Definitions (continued from the cosmology forum)

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The discussion centers on the constancy of the speed of light and its implications in different inertial frames, emphasizing that while the speed of light is a fundamental axiom in special relativity (SR), it cannot be proven but rather serves as a basis for deriving other physical laws. Participants debate the interpretation of measurements taken by physicists A and B, who construct identical meter sticks while in relative motion, and how time dilation affects their observations. The conversation highlights that both physicists would agree on the length of their rulers when at rest, yet the time marked by their clocks would differ, leading to complex reasoning about the speed of light. Some argue that this discrepancy could suggest a variable speed of light, while others maintain that the constancy of light speed remains valid across inertial frames. Ultimately, the discussion underscores the intricate relationship between measurement, time, and the foundational principles of physics.
  • #61
Chrisc said:
Thanks atyy,
Unless I'm mistaken this is not the issue DaleSpam and others have with my claim.

No, I'm trying to figure out why you have a problem with what eg. DaleSpam is saying. I can't figure out why you feel the need to take, as DaleSpam says, x1/t or x/t1. I guess you somehow feel that the clock presents evidence that it has changed rate, while the ruler doesn't present evidence that it has changed length? However, the quantity on the clock that shows the change is an integral - the final rate of A and B's clock is the same, but the integrated time is not. So I am suggesting you look at the integral of the measured length so that the "ruler" also presents evidence that it was different (maybe, I haven't really thought this through).
 
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  • #62
DaleSpam said:
Chrisc, I have already answered that question several times and I am simply not masochistic enough to go down that road yet again with you.

I tried to communicate using English; I tried to communicate using math. I told you the same thing using both English and math, I clearly connected the two, and I pointed out your error both ways. You seem to have a very difficult time forming a cogent argument in either English or math. I am not the only one who has voiced this communication difficulty, so I don't think it is due to stolidness on my side.

The bottom line is that despite several pages of attempts you have simply failed to make your case that "they have little option but to conclude the speed of light differs between the labs when they are in motion". Every attempt to do so has involved taking an expression like x/t1 or x1/t and trying to pass it off as a velocity.

DaleSpam, I too am finding this an exercise in futility.
You are I think, quite aware of the meaning of my question.
Why you are avoiding it I don't know.

If you really do think that the evidence of clocks and rulers can change without
that change indicating a change in what clocks and rulers measure - Length and Time -
then this discussion certainly is futile.

I am grateful for your time and effort.
 
  • #63
atyy said:
No, I'm trying to figure out why you have a problem with what eg. DaleSpam is saying.
I do not have a problem with what DaleSpam has said in general.
He is employing the convention of SR to show me that c is constant in all frames.
I do not disagree with that, I never have.
It is DaleSpam who has a problem with what I've said.
atyy said:
I can't figure out why you feel the need to take, as DaleSpam says, x1/t or x/t1.
Taking x1/t or x/t1 is simply a cross reference of L/T of A and B.
atyy said:
I guess you somehow feel that the clock presents evidence that it has changed rate,
Yes, it is evidence that A's clocks have changed rate wrt B's.
atyy said:
while the ruler doesn't present evidence that it has changed length?
I am not concerned that the ruler does not present evidence of changing length.
The evidence of c by A during the experiment is indication that Length did change.
If it did not A would not have found c = 300,000km/s.
 
  • #64
Chrisc said:
Why you are avoiding it I don't know.
I didn't avoid it, I already answered it. The point is that you are the one making the unorthodox claim and so it is up to you to substantiate it, which you have failed to do.
 
  • #65
DaleSpam said:
I didn't avoid it, I already answered it. The point is that you are the one making the unorthodox claim and so it is up to you to substantiate it, which you have failed to do.

My claim is unorthodox?

You agree time dilates between frames in motion.
You agree speed requires a measure of time.
Yet you deny the time dilation will affect the measure of speed.
Why - because length contraction makes it impossible to detect.

Do you not see you are denying the existence of a deduced
state of physical dimension by inferring the validity of the deduction
precludes its own existence?
You claim Time dilation and Length contraction are physically real
effects of motion, yet deny any change of Time and Length because as
they change they make it impossible to detect that they have changed.

Are you familiar with the story of the Emperor's New Clothes?
 
  • #66
Chrisc:
the discrepancy in the total time marked by their clocks leads them to reason the speed of light differs between their labs when in motion, but is constant wrt any "measure" of length/time in either lab.
This is your original assertion.

