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If we reverse the situation the analysis is clearly flawed. The Sun is not a particularly bright star in an absolute sense, but it's extremely bright to us. If
by dreamcompiler 5y ago
If we reverse the situation the analysis is clearly flawed. The Sun is not a particularly bright star in an absolute sense, but it's extremely bright to us. If you moved it a few hundred AU farther away, it would become difficult to distinguish from the background stars. Clearly distance makes a difference in apparent brightness.
One thing that happens is that once the star fills a 2D area in the sky its brightness stops falling off at 1/r^2 and falls off at 1/1 (no falloff) in the near field where the area is a significant fraction of the overall field.
- marcan_42 5y ago> If we reverse the situation the analysis is clearly flawed. The Sun is not a particularly bright star in an absolute sense, but it's extremely bright to us. If you moved it a few hundred AU farther away, it would become difficult to distinguish from the background stars. You missed my point about pointlike objects. If you moved the sun 1 AU further away, it would of course cast 1/4 of the total light on the Earth, but as an object in the sky it would have the same surface brightness as it does now. It would just look smaller. I'm talking about the appearance of objects in the sky to a camera-like observer. Once the distance increases to the point where the human eye cannot resolve it beyond a single point, then brightness starts diminishing with distance. This is the case for all single stars other than the sun. This is not the case for aggregate objects like galaxies that are large enough to see as non-points with the naked eye, like Andromeda, regardless of whether they are composed of individual pointlike stars or not.