Re: COLLISION 2

[brian whatcott <inet@INTELLISYS.NET>]

At 13:36 11/29/99 -0700, Jim wrote:

> >         A photon leaves the sun with h-nu of energy, travels through
> > space, strikes the surface of the earth and is absorbed by an atom.
> >
> > Questions:
> >         1) Didn't the internal energy of the sun decrease (change) by
> >            h-nu?
>
> I don't know how helpful it is to think of a "photon" as a real particle,
> but let's do for the nonce -- yes, something in the sun did work on this
> assumed particle and increased its energy and at the same time work was
> done on the sun to decrease the energy there.
>
> >         2) Didn't the internal energy of the earth increase (change) by
> >            h-nu?
>  As the "photon" collides with the Earth it does indeed do work on the
> Earth and the internal energy does indeed increase.///

> Jim Green

This is the clearest statement of Jim's position on heat vs work that I
have seen.

In considering the various gradations between conduction, convection and
radiation, I fancy Jim would see a hot plate in contact with a water
container as heating the water.

I reckon Jim might allow that if the contact method were to be replaced
by a gas flame playing hot air on the water pot, it would yet be heating
the water.

But if a 'heat' lamp replaces the gas flame or the hotplate, then it
seems this is not heating but working the water into boiling...
...because there is no physical contact with a higher temperature
reservoir.

 If this same heat lamp were placed beneath the water pot, and played
on a plate in contact with the pot, then the pot would be heated
even though the (radiatively heated) plate was worked.

I think I have it!

But wait: the metal base of the pot can serve as the radiative
absorber, so I suppose that the water can still be heated by the pot,
though the pot is worked by the heat lamp?




brian whatcott <inet@intellisys.net>
Altus OK