[meteorite-list] Speed-of-light question

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Wed, 26 Aug 2009 00:50:51 -0500
Message-ID: <F39C9FD0A75E4B2FBD038D3D1B1EF31D_at_ATARIENGINE2>

Hi, All,

Speaking to this thread, and all the people who
find this sort of thing fun, there are many other
relativity brain teasers you can tease your brain
with... Like this one:

<QUOTE>

    Consider the admittedly unrealistic situation
of a man carrying horizontally a 20-ft pole and
wanting to get it into a 10-ft garage. He will run at
speed v = 0.866c to make ? = 2, so that the pole
contracts to 10 ft. It will be well to insist on having a
sufficiently massive block of concrete at the back
of the garage, so that there is no question of whether
the pole finally stops in the inertial frame of the
garage, or vice versa.

    So the man runs with his (now contracted) pole
into the garage and a friend quickly closes the door.
In principle we do not doubt the feasibility of this
experiment; that is, the reality of length contraction.
When the pole stops in the rest-frame of the garage,
it will tend to assume, if it can, its original length
relative to the garage. Thus, if it survived the impact,
it must now either bend, or burst the door, or remain
compressed.

    At this point a paradox might occur to the reader:
What about the symmetry of the phenomenon?
Relative to the runner, won?t the garage be only 5 ft
long? And, if so, how can the 20-ft pole get into the
5-ft garage? Very well, let us consider what happens...

<UNQUOTE>

from Wolfgang Rindler's "Relativity," probably
the best and clearest book on the subject ever
written. It contains a lot of brain teasers and
it is downloadable at:
http://avaxhome.ws/ebooks/science_books/astronomy_cosmology/relativity_special_general_and_cosmological.html

And the answer? I won't spoil it, but you can get the
20-foot pole into the 5-foot garage easily, no problemo.
and with room to spare! (p. 63)



Sterling K. Webb
----------------------------------------------------------------------
----- Original Message -----
From: "Mexicodoug" <mexicodoug at aim.com>
To: <mojave_meteorites at cox.net>
Cc: <Meteorite-list at meteoritecentral.com>
Sent: Tuesday, August 25, 2009 11:44 PM
Subject: Re: [meteorite-list] Speed-of-light question


> Oh one of these Gamow deals ... lets see, is it:
>
> 0.707106781....times the speed of light (dividing by the square root
> of two to cancel out the dilution of someone watching you, who thinks
> you have traveled at 6.18... years?)?
>
> The "..." because exactly is a pretty strong statement and I am
> keyboard challenged to write (1/(sqrt(2))*c since the parentheses get
> confusing.
>
> Best wishes, Doug
>
>
>
> -----Original Message-----
> From: Rob Matson <mojave_meteorites at cox.net>
> To: Meteorites USA <eric at meteoritesusa.com>
> Cc: meteorite-list at meteoritecentral.com
> Sent: Tue, Aug 25, 2009 11:56 pm
> Subject: [meteorite-list] Speed-of-light question
>
>
>
> Hi Eric and List,
>
>> Light itself travels 186,000 miles per second. Do most people
>> really understand how fast that truly is? Do people realize
>> how long it would take to travel ANYWHERE in our universe?
>
> At the speed of light, you can actually travel anywhere in the
> universe *instantaneously* -- from your own reckoning of time.
> Which brings up a special relativity question for you all: at
> what velocity must you travel in order to reach Alpha Centauri
> (4.37 light-years away) in exactly 4.37 years -- by *your*
> reckoning of time?
>
> --Rob
>
>
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Received on Wed 26 Aug 2009 01:50:51 AM PDT