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Re: a relativity question



Does not a photon change mass/energy/wavelength/color as it climbs the
gravitational potential hill of the earth?

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor
----- Original Message -----
From: "John Mallinckrodt" <ajm@CSUPOMONA.EDU>
To: <PHYS-L@lists.nau.edu>
Sent: Monday, November 25, 2002 9:49 PM
Subject: Re: a relativity question


| >A question in Giancolli asks: Is a compressed spring more massive than
the
| >relaxed version of the spring.
| >
| >I understand that Work has been done and there is no change of KE.
| >Classically we say there is now PE stored. But it seems that to conserve
| >energy in the relativistic sense that there would be added mass ...
|
| Yes
|
| >... measured.
|
| Unlikely!
|
| >If so, I wonder if the same would be said of an elevated mass?
|
| No; an elevated mass does not "have" more energy despite the
| implications of standard textbooks (and not to mention the usefulness
| of that gentle subterfuge in many common situations.) Gravitational
| potential energy is a property of a *system* of interacting masses.
|
| For instance, consider the system consisting of the Earth and all of
| its immediate neighboring objects including my car, Martha Stewart,
| and the ionosphere. If you reach in from outer space, lift my car
| some distance, and then remove your (lengthy!) arm safely back into
| the cosmos, the rest energy of the system--and, therefore, its
| mass--has been increased. My car's mass may also have changed (as a
| result, perhaps, of heat conducted to or from your hand while
| lifting), but not because of the energy of interaction between it and
| the Earth.
|
| --
| John Mallinckrodt mailto:ajm@csupomona.edu
| Cal Poly Pomona http://www.csupomona.edu/~ajm
|
| This posting is the position of the writer, not that of SUNY-BSC, NAU or
the AAPT.


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This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.