Question

“How bright would the sun appear to an observer on Earth if the sun were four times farther from Earth than it actually is? Express your answer as a fraction of the sun’s brightness on Earth’s surface.”

Answer 1

Like a lot of other things, (gravity, sound, electrostatic force), brightness also decreases as the square of the distance.

When the source moves to a new position that's 4 times as far away, its apparent brightness becomes (1/4^2) its original value.

That's 1/16 .