I learned this today. Stars die because they exhaust all of their fuel. There are seven different types of star. They are classified using the Morgan-Keenan system. They are given the letters, B, A, F, G, K, and M, to show temperature, and Roman numerals to show luminosity. M, the coolest stars, are between 2,400 […]
#87 How do stars die? Read More »
I learned this today. On November 14th, 1910, Eugene Ely flew a plane off a ship, technically making that ship the first ever aircraft carrier. He made the first takeoff and landing in 1911. It was a flying event in Belmont Park, New York and Eugene Ely was trying to prove that it was possible
#86 When did people start using aircraft carriers? Read More »
The first ever money was the Mesopotamian shekel, used about 5,000 years ago. Before we had money, people used the bartering system. Bartering probably started when hunter-gatherers began to form larger groups. When hunter-gatherers were in small groups, they could service all of their own needs. They only needed food, clothing, and shelter. Once the
#85 When did people start using money? Read More »
I learned this today. London was built where it is because it is the closest point to the sea that could be bridged. There may have been a small settlement where London is from prehistoric times, but there is no real evidence for that. There is, however, evidence of a bridge crossing the river Thames
#84 Why is London where it is? Read More »
I learned this today. Quartz watches are far more precise than mechanical clocks because they make quartz crystals oscillate at a very precise frequency. A mechanical watch has an accuracy of ±5 seconds a day. Quartz watches have an accuracy of about ±5 seconds a month. For comparison, an atomic clock has an accuracy of
#83 How does a quartz watch work? Read More »
I learned this today. Our skin can allow sweat out, but it doesn’t let water in thanks to a thin layer of fat between the outermost layers of skin cells. The skin is said to be the largest organ in the human body. Actually, by surface area, it is the second largest because the inside
#82 Why is skin waterproof? Read More »
I learned this today. Whales make use of sound in the water because they cannot use their other senses. It is not possible to use light to see underwater because the water scatters it too much. Plus, some whales dive over 2,000m and light doesn’t really penetrate much farther than 1,000m. They also cannot rely
#81 Why do whales make sounds? Read More »
I learned this today. The Middle Ages and the Dark Ages both refer to Europe between the Fall of Rome in 476 AD and the beginning of the Renaissance in the 14th century. Some people say the “Medieval Period” is a better expression, but this means pretty much the same thing. The idea that this
#80 Why do we say Middle Ages and Dark Ages? Read More »
I learned this today. Dogs can probably smell cancer in people. Dogs have a phenomenal sense of smell. They have 300 million olfactory receptors in their noses. We have about 6 million. On top of this, the part of their brain that is devoted to analyzing smells is about 40 times larger than ours. It
#79 Can dogs smell cancer? Read More »
I learned this today. Steam cars outnumbered internal combustion engine cars and electric cars from 1900 until about 1907. Steam engines are external combustion engines because the fuel is burned away from the engine. They release far fewer polluting gases than internal combustion engines. A steam engine works by burning a fuel source to heat
#78 Why were steam cars so popular in 1900? Read More »
