184 SOLUTIONS
where is the Stefan–Boltzmannconstant. Only afraction of
this flux reaches the Earth. In equilibrium this fraction equals the total
flux radiatedfrom theEarth at temperature So
From (S.4.73.2) weobtain
b) The radiation pressure on theEarth isgiven by
where is the ratio of the total fluxfrom the Sun to thefluxthat
reaches theEarth. Theradiationforce on the Earth
where is thecrosssection of theEarth.
c) For the small “chondrule” the temperature will be the same because it
depends only on the angle atwhich the Sun isseen and theradiationforce:
d) Using (S.4.73.3) anddenoting the meltingtemperature of themetallic
particle and the distance from the Sun we obtain