Relativity?

How does science work? And what's all this about quantum mechanics?

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davidm
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Re: Relativity?

Post by davidm »

:?
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Noax
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Re: Relativity?

Post by Noax »

This is a better thought experiment since it doesn't presume something known to not be possible.
Viveka wrote: Fri Nov 17, 2017 2:06 amIf light is given off as a spherical wavefront from a certain light-clock, and if the motion of the light-clock on a train is sufficient, then length-contraction and time-dilation would occur.
What is a light clock? I know uwot had one on his site, but it was just a photon bouncing unmeasured between a parallel pair of mirrors. No wavefront is given off from that setup. So I presume a strobe light that gives off one pulse, or perhaps a series of them at regular intervals. Correct me if I misrepresented your scenario. All clocks measure the same thing, just some with more precision than others.

Speed of light is fixed in any frame, so in any frame, each pulse expands in a sphere, not deformed into an ellipsoid. The motion of the light source does not affect the expanding sphere. The sphere cannot be motion-dilated since it is growing at the same speed in all directions, and thus the center is stationary in the frame in which it is measured. Choose a different frame and the sphere center must be stationary in that one as well.

I know... This counters your intuition so I'm proven wrong. Go on. Say it.
and, on top of that, it wouldn't travel as a sphere even though it must in all inertial frames due to the invariance of the speed of light in all directions.
No, if light speed is constant, the sphere cannot travel. It just grows in place.
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Noax
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Re: Relativity?

Post by Noax »

Addendum: If the strobe puts out multiple pulses, the spheres will be concentric only in a frame where the strobe source is stationary. If the strobe is moving, each pulse originates from a different location and the spheres are not concentric.
Viveka
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Re: Relativity?

Post by Viveka »

Noax wrote: Fri Nov 17, 2017 3:17 am This is a better thought experiment since it doesn't presume something known to not be possible.
Viveka wrote: Fri Nov 17, 2017 2:06 amIf light is given off as a spherical wavefront from a certain light-clock, and if the motion of the light-clock on a train is sufficient, then length-contraction and time-dilation would occur.
What is a light clock? I know uwot had one on his site, but it was just a photon bouncing unmeasured between a parallel pair of mirrors. No wavefront is given off from that setup. So I presume a strobe light that gives off one pulse, or perhaps a series of them at regular intervals. Correct me if I misrepresented your scenario. All clocks measure the same thing, just some with more precision than others.
A light-clock is a photon bouncing up and down vertically with two mirrors above and below. However, in my thought-experiment the light itself is a spherical wave.
Noax wrote: Fri Nov 17, 2017 3:17 am Speed of light is fixed in any frame, so in any frame, each pulse expands in a sphere, not deformed into an ellipsoid. The motion of the light source does not affect the expanding sphere. The sphere cannot be motion-dilated since it is growing at the same speed in all directions, and thus the center is stationary in the frame in which it is measured. Choose a different frame and the sphere center must be stationary in that one as well.

I know... This counters your intuition so I'm proven wrong. Go on. Say it.
and, on top of that, it wouldn't travel as a sphere even though it must in all inertial frames due to the invariance of the speed of light in all directions.
No, if light speed is constant, the sphere cannot travel. It just grows in place.
Since the light clock uses light, it cannot change its speed of light, but rather the length-contraction or time-dilation must occur whenever there is appreciable approach of the speed of light in order to change how fast it 'ticks'.Thus, whenever length-contraction or time-dilation occurred it would only change how fast it 'ticks' and thereby change the geometry of the sphere into an ellipsoid. Here's the contradiction: the sphere of light must both be deformed through 'ticking' slower or faster due to time dilation and length contraction, but, yet, it cannot be deformed through the invariance of the speed of light.
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Noax
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Re: Relativity?

Post by Noax »

Viveka wrote: Fri Nov 17, 2017 6:07 am However, in my thought-experiment the light itself is a spherical wave
Don't know what you mean by this.
Viveka
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Re: Relativity?

Post by Viveka »

Noax wrote: Fri Nov 17, 2017 7:00 am
Viveka wrote: Fri Nov 17, 2017 6:07 am However, in my thought-experiment the light itself is a spherical wave
Don't know what you mean by this.
A wave of electromagnetism extending spherically throughout space at c velocity. In other words, not the particle of light but the wave of light.

Don't play dumb. You very well know what a light-wave is don't you?
uwot
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Re: Relativity?

