When it comes to measuring the "hardness" of a material, most tests are distinctly low-tech and basically involve pressing a diamond tip into the surface and measuring the size of the dent produced.

How do we know the mass of a planet originally appeared on Quora - the knowledge sharing network where compelling questions are answered by people with unique insights. Answer by Geoffrey Widdison on ...

Physics and Python stuff. Most of the videos here are either adapted from class lectures or solving physics problems. I really like to use numerical calculations without all the fancy programming ...