90 Facts You Never Knew You Wanted to Know

Most people think humans have only five senses, but that's not completely true. Taste, touch, smell, sight and hearing aren't the only ones. Scientists say people have between 9 and 20 senses total. These include thermoception (sense of warmth) and equilibrioception (sense of balance). There's also the sense of time, although not everyone seems to have that.

We used to think there were just 8 blood types, but there are actually over 30 known blood group systems. Here's a fun fact: For every pound of fat you gain, you generate one mile of new blood vessels to supply oxygen and nutrients. Your stomach makes a new lining every 6 days to avoid digesting itself. Nerve cells transmit 1,000 impulses per second, traveling 1 to 268 mph.

Our DNA contains 100,000 viruses. Scientists discovered one that goes back 100 million years. Your body emits visible light and you're brightest at 4pm. Your glow is least visible at 10am, about 1,000 times less than your eyes can see.

Sweat is mostly water mixed with proteins, sugars, ammonia and trace metals like copper and zinc. Sodium makes it salty - more salt intake means saltier sweat as your body tries to get rid of excess quickly by sweating.

If you walked 2 mph, you'd have to go 20 hours straight to lose 1 lb. It would take 518 days to circle the equator. Ear wax isn't wax, but fat, skin cells, sweat and dirt. Your brain triples in size the first year and reaches full maturity at 25. 60% of it is fat.

Your brain generates 23 watts, enough for a small lightbulb. Humans can't really multitask - your brain switches between tasks, which doesn't save time but increases mistakes and takes longer. Chewing gum while studying can help concentration by waking up your brain, better than caffeine, but only for 20 minutes.

The heart's beating sound is the clap of valve leaflets opening and closing. Your corneas don't get blood, but oxygen directly from air. Goosebumps are an evolutionary reflex to make hair stand up and ancestors look scarier. You produce 1-3 pints of saliva daily to help digest and fight infections. You have almost as many bacteria in your mouth as people on Earth.

Each hair strand grows 1/2 inch per month. If you added all that growth, it would be 10 miles in one year. Your hair can hold 3 oz, an apple's weight. Combined strength of all your hair could support two elephants.

Sunburn is when your body's defense against UV rays gets overwhelmed. Detachable car headrests can be used to break windows in an emergency. The White House has a flower shop in the basement. Americans buy 350 pizza slices per second. You can make lemon juice without seeds using tongs.

Tigers' stripes are all different like fingerprints. Stop signs were yellow before fade resistant red enamel was invented in the 1950s. The tallest rose bush grew to 28 1/2 feet tall. Seat belts tighten automatically to align airbags and pre-load brakes to reduce shock in a predicted collision.

Lighter car materials like aluminum alloys enable more fuel efficiency but also crumple to absorb impact in a crash. Bumpers were invented in the late 1800s to absorb impact. Windshields are laminated to prevent shattering. Airbags started in the 1960s and expanded from just the steering wheel to throughout cars by 1998.

Anti-lock brakes maintain traction on slippery roads. Adaptive cruise control adjusts speed to match slower cars ahead. Automatic high beams use cameras to determine when to switch between high and low. Blind spot monitoring alerts you to cars in adjacent lanes. Driver attention monitors suggest breaks for fatigue or phone distraction.

Tire pressure monitoring ensures you know when tires need more air. Lane keeping assists steer back into the proper lane if you drift. Night vision uses heat signatures to see pedestrians and animals in the dark. Advanced autopilot systems can steer, change lanes and brake automatically. Safety evolves constantly to keep us safe on the road.