How to Avoid Breaking Physics With Your “What If” Question

We get a lot of “what if” questions here on Physics Forums. This article will explore three different types and then some suggestions for students who feel their question may fall into one of those types.

“what if” questions that contradict physics as we know it
“what if” questions that are themselves self-contradictory
“what if” questions that can be answered but with some difficulty
suggestions for the student

“What If” Questions That Contradict Physics as We Know It
 
Often here on the Physics Forum, people ask questions that, unrealized by them, amount to being exactly “if the laws of physics don’t apply, what do the laws of physics say about ?”.
Sometimes this is just because of a poorly formulated question. For example, if someone asks “what would happen to the Earth if the sun were to suddenly disappear”, it could well be that what they are really want to know is “does the gravity of the sun affect the Earth instantaneously”. The first question is problematic because it...