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more on Brian Greene: That Famous Equation and You
From: David Farber <dave () farber net>
Date: Fri, 30 Sep 2005 17:40:31 -0400
Begin forwarded message: From: Vadim Antonov <avg () kotovnik com> Date: September 30, 2005 5:26:49 PM EDT To: David Farber <dave () farber net> Subject: Re: [IP] more on Brian Greene: That Famous Equation and You
From: Brian Sniffen <bts () alum mit edu> Date: September 30, 2005 2:22:46 PM EDTAlas, the above are common misconceptions that bear correcting. When one burns gasoline, one doesn't convert any of its mass into energy.This certainly does involve a change in mass.
That is absolutely correct.
It's the equivalent of allowing an anvil to descend from the top of a building to the bottom, and using a rope attached to the anvil to turn a shaft or do other work as it falls. The anvil has precisely the same mass at the bottom as it did at the top; it merely has less gravitational potential energy because it is closer to the center of the Earth. A similar process occurs on a molecular level when a battery is discharged or gasoline is burned.I *think*, but am less certain, that a dropping anvil also exhibits a change in mass. You'd need to drop an awfully big anvil an awfully long way to be able to measure it, though. That anvil's falling deeper into a gravity well, so the potential energy has to go *somewhere*. It goes into rest mass.
The real answer is: the kinetic energy of moving things is stored in the relativistic icrease of mass (M=m/sqrt(1-v**2/c**2) where M is the relativistic mass, and m is rest mass). When anvil crashes down, it transfers its kinetic energy to the kinetic energy of heat motion in itself and the surface material. Enegry and the relativistic mass is one and the same. The physical nature of the gravitational potential energry is not yetunderstood, given the absense of a grand unified theory (potential energy of non-gravitational interactions is, basically, equivalent to the mass of the paricles mediating the corresponding force (aka gauge bosons). In case of strong force, pulling apart two bound quarks would eventually result in
conversion of the potential energy into a new pair quark/antiquark, thus "snapping" the stretched tube of color charge). --vadim ------------------------------------- You are subscribed as lists-ip () insecure org To manage your subscription, go to http://v2.listbox.com/member/?listname=ip Archives at: http://www.interesting-people.org/archives/interesting-people/
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- more on Brian Greene: That Famous Equation and You David Farber (Sep 30)