Wild Insides
#5How things work
Why Shopping Carts Lock Up At The Parking Lot Edge
Some shopping carts have a hidden brake in one wheel.
Short. Strange. True.The real science
smoke alarm · how smoke detectors work · americium · radioactive · alpha particles · ionization smoke alarm
The real science
Many smoke alarms hold a tiny amount of radioactive americium. Its alpha particles turn the air between two metal plates into a sensor, and smoke breaks the current. The metal is made in nuclear reactors, but its radiation can't even get through a sheet of paper. Test your alarm once a month.
Don’t try anything shown in this video.
Follow the facts
- US EPA: Americium in Ionization Smoke Detectors
- BBC Bitesize: Smoke detectors
- Nuclear Regulatory Commission: Backgrounder on Smoke Detectors
Ask about this science
Curious about something in “There's A Radioactive Speck In Your Smoke Alarm”? Our AI-powered helper answers using only this page’s write-up and sources.
AI answers can be wrong; check the sources. Not medical advice.
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#5
#3How things work
Why A Snapped Elevator Cable Won't Drop You
Almost everyone has wondered what happens if an elevator's cable snaps.
Short. Strange. True.The real science
#2How things work
How Pill Bottle Caps Outsmart Most Toddlers
Child-resistant medicine caps hide a two-part lock that only opens when you push down and turn at the same time.
Short. Strange. True.The real science