* individual genetics (maybe including something about the anatomy of your iris? or the focal abilities of your eye?)
* how fixedly you manage to stare at the sun, as opposed to letting your eye wander around a bit
* how frequently you unconsciously blink
that would cause the degree of injury to vary a lot. But it's understandable that experts would like to emphasize the really, just don't stare at the sun principle as the most reliable advice, so people don't do a lot of second-guessing (like "oh well I'm at a high latitude so it's not that bad").
I had also stared at the sun a little bit on occasion in elementary school (but for like 4-5 seconds, not like 30 seconds!) and that was one thing that gave me some counterproductive confidence that it wouldn't be super-harmful super-quickly.
¹ Notably, a lot of people will "watch the sunset" for like 1-5 minutes at a time, which is a form of starting at the sun, and I've never heard of that causing anyone any trouble. It really is true that time of day and latitude both have a big effect on the intensity of sunlight. Among other things, this interactive diagram makes pretty clear why watching the moment of sunset isn't that dangerous: https://engaging-data.com/solar-intensity/
It's easy to confirm there that the incident power in direct sunlight can vary by a factor of 100× as you get further from the tropics and closer to the moment of sunrise or sunset.
But it's not a great risk to have lots of people apply these heuristics to justify staring at the sun. If you just get a little bit confused about the details, the potential for damage is very, very high!
* latitude
* time of day¹
* individual genetics (maybe including something about the anatomy of your iris? or the focal abilities of your eye?)
* how fixedly you manage to stare at the sun, as opposed to letting your eye wander around a bit
* how frequently you unconsciously blink
that would cause the degree of injury to vary a lot. But it's understandable that experts would like to emphasize the really, just don't stare at the sun principle as the most reliable advice, so people don't do a lot of second-guessing (like "oh well I'm at a high latitude so it's not that bad").
I had also stared at the sun a little bit on occasion in elementary school (but for like 4-5 seconds, not like 30 seconds!) and that was one thing that gave me some counterproductive confidence that it wouldn't be super-harmful super-quickly.
¹ Notably, a lot of people will "watch the sunset" for like 1-5 minutes at a time, which is a form of starting at the sun, and I've never heard of that causing anyone any trouble. It really is true that time of day and latitude both have a big effect on the intensity of sunlight. Among other things, this interactive diagram makes pretty clear why watching the moment of sunset isn't that dangerous: https://engaging-data.com/solar-intensity/
It's easy to confirm there that the incident power in direct sunlight can vary by a factor of 100× as you get further from the tropics and closer to the moment of sunrise or sunset.
But it's not a great risk to have lots of people apply these heuristics to justify staring at the sun. If you just get a little bit confused about the details, the potential for damage is very, very high!