Clocks and rulers

[swansont]

As an analogy, would you say each frame represents a lens with different perspective views but all give representations that are equally valid?

That works, but I was focusing more on a different aspect. I think use of the word "change" indicates a fundamentally flawed understanding. It's tied in with the "reality" aspect, as if there's a preferred frame that's truth.

 

If two people look at something, as with examples we've seen in recent discussion (e.g. the can), and we got different descriptions from each, one would not assert that the can changed shape.

[StringJunky]

That works, but I was focusing more on a different aspect. I think use of the word "change" indicates a fundamentally flawed understanding. It's tied in with the "reality" aspect, as if there's a preferred frame that's truth.

 

If two people look at something, as with examples we've seen in recent discussion (e.g. the can), and we got different descriptions from each, one would not assert that the can changed shape.

My understanding is that the observed (noun) doesn't change but the measurements do. One of the difficulties people might have getting to grips with it is imagining all these frames have their own discrete volume of space which is uniquely affected and then possibly try to align all the frames as 3D volumes butted together and it doesn't work or fit smoothly in the real sense. I just view the change in the signal for each observer and don't think about the space but am aware that each has its own geometry; you can't see it anyway in practice. I don't pretend to have it clearly in my mind but, at the end of the day, it's just the measurements that matter and the model they describe isn't it? The problem people are having is an ontological one, it seems.

[MigL]

I guess we all struggle trying to put relativity in everyday terms and words.

Its really meant to be treated mathematically.

 

But how about this then...

Reality is frame dependent.

A nerf ball could be nearly stationary to observer A' frame, and when it hits him he won't even feel it.

That same nerf ball could be moving at thousands of miles per hour as measured in observer B's frame, and when it strikes him it'll be like a ton of bricks.

Same nerf ball, but the way it interacts with each observer's frame is different, but equally valid.

 

Whatever you measure in your frame IS the reality ( distances, times, colors, masses, etc. ) in your frame.

Whatever is measured in another frame is the reality in THAT particular frame.

( kind of makes 'reality' subjective, doesn't it )

Edited August 9, 2016 by MigL

[J.C.MacSwell]

I guess we all struggle trying to put relativity in everyday terms and words.

Its really meant to be treated mathematically.

 

But how about this then...

Reality is frame dependent.

A nerf ball could be nearly stationary to observer A' frame, and when it hits him he won't even feel it.

That same nerf ball could be moving at thousands of miles per hour as measured in observer B's frame, and when it strikes him it'll be like a ton of bricks.

Same nerf ball, but the way it interacts with each observer's frame is different, but equally valid.

 

Whatever you measure in your frame IS the reality ( distances, times, colors, masses, etc. ) in your frame.

Whatever is measured in another frame is the reality in THAT particular frame.

( kind of makes 'reality' subjective, doesn't it )

I prefer to think of it as one reality, which can be considered from any choice of frame of reference, but I think this is where this leads...

 

You have one rest frame (setting aside the fact that you can be described as at rest in multiple non inertial frames)

That is your frame

That is the frame you are in

It is the only frame you are in

Anything moving wrt that frame is not in that frame

Nothing can move in a frame

Nothing happens in a frame

 

I think this is a little unfortunate if that is the implied context of being in a frame

Edited August 9, 2016 by J.C.MacSwell

[robinpike]

 

 

The ruler can only be in its own frame. It never moves to a different frame. Observers in other frames measure it as having a different length.

 

That is a good explanation as it avoids leading to logical contradictions.

 

The OP question asked why the time on the traveller's clock became out of sync with the stay at home clock, but the length of the ruler did not. Why does length and time behave differently?

 

The way this has been explained to me is that the rate of time on the travelling clock does NOT change - in the same way that the length of the ruler does not change. What changes is the distance of the journey of the travelling clock through 'space-time'.

 

Although maybe counter-intuitive - the travelling clock takes a SHORTER distance through space-time, and hence less time is shown on its clock when it returns than the non travelling clock. At no point did the rate of time on the travelling clock slow down.

[swansont]

That is a good explanation as it avoids leading to logical contradictions.

 

The OP question asked why the time on the traveller's clock became out of sync with the stay at home clock, but the length of the ruler did not. Why does length and time behave differently?

Which was answered in some detail.

