Babies grow in their mother’s uterus, a special organ that houses the baby until it is born. At the start of pregnancy, a mother’s egg is fertilized, which makes a new cell. The cell divides quickly into many more cells. At about one week, this tiny mass, called an embryo, sticks to the wall of the uterus, and begins to grow. From the moment of conception, 46 chromosomes and tens of thousands of genes combine to determine a baby’s physical characteristics—the sex, facial features, body type, and color of hair, eyes, and skin. At the eighth week, the embryo is called a fetus.
By the end of the twelfth week, the fetus is completely formed and is able to make a fist, can turn his or her head, and can squint and frown. Until the baby is ready to come out, it grows inside its mother’s uterus. When the baby is ready to be born, at about 40 weeks, the mother starts to feel labor contractions. The uterus squeezes and pushes the baby out of the uterus and into the world.
Camels are the only animals with humps. A camel’s hump is a giant mound of fat, Which can weigh as much as 80 pounds (35 kilograms). The hump allows a camel to survive up to two weeks without food. Because camels typically live in the deserts of Africa and the Middle East, where food can be scarce for long stretches, their hump is key to their survival. When camels are born their humps are empty pockets of flexible skin. As a camel grows and begins to form its fatty tissue reserves, the humps begin to fill out and take shape.
The humps also come in handy for humans who have domesticated the camel. For thousands of years, people have used these strong, resilient creatures for transportation and for hauling goods. The two-hump, or Bactrian, camel was domesticated sometime before 2500 B.C.E., probably in northern Iran, northeastern Afghan – istan, and northern Pakistan. The one-hump, or Dromedary, camel was domesticated sometime between 4000 and 2000 B.C.E. in Arabia.
In 1823, the English mathematician originated the concept of a programmable computer. At this time, he persuaded the British government to finance what he called an “analytical engine.” This would have been a machine that could undertake any kind of calculation. It would have been driven by steam, but the most important innovation was that the entire program of operations was stored on a punched tape (a long strip of paper in which holes are punched to store data).
Babbage’s machine was not completed in his lifetime because the technology available to him was not sufficient to support his design. However, in 1991 a team lead by Doron Swade at London’s Science Museum built the analytical engine (sometimes called a “difference engine”) based on Babbage’s work. Measuring 10 feet (3 meters) wide by 6.5 feet (2 meters) tall, it weighed three tons and could calculate equations down to 31 digits. The feat proved that Babbage was way ahead of his time, even though the device was impractical because one had to a turn a crank hundreds of times in order to generate a single calculation. Modern computers use electrons, which travel at the speed of light.
