Why we cant measure the speed of light

a reply to: More1ThanAny1

Two things wrong with this approach 1st photons do not actually have a size that could be measured. According to Quantum Mechanics, a photon has no size at all . If we treat it as a particle it is simply a point in space. If it is treated as a wave, it has wavelength and amplitude but no size.

Second problem we would have to rely on photons bouncing back to our detector or camera again measuring light traveling in more than one direction away from us and back again.

a reply to: blackcrowe

Ok having read through this your simply not understanding this at all. Your experiment here shows that light traveling in 2 directions always equals C. We already know this fact its been proven in multiple experiments. And has nothing to do with the topic of this thread. Im trying to get people to question the world around them because after all that is the true sign of intelligence.

"Measure", is man's way of understanding, (getting a grip) with what they can, or can't understand.
"Science says", a star died 2 million years ago.. But we still see the "light", because of the "speed of light" and how far the Star was away, when it "died".

Science, "search for truth", started out with a noble purpose. It has become a "find evidence against" a logical hypothesis.

One of the greatest "pyramid schemes" ever....
"We know this is the reallity". But is it "really"? ...We're all "EDUCATED"! But we still, "have many questions"!.. "Gofund us"!

According to the idiots, (at least in my country)...
"Newton",.."discovered gravity"!

Are you going to tell me? The "Neanderthal" before "Newton", ... Didn't know how to "calculate" the "trajectory" of rock, spear or throwing stick, in relationship to his/her ability of force.. To "thrust make effort" to get dinner?..

"Scientists" are idiots.

originally posted by: dragonridr
Two things wrong with this approach 1st photons do not actually have a size that could be measured. According to Quantum Mechanics, a photon has no size at all . If we treat it as a particle it is simply a point in space. If it is treated as a wave, it has wavelength and amplitude but no size.

That is according to quantum mechanics... I wouldn't say that makes the approach wrong though. That just means you have a definition problem. Light is a wave, it's not a particle. Some would say its a soliton-wave with a circular ellipsoid shape and its size is length λ, and its diameter is λ / π.

originally posted by: dragonridr
Second problem we would have to rely on photons bouncing back to our detector or camera again measuring light traveling in more than one direction away from us and back again.

You must not have understood my single point measuring system. You only need a single detector that can measure when the light quanta wave first hits it, and when the wave is done hitting it (or completely absorbed), and know its length.

a reply to: More1ThanAny1

Ok, I will try explaining it to you this way we have a measuring device at point a. The only way to get photons to return to point a is refraction we are either going to split it or bounce it. Because of this, we are not measuring the speed in only one direction will always be 2 or more. Then there is the signal itself from the photon detector telling us the start and end. Those are photons or em waves,

Finally, if photons actually have size it is too small for us to even measure. Meaning all we can do is treat it as a wave or point particle there would be no size to use as a reference frame. So we would have no idea what any of this data would mean.

To dragonridr and More1ThanAny1.

Yes, it's right. I don't understand the point.

It is difficult to understand when the author of the OP claims that we assume the speed of light. While also claiming that the speed is known.

Please watch the video linked below.

Richard Feynman. How did we find the speed of light.

Einstein is not mentioned, neither is measuring light in 2 directions or bouncing off a mirror.

a reply to: dragonridr

Ok, I will try explaining it to you this way. We don't need the photon to return anywhere. We are measuring in only one direction with a single detector. You emit photons at a very special measuring device that understands the start and the end of the photon itself and does all the timing. The photon doesn't need to return to the emitter.

How you define the size of a photon is another topic.

a reply to: blackcrowe

Every method we use involved measuring light that has taken more than 1 path. We have yet to measure light traveled in just a single direction. To further confuse people its now impossible to get anything other than c in an experiment because scientists cooked the books.

The meter is the distance traveled by a beam of light in a vacuum in 1/299,792,458 of a second, where the second is based on the radioactive decay of the cesium-133 atom.

Defining the meter in terms of the speed of light basically fixes the speed of light at 299,792,458 m/s. If an experiment yields a different result, it just means the apparatus is faulty. Rather than conducting more experiments to measure the speed of light, scientists use the speed of light to calibrate their equipment.

