Question about time and measurement

[Fiziqs]

A------------------------------B

Let's say that you have two identical atomic clocks with identical readings at point A. Now clock 1 is moved fast from A to B, and clock 2 is moved slowly from A to B. Then you compare the two clocks at B and you will find that clock 1 is behind on clock 2. In other words, the clock that moved slower will have recorded more units of time than the clock that moved fast.

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?

 

[questionator89]

Yes Fiziqs.
To make it simpler I try to make these two objects in the thought experiment traveling in circles so that they just meet up on there own orbit every few orbits or something.
If the fast object has to stop (and i am trying to figure out why when we "stop" we don't just age ininiftely by the pattern of time dilation) wait for the slow object I would assume that when they met they would actually have experienced the exact same amount of time.

Just like with the astronaut returning to Earth to see everyone age dramatically, the Earth doesn't speed up to catch the astronaut, and the astronaut doesn't slow down and wait for the earth. He, in most cases, will turn around and head back to earth.

Drakkith that is a good graph.

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.

And you keep saying to me there is no point in trying to understand what it would be like to travel at light speed, because we have no idea.

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.

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.

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

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?

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.

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.

 

[questionator89]

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?

an object at rest is already aging to infinity.
but we are barely moving so relative to us, it seems to be just ticking slightly faster.
we are already accumulating time at almost the maximum rate.But still, to add to this, could we not judge how fast an object has moved over its journey compared to us by how much more or less time it accumulated?

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?

 

[questionator89]

I think I answered my own question maybe.
We are already ALMOST experiencing the fastest rate of time we can accumulate.

 

[harrylin]

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?

If the clocks travel at the same speed then the two clocks will be equally retarded, so that they are in synch wiht each other. Instead, we compared a clock that was transported rapidly from A to B with a clock that was transported much more slowly from A to B. See §4 of http://fourmilab.ch/etexts/einstein/specrel/www/

 

[questionator89]

Harrylin, that is what Fiziqs was saying though.
We can't go from A to B and have this effect work. Ill explain what I mean.
If both clocks have to travel the same distance, this means they experienced the same time rate if they have to meet up.
The fast clock must go much farther and return to the other object for this to work. So the fast clock does a continuous loop and checks back in once in a while. Or the fast clock zooms away from the Earth turns around and zooms back. The fast clock could even zoom past the Earth and turn around and just do a back and forth guitar string pattern over the earth. something.

If we are sending two clocks from A to B, one going slow, one going fast, we would need Buddah to be the 3rd observer and count a certain amount of time, maybe after the fast clock is halfway through the journey or something, and check both the clocks at the same time and see which one has accumulated more or less time.

Its much better to comprehend if the fast clock makes the effort to get back to the slow clock for the comparison.

once the fast clock reaches point B, to compare clocks he would have to wait. and all of the extra anti aging he would have would be completely canceled out while driving miss Daisy meanders through the journey

 

[Fiziqs]

We can't go from A to B and have this effect work. Ill explain what I mean.
If both clocks have to travel the same distance, this means they experienced the same time rate if they have to meet up.

Actually questionator89 I think harrylin is correct, even if clock 1 has to stop and wait for clock 2 their clocks will not read the same. The reason that I think this is true is that the time dilation effect is not linear. In other words both clocks would end up reading the same time if going twice as fast simply meant experiencing half the passage of time. But time dilation isn't linear, going twice as fast will cut the passage of time by more than half.

Thus if clock 1 travels at just under the speed of light it will experience very little time at all, and if clock 2 is traveling at exactly half the speed of clock 1 it will nonetheless experience much more than twice the time. Going faster for a shorter period of time will have more of an effect than traveling slower for a longer period of time.

At least that's how it appears to me.

 

[questionator89]

Right. But isn't it all related to what distance you went through space time to give you this dilation?

At the end of the road with object one they measure the time. But then it takes the other object much longer to reach the end of the road. But once it reaches it they measure this time.
Under this scenario I can understand a discrepancy.

But if they measure both clocks at the same time, they would have to wait while the other object finishes the journey and the faster object sits not moving, which means the object which reached it faster is now experiencing the maximum accumulation of time that any object can experience because it is at rest. the slow moving clock is still moving towards it and experiencing slightly less time accumulation.
It is not linear it is an exponential increase, but it continues both ways.
To sit and wait for the other clock to arrive would take just as long as the entire journey that the slower clock perceived.

