1. You can hear the difference between hot and cold water when it's poured. View this video on YouTube Tom Scott / YouTube / Via youtube.com If that sounds fake to you, just give this video a listen. The key is that the viscosity of water decreases as the temperature increases, so the difference you're hearing is largely due to the change in viscosity. 2. Sharks existed before trees. Dcorn / Getty Images The earliest undisputed shark fossils date back 420 million years. The first trees appeared on Earth during the Devonian period, and the oldest estimates place them at about 408 million years ago. 3. Blue eyes are newer to the human race than pottery. Stevemcsweeny / Getty Images A 2008 study by a team at the University of Copehagen traced the gene for blue eyes back to one common ancestor, who mostly likely lived about 10,000 years ago. By contrast, the oldest pieces of pottery unearthed in China date back as far as 20,000 years ago. 4. Charlie Chaplin and 50 Cent were alive at the same time. Hulton Archive / Astrid Stawiarz / Getty Images Though they're thought of as living in very different times, Chaplin died on Dec. 25, 1977... Roughly two and a half years after Curtis Jackson, aka 50 Cent, was born. 5. Cumulus clouds can weigh more than a million pounds. Eerik / Getty Images An average cloud of about 1 cubic kilometer in volume would weigh an estimated 1.1 million pounds. 6. One 17-inch pizza is more pizza than two 12-inch pizzas. Issaurinko / Getty Images Let's do some pizza math, shall we? The area of a circle is π*r², so a 17-inch pizza would have an area of about 227 square inches (3.14*8.5²=226.865). A 12-inch pizza has only about 113 square inches, which makes two of them just about a square inch smaller than one 17-inch. So just order the large. 7. The state of Michigan is slightly bigger than Great Britain. iStock The area of Great Britain is 94,226 square miles, including land and water area. Comparatively, the land and water area of Michigan is 96,716 square miles. However, if you only consider land area, Britain has Michigan beat by a little over 36,000 square miles. 8. All peacocks are male. Alexeyvis / Getty Images There's no such thing as a female peacock...because they're called peahens. If you're referring to a group of the two, you'd just call them peafowl. 9. More people are killed each year by cows than by sharks. Lindsay_imagery / Getty Images The CDC found 21 incidents of cow-related deaths in a four-state area over a five-year period, which comes out to just about four deaths per year just in that area. Meanwhile, there's only about one death per year attributed to shark attacks. 10. The 2% margin of error the Chinese government aims for when taking their population census is larger than the entire population of Australia. Tyler Sprague / Getty Images The population of China, as of 2016, was 1.378 billion. Two percent of that is still a whopping 27.57 million people, which is larger than the population of Australia, which was a little over 24 million in 2016. 11. A quarter of all the bones in the human body are in the feet. Leonello / Getty Images A human foot contains 28 bones, so the total number of bones in both feet is 56. That's a little over 27% of the 206 bones in the entire human body. 12. The people who first measured Mount Everest actually added a couple inches so the number didn't sound made-up. Zzvet / Getty Images The team that first measured the height of Everest's tallest peak found that the height was exactly 29,000 feet. Fearing that the public would think the numbers were an estimate, the team reported the height as 29,002 feet in order to make it sound more accurate. Since then, more accurate methods of measurement have found the official height to be 29,035 feet. 13. Twice as many people use the New York City subway system each year than fly on domestic U.S. flights. Itsten / Getty Images In 2016, there were 711 million passengers aboard U.S. domestic flights. In the same year, 1.757 BILLION people used the MTA. Of course, these numbers reflect each time a person got on a plane or subway train and not the number of unique passengers, but still...that's a lot of people. 14. Lighters were invented before matches. Givaga / Getty Images The Döbereiner Lamp, invented by Johann Wolfgang Döbereiner in 1824, is credited with being the first push-button lighter. Dangerous matches were created before that, but safe, practical friction matches in the form we know them today — i.e. a wooden stick with an ignitable tip — weren't invented until 1827. 15. When the Krakatoa volcano erupted in 1883, the sound was so loud that it could be heard at least 3,000 miles away. Byelikova_oksana / Getty Images It's said to have been the loudest sound in recorded history. 16. The population of California is larger than the entire population of Canada. Dikobraziy / Getty Images In 2016, the population of California was reported to be 39.25 million people. In 2017, the population of Canada is estimated to be 35.62 million. California is very big. 17. The world's population doubled in the last 50 years. Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF Tap to play or pause GIF United States Census Bureau / Via census.gov In 1960, the world's population was about 3 billion people. As of 2010, that number jumped to 7 billion, more than doubling in five decades.