5 things you thought were true but arent

1. Cracking your knuckles gives you arthritis.

THE MYTH: People who crack their knuckles are slowly twisting their hands into hideous wizened claws.

THE TRUTH: Multiple studies have found no link whatsoever between the annoying habit and arthritis. The cracking sound isn’t bones being mangled out of shape but the release of pockets of gas from between joints. That said, long periods of knuckle cracking may contribute toward lower grip strength. So pack it in.

2. Toilet doors are dangerous.

THE MYTH: Touch a door handle on the way out of a public toilet and you might as well have eaten a germ sandwich.

THE TRUTH: Door handles have the least bacteria of any surface in the room, according to a test carried out at the University of Arizona. Even though a fairly disgusting 32% of people don’t wash their hands after relieving themselves, to pick up something like salmonella from the germs they leave behind on the handle would require a huge dose. Coupled with the fact that most bacteria need a warm, moist environment to survive and can only live on hard, dry surfaces for a couple of hours, you’re pretty much in the clear.

3. Chewing gum stays in your body.

THE MYTH: Accidentally swallow a chunk of Wrigley’s and your gastrointestinal tract will be wrestling with it for more than half a year.

THE TRUTH: Pediatric gastroenterologist David Milov of Nemours Children’s Clinic in Florida told Scientific American that this is 100% poppycock. “That would mean that every single person who ever swallowed gum within the last seven years would have evidence of the gum in the digestive tract,” he said. “But colonoscopies and capsule endoscopy procedures turn up no such evidence.” In reality, it’ll hang around for about a week.

4. Nails and hair continue to grow after you die.

THE MYTH: As though corpses weren’t disturbing enough, we all turn into Stig of the Dump in death.

THE TRUTH: From the moment you’re dead, your hair and fingernails decay with the rest of you. This myth comes from the fact that skin recedes from a dead body, making nails and hair appear longer.

5. You can see the Great Wall of China from space.

THE MYTH: From the cold nothingness of outer space, the only visible evidence of mankind is China’s huge wall — which can even be viewed from the moon.

THE TRUTH: Even from the relatively low orbit of the International Space Station — about 173 miles above sea level — the Great Wall is impossible to make out. From the moon? Forget about it. This decades-old myth occurs in old school textbooks but was actually disproven by one of China’s own astronauts, Yang Liwei. You can, however, see the pyramids from space. If you squint a bit.