What does (1/√2)(Ψx − Ψy) represent?

[Nerdydude101]

I saw this the other day on a physics joke and i was wondering if anyone could tell me what it represents.

(1/√2)*(Ψ_x-Ψ_y)

(note: the x and y are just the values i put, the original values were labeled full and empty but i presume that has to do with the joke)

 

[TumblingDice]

The greek letter psi is use to express water potential. Hmm... Could it be a relationship for "glass half full/glass half empty" theme?

 

[Nerdydude101]

That was the joke yeah, I read that the Greek letter psi was used in quantum mechanics to describe wave functions and schrodingers superpositioning, I assumed te joke was about superpositioning because it would make the glass both half full and half empty (and so on including the other possible states) and I didn't know if maybe it was used to list all possible states of the glass (or at least the wanted ones under the circumstance for the joke)

 

[UltrafastPED]

(1/√2)*(Ψ_FULL-Ψ_EMPTY)

This version is definitely funny!

 

[TumblingDice]

That was the joke yeah, I read that the Greek letter psi was used in quantum mechanics to describe wave functions and schrodingers superpositioning, I assumed te joke was about superpositioning because it would make the glass both half full and half empty (and so on including the other possible states) and I didn't know if maybe it was used to list all possible states of the glass (or at least the wanted ones under the circumstance for the joke)

A glass can be half-full and half-empty at the same time classically without need for QM or superposition.

Could it refer to someone you can't tell will be optimistic or pessimistic about something until you 'measure' (or offer your own thoughts first)...? Was there more to the joke than just the formula?

EDIT: Just read Ultrafast's post. Obviously the formula says it all. Can someone please explain for me? TIA!