Meaning now we could not even detect if we were wrong. All experiments are rigged because we are using the speed of light as our measuring device we cannot get a different answer for C.

a reply to: dragonridr

Every method we use involved measuring light that has taken more than 1 path. We have yet to measure light traveled in just a single direction.

It doesn't mater how many paths you use. From the lights point of view. It travels forwards only for the total distance. Effectively, it is a one way measurement.

If c is different. How is space exploration possible?

There is currently a probe orbiting and observing our sun. For one.

Any inaccuracy would mean total failure.

Or is space exploration rigged? It is only an experiment after all.

originally posted by: blackcrowe
a reply to: dragonridr

Every method we use involved measuring light that has taken more than 1 path. We have yet to measure light traveled in just a single direction.

It doesn't mater how many paths you use. From the lights point of view. It travels forwards only for the total distance. Effectively, it is a one way measurement.

If c is different. How is space exploration possible?

There is currently a probe orbiting and observing our sun. For one.

Any inaccuracy would mean total failure.

Or is space exploration rigged? It is only an experiment after all.

As long as we get c for our value it has no effect on probes space exploration or even our GPS satellites. Here i suggest taking the time to watch this video.

I see the problem.

What you're saying is that all everybody has ever done was measure the average speed of light in two opposite directions (or, for that matter, on any "circular" path that starts and ends at the same point), which could potentially hide the actual fact that speed of light is different from C when measured in just one direction.

Or, mathematically: (C+dC) + (C-dC) = 2*C => always giving C when divided by 2 (and dC being that slight difference to C when measured in just one direction)

Well, the problem is that dC should then also depend on the absolute direction and speed of the measuring equipment (including the clocks), which, of course, Relativity made away with by making the assumption (its very first axiom) that it simply doesn't. Being just an assumption, that has never actually been experimentally verified, hence the need for measuring the speed of light in just one direction as an actual experimental proof of that assumption.

From everything I know, the only way to actually make such a measurement would involve these things:

a) have a (micro) black hole at position of rest in (relative to) the Eart's frame of reference,

b) that (micro) black hole will eventually (rather quickly, I imagine) align its axis of rotation with Earth's absolute direction of movement (because that's what black holes do in a holographic-one-actual-dimension-less universe), giving you the first required condition to proceed with the experiment,

c) have two clocks at rest in Earth's frame of reference, both clocks at the same distance away from the (micro) black hole, and both lying in black hole's plane of rotation (preferably on the opposite sides of the black hole's axis of rotation),

d) synchronize the clocks (potentially problematic, but so-called "quantum entanglement" (generating a pair of photons from the same atomic source) may help with that,

e) move both clocks in opposite directions, at the same speed, and they will remain synchronized,

f) have a source of light (laser) at first clock's position, and generate a time-encoded pulse, so that the pulse itself carries the (information about) time as measured by the first clock,

g) have a detector at the second clock's position, read the pulse, and calculate C in that direction,

h) repeat the measurement in the opposite direction

All of this will, of course, give you only the actual speed of light in a plane perpendicular to your absolute direction of movement. Ideally, you'd want to be able to make that measurement in any direction, and in order to do that, you'd have to make some adjustments to the experiment, as follows:

c) have two clock at rest in Earth's frame of reference, both locks at the same distance away from the (micro) black hole, on the opposite sides relative to the black hole's center point,

e) move both clocks in opposite directions, at the same speed, and they will NOT remain synchronized,

e.1) synchronize the clocks again by adding (calculated) +dT and -dT to clocks (potentially problematic if your assumption about the formula, used to calculate dT, being correct is actually wrong), respectively, depending on their direction of movement

All the other (unmentioned) steps should stay the same.

Does all of this answer your question (pertaining to the experiment only, and not to why black holes behave like they do)?

a reply to: dragonridr

I have just watched it.

What does he mean when he says "c over 2" at the 14.14 mark?

Does he mean c x c Edit. c being the measured speed x measured speed. A big number. Or c^2 ( c squared)?

I have already explained c^2 and that c and c^2 are equal to each other. But 180 deg rotated to each other.

The video is not worth watching.

a reply to: blackcrowe

1+4 is equal to 2+3 this doesnt mean the number one and 3 are the same. c^2 may not be the same as C + C equal If C is not the same in all directions . By the way you seem to want to think in left or right thats not the case. It would be in reference to a frame of reference. So anytime a photon is altered could make it instatanous for example. if there is a diference it might not even be a huge diference wont know until we verify it.