[disarray]

 

The way this has been explained to me is that the rate of time on the travelling clock does NOT change - in the same way that the length of the ruler does not change. What changes is the distance of the journey of the travelling clock through 'space-time'.

 

 

I can somewhat imagine this if I think of the universe (i.e., spacetime) expanding in accordance with typical light cone illustrations. However, in keeping with the Equivalence principle, it doesn't seem that one can explain the time dilation related to being in a gravitational well in a similar way, i.e., by suggesting that one clock at one distance from the surface of, say, a planet, is taking a different path through spacetime than a clock at a greater distance.

 

[imatfaal]

 

I can somewhat imagine this if I think of the universe (i.e., spacetime) expanding in accordance with typical light cone illustrations. However, in keeping with the Equivalence principle, it doesn't seem that one can explain the time dilation related to being in a gravitational well in a similar way, i.e., by suggesting that one clock at one distance from the surface of, say, a planet, is taking a different path through spacetime than a clock at a greater distance.

 

 

I think you pretty much can although I am on very thin ice here - you need to use a metric which describes a non-inertial uniformly accelerating frame in otherwise flat space; this is the Rindler Metric. A test particle which is at rest in this coordinate system is undergoing constant acceleration. The same time dilation will fall out as the calculation you will have seen for gravitational potential. This sort of time dilation is very much based on the coordinate system that you are doing your calculation on and I am not sure if you can replicate these results if you set your frame as inertial and try to work from there

[StringJunky]

I prefer to think of it as one reality, which can be considered from any choice of frame of reference, ....

How about: reality is the sum of all possible frames?

[michel123456]

I prefer to think of it as one reality, which can be considered from any choice of frame of reference, but I think this is where this leads...

 

You have one rest frame (setting aside the fact that you can be described as at rest in multiple non inertial frames)

That is your frame

That is the frame you are in

It is the only frame you are in

Anything moving wrt that frame is not in that frame

Yes.

Because there is something that you observe.

All the observers from all the frames converge, focus to a point where there is "something". And this "something", the starting point, the physical object of observation does not physically change. The ruler never "physically" contracts.

However, the ruler may appear as contracted by some observer B. In this case, the situation should be symmetric and the guy who has the ruler at hand should observe observer B contracted.

Edited August 9, 2016 by michel123456

[MigL]

It doesn't contract in its own frame, you're right.

But it may contract in the frame you measure it from.

And it will affect you, in your frame, as contracted.

A frame doesn't have to be a light year away. It could be right in front of your nose, but with a relativistic velocity. It is still a different frame, and you will measure contraction of the ruler. Furthermore upon a collision, the ruler will act as if it is shorter. It affects your frame as you measure it, not as in its own frame.

 

So, if it quacks like a duck ( your measurement ), why do you keep insisting its a rabbit ( in its own frame ) ????

[disarray]

It doesn't contract in its own frame, you're right.

But it may contract in the frame you measure it from.

And it will affect you, in your frame, as contracted.

A frame doesn't have to be a light year away. It could be right in front of your nose, but with a relativistic velocity. It is still a different frame, and you will measure contraction of the ruler. Furthermore upon a collision, the ruler will act as if it is shorter. It affects your frame as you measure it, not as in its own frame.

 

So, if it quacks like a duck ( your measurement ), why do you keep insisting its a rabbit ( in its own frame ) ????

 

Forgive me if I am stating the obvious, but doesn't that last comment just emphasize the notion that the "size" of the ruler in its own frame (aka, inertial or rest frame?) is no more 'real' than it is from other (non-inertial) frames. That is, Relativity states that a rabbit is just as real as any number of ducks. In other words, we might state that there is no standard as to how long the ruler is, or what its mass is (for that matter), and perhaps even what its "true" velocity is.

 

 

I think you pretty much can although I am on very thin ice here - you need to use a metric which describes a non-inertial uniformly accelerating frame in otherwise flat space; this is the Rindler Metric. A test particle which is at rest in this coordinate system is undergoing constant acceleration. The same time dilation will fall out as the calculation you will have seen for gravitational potential. This sort of time dilation is very much based on the coordinate system that you are doing your calculation on and I am not sure if you can replicate these results if you set your frame as inertial and try to work from there

 

Well this is way above my head, but it seemed to me that these comments from Wiki might be relevant:

"But the world lines of our Rindler observers are the analogs of a family of concentric circles in the Euclidean plane, so we are simply dealing with the Lorentzian analog of a fact familiar to speed skaters: in a family of concentric circles, inner circles must bend faster (per unit arc length) than the outer ones.....In fact, in the close neighborhood of a black hole, the geometry close to the event horizon can be described in Rindler coordinates. Hawking radiation in the case of an accelerating frame is referred to as Unruh radiation. The connection is the equivalence of acceleration with gravitation."

