Design of new experiment to check relative speed of light

[ghjadhav]

To design new experiment to measure relative speed of light, let us discuss about the possible reasons of failure of Michelson-Morley experiment (not about its accuracy but about its philosophy). While designing new experiment, what cares should be taken?

[robross]

To design new experiment to measure relative speed of light, let us discuss about the possible reasons of failure of Michelson-Morley experiment (not about its accuracy but about its philosophy). While designing new experiment, what cares should be taken?

Hello and welcome to BAUT. I'm sure a friendly moderator will be by soon to welcome you as well.

You should know that this particular forum is not the right place to start discussions about things; it's purely for asking questions and receiving answers to those questions.

However, if I interpret your post as a question about experimental results in measuring the speed of light, I can point out we have many ways of measuring this quite accurately now, and in every case it has produced consistent results.

One simple experiment is the fact that we have reflecting mirrors on the Moon now. We can send up a light beam, and measure the time it takes to be reflected back to us. Since we know the exact distance to the Moon very accurately, we can also accurately measure the round-trip time of the light beam, divide by two, and that gives us the speed of light.

Rob

[mugaliens]

One simple experiment is the fact that we have reflecting mirrors on the Moon now. We can send up a light beam, and measure the time it takes to be reflected back to us. Since we know the exact distance to the Moon very accurately, we can also accurately measure the round-trip time of the light beam, divide by two, and that gives us the speed of light.

Rob

I think you have that backwards, Rob. We know the speed of light very precisely through other experiments, and use that information combined with the round-trip time for the light to return from the lunar reflectors to measure the distance to the Moon, which actually varies a bit throughout it's orbit, from 363,104 km to 405,696 km.

[grav]

To design new experiment to measure relative speed of light, let us discuss about the possible reasons of failure of Michelson-Morley experiment (not about its accuracy but about its philosophy). While designing new experiment, what cares should be taken?

Welcome, ghjadhav. Are you asking about how the setup for the experiment itself should be performed or what would cause the greatest margin of error. As far as error, temperature control is a big factor.

[robross]

I think you have that backwards, Rob. We know the speed of light very precisely through other experiments, and use that information combined with the round-trip time for the light to return from the lunar reflectors to measure the distance to the Moon, which actually varies a bit throughout it's orbit, from 363,104 km to 405,696 km.

Whoops, yea, you're right. My bad.

Uhm, the sun was in my eyes when I wrote that? Or maybe the dog ate it.

Rob

[Jeff Root]

The dog ate all your reference notes and calculations. Good thing they
were on paper, not on your computer.

One possible theoretical problem is that, as far as I know, only two-way
measurements of light speed have been done. I've seen a couple of
proposals for one-way measurements. If I recall correctly, one would be
difficult, requiring multiple spacecraft in deep space; the other would be
easy, and could be done with a good oscilloscope and a few hundred feet
of optical fiber. (If you don't mind measuring the speed of light in glass
rather than vacuum.) I might be wrong about this second experiment.
It could be for measuring a difference between two speeds, not the
speed itself.

-- Jeff, in Minneapolis

[pzkpfw]

Welcome to BAUT, ghjadhav. Please make sure you check out the rules.

I've moved your thread here as it seemed you were looking for more of a discussion than asking a specific question.

I should note that MM is clearly an experiment accepted by mainstream science. If your discussion turns into you making certain kinds of claim this thread might need to get shifted to our "against the mainstream" (ATM) sub-forum - where you'll need to back-up those claims.

I don't mean to "scare you off" from your very first post here, but this seemed a relevant/useful note to make, given your post topic.

Cheers,

[mugaliens]

Uhm, the sun was in my eyes when I wrote that? Or maybe the dog ate it.

Rob

LoL! I'll buy the dog story, as it's worked for me!

[dhd40]

I think you have that backwards, Rob. We know the speed of light very precisely through other experiments, and use that information combined with the round-trip time for the light to return from the lunar reflectors to measure the distance to the Moon, which actually varies a bit throughout it's orbit, from 363,104 km to 405,696 km.

Well, there are other methods to determine the distance to the moon (and other celestial bodies) without knowing the speed of light, e.g. parallax shift methods.

Or this one from 270 BC

http://www-istp.gsfc.nasa.gov/stargaze/Shipprc2.htm

[mugaliens]

One possible theoretical problem is that, as far as I know, only two-way
measurements of light speed have been done. I've seen a couple of
proposals for one-way measurements. If I recall correctly, one would be
difficult, requiring multiple spacecraft in deep space; the other would be
easy, and could be done with a good oscilloscope and a few hundred feet
of optical fiber. (If you don't mind measuring the speed of light in glass
rather than vacuum.)

The oscilliscope method has been done. It's simply nowhere near as accurate as either the cavity resonance wavemeter or the interferometer.

[Jeff Root]

I can't say anything about the optical fiber/oscilloscope method until I look
up again what that proposed experiment was actually intended to measure,
but can you explain how one-way speed of light can be measured with an
interferometer setup?

-- Jeff, in Minneapolis

[mugaliens]

but can you explain how one-way speed of light can be measured with an
interferometer setup?

-- Jeff, in Minneapolis

Here you go - good diagram, great explanation. It's two-way, though, not one way.