Unraveling the Time Dilation Argument: Does Speed Affect the Passage of Time?

[apinkpwny]

Me and a few friend are currently having a large argument whether time is actually changing when a shuttle is moving near the speed of light.

so the scenario is a shuttle moves near the speed of light for 100 years. with a clock set to 0:00:00 and a person on Earth also has a clock at 0:00:00.

after 100years the shuttle stops at the stationary person, would their clocks read the same time or will the person on the shuttle be younger and have a clock with a lesser time recorded.

 

[ghwellsjr]

You didn't explain how they started out but if you meant that the shuttle left Earth when both clocks read zero, then a hundred years later when the shuttle stops at the stationary person, their clocks will not read the same time, the person on the shuttle will be younger and have a clock with a lesser time recorded.

 

[apinkpwny]

You didn't explain how they started out but if you meant that the shuttle left Earth when both clocks read zero, then a hundred years later when the shuttle stops at the stationary person, their clocks will not read the same time, the person on the shuttle will be younger and have a clock with a lesser time recorded.

this is exactly what i meant thank you!one of us feels that as soon as the person traveling at a high speed comes to rest the clock will snap back to the stationary person's time.

if you could please explain in a simple way why one of us is wrong i would be much appreciated.

 

[Jobey]

But time itself would not actually change? correct? It would just appear that it has changed.

 

[Symbiosis]

You didn't explain how they started out but if you meant that the shuttle left Earth when both clocks read zero, then a hundred years later when the shuttle stops at the stationary person, their clocks will not read the same time, the person on the shuttle will be younger and have a clock with a lesser time recorded.

Time relative to the person on the shuttle appears normal, just as time standing still on Earth appears normal. My question would be: is the OBSERVED time less and not the ACTUAL time?

How does the actual time change when it's relative to the observer (guy on the ground or shuttle, not third party)?

Basically, what I'm asking is doesn't time only appear to go slower from guy's perspective from Earth, but once the shuttle guy stops, it should catch up to him (Earth guy), because the information is no longer traveling at near the speed of light (a.k.a. delayed).

 

[Dale]

The relativistic effects of time dilation, length contraction, and relativity of simultaneity are not visual effects or optical illusions. They are what remain even after correctly accounting for the appearances.

 

[Jobey]

But can the measurement of say one second change if you are moving faster or slower? 1 second is always 1 second no matter what... yes?

 

[Ryan_m_b]

But can the measurement of say one second change if you are moving faster or slower? 1 second is always 1 second no matter what... yes?

If we both count 1 Mississippi, 2 Mississippi...and then you jetted off far away at near light speed and came back some time later I would have counted far more Mississippis than you even though we have both been counting at the same rate. If Whilst I was counting I used a telescope to observe you I would see you counting far slower even though for you nothing has changed.

 

[Jobey]

Yes, but one second for me is still one second and one second for you is still one second. I'm not trying to relate the two different scenarios.

 

[ghwellsjr]

this is exactly what i meant thank you!one of us feels that as soon as the person traveling at a high speed comes to rest the clock will snap back to the stationary person's time.

if you could please explain in a simple way why one of us is wrong i would be much appreciated.

But time itself would not actually change? correct? It would just appear that it has changed.

Time relative to the person on the shuttle appears normal, just as time standing still on Earth appears normal. My question would be: is the OBSERVED time less and not the ACTUAL time?

How does the actual time change when it's relative to the observer (guy on the ground or shuttle, not third party)?

Basically, what I'm asking is doesn't time only appear to go slower from guy's perspective from Earth, but once the shuttle guy stops, it should catch up to him (Earth guy), because the information is no longer traveling at near the speed of light (a.k.a. delayed).

Wow, I feel like I'm being ganged up on. Do you guys all know each other?

OK, apinkpwny also didn't explain how the shuttle was going to travel, he just said it traveled near the speed of light. So I cannot tell you about the OBSERVED time because that depends on whether the shuttle traveled 50 years away from the Earth and then turned around and traveled another 50 years back, or maybe the shuttle took a big circular path so that it was always "turning around" the whole trip, or maybe it was in orbit around the Earth for the whole time.

