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Why No One Has Measured The Speed Of Light

qubit

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Fascinating. I never knew this was a problem until I saw this video. It's from a reputable channel, too.



UPDATE
For another perspective, here's another source explaining why the speed can never be measured.



ANOTHER UPDATE

Three animations which give a good feel for the speed of light.

 
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Kinda clickbaity, It's not a "problem" ? Better sources to learn GR and SR. Otoh, if it can get anyone interested in science, +1 from me
 
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I blow my load faster than that, cmon.
 

qubit

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Kinda clickbaity, It's not a "problem" ? Better sources to learn GR and SR. Otoh, if it can get anyone interested in science, +1 from me
There's no clickbait. It's exactly a problem, because it's not possible to do away with the assumption of the speed of light, regardless of how you try to measure it and that's what makes the video interesting. This video isn't intended to teach all about SR & GR, just how it relates to measuring the speed of light. And yes, the presentation makes a big difference to user engagement. :) This channel is pretty good at that.
 
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Yes! Veritasium is a great channel, very informative topics. Been following it for a while now, always happy to see a new video in my sub box. That video did get my old noggin' churning when I watched it when it first came out. Very interesting topic that you just wouldn't ever think about.
And yeah, I disagree with Wizzard. It is a problem, not one that's paramount to our daily lives but neither are most scientific problems. A scientific problem is simply something we just don't understand, it doesn't have to change our lives by finding the solution.
 

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I can accept that the speed of light is impossible to measure to an exact amount. However, the presenter established another narrative which is that we can't be sure it doesn't travel at two different speeds. The initial premise for that is based on physical science, where light will travel at speeds other than C. I guess a black holes gravitational well is evidence of that. However, in much of the YT vid, he talks about a communication from Earth to Mars. That's a path through 'standard' space in a stable planetary model where gravity and such is held in balance. All the host ends up doing, IMO, is to look like a conceited ass with the instantaneous speed concept. My problem with his problem is that he provides no sound science for the general assumption he makes that light speed could be 1/2 C and instantaneous in a round trip. That's where this video fails hardest. It's not science to postulate a random thought, it's pseudo-science. He's taking Einsteins theory which accepts C isn't truly constant and adds an arbitrary value.

It's that sort of extrapolation of scientific data, specifically twisting the scientific theory, to create a novel problem or hypothesis which whack-jobs use to befuddle others. Because, thing is, it takes a clever misapplication of science to create pseudo-science.

Now, I'm not saying this guy is doing that across his channel but what was presented in the vid is pretty much 95% science to create a convincing foundation for his entirely unscientific postulation. He could have left out his BS and kept it very interesting by focussing on the difficult issues of measuring light speed through different mediums.
 

qubit

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@the54thvoid It's a tricky one, but going by the measurement with a mirror example, he's right that the value we arrive at is an average value of both trips, so he took it to the limit of instantaneous one way and double speed the other for it to give the same result. Thinking about it, one could also say that light speed varies in the one direction too, a but like wow and flutter on a cassette for an analogy, so how do we prove that it doesn't happen?

The problem of course, is that there's nothing faster than light to compare with.

Also, Einstein did say that the speed of light in a vacuum is a constant. All that changes is blueshift or redshift depending on gravity and whether one is going fast or slow. Why do you think otherwise?
 

the54thvoid

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@the54thvoid It's a tricky one, but going by the measurement with a mirror example, he's right that the value we arrive at is an average value of both trips, so he took it to the limit of instantaneous one way and double speed the other for it to give the same result. Thinking about it, one could also say that light speed varies in the one direction too, a but like wow and flutter on a cassette for an analogy, so how do we prove that it doesn't happen?

The problem of course, is that there's nothing faster than light to compare with.

Also, Einstein did say that the speed of light in a vacuum is a constant. All that changes is blueshift or redshift depending on gravity and whether one is going fast or slow. Why do you think otherwise?
From the vid, he shows the actual equation to illustrate it uses the average of a round trip. From this he makes the arbitrary statement, what if it's 'instantaneous'. Technically, and strangely, this phenomenon was used in a Star Trek TNG episose when Wesley becomes the 'traveller'(?). If anything can move at an instantaneous speed, it can exist everywhere at once. Which, under quantum physics is impossible, no? I'm sure I've watched this described in such a way that two electrons cannot inhabit the same specific energy space, which is linked to spooky entanglement. You change the property of an entangled photon and it's counterpart, no matter how far away must also change it's behaviour.

