# Monthly Archives: January 2011

## Q: Why is it that (if you exclude 2 & 3) the difference between the squares of any two prime numbers is divisible by 12?

Physicist:  That’s a really cool property! Every prime number (other than 2 and 3) can be written in the form 6j+1 or 6j+5.  For example, 17 = 6(2)+5 and 31 = 6(5)+1. This is because numbers of the form 6j, … Continue reading

Posted in -- By the Physicist, Brain Teaser, Math, Number Theory | 6 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 | 19 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 | 16 Comments

## Q: If atoms are mostly made up of empty space, why do things feel solid?

Physicist: (The following paragraph is wrong.  Like, really wrong.  There’s a redaction here: My bad: If atoms are mostly made up of empty space, why do things feel solid?) As atoms get too close to one another their charges begin … Continue reading

Posted in -- By the Physicist, Particle Physics, Physics | 70 Comments

## Q: Can we build a planet?

Physicist: In theory, there’s nothing standing in the way.  In fact by constructing a planet from asteroids, comets, or dust you can expect to get a fair amount of energy back out.  Normally, you’d just chuck a bunch of dust, … Continue reading

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

## Q: π = 4?

Physicist: Recently this picture has been floating around confusing everyone, and making people think that maybe Indiana wasn’t completely off base when they moved to declare that . The exact answer to this question comes from deep in the field … Continue reading

Posted in -- By the Physicist, Geometry, Math | 16 Comments