As far as the ACTUAL time goes, in order to address that issue, we have to settle on a theory that includes the definition of time. Einstein's Special Relativity is one such theory that does this and the one that this forum is dedicated to providing an environment for learning. So using SR, you need to settle on a Frame of Reference in which time has a defined meaning. You can pick any FoR but it always makes sense to pick one in which the computations will be easier and that would be one in which the Earth remains at rest. (We always ignore the rotation of the Earth and its orbit around the Sun when we do these kinds of thought experiments.)

So according to how SR defines time, it progresses for each observer at a rate determined by the speed of that observer in the FoR. The faster the observer is traveling, the slower his clock ticks. If an observer remains stationary, his clock ticks normally. So the Earth observer is stationary, time progresses normally for him, and the shuttle is traveling at a high speed so time progresses at a slower rate for him. It's just as simple as that. If you analyze the situation from any other FoR, you will get the same answer, as far as the final result, but the computations will be much more difficult, in fact, so difficult that you can't do it in your head, you will have to get out your calculator and follow a bunch of equations, etc, etc, etc.

 

[Dale]

But can the measurement of say one second change if you are moving faster or slower? 1 second is always 1 second no matter what... yes?

Suppose you have a sheet of paper and you measure its size along one edge and get 11", then suppose your friend measures it along the diagonal and gets 14". You can describe this one of two ways, you can say that tilting his ruler along the diagonal made his ruler shorter in the vertical direction, or you can say that his ruler is the same as it always was, but just that by tilting his ruler he was measuring something different.

A clock is a ruler that measures time. The kind of time that is measured by a clock is called "proper time", this is like the distance measured by the ruler, a tilted ruler being like a clock which is moving. When you take a system of clocks and synchronize them that is like the lines on the piece of paper, it is called "coordinate time". The time dilation formula is about the relationship between coordinate time and proper time.

 

[Vanadium 50]

But time itself would not actually change? correct? It would just appear that it has changed.

What is the difference? More specifically, what experiment could you make that would tell the difference.

 

[ghwellsjr]

But can the measurement of say one second change if you are moving faster or slower? 1 second is always 1 second no matter what... yes?

Yes, but one second for me is still one second and one second for you is still one second. I'm not trying to relate the two different scenarios.

All the clocks moving together will tick at the same rate and all the time related processes will progress at the same rate so you will have no way of knowing that time is doing anything differently for you. But when you have things moving with respect to each other at different speeds, you need to establish a definition of time in order to make sense out of what is really happening.

And we have just one scenario, not two. That scenario can include any number of observers, all traveling in different directions and different speeds.

 

[apinkpwny]

thank you all for posting i really appreciated all the help you provided me and my friends, i think this is a very hard topic to grasp and even though we know it happens ( in theory) it is still something some people just have to dispute to maintain a sound sense of the universe. thanks again!

 

[Jobey]

Yes we are all friends :) Just with different opinions. But back to what I was talking about. SO what you are saying is proper time cannot change, this is the time we use on Earth its a measurement of an event and it always remains the same? This can never change?

 

[Dale]

even though we know it happens ( in theory)

Not just in theory. The experimental evidence is overwhelming.
http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html

 

[ghwellsjr]

thank you all for posting i really appreciated all the help you provided me and my friends, i think this is a very hard topic to grasp and even though we know it happens ( in theory) it is still something some people just have to dispute to maintain a sound sense of the universe. thanks again!

The theory is there to make sense of what is really happening. A shuttle that takes a high speed trip away from the Earth for a hundred years will really return with its crew (and clocks) having aged less than the people that remained on Earth.

 

[Dale]

SO what you are saying is proper time cannot change, this is the time we use on Earth

Proper time is the time measured by a clock. Any clock anywhere. It has nothing to do with whether or not the clock is on Earth or not.

