# Schroedinger Cat (Homework 10-325)

3. Explain the Schrodinger’s Cat paradox as if you were talking to

a) someone with some knowledge of quantum mechanics, e.g. at the level of Phys 324.

b) someone with an interest in quantum mechanics but no formal background.

c) yourself.

a)
For someone that does know quantum mechanics I would explain
Imagine you have a cat in a sealed box together with tiny amount of radioactive material. In one hour this material could decay once or not. If the decay occurs though a Geiger counter it triggers a macroscopic mechanism that kills the cat.

You let the cat alive in the box and after one hour you come back. You do not know how is the cat inside (alive or dead) until you do not peek in the box window to see this. So that when you return the cat is in a mix of states:

$Ψ_cat=(1/√2)(ψ_{alive}+ψ_{dead})$

The fact that you peek in the window constitutes the measurement and forces the wave function to collapse in a precise eigenfunction and the cat to be or dead or alive.  Can this be true? (The fact that the person that is peeking to see that state of the cat is the one that determines if the cat lives or dies?) Evidently not.

b)

For someone that does not know quantum mechanics I would say

When you return to peek in the box the cat is half dead and half alive. Can this happen in the real world? Evidently not.

c)

To me

The paradox of the Schrodinger cat comes from the applications of quantum mechanics law to the macroscopic world. Is this possible? Quantum mechanics fails when applied to macroscopic world because a large object never can be described by a linear combination of all of its constituents (all its atoms for example).  Can a macroscopic object be described as being in a quantum “mix” of states? Evidently not.