Not much of a mathematical Luddite let me rewrite the problem for you to make whats wrong with his answer clearer
x^0 = y^0
y^0 = x^0
Is x < y or is y < x ?????
Given x and y are representing time that is what we are checking is reversible.
Ask him to prove x is less than y from his proof which is what he has to be assuming.
To show him the problem set x = 3sec and y = 1sec. X comes before Y for him and so now time goes backwards to him
The fact he can't separate x from y is what he actually proved ... he scored an own goal
Even in the purest version of mathematics positive and negative is a convention not something that can be proved. One mans positive is another mans negative. I had ten dollars, when I give it to you I am -$10 but you are +$10 dollars. The plus/minus is totally point of view there is no absolute ... yeah relativity again.
If he is layman naive what he will do next is claim he measures time x before y so he will try to exclude your reversal of y and x
If he doesn't get it ask him to put his car in reverse and ask him to describe which way is forward and which is backwards using his maths. His forward will have all negative signs and so we can conclude forward means negative sign which wont work when actually driving forward. See the problem of using measurement to establish direction.
The connection between convention in maths and convention in physics reality is a very slippery slope even in high energy physics we have a thing called west coast and east coast convention because people took different points of view.
Disagreement about sign conventions is a frequent source of confusion, frustration, misunderstandings, and even outright errors in scientific work. In general, a sign convention is a special case of a choice of coordinate system for the case of one dimension.
Measuring time X coming before Y doesn't prove that it does it just establishes a convention based on your sign choice of how you saw it unfold, and certainly doesn't prove it can't be reversed.
There is no way into the problem with mathematics he can't even prove to me -1 is greater than 1, they are both one unit from any zero. We choose in some instances that 1 is greater than -1 by definition of number set order, it is not something you can prove. It like car driving direction is simply a convention based on how we usually see things.