As far as the rest of your question, it is too vague for me to answer. What do you mean by "remains the same" and "never change"? I described how you could look at a ruler and say that it had become shorter or how you could look at the same ruler and say that it had stayed the same. You need to be specific about what you are asking about when you are asking about changes.

 

[Jobey]

The theory is there to make sense of what is really happening. A shuttle that takes a high speed trip away from the Earth for a hundred years will really return with its crew (and clocks) having aged less than the people that remained on Earth.

See this is where I start to get confused on how this can happen, because the same amount of time has passed (from a 3rd party standpoint) on earth, and in the shuttle.

 

[Jobey]

Proper time is the time measured by a clock. Any clock anywhere. It has nothing to do with whether or not the clock is on Earth or not.

As far as the rest of your question, it is too vague for me to answer. What do you mean by "remains the same" and "never change"? I described how you could look at a ruler and say that it had become shorter or how you could look at the same ruler and say that it had stayed the same. You need to be specific about what you are asking about when you are asking about changes.

Proper time (the time measured by a clock) cannot change is what I am asking.

 

[ghwellsjr]

Yes we are all friends :) Just with different opinions. But back to what I was talking about. SO what you are saying is proper time cannot change, this is the time we use on Earth its a measurement of an event and it always remains the same? This can never change?

All clocks always display proper time. But the clocks that remain stationary at different locations in the selected stationary Frame of Reference and have all been set to the same time to begin with will display what we call the coordinate time. If you move a clock, it no longer can be used for coordinate time. So in SR, we reserve the term "proper time" for those clocks that we can move around and "coordinate time" for those clocks that must remain fixed at the locations where they were originally set to the same time. We use the coordinate times on clocks at each location to specify when and where "events" occur. Then we can talk meaningfully talk about how observers (with clocks) can move around and we can easily calculate how fast their clocks tick and keep track of the progression of the proper times on those clocks.

 

[Dale]

Proper time (the time measured by a clock) cannot change is what I am asking.

Again, too vague. What do you mean by change? What is the clock measuring the proper time between? The time measured by a clock depends on what events it is measuring the time between as well as how it travels from one event to the other. What are you keeping fixed and what are you allowing to vary?

If you have two events A, and B, then a clock which measures the proper time between A and B by traveling inertialy will be different from the proper time measured by another clock moving non-inertially between A and B.

 

[Jobey]

Again, too vague. What do you mean by change? What is the clock measuring the proper time between? The time measured by a clock depends on what events it is measuring the time between as well as how it travels from one event to the other. What are you keeping fixed and what are you allowing to vary?

If you have two events A, and B, then a clock which measures the proper time between A and B by traveling inertialy will be different from the proper time measured by another clock moving non-inertially between A and B.

Let me try to make my question more simple I guess, what I am asking is one second is always one second no matter what sort of scale we measure it on. 1:1

 

[ghwellsjr]

The theory is there to make sense of what is really happening. A shuttle that takes a high speed trip away from the Earth for a hundred years will really return with its crew (and clocks) having aged less than the people that remained on Earth.

See this is where I start to get confused on how this can happen, because the same amount of time has passed (from a 3rd party standpoint) on earth, and in the shuttle.

Join the club. Einstein's theory of Special Relativity doesn't offer an explanation of how this can happen but we know it does, not just from the theory, but from the experiments that caused scientists to develop the theory in the first place. It's just the way nature works. I'd like to offer you another choice but I'm afraid that as long as you stick around this world, you'll have to face the realities it offers you.

 

[Jobey]

I think I have come to terms with everything now, starting to make a little bit more sense. Thanks everyone for the info much appreciated!

 

[ghwellsjr]

I think I have come to terms with everything now, starting to make a little bit more sense. Thanks everyone for the info much appreciated!

Great, and what about your friends, does it make sense to them too?

 

[Jobey]

Yeah I think they have come to understand it too :) One is looking into it a bit more to learn some extra stuff but that's about it, thanks again!

 

[Symbiosis]

Heh, I don't think I'm smart enough to pretend to know one way or the other. I'm still fairly confused. The more I think about it, the more mind-boggling it gets.

