in astronomy, why does flux decrease with distance but not intensity?

Question

in astronomy, why does flux decrease with distance but not intensity?

In: 2

Answer 1

It depends on what you mean by flux and intensity; different fields and subfields annoyingly use the same words to describe different things.

In the way you probably mean it, ‘flux’ means how tightly packed the light is. As you get farther away, the light has more room to spread out.

In the way that you probably mean it, ‘intensity’ refers to how tightly packed the light in one particular direction is. Since the light is all going in one direction, it does not spread out as you get farther away.