🚀 go-pugleaf

In article <1992Nov06.211115.134895@watson.ibm.com>, lucas@watson.ibm.com (Bruce D. Lucas) writes...
>How do we know space is three-dimensional, or space-time
>four-dimensional?  Is there a simple experiment one can do to
>determine the dimensionality of space or of space-time?

How many mutually perpendicular rulers can you affix to a single pivot?
After you have attached three of them, you won't have room for a fourth.
So space is three dimensional.  (Of course, if you worry about
General Relativity then you have to deal with the fact that it is curved
as well...)

Spacetime is four-dimensional because we add one dimension of time to 
three dimensions of space.  How do I know that time is one-dimensional?
I'm not sure.  It certainly is a good working hypothesis until someone
shows me how to move perpendicularly to the normal flow of time. :=)

-Scott
--------------------
Scott I. Chase			"It is not a simple life to be a single cell,
SICHASE@CSA2.LBL.GOV		 although I have no right to say so, having
				 been a single cell so long ago myself that I 
				 have no memory at all of that stage of my 
				 life." - Lewis Thomas