Muscles are attached to bones by tendons, the longest and strongest of which is called the Achilles tendon in your heel. This thick band of tissue attaches the muscles of the calf to the heel bone and is the key to the foot’s ability to flex.
The Achilles tendon allows you to push off of your foot when walking or running. In ancient Greek myth, the hero Achilles died from a wound to his heel, so the popular expression “Achilles heel” often refers to a physical weakness or limitation.
An avalanche is a huge mass of ice and snow that breaks away from the side of a mountain and slides downward at great speed. Most avalanches result from weather conditions, such as heavy winds and earth tremors, that cause snow on a mountain slope to become unstable.
A large avalanche in North America might release 300,000 cubic yards of snow—the equivalent of 20 football fields filled 10 feet (3.3 meters) deep with snow. Wintertime, particularly from December to April, is when most avalanches occur.
All living things need water to survive. Without water, the human body stops working properly. Water makes up more than 50 percent of your body weight and a person cannot survive for more than a few days without it. Water flushes toxins out of your organs, carries nutrients to your cells, and provides a moist environment for ear, nose, and throat tissues.
Water is also in lymph, a fluid that is part of your immune system, which helps you fight off illness. You need water to digest your food, to get rid of waste, and to sweat. Too little water in your body leads to dehydration, and it can make you tired and unable to function. Your body gets water from drinking it, but lots of foods, such as fruits and vegetables, contain water too.
Living creatures need oxygen to survive, and fish are no exception. Human beings 68 use their lungs to take in oxygen, and fish breathe using their gills. A fish’s gills are full of blood vessels that absorb the tiny particles of oxygen from the water.
The fish sucks the water in through its mouth and squirts it out through its gills; during this process, the gills take the oxygen from the water into the blood vessels. A fish’s gills are not constructed to take oxygen from the air, so they cannot breathe on dry land.
The fastest growing hairs on the human body are men’s beard hairs. If the average male never trimmed his beard, it would grow to almost 30 feet (9 meters) long in his lifetime.
Scientists don’t really know why we cry when we’re unhappy or hurt (or sometimes, even joyful). But tears help express deeply felt emotions and often release stress and tension from the body. From our earliest days, when we were babies and could not yet communicate through language, crying let the people around us know that we needed something.
Frequently, even after we become older, crying still serves as a wordless signal that something help or comfort is needed. In places all over the world, no matter what language is spoken, crying expresses emotions that are easily understood by all.