You seem to be saying that there is an underlying objective reality in which there is something called 'the speed of light'. This thing may vary between frames - but we never measure this thing, whenever we try we always come up with the same number, because nature conspires to alter our instruments to hide this difference.

If this were so, then the 'underlying speed of light' has no effect of the laws of physics, cannot be empirically falsified or detected, and so is irrelevant. The thing just contradicts itself - why are you so convinced it has any meaning ? Your arguments are mathematically naive - you cannot 'prove' that it exists after admitting it can't be measured.

You may be interested to know that there's a theory of gravity called PV gravity that postulates that matter changes \epsilon_0 and \mu_0 and thus the locally measured speed of light. There's an excellent summary here
http://en.wikipedia.org/w/index.php?title=Polarizable_vacuum&oldid=56603531
 
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  • #67
Chrisc said:
My claim is unorthodox?
Yes.
Chrisc said:
Do you not see you are denying the existence of a deduced
state of physical dimension by inferring the validity of the deduction
precludes its own existence?
No, I don't see that, and you have failed to demonstrate it as indicated above.
Chrisc said:
Are you familiar with the story of the Emperor's New Clothes?
Yes, are you familiar with the story of the boy who cried wolf?
 
  • #68
Mentz114 said:
Chrisc:

This is your original assertion.

You seem to be saying that there is an underlying objective reality in which there is something called 'the speed of light'. This thing may vary between frames - but we never measure this thing, whenever we try we always come up with the same number, because nature conspires to alter our instruments to hide this difference.

No, I am not the one claiming immeasurable mechanics. I am the one claiming the time dilation of A's clocks is VERY REAL, VERY MEASURABLE evidence of a change in the dimensions of A while in motion.
DaleSpam is claiming the dilation of A's clocks is evidence that should be IGNORED or worse considered proof of his claim that the dimensions of A were NOT CHANGED while A was in motion wrt B.
Think about that for a second. A physically real, measurable CHANGE in a fundamental dimension of physics should be IGNORED, or considered evidence of NO CHANGE.
Now explain to me why I'm the conspiracy theorist, why my arguments are naive, why I should suffer the burden of proving to reasonable people that a physically measurable change in a fundamental dimension is evidence of a physically measurable change in a fundamental dimension?

Thanks for the link.
 
  • #69
DaleSpam said:
No, I don't see that, and you have failed to demonstrate it as indicated above.
One last appeal to your ...
10/20 = 1/2
If I gave you 10 dollars over twenty days or 1 dollar over 2 days, I would in each case give you the same thing, a ratio of money/days that is a constant $0.50/day.
I think you will agree the ratio of money/days remains constant and if all you could ever look at was the money/day you would argue (as your are now) that there is no difference in the money/day in either case.
I am simply arguing that since you can look at more than the money/day in that you can see that the time of A is different than the time of B, you must consider the magnitude of the ratio they both agree on is different between them. One gets a total of 10 dollars, the other a total of 1 dollar.



DaleSpam said:
Yes, are you familiar with the story of the boy who cried wolf?

I am, and I've enough confidence to leave it at that.
Again, I thank you for your time and hope someday you will see this beyond the math.
 
  • #70
Chrisc said:
One last appeal to your ...
10/20 = 1/2
If I gave you 10 dollars over twenty days or 1 dollar over 2 days, I would in each case give you the same thing, a ratio of money/days that is a constant $0.50/day.
I think you will agree the ratio of money/days remains constant and if all you could ever look at was the money/day you would argue (as your are now) that there is no difference in the money/day in either case.
I am simply arguing that since you can look at more than the money/day in that you can see that the time of A is different than the time of B, you must consider the magnitude of the ratio they both agree on is different between them. One gets a total of 10 dollars, the other a total of 1 dollar.
I actually like this example quite a bit. The amount of money a worker earns divided by the amount of time that they worked is called the worker's wage. The fact that A earned $10 and B earned $1 does not in any way contradict the fact that they were paid the same wage of $0.50/day (must be a "sweat shop").

Additionally, the amount of money earned by A divided by the time worked by B is not a wage and vice versa. So the fact that those numbers are not equal to $0.50/day also does not in any way contradict the fact that they were paid the same wage. There is, in fact, no logical way for them to conclude that they were paid different wages, despite the fact that they earned different amounts of money.

All of your assertions in this thread have been based on this type of mistake as I have pointed out long ago.

Chrisc said:
I thank you for your time and hope someday you will see this beyond the math.
That "see beyond the math" is an interesting phrase. Math is the language of logic, so what that phrase means is that you hope I will just discard logic and blindly accept your claims.
 
