What dinosaur made this track? Ah yes, ol' Saladtongosaurus. (John Kennedy/) Welcome to PopSci’s at-home science projects series. On weekdays at noon, we’ll be posting new projects that use ...

It's a Friday summer weekend. Brain is fried. Concentration, which isn't all that swift on a good day, is... what's that word? Which means that it's a good time to do something fun.