## The Concept of Zero

Here's what I have now.

A universal physical constant is something that is universal in nature and constant in time. Speed of light is one such constant. No matter what part of the universe you take it from at any point in time, it will always be the same. So assuming that subtracting the speed of light from the speed of light is possible (which I cannot see any reason why you wouldn't be able to), it would indeed be zero.

As such, anything that is affected by the speed of light and/or any other universal constant can reach zero also. Since everything effects everything in the end, zero is an attainable value.

Thank you all for putting up with me. I can now sleep a little better at night with this question cleared up.

As a side note, the apple question doesn't work because "apple" is not a universal constant. In chiro's example, it's trying to define it as a universal constant when it isn't, unless you were trying to make those apples represent a universal constant.

Edit: After re-reading the question, making those apples represent a universal constant was exactly what you were doing, although in a pretty confusing way. My apologies.