Superconductivity at room temperature??

[ben m]

Lets say I have a 1m^3 square block of glass made on earth with a refraction index of 1, with all sides coated with a thin slightly reflective dielectric say MgFl .
I also have a clock I made with a piece of radioactive unobtanium which decays at a rate of 10e15 disintigrations per second. I count and average the disintegrations and derive a percise 10 Ghz clock (also confirmed on earth).

This clock should slow as with any clock in the high speed reference frame of the traveler, correct?

All good so far, and this is a very useful way of thinking about it.

I now use this clock to fire a laser producing a 0.05ns pulse through the glass block (normal to the direction of travel) of the ship. The pulse partially reflects from the 2 interfaces on the block and returns back to the laser where a pin diode picks up the reflection from the far side of the block and stops the timer which was started by the inital laser signal.

Yep. You, on the ship, say "I just timed a 2-meter light path with a 10 GHz clock; it took 66.8 ticks, so I measured 2.99e10 m/s". From the ground, an observer would say (seeing your clock as slow AND the block as contracted) "He just timed a 1.98-meter light path with a 9.9-GHz clock, which it took 66.8 ticks, so he measured 2.99e10 m/s".

I reorient the laser to the block perpendicular to the ships direction of travel and repeat the above measurement.

Yep. You, on the ship, say "I just timed a 2-meter light path with my 10-GHz clock and got 66.8 ticks, or 2.99e8 m/s". From the ground, remember, the light is traveling *more than* two meters---it's got some velocity in the direction of the ship, PLUS the perpendicular velocity that gets it across the block, so it's following a zigzag path through space. Over this distance---which, according to the ground observer, is the actual distance the light has to travel---it's also seen to go at 2.99x10^8 m/s.

It does all work out. It's hard to see the exact form of the agreement without using the math, though.

 

[BowlOfRed]

Now, if the speed of light is the same in any frame (with mass) and the ruler is the speed of light which is unaffected by contraction then there appears to be a conflict if the block is actually shorter in the travel direction.

Not if the clocks are also different between the frames. Which they are.

Another conflict is if the clock is actually running slower in the ships frame, the speed of light from a distant star measured in that frame used to clock the incoming light (viewed through the windscreen of the ship) would be measured at a higher speed than c using the ships clock (which is slower than the same clock on earth).

I don't like that you are using the phrase "actually running slower". It sounds to me like you are assuming some sort of absolute frame. Remember that between inertial frames, the observations are symmetric.

If A and B are in motion relative to each other, A would see B's clock running slow and B would see A's clock running slow.

 

[flyer]

ben m

Lets consider for the moment only the traveler in his reference frame at some fraction of c
in an inertial frame (no acceleration). The coordinate transform is not needed in the inertial frame of the traveler.

He is continually aging slower than his brother, and the unobtanium clock is also running slower than it was on earth.
But even if the clock is running slower but consistently, a del-t between the perpendicular light paths going through
the glass should be evident if the block is "really" physically shorter if c is consistant for all frames regardless of their motion.

BowlOfRed

"I don't like that you are using the phrase "actually running slower". It sounds to me like you are assuming some sort of absolute frame."

When the twins meet up their ages are different according to ben m, which would imply the travelers clock, biological or otherwise
must have run slower than the earth bound twins clock, or am I wrong? Is one of the clocks actually not running slower, and if it isn't
how is it their ages are different on their second meeting?

 

[ben m]

ben m

Lets consider for the moment only the traveler in his reference frame at some fraction of c
in an inertial frame (no acceleration). The coordinate transform is not needed in the inertial frame of the traveler.

He is continually aging slower than his brother, and the unobtanium clock is also running slower than it was on earth.
But even if the clock is running slower but consistently, a del-t between the perpendicular light paths going through
the glass should be evident if the block is "really" physically shorter if c is consistant for all frames regardless of their motion.

In his frame, i.e. according to his rulers and clocks, the glass is not contracted. The guy on the spaceship is, according to any measurement he can actually do, shooting beams of light through a nice square block, and of course it takes the same amount of time in either the parallel or perpendicular directions.

When the twins meet up their ages are different according to ben m, which would imply the travelers clock, biological or otherwise
must have run slower than the earth bound twins clock, or am I wrong? Is one of the clocks actually not running slower, and if it isn't
how is it their ages are different on their second meeting?

No. During the inertial-flight-out and the inertial-flight-homeward phases, both observers say that the other observer's clock is running slower. During the phase where the space-ship twin is accelerating to turn around, he temporarily sees the earthbound twin's clock running much faster (and vice-versa); that's where the age-difference accumulates.

If the outbound twin had not tried to turn around, the paradoxical-sounding disagreement about the sign of the clock-offset would be mixed in with related disagreements about the definition of simulteneity, and no paradoxes actually result.