In any case, is it fair to say that one should think in terms of a clock that is 'lower' in the gravitational well as being in a different spacetime frame from one that is lower, so that that being in an "inner circle" means that the inner clock (closest to earth) is taking a different path through spacetime than a clock at a greater distance.....much like skaters of different distances from the hub in the center of a skating rink are in different frames as they travel around it (as if centripetal or centrifugal force is relevant, e.g., escape velocity, perhaps) ?

 

Note: If this is an inane question and I have lost the plot owing to lack of mathematical knowledge, please ignore, and I will move on to a different issue.

 

I guess what I am getting at is to ask if it is more accurate to say that equivalence (i.e., in example of twin paradox and gravitational well and black holes) is the result of variations in energy/momentum, or whether it is more accurate to say that equivalence is the result of variations in space time.

 

 

How about: reality is the sum of all possible frames?

 

But wouldn't this sum be infinite?....so that we could never say what such a sum might actually be? Can the universe be described in terms of a finite number of Planck units (each with their own frame of reference or perspective perhaps?) in some way as if spacetime is a pixelated "fabric," and, if so, wouldn't the continual expansion of the universe at (approx.) speed of light also be a confounding factor so that even if we could find such a sum that it would be continually changing at the speed of light?

Edited August 10, 2016 by disarray

[MigL]

Only if you take my last sentence the wrong way, Disarray.

If it measures like a 'duck', it is a duck !

If the ruler measures shorter it IS shorter.

Your reality is only in your frame.

Never mind what other different lengths of rulers are measured in an infinity of other frames.

None are favoured, and so all are real IN THEIR OWN FRAMES.

[StringJunky]

Only if you take my last sentence the wrong way, Disarray.

If it measures like a 'duck', it is a duck !

If the ruler measures shorter it IS shorter.

Your reality is only in your frame.

Never mind what other different lengths of rulers are measured in an infinity of other frames.

None are favoured, and so all are real IN THEIR OWN FRAMES.

Indeed. The number of frames is irrelevant to the thought I posted.

[Endy0816]

I like going by the ratios, we'll all agree on those. Makes the math easier too.

[disarray]

Only if you take my last sentence the wrong way, Disarray.

If it measures like a 'duck', it is a duck !

If the ruler measures shorter it IS shorter.

Your reality is only in your frame.

Never mind what other different lengths of rulers are measured in an infinity of other frames.

None are favoured, and so all are real IN THEIR OWN FRAMES.

 

That's what I meant....There is no rabbit (real measurement of the ruler), just what one might call functional appearances (ducks) or 'realities' if you like, that are real in ones own frame (and never mind about other frames). I see you mention that there are an infinity of other frames, thereby agreeing I presume with my comment that there is no real (or more standard or preferred or definitive frame) even if one says that such a hypothetical real frame is the sum of the infinity of other frames (which, as I said, would be impossible to calculate anyway).

 

As an aside, I find it interesting that cubism developed at a similar moment in history as Relativity:

 

"The genius of Cubism is that it allows the viewer to escape from this “system of reference” of our three-dimensional spatial and one dimensional time dependent world. In Cubist artwork, objects are analyzed, broken up and reassembled in an abstracted form—instead of depicting objects from one viewpoint, the artist depicts the subject from a multitude of viewpoints to represent the subject in a greater context."

http://kkartlab.in/group/some-science/forum/topics/cubism-and-those-four-dimensions-of-einstein-s-theory-of

 

 

The ruler can only be in its own frame. It never moves to a different frame. Observers in other frames measure it as having a different length.

 

So the ruler comes back to earth and it will be the same length as a similar (say, 1 foot) ruler that had stayed on earth (that is, their ends will line up when you put them side by side). Presumably one might say the same things about its mass....it may be heavier while traveling (in comparison with the earthly inertial, frame), but have the same weight as a similar ruler that stayed on earth.

 

A wooden ruler will decompose with time; that is, it can age, though it would take several centuries (or even millennia) I suppose for it to turn to what amounts to dust.

