2020年GeCAA理论第2题-地平论

英文题目

2 Flat Earth (10 points)

A new model of the world is gaining in popularity among some people. These people believe in the “Flat Earth” view of the world, where the Earth is not a spheroid, but rather a circle with radius $$R_⊕$$. The central axis of the Earth (normal to the circle passing through its centre C) is passes through the observer’s zenith. This model must at least remain consistent with the observed phenomena, as listed below:

• The value of the solar constant is $$S_⊙ = 1366W/m^2$$.

• The Earth’s central axis precesses in a circle with a period 25800 years.

• The radius of the precession circle is 23.5°.

We assume that the Earth is a perfect blackbody radiator and the Sun is sufficiently far away that all sun rays are parallel. Let us also assume that the Sun’s current (initial) location is at the zenith.

Determine how many years it will take for the Earth’s equilibrium temperature to decrease by 1 °C.