tag:blogger.com,1999:blog-10944560.post114107764426066586..comments2024-01-01T08:18:36.278-05:00Comments on Real Physics: Inflationary DifficultiesLawrence Gagehttp://www.blogger.com/profile/01242322119143922513noreply@blogger.comBlogger6125tag:blogger.com,1999:blog-10944560.post-1143038493157274032006-03-22T09:41:00.000-05:002006-03-22T09:41:00.000-05:00No, I'm saying you're "comparing apples to oranges...No, I'm saying you're "comparing apples to oranges." The universe is so entirely different from a black hole that the analogy you're trying to use doesn't fit. Most significantly, the universe doesn't have anything to "escape" into. Perhaps more immediately preceivable: in a black hole the only direction you can travel is down, whereas clearly you can travel in every direction in the universe.<BR/><BR/>LGLawrence Gagehttps://www.blogger.com/profile/01242322119143922513noreply@blogger.comtag:blogger.com,1999:blog-10944560.post-1142638490707639592006-03-17T18:34:00.000-05:002006-03-17T18:34:00.000-05:00So you're saying that space, as well as everything...So you're saying that space, as well as everything else was expanding at the same time so there was no contradiction?Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-10944560.post-1142631394349322542006-03-17T16:36:00.000-05:002006-03-17T16:36:00.000-05:00I'm not sure why you two think the universe starte...I'm not sure why you two think the universe started as "a black hole": perhaps the word "horizon" reminds you of the event horizon of black-hole fame?<BR/><BR/>The general relativistic metric (the mathematical form that describes how spacetime bends) for a black hole is significantly different from that for the universe. I'm not a relativist, but perhaps it's not too far off to put it in these terms:<BR/><BR/>black hole = mass within event horizon surrounded by space<BR/><BR/>universe = mass not surrounded by anything at all (that is, not embedded in a larger space)<BR/><BR/>The "big bang" is the initial impetus that caused the expansion. As Guth himself says, inflation isn't necessary for the initial expansive motion. The term "big bang" is unfortunate; it was devised by opponents of the theory and makes it sound like an explosion into a larger space, but it was probably more like an opening flower or matter falling upward, so to speak: a natural, non-violent motion. (The metaphors fall short because there's really nothing that's a very exact comparison to "the sum total of all physical interacting things," that is, the universe.) The universe doesn't have to worry about climbing out of an event horizon, because it's the space itself within its horizon that is expanding: the "boundary" of the universe simply gets bigger as it expands.<BR/><BR/>I hope that's helpful.<BR/><BR/>Steve, Guth says on the same page of the book that the theories with and without inflation describe indentical cosmic radii for all times after 10^-35 seconds. In brief, inflation makes only the smallest fraction of a second of difference in cosmic age, certainly well within the uncertainties of its measurement.<BR/><BR/>LGLawrence Gagehttps://www.blogger.com/profile/01242322119143922513noreply@blogger.comtag:blogger.com,1999:blog-10944560.post-1142629018303221582006-03-17T15:56:00.000-05:002006-03-17T15:56:00.000-05:00Jon said,"Maybe you could explain something to me:...Jon said,<BR/><BR/>"Maybe you could explain something to me: If the universe essentially started out as a massive black hole and the escape velocity of a black hole is greater than the speed of light then how did the universe start seeing that nothing can go faster than the speed of light?"<BR/><BR/>It's funny you say that! I was lying in bed last night pondering the same thing after reading LG's post on Cosmic Inflation. I don't fully understand the technical problems with the Big Bang that lead to Inflation Theory, but it did get me thinking that without the exponential growth in size/speed the whole thing would not even escape itself in the first micro second. The density of the entire universe wrapped up in the head of a pin would be the mother of all black holes. <BR/><BR/>Now this has me thinking, if the inflation increased in the order of X to the power of 50 or more, even for a few seconds, how many years do we need to subtract from our existing 15,000,000,000 estimated years since detonation.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-10944560.post-1142605960397395322006-03-17T09:32:00.000-05:002006-03-17T09:32:00.000-05:00Where did you hear that the universe started essen...Where did you hear that the universe started essentially as a (massive) black hole? From my understanding, that's a rather poetic use of the term "black hole."<BR/><BR/>LGLawrence Gagehttps://www.blogger.com/profile/01242322119143922513noreply@blogger.comtag:blogger.com,1999:blog-10944560.post-1142550786115382632006-03-16T18:13:00.000-05:002006-03-16T18:13:00.000-05:00Maybe you could explain something to me: If the un...Maybe you could explain something to me: If the universe essentially started out as a massive black hole and the escape velocity of a black hole is greater than the speed of light then how did the universe start seeing that nothing can go faster than the speed of light?Anonymousnoreply@blogger.com