I dont believe there will be a diference but until we figure a way to check we wont know for sure.

a reply to: clusterfok

Unusual approach to synchonize two clocks you get the outside the box award lol.

a reply to: dragonridr

In my question what is c over 2. I realised after logging off. He means half c.

So light travels to mars at half the speed of light. But the the return is instant making c the average.

There is no need for that to happen like that.

By the way you seem to want to think in left or right thats not the case.

No. My whole point is that left or right, up or down or forwards or backwards are all only forwards from the lights perspective. Which is not being taken into account.

Good luck with it though.

originally posted by: moebius
a reply to: dragonridr

You don't have to measure the speed of light to show that it is isotropic (same in any direction). See Mössbauer rotor experiments.

originally posted by: dragonridr
Problem is we have no way of knowing if light travels different speeds in different directions.

Dragonridr, did you ever respond to the comment by moebius?

originally posted by: clusterfok
b) that (micro) black hole will eventually (rather quickly, I imagine) align its axis of rotation with Earth's absolute direction of movement (because that's what black holes do in a holographic-one-actual-dimension-less universe), giving you the first required condition to proceed with the experiment,

According to Hawking's black hole radiation model (which hasn't been experimentally verified either), the micro black hole would evaporate almost instantly, which is widely thought to be probably true despite the lack of experimental verification:

Micro Black Hole Production and Evaporation

It has been conjectured that Micro Black Holes (MBH) may be formed in the presence of large extra dimensions. These MBHs have very small mass and they decay almost instantaneously.

e) move both clocks in opposite directions, at the same speed, and they will remain synchronized,

If you watched the Veritasium video, that's the kind of thing Derek says you can't do because if space time is different in different directions that may not be a valid assumption. In fact it's definitely not true where spacetime is different in different directions, like if you move one clock down and the other clock up in a lab on Earth at the same speed, those are opposite directions, but the clocks will not remain synchronized. By the way how would you know if you're moving them at the same speed or not? In the example I gave moving them in opposite directions, the passage of time is continually variable according to general relativity and if speed is displacement per unit time and you don't have a reliable clock since time is changing as you move it, it's hard to say you're moving them at the same speed with any certainty. Now you could add the qualification that the opposite directions must be "level" and not up or down, but that's still a problem if the different directions affect the passage of time differently. You're assuming they don't which they probably don't, but since that's the thing you're trying to prove, you can't assume it, it would end up being a circular proof which depended on your assumption.

Anyway, as long as you move the clocks "level" or in a uniform gravitational field, they should stay synchronized and almost certainly will, but I don't see how you can make that assumption and claim your experimental result proves anything.

Moebius' comment is interesting because if that's true, we may not be able to measure the one-way speed of light, but we don't need to if that experiment shows the speed of light is the same in all directions (even if it doesn't directly measure the one-way speed of light).

a reply to: Arbitrageur

Im not sure but if he was talking about Mössbauer rotor experiments. That wouldnt prove light is the same speed what it does is prove frame dragging or an absolute reference frame. We would run in to the problem in order to make the measurement you have to assume the speed of light is the same In fact they set c=1 in the paper. You cant test for an answer that is assumed in the paper to be true.

originally posted by: ArbitrageurAccording to Hawking's black hole radiation model (which hasn't been experimentally verified either), the micro black hole would evaporate almost instantly, which is widely thought to be probably true despite the lack of experimental verification

Well, there's (unverified) theory, and there's (verified) practice. Not that I've ever seen a micro black hole myself, but LHC was initially intended to act as a micro black hole factory, so at least some people believed that they wouldn't evaporate almost instantly... as they shouldn't if energy density in their close proximity is high enough to feed them until they grow to be stable enough. If they're also charged, and you manage to catch one in a magnetic trap, you could even feed it directly (with a laser, for example), and then use it as a gyroscope-of-sorts (as explained in the previous post).

originally posted by: ArbitrageurIf you watched the Veritasium video, that's the kind of thing Derek says you can't do because if space time is different in different directions that may not be a valid assumption. In fact it's definitely not true where spacetime is different in different directions, like if you move one clock down and the other clock up in a lab on Earth at the same speed, those are opposite directions, but the clocks will not remain synchronized.

