Tag
6 articles on this topic.
Blog
It started with two rules: bonds have a length, and things attached to the same atom push each other away. That got methane its tetrahedron and benzene its hexagon. Then water needed lone pairs, ethene needed a reason not to fold in half, ethane needed a reason to stagger, and copper needed to be told. Here is what each rule bought, and what the ones I tried and threw away did not.
Blog
Drop charged vertices into a 3D workspace, join them, and let them settle. Every Platonic solid comes out with its edges equal to within a thousandth, from an energy that has no notion of an angle and no rest length. The Archimedean solids come out wrong, and the reason why turns out to be the interesting part.
Blog
The seconds hand moves because a balance wheel is vibrating, and for no other reason. Wind the crown, pull it out to set the time, put it on a wrist and let the rotor wind it for you, and fade the bridges away to watch the escapement lock, unlock and impulse five times a second.
Blog
A total eclipse is a cosmic coincidence: a moon that just barely covers the sun. This app lets you move through the Sun, Moon and Earth system and watch the geometry that decides which patch of the planet falls into shadow.
Blog
Dig a straight tunnel between any two points on Earth, pump out the air, and let gravity supply the propulsion. The trip takes 42 minutes, and the remarkable part is that it takes 42 minutes no matter which two cities you pick.
Blog
The Earth stays in orbit because of its angular momentum. Take that away, stopping the planet dead in its tracks, and how long until it reaches the Sun? Working out the answer turns up an unexpected appearance by pi.