What are some useless facts that everyone knows?

1.The average person swallows 8 spiders per year while asleep: This fact has been debunked and widely regarded as a myth. Spiders typically avoid humans, and it's highly unlikely for them to crawl into our mouths while we sleep.

2. Bats are blind: Contrary to popular belief, many bat species can see quite well. However, some bats rely on echolocation to navigate in the dark, which gives the false impression that they are blind.

3. A penny dropped from a tall building can kill someone: It's unlikely for a penny to gain enough velocity during free fall to cause serious harm. Terminal velocity for a penny is relatively low, so it wouldn't pose a significant danger to anyone below.

4. Humans only use 10% of their brains: This misconception has been perpetuated by various self-help gurus and popular media. In reality, we use a significant portion of our brains, and modern imaging techniques have shown that different regions are active during various tasks.

5. Cracking your knuckles leads to arthritis: Despite common belief, there is no scientific evidence linking knuckle cracking to arthritis. The cracking sound is caused by gas bubbles in the joint fluids, and it typically doesn't cause any long-term damage.