Actually... entanglement supports instantaneous speed of interaction, if not travel.

I'm waving the white flag, I work in a freaking gym, man. Gonna do me some reps to get me some biggness.
 

qubit

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@the54thvoid It's that last sentence that you've got the laughing emoji for - you've cracked me up! :D

To be honest, the video confuses me a bit, but I trust he's making sense due to his reputation. Just don't tell anyone I got mixed up, ok? Oh... :eek:
 
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I'm waving the white flag, I work in a freaking gym, man. Gonna do me some reps to get me some biggness.

The amount of "bro" that ancient philosophers had makes me think that the hang-out spot for philosophers (like Socrates, Arostotile, etc. etc.) was a glorified gym. Seriously.

“No man has the right to be an amateur in the matter of physical training. It is a shame for a man to grow old without seeing the beauty and strength of which his body is capable.”

All that thinking had to come from somewhere, and its evident that maybe Socrates was doing that "thinking" in between reps. Lol.
 
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If it has no physical consequences (the reason it can't be measured) then it is irrelevant (has no effects); so one is free to define it to be direction independent.
 
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The amount of "bro" that ancient philosophers had makes me think that the hang-out spot for philosophers (like Socrates, Arostotile, etc. etc.) was a glorified gym. Seriously.



All that thinking had to come from somewhere, and its evident that maybe Socrates was doing that "thinking" in between reps. Lol.
People dont give thier bodies enough credit for the thoughts in thier heads, sometimes. If I had a nickle for every "unsolvable" issue that dissappeared when I became more active...
 

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If it has no physical consequences (the reason it can't be measured) then it is irrelevant (has no effects); so one is free to define it to be direction independent.
Thing is, this is science, another word for the pursuit of the deepest understanding of reality possible, so it matters in that sense. And who knows, it might even matter in some real life sense that we just don't know about yet.
 
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Thing is, this is science, another word for the pursuit of the deepest understanding of reality possible, so it matters in that sense. And who knows, it might even matter in some real life sense that we just don't know about yet.
I agree, although I think much of the unknow should remain just that, unknow, and unsolvable since Man tends to exploit it for it's destructive powers instead of what it can do for the greater good. Deep thought over....
 

qubit

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I agree, although I think much of the unknow should remain just that, unknow, and unsolvable since Man tends to exploit it for it's destructive powers instead of what it can do for the greater good. Deep thought over....
Well, there's an argument for misuse there, I'll give you that. Unfortunately, we can't discuss that here.
 
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People dont give thier bodies enough credit for the thoughts in thier heads, sometimes. If I had a nickle for every "unsolvable" issue that dissappeared when I became more active...


I mean, its weird, but true. There's something about fitness that helps in purely mental tasks (like playing video games at a professional level). That's why eSports players hit the gym.

“I had never been to a gym prior to joining this team,” Gallagher says. “I did some physical activities in high school, but nothing super specific. When I joined [the Philadelphia Fusion*], I talked to Tucker [Roberts], who is the owner, and was like, ‘I want a personal trainer for the team. Even if it’s only me using it, I want a gym and a personal trainer. I think that will be really beneficial for me as a player.’”

They’re still in the process of getting that set up, but Elk says that “using online advice,” he has already begun to take advantage of the gym they have at the team house. “Fusion* supplied us with a cable machine, lots of dumbbells, a bench press, deadlifts … a lot of really basic equipment, which has been nice.”

Stretching is also hugely important as a means to avoid wrist, neck, and shoulder injuries that are so often the result of prolonged sessions sitting at the computer.

“In order to avoid any issues with wrist, shoulder, or back pain, I like to take precautions by practicing some simple stretches we learned at the 76ers* Training Complex with the team's sports science staff,” Noquez says. “These stretches are great because you don't need any special equipment and you don't need a lot of space. I can do these stretches right at my desk, in-between scrims, or even in-between rounds if I needed to.”

