Speed of Light in a Vacuum

>>8606956
There HAVE been experiments in vacuum. And they have verified that speed of light is 3*10^8 m/s.
However, air has a very small diffraction coefficient (about 1.01) and so the velocity for air is almost the same as c.

>>8606956
The instantaneous velocity of a photon never changes. The only reason why light is "slower" going through a transparent or translucent material is because it is being refracted and thus is not taking a direct path from the source to the viewer.

>>8606964

What experiments? That's what I'm trying to see. How did they do it?

>>8606983
The simpler method is to use a vacuum pump to remove the air from a closed volume.
Then start the laser.

>>8606956
>the maker of OP's image couldnt convert m/s to mph to make the sign more authentic
Garbage image pls delete

>>8606956
The first time it was attempted in near vacuum:
http://adsabs.harvard.edu/full/1935CMWCI.522....1M

Modern measurements:
http://tf.nist.gov/general/pdf/1778.pdf

http://www.npl.co.uk/about/history/research/speed-of-light/

>>8606956
>Is there an experiment that can prove light can pass through a vacuum?
>It takes ... light from the sun about 8 minutes and 20 seconds to reach Earth.
>Tell me why I'm dumb.
If not a vacuum, what do you think lies between the Sun and the Earth?

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>>8606956
>Vacuum

No such thing in nature.

>>8606956
>If the speed of light slows down in water

The speed of light does not change. Speed != velocity

>>8607645
yeah there is
see: space

>>8607878
>See the aluminium props in a Hollywood basement
lol Americans...

>>8606956
It should also be affected by gravity; citing photons that do not escape black suns (holes). They must be slowed down unless it's some relativity thing going on.
How would anyone measure vacuum anyway? What is it? The lack of breathable air? Extremely few O2 molecules? Lack of dust? Hard to contain a region of space that contained no dust, even in the deep, dark, despairing depths of space between stars.

>>8607442

Assuming space and dark matter is real.

>>8608255

Assuming gravity is real over electromagnetism

I just wanted someone to provide evidence. Why can't we get two satellites in space then point lasers between them and find the speed?

>>8608266
>Assuming space and dark matter is real.
are*
Good grief. Are you a flat Earther / Moon landing was a hoax kind of guy?

>>8608318
I suppose they could use two satellites. But why do something that costs so much, when it could be done for so much less? For instance, pointing at the reflector on the Moon?

>>8608602
It costs nothing, they already have it! You fucking idiot, radio waves are still light... Geez weez kid

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>>8608609
Before you go calling the kettle black, pot...
Can you name any two satellites that have been designed such that they can communicate with each other for the purpose specified?
Or were you just in a hurry to ambush someone with what you though twas a clever trap?

>>8608609
BTW... the post specified lasers. Not radio waves.
>>8608318

Get a hold of yourself. You're a bit unstable.

The definition of a "meter" is the distance travelled by light in vacuum 1/c seconds. Therefore, the speed of light is exactly c.