Give short one or two sentence answers Please write legibly

Give short (one or two sentence) answers. Please write legibly. How do we know what the (surface) temperature of the sun is? Can we use the same principle to determine the surface temperature of the moon? Why or why not? I have a box containing an ideal gas. I poke a hole in a side and molecules come streaming out. Is the velocity distribution of these escaping molecules Maxwellian? Why or why not? Does your car engine operate like an ideal (Carnot) engine? Why or why not?

Solution

(a) The temperature of the surface of the Sun can be determined in various
ways. We know how much energy we receive on Earth per unit time over a unit area facing the Sun. Then knowing the distance to the Sun, we can estimate total energy being emitted by the Sun. The total energy emitted per unit time per unit area is related to temperature in a known way. This can be used to find the Surface temperature of
the Sun. Sun is a gaseous sphere and it seems to be a stable object. Our existence tells us about the stability of the Sun. We think that gravity holds the Sun together. In that case the gas pressure must be enough to balance the gravitational force. We know the relation between gas pressure and temperature, this is then used to calculate the core temperature.

(b) No

Temperatures on the moon are extreme, ranging from boiling hot to freezing cold depending on where the sun is shining. There is no significant atmosphere on the moon, so it cannot trap heat or insulate the surface.