[ceejayoz]

Yeah, people get really messed up by just how good our eyes are. (For a close-to-home example, people think indoor plants get a lot closer to sunlight-level amounts than they really do.)

We can spot a single photon in the right conditions. https://www.nature.com/articles/ncomms12172

[zarmin]

Eye sensitivity isn't the issue. Sirius isn't barely visible at the detection threshold, it's the brightest star in our sky. If a 25x luminosity boost over the Sun only gets you to the edge of naked-eye visibility at that distance, where do the additional orders of magnitude come from to make it one of the most prominent objects in the night sky? Show me the math.

[ceejayoz]

> Sirius isn't barely visible at the detection threshold, it's the brightest star in our sky.

And it's entirely washed out during the day. The full Moon is very bright, but it's still 400,000 times dimmer than the Sun when seen from Earth, and that's only ten different. The brightest star in our sky is simply not very bright; our eyes are just pretty awesome.

That star you are seeing is 25 orders of magnitude dimmer.

https://astro.wku.edu/labs/m100/mags.html

"While you may perceive one star to be only a few times brighter than another, the intensity of the two stars may differ by orders of magnitude. (Light intensity is defined as the amount of light energy striking each square cm of surface per second.) The eye is a logarithmic detector. While the eye is perceiving linear steps in brightness, the light intensity is changing by multiplicative factors. This is fortunate; if the eye responded linearly instead of logarithmically to light intensity, you would be able to distinguish objects in bright sunlight, but would be nearly blind in the shade! If logarithms are a faint memory, you should peruse a refresher on logs and logarithmic scales before continuing."

https://physics.stackexchange.com/questions/329971/how-many-... says looking up at a sunny sky lets you take in 3×10^14 photons per second per eye. Yet you can see a single photon! https://www.nature.com/articles/ncomms12172

Or, we can conclude the entire field in dozens of countries simply can't do math. Your choice.