Could the speed of light be variable?

AI Thread Summary
The speed of light is not constant across different substances, as it varies based on the refractive index, traveling slower in water than in air or vacuum. Current theory maintains that the speed of light in a vacuum is constant, though some hypotheses suggest it may have changed over time, albeit with limited evidence. The discussion also explores whether an object can exceed the speed of light in water, indicating that relativistic equations may change when conducted in mediums other than a vacuum. Cherenkov radiation is cited as a relevant phenomenon in this context. Overall, the conversation centers on the complexities surrounding the speed of light and its implications in various mediums.
Dremmer
Messages
92
Reaction score
0
Could the speed of light be variable? (not always travel at the same speed)
 
Science news on Phys.org
The speed of light (in current theory) in a vacuum is constant. However, some possibilities have been raised that it might have varied over time, but the evidence is at best scanty.
 
This is a related question...

Could the speed of light through water be exceeded by an object traveling through water. In other words does the C change for all of the relativistic equations if the experiment is conducted in a medium other then vacuum?
 
Thread 'A quartet of epi-illumination methods'

Thread 'A quartet of epi-illumination methods'

Well, it took almost 20 years (!!!), but I finally obtained a set of epi-phase microscope objectives (Zeiss). The principles of epi-phase contrast is nearly identical to transillumination phase contrast, but the phase ring is a 1/8 wave retarder rather than a 1/4 wave retarder (because with epi-illumination, the light passes through the ring twice). This method was popular only for a very short period of time before epi-DIC (differential interference contrast) became widely available. So...
View full post »

Thread 'Effective absorption coefficient of gold nanoparticles'

I am currently undertaking a research internship where I am modelling the heating of silicon wafers with a 515 nm femtosecond laser. In order to increase the absorption of the laser into the oxide layer on top of the wafer it was suggested we use gold nanoparticles. I was tasked with modelling the optical properties of a 5nm gold nanoparticle, in particular the absorption cross section, using COMSOL Multiphysics. My model seems to be getting correct values for the absorption coefficient and...
View full post »

Similar threads

I What travels faster: visible light in water or X-rays in liquid mercury?
Replies
6
Views
2K
B Is light breaking its own speed limit when cornering?
Replies
25
Views
2K
Speed of Light when not in a vacuum?
Replies
5
Views
6K
Measuring the speed of light in a straight line
Replies
19
Views
2K
Achieving the speed of light at the end of a whip
Replies
15
Views
5K
Circuits and the Speed of Light
Replies
2
Views
923
Will Headlights Work If My Car Travels Near the Speed of Light?
Replies
1
Views
10K
Why does the speed of light change in different media?
Replies
4
Views
4K
Speed of Light x2: Car Travel & Bullets Fired
Replies
21
Views
3K
Why is the speed of light smaller in a medium?
Replies
23
Views
3K

Hot Threads

Recent Insights

Back
Top