Hypodermic injection needles aren't made by drilling hole... | funfact.wiki | funfact.wiki
Hypodermic injection needles aren't made by drilling holes. A flat steel strip is rolled into a tube, welded, then pulled through progressively smaller holes. Larger gauge numbers mean thinner needles — 18G means the wire passed through 18 holes.
The barbershop pole originated from a time when barbers in Europe also performed surgery. Red represents arteries and bleeding, blue represents veins and shaving, and white represents bones and bandages.
In 19th-century Paris, all city clocks were synchronized via compressed air. Around 300km of underground pipes carried minute-by-minute pressure pulses from a central master clock to over 4,000 clocks. When the 1910 Paris flood hit, every clock in the city froze at 10:53 AM.
The fact that scurvy can be prevented with citrus fruits was known as early as the 1400s. Yet humanity kept rediscovering and forgetting this cure for over 400 years. Mainstream medicine did not fully accept it until 1907.
Highway and railroad curves are not circular arcs — they use a special shape called a "clothoid" (Euler spiral). Its curvature changes gradually, so centrifugal force increases smoothly when transitioning from a straight section to a curve, rather than hitting suddenly.
When bees are repeatedly exposed to explosive scents followed by sugar water, they eventually extend their tongues at the smell alone. A real device was built with 36 trained bees in sensor cartridges as an explosive detector. Training a dog takes months, but bees need only a few hours.