Post by uwot »

Viveka wrote: Fri Nov 17, 2017 6:07 am...in my thought-experiment the light itself is a spherical wave.
I think this is based on a misunderstanding of quantum mechanics. It is not the light wave that is spherical, rather the wave function. This, in essence, is a response to the two slit experiment which shows, conclusively, that photons are not points of energy. In the 'shut up and calculate' school of physics, it doesn't matter what that means in physical terms, because the maths works.
The issue is described by Nobel Prize winner Robert Laughlin:
"It is ironic that Einstein's most creative work, the general theory of relativity, should boil down to conceptualizing space as a medium when his original premise [in special relativity] was that no such medium existed [..] The word 'ether' has extremely negative connotations in theoretical physics because of its past association with opposition to relativity. This is unfortunate because, stripped of these connotations, it rather nicely captures the way most physicists actually think about the vacuum…The modern concept of the vacuum of space, confirmed every day by experiment, is a relativistic ether. But we do not call it this because it is taboo."
In practise, this allows photons to be conceptualised as expanding wave fronts of a specific (quantum of) energy. Because of the electronic nature of most of our detection devices, that quantum of energy will only register if it triggers a quantum leap in an electron orbiting an atom. To do that, the whole of the energy has to be absorbed by the atom; but that energy is spread across the wavefront. It's as if the atom sucks up the whole of the wavefront (very loosely the collapse of the wave function), at which point we go 'Ah! There's the photon.' But since that can happen anywhere along the wavefront, until the wave causes a quantum leap, there is no real sense in which it is a photon in a specific place.
Viveka wrote: Fri Nov 17, 2017 6:07 amSince the light clock uses light, it cannot change its speed of light, but rather the length-contraction or time-dilation must occur whenever there is appreciable approach of the speed of light in order to change how fast it 'ticks'.Thus, whenever length-contraction or time-dilation occurred it would only change how fast it 'ticks' and thereby change the geometry of the sphere into an ellipsoid. Here's the contradiction: the sphere of light must both be deformed through 'ticking' slower or faster due to time dilation and length contraction, but, yet, it cannot be deformed through the invariance of the speed of light.
Right. This is based on a misunderstanding of special relativity. It is not the case that the speed of light doesn't change; the claim is that the speed of light in a vacuum will be measured as the same in any inertial frame. That would be very difficult to account for if there were any such thing as a true vacuum, but note that Laughlin describes the vacuum as a "relativistic ether" (some physicists think that is what the Higgs field is). In other words, 'space' is a substance that can be stretched and compressed, which is the basic premise of general relativity. In which case, even if light were a wave, as you describe, it would not be spherical, it's shape would follow whatever geodesics the local conditions (gravity and motion) generated.
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Re: Relativity?

Post by Eodnhoj7 »

Taking Davidm's ABC graph:

1) If viewing the graph, as non-moving, with ABC blinking at one moment the graph (surrounding space) would curve upon itself.
2) If viewing the graph, as non-moving, with ABC not-blinking at one moment the graph (surrounding space) would cease to curve.
3) ABC exist in a linear pattern, in a separate dimension of space simultaneously to the graph curving and ABC individually blinking.
Viveka
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Re: Relativity?

Post by Viveka »

uwot wrote: Fri Nov 17, 2017 9:12 am
Viveka wrote: Fri Nov 17, 2017 6:07 am...in my thought-experiment the light itself is a spherical wave.
I think this is based on a misunderstanding of quantum mechanics. It is not the light wave that is spherical, rather the wave function. This, in essence, is a response to the two slit experiment which shows, conclusively, that photons are not points of energy. In the 'shut up and calculate' school of physics, it doesn't matter what that means in physical terms, because the maths works.
The issue is described by Nobel Prize winner Robert Laughlin:
"It is ironic that Einstein's most creative work, the general theory of relativity, should boil down to conceptualizing space as a medium when his original premise [in special relativity] was that no such medium existed [..] The word 'ether' has extremely negative connotations in theoretical physics because of its past association with opposition to relativity. This is unfortunate because, stripped of these connotations, it rather nicely captures the way most physicists actually think about the vacuum…The modern concept of the vacuum of space, confirmed every day by experiment, is a relativistic ether. But we do not call it this because it is taboo."
In practise, this allows photons to be conceptualised as expanding wave fronts of a specific (quantum of) energy. Because of the electronic nature of most of our detection devices, that quantum of energy will only register if it triggers a quantum leap in an electron orbiting an atom. To do that, the whole of the energy has to be absorbed by the atom; but that energy is spread across the wavefront. It's as if the atom sucks up the whole of the wavefront (very loosely the collapse of the wave function), at which point we go 'Ah! There's the photon.' But since that can happen anywhere along the wavefront, until the wave causes a quantum leap, there is no real sense in which it is a photon in a specific place.
I agree completely. The photon is quantum, but when it is a wave, it appears to be non-quantum, although when the wave is absorbed, it is a quantum. Hence Planck's Constant quantum multiplied by Non-quantum Frequency to get the Energy of the Photon.
uwot wrote: Fri Nov 17, 2017 9:12 am
Viveka wrote: Fri Nov 17, 2017 6:07 amSince the light clock uses light, it cannot change its speed of light, but rather the length-contraction or time-dilation must occur whenever there is appreciable approach of the speed of light in order to change how fast it 'ticks'.Thus, whenever length-contraction or time-dilation occurred it would only change how fast it 'ticks' and thereby change the geometry of the sphere into an ellipsoid. Here's the contradiction: the sphere of light must both be deformed through 'ticking' slower or faster due to time dilation and length contraction, but, yet, it cannot be deformed through the invariance of the speed of light.
Right. This is based on a misunderstanding of special relativity. It is not the case that the speed of light doesn't change; the claim is that the speed of light in a vacuum will be measured as the same in any inertial frame. That would be very difficult to account for if there were any such thing as a true vacuum, but note that Laughlin describes the vacuum as a "relativistic ether" (some physicists think that is what the Higgs field is). In other words, 'space' is a substance that can be stretched and compressed, which is the basic premise of general relativity. In which case, even if light were a wave, as you describe, it would not be spherical, it's shape would follow whatever geodesics the local conditions (gravity and motion) generated.
If its shape is morphed in any way, such as through time-dilation, length-contraction, or simply following geodesics, in your 'relativistic ether' it must violate the invariance of the speed of light due to changing its geometry as a non-spherical wave-front. However, it must follow a spherical geometry, and therefore it is violating the amount of 'ticks' that are faster or slower due to the ethereal relativity.
ken
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Re: Relativity?

