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comment If action equals reaction, how is it ever possible to win in martial arts?
I'm definitely no expert on martial arts, but it seems to me that at least part of the answer should involve balance — if you knock me sufficiently off balance, not only will I feel the force of your blow on me, but shortly afterwards I might be feeling the force of the ground rushing up to greet me. Even if I manage to refrain from falling, knocking me off balance could then feed back into the ability to hit strategic target points.
comment How can contact binaries persist?
Is there any literature that calculates their expected life expectancy? I realize such calculations would require a definition of "contact" which might be somewhat fuzzy in this case, but I don't see that stopping theoretical astrophysicists…
comment What is the wave in an electron?
Exactly this. From "an electron is the elementary excitation of the electron field"
comment Is it possible to counter-act centrifugal force by moving at the same speed in the anti-spin direction?
"neglecting its acceleration due to air friction" - also ignoring frame dragging, the effect of which would be much, much smaller than air friction:
comment How viable is reuse of nuclear waste at this point, and what are future prospects?
I'm also confused as to why this was closed. Is it because of the social aspect, or because he's asking more of an engineering question than a physics question? The core question, as I understand it, it "What is the current state-of-the-art in terms of waste handling, and can it be reasonably expected that underground deposition of nuclear waste can be eliminated altogether in the foreseeable future?"
comment A fan in a hot room at what point does it put in more energy that it dissipates
@Vintage: Another good point. I'll edit my answer to include the points that you and Mitchell have made.
comment Does hot air really rise?
With respect to water, the temperature at which warm water becomes less dense than cold is 4° C.
comment A fan in a hot room at what point does it put in more energy that it dissipates
@Mitchell: Excellent point
comment Is the entire Universe the same age?
@Ted Bunn: Nice addition. I question your last paragraph, though. Wouldn't general relativistic effects make that not true, since time flows slower in a gravitational field? (As an extreme case, consider the adventures of an observer near the event horizon of a black hole who can manage to watch the universe age billions of years while mere minutes elapse for himself.)