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Groundrules

Note that this site is a service for "laymen", not a consulting service for highly technical questions. There are some ground rules. Please

submit single, concise, well-focused questions;
do not use "the Physicist" to do your homework;
in the same vein, do not ask me to help you with homework since this is not a tutoring site;
do not ask about technical details which could be related to bombs or other weapons;
if you don't like my answer, don't try to pursue a debate with me—I do not wish to nor do I have the time to critique your personal theory of the universe!
I no longer answer questions which are based on premises like: "...if we could travel faster than the speed of light..." or "...ignoring the fact that nothing can go faster than the speed of light...", "…if I were traveling at the speed of light…, etc.
Please refrain from asking questions which include phrases like: "perfectly stiff", "infinite energy source", "perfectly reflective surface", etc. It is usually not possible to give good answers to questions based on unphysical assumptions.