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A long while back, I read a scifi book (really a kids scifi book) about a kid that finds a red pebble which cancels gravity for anything it's in contact with (e
by mnw21cam 13y ago
A long while back, I read a scifi book (really a kids scifi book) about a kid that finds a red pebble which cancels gravity for anything it's in contact with (except kids, obviously), causing those objects to be pulled strongly up into the sky. Why? Because they were attracted by the moon's gravity. They even got it to spin round and suggested using that for free energy. Can't for the life of me remember the title or author, but I remember it really grated against my sensibilities, and I never read anything by the same author again.
- cynicalkane 13y agoIf you had a way to cancel gravity, you could use that to get free energy because the no-curl condition for energy conserving fields would no longer hold. You could create a closed path in space where gravity is always pulling you along the path.
- dTal 13y agoI couldn't resist crunching the numbers: the acceleration due to the moon's gravity as felt from the Earth is roughly 3.319×10^-5 m/s². By contrast, the centripetal acceleration due to Earth's rotation is 0.0337 m/s², several orders of magnitude larger (and just about perceptible as a gentle tendency to float up). (A similar example to your red pebble would be "Cavorite" from the H. G. Wells story "The first men in the moon", which also negated gravity causing objects to shoot violently upwards. The explanation given however was buoyancy, which makes more sense I suppose.)
- teahat 13y agoPretty sure it was Antigrav by Nicholas Fisk. It was a cool story - if you were a kid. I never did find any red pebbles though.
- mnw21cam 13y agoThat sounds about right.