This story on Reddit involves a 1 km by 1 km by 1.79 lightyear block of lead in deep space, and I was wondering if it was at all feasible (though that question is probably out of scope). To ask a more answerable question, how would I determine the surface gravity of such an object? In particular, how much gravity would you experience if you were standing in the middle of one of the two square sides?


closed as off-topic by Aaron Stevens, stafusa, Jon Custer, rob Aug 14 at 19:58

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  • $\begingroup$ What is your definition of "how much gravity"? $\endgroup$ – Aaron Stevens Aug 13 at 19:50
  • $\begingroup$ @AaronStevens "how much gravity" = how much acceleration due to gravity would you experience $\endgroup$ – Rob Watts Aug 13 at 20:10
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    $\begingroup$ FWIW, lead's pretty soft, and gravity will tend to convert the block to a sphere, with a radius a shade over 15930 km, assuming I didn't mess up the arithmetic (I used Google Calculator). $\endgroup$ – PM 2Ring Aug 13 at 20:46
  • $\begingroup$ @PM2Ring yes lead is soft, but consider a 1 mm by 1 mm version - all that put together into a sphere would give 0.005 m/s^2 surface gravity, but spread out over more than a lightyear? The gravitational pull seems like it would be negligible, allowing it to remain a rectangular prism. If you made it bigger at some point it would obviously pull itself together into a sphere, but where is that point? en.wikipedia.org/wiki/Hydrostatic_equilibrium#Planetary_geology suggests for spheres it's around 400 km for ice and somewhat more than that for rock. $\endgroup$ – Rob Watts Aug 13 at 22:25
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    $\begingroup$ arxiv.org/abs/1206.3857 $\endgroup$ – G. Smith Aug 14 at 0:57