Light speed is not constant or accurate

[Eric Ward]

That is not true. Time dilation is not directly observable. Your 'blink time' would be subject to the Doppler effect between labs that are in relative motion.

I've hear physicist say that if a rocket ship was shot into a black hole it would appear to slow down because of gravitational time dilation. I miss spoke about the particle observing a slower reality. It would experience

I'm not sure what you mean by the "correct" light speed, but if you mean something like you said before, along the lines of "the speed we would measure if the Earth's gravitational field were not there", this is a meaningless concept, for reasons I explained in a previous post.

You are correct. I accept this now and have a clearer understanding of SR surrounding time dilation. Thank you. E

 

[Mentz114]

I've hear physicist say that if a rocket ship was shot into a black hole it would appear to slow down because of gravitational time dilation. I miss spoke about the particle observing a slower reality. It would experience...

The problem here is that you are trying to run when you can't even crawl. GR is extremely difficult to understand and the mathematics is daunting. SR is, actually, a much simpler idea with surprisingly simple mathematics! That is what you need to learn and understand FIRST! Diving into GR like this is like teaching a toddler how to climb a tree when he hasn't even learned how to stand up straight! - ZapperZ

 

[Eric Ward]

The problem here is that you are trying to run when you can't even crawl. GR is extremely difficult to understand and the mathematics is daunting. SR is, actually, a much simpler idea with surprisingly simple mathematics! That is what you need to learn and understand FIRST! Diving into GR like this is like teaching a toddler how to climb a tree when he hasn't even learned how to stand up straight! - ZapperZ

Thank you. I didn't intend for that to post. It was incomplete. Zapper hit the nail on the head. E

 

[Dale]

Just as an aside. The meter used to be defined by a couple of marks on a metal bar. (Skipping a few steps) then we tried to measure the speed of light and found it to be so constant that most of the inaccuracy in the speed of light was due to inaccuracy in the meter. Now we can get incredibly precise and reproducible measures of the meter by defining the speed of light to gave a fixed constant.

 

[doaaron]

Regarding the whole point about the speed of light being constant, these scientist think that they have managed to slow down the speed of light.

http://www.bbc.com/news/uk-scotland-glasgow-west-30944584

Forgetting about whether their experimental setup was correct or not, I wonder what the experts think would be the implications wrt SR GR etc.Aaron

 

[Ibix]

Regarding the whole point about the speed of light being constant, these scientist think that they have managed to slow down the speed of light.

This has been discussed here a couple of times. The researchers managed to construct a single photon in a non-plane wave state. This travels slower than a plane wave photon. It is the speed of plane waves that is invariant.

From a relativistic perspective this experiment means nothing.

 

[Eric Ward]

Regarding the whole point about the speed of light being constant, these scientist think that they have managed to slow down the speed of light.

http://www.bbc.com/news/uk-scotland-glasgow-west-30944584

Forgetting about whether their experimental setup was correct or not, I wonder what the experts think would be the implications wrt SR GR etc.Aaron

That's very interesting. I'll have to look up the paper they published. I would personally like to see the experiment duplicated again and see the math but you it looks at face value like they have some result. Now to see how valid it is and of course if they were accurate in their experiment. I'm curious what laws they based their math on before the experiment or if they are trying to challenge one. I will be back after reading their paper.

 

[Mentz114]

Regarding the whole point about the speed of light being constant, these scientist think that they have managed to slow down the speed of light.

http://www.bbc.com/news/uk-scotland-glasgow-west-30944584

Forgetting about whether their experimental setup was correct or not, I wonder what the experts think would be the implications wrt SR GR etc.Aaron

The speed of light in a vacuum is the invariant. Light traveling through matter is not the same thing and could probably be made to take years.

 

[doaaron]

The speed of light in a vacuum is the invariant. Light traveling through matter is not the same thing and could probably be made to take years.

I think you need to re-read the article.Aaron

 

[Eric Ward]

The speed of light in a vacuum is the invariant. Light traveling through matter is not the same thing and could probably be made to take years.

You're right Mentz114 however, these scientist are slowing the light down after it leaves there electronic liquid crystal. Normally if light travels through, let's say, a clear glass of water. It slows down as its passing through but once it leaves it speeds back up to the normal speed of light. What this group has accomplished in experiment is slowing light down after it has left the said matter. Truly a fantastic discovery but does not change any principles in GR. They claimed to have simply changed the shape of the photon. Doaaron said it best above. "They have constructed a single photon in a non-plane wave state. This travels slower than a plane wave photon. It is the speed of plane waves that is invariant.

From a relativistic perspective this experiment means nothing." Doaaron.

Very well said Doaaron..

 

[doaaron]

Doaaron said it best above. "They have constructed a single photon in a non-plane wave state. This travels slower than a plane wave photon. It is the speed of plane waves that is invariant. From a relativistic perspective this experiment means nothing." Doaaron. Very well said Doaaron..

Wohoo free credit :D

seriously though, that wasn't me :P

Aaron

 

[Eric Ward]

Wohoo free credit :D

seriously though, that wasn't me :P

Aaron

You right, I feel TERRIBLE. My mistake. That was "Ibix".

 

[doaaron]

You right, I feel TERRIBLE. My mistake. That was "Ibix".

happens to us all at some point...

 

[Eric Ward]

You're right Mentz114 however, these scientist are slowing the light down after it leaves there electronic liquid crystal. Normally if light travels through, let's say, a clear glass of water. It slows down as its passing through but once it leaves it speeds back up to the normal speed of light. What this group has accomplished in experiment is slowing light down after it has left the said matter. Truly a fantastic discovery but does not change any principles in GR. They claimed to have simply changed the shape of the photon. Doaaron said it best above. "They have constructed a single photon in a non-plane wave state. This travels slower than a plane wave photon. It is the speed of plane waves that is invariant.