  • #71
Additionally, the amount of money earned by A divided by the time worked by B is not a wage and vice versa. So the fact that those numbers are not equal to $0.50/day also does not in any way contradict the fact that they were paid the same wage. There is, in fact, no logical way for them to conclude that they were paid different wages, despite the fact that they earned different amounts of money.

All of your assertions in this thread have been based on this type of mistake as I have pointed out long ago.
Good thinking, Dalespam.
 
  • #72
DaleSpam said:
All of your assertions in this thread have been based on this type of mistake as I have pointed out long ago.
No, all of your answers have been this same misconstrued take on what I've said.
But as you like this analogy...

Consider two workers meet in a bar and claim to have earned the same wage $0.50/day.
They put their pay cheques on the table and see they are exactly the same amount.
All is well until they notice that one of their watches shows that worker only worked half as many days.
As their pay cheques match, is there some answer you can offer other than the worker whose watch ran slow was paid $1.00/day relative to the other?

DaleSpam said:
That "see beyond the math" is an interesting phrase. Math is the language of logic, so what that phrase means is that you hope I will just discard logic and blindly accept your claims.
No, I said "see beyond" the math not exclusive of or regardless of or instead of...
you are not doing yourself any justice by twisting my words to suit your argument.
 
  • #73
Consider two workers meet in a bar and claim to have earned the same wage $0.50/day.
They put their pay cheques on the table and see they are exactly the same amount.
All is well until they notice that one of their watches shows that worker only worked half as many days.
As their pay cheques match, is there some answer you can offer other than the worker whose watch ran slow was paid $1.00/day relative to the other?
They can't have the same total and the same rate, if one worker worked less time than the other. It doesn't make sense. Someone in that scenario is mistaken.
 
  • #74
Mentz114 said:
They can't have the same total and the same rate, if one worker worked less time than the other. It doesn't make sense. Someone in that scenario is mistaken.

Let me rephrase what you've just said in context of what this thread has been discussing.
They can't have the same Length of ruler and the same speed of light if A's time ran slower than B's.

Are you suggesting the physicists in A were mistaken when they measured c to be 300,000km/s?
Perhaps you think that the numbers on the pay cheques "changed" from when they worked to when they met in the bar?

Or perhaps you are beginning to see my point... the rate is, was and always will be the same, the same ratio, the same rate of pay, the same rate of motion or the same speed. What changes is the dimensions by which these are measured. When Length contracts and Time dilates BETWEEN two frames in motion, then that which is defined by the quantities of these CHANGED measures, is itself changed BETWEEN these same frames.
 
  • #75
Chrisc said:
is there some answer you can offer other than the worker whose watch ran slow was paid $1.00/day relative to the other?
Sure, one is a full-time employee and the other is a part-time employee.
 
  • #76
Mentz114 said:
Good thinking, Dalespam.
Thanks! :smile:
 
  • #77
DaleSpam said:
Sure, one is a full-time employee and the other is a part-time employee.

Funny, useless, but funny.
 
  • #78
Chrisc said:
Funny, useless, but funny.
Hehe, thanks!

Of course there are some obvious limitations with your analogy: there is no "invariant wage", time worked and money earned don't Lorentz transform, and inflation isn't really analogous to length contraction.

But even so I was making the point that proper time is not the same as "time worked" which is in the definition of wage. Only working time is relevant, which is generally different from wristwatch or calendar time.

Similarly with your original point. Regardless of how you object, it remains clear that your assertions result from mixing frames or equivalently from using the wrong time in calculating a speed.
 
  • #79
DaleSpam said:
Regardless of how you object, it remains clear that your assertions result from mixing frames or equivalently from using the wrong time in calculating a speed.

It is clear from this statement that you still don't understand what I've said.
You are stuck on the notion that I've mixed frames with x/t1 and x1/t.
I've explained the inequality of this cross reference shows a change in
MAGNITUDE of dimensions measured NOT the inequality of the speed of light.

It is this change you are failing to see, or ignoring or for some reason denying.
Until you acknowledge a very real change of dimension between A and B you will
not understand what I've said.

Think of this distinction as the difference between dimensional and dimensionless physical constants.
You posted a very lucid account of this distinction a while ago.
Use your reasoning there to see and define the difference here.

The speed of light is a physical constant in all frames.

The magnitude of the dimensions that comprise this constant change...between frames.

