undefined | Better HN

0 pointsbrummm3y ago0 comments

Just a small comment about the speed of light. The way we now define the speed of light, measuring it doesn't really make sense anymore. The speed of light is now DEFINED as 299792458 m/s and the meter definition is based on the speed of light. So in principle, one can only measure the meter and not the speed of light anymore.

0 comments

rightbyte3y ago

In vacuum.

enchiridion3y ago

Would it be the same in a hypothetical completely homogeneous gas?

My assumption is that turbulent changes in pressure cause diffraction, causing the light to not take a perfectly straight path. I don’t know enough about physics to know if that’s right.

CodesInChaos3y ago

The speed of light in a medium is the inverse of the refractive index of that medium. It's caused by the interaction between the electrons in matter (bound to atoms) and electromagnetic fields. It does not require inhomogenities larger than the atomic structure.

https://en.wikipedia.org/wiki/Refractive_index

liminvorous3y ago

Materials seem to have different refractive indices for some sort of complicated quantum reason that only relies on the inhomogenity because of materials being made up of atoms containing electrons, not an sort of macroscopic inhomogenity.

https://www.physicsforums.com/threads/how-does-refraction-wo... is the thread I'm basing this on

j / k navigate · click thread line to collapse