[net.space] Big Bang Source

KIRK.TYM@OFFICE-2.ARPA (04/13/84)

From:  Kirk Kelley  <KIRK.TYM@OFFICE-2.ARPA>

An interesting mapping onto the surface of an expanding (pitted) balloon are the
three spacial dimentions.  Time is the dimention at right angles to the surface.
 The pits are locations of mass.  Black holes make relatively deep pits.  
Concievably there might be some black holes that go all the way to the center of
the balloon (though no further).  I would expect to find the origin of a big 
bang somewhere near the center.

Assuming a cycling universe, what would the completed solid of all of spacetime 
look like?  Like a bowling ball with a few huge pits that represent the union of
the last black holes?

 -- modeler of nothing

cramer%ti-csl.csnet@csnet-relay.arpa (04/13/84)

From:      Nichael Cramer <cramer%ti-csl.csnet@csnet-relay.arpa>


> An interesting mapping onto the surface of an expanding (pitted) balloon are
> the three spacial dimentions.  Time is the dimention at right angles to the
> surface...  I would expect to find the origin of a big bang somewhere near
> the center...
>                -- modeler of nothing

	Your second point illustrates my point exactly.  i.e. that there is no
point IN the universe from which the primordial fireball expanded; keeping
in mind the important distinction that it is the two dimensional surface
that represents the model of expanding spacetime and not the interior space
enclosed by the ballon.  (In point of fact, the point in the center of the
balloon is 'inside' the balloon only because we poor creatures are trapped 
in 3-space, just as a point inside a circle appears to 'contained' by a 
circle to a flatlander, a point of view that looks naive to us.)
	HOWEVER, and more importantly, the first point you raise is precisely
the issue that prompted the original message.  The 2-space of the surface
of the expanding balloon does NOT represent our own 3-space (with one
suppressed dimension) expanding out through time.  Rather, it (with obvious
limitations) models an expanding spacetime with TWO dimensions suppressed.

mclean%NRL-CSS@sri-unix.UUCP (04/13/84)

From:  John McLean <mclean@NRL-CSS>



   I agree with Nichael Cramer that if SPACE is expanding it makes no
sense to ask where the big bang occurred.  However, if SPACETIME is expanding,
it makes just as little sense to ask when it occurred.  Nevertheless, it
seems to me that dates for the big bang are given.  How can this be?
                                                                   Thanks,
                                                                   John