Gotta stay fit if you want to remain an elite video gamer. I dunno what this has to do with the speed of light though, lol. I'll try to be more on topic now :cool:
 

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The "Speed of Light " is a bit of a misnomer..............
I would say it does vary depending on the light Frequency
Infra red light thru to ultraviolet covers a wide spectrum we can see but light also exists at frequencys both far below and way above
So comes the Question
Which light Speed are you measuring. :)
 
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It is well known that the speed does not depend on the energy (for light), strange as that might seem.

EVEN stranger, even if one is passing a beam of light, one will still measure the same speed, even if going at say 99% the speed of light. Ridiculous? Absolutely; but true never-the-less.


Actually, there are many equations involving c; take Maxwell's equations for example. One would notice if c was direction dependent.
 
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It is well known that the speed does not depend on the energy (for light), strange as that might seem.

EVEN stranger, even if one is passing a beam of light, one will still measure the same speed, even if going at say 99% the speed of light. Ridiculous? Absolutely; but true never-the-less.


Actually, there are many equations involving c; take Maxwell's equations for example. One would notice if c was direction dependent.

Note: "The Speed of Light" changes. Light in a vacuum is faster than light in fiber optics. When physicists talk about "The Speed of Light", they're using shorthand for "The Speed of Causality" (which light in a vacuum, or "c", happens to match).

"Causality", that is, how quickly the rest of the world "reacts" to changes, propagates at a fundamentally constant velocity. In fact, the big surprise is that there's a "speed of causality" at all, and that there are physics experiments that prove it has a speed (and that its a constant).
 
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How true, and as a result electrons can go faster than the speed of light (in a material) and the shock wave is Cherenkov radiation.
 
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I have to assume the speed they are "Looking For" is based on how fast it travels naturally from a star to a planet through space.
It's true the speed of light does change depending on conditions.....
And I seem to recall from years ago it was proven magnetism can actually move faster than light itself can.

It has been proven as fact in the case of black holes, lines of magnetic force do emanate from a black hole and that means it's coming up from the hole through it's event horizon.
So if you must go faster than light itself to make it up and out of the event horizon, well - There you go.

I don't believe it's possible to nail it down to an exact speed but we can get close.
For example it's been said a radio transmission travels at the speed of light. It takes a radio transmisison about 4 seconds to travel from Earth to the moon and you can get an approximate speed based on the distance it must travel during those 4 seconds but also, there is no actual way to 100% measure this distance accurately at any time either. As the moon orbits, it either gets closer or further away as it orbits, that also being relative to the transmission point of the signal on Earth to the receiving point on the moon.
 

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The "Speed of Light " is a bit of a misnomer..............
I would say it does vary depending on the light Frequency
Infra red light thru to ultraviolet covers a wide spectrum we can see but light also exists at frequencys both far below and way above
So comes the Question
Which light Speed are you measuring. :)
That's a misconception. Light travels at the same speed regardless of its frequency. It doesn't change with intensity, either.


How true, and as a result electrons can go faster than the speed of light (in a material) and the shock wave is Cherenkov radiation.
Yup, Cherenkov radiation is effectively a sonic boom. How cool is that?! Read all about it, here:


I have to assume the speed they are "Looking For" is based on how fast it travels naturally from a star to a planet through space.
It's true the speed of light does change depending on conditions.....
And I seem to recall from years ago it was proven magnetism can actually move faster than light itself can.

It has been proven as fact in the case of black holes, lines of magnetic force do emanate from a black hole and that means it's coming up from the hole through it's event horizon.
So if you must go faster than light itself to make it up and out of the event horizon, well - There you go.

I don't believe it's possible to nail it down to an exact speed but we can get close.
For example it's been said a radio transmission travels at the speed of light. It takes a radio transmisison about 4 seconds to travel from Earth to the moon and you can get an approximate speed based on the distance it must travel during those 4 seconds but also, there is no actual way to 100% measure this distance accurately at any time either. As the moon orbits, it either gets closer or further away as it orbits, that also being relative to the transmission point of the signal on Earth to the receiving point on the moon.
It's about 1.3 seconds to get to the moon, quite a bit faster.
 
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How true, and as a result electrons can go faster than the speed of light (in a material) and the shock wave is Cherenkov radiation.

In a medium is the key part here.

By current knowledge speed of light in vacuum is considered invariant and unreachable in practice by any matter (with increasing energy input one can get arbitrarily close).
 
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