Speed of light in vacuum slowing down?

[spacelike]

Note: I am familiar with (special) relativity and its implications.

This is just a question about experimental results.

 

 

I remembered hearing many years ago that data was showing that the speed of light in vacuum is getting slower. So, recently I decided to google it and I see a bunch of articles about the same thing. But I know from experience that articles on the internet can have very outdated information or just plain incorrect information sometimes.

 

and the articles make it sound like it's not confirmed yet too, which doesn't make sense to me because isn't measuring the speed of light a relatively easy thing to do?

 

I find it hard to believe that this can still be an open question. The only way I can imagine that we are still unsure is due to the possibility that the change is so small we can't measure it.... But it can't be that because scientists have claimed to measure that it is slowing down, so the amount of change in question is within our ability to measure.

(I mean, the possibility of the change being so small will always exist of course... But either their measurements were wrong or they aren't, repeated experiments should easily reveal this, and it has been at least 5 years since I first heard this, hasn't anyone tried to repeat the experiment?)

 

So what is it? Have those measurements been shown to be faulty? Are the slower measurements within the error margin? Has it been confirmed to be slowing down? Is 5 years not long enough for a repeated experiment to have finalized?

Edited July 31, 2013 by spacelike

[xyzt]

Note: I am familiar with (special) relativity and its implications.

This is just a question about experimental results.

 

 

I remembered hearing many years ago that data was showing that the speed of light in vacuum is getting slower. So, recently I decided to google it and I see a bunch of articles about the same thing. But I know from experience that articles on the internet can have very outdated information or just plain incorrect information sometimes.

 

and the articles make it sound like it's not confirmed yet too, which doesn't make sense to me because isn't measuring the speed of light a relatively easy thing to do?

 

I find it hard to believe that this can still be an open question. The only way I can imagine that we are still unsure is due to the possibility that the change is so small we can't measure it.... But it can't be that because scientists have claimed to measure that it is slowing down, so the amount of change in question is within our ability to measure.

(I mean, the possibility of the change being so small will always exist of course... But either their measurements were wrong or they aren't, repeated experiments should easily reveal this, and it has been at least 5 years since I first heard this, hasn't anyone tried to repeat the experiment?)

 

So what is it? Have those measurements been shown to be faulty? Are the slower measurements within the error margin? Has it been confirmed to be slowing down? Is 5 years not long enough for a repeated experiment to have finalized?

This is Zwicky's theory of "Tired Light". It has been proven incorrect.

[Strange]

There have been some measurements that suggest that the speed of light may have changed. But this is a few parts per million over a period of many billions of years.

 

Obviously, this can't be tested directly by measuring the speed of light. So it has to be done indirectly by measuring things such as the fine structure constant in the past (e.g. looking at distant galaxies). As far as I know, these measurements have not been successfully repeated or confirmed.

 

The other, unrelated, idea is that it is possible to choose a different set of coordinates for describing the expanding universe. If you choose appropriate coordinates then the speed of light changes over time and the universe is infinitely old (and distances shrink .... or something; I don't claim to understand the details). But it is just a different version of the same model that (for most people) is less intuitive.

Edited July 31, 2013 by Strange