I learned this today. The aurora borealis are green, purple, pink, and blue because those are the colors given off when the different elements in the atmosphere are heated up. The aurora borealis is caused by electrically charged particles from space hitting the magnetic field in the upper atmosphere at a very high speed. The […]
#264 Why are the aurora borealis those colors? Read More »
I learned this today. Trees have rings because they do not grow through the winter when it is too cold. The study of tree rings is called dendrochronology. The word comes from ancient Greek: dendron means “tree”, khronos means “time”, and logia means “the study of”. So, it is the study of tree time. What
#263 Why do trees have rings? Read More »
I learned this today. Hardtack is a dense biscuit made from flour, water, and sometimes salt. It was sometimes called “ship’s biscuit” because it was a staple on long voyages. The word “hardtack” comes from the British sailor slang for food, “tack”. It was called “hardtack” because it was extremely hard. Hardtack is a very
#262 What is hardtack? Read More »
I learned this today. The first paper money was issued in China in the 7th century. Many countries around the world had started using different things as “money” by about 3000 BC. They were first used to represent a weight of something. For example, the Mesopotamian shekel represented 160 grains of barley. It was easier
#261 When did people first start using paper money? Read More »
I learned this today. Animals can sleep standing up by locking a set of muscles and tendons in their legs, using gravity to lock a joint, or using a flexor tendon. There are a lot of animals that can sleep while they are standing, but they can only do that through slow-wave sleep. To enter
#260 How do some animals sleep standing up? Read More »
I learned this today. A hand grenade works because the removal of the lever starts a series of steps that ends with an explosion. There are many different types of grenade. I am going to look at the fragmentation grenade. Most of us imagine the Mk 2 grenade when we think of a hand grenade.
#259 How does a hand grenade work? Read More »
I learned this today. The energy from the photons in a laser beam can be used to propel a very light sail into space. A laser powered solar sail could let us look at the planets around the closest star to us. Laser propulsion has been suggested as the best way we have of reaching
#258 How can a laser power a solar sail? Read More »
I learned this today. The first war correspondent is technically William Howard Russell. William Howard Russell was a war correspondent during the Crimean War. The Crimean War was a war between Russia on one side and the Ottoman Empire, France, and the United Kingdom on the other side. It lasted from October 1853 to February
#257 Who was the first war correspondent? Read More »
I learned this today. The Richter scale is a way of measuring the strength of an earthquake by looking at the height of its seismic wave. The Richter scale was developed in 1935 by Charles Francis Richter. He was an American physicist who was very interested in seismology. He came up with his system because
#256 What is the Richter scale? Read More »
I learned this today. The surface tension of water is higher than almost all other liquids because it contains so much hydrogen. Surface tension is what allows droplets to form on leaves, like the picture with this post, and for you to keep adding drops of water to a glass without it spilling over the
#255 Why is the surface tension of water so high? Read More »
