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GRED: Twirling pole paradox

Posted: Wed Jun 02, 2010 3:18 pm
by RJN
Guess the Result of the Experiment of the Day (GRED): The Twirling Pole Paradox

You hold a really long pole -- for example one light year long. You are out in space. You hold one end of this pole firmly to your stomach with the pole pointing out, and then you spin around in a circle. Therefore the free end of the pole makes a complete circle, with you at the center of the circle. Say it takes you 10 seconds to do this. Does the speed of the free end go faster than the speed of light?

Please do NOT post any answers or comments with spoilers here. Answers and comments with spoilers are encouraged in GRED Answer post here: http://asterisk.apod.com/vie ... 30&t=19643 . Please check back there later -- what I believe to be the correct answer will be posted there a few days after this initial post.

Comments or questions here -- without spoilers -- are OK. In particular, questions about the experimental setup are OK.

Re: GRED: Twirling pole paradox

Posted: Thu Jun 03, 2010 8:00 pm
by Nancy Lou
I'm a professional musician and educator. I LOVE these questions that I find on APOD. Sometimes, I even may have the answer correct!
Thank you for helping to keep my old brain sharp!
:D

Re: GRED: Twirling pole paradox

Posted: Thu Jun 03, 2010 9:16 pm
by Jay Mack
The poser does not specify the speed of light in relation to what. Speed is relative.

Re: GRED: Twirling pole paradox

Posted: Thu Jun 03, 2010 9:23 pm
by Beta
Jay Mack wrote:The poser does not specify the speed of light in relation to what. Speed is relative.
Actually, the speed of light is the one speed that isn't relative.

Re: GRED: Twirling pole paradox

Posted: Thu Jun 03, 2010 10:21 pm
by Nurse Mike
Can we assume the pole is a "standard" pole, or does it have infinite rigidity?

Re: GRED: Twirling pole paradox

Posted: Thu Jun 03, 2010 10:51 pm
by Einstien
The question doesn't seem to make sense.
If it is given that it took 10 seconds to spin around, the pole must have moved in a 1-lt-yr arc. (That's C = pi*D = pi*2-lt-yr) That's pretty fast!
If this is given, then the pole spun around and did not break and made the arc. Given.

Answer a) asks if it doesn't violate any laws....wha?! Of course it does, so this must be wrong.
Answer b) states that the pole can't go faster than the speed of light...which it can't...but, IT JUST DID in the given part of the problem!..so this must be wrong.
Answer c) is correct by the process of elimination.

Re: GRED: Twirling pole paradox

Posted: Thu Jun 03, 2010 10:52 pm
by RJN
Nurse Mike wrote:Can we assume the pole is a "standard" pole, or does it have infinite rigidity?
Assume the pole is made of a very sturdy solid material.

Re: GRED: Twirling pole paradox

Posted: Fri Jun 04, 2010 1:58 pm
by jman
It's a Festivus Pole. Very high strength-to-weight ratio