How long it takes a ball to drop on various Solar System bodies

James O’Donoghue made this straightforward animation that shows how long it takes for a ball to drop one kilometer on different planets:

It might be surprising to see large planets have a pull comparable to smaller ones at the surface, for example Uranus pulls the ball down slower than at Earth! Why? Because the low average density of Uranus puts the surface far away from the majority of the mass. Similarly, Mars is nearly twice the mass of Mercury, but you can see the surface gravity is actually the same… this indicates that Mercury is much denser than Mars.

Okay, sure, but what’s heavier on Mars: a ton of feathers or a ton of bricks? [via kottke]

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Gravity visualized in physics demo

Dan Burns explains some properties of time and space using marbles and two large pieces of spandex sewn together in a classroom demonstration.

https://www.youtube.com/watch?v=MTY1Kje0yLg

Physics and me never got along in high school and college, but I did always enjoy the low-budget demonstrations. It's one thing to see calculations on paper. It's another when the professor sets up a stuffed monkey on one side of the room and then shoots a sock out of a pressurized cannon angled at the trajectory you just calculated to make sure the sock hits the monkey on its way down from ceiling height.

Of course you can look it up on YouTube:

https://www.youtube.com/watch?v=cxvsHNRXLjw

In retrospect, shooting a monkey falling out of a tree seems kind of wrong.

And while we're at it, I always liked this demo too. A bicycle wheel gyroscope hangs from a rope, and when it spins its axis stays horizontal like magic.

https://www.youtube.com/watch?v=8H98BgRzpOM

MIT has a 43-demo playlist if you need something to watch during your lunch hour.

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