A change in the numerical value of c would have no affect on the laws, it would be an imperceptible change.

A change in the ratio of dimensions that is c would have significant affect on the laws.

I'll leave the rest for you to reason through, but I would be very interested in your results.
 
  • #80
Chrisc said:
It is clear from this statement that you still don't understand what I've said.
You are stuck on the notion that I've mixed frames with x/t1 and x1/t.
Perhaps I don't understand your new argument if it has been modified from your previous derivation. Can you derive your new assertion without mixing frames with expressions like x/t1 and x1/t?
 
  • #81
Chrisc, I don't even understand the assertion, let alone the argument. I'm especially confused since you agree with DaleSpam, yet you seem to be saying something different. So if you can state what you mean in a simple way, I would be much less confused.
 
  • #82
DaleSpam said:
Perhaps I don't understand your new argument if it has been modified from your previous derivation. Can you derive your new assertion without mixing frames with expressions like x/t1 and x1/t?

I've not changed my argument, I am offering another perspective that I thought you'd be more familiar with.
 
  • #83
atyy said:
Chrisc, I don't even understand the assertion, let alone the argument. I'm especially confused since you agree with DaleSpam, yet you seem to be saying something different. So if you can state what you mean in a simple way, I would be much less confused.

From the beginning my assertion has stemmed from the fact that the constancy of the speed of light is empirical evidence.
As malawi-glenn said, "we can never prove the light speed to be constant."
Upon SR surviving falsification, the postulate is considered sound, but still not prove-able as it is a postulate or axiom of the theory.
SR holds the speed of light constant by formulating a change in the dimensions that comprise it.
In other-words, when the theory does away with absolute rest, it simultaneously does away with the notion of all absolute measures including those of the dimensions Length, Time and Mass.
This is interesting - the lack of absolute measure affords a universal constant of measure "c".
It should be clear from this that between frames in constant linear motion, there exists a very real, verifiable CHANGE in the dimensions that comprise the motion of light.
How can we verify a physical change in dimension yet not use it to prove the constancy of the speed of light?
Because its constancy is relative to the dimensions in which it is measured. When these dimensions change as SR predicts they do, the speed of light changes with them which holds it constant in every frame it is measured.
How does the speed of light change? (which is DaleSpam's argument)
It changes with and "as" the dimensions that comprise it. This does not mean we can measure the change directly any more than we can measure the change in dimensions directly. But as the evidence of this change is empirically verified by the clocks of A, then the validity of SR demands we acknowledge this change is equally valid evidence of the change in light speed necessary to hold it constant for the frame in which the change of dimension occurred.

This is where DaleSpam jumps up yelling "Hand Waving, Hand Waving, it's all a bunch of Hand Waving.
Show me the math"
I've tried to explain the math is just as he has seen it a thousand times before. There is nothing new in the math. It is essentially a case of understanding what it means to apply the math, specifically the Lorentz factor.
1/sqrt(1-v^2/c^2)
This is a ratio of dimension, 1 over a function of CHANGE of dimension. A function driven by the relative measure known as v and the constant (axiomatic) measure known as c.
I can't rewrite this any differently without it meaning something else. So how I am expected to show DaleSpam math he has not already seen is beyond me.
 
  • #84
Chrisc said:
I've not changed my argument
Then your argument still stands refuted. You simply cannot derive a change in c without erroneously mixing frames, as we showed above.
 
  • #85
LOL, is this still going on? :smile:
\uparrow​
(rhetorical question)
 
  • #86
Derive that! You're mixing frames!

Oh, sorry, it is getting to be a reflex. :smile:
 
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  • #87
Chrisc said:
One last appeal to your ...
10/20 = 1/2
If I gave you 10 dollars over twenty days or 1 dollar over 2 days, I would in each case give you the same thing, a ratio of money/days that is a constant $0.50/day.
I think you will agree the ratio of money/days remains constant and if all you could ever look at was the money/day you would argue (as your are now) that there is no difference in the money/day in either case.
I am simply arguing that since you can look at more than the money/day in that you can see that the time of A is different than the time of B, you must consider the magnitude of the ratio they both agree on is different between them. One gets a total of 10 dollars, the other a total of 1 dollar.

Oi, is someone using my economic theory without attribution?

Chrisc, maybe the problem here is that you are only thinking of one factor. I discussed a sort of economic theory of spacetime with DaleSpam a while back.