Post by ken »

uwot wrote: Wed Nov 01, 2017 10:28 pm
ken wrote: Tue Oct 31, 2017 5:35 amAre you suggesting here that what an observer sees travelling at close to the speed of light has been demonstrated?
No human has travelled at anything like light speed; the current record is, from memory, something like 23 000mph. Even at that speed, the effects relativity are much too slight to be observed by a human being. However, atomic clocks are accurate enough to demonstrate the effects of time dilation at much lower speeds, and every time they show results that agree with relativity. Given that human beings are made of the same subatomic particles as atomic clocks, it is reasonable to extrapolate that they will be affected in precisely the same manner.
So, it is only a guess, is that right?

Also, did one of these atomic clocks, supposedly, speed up and not slow down when traveling in a certain direction?
davidm
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Re: Relativity?

Post by davidm »

ken wrote: Fri Nov 17, 2017 9:37 pm
uwot wrote: Wed Nov 01, 2017 10:28 pm
ken wrote: Tue Oct 31, 2017 5:35 amAre you suggesting here that what an observer sees travelling at close to the speed of light has been demonstrated?
No human has travelled at anything like light speed; the current record is, from memory, something like 23 000mph. Even at that speed, the effects relativity are much too slight to be observed by a human being. However, atomic clocks are accurate enough to demonstrate the effects of time dilation at much lower speeds, and every time they show results that agree with relativity. Given that human beings are made of the same subatomic particles as atomic clocks, it is reasonable to extrapolate that they will be affected in precisely the same manner.
So, it is only a guess, is that right?
No, that's not right. :?
ken
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Re: Relativity?

Post by ken »

davidm wrote: Fri Nov 17, 2017 10:10 pm
ken wrote: Fri Nov 17, 2017 9:37 pm
uwot wrote: Wed Nov 01, 2017 10:28 pm
No human has travelled at anything like light speed; the current record is, from memory, something like 23 000mph. Even at that speed, the effects relativity are much too slight to be observed by a human being. However, atomic clocks are accurate enough to demonstrate the effects of time dilation at much lower speeds, and every time they show results that agree with relativity. Given that human beings are made of the same subatomic particles as atomic clocks, it is reasonable to extrapolate that they will be affected in precisely the same manner.
So, it is only a guess, is that right?
No, that's not right. :?
So where is the actual evidence that human beings age slower when they travel?

What did they compare it with?

What was it measured against?
davidm
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Re: Relativity?

Post by davidm »

ken wrote: Fri Nov 17, 2017 10:39 pm
davidm wrote: Fri Nov 17, 2017 10:10 pm
ken wrote: Fri Nov 17, 2017 9:37 pm

So, it is only a guess, is that right?
No, that's not right. :?
So where is the actual evidence that human beings age slower when they travel?
Here's why astronauts age slower than people on earth.
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Noax
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Re: Relativity?

Post by Noax »

ken wrote: Fri Nov 17, 2017 10:39 pm So where is the actual evidence that human beings age slower when they travel?
That's like arguing that fire has been shown to kill others, but no actual evidence that it might kill you.
Yes, your suggestion that humans, alone among all material objects, are immune from physics, is equally plausible. 10 points for Hufflepuff.
Last edited by Noax on Sat Nov 18, 2017 12:08 am, edited 2 times in total.
davidm
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Re: Relativity?

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