Stephen Wolfram answers general questions from his viewers about science and technology as part of an unscripted livestream series, also available on YouTube here: https://wolfr.am/youtube-sw-qa

Questions include: What causes snow? Why doesn't rain just turn into ice? - OK, Stephen really knows his stuff on this branch of physics... he's studied in detail. - Why is the density of solid water lower than liquid water? - Is there any other molecule that also expands when it is solid? - Why is the density of solid water lower than liquid water? - For ice skating, the ice melts at the contact of your blade so there is a small layer of liquid water due to friction, and hence it skates. - But you also can push and speed up on ice while skating, so an increase in the friction must have happened? - Apparently, gecko feet exhibit Casimir-like effects. - Stephen, if I may make a suggestion: you need a blackboard (or whiteboard) behind you for the explanations. - Is air a molecule? What is air? - Can you measure the absorption of CO2 by plants with this device?