this post was submitted on 16 Jun 2026
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Today I Learned

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[–] village604@adultswim.fan 93 points 2 days ago (8 children)

Fun semi-related fact:

Have you ever walked outside on a bright day and it's so bright it hurts? Turns out there's a max pain limit from brightness per eye, and your brain adds them together.

By closing one eye, you cut the total possible pain in half.

[–] IPeaceInYourFace@lemmy.world 10 points 1 day ago (1 children)

Anybody else close one eye when it's too loud and they need to think?

Now it makes sense.

Less GPU usage by eyeballs, more capacity for prediction algorithms.

[–] village604@adultswim.fan 7 points 1 day ago

Same logic as turning down the radio when looking for a street.

[–] NABDad@lemmy.world 24 points 2 days ago (2 children)

Absolutely unfun semi-related fact:

Sometimes when one eye is injured, the injured eye has to be removed or your body will decide the uninjured eye is bad and your immune system will destroy it.

Sympathetic Ophthalmia

If the injured eye has no chance of recovery, they scoop it out.

[–] village604@adultswim.fan 7 points 2 days ago (2 children)

Your body can also just decide it doesn't like a finger or limb and kill it.

[–] NABDad@lemmy.world 18 points 2 days ago (2 children)

Yeah, the immune system can be moronic. Intelligent design my ass.

However, there's something extra special about getting poked in one eye and having your own immune system decide that an eye for an eye means your good eye has to die.

[–] cynar@lemmy.world 4 points 1 day ago (1 children)

I think the immune system can't see the eye, so it's never trained to avoid it. If the eye is damaged, the immune system can become aware of it and start reacting. Once it starts, pulling it back is not easy.

The immune response system is simultaneously amazing and insane.

It basically deliberately scrambles part of the DNA in the immune cells that create antibodies. The rest of the body then sheds cells into the blood to move to the lymph nodes. Any immune cells that react then self destruct.

It's the equivalent of firing a paint blunderbuss at a wall, and creating a silhouette by standing in the way!

[–] NABDad@lemmy.world 2 points 1 day ago (1 children)

My immune system pisses me off constantly.

It let COVID through three times despite me rigorously keeping up to date with the vaccines as much as possible, and at the same time it has destroyed my thyroid gland and it has declared cherries and peaches as terrorist infiltrators.

I feel like if my immune system is so bored it needs to attack harmless things, I should never have to deal with any actually harmful thing.

It's like a cop that beats up an unarmed teenager, but hides when someone is shooting up a school.

[–] cynar@lemmy.world 2 points 1 day ago

I definitely think there are grounds to the cleanliness hypothesis. Basically the immune system expects a certain amount of activity. If it's underperforming, the body systems assume it's a problem with the immune system, not a lack of bugs, because we are too clean. It then racks up activity levels, causing problematic autoimmune or allergy reactions.

[–] Swedneck@discuss.tchncs.de 2 points 1 day ago

that last bit is very satisfying to say

[–] finallymadeanaccount@lemmy.world 1 points 2 days ago (1 children)

Fuck sake! How else am I supposed to pick my nose?

[–] village604@adultswim.fan 3 points 1 day ago

You still have toes, ostensibly.

[–] k_rol@lemmy.ca 3 points 2 days ago
[–] Jax@sh.itjust.works 20 points 2 days ago (1 children)

Huh, I've always closed one eye when it's super bright because it's simply more comfortable. Cool to have the behavior defined this way.

[–] AI_toothbrush@lemmy.zip 6 points 2 days ago

I never knew why the hell that worked, it seemed so bizarre and knowing it this way really is cool

[–] danekrae@lemmy.world 30 points 2 days ago (1 children)

Or just look cool and sexy by squinting.

[–] Swedneck@discuss.tchncs.de 2 points 1 day ago
[–] cevn@lemmy.world 21 points 2 days ago

This explains why I have to close one eye to go outside in the sun lol

[–] NOT_RICK@lemmy.world 6 points 2 days ago (2 children)

That is fun, I’ve wondered why that is. I also think sometimes when it’s super bright out it makes me sneeze.

[–] village604@adultswim.fan 5 points 2 days ago (2 children)

That's definitely a known thing.

My brain is weird, because if I'm super nauseous it makes me sneeze then I feel better

[–] Nurse_Robot@lemmy.world 9 points 2 days ago

Photic sneeze response

[–] sydd@lemmy.world 2 points 2 days ago

Pretty sure it's related to the vagus nerve, maybe someone more knowledgeable can chime in.

[–] Onomatopoeia@lemmy.cafe 1 points 2 days ago

Ok, John Denver! 🤪

[–] Airfried@piefed.social 3 points 2 days ago

I did notice that but I never even wondered why that is. Neat!

[–] LodeMike@lemmy.today 4 points 2 days ago (1 children)

Is this that odd? We experience less pain if one of two arms has a knife in it instead of both.

[–] SpacetimeMachine@lemmy.world 9 points 2 days ago (2 children)

It is a bit odd. Your eyes feel pain to tell you whatever you are seeing might damage them if you look too long. But if you close one eye the pain can disappear entirely, even though that single eyes experience is the exact same.

[–] Rooster326@programming.dev 2 points 2 days ago

Better to go blind in one eye. Then you can have a sweet eye patch

[–] LodeMike@lemmy.today 1 points 2 days ago

So it is averaged over both eyes. Do yoh experience any pain in one eye? Or is it always averaged over both?