slower than 0 after and at 100%c(unless you believe you can go back in time).

Drakkith continually misread what I was posting. Every post was more of an argument than a lesson.

YOu must realize by now that I am not trying to determine absolute speed or absolute rest or time.

I am trying to figure out if there was a way to tell you were in motion, if you already were in motion and not accelerating or decelerating

A couple smart people once said "If you cannot explain something to a 5 year old and have him comprehend it then you do not understand it fully"

Im not passing blame and I really do appreciate all the responses.

As of right now, nobody can truly tell me what it is that I do not comprehend.
And Dice, its not absolute speed or rest. But I do believe we would lose the ability to be sentient at the speed of light, and our spaceship wouldn't take the TIME to propel itself and likely wouldn't take the TIME to slow down or speed up anymore to get you out of this state of frozen time. So I wouldn't do it

Great input tumbler, its really awesome that you followed my posts the whole time and jumped in once I left and criticized me without any input whatsoever