#massless

Why does time stand still for photons? I get the fact that we can never reach the speed of light due to our invariant mass and I also get that the faster we move through space, the slower we move through the time, but I just don't get why the speed of light should be our zero point for T (i.e. in which time stands still for the observer).

Ask Ethan: How Do Massless Particles Experience Gravity?

“Given the equation for gravity between two masses, and the fact that photons are massless, how is it possible for a mass (like a star or a black hole) to exert influence on said photon?”

You know the law of universal gravitation: you put in what any two masses are, how far apart they are from each other, and the gravitational constant of the Universe, and you can immediately know what the force is between any two objects. Set one of the masses to zero, and the force goes to zero. So why is it, then, that if you take the ultimate particle with no mass, a photon, and pass it close by a mass, its path does bend? Why do massless particles experience gravity?

To understand why, you should think about what happens if you and I start at the same place near a mass, but I’m stationary and you’re moving. How far away is that mass? What’s the “r” that goes into Newton’s equation? And who’s right: me or you?

Shape-shifting neutrinos earn physicists the 2015 Nobel

Super-Kamiokande, a neutrino detector in Japan, enabled Takaaki Kajita, one of this year’s recipients of the Nobel prize in physics, to make his discovery: that neutrinos flip-flop between identities, and that they must have mass. Photo: Super-Kamiokande

What do Albert Einstein, Neils Bohr, Paul Dirac, and Marie Curie have in common? They each won the Nobel prize in physics. And today, Takaaki…

Graviton - "Mu Lepton/Boson"