I see where confusion is stemming from. I mentioned Earth, but I never meant for that to be understood as Earth's-gravitational-field frame of reference. I simply meant Earth (location of the experimental equipment) as a reference "point". Earth's own (rotational, seemingly-circular, but really highly complex, pseudo-spiral-like) absolute movement in space, as well as Earth's gravitational field itself, will certainly add some error to the measurement, but as long as those errors are smaller than the error introduced by the measuring equipment itself, they should be safe to ignore (another problematic assumption, I guess).

My point is simply to emphasize the fact that, if you want to measure the speed of light in just one direction, you really need some way to find out the attributes (direction, primarily) of the equipment's absolute movement in space, which runs completely contrary to Relativity which says that there's no such thing as absolute movement in space, because there is (according to Relativity) no absolute frame of reference to determine such movement.

I'm not a physicist, so my understanding of Relativity is very limited, but I'm pretty certain that I got that part right.

I also see that what you're asking for is a general validation of the speed of light in a general universe where that speed may not be the same in all directions (or in all points in space or at all times, being the most general of all generalizations). What I proposed was really a special case validation of the speed of light in the special case universe (this one) in different directions, so you're right, my solution wouldn't work in any other universe (if that's what's troubling you).

Also, the reason why I assume that clocks would remain synchronized if moved only within a plane of (already aligned with its absolute direction of movement) black hole's rotation (and moved at the same speed relative to the black hole's axis of rotation, speeds being measured locally, in the clocks' local frames of reference) is because that should be the case in this special case (holographic) universe. I was really taking a shortcut there (or, rather, I was doing it in reverse) to "prove" something that I already assumed to be true, so yes, it's all circular reasoning in the end, but the point is to experimentally verify if it's true at all, so circular reasoning or not, if it can be verified experimentally, it doesn't matter how exactly I came up with it.

...

All of this thinking has actually led me to another possible (theoretical) solution to your problem. It would be one that would not involve any black holes at all, but also one which could not give you exact speed of light in different directions, only a definite proof that C is either the same in all direction, or that it isn't.

This solution would involve some way to trap a pulse of light into a circular path, and then measure pulse's position after specific (precise) interval of time has passed. Make a 12h delay (for Earth's spin to send you traveling in the not-quite-opposite direction), and then repeat the experiment. Is the difference in results greater than the anticipated error (due to all the gravitational and equipment effects)?

Interestingly enough, there may actually be a way to trap a pulse of light in such a way.

Photons pair up like superconducting electrons
www.nature.com...

And with that, I'm now officially out of ideas.

originally posted by: blackcrowe
Richard Feynman. How did we find the speed of light.

Einstein is not mentioned, neither is measuring light in 2 directions or bouncing off a mirror.

Feynman is right, that measurement of the speed of light using Jupiter's moons was made by Olaus Roemer in 1676, but the speed he came up with was what we would today call 214,000 km/s, which is somewhat in the right ballpark, but not that close to our definition of the speed of light as 299,792 km/s. Moreover an analysis by Zhang showed this method is actually using Jupiter as a slow moving clock, thus it's not really a one-way speed of light measurement.

One-way speed of light

The first experimental determination of the speed of light was made by Ole Christensen Rømer. It may seem that this experiment measures the time for light to traverse part of the Earth's orbit and thus determines its one-way speed, however, this experiment was carefully re-analysed by Zhang, who showed that the measurement does not measure the speed independently of a clock synchronization scheme but actually used the Jupiter system as a slowly-transported clock to measure the light transit times.[32]

The Australian physicist Karlov also showed that Rømer actually measured the speed of light by implicitly making the assumption of the equality of the speeds of light back and forth.

originally posted by: dragonridr
a reply to: Arbitrageur

Im not sure but if he was talking about Mössbauer rotor experiments. That wouldnt prove light is the same speed what it does is prove frame dragging or an absolute reference frame. We would run in to the problem in order to make the measurement you have to assume the speed of light is the same In fact they set c=1 in the paper. You cant test for an answer that is assumed in the paper to be true.

You say "they set c=1 in the paper", but you don't say what paper. Mössbauer rotor experiments is plural, so there are numerous papers, one for each variation of the experiment.