 

[questionator89]

Harrylin,
Could you explain one section in that link that you shared?
The part where the light particle is bouncing off a reflector and they are determining the difference in force between the light that hit the surface and left, and determining what force was enacted upon the surface (or "work done")?
I can't follow the math here. are they saying that the reflector feels the photons bounce off and moves?

I have heard of the solar sails that we are considering using for spacecraft , and ionic propulsion, but I do not understand how this works.

If a photon was massless how can it apply any force?
I thought that light bent with gravity only because gravity is warping the straight line that light would have normally travelled. What is the weight of an electron?

 

[harrylin]

Harrylin,
Could you explain one section in that link that you shared?
The part where the light particle is bouncing off a reflector and they are determining the difference in force between the light that hit the surface and left, and determining what force was enacted upon the surface (or "work done")?
I can't follow the math here. are they saying that the reflector feels the photons bounce off and moves?
[..]
If a photon was massless how can it apply any force?
I thought that light bent with gravity only because gravity is warping the straight line that light would have normally travelled. What is the weight of an electron?

That's a completely different topic; anyway in §8 he uses the concept of light waves and not photons - no light particles. Light pressure is already known from classical optics, compare https://en.wikipedia.org/wiki/Radiation_pressure.
Light energy is the square of its amplitude. By definition the work done on an object equals the energy that entered it minus the energy that was given back. if you want to discuss it further, please start it with a new thread.

 

[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

 

[questionator89]

And also if we read Drakkiths first post even, he sounds frustrated already.
Why do you even try Drakkith if it just aggravates you to talk to people so obviously less intelligent than you are

 

[questionator89]

Harrylin you were helpful

Drakkith you were helpful twice

Dalespam
all you do is argue about how I worded my posts. No helpful input

Im off PF good luck with your quest for knowledge

 

[Nugatory]

You must realize by now that I am not trying to determine absolute speed ...
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

The bolded text above is pretty much a definition of "absolute speed", so whether you realize it or not, you're still pursuing that notion. That may be why you feel like we're yelling at you...

You are always at rest relative to yourself, and everything that is not at rest relative to you is moving relative to you. And the same is true of everything else in the universe; every object in the universe is at rest relative to itself. Therefore, there is no way to determine whether something is "in motion", you can only determine that it is in motion relative to something else, and then its speed can be zero (no motion at all) or anything up to almost the speed of light (very fast motion indeed), depending on what something else you choose to compare with.

 

[TumblingDice]

So even if there is not absolute speed, at the speed of light time stops.

At the risk of not being perfect and hoping any "mistakes" are in my terminology.

Regarding the idea that time stops at the speed of light: If you examine the math, it's only valid with relative speed less than c. That's because if you plug 'c' as a reference speed into equations, you get an "undefined" result. That's because the function only "approaches" the axis where you might suggest that relative time stops. It cannot reach the axis where "time stops" because of standard rules of mathematics. We can toss around the concept of "infinity", but that's another example of something that requires proper perspective. Infinity is a concept, not a value. If it were a real value, the equations come out undefined, for example, the denominator of the result becomes zero, and dividing by zero is meaningless.

To be clear, anything with invariant mass can never travel at the speed of light. You can accelerate in your own reference frame until the cows come home and try your best to go faster. But as you do your thing to accelerate, the theory of relativity keeps "raising the bar". You can experience constant acceleration, but the math always confines you to only "approaching" c.

 

[Samshorn]

Believing in an absolute speed... must not be confounded with believing that measured speeds are absolute...

That's a mis-use of the word "measured". The confounding that you are referring to is not between measured and un-measured speeds, nor is it between observed and un-observed speeds. Relativity is not a subjectivist theory. It's propositions refer to perfectly well-defined objective attributes of the external world, regardless of whether they are measured/observed. The correct distinction is between defined and un-defined conceptions of speed. For example, the "one-way speed of light" can have any value we choose, because it is an undefined concept, whereas the "one-way speed of light in terms of a system of coordinates in which the Newtonian equations of mechanics hold good (to the first approximation)" is unambiguously equal to c. This is objectively true for any pulse of light, whether that particular pulse's speed is measured or not. So the distinction isn't between measured and unmeasured quantities, it's between defined and un-defined quantities. Or, to put it another way, the distinction is between knowing what we are talking about, and not knowing what we are talking about.