Think of it this way, you have a constant income of spacetime dollars - ct spacetime dollars per t. You can spend it just sitting around doing nothing, which means you spend it in terms of time (c.t_{you}). You might notice that I split mine up and spend part of my income on moving from one place to another (distance of v_{me}.t_{me}) and the remainder goes up in time (c.t_{me}) . The exchange rate depends on how long I take to move from one place to another, but the end result is that the spacetime dollars I spent my distance traveled and my time elapsed will equal the spacetime dollars you spent on your time elapsed (and your distance traveled which was zero (v_{you} = 0) ):

\sqrt{v.t_{me}^{2} + c.t_{me}^{2}} = c.t_{you}

The same sort of equation can be used for a rod at rest. A rod at rest has simultaneous ends, the value of the simultaneous ends of a rod which has a length of x is x spacetime dollars.

Relative to you, that rod can convert some of that length into motion (this is not rational economics here) - this is giving the rod a time component, and will make the ends of the rod non-simultaneous to you. The magnitude of the non-simultaneity (MNS) and the length of the rod will vector sum to the resting length of the rod:

x_{at rest} = \sqrt{x_{in motion}^{2} + MNS_{in motion}^{2}} ... (1)



Finally, the same sort of equation can be used for a clock. A clock at rest, with colocal ticks and tocks, has a time value of ct_{at rest} - where t_{at rest} is the number of ticks and tocks, not the period between each tick and tock. The clock can convert some of that, relative to you, into motion but the ticks and the tocks will not be colocal. The vector sum of the values, time value in motion plus the extent of non-colocality (ENC) of the clock in motion will add up to the rest time value:

ct_{(at rest)} = \sqrt{ct_{(in motion)}^{2} + ENC_{in motion}^{2}} ... (2)


...


Equations (1) and (2) can be more balanced, if one considers a zero MNS_{at rest} and a zero ENC_{at rest}:

\sqrt{x_{at rest}^{2} + MNS_{at rest}^{2}} = \sqrt{x_{in motion}^{2} + MNS_{in motion}^{2}}

and

\sqrt{ct_{(at rest)}^{2} + ENC_{at rest}^{2}} = \sqrt{ct_{(in motion)}^{2} + ENC_{in motion}^{2}}

Leaving these out is possibly where a lot of confusion comes in.

Anyways, in conclusion, if you "make" the ticks and tocks of a clock non-local or you "make" the ends of a rod non-simultaneous, by giving them motion relative to you, then you will reduce the number of tick and tocks or contract the rod to an extent equivalent to the extent to which the ticks and tocks are non-local or the ends of the rod are non-simultaneous.

...


No-one but me may understand this "economic theory", but the by the state of the world economy, no-one understands the real thing either :smile:

cheers,

neopolitan

PS In terms of the quoted section, you could say that one guy got $10 for just sitting there, the other got only $1 but did get to do some very fast, mind broadening travel (since the traveling one spends less spacetime money on time, he could arrive back home after twenty days of the $10 guys time having only 2 days on his clock, qualifying for only 2 days' pay).
 
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  • #88
Going back to mixing quantities across frames. If we calculate x'/t we get

\frac{x'}{t}=\frac{x\cosh(\beta)+t\sinh(\beta)}{t}=c\cosh(\beta)+\sinh(\beta)

The across frame quantity x'/t which Chrisc claims represents a velocity can be greater than c so it is not governed by relativity and has no physical significance within the framework of SR.
 
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  • #89
Mentz114 said:
Going back to mixing quantities across frames. If we calculate x'/t we get

\frac{x'}{t}=\frac{x\cosh(\beta)+t\sinh(\beta)}{t}=c\cosh(\beta)+\sinh(\beta)

The across frame quantity x'/t which Chrisc claims represents a velocity can be greater than c so it is not governed by relativity and has no physical significance within the framework of SR.

Thanks Mentz114, that is a problem, but not what I've said.
It seems DaleSpam's insistence that I have mixed frames has convinced everyone.
 
  • #90
DaleSpam said:
Then your argument still stands refuted. You simply cannot derive a change in c without erroneously mixing frames, as we showed above.

You are not listening.
Go back and read post #50, lines 14 and 15.
They state that c DOES NOT EQUAL x/t1
and c DOES NOT EQUAL x1/t

It is because c ≠ x1/t
and c ≠ x/t1
which is to say c ≠ BLength/ATime
and c ≠ ALength/BTime
that one can say
BLength ≠ ALength
BTime ≠ ATime
therefore
BLength/BTime ≠ ALength/ATime
and
c = BLength/BTime ≠ ALength/ATime = c
 

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