Is the speed of light a constant? Or can it vary? If so, in what kinds of situations, or how much?

[Neogaia777]

Is the speed of light truly a constant? Or can it vary? If so, in what kind of situations, or how much can it vary?

I'm asking for someone in another thread, told him I would bring it here and ask some honest questions about it here.

He posted this article: https://www.universetoday.com/14955...ure-the-speed-of-light-in-a-single-direction/

He claims the speed of light can vary with direction basically, can only be measured when being reflected off a surface, or in two directions/ways, and that we can't actually measure or determine it, and other things like that, etc.

I always believed that it was/is a constant, but are the situations where it can vary?

And if so, what are they, and how much?

Now he also believes that the earth is not very old, 6 to 12 thousand years or something like that, and he is using this article to support some of his claims, etc.

And since I'm not an expert, I told him I would bring those questions here, etc.

I argued that it was a constant, but then I googled it and found out that may not always be true, etc.

Anyway, can you guys pick this apart and sort this out for me please, etc?

But in maybe layman's terms preferably, etc.

Either way, I told him that what I found out or what I got from you guys on here was probably not even going to get anywhere close to supporting his claims, but I told him that I would link it for him in the other thread, etc.

Thanks in advance.

Take Care/God Bless.

 

[AlexB23]

Is the speed of light truly a constant? Or can it vary? If so, in what kind of situations, or how much can it vary?

I'm asking for someone in another thread, told him I would bring it here and ask some honest questions about it here.

He posted this article: The One-Way Speed of Light | Spaceaustralia.

He claims the speed of light can vary with direction basically, can only be measured when being reflected off a surface, or in two directions/ways, and that we can't actually measure or determine it, and other things like that, etc.

I always believed that it was/is a constant, but are the situations where it can vary?

And if so, what are they, and how much?

Now he also believes that the earth is not very old, 6 to 12 thousand years or something like that, and he is using this article to support some of his claims, etc.

And since I'm not an expert, I told him I would bring those questions here, etc.

I argued that it was a constant, but then I googled it and found out that may not always be true, etc.

Anyway, can you guys pick this apart and sort this out for me please, etc?

But in maybe layman's terms preferably, etc.

Either way, I told him that what I found out or what I got from you guys on here was probably not even going to get anywhere close to supporting his claims, but I told him that I would link it for him in the other thread, etc.

Thanks in advance.

Take Care/God Bless.

The speed of light is constant, at 299,792.458 km/s in a perfect vacuum. In air, light travels at 299,700 km/s, while in water, it goes at 224,900 km/s. Light's speed varies depending on what material it travels through, as atoms can impede the travel of photons. Scientists have developed materials to slow light down to nearly a stop, and also have reshaped light particles to make photons travel 0.001% slower compared to a regular photon. One can not argue with Young Earth Creationists. Trust me, I am an Old Earth Creationist, and have tried a few times.

Sources:

speed of light in vacuum - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

speed of light in air - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

speed of light in water - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

How to slow down light until it stops

In vacuum, light always travels at a constant speed of 299,792,458 metres per second. Nothing can travel faster than this constant c, as denoted by physicists. These two postulates are basic building blocks of modern physics and were first announced more than a hundred years ago by Albert...

www.zmescience.com

 

[Neogaia777]

Is the speed of light truly a constant? Or can it vary? If so, in what kind of situations, or how much can it vary?

I'm asking for someone in another thread, told him I would bring it here and ask some honest questions about it here.

He posted this article: There's no way to Measure the Speed of Light in a Single Direction

He claims the speed of light can vary with direction basically, can only be measured when being reflected off a surface, or in two directions/ways, and that we can't actually measure or determine it, and other things like that, etc.

I always believed that it was/is a constant, but are the situations where it can vary?

And if so, what are they, and how much?

Now he also believes that the earth is not very old, 6 to 12 thousand years or something like that, and he is using this article to support some of his claims, etc.

And since I'm not an expert, I told him I would bring those questions here, etc.

I argued that it was a constant, but then I googled it and found out that may not always be true, etc.

Anyway, can you guys pick this apart and sort this out for me please, etc?

But in maybe layman's terms preferably, etc.

Either way, I told him that what I found out or what I got from you guys on here was probably not even going to get anywhere close to supporting his claims, but I told him that I would link it for him in the other thread, etc.

Thanks in advance.

Take Care/God Bless.

The article link doesn't seem to be working at the moment, but this is one of the things that it says in it that I found laughable, but I could be wrong maybe?

"The speed of light coming towards us is at ten times more speed/faster than the light moving away from us", etc.

What do you think?

Update: Article link seems to be working now.

 

[Neogaia777]

The speed of light is constant, at 299,792.458 km/s in a perfect vacuum. In air, light travels at 299,700 km/s, while in water, it goes at 224,900 km/s. Light's speed varies depending on what material it travels through, as atoms can impede the travel of photons. Scientists have developed materials to slow light down to nearly a stop, and also have reshaped light particles to make photons travel 0.001% slower compared to a regular photon. One can not argue with Young Earth Creationists. Trust me, I am an Old Earth Creationist, and have tried a few times.

