[Coda]

Originally Posted by Potironette

Is the light that I see not the same light that another person sees?

Nope. It comes from the same source, but the photons are distinct.

The pupils take time to adjust...do you mean that when the light first turns on and off, people don't see the room and just see the bright flash and that's because the eye can't make out the details because it needs to adjust?

Yes. A less-bright pulse of light, on the other hand, can do a fairly good job of giving you an impression of the room, but your body's reaction will make the darkness afterward feel even darker.

This is why you should try to avert your eyes from oncoming headlights when driving at night, by the way -- the bright light in your face diminishes your low-light vision.

Why do pupils need to be protected :o?
I mean, it makes sense pupils need to be protected, but why is light harmful? Is it like the sunspots thing where when I look at a super bright object I see a blob in my eyes for a while? What is that?

That's retina burn. Mild cases just result in the nerves in your eyes getting overloaded for a while and sending off bad signals until they recover -- that's what the spots are. More serious cases, like looking into the sun for more than a brief moment, can lead to permanent blindness. This risk of damage is why we have reflexes to make us blink and look away, because we as a species depend so strongly on our sense of vision.

EDIT: Forgot to explain why light is harmful. Long story short, light is energy. Put too much energy into a living cell and it cooks. Your eye has a lens in it that concentrates light onto the retina, and your retina is made of very very sensitive cells, so it takes less light to cause damage there than to -- for example -- your skin. (On the other hand, the lens filters out the ultraviolet light that can cause DNA damage, so unless you've had cataract surgery or something that removes the lenses you don't have to worry about sun-induced retinal cancer like you have to worry about skin cancer.)