See it work
These are not illustrations. Each one is the actual physics, running in your browser: move a slider and everything else follows, the way it would on the real world it belongs to. A drawing can tell you a sky has two suns. Only a working model can show you what that does to the ground at your feet.
- What would a world with two suns actually look like?Almost every version you have seen gets it wrong in the same way. The real thing is stranger, and you can read the date off your own shadow.Interactive6 min read
- What would you weigh inside a hollowed-out world?Not less and less until you are crushed. Less and less until there is nothing left to pull you at all — across a whole room, not just at one point.Interactive6 min read
- What does a heavy thing actually do to the space around it?Not pulling, not radiating, not reaching out. Something quieter than that, which never entirely stops, anywhere in the universe.Interactive5 min read
- Why does pushing something send you the other way?On the ground you never notice, because the planet takes the other half. Take the ground away and the arithmetic arrives all at once.Interactive5 min read
Every one of them is also an article. The toy shows you the thing; the writing underneath explains it. You can play with it and leave, or read the whole answer — both are the point.