Sources:

speed of light in vacuum - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

speed of light in air - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

speed of light in water - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.

www.wolframalpha.com

How to slow down light until it stops

In vacuum, light always travels at a constant speed of 299,792,458 metres per second. Nothing can travel faster than this constant c, as denoted by physicists. These two postulates are basic building blocks of modern physics and were first announced more than a hundred years ago by Albert...

www.zmescience.com

I think his argument (which I had some difficulty understanding) is that since light cannot be measured in one direction, that light from the distant universe could have been coming at us fast enough so as only to take thousands of years to get here to us, etc.

But since he never specifically said that, I had some difficulty understanding his argument, etc.

He seemed to be stuck on the fact that light cannot be measured in one direction, etc. And we therefore do not know if it is not the same or equal in both directions, etc.

And he also seemed to be implying that we cannot measure it at all maybe, etc?

Anyway, thanks for the information links!

I found out about the different mediums like water or air on Google, but didn't know about the other things.

God Bless.

 

[AlexB23]

I think his argument (which I had some difficulty understanding) is that since light cannot be measured in one direction, that light from the distant universe could have been coming at us fast enough so as only to take thousands of years to get here to us, etc.

But since he never specifically said that, I had some difficulty understanding his argument, etc.

He seemed to be stuck on the fact that light cannot be measured in one direction, etc. And we therefore do not know if it is not the same or equal in both directions, etc.

And he also seemed to be implying that we cannot measure it at all maybe, etc?

Anyway, thanks for the information links!

I found out about the different mediums like water or air on Google, but didn't know about the other things.

God Bless.

You are welcome. I always back up science with links. Yeah, this guy is stuck on something. Remember, we know how long it takes to communicate with distant spacecraft, as radio waves travel at the speed of light.

I can beckon for @sjastro to help as well with even more science, if you need him.

 

[Arcangl86]

So he is right in one sense is that we do not know with absolute certainty the one-way speed of light. We can only measure how long it takes to get somewhere and come back to us, and relativity does some strange things as well. But even though c, as measured, is technically the average speed of light, there is no scientific reason to think that the speed of light is actually different depending on the path it takes, though science also can't disprove that.

 

[Neogaia777]

I can beckon for @sjastro to help as well with even more science, if you need him.

I think I am expecting him to be on here soon.

God Bless.

 

[AlexB23]

I think I'm expecting him to be on here soon.

God Bless.

You are welcome, brother. God bless as well.

It is getting late here, so I am signing off, but I will check this out tomorrow, cos science is my favorite subject.

 

[Neogaia777]

You are welcome, brother. God bless as well.

It is getting late here, so I am signing off, but I will check this out tomorrow, cos science is my favorite subject.

See you later, have a good night.

God Bless

 

[AlexB23]

See you later, have a good night.

God Bless

Thank you, brother in Christ. I'll try to make it to this thread tomorrow.

 

[Neogaia777]

So he is right in one sense is that we do not know with absolute certainty the one-way speed of light. We can only measure how long it takes to get somewhere and come back to us, and relativity does some strange things as well. But even though c, as measured, is technically the average speed of light, there is no scientific reason to think that the speed of light is actually different depending on the path it takes, though science also can't disprove that.

This is a good answer.

So, do you think there is any possibility/scenario where they could be different, especially since we really don't know, or can't prove it?

 

[awstar]

Like many science “truths”, there often multiple allowable answers provided by Einstien's theories, but usually only one of the answers is propagated by scientists, and that one acceptable answer is solely based on scientists’ philosophy — not the science itself.

Here's a very short video and its youTube discription that answers a question about Einstien's view of the speed of light.

Anisotropic Synchrony Convention | Dr. Jason Lisle

Simple explanation of how one-way infinite speed of light refers to the incoming light relative to the observer.

This is intended as a quick answer to a question [...] asked, since one-way infinite speed of light makes sense and explains the distant starlight problem in biblical creation model. The only question is which way is the "one-way". Well, it's the incoming light and it applies to each observer individually, no matter where they are located in the universe and how many observers there are. It is observer dependent.

 

[Neogaia777]

Like many science “truths”, there often multiple allowable answers provided by Einstien's theories, but usually only one of the answers is propagated by scientists, and that one acceptable answer is solely based on scientists’ philosophy — not the science itself.

Here's a very short video and its youTube discription that answers a question about Einstien's view of the speed of light.

Unfortunately, that video really doesn't say or prove anything, etc.

And I like that they say "you can say", etc.

Yeah "you can say" anything you like, like the speed of light is infinite or moves at infinite speed coming at you or "whatever", and is at some other slower speed moving away from you, etc, sure "you can say" that, etc, because anyone can "say anything they like", etc, but the most likely possibility still stands that the speed of light is the same in both directions, etc.

I'm trying to find actual evidence that the speed of light could be different in some cases, not just what someone probably trying to push a young earth or young universe agenda "says", etc.

And am only going to be open to "real evidence of such" and not just what someone "says", or wants to be true in order to push their own agenda, or resolve their own point of view of, probably in this case, their own view or interpretation of the Bible, etc.

And I'm not trying to be insulting either, but this is just a "joke", etc.

