Read it, learn from it, enjoy it.
This page is the boring fine print, kept as short as we could make it. The gist: the site is free, it's here to teach, and we don't promise it's perfect.
Free to read
Everything on this site is free and meant for learning. Use it for homework, for curiosity, for teaching someone else. Quote a page, share a link, point a friend at a simulator. That's exactly what it's for.
The explainers are simplified on purpose
To teach a thing well, you have to leave some of it out at first. So the answers here trim the edges to make the core idea clear. That's a feature, but it means nothing on this site is professional advice. Don't lean on it for a medical decision, a safety call, or anything with real stakes. For that, talk to someone qualified.
It comes as-is
We work hard to keep the science right and the simulators honest, but we can't promise the site is always correct, always up, or free of mistakes. It's offered as-is, with no warranty of any kind. If you spot an error, please tell us. Corrections are the most useful thing you can send.
Please respect copyright
The writing, artwork, and simulators here took real effort. By all means quote and link to them, but don't pass the work off as your own or republish whole pages under a different name.
Links and ads aren't endorsements
The ads on the site come from Google and the businesses that pay them, not from us. We don't pick them one by one and we don't vouch for them. The same goes for any outside link. Treat them with the usual care you'd give anything on the web.
Something wrong?
If a page is off, an ad is out of line, or you have a question about any of this, the contact page will reach us.