From: posting-system@google.com Sent: Wednesday, January 23, 2002 10:18 AM To: brian@holtz.org Subject: Re: Can time go infinitely backward? Follow Up Flag: Follow up Flag Status: Flagged From: brian@holtz.org (Brian Holtz) Newsgroups: alt.atheism.moderated Subject: Re: Can time go infinitely backward? References: <3474f5fc.0201190825.4971df@posting.google.com> <62b769e4.0201201318.29b32670@posting.google.com> NNTP-Posting-Host: 12.236.1.8 Message-ID: <29c16047.0201231017.264d2b5a@posting.google.com> "Paul Holbach" wrote > Following Einstein, space and time can no longer be regarded as > absolute categories being independent of each other (as held by > Newton). We now know that space and time are joined together > inseparably as one spacetime continuum. You simply cannot have one > without the other. That appears to be the case in our universe, but it is not logically necessary. It is rather a consequence of the contingent fact that our universe is relativistic instead of Newtonian -- i.e., that the speed of light is a finite constant for any observer in an intertial reference frame, regardless of the relative motion of the light source. Our universe would be Newtonian if instead the speed of light varied for such observers. (Would the universe be Newtonian if the speed of light were infinite for all observers?) > If an infinite amount of time had already gone by up to now, there > wouldn´t be any possibility of timekeeping. [..] temporal intervals > would be absolutely incommensurable and there would be no sensible > measurement of time at all. There would be no possibility of keeping time relative to a first year, but it would still be possible to measure intervals before and after some arbitrary year. In fact, that is what our calendar does. > for in case there is not space and time but merely "fused", > continuous spacetime, there could only be time without a > beginning, if space had no origin, too. But today we know for > sure that space originated in the Big Bang and, accordingly, > time must have originated therein as well. Our timeline originated there, but it is not logically necessary that there could not have been events prior to (i.e. that could have influenced) the Big Bang. > if [a theist] approved to the contrary notion of time without > a beginning, he would unintentionally be postulating a necessarily > eternal space without origin in the same breath Only if relativity is logically necessary. It isn't. -- brian@holtz.org http://humanknowledge.net