 

[flyer]

Not if the clocks are also different between the frames. Which they are.

I don't understand, are you saying the speed of light is different in different frames ?

I don't like that you are using the phrase "actually running slower". It sounds to me like you are assuming some sort of absolute frame. Remember that between inertial frames, the observations are symmetric.

If A and B are in motion relative to each other, A would see B's clock running slow and B would see A's clock running slow.

The travelers clock must be (have been) running slower than his earthly brother if he ends up younger than his brother on their second meeting, or not?

 

[flyer]

In his frame, i.e. according to his rulers and clocks, the glass is not contracted. The guy on the spaceship is, according to any measurement he can actually do, shooting beams of light through a nice square block, and of course it takes the same amount of time in either the parallel or perpendicular directions.

In any frame c is c, is it not, and we are only considering his inertial frame at the moment. The laser pulse doesn't care about frames, its propagation speed will be c normal to the direction of travel or perpendicular to it. If the glass block is actually shorter I agree a measuring tape would not see this due to contraction, but light speed is not subject to contraction in any direction, so if the block is (compressed) in the direction normal to travel, this should be indicated by the propagation time, regardless if the clock is slow or not, a del-t should be evident between the two mesurements.

No. During the inertial-flight-out and the inertial-flight-homeward phases, both observers say that the other observer's clock is running slower. During the phase where the space-ship twin is accelerating to turn around, he temporarily sees the earthbound twin's clock running much faster (and vice-versa); that's where the age-difference accumulates.

If the outbound twin had not tried to turn around, the paradoxical-sounding disagreement about the sign of the clock-offset would be mixed in with related disagreements about the definition of simulteneity, and no paradoxes actually result.

So the time dilation (causing the end age difference) actually only occurs during the acceleration phase, or when the traveler is not in an inertial frame, is this correct ?

 

[BowlOfRed]

Here, try reading this link. See if this makes it better or worse.

http://www.phys.unsw.edu.au/einsteinlight/jw/module4_time_dilation.htm

 

[ben m]

If the glass block is actually shorter I agree a measuring tape would not see this due to contraction, but light speed is not subject to contraction in any direction, so if the block is (compressed) in the direction normal to travel, this should be indicated by the propagation time, regardless if the clock is slow or not, a del-t should be evident between the two mesurements.

Try working through the math. Don't forget that the emitter, reflector, and the detector are all moving. Suppose that the light is emitted at position x1=0 and time t1=0, using the rulers on the ground. Figure out at what time *and position* the light is detected (x2,t2). Repeat the exercise using the moving ruler and clock.

The ground observer will say that there's an asymmetry---in the parallel case, the cube is shortened, but also the time is shortened (because the detector "catches up" with the beam, in a sense), so the light still appears to move at c in both orientations. The moving observer will see no asymmetry, and the light appears to move at c in both orientations.

 

[BowlOfRed]

So the time dilation (causing the end age difference) actually only occurs during the acceleration phase, or when the traveler is not in an inertial frame, is this correct ?

Time dilation (observation of moving clocks running slowly) is a direct consequence of a constant 'c' and pythagoras. That happens even without acceleration.

The whole twin paradox where the ages are different after rejoining requires a more complex treatment.

 

[flyer]

Here, try reading this link. See if this makes it better or worse.

wwwdotphys.unsw.edu.au/einsteinlight/jw/module4_time_dilation.htm

I have read this before and several others, but it doesn't seem to address what happens in the single inertial frame of the traveler without the second observer.
Thanks

 

[flyer]

Try working through the math. Don't forget that the emitter, reflector, and the detector are all moving. Suppose that the light is emitted at position x1=0 and time t1=0, using the rulers on the ground. Figure out at what time *and position* the light is detected (x2,t2). Repeat the exercise using the moving ruler and clock.

The ground observer will say that there's an asymmetry---in the parallel case, the cube is shortened, but also the time is shortened (because the detector "catches up" with the beam, in a sense), so the light still appears to move at c in both orientations. The moving observer will see no asymmetry, and the light appears to move at c in both orientations.

I believe you, when applying the transform to two frames, but I am trying to get what happens in the travelers frame, regardless of the second observer.
If light cannot be used in an inertial frame to measure distance, why not.

To understand something, you need to know where it comes from.
The mathematical derivations came after insight, what was the insight.

 

[ben m]

I believe you, when applying the transform to two frames, but I am trying to get what happens in the travelers frame, regardless of the second observer.

In the traveler's frame, the cube is a cube. The traveler measures that it's L meters long and L meters wide; and that light will take time t = 2L/c to go across and back in any direction. What's the problem?