From a relativistic perspective this experiment means nothing." Doaaron.

Very well said Doaaron..

My apologies that "quote" was from Ibix.

Instead of writing all of that. I should have just said "re-read it" too..

 

[Mentz114]

You're right Mentz114 however, these scientist are slowing the light down after it leaves there electronic liquid crystal. Normally if light travels through, let's say, a clear glass of water. It slows down as its passing through but once it leaves it speeds back up to the normal speed of light. What this group has accomplished in experiment is slowing light down after it has left the said matter. Truly a fantastic discovery but does not change any principles in GR. They claimed to have simply changed the shape of the photon. Doaaron said it best above. "They have constructed a single photon in a non-plane wave state. This travels slower than a plane wave photon. It is the speed of plane waves that is invariant.

"From a relativistic perspective this experiment means nothing." Doaaron.

Very well said Doaaron..

It sounds as if they have photon state that is like a wave packet. The difference between group and phase velocity is a well known phenomenon. Nice experiment.

Yes, no conflict with relativity.

 

[Ibix]

My apologies that "quote" was from Ibix.

I'll let you off. This time...

 

[Kishan Kumar]

The speed of light is equal to reciprocal of sq.root of permitivity times permeability, as derived by Maxwell which concludes that speed of light remains the same whatever be the frame of reference. And the thing you talking about time dilation, length contraction(look it up) and gravitational time dilation, these all came due to the fact that light has a constant speed(c=299,792,458 m/s).

 

[Jamini Bhusan]

You guys are great btw! Thank you for all of your awesome answers. I'm a huge science geek. I started with astronomy and meteorology in my 20s and moved to studying physics 3 years ago. I wish I could go to school and be full time. It would be just be irresponsible to go back to school with a wife and kids. So I'm stuck in my current career . But just know you guys are my heros!

Dear Eric, each of us are on a journey from conception to death & there is not much point in looking back. One need not have a degree or doctorate in physics to raise questions; in fact, those who go to regular University become mechanical, they must agree with what they read in books, agree with couple of hundred pages of writings to secure their degree & livelihood. If questions are not raised then things would become absolute; modern scientists are now raising questions like you have. "A fundamental law of physics, indeed of all science, is causality: that cause always precedes effect. This was accepted in classical physics, and the special theory of relativity took pains to preserve the rule, despite the relativity of an object's motion." I am sure you know about work done by physicist Masatoshi Koshiba. http://www.livescience.com/29111-speed-of-light-not-constant.html

 

[Ophiolite]

[Mentor's note - edited to remove a statement based on an unsupported assumption]

in fact, those who go to regular University become mechanical, they must agree with what they read in books, agree with couple of hundred pages of writings to secure their degree & livelihood

While learning the fundamentals is an integral part of undergraduate training, questioning why those are considered fundamental and exploring the evidence is an essential element in quality tertiary education.

 

[ZapperZ]

Dear Eric, each of us are on a journey from conception to death & there is not much point in looking back. One need not have a degree or doctorate in physics to raise questions; in fact, those who go to regular University become mechanical, they must agree with what they read in books, agree with couple of hundred pages of writings to secure their degree & livelihood. If questions are not raised then things would become absolute; modern scientists are now raising questions like you have. "A fundamental law of physics, indeed of all science, is causality: that cause always precedes effect. This was accepted in classical physics, and the special theory of relativity took pains to preserve the rule, despite the relativity of an object's motion." I am sure you know about work done by physicist Masatoshi Koshiba. http://www.livescience.com/29111-speed-of-light-not-constant.html

This is a very annoying comment, and it repeats the often-spewed garbage that crackpots try to use against scientists, that we are nothing more than a bunch of people who simply toe the party line. This is not only silly, but also ignores the most obvious evidence out there, which is that advances in science and our knowledge ARE being made by these people. If we only become "mechanical", we won't be making such advances.

Here's the thing: to be able to go outside of the "box", you must, first and foremost, know WHERE the box is, and where the boundaries are! Otherwise, you won't know if something is new even if it comes up and bites you on your rear end! We teach kids about the known and verified science so that they will be able to recognize when something truly new comes up! Otherwise, you'll end up claiming about something to be new when all it is is simply a reflection of your ignorance of what is already known!

Secondly, in the hands of someone who doesn't understand physics and doesn't keep up with all the latest results, that livescience article will result in exactly this: someone claiming that light can have a varying speed. Now, consider the fact that this possibility is actually irrelevant in this case, because the topic of this thread is NOT about light varying in speed over the evolution of our universe (which is still highly controversial, by the way). The OP's point in the first thread, and the discussion throughout the thread, is not related to this point. So already this is highly off-topic. But more importantly, the issue of speed of light varying over time has not had a lot of experimental support. In fact, there have been many that points to the contrary. See, for example, http://physicsworld.com/cws/article/news/2008/mar/10/new-optical-clock-promises-increased-accuracy, where this has a greater accuracy than previous measurement of the fine-structure constant.

Moral of the story here is that you simply cannot "imagine" all these things without first understanding the fundamental knowledge, and then being aware of the state of knowledge that we currently have, right now. That is why we have citation indexes, so that you can check if new work related to old ones have been published. Otherwise, you'll end up quoting something like this and misleading yourself into thinking that this is still something that it widely accepted.

Zz.

 

[Nugatory]

ZapperZ has said pretty much everything there is to say in the current state of this thread. It is now closed.