Needless to say, given the set of all possible inertial coordinate systems (defined as above), we are free to select one of them and declare it to be the "plamange" one. Or we could substitute the phonetic sound "true" in place of "plamange", without of course attaching any well-defined conceptual significance to the sound, but this kind of silliness takes us outside the bounds of physics (as Lorentz admitted to Einstein in his "universal spirit" confession), and of course it does nothing at all to explicate quantum phenomena (as Bell admitted when pressed on his "cheapest solution" comments). So calling it metaphysical is actually giving it too much credit. It's utterly pointless.

 

[ghwellsjr]

That's a mis-use of the word "measured". The confounding that you are referring to is not between measured and un-measured speeds, nor is it between observed and un-observed speeds. Relativity is not a subjectivist theory. It's propositions refer to perfectly well-defined objective attributes of the external world, regardless of whether they are measured/observed. The correct distinction is between defined and un-defined conceptions of speed. For example, the "one-way speed of light" can have any value we choose, because it is an undefined concept, whereas the "one-way speed of light in terms of a system of coordinates in which the Newtonian equations of mechanics hold good (to the first approximation)" is unambiguously equal to c. This is objectively true for any pulse of light, whether that particular pulse's speed is measured or not. So the distinction isn't between measured and unmeasured quantities, it's between defined and un-defined quantities. Or, to put it another way, the distinction is between knowing what we are talking about, and not knowing what we are talking about.

You lifted that quoted phrase from Einstein's 1905 paper (first article) where he proceeded to argue that the "one-way speed of light" requires an additional definition. Do you know something that Einstein didn't know?

 

[questionator89]

Right. I will lay a thought experiment out there to clearly define my question. I want to be clear that I am taking into consideration everything you say TumblingDice, but you should realize that, other than this one question, the concept as a whole is something I can grasp. Except infinity. But when I use this word I use it only for something that has lost all sentience or consciousness or meaning of time. And I have a feeling this perspective could comprehend infinity. and comprehend nothing at all ever.

My thought experiment:

We as a fourth observer are watching a spaceship move from left to right, viewed directly in front of us.

This spaceship launches two clocks out, at exactly the same speed.
The clock which it launched behind itself is seemingly at rest to our perspective as the fourth observer, because the exact rate at which the spaceship was moving was canceled out.

To the spaceship, both clocks zoomed away from it in exactly the same way, and the spaceship would see both clocks ticking at exactly the same rate. which is slower than its own rate of time.

The spaceship already knows how fast each clock left its surface. The spaceship knows what distance is between the ship and the two clocks always.

after 10 minuits each clock sends a signal back to the ship how much time was accumulated during the 10 mins to the ship. let's say that the clocks both accumulated 8 seconds

What you guys (all of you) are trying to convey to me is that to the ship, both clocks have experienced less time, because to the ship both clocks zoomed away from it.

Fine.

Lets think of it this way.
Now let's say this ship was already traveling at 99.9%c. The ship does not know it is traveling at this speed.

So to us as the fourth observer we know that the propellants in the clocks can't break this speed. We would expect from watching that the clock launched in front, would not be able to be launched in front.
And the clock launched behind would indeed be launched behind, and would be at a slower momentum relative to the ship. From our perspective.But what is conveyed to me is that, A) the ship has no idea that is traveling this fast, and cannot see anything around it including us as the fourth observer, except for the clocks.
B) Both these clocks will zoom away from the perspective of the ship at the same speed and seem to experience less time

So let's leave absolute speed completely out of this.
We know anything with invariant mass can never travel at the speed of light. Or our math tells us this?

So from the perspective of the spaceship both clocks leave and are zooming away.
But to the perspective of the fourth observer watching this all happen, the leading clock went faster than the speed of light, and the trailing clock is at rest and experiencing the same rate of time that we are?

How is it that, because the spaceship has nothing to reference from and does not know that he is breaking the this law, this is able to happen?

