Question

How much dimmer does the Sun appear from Pluto than from the Earth?

Answer 1

On average, the ratio of apparent brightnesses is about 1560 to 1.

Explanation:

The apparent brightness of the Sun from any orbiting object varies, because the orbits are elliptical and so the distances vary. But on average Pluto is about `39.5` times as far from the Sun as Earth is.

Then the apparent brightness of the Sun varies inversely with the square of distance, so:

`{"Brightness on Earth"}/{"Brightness on Pluto"}=39.5^2=1560`.