lew@ihuxr.UUCP (Lew Mammel, Jr.) (11/03/84)
These remarks are not aimed at justifying the existence of a "speed limit", but are an attempt to show the nature of its enforcement, so to speak, and to show that in many ways it doesn't defy the intuition as bluntly as it seems on first statement. Many people (e.g. Robert Heinlein) conceive of C as a "wall" which can be approached, like the sound barrier, but not broken through. Actually, it is possible, under relativity, to go as fast as you please, in the sense that you can gain arbitrarily large kinetic energy. An objects kinetic energy is measured by "gamma". Slow objects, that is objects travelling only a small fraction of the speed of light, have a value of gamma nearly equal to one. Objects travelling near the speed of light have gamma much greater than one. These are objects travelling at "ultrarelativistic" speeds, speeds equivalent to a classical velocity of many times the speed of light. You could say that displacement per unit time becomes a poor measure of intuitive speed in the ultrarelativistic region. A bullet with gamma equal 2000 won't get to the target much faster than one with gamma equal 100, but it will hit one hell of lot harder when it gets there! That's a good measure of speed, isn't it? Even light obeys this intuition. If you run away from it, it is red-shifted and becomes "soft" - you absorb much less energy from it. If you run into it, it hits you harder, just as would a classical stream of particles. Rather than banging your head against a wall that isn't there, try to develop an intuition in line with the theory. It's not impossible. Lew Mammel, Jr. ihnp4!ihuxr!lew
kpmartin@watmath.UUCP (Kevin Martin) (11/03/84)
>You could say that displacement per unit time becomes a poor measure of >intuitive speed in the ultrarelativistic region. A bullet with gamma >equal 2000 won't get to the target much faster than one with gamma equal >100, but it will hit one hell of lot harder when it gets there! > Lew Mammel, Jr. ihnp4!ihuxr!lew Unless you are riding the bullet, in which case you only have to go 1/20th as far on the faster bullet due to space contraction, so it takes only 1/20th as long (give or take the difference between .9999*c and .9998*c or whatever).
bill@utastro.UUCP (William H. Jefferys) (11/08/84)
The fact that C is the limiting velocity ic a consequence of the
fact that any inertial observer measures the same value for C,
coupled with some very general ideas regarding the homogeneity
of space and time. Others have presented discussions of this so
I will not pursue this. BUT...
I have recently bought an excellent book, "Relativity Visualized",
by Lewis C. Epstein (must be ordered direct from the publisher,
Insight Press, 614 Vermont St., San Francisco CA 94107). It takes
a very intuitive, geometrical approach to both special and general
relativity, and has some unique discussions that are as clear and
easy to understand as any I have seen in the non-technical
area. I strongly recommend it to nonphysicists who would like
to understand the basic ideas of relativity better.
Epstein is also the author of "Thinking Physics", available from
the same publisher, a collection of challenging problems in
basic physics, mostly nonmathematical but intended to help
elementary physics students sharpen their physical intuition.
Some of them will even trip up the unwary expert. This one
is also strongly recommended.
--
"When evolution is outlawed, only outlaws will evolve"
Bill Jefferys 8-%
Astronomy Dept, University of Texas, Austin TX 78712 (USnail)
{allegra,ihnp4}!{ut-sally,noao}!utastro!bill (uucp)
bill%utastro.UTEXAS@ut-sally.ARPA (ARPANET)herbie@watdcsu.UUCP (Herb Chong, Computing Services) (11/10/84)
Spacetime Physics by Taylor and Wheeler is also a good book, but only
if you want to know some of the mathematical details. There are over
100 excercises with solutions. Many of the classic paradoxes are
used as examples and problems.
Herb Chong...
I'm user-friendly -- I don't byte, I nybble....
UUCP: {decvax|utzoo|ihnp4|allegra|clyde}!watmath!watdcsu!herbie
CSNET: herbie%watdcsu@waterloo.csnet
ARPA: herbie%watdcsu%waterloo.csnet@csnet-relay.arpa
NETNORTH, BITNET: herbie@watdcs, herbie@watdcsustan@sdcsvax.UUCP (Stan Tomlinson) (11/14/84)
The speed of light:
Not only a good idea,
Its the Law!
Stan Tomlinson
sdcsvax!stan
(take your 55 and ...)ian@ic-cs.UUCP (Ian W. Moor) (11/16/84)
Doesn't this belong in net.lang.C ? :-)
--
Ian W. Moor {mcvax,vax135}!ukc!west44!ic-cs!im
Dept of Computing
Imperial College "The squire on a hippopotamus is equal to
180 Queen's Gate the son of the other two squires"
London SW7 2BZleon@hhb.UUCP (Leon Gordon) (12/01/84)
I haven't had time to follow this discussion much, but has
anyone posted the following limerick? (I think it originally appeared
in Physics Today):
There was a young lady named Bright
Who could travel much faster than light;
She set out one day in a relative way,
And returned on the previous night!
leon
{decvax,ihnp4,allegra}!philabs!hhb!leonherbie@watdcsu.UUCP (Herb Chong, Computing Services) (12/04/84)
I just finished reading a biography of Einstein and since I don't have it handy, I can't remember who, but it was attributed to one of his colleagues who happened to like limericks. I seem to recall that he was an Englishman. Anyway, the important thing is that it dates from the '20's. Herb...