Why is the speed of light 186,000 miles per second?

[|Glitch|]

Why is the speed of light 186,000 miles per second? Is that how fast the ether will allow it to travel?

First and foremost, the speed of light has been converted into a completely arbitrary unit of measure that we can comprehend. About 339 years ago Danish Astronomer Ole Rømer determined that light had a finite speed. Since then we have been able to observe and measure the speed of light in a vacuum with great precision (299,792,458 m/s with a measurement of uncertainty of 4 parts per billion). Furthermore, we have since changed the unit of measure, making one meter equal to the distance light travels in a vacuum at 1/299,792,458 of a second. Therefore, the unit of measure "meter" is now fixed to the value of c in meters per second.

The short answer is that the speed of light has the specific velocity it does because we have observed and accurately measured it. We do not know why light moves at that specific velocity, just like we do not know what gives mass gravity. But we can measure the speed of light and understand its effects, just like we can with gravity.

and if that is the case, if the edge of the universe; the edge to which the universe is speeding up, would the ether out there let light travel at higher or lower speeds? Which to me means that light is 186,000 miles per second in our are of the universe?

The speed of light can be slowed down, but not sped up. Although, there have been theories that suggest certain hypothetical particles can travel faster than the speed of light, just as tachyons, but they have never been observed. When visible light hits our atmosphere all kinds of things start happening, from scattering, absorption, emission, and reflection. As a result, the speed of light is slowed down by ~90 m/s as it passes through our atmosphere.

 

[thejun]

Yes, remember, my question is not how you measure things directly (a kilometer), or indirectly (slamming protons together and performing a rule out process to get the measurement you want). measurements are just a way to quantify something. A lot of you say light can slow down in air, or in water. so the water is determining the fastest speed it can travel. well in space i think its the same thing, that I'm calling the ether. maybe its why dark matter clumps, who knows.. I'm just thinking out loud. now if this ether exists, the edge of the expansion, it may be stretched, therefore light may go faster there by default, maybe that explains why it looks like its increasing faster when its really not. I have a dozen more questions, but verrrry curious what you guys think about this!

 

[Nugatory]

Yes, remember, my question is not how you measure things directly (a kilometer), or indirectly (slamming protons together and performing a rule out process to get the measurement you want). measurements are just a way to quantify something. A lot of you say light can slow down in air, or in water. so the water is determining the fastest speed it can travel.

You can calculate the speed of light in vacuum from the observed behavior of electrical and magnetic fields in a vacuum, and you can calculate the speed of light in air and water by allowing for the observed differences in the behavior of electrical and magnetic fields in those mediums.

well in space i think its the same thing, that I'm calling the ether. maybe its why dark matter clumps, who knows.. I'm just thinking out loud. now if this ether exists, the edge of the expansion, it may be stretched, therefore light may go faster there by default, maybe that explains why it looks like its increasing faster when its really not. I have a dozen more questions, but verrrry curious what you guys think about this!

Please remember that any posts that argues for something on the basis of "I think" is likely a violation of the Physics Forums rules prohibiting personal theories and speculation; this part of your post certainly is.

As a matter of history, there was once a hypothesis that something in empty space called "ether" was the medium through which light propagated in a vacuum. This hypothesis died in 1905 when it became clear that it wasn't needed - the straightforward ether theories don't match experimental results and the complicated ones answer only a subset of the questions that special and general relativity answer.

 

[mfb]

maybe its why dark matter clumps, who knows

Speculations without any model backing that up are pointless.

There is no indication of any "edge of expansion". The universe looks the same in all directions, and no model predicts anything in space that could be called "edge".

 

[Niflheim]

Yes, remember, my question is not how you measure things directly (a kilometer), or indirectly (slamming protons together and performing a rule out process to get the measurement you want). measurements are just a way to quantify something. A lot of you say light can slow down in air, or in water. so the water is determining the fastest speed it can travel. well in space i think its the same thing, that I'm calling the ether. maybe its why dark matter clumps, who knows.. I'm just thinking out loud. now if this ether exists, the edge of the expansion, it may be stretched, therefore light may go faster there by default, maybe that explains why it looks like its increasing faster when its really not. I have a dozen more questions, but verrrry curious what you guys think about this!

You can think it's the "same thing" all you want, it isn't. As multiple people have repeatedly told you, the ether does not exist. A vacuum is truly empty, there is nothing there. And why would c be constant here and everywhere else in the universe that we can observe but not at the "edge" of the universe, which has also been proven not to exist? It sounds like you really don't have all the facts here, I would consider doing some more research on the topic. I would recommend Stephen Hawking's a Brief (or Briefer) History of Time to give you the basic facts.

 

[thejun]

the universe cannot look the same in all directions, that doesn't make sense at all. Everything you guys say is speculation, and you are criticizing my question. I don't want you to answer it with facts. i know that is impossible. But I am a person that tries to think outside the box. you say that space is a vacuum, there is nothing there, then all of a sudden there is dark matter and dark energy, which no one can see, yet you are ok with believing that. And your right nugatory, I apologize for asking this here.

 

[Nugatory]

the universe cannot look the same in all directions, that doesn't make sense at all.

Have you looked? It is an observational fact that, to the limits of accuracy of our devices, the universe is indeed isotropic on a large scale (which is what people mean when they use the less precise "looks the same in all directions"). One of the harder lessons for humans to absorb is that the universe really doesn't care what we think makes sense - it is the way it is.

... you say that space is a vacuum, there is nothing there, then all of a sudden there is dark matter and dark energy, which no one can see, yet you are ok with believing that.

The dark energy and dark matter hypotheses do not disagree in any way with the experimentally confirmed theories of how a vacuum behaves, and "space is a vacuum" is a misstatement of what scientists say about what's in space. Yes, you will hear even professional scientists say "space is a vacuum" when they're speaking to a non-technical audience... but that's a simplification for a non-technical audience. A strictly correct description would be something along the lines of "a perfect vacuum is a very good approximation for outer space; there's a little bit of stuff, maybe a few atoms or so, in every cubic meter of space, but so little that its effects are locally negligible".

 

[Nugatory]

We can close this thread at this point. The original question has been answered, and the subsequent discussion into other topics that should be discussed in their own threads or not at all.