I wasn't that familiar with all of the variations in the experiments, but I found a paper "The Doppler Effect and the Anisotropy of the Speed of Light" by Drągowski and Włodarczyk (Foundations of Physics (2020) 50:429–440) who mention the Mössbauer rotor experiments. I bolded the part that seems relevant to this thread though I included the related passages for context.

The transverse Doppler effect has been extensively investigated in a class of so-called Mössbauer rotor experiments. Resonance absorption of radiation by atomic nuclei was measured in a setup consisting of a source and absorber placed on a rotating disk. In most of the experiments the change in orientation of the experimental setup was not accounted for, thus only the average Doppler shift was measured and obviously no directional anisotropy could be detected. There were also a few such experiments [14–16], that investigated directional dependence of the effect.

It has been shown in the previous section that the null result of experiments investigating the Doppler effect does not exclude the anisotropy of the speed of light, since the formulas describing the energy change calculated with the absolute and Einstein synchronization are identical, even though the one-way velocities of light are not. As expected, no anisotropy was observed within the accuracy of the measurement in direction sensitive Mössbauer rotor experiments.

So a particular class of those experiments did test for anisotropy in various directions, and while it did have a null result, that null result is not conclusive in confirming the isotropy of the speed of light for the reason explained.

So moebius, if you were thinking of a variation of the experiment not mentioned here or have a link to support your statement on page one, feel free to post it. The way I interpret this interpretation is that maybe we could say if relativity is correct, then the Mössbauer rotor experiments do prove what you say they prove, and of course relativity is widely thought to be at least largely correct, but we don't want to assume that for this experiment.

originally posted by: clusterfok
Well, there's (unverified) theory, and there's (verified) practice. Not that I've ever seen a micro black hole myself, but LHC was initially intended to act as a micro black hole factory

That was considered a possible outcome.

so at least some people believed that they wouldn't evaporate almost instantly...

They did expect the black holes to evaporate almost instantly, an "evaporation signature" as described below is what they were looking for. To my knowledge they never observed such a signature.

Search for microscopic black hole signatures at the Large Hadron Collider

Microscopic black holes are predicted to exist in some theoretical models that attempt to unify General Relativity and Quantum Mechanics by postulating the existence of extra "curled-up" dimensions, in addition to the three familiar spatial dimensions. At the high energies of the Large Hadron Collider, such theories predict that particles may collide "closely enough" to be sensitive to these postulated extra dimensions. In such a case, the colliding particles could interact gravitationally with strengths similar to those of the other three fundamental forces – the Electromagnetic, Weak and Strong interactions. The two colliding particles might then form a microscopic black hole.

If it were so produced, a microscopic black hole would evaporate immediately, producing a distinctive spray of sub-atomic particles of normal matter. These would then be observed in the high-precision CMS detector that surrounds the LHC collision point. CMS has searched for such events amongst all the proton-proton collisions recorded during the 2010 LHC running at 7 TeV centre-of-mass energy (3.5 TeV per proton beam).

No experimental evidence for microscopic black holes has been found.

I see where confusion is stemming from. I mentioned Earth, but I never meant for that to be understood as Earth's-gravitational-field frame of reference.

Yet still, you're talking about the LHC, an accelerator on earth, which doesn't make for a consistent argument that you're not talking about "on Earth" or the LHC is a bit underground I suppose but that's partly because real estate is too valuable to put it on the surface.

I was really taking a shortcut there (or, rather, I was doing it in reverse) to "prove" something that I already assumed to be true

Right, well to measure the one-way speed of light without building assumptions into the measurement is the problem, and every solution considered so far has assumptions built into the experiment. The assumptions people are considering may be both reasonable, and true, but the unsolved problem is to figure out how to make the measurement without making such assumptions.

This solution would involve some way to trap a pulse of light into a circular path, and then measure pulse's position after specific (precise) interval of time has passed. Make a 12h delay (for Earth's spin to send you traveling in the not-quite-opposite direction), and then repeat the experiment. Is the difference in results greater than the anticipated error (due to all the gravitational and equipment effects)?

No, the circular path idea I thought was discussed and excluded in the Veritasium video. It's a slight variation on the mirror idea in that both methods will mask the anisotropy of the speed of light and make it seem isotropic even if it's not.