Category Archives: Relativity

Q: What would you experience if you were going the speed of light?

The original question was: If I’m moving at the speed of light towards you and I throw a tennis ball at you (at, say, 5 m/s), what do you observe? Will I hit you first, the tennis ball, or both … Continue reading

Posted in -- By the Mathematician, Physics, Relativity | 56 Comments

Q: What is a magnetic field?

Physicist: Magnetic fields are nothing more than the result of combining an electric field with the effects of relativity. First some background.  Magnetic fields were first defined in such a way that iron filings will point in the direction of … Continue reading

Posted in -- By the Physicist, Physics, Relativity | 32 Comments

Q: In the NEC “faster than light” experiment, did they really make something go faster than light?

The original question was: I was reading an article by Lijun Wang the experiment I think is called the NEC experiment.  Basically what the guy does is speed up light so that it goes faster than the than the speed … Continue reading

Posted in -- By the Physicist, Physics, Relativity, Skepticism | 15 Comments

Q: How does the Twin Paradox work?

The original question was: I have a question about the twin paradox.  Is it true that faster aging of the twin who stayed at home happens only when the other twin’s spaceship is accelerating/deceleration (btw, does it matter whether he … Continue reading

Posted in -- By the Physicist, Physics, Relativity | 57 Comments

Q: How can photons have energy and momentum, but no mass?

Physicist: Classically (according to Newton) kinetic energy is given by and momentum is given by , where m is mass and v is velocity.  But if you plug in the mass and velocity for light you get .  But that’s … Continue reading

Posted in -- By the Physicist, Relativity | 227 Comments

Relativity and Quantum Mechanics: the elevator pitch

Physicist: A woman on the subway, about two stations away from her stop, asked us “what are relativity and quantum mechanics?” So, this is a two-stop elevator pitch for the two most pivotal sciences since slicedbreadology. Relativity: Speed is just … Continue reading

Posted in -- By the Physicist, Quantum Theory, Relativity | 3 Comments