People can "say" anything they like, etc.

But I am looking for actual observable or proveable evidence in this case if you want me to buy into the view that they could be as different as what some of the people are saying in this video, etc.

God Bless.

 

[sjastro]

The subject of a one way speed of light has turned up in this forum before from a video by the physicist and science presenter Derek Muller.

The problem is the synchronisation of clocks from the light's source to its final destination. This would ordinarily require sending a signal at an infinite speed so the clocks are instantaneously synchronised.
Since this is impossible scientists have tried to work around this problem without much success so at this stage a one way speed of light is an unfalsifiable idea.
The speed of light based on a two way or round trip is constant and is supported by evidence in the form of interferometer measurements and for this reason we use Einstein's assumption the speed is isotropic.

A problem I found in the link was the reference to the speed of light being 10x faster in one direction compared to the other and length/time dilation needs to be considered.
Length and time dilation involves the Lorentz transformation and if light travels faster than c the equations breakdown as length and time take on imaginary values.
While complex numbers are used in QM they have no place in relativity or cosmology.

Finally a word on the Jason Lisle video, there is zero evidence for the speed of light being infinite in one direction and 0.5c in the other for the reasons given above and is not an observer frame of reference issue.

 

[Neogaia777]

The subject of a one way speed of light has turned up in this forum before from a video by the physicist and science presenter Derek Muller.

The problem is the synchronisation of clocks from the light's source to its final destination. This would ordinarily require sending a signal at an infinite speed so the clocks are instantaneously synchronised.
Since this is impossible scientists have tried to work around this problem without much success so at this stage a one way speed of light is an unfalsifiable idea.
The speed of light based on a two way or round trip is constant and is supported by evidence in the form of interferometer measurements and for this reason we use Einstein's assumption the speed is isotropic.

A problem I found in the link was the reference to the speed of light being 10x faster in one direction compared to the other and length/time dilation needs to be considered.
Length and time dilation involves the Lorentz transformation and if light travels faster than c the equations breakdown as length and time take on imaginary values.
While complex numbers are used in QM they have no place in relativity or cosmology.

Finally a word on the Jason Lisle video, there is zero evidence for the speed of light being infinite in one direction and 0.5c in the other for the reasons given above and is not an observer frame of reference issue.

Thanks for this post man.

Take Care.

 

[AV1611VET]

Is the speed of light truly a constant? Or can it vary?

It is a constant.

Some time ago here, we had a Mensan* that used to post (Wiccan Child).

He was asked that question, and if I remember correctly, he said the speed of light didn't change, but the substance it moves through can cause it to "ping pong" through it; thus making it travel farther, and it only seems to slow up.

* He wasn't actually a Mensan, per se, as he didn't take the test for it.

 

[Neogaia777]

he said the speed of light didn't change, but the substance it moves through can cause it to "ping pong" through it; thus making it travel farther, and it only seems to slow up.

Some of the links @AlexB23 provided in post #2 gets into some of that.

God Bless.

 

[AlexB23]

Some of the links @AlexB23 provided in post #2 gets into some of that.

God Bless.

Yep, in fact, it takes millions of years for light to go from the core of the sun to the surface of the sun, cos of all the atoms in the way. It is similar to a game of pinball. Finally, once the photon reaches the surface of the sun, it takes 8 minutes to get to Earth.

Source:

NASA - Sun-Earth Day - Technology Through Time - #50 Ancient Sunlight

This web site is comprised of a series of educational programs and events that occur throughout the year culminating with a celebration on or near the Spring Equinox. :Code 672.0

sunearthday.nasa.gov

 

[awstar]

I'm trying to find actual evidence that the speed of light could be different in some cases, ...

And am only going to be open to "real evidence of such" and not just what someone "says",

and what evidence do you have thus far that the speed of light is constant in both directions? just asking...

 

[essentialsaltes]

Is the speed of light truly a constant? Or can it vary? If so, in what kind of situations, or how much can it vary?

I'm asking for someone in another thread, told him I would bring it here and ask some honest questions about it here.

He posted this article: There's no way to Measure the Speed of Light in a Single Direction

He claims the speed of light can vary with direction basically, can only be measured when being reflected off a surface, or in two directions/ways, and that we can't actually measure or determine it, and other things like that, etc.

Turns out the question is subtler than I thought. Trying to synchronize two clocks by moving them slowly (so you could do a one way measurement with a clock at each end) appears to be prone to difficulties that turn out to be equivalent to the standard assumption that the path out is the same as the path back in a two way measurement.

Wikipedia provides some additional detail.

I always believed that it was/is a constant, but are the situations where it can vary?

I mean, to dispense with the obvious, when we talk about "the speed of light" as a constant we're talking about the speed of light in vacuum. Light travelling through any medium -- air, water, glass -- is slowed by that medium.

There are some speculative ideas that in the very very very very very very early universe a split second after the Big Bang, the speed of light was faster.

But the speed of light (sure, the two-way speed) doesn't seem to vary for most of the universe's history.

Anyway, if the speed of light is faster to left than to the right, it doesn't seem it would have any particular effect on other measurements.