 

But the point is, would a ruler that had traveled through space at near SoL for, say, a century, be less decomposed (younger) than a ruler made at the same time from the same materials on earth?

 

If the answer is yes, then it seems inconsistent that the length and mass would be the same on returning, but its molecular integrity (age) would be different.

Edited August 10, 2016 by disarray

[swansont]

So the ruler comes back to earth and it will be the same length as a similar (say, 1 foot) ruler that had stayed on earth (that is, their ends will line up when you put them side by side). Presumably one might say the same things about its mass....it may be heavier while traveling (in comparison with the earthly inertial, frame), but have the same weight as a similar ruler that stayed on earth.

 

A wooden ruler will decompose with time; that is, it can age, though it would take several centuries (or even millennia) I suppose for it to turn to what amounts to dust.

 

But the point is, would a ruler that had traveled through space at near SoL for, say, a century, be less decomposed (younger) than a ruler made at the same time from the same materials on earth?

 

If the answer is yes, then it seems inconsistent that the length and mass would be the same on returning, but its molecular integrity (age) would be different.

This "inconsistency" has already been covered. The analogous property to length is clock rate (frequency). The analogous measurement to elapsed time would be an odometer.

[J.C.MacSwell]

 

 

 

If the answer is yes, then it seems inconsistent that the length and mass would be the same on returning, but its molecular integrity (age) would be different.

 

If the aging and decomposing affected it's mass or length it would not be the same, but that would be for totally different reasons.

[disarray]

This "inconsistency" has already been covered. The analogous property to length is clock rate (frequency). The analogous measurement to elapsed time would be an odometer.

Yes, thank you, I recall the discussion. It would seem then that the length of a returning spaceship (or ruler) would be back to what is generally called 'normal' length and weight, but that the actual decomposition of the spaceship, ruler, and travelers is irreversible, though less 'severe' than their earthbound counterparts, and thus we could say that they had undergone a definite physical transformation. I understand that, from the earthbound frame of reference, the reality for us is that the ruler has shortened (though I don't know how we would get information about the length of the ruler while it is hypothetically traveling near SoL).

 

Nevertheless, the ruler returns intact and has a length comparable to other rulers on earth. Whatever change in length we might think or perceive it to have, however functional that perception might be from different frames such as that of earthlings, the change was only temporary (for the duration of the trip). Had the ruler physically changed length, however, when coming and going, then, just as it had decomposed in an irreversible manner, one would think that the ruler would be a bit worse for the wear of being stretched. (I think it was agreed earlier that the ruler does not physically change, particularly in its own frame).

 

Can I then conclude that, although different estimations of the mass and length of the ruler are, for all practical purposes or even in some ontological sense, just as "real," from all frames of reference, all such variations are more like (functional/useful) appearances, rather than physical variants, since they do not, unlike the state of decomposition (age), retain any changes once returning to earth.

If the aging and decomposing affected it's mass or length it would not be the same, but that would be for totally different reasons.

Good information. I was going to ask about that, actually, and presumed that was the answer.

Edited August 11, 2016 by disarray

[michel123456]

It doesn't contract in its own frame, you're right.

But it may contract in the frame you measure it from.

And it will affect you, in your frame, as contracted.

A frame doesn't have to be a light year away. It could be right in front of your nose, but with a relativistic velocity. It is still a different frame, and you will measure contraction of the ruler. Furthermore upon a collision, the ruler will act as if it is shorter. It affects your frame as you measure it, not as in its own frame.

 

So, if it quacks like a duck ( your measurement ), why do you keep insisting its a rabbit ( in its own frame ) ????

But in the ruler's frame, you are quacking like a duck.

What i say is that the ruler cannot be a rabbit, a duck, a dog, a cat, etc. at the same time just because it is been observed by many.

 

Look: even without Relativity, it is known that distance & time are obstacles.

We don't know that enough about the Moon, we must go there. We don't know enough about Mars and Jupiter, we must go there. We don't even know enough about our mother Earth, we have to dig and go there inside.

If you get a new pencil as a present, you will open the box, take the pencil at hand, feel it in your hand, take a piece of paper and write a little, even you will open it to see the mechanism inside (I do that).

Don't tell me that an observer thousand kilometers away traveling at half the SOL knows better the pencil than you do. If he tells you that it is blue while you admire your red pencil, who is right?

