king@dciem.UUCP (Stephen King) (05/31/85)
<>-<>-<>-<>-<>-<>-<>-<>-<>-<>-<> Rather than the universe expanding from some central point which is beyond our 3 dimensional existance, is it not more corerect to say that space itself is expanding? Isn't the distance between characters on this dislay getting greater all the time (although imperceptably)? I understand that not all galaxies are moving away from ours, in fact some are approaching at a considerable velocity. With regard to Ed Nather comments:- 4 dimensions? ... are you counting time? sjk
nather@utastro.UUCP (Ed Nather) (06/03/85)
> Rather than the universe expanding from some central point which is beyond > our 3 dimensional existance, is it not more correct to say that space > itself is expanding? Yes, it probably is, but you have to be careful about it ... > Isn't the distance between characters on this dislay > getting greater all the time (although imperceptably)? No. There's one of the problems. So long as systems are held together by a force acting to oppose Universal Expansion, they remain bound and do not partake of the expansion process. Your display screen is held together by molecular forces far stronger than the expansion of space could overcome; your terminal (and you) are held from expanding by the earth's gravity field, and the earth, sun, and the galaxy they are in are all gravitationally bound in a "local" group of galaxies. Only when you get beyond clusters of galaxies can Universal Expansion be perceived, and then only with difficulty. > I understand that > not all galaxies are moving away from ours, in fact some are approaching > at a considerable velocity. Depends what you mean by "considerable". A few close ones (Andromeda, for example) seem to be moving in our direction, but more probably they are orbiting a common central point and happen to have a component of that orbital velocity toward us, right now. All "blue shifts" noted for nearby galaxies are small compared with the velocities implied by the "red shifts" seen in *all* very distant galaxies and clusters of galaxies. > > With regard to Ed Nather comments:- 4 dimensions? ... are you counting time? > > sjk Spatially, no. There is an increasing suspicion that a number of puzzles might be solved if models of the Universe had more than 3 spatial dimensions -- the foreshortening of objects as they approach the speed of light, almost as if they were "turning" into a dimension we can't access; the puzzle of conjugate variables in Quantum Mechanics, as if they were perpindicular to each other, but employing a dimension apart for the recognized three spatial ones, etc. This is probably totally wrong and off the wall, but if it should turn out to be right, remember: you heard it here first! -- Ed Nather Astronony Dept, U of Texas @ Austin {allegra,ihnp4}!{noao,ut-sally}!utastro!nather nather%utastro.UTEXAS@ut-sally.ARPA