king@dciem.UUCP (Stephen King) (10/16/86)
O~~~~~~~~~~O I have just finished reading Carl Sagan's novel *Contact* and must say that I enjoyed it very much. I do have some questions for anybody in the know: 1) I have heard of wormholes (the means used for travel at velocities >c in the novel), but always thought that they were just the result of informed speculation. Do they (or could they) really exist? 2) What are the differences between wormholes and black holes? 3) I understand that Stephen Hawking has established a means whereby black holes can 'evapourate' through the emission of large scale gravity waves, smaller black holes being almost explosive through this mechanism. How, then, could mini black holes have hung around since the Big Bang? 4) Can causality really be violated in the immediate vicinity of a black hole (or beyond the event horizon)? * Looking forward to a trip to Vega sjk ...utzoo!dciem!king * I am not a fiction author. * don't expect my employer to accept responsibility for any * of these wild speculations or highly biased opinions.
kilcup@batcomputer.TN.CORNELL.EDU (Greg Kilcup) (10/23/86)
In reference to Stephen King's queries about wormholes: Kip Thorne (an astrophysist at Caltech) was at Cornell a couple of weeks ago, and gave a colloqium (introduced by none other than Carl "BILLyuns and BILLyuns" Sagan) at which he explained that: --> The original wormhole is a bizarre but valid solution of the Einstein equations in the absence of matter, which in principle allows the universe to be multiply connected for a time. That is, two distant places in the universe may be temporarily connected by a shortcut through hyperspace. --> In practice, they are actually useless for getting from one place to another. Firstly, wormholes are dynamic solutions, and disappear before anyone can even in principle travel through one. Furthermore, such solutions are very unstable, and in the presence of even the slightest background radiation, wormholes will not even form. For this reason, one believes that wormholes do not naturally form. --> However, when finishing the novel, Sagan called Thorne, asking if there was any possible way to form a wormhole, given a sufficiently advanced technology. After some thought, Thorne found that if one could somehow create an incredible tension (many orders of magnitude greater than that required to tear a nucleus apart, for example), then there is another bizarre, and STATIC wormhole solution to Einstein's equations. Of course we have no idea how to create such a tension--- in particular ordinary matter won't do---but there is no (known) reason rule out the idea. Thorne has apparently produced an undergraduate level writeup, which will soon appear in The American Physicist (if it hasn't already). -- Greg Kilcup (kilcup@lnssun2.tn.cornell.edu) Newman Labatory of Nuclear Studies Cornell University ARPA: kilcup@lnssun2.tn.cornell.edu