People are mind-blown after learning the real reason train windows have black dots.
Life's full of little mysteries, which way should toilet paper hang, why does one AirPod always die faster than the other, and what's the correct way to go to the toilet?
Well, as they say, everyday's a school day and people were fascinated to find out why a certain design on trains exists.
If you've ever sat by the window on a train, bus or car, you've likely noticed those little black dots around the edges of the glass. They're everywhere once you start looking for them, but most people just assume they're some kind of decoration or design feature.
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Well, someone on TikTok finally answered the question that's been bugging people for years, and the explanation is clearer for some more than others.
Before the answer came out, people shared their theories. Some joked they were 'braille' for visually impaired passengers, while others thought they were just there for 'decorative effect'.
Turns out, they're actually called 'frit' and they're essential from an engineering point of view.
"It's a baked-on ceramic pattern that's there because glass and the metal frame around it expand at different rates," the man explains on the TikTok. "And this pattern distributes the heat a bit more evenly, so the glass doesn't crack."
Basically, when temperatures change, glass and metal expand and contract at different speeds. Without something to help manage this difference, the stress could cause the window to crack or even shatter.
They're also not randomly placed.
They're positioned in what's called a 'halftone pattern,' getting smaller and farther apart as they move away from the frame. This creates a gradual transition that helps distribute heat and stress more evenly.
These ceramic patterns are literally baked into the glass during manufacturing, making them virtually indestructible.
The same technology is used on car windows, which is why you'll see similar black dots around the edges of your windscreen and rear window.
The TikTok explanation has gone viral, with people expressing amazement at finally learning the truth about something they see every day.
"The mansplaining that i want in my relationship," one TikTok user joked.
"oh god i love fun little facts of the world around us," another admitted.
Others admitted they were none the wiser, commenting: "i understood nothing".
Over on Instagram, where the clip was also shared, people were equally impressed.
“Finally knowing this is very satisfying to my inner child,” a commenter wrote under the Instagram user’s original post.
“I ALWAYS WONDERED!” another Instagrammer wrote.