The only time this thing looks non-cubic (and the only reason you thought to call the cube "shortened" in one direction, and the only reason you suspected an asymmetry) is when you try to measure it with an observer---with an Earthbound ruler---that's moving relative to the cube. That observer sees a more complicated measurement sequence, including both a length-asymmetry (which, yes, he can measure using the speed of light) and a displacement between the emission-event and the detection-event. What's the problem?

 

[BowlOfRed]

I have read this before and several others, but it doesn't seem to address what happens in the single inertial frame of the traveler without the second observer.
Thanks

Are you asking what happens when the device being measured and the observer are in the same reference frame (either both on earth or both on a ship)?

If so, then there is no measured contraction, no measured time dilation, and no difference between any measured direction in the manufactured cube.

This seems to be a trivial case, so I am wondering if I am misinterpreting your question.

 

[ben m]

To understand something, you need to know where it comes from.
The mathematical derivations came after insight, what was the insight.

That's not correct. There are a million ways to have the "insight" that you want to see what happens if clock-rates and distances and motion are connected. There is only one way in which it actually makes sense, and to tell the difference between the 999,999 nonsense-relativities and the 1 special-relativity you need math. The questions you are asking are about the difference between the relativity-that-actually-works and the 999,999 vague-ideas-that-don't. That difference is a mathematical one.

In practice, physicists are usually asked to develop the math and the intuition at the same time.

 

[flyer]

Are you asking what happens when the device being measured and the observer are in the same reference frame (either both on earth or both on a ship)?

Exactly

If so, then there is no measured contraction, no measured time dilation, and no difference between any measured direction in the manufactured cube.

This seems to be a trivial case, so I am wondering if I am misinterpreting your question.

Nope, it's probibly trivial ,but I am trying to understand it.
I will do some more reading.
Thanks for your time guys.

 

[flyer]

That's not correct. There are a million ways to have the "insight" that you want to see what happens if clock-rates and distances and motion are connected. There is only one way in which it actually makes sense, and to tell the difference between the 999,999 nonsense-relativities and the 1 special-relativity you need math. The questions you are asking are about the difference between the relativity-that-actually-works and the 999,999 vague-ideas-that-don't. That difference is a mathematical one.

In practice, physicists are usually asked to develop the math and the intuition at the same time.

I believe you must verify your postulate with the mathematics of course, but the postulate comes from
insight (and the understanding of the governing math of course), but we are human. Einstein envisioned
"riding a beam of light", the math came later (maybe only seconds later) . I agree, there are countless crackpot theories out there but
if the math doesn't hold up they are just that. If the math works, its on to an experiment, if possible and a prediction. Calculators alone don't make theories.

Just my opinion.

 

[ben m]

One thing you may be missing:

The traveler is sitting there with his L x L x L cube. Earth-man flies by with his funny ruler and the traveler watches him do experiments which "conclude" that the cube is L x L x L/gamma. According to the traveler's instruments, the L/gamma conclusion was a "mistake"---he'd say that Earth-man's measurements happened in a weird sequence, and that the L/gamma he measured was not in fact the length of the cube.

This is an example of the "relativity of simulteneity".

 

[Reality Check]

Exactly

Then the answer is easy: Both obervers get the same measurments. Both observers measure that the clock ticks at that same rate . Both observers measure the same lengths.

 

[Reality Check]

I believe you must verify your postulate with the mathematics of course, but the postulate comes from
insight (and the understanding of the governing math of course), but we are human. Einstein envisioned
"riding a beam of light", the math came later (maybe only seconds later) . I agree, there are countless crackpot theories out there but
if the math doesn't hold up they are just that. If the math works, its on to an experiment, if possible and a prediction. Calculators alone don't make theories.

Just my opinion.

You seem to be confusing the general definition of theory as just an idea with the definition of theory used in science - a scientific theory (basically an idea + empirical observations + math)
The "countless crackpot theories" that have invalid math are invalid scientific theories. If they do not have math then they are not even theories.

 

[leonAzul]

I can feel it coming on myself sometimes. A kind of brain calcification. Not as symptomatic as our friend, but of the same type for sure.

I have hesitated to respond to this without JP being present because I would prefer to speak to him directly rather than in absentia.

One of the reasons I continue to follow this thread, among others, is my own sense of incipient ossification of my brain. This seems to come about not so much from a poor education, but rather from a natural desire to "get things done", which sometimes results in the neglect of continuing to cultivate the skills required for acquiring and communicating knowledge over the immediate application of knowledge.

JP has a commendable CV in the private sector in areas that include Physics and Materials Research. Through this he also gained recognition as a lecturer within academia. What is lacking is the continued interaction with other scientists that would facilitate the ability to successfully undergo peer review. The mantra "publish or perish" is not so much a defense of dogma or political foolishness, but rather an admonition to keep in mind that the best ideas, no matter how brilliant, are useless unless they can be communicated and reviewed publicly and collaboratively.