Quote:
Originally Posted by sjastro
Time is not a spatial variable.
I think the confusion arises from Special Relativity.
The metric for distance between 2 points in 3-D flat space is
ds2=dx2+dy2+dz2.
In space-time the metric is
ds2=c2dt2-dx2-dy2-dz2 (c is the speed of light.)
ds2 is still a spatial property, but since t is now in the equation it is easy to think of t as spatial.
Steven
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So that website I linked to that asserts
Quote:
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"If we want to count time as a dimension, then we should say that we live in a four dimensional space-time that is curved into the 5th dimension! So where is this "different direction"?"
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is just plain wrong?
It looks like the author is trying to get a grip on the curve by basically stating that the curve exists into the fourth dimension and the projection of the four dimensional space onto the 3rd dimension is the flat space we all know. I think that this is incorrect (happy to be shown I'm wrong though - because its nice and easy to understand!)