4 ms·

Doesn't that proposal merely ~halve the amount of mass required? I'm in an office right now that has a ceiling made out of normal matter (gypsum, fiberglass, s

Doesn't that proposal merely ~halve the amount of mass required? I'm in an office right now that has a ceiling made out of normal matter (gypsum, fiberglass, steel, and tar, probably a couple thousand kg overhead) and a floor also made out of normal matter (carpet, concrete, iron, silicon, oxygen, and a bunch of other stuff adding up to 6x10^24 kg), which generates artificial gravity at 1g. It happens to be rotating at 1/1440 RPM, but that's only a 0.2% reduction in the acceleration. Sure, if antimatter caused anti-gravitational forces, you could have achieved the same gravitational acceleration I experience in my office using one 3x10^24 kg sphere of antimatter overhead and one 3x10^24 kg sphere of matter beneath, but that's still not a Starship Enterprise, much less an X-wing, with artificial gravity generators. You're still stuck at: F = G x m_matter / r^2 + G x m_antimatter / r^2 F = 4 x pi / 3 x G x density x radius_matter + 4 x pi / 3 x G x density x radius_antimatter with planet-sized masses and radii for both. And I'm not sure that "hilariously" is a sufficient modifier for the danger level when standing in a 3m gap between planet-sized spheres of matter and antimatter.

eesmith 3y ago
Heinlein had a discussion about the "place a large mass just over a particular point on the Earth's surface" approach in "- We Also Walk Dogs" at https://archive.org/details/isbn_9780739410516/page/306/mode/2up?q=%22large+mass+just+over%22 https://archive.org/details/isbn_9780739410516/page/306/mode... . How big as mass? After some calculations on a slide rule: > “I’m almost afraid to answer. You would need a good sized asteroid, of lead, to get anywhere at all.” > “Asteroids have been moved before this.“ > “Yes, but what is to hold it up? No, Chief, there is no conceivable source of power, or means of applying it, that would enable you to hang a big planetoid over a particular spot on the Earth’s surface and keep it there.” But wait, what about something dense, like core material from a dwarf star? > “All we would need for that would be a ship capable of going light-years in a few days, some way to mine the interior of a star, and a new space-time theory.” > “Oh, well, skip it." Oh, yeah. In this space-age future where people can travel across the Solar System, they also use punched cards.

eesmith 3y ago

Heinlein had a discussion about the "place a large mass just over a particular point on the Earth's surface" approach in "- We Also Walk Dogs" at https://archive.org/details/isbn_9780739410516/page/306/mode/2up?q=%22large+mass+just+over%22 https://archive.org/details/isbn_9780739410516/page/306/mode... . How big as mass? After some calculations on a slide rule: > “I’m almost afraid to answer. You would need a good sized asteroid, of lead, to get anywhere at all.” > “Asteroids have been moved before this.“ > “Yes, but what is to hold it up? No, Chief, there is no conceivable source of power, or means of applying it, that would enable you to hang a big planetoid over a particular spot on the Earth’s surface and keep it there.” But wait, what about something dense, like core material from a dwarf star? > “All we would need for that would be a ship capable of going light-years in a few days, some way to mine the interior of a star, and a new space-time theory.” > “Oh, well, skip it." Oh, yeah. In this space-age future where people can travel across the Solar System, they also use punched cards.