John M: > >Cher Quentin, >let me paraphrase (big): > >so someone had an assumption: BH. OK, everybody has the right to fantasize. >Especially if it sounds helpful.
Well, the basic assumption was more broad than that: it was that general relativity is a trustworthy theory of gravity. There's plenty of evidence that supports various predictions of GR which differ from Newtonian gravity, like the precession of the perihelion of Mercury's orbit, the gravitational lensing of light near stars and galaxies, and gravitational time dilation which can be measured at different altitudes on Earth (and it also needs to be taken into account when programming the clocks on board the orbiting GPS satellites). One of GR's predictions is that a sufficiently large collapsing star will form a black hole (another is that the universe must be either expanding or contracting, which lead to the Big Bang theory once redshift was observed). Black holes were theorized for a while, then in the last two decades they found observational evidence for a large number of likely black holes with telescopes. Most physicists believe general relativity's predictions will cease to be accurate at the "Planck scale" of very short distances and times and very high energy densities, and that at these scales it will need to be replaced by a quantum theory of gravity. So although they are fairly confident that GR is correct about large collapsing stars forming a black hole with an "event horizon" and a size proportional to its mass (given by the 'Swarzschild radius'), they think that the prediction of a singularity of infinite density at the center could be wrong, and that we'll need a theory of quantum gravity to understand what's really going on there. Jesse _________________________________________________________________ The average US Credit Score is 675. The cost to see yours: $0 by Experian. http://www.freecreditreport.com/pm/default.aspx?sc=660600&bcd=EMAILFOOTERAVERAGE --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~----------~----~----~----~------~----~------~--~---
