
Re: Time, bangs and quantum physics [was Re: Evidence for Big Bang]
William S. Lawson (lawson@ludwig.llnl.gov)
25 Apr 1995 15:35:19 GMT
In article <3nio13$d29@io.salford.ac.uk>, Mark Picton <m.picton@surveying.salford.ac.uk> writes:
> I suppose this is an old question but is time really a dimension? I mean
> our three spatial dimensions allow forwards and backwards travel but
> time can only really be measured in terms of events. Whereas, spatial
> dimensions can experienced directly time can only be measured indirectly
> with reference to events that have happened in our, subjective, past.
> [You can't measure the future!]
First off, time is a dimension even if you don't buy relativity. This is just
by applying the mathematical definition of a dimension. The qualitative
difference between time and space led to the assumption, unquestioned until
Einstein's time, that the two were independent in the sense that one could not
define a useful metric containing both space and time coordinates, i.e. space
and time don't mix. This simplifying assumption has proved incorrect, and the
qualitative difference between space and time traced (in part) to the unusual
character of the metric (its time component is negative). What this means is
that time and space are not independent, and that changing your state of motion
(mathematically similar to rotating yourself in three dimensions) mixes your
perceived time and space components. In this sense, time is not only a
dimension, but is inseparable from space.
 Bill Lawson