Wouldnt the spaceship notice that the clock ahead of him never sent another signal again?

To us as the fourth observer the trailing clock is at rest and experiencing the same time rate as us, which is much faster than the ship and the forward clock.

But to the ship this trailing clock is speeding away, and experiencing time dilation compared to the ships clock.
This means the the trailing clock sends a signal which would be identical to the leading ship, were it experiencing time.
Us as the fourth observer know that this leading clock is traveling faster than light (if it left the spaceship at all)

Would the ship only receive one signal? or Because the ship has no frame of reference , would the clock go faster than c?

Lets say the spaceship didnt use clocks. Let's say he used lasers.
Would his leading laser leave his spacecraft ? Would it appear to leave his spacecraft to the spaceship but not move to us as the fourth observer?

If light cannot break the speed of light, could you not at any velocity, throw a disco ball up and see which way the light goes slower?

So if you are already moving, you do not accelerate you do not slow down, you cannot know how fast(if at all) or in what direction you travel, you appear to be at rest.

And anything you launch away from yourself you assume is speeding up, because you believe you are at rest.

But isn't the speed of light completely independent from your speed/

When we are driving at 80mph and we throw a baseball at 80mph we know when this ball leaves our hand it is traveling 160mph

Does light follow this rule? If not wouldn't time dilation also not follow this rule?

 

[Samshorn]

You lifted that quoted phrase from Einstein's 1905 paper (first article) where he proceeded to argue that the "one-way speed of light" requires an additional definition. Do you know something that Einstein didn't know?

I said the "one-way speed of light" (with no further specification) is undefined, and hence requires an additional condition to be well defined and meaningful. You point out that Einstein said the same thing, and then you ask if I know something Einstein didn't. That's a bit of a non-sequitur, isn't it?

I think what you're missing (and what Einstein didn't emphasize as clearly as he might have in his initial paper, although in subsequent writings he did clarify) is that the extra condition represented by the definition of "inertial coordinate systems" in terms of Newton's laws (to the first approximation) amounts to stipulating the isotropy of mechanical inertia, and this is equivalent to the extra condition represented by stipulating isotropy of light speed. (This equivalence is unavoidable if you accept the inertia of energy.) Indeed this is what justifies the claim that the latter condition yields the inertial coordinate systems, just as does the former condition. That's why Einstein wrote that "With the given physical interpretation of coordinates and time, this [stipulation of isotropic light speed in terms of inertial coordinates] is by no means a merely conventional step, but... can be experimentally confirmed or disproved". You can read about this in any good book on relativity.

Again, the "one-way speed of light" is an undefined and arbitrary conception, but the "one-way speed of light in terms of coordinate system in which the equations of Newtonian mechanics hold good to the first approximation" is unambiguously equal to c, and this is an empirical fact that can be (and has been) confirmed experimentally. This is fundamental to a genuine understanding of special relativity.

 

[harrylin]

[..] Regarding the idea that time stops at the speed of light: If you examine the math, it's only valid with relative speed less than c. That's because if you plug 'c' as a reference speed into equations, you get an "undefined" result. [..]

Plugging in c doesn't work and of course it's impossible to reach that speed, but taking the limit gives you zero clock frequency. Einstein phrased the equivalent length contraction as follows:
the greater the value of v, the greater the shortening. For v=c all moving objects—viewed from the “stationary” system—shrivel up into plane figures." - the greater the value of v, the greater the shortening. For v=c all moving objects—viewed from the “stationary” system—shrivel up into plane figures.
- §4 of http://www.fourmilab.ch/etexts/einstein/specrel/www/

 

[harrylin]

That's a mis-use of the word "measured". The confounding that you are referring to is not between measured and un-measured speeds, nor is it between observed and un-observed speeds. Relativity is not a subjectivist theory. It's propositions refer to perfectly well-defined objective attributes of the external world, regardless of whether they are measured/observed. The correct distinction is between defined and un-defined conceptions of speed. [..].

I thought to make clear in that post, among other things, that SR is about making predictions of observations and not about metaphysics. But indeed I did not phrase one sentence well enough. Rephrasing: Maxwell thought that absolute speed can be measured.