You will tell me that as physics are concerned, they are both right: the pencil is blue and the pencil is red.

To me it is not right. The one who has the pencil at hand knows better, because 1 he is closer 2 he is "in real time" 3 he is in the same frame.

 

 

Can I then conclude that, although different estimations of the mass and length of the ruler are, for all practical purposes or even in some ontological sense, just as "real," from all frames of reference, all such variations are more like (functional/useful) appearances, rather than physical variants, since they do not, unlike the state of decomposition (age), retain any changes once returning to earth.

 

That is my point, yes.

 

Because if the ruler IS shorter, and you put this shorter dimension into your equations, then you will find it would appear even shorter-shorter.

In fact, what you put into your equations is the ruler real dimension (in its own frame) and then get the contracted result as observed by you, or by another.

 

It is all about observation.

Now, if this observation has a real effect upon you, that is not a mystery that comes fom Relativity, the entire physics world is like this. I mean, if I throw a stone at you, and you are observing the stone coming right to your face, you may expect to hurt. Some other observer outside of the stone's path will not hurt. Another observer thousand of kilometers away will not hurt. You and only you will hurt, because it is your reality, not anyone else's reality. And the stone's velocity will be the velocity as measured by you. And the physical effects will be those corrwesponding to this velocity, not the velocity as observed by anyone else.

If you observe a mirror sideways at an angle, you will see the reflection of something (say, a red light). Some other observer next to you will see in the same mirror the reflection of something different at the same time, (say a blue light). So your face will become slightly red (because of the red light rays), and the observer-next-to-you's face will become blueish. If there is a mystery in this it is not caused by Relativity.

Edited August 11, 2016 by michel123456

[disarray]

Because if the ruler IS shorter, and you put this shorter dimension into your equations, then you will find it would appear even shorter-shorter.

In fact, what you put into your equations is the ruler real dimension (in its own frame) and then get the contracted result as observed by you, or by another.

 

Shorter-shorter: That seems like a very good point.

 

Certainly in the explanations I have read, there seems to be little effort to distinguish between functional appearances and actual physical events. I can understand the notion that all appearances are equal, since they are just appearances from a POV, however functional they might be:

 

If you throw a basketball at me, I will see it appear to grow as it nears my hands, and fapp (for all practical purposes) it works for my brain to see it coming to me as if it were growing. Even if I hold it extended in my hands and say this is its actual size (in an inertial rest frame), I could just as well move the basketball a few inches from my eyes, and again, it will seem larger, so that even in a rest frame, I am just dealing with appearances (that work). If we ask which image of the basketball is real (e.g., at what distance from our eyes), one can no doubt pragmatically reply, of course, that they are all equally real...no surprises here.

 

That length contraction is not as permanent, physical, or irreversible as ageing/decomposition/entropy only seems strangely contradictory if we claim that both are the result of the curvature of spacetime. But if we claim that the former is the result of differences in appearances, and the latter is the result of the curvature or stretching of spacetime, perhaps owing to changes in EM energy levels, there is not.

 

Given the principle of Equivalence, there should be length contraction (of the ruler) as well as mass increase at various distances in the gravitational well as well as what one might call permanent, 'decomposition dilation', though again, mass change (and length contraction?) is just temporary, depending upon how far up a mountain we night stand.

 

If there is length contraction of a ruler in a gravitational well as well as time dilation, we couldn't just say that it was a matter of appearances, as we might when talking about the traveling twin in a rocket, since we are actually holding rulers and clocks in our own rest frame as we change altitude as a single person (No twin needed!). Presumably, the slower ageing of the traveling twin will happen whether the earth observer is scanning the skies day and night or lying in a coma, but still wearing his atomic watch.

 

So one might ask whether the temporary effect of length contraction of a ruler is dependent upon a hypothetical "observer" in the same way that one might rightly claim that the apparent but useful change in the ("real apparent") size of the basketball (or the "real apparent" decibel level of it being dribbled) is dependent upon someone being in the gym.

Edited August 11, 2016 by disarray

[swansont]

Yes, thank you, I recall the discussion. It would seem then that the length of a returning spaceship (or ruler) would be back to what is generally called 'normal' length and weight, but that the actual decomposition of the spaceship, ruler, and travelers is irreversible, though less 'severe' than their earthbound counterparts, and thus we could say that they had undergone a definite physical transformation. I understand that, from the earthbound frame of reference, the reality for us is that the ruler has shortened (though I don't know how we would get information about the length of the ruler while it is hypothetically traveling near SoL).

