John Carlos Baez on Nostr: nprofile1q…chszg - to not notice that we were falling into an enormous black hole, ...

nprofile1qy2hwumn8ghj7un9d3shjtnddaehgu3wwp6kyqpqez3yya8tpgge7lk4jq2zxz0cj3d2mcgev9mffd4ec7tfy84hre4sqchszg (nprofile…hszg) - to not notice that we were falling into an enormous black hole, its radius would need to be roughly the radius of the observed universe or larger, e.g. 14 billion light years. We have no reason to think such ridiculously large black holes exist, much less that we're falling into one. It's fun to think about how massive such a black hole would need to be... let's see, I'm getting that a black hole of radius 1 light year must be 3 trillion times as heavy as the Sun, and the radius is a linear function of the mass, so for one to be 14 billion light years in radius, it would need a mass about 4 ×10²² that of our Sun. By comparison the Milky Way is a puny 1.5 ×10¹² solar masses, so we're talking a mass of roughly 30 billion Milky Ways.