The current debate in my mind (yes, I'm crazy) is if our measurement of time via atomic clocks can change, like observing an electron changes what it will do (double slit experiment came to mind). And if it does or doesn't change, what effect does that have on reality... like aging?

I was having a hard time understanding the link posted on the first page. The "twin paradox" section seems to say (unless I misunderstood that too) that it's "only a paradox in that it appears inconsistent, but it's not." This leads me to believe that the time recorded would be different, but not reality (your age would remain the same as the person sitting still on Earth).

The other experiment, the Transverse Doppler Effect confuses me completely. I guess I'm just ignorant and need some sort of visual assistance.

So ignoring the TDE (^), I'm just going off of the "Twin Paradox," which lead me to that question: is it possible the measurement of time gives us the illusion (I know that's not a proper term to use) of time dilation, e.g.: 10 minutes on Earth ~= 9.99... minutes traveling extreme fast. Almost all of my confusion stems from the idea that I have a hard time wrapping my head around the fact that traveling at all, effectively makes you age slower, albeit negligible.

I apologize if these questions/posts are confusing.

 

[Vanadium 50]

If you want to make the distinction between what is "really" happening and what is being measured by clocks, you need to come up with an experiment that can show the difference. Otherwise you are not talking about science.

 

[Symbiosis]

If you want to make the distinction between what is "really" happening and what is being measured by clocks, you need to come up with an experiment that can show the difference. Otherwise you are not talking about science.

Well I don't think it's realistic/feasible to actually test "aging" out (of anything, not necessarily living -- e.g. a metal ball suspended in water slowly rusting on Earth vs one in a fast shuttle over a long period of time... shuttle returns, compare results).

*Edit: That's actually really stupid example, but hopefully you get what I mean.

But people are saying that the guy on the fast trip would come back with a clock that's behind the stand-still one AND he would be younger than the stand-still Earth guy. The measurement of the clock I get, the age I don't, especially since "the fast-traveling guy would feel the same time passing by."

Is it just the measurement of time that changes or everything "time" encompasses? Cellular progression/decay slows down as well? That's the confusing part for me, but maybe I'm just looking at this from too simplistic of a viewpoint.

 

[ghwellsjr]

Heh, I don't think I'm smart enough to pretend to know one way or the other. I'm still fairly confused. The more I think about it, the more mind-boggling it gets.

The current debate in my mind (yes, I'm crazy) is if our measurement of time via atomic clocks can change, like observing an electron changes what it will do (double slit experiment came to mind). And if it does or doesn't change, what effect does that have on reality... like aging?

I was having a hard time understanding the link posted on the first page. The "twin paradox" section seems to say (unless I misunderstood that too) that it's "only a paradox in that it appears inconsistent, but it's not." This leads me to believe that the time recorded would be different, but not reality (your age would remain the same as the person sitting still on Earth).

The other experiment, the Transverse Doppler Effect confuses me completely. I guess I'm just ignorant and need some sort of visual assistance.

So ignoring the TDE (^), I'm just going off of the "Twin Paradox," which lead me to that question: is it possible the measurement of time gives us the illusion (I know that's not a proper term to use) of time dilation, e.g.: 10 minutes on Earth ~= 9.99... minutes traveling extreme fast. Almost all of my confusion stems from the idea that I have a hard time wrapping my head around the fact that traveling at all, effectively makes you age slower, albeit negligible.

I apologize if these questions/posts are confusing.

The reason why it is called the Twin Paradox is because if you consider a trip where the traveling twin goes for 50 years away from Earth at a constant speed then turns around and comes back at the same constant speed for another 50 years, then during each half of the trip you have a symmetrical situation that can be easily analyzed from the FoR in which either twin is at rest. Then the other twin is the one that is experiencing slow time. So it appears, to those who ignore what happens in between (the twin turning around and no longer being at rest in the same FoR), that the experience of the twins is symmetrical all the time and that they should be the same age when the traveler comes home.

