From: MC elover (mcelover@yahoo.com)
Date: Sun Feb 03 2002 - 10:23:19 PST
Message-ID: <20020203182319.9788.qmail@web10906.mail.yahoo.com> Date: Sun, 3 Feb 2002 10:23:19 -0800 (PST) From: MC elover <mcelover@yahoo.com> Subject: relativity and light
hey all
relativity is such a great subject to dabble in. kids
always come up with such creative and worthwhile
questions. here's one that stumped me:
during our discussion of the twin paradox--where the
stay on earth twin ages more than the space travelling
twin--we all agreed that the acceleration of the
travelling twin was the source of the paradox and that
his perspective couldnt be trusted be trusted as an
inertial frame of reference. that was all good. The
question ususally arises about what would happen if
the travelling twin actually travelled at the speed of
light. we again agreed, this time that the travelling
twin wouldnt age at all relative to his earthbound
twin, EXCEPT when he was slowing down to turn around.
THEN one bright student asked me what would happen if
we sent a beam of light on a round trip, say by
bouncing it off of a mirror on a distant planet.
specifically, he wanted to know if light can
ACCELERATE. that is, when the light hits the mirror,
it's got to slow down and stop and then speed up in
the other direction. all this will take some time
from our perspective since the light wouldnt be
travelling at the speed of light. this brings up a
bunch of issues: what the heck happens when light
bounces off of a metallic surface like a mirror? what
about a non-metallic surface? also, how much time,
relative to us, does it take a beam of light to bounce
off of something?
one last thing: i've been working for a while on
trying to make an analogy between the cars driving on
fell street and photons in a beam of light. since the
traffic lights are timed, the flow of traffic is
confined to the speed limit, but individual cars might
go faster or slower as they move around in the
traffic. does this jive with anyone?
with funky handshake
-eric
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