Category Archives: Relativity

Q: As a consequence of relativity, objects becomes more massive when they’re moving fast. What is it about matter that causes that to happen?

Physicist: The laws of the universe are relativistic.  That is, Einstein was right and Newton, although accurately and intuitively describing the world around us, was wrong.  When you try to translate the cleaner Einstein laws into a Newtonian form you … Continue reading

Posted in -- By the Physicist, Physics, Relativity | 12 Comments

Q: Why does E=MC2 ?

Physicist: It’s a little surprising that this question didn’t come up earlier.  Unfortunately, there’s no intuitive way to understand why “the energy of the rest mass of an object is equal to the rest mass times the speed of light … Continue reading

Posted in -- By the Physicist, Physics, Relativity | 81 Comments

Q: Why does relativistic length contraction (Lorentz contraction) happen?

Physicist: This probably should have come before the last post. Length contraction is a symptom of “tilted now planes”.  For someone moving past you events physically in front of them happen earlier than they should (according to you), and events … Continue reading

Posted in -- By the Physicist, Physics, Relativity | 24 Comments

Q: Why does Lorentz contraction only act in the direction of motion?

Physicist: A lot of things get messed up by relativity, like when and where stuff happens, how massive things are, or how time passes.  Length contraction is an effect that literally makes things shorter in the direction of motion.  So … Continue reading

Posted in -- By the Physicist, Physics, Relativity | 22 Comments

Q: Why does “curved space-time” cause gravity?: A better answer.

Physicist: The original post is here. The curvature of space alone has almost no effect on the movement of objects until they are moving really fast.  With the exception of only the most extreme cases (black holes), space is very, … Continue reading

Posted in -- By the Physicist, Mistake, Physics, Relativity | 123 Comments

Q: According to relativity, two moving observers always see the other moving through time slower. Isn’t that a contradiction? Doesn’t one have to be faster?

Physicist: They definitely both experience time dilation.  That is to say, they both see the other person moving through time slower (you will always see your own clock running normally, in all circumstances).  The short resolution to the “paradox” is: … Continue reading

Posted in -- By the Physicist, Philosophical, Physics, Relativity | 43 Comments