A simple metric explanation
(This post has the theme to "Mission: Impossible" running in the background.)
I am currently having an e-conversation with someone who thinks Special Relativity is incorrect. I have no problem discussing this with this person, though I support Special Relativity based on the evidence, however it seems his Math background is a bit lacking.
The problem is this. I worked out a metric for his theory so I could compare it with the Minkowski metric. I then pointed out to him that his metric is variable and depends on the relative velocity of the reference frame with respect to his aether frame. His response? What's a metric?
I've apparently spent too much time doing "Physics Math." I can't come up with a simple description for what a metric is. Could someone please give me an explanation of what a metric is that would be understood by someone who (apparently) knows nothing beyond vector addition and intro Calculus?