3 ms·

Ah, good point! I'm not sure that it would still win versus point-sized Earth - according to this [1], shrinking Earth to half its size would increase gravity

Ah, good point! I'm not sure that it would still win versus point-sized Earth - according to this [1], shrinking Earth to half its size would increase gravity 4x. And a point is obviously much smaller than half. But still, to see how incredibly weak gravity is consider that you don't even have to consider the gravitational pull of the magnet. Even if you walk next to a mountain you don't have to think twice about falling toward it. Gravity is negligible at even monstrously huge scales! It's just not a very large force at all, compared with magnetism, electricity, or e.g. solar radiation. It's truly weak. I've never had to think about the gravitational pull of any object other than literally the Earth or maybe occasionally the moon (which has a mass of 7.35x10^22 kg, or 1.2 percent of Earth's mass -- i.e. the Earth and the 5 septillion kilos I quoted is only 81 times as large.) The everyday pull of objects (for example the pull by which the building next to you right now is attracting you) is so negligible. It's weak! [1] https://www.quora.com/If-the-earth-shrinks-half-of-its-radius-and-its-mass-remains-same-what-would-be-the-weight-of-objet-on-earth https://www.quora.com/If-the-earth-shrinks-half-of-its-radiu...

tzs 10y ago
Yeah, I expressed myself poorly when I said shrunken Earth at the same distance from the object as the magnet would lose. What I wanted to convey was that if you could get the mass closer to the object, you wouldn't need anywhere near 5.972 × 10^24 kg anymore. For instance, if you had a sphere whose center of mass was 1 m from your test object, and wanted it to exert the same force that the Earth exerts 6.7 x 10^6 meters from the object, you would only need your sphere to have a mass of 1.33 x 10^11 kg. If we were using a sphere small enough that we could get its center of mass 10 mm from our test object's center of mass, it would only a mass of 1.33 x 10^7 kg. So, the magnet is still winning in the sense that it still takes a lot of mass to counter the magnet, but we're talking 10^7 kg, not 10^25 kg.
- logicallee 10y ago
  >but we're talking 10^7 kg, not 10^25 kg which, let's not forget, is still 10,000,000 kg! But it gets worse. The thing I quoted, which generates 150 lbs of magnetism -- only weighs 0.3 ounces!! (0.01875 lbs or 0.0085 kg). were your figures for 150 lbs or for 0.018 lbs of gravitational force from a point source? :)

tzs 10y ago

Yeah, I expressed myself poorly when I said shrunken Earth at the same distance from the object as the magnet would lose. What I wanted to convey was that if you could get the mass closer to the object, you wouldn't need anywhere near 5.972 × 10^24 kg anymore. For instance, if you had a sphere whose center of mass was 1 m from your test object, and wanted it to exert the same force that the Earth exerts 6.7 x 10^6 meters from the object, you would only need your sphere to have a mass of 1.33 x 10^11 kg. If we were using a sphere small enough that we could get its center of mass 10 mm from our test object's center of mass, it would only a mass of 1.33 x 10^7 kg. So, the magnet is still winning in the sense that it still takes a lot of mass to counter the magnet, but we're talking 10^7 kg, not 10^25 kg.

logicallee 10y ago
>but we're talking 10^7 kg, not 10^25 kg which, let's not forget, is still 10,000,000 kg! But it gets worse. The thing I quoted, which generates 150 lbs of magnetism -- only weighs 0.3 ounces!! (0.01875 lbs or 0.0085 kg). were your figures for 150 lbs or for 0.018 lbs of gravitational force from a point source? :)