Deeply Hidden ThingsGravity & Relativity
Why does everything fall? Three complete lessons, both versions, no account. Start at the top — they build on each other.
Why Does Everything Fall?
With the air out of the way, everything falls the same — whatever it is made of.
Needs: hardcover book, sheets of paper, tissue
The Straightest Path
Nothing is pulling you down.
Needs: something round, a tapered cup, a straight-sided tube
Falling Forever
Nothing is holding anything up.
Needs: paper or plastic cup, water, towel
Why your phone knows where you are
After the three lessons: a thorough look at how general relativity is running in GPS — written for a child and a grown-up at the same table.
Nothing that identifies you. Progress through the child’s lessons is saved in your own browser and never sent to us. Those lessons — and In the world — load no analytics, no advertising, and no third-party scripts.