Thermodynamics, Statistical Physics, and Quantum Mechanics

THERMODYNAMICS AND STATISTICAL PHYSICS 35

4.73 Radiation Force (Princeton, Moscow Phys-Tech,

MIT)

Consider an idealized Sun and Earth, both blackbodies, in otherwise empty
flat space. The Sun is at a temperature and heattransfer by
oceans and atmosphere on the Earth is so effective as to keep the Earth’s
surface temperature uniform. The radius of the Earth is
the radius of the Sun is and the Earth–Sun distance is
The mass of Sun

a)

b)

c)

d)

Find the temperature of the Earth.

Find the radiation force on the Earth.

Compare these results with those for an interplanetary “chondrule” in

the form of aspherical,perfectly conductingblackbodywith a radius

cm, moving in a circular orbit around the Sun at a radius

equal to the Earth–Sun distance

At what distance from the Sun would a metallic particle melt (melting

temperature

For what size particle would the radiation forcecalculated in (c) be

equal to the gravitationalforce from the Sun at adistance?

4.74 Hot Box and Particle Creation (Boston, MIT)

The electromagneticradiation in a box of volumeVcan be treated as a

noninteractingideal Bose gas of photons. If the cavity also contains atoms

capable of absorbing and emitting photons, the number of photons in the

cavity is notdefinite. The box iscomposed of a specialmaterial that can

withstand extremely high temperatures oforder

e)