679: Christmas Plans
Title text: Physicists who want to protect traditional Christmas realize that the only way to keep from changing Christmas is not to observe it.
This comic centers around a joke about Quantum Entanglement in physics - if you don't observe something, it has all possible states, not a specific one. It is a double-entendre with the word observe meaning both "look at" (physics sense) and "celebrate" (a holiday). One of the most famous examples on this is the Schrödinger's cat paradoxon.
The title text refers to another principle in physics where the act of measuring something must also change it in some way. If one drops a thermometer into into a mug of water, energy spent (or released) when heating (or cooling) the mercury in the thermometer changes the temperature of the water in the mug by a small amount. The only way not to interfere with the temperature of the water in the mug is not to measure it.
- [Cueball is standing behind a friend, who is sitting at a computer.]
- Cueball: Hey, will you be in town the day after Christmas?
- Friend: Couldn't say—
- Friend: I'm Jewish.
- Cueball: But... how does being Jewish keep you from knowing your plans?
- Friend: I know my plans—
- Friend: I just don't know when Christmas is.
- Cueball: Really? Why not look it up?
- Friend: Well, I'm also a physicist.
- Cueball: So?
- Friend: I believe that since I don't observe Christmas, it can't have a definite date.