8k views

### What is so special about speed of light in vacuum?

I will try to be as explanatory as possible with my question. Please also note that I have done my share of googling and I am looking for simple language preferable with some example so that I can get ...
18k views

### Is there a proof of existence of time?

It seems to me that there is no such thing as time. There is only movement in the universe and we compare our own movement to a different object to have a sense of time. It can be a clock or a atomic ...
4k views

### Do Maxwell's equations independently impose constraints on the speed of light?

My question is about the relations and equations that makes us to impose constraints on the velocity at which electromagnetic waves propagate. Do Maxwell's equations independently impose constraints ...
417 views

### Photon mass and life time

In this article, the author tried to explain that, Einstein's theory may not valid because he says "photon can decay because it may have minute amount of mass". I'm totally in a conundrum state that ...
313 views

### What if EM or QCD was spontaneously broken?

Suppose that Standard Model Higgs mechanism broke electromagnetism, by e.g. veving the charged component of the doublet, so that the photon was massive with $m_\gamma\sim v$. Could such a Universe ...
1k views

### Can light exist without spacetime?

Since the medium in which light propagates is spacetime, would light be able to exist if spacetime did not exist? Is this like one of those chicken/egg problems, or can light be thought of as a ...
238 views

### How can we experimentally tell the difference between particles with and without rest mass?

We only observe their decay products and that is what the rest-mass is reconstructed from. Also, there is a whole issue of running coupling which means that rest mass per se actually doesn't make ...
197 views

### Causality without light

Related to my prior question: Would it be possible to develop special relativity without knowing about light? Imagine a species insensate to light and other em radiation. They are very attuned to ...
### What $E=mc^2$ has to do with nuclear formation?
I am a bit confused that what actually the Einstein's equation meant to describe binding energy wht is that $c^2$ for as when nucleon combine what is the need of speed of light in equation?