earth-sun distance and heat involved

(Beto) writes:

According to my calculations, the difference between the longest
distance from earth to the sun and the shorstest one are about 4.8
millions of kilometers.

Why the temperature doesn't drastically change because of this?

Because the distance only varies by a few percent.


If this is because of radiation doesn't being too important this far
from the sun,

Uh --- just what _do_ you think heats the Earth, then ??? ,:-I


Where can I find a equation which relates radiation with distance?

Look up "Inverse Square Law." If you halve the distance, you quadruple the
radiant flux. For small changes in distance, the percent change in radiant
flux is twice the percent change in distance. However, this is offset by
the fact that re-radiation to space goes as the _fourth_ power of temperature,
so the percent change in temperature is only 1/4 the percent change in the
incoming radiant flux.

The reason why you don't notice the effect of the Earth's varying distance
from the Sun is that the temperature changes due to axial tilt (AKA "seasons")
are so much larger than the changes due to distance from the Sun. Also, there
are these things called "oceans" that act as huge heat sinks, moderating
changes in temperature.

Nevertheless, the annual change in distance of the Earth from Sun
is a small factor that must indeed be included in climate simulations.


-- Gordon D. Pusch

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