But you can't change your Frame of Reference in the middle of the scenario without incurring problems. The correct way to analyze this if you want to use one of the two frames in which the traveler is at rest for half the trip is to continue that same FoR for the other half of the trip. Then you will get the same answer that he is the one that has aged less when they reunite.

Note that unless they start out together and end up together, there is no single answer to which one ages less, different FoR's will give different answers.

 

[ghwellsjr]

Well I don't think it's realistic/feasible to actually test "aging" out (of anything, not necessarily living -- e.g. a metal ball suspended in water slowly rusting on Earth vs one in a fast shuttle over a long period of time... shuttle returns, compare results).

*Edit: That's actually really stupid example, but hopefully you get what I mean.

But people are saying that the guy on the fast trip would come back with a clock that's behind the stand-still one AND he would be younger than the stand-still Earth guy. The measurement of the clock I get, the age I don't, especially since "the fast-traveling guy would feel the same time passing by."

Is it just the measurement of time that changes or everything "time" encompasses? Cellular progression/decay slows down as well? That's the confusing part for me, but maybe I'm just looking at this from too simplistic of a viewpoint.

If you are correct, don't you think the guy in the shuttle taking a 100 year trip would find it rather awkward that his clock was running really slowly? He could notice if it was running at one-tenth of its normal rate while he was aging normally. So everything runs slower, clocks, rust rates, aging, cellular progression/decay, everything. One of the tenets of relativity is that you cannot tell how fast you are traveling and if you were correct, then that would be a way to tell, wouldn't it?

 

[Symbiosis]

The reason why it is called the Twin Paradox is because if you consider a trip where the traveling twin goes for 50 years away from Earth at a constant speed then turns around and comes back at the same constant speed for another 50 years, then during each half of the trip you have a symmetrical situation that can be easily analyzed from the FoR in which either twin is at rest. Then the other twin is the one that is experiencing slow time. So it appears, to those who ignore what happens in between (the twin turning around and no longer being at rest in the same FoR), that the experience of the twins is symmetrical all the time and that they should be the same age when the traveler comes home.

But you can't change your Frame of Reference in the middle of the scenario without incurring problems. The correct way to analyze this if you want to use one of the two frames in which the traveler is at rest for half the trip is to continue that same FoR for the other half of the trip. Then you will get the same answer that he is the one that has aged less when they reunite.

Note that unless they start out together and end up together, there is no single answer to which one ages less, different FoR's will give different answers.

Oh my god. Thank you. That finally clicked and made sense.

The only other question would be, what if it wasn't a trip away and back, but rather around the Earth for 50 years? *Edit: Never mind, you answered with your next post.

If you are correct, don't you think the guy in the shuttle taking a 100 year trip would find it rather awkward that his clock was running really slowly? He could notice if it was running at one-tenth of its normal rate while he was aging normally. So everything runs slower, clocks, rust rates, aging, cellular progression/decay, everything. One of the tenets of relativity is that you cannot tell how fast you are traveling and if you were correct, then that would be a way to tell, wouldn't it?

Touche.

SR is really painful. I really appreciate you guys taking the time to answer our elementary questions by the way.

 

[ghwellsjr]

Well we love the quick learners and you guys are about the quickest I have ever seen.

 

[Dale]

Well I don't think it's realistic/feasible to actually test "aging" out (of anything, not necessarily living -- e.g. a metal ball suspended in water slowly rusting on Earth vs one in a fast shuttle over a long period of time... shuttle returns, compare results).

However, it is feasible to do this test using rapidly decaying subatomic particles, such as muons. If you go to the "experimental basis" link I provided earlier and look for muons you can basically think of them as very small metal balls that rust extremely quickly.

Is it just the measurement of time that changes or everything "time" encompasses? Cellular progression/decay slows down as well? That's the confusing part for me, but maybe I'm just looking at this from too simplistic of a viewpoint.

All clocks dilate the same amount, regardless of whether they are atomic clocks pulsing, heart beats thumping, metal spheres rusting, or particles decaying. It is everything time encompasses.