What's this about polarised sunglasses being bad for cycling (hexbear.net)

submitted 2 weeks ago by doublepepperoni@hexbear.net to c/urbanism@hexbear.net

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Finally got a pair of prescription sunglasses for summer, but apparently polarised lenses are potentially dangerous for cyclists according to Redditors due to light playing weird tricks on you. On my first day wearing them the only interesting thing I noticed was my phone screen shimmering like a foil trading card

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[-] JustSo@hexbear.net 14 points 2 weeks ago

only interesting thing I noticed was my phone screen shimmering like a foil trading card

if you can find a second polarized lens or glass/window with a polarizing film on it, you can play with viewing through both polarizing filters and rotating one. It's kinda cool. I think two identical lenses with one rotated 90 degrees blocks 100% of light (if the polarization is strong.) They're excellent for looking into rock pools and stuff, water in general I suppose. They cut so much glare and dazzle that otherwise only lets your eyes really see the surface of things.

A few physical phenomena look a bit different through polarized lenses, but I get used to it very quickly and I've never heard anyone ever complain about the polarizing (ha) effect doing stuff like this. I'm sure there are edge cases and particular sensitivities, but online you only need like 3 people to agree early in a discussion and you can generate new lore for that online space.

People who've never worn polarizing sunglasses now wont, because they're afraid that it will make them vulnerable to sudden death or injury and they will helpfully repeat the misinformation to save the next person who didn't hear those three guys talk about the issue that one time.

Reddit is exceptional for this, people studied early on how to most effectively manipulate public opinion on reddit with first post and/or second post bias and a few other consensus building cognitive tricks that I can't remember. Sounds really sinister and it is when it's done to intentionally manipulate people, but redditors also just do it to themselves by accident all the time.

[-] doublepepperoni@hexbear.net 6 points 2 weeks ago

if you can find a second polarized lens or glass/window with a polarizing film on it, you can play with viewing through both polarizing filters and rotating one. It's kinda cool. I think two identical lenses with one rotated 90 degrees blocks 100% of light (if the polarization is strong.) They're excellent for looking into rock pools and stuff, water in general I suppose. They cut so much glare and dazzle that otherwise only lets your eyes really see the surface of things. A few physical phenomena look a bit different through polarized lenses, but I get used to it very quickly and I've never heard anyone ever complain about the polarizing (ha) effect doing stuff like this.

That's exactly the sort of neat stuff I hoped to see with my new glasses. All the supposed negative effects on Reddit just sounded really interesting to me. Maybe I will get a second pair of sunglasses thonk . I've only ever owned one pair of glasses at a time but after discovering how cheaply you can order them online from China I've already got several

I'm sure there are edge cases and particular sensitivities, but online you only need like 3 people to agree early in a discussion and you can generate new lore for that online space. People who've never worn polarizing sunglasses now wont, because they're afraid that it will make them vulnerable to sudden death or injury and they will helpfully repeat the misinformation to save the next person who didn't hear those three guys talk about the issue that one time. Reddit is exceptional for this, people studied early on how to most effectively manipulate public opinion on reddit with first post and/or second post bias and a few other consensus building cognitive tricks that I can't remember. Sounds really sinister and it is when it's done to intentionally manipulate people, but redditors also just do it to themselves by accident all the time.

Reminds me of the old ProZD skit about enthusiast subreddits

[-] insurgentrat@hexbear.net 8 points 2 weeks ago* (last edited 2 weeks ago)

Enjoy looking deep into water as you knock out all the polarised light from Brewster's angle that gets reflected off the surface.

Also you can see stress in transparent plastics as rainbows!

[-] SpookyVanguard64@hexbear.net 5 points 2 weeks ago

Another interesting thing you can look for is the band of polarized light in the sky created by Rayleigh scattering. Just look anywhere that's 90 degrees away from the sun.

[-] doublepepperoni@hexbear.net 2 points 2 weeks ago

Not sure if it's related but I have noticed the entire sky sometimes darkening when tilting my head to the side. Some manhole covers shimmer, so presumably other metal surfaces can do so too. I have another phone which doesn't have the foil effect, instead the screen just goes black when I turn it sideways. Very cool!

[-] SpookyVanguard64@hexbear.net 2 points 2 weeks ago* (last edited 2 weeks ago)

Yeah, the whole sky darkening should also be related to Rayleigh scattering, since all sunlight that gets scattered by the atmosphere will get polarized to some extent. The effect is just most intense 90 degrees from the light source.

The shimmery foil effect is likely due to birefringence. Basically some materials have a different index of refraction depending on the polarization and direction of travel, causing the light passing through to get split based on its polarization. Not sure exactly where the color shimmer comes from though tbh. I'm thinking it's some sort of interference pattern created by the polarized light components recombining out of phase or something like that, but I could be wrong about that. It's been like 4 years since I graduated with my physics degree, and optics was never my strong suit lol.

(I am taking an intro to materials science class right now though, and one of the main ways to create birefringence is passing light through a non-cubic crystal structure, so I imagine we'll probably cover that once we cover optical properties in the next few weeks. Speaking of which, martensite is the only microstructural variant of steel that I'm aware of that has a non-cubic crystal structure, so I wonder if those manhole covers you're seeing are made of martensitic steel.)