The physical transformation from aging is a separate issue.

 

Nevertheless, the ruler returns intact and has a length comparable to other rulers on earth. Whatever change in length we might think or perceive it to have, however functional that perception might be from different frames such as that of earthlings, the change was only temporary (for the duration of the trip). Had the ruler physically changed length, however, when coming and going, then, just as it had decomposed in an irreversible manner, one would think that the ruler would be a bit worse for the wear of being stretched. (I think it was agreed earlier that the ruler does not physically change, particularly in its own frame).

 

Can I then conclude that, although different estimations of the mass and length of the ruler are, for all practical purposes or even in some ontological sense, just as "real," from all frames of reference, all such variations are more like (functional/useful) appearances, rather than physical variants, since they do not, unlike the state of decomposition (age), retain any changes once returning to earth.

 

If you reread the thread, you might see the continual message has been that there is no physical change, and that inquiries along that line indicate a misunderstanding of relativity. The items can't retain any physical change, because they never physically changed in the first place.

 

What changes is the reference frame. Lengths and frequencies depend on what frame you are in.

[disarray]

 

The physical transformation from aging is a separate issue.

But the physical transformation of aging (physical decomposition) permanently slows down so that not only does the spaceship clock/odometer have a different (slower?) reading, but the crew and spaceship have physically aged as well....Does not this suggest that time dilation is a physical phenomena, not just a matter of time itself slowing down?

If you reread the thread, you might see the continual message has been that there is no physical change, and that inquiries along that line indicate a misunderstanding of relativity. The items can't retain any physical change, because they never physically changed in the first place.

 

Yes, I am acknowledging that message....If I seem to again question it, it was because I wanted to clarify it. See my last post at 3:47 a.m. today.

 

[swansont]

But the physical transformation of aging (physical decomposition) permanently slows down so that not only does the spaceship clock/odometer have a different (slower?) reading, but the crew and spaceship have physically aged as well....Does not this suggest that time dilation is a physical phenomena, not just a matter of time itself slowing down?

Aging is a function of time passing, but is not directly caused by it — there's no "time interaction". All these things happen at whatever rate is present. If time is dilated by a factor of 2, then all of this aging happens half as fast. You seem to be suggesting some separate effect, which is not present.

[disarray]

So given equivalence, there is the question as to whether the ruler changes (or should I say, appears to change) length at various points in the gravitational well. If it doesn't then there doesn't seem to between the supposedly equivalent effects resulting from acceleration and gravity.

 

Also, in accordance with equivalence, I have read that people (or clocks and rulers) can be said to age at different rates depending upon the altitude at which they live, albeit in a minuscule amount (e.g., fraction of a second per lifetime).

 

I read that the spacetime warp of gravity affects the nature of the photon itself (e.g., light beam passing the sun): "Einstein argued...that as a photon travels through a gravitational field, it loses energy. This results in a lower frequency, or the number of times per second that the light wave oscillates, and a corresponding shift toward the red." http://www.pbs.org/wgbh/nova/physics/putting-relativity-to-the-test.html

 

I gather that greater spacetime "curvature" related to gravitational wells or spaceship travel leads to greater "stretching" of EM waves in general (e.g., radio, light) and therefore results in EM waves with a lower frequency, (relativistic) red shift, even in their own frame (a physical phenomenon), and thus, arguably, with the physical result that sea level and spaceship clocks/odometers (composed as they are of EM waves) run slower.

 

Whether space actually "stretches," thereby lowering wave frequency could, it would seem, be explained equally as well in terms of EM waves slowing down when originating from a fast-moving massive object (e.g., a train or spaceship), whether or not an actual observer is present....without mentioning spacetime at all. We say abstract things such as "time dilates" or "space expands" because doing so fits equations we have based on time (i.e., v=d/t and the Lorentz transformation equations) so accurately. But again, it seems to me that if time itself were just slowing down, thereby physically reducing the ageing process, that there would be no physical change to light wave frequency in a spaceship's own frame (as it travels near c through space), just as there is no physical change to the length of the ruler on board the spaceship in its own frame.

Edited August 11, 2016 by disarray