John Rennie
Reputation
99/100 score
 23h answered Exercise 18b in Schutz's First course in GR 1d awarded Guru 1d comment Spring constant and a spring's decompressed length Related and possibly a duplicate: Does the stretching of a spring depend on its rest length? 1d answered General Relativity, Curvature, and extra dimensions 1d revised According to Ohm's Law, shouldn't there be a zero electric potential within a capacitor since the current is 0? Tweak 1d revised How can I calculate how high an arrow goes when all I know is its initial speed? I'm not taking my clothes off in the name of physics 1d answered Does the speed of light change? 1d comment Producing negative energy/exotic matter with particle accelerator for warp drive Related: Exotic Matter — What is it? 1d comment What is the isochronic law of pendulums? I'm voting to close this question as off-topic because it shows insufficient prior research 1d revised How to find the current source Is and the voltage V1 of this circuit schematic? edited tags 1d comment Can speed of light be $c$ in air or other medium? @igael: In practice you would only work with polaritons when the coupling is very strong e.g. in a BEC. Nevertheless the principle applies. Once the light starts interacting with a dielectric is is no longer just an EM wave and therefore doesn't travel at $c$. 1d answered Prospects for detection of gravitons? 1d answered Can speed of light be $c$ in air or other medium? 1d reviewed Looks OK Could LIGO discovery be due to e.g. earthquakes or have a terrestrial source? 1d comment induction of voltage from power lines to telephone lines Hi and welcome to the Physics SE! Please note that this is not a homework help site. Please see this Meta post on asking homework questions and this Meta post for "check my work" problems. 1d comment Producing negative energy/exotic matter with particle accelerator for warp drive No. Next question? 1d comment Does the speed of light change? @DerbR. this is a site for, and I quote from the tour, a question and answer site for active researchers, academics and students of physics and astronomy. Everyone is welcome, but we expect you to be willing to put some effort into your questions and a basic search of this site is part of the required effort. In relativity the speed of light is constant because it's a geometrical property. Have a browse through the search I suggested in my first comment to learn more. 1d reviewed Leave Closed complex waveforms 1d comment Does the speed of light change? I'm voting to close this question as off-topic because it shows insufficient prior research. 1d comment Does the speed of light change? Hi Derb. You need to have a look at all the many other questions asking why the speed of light is constant, and then refine your question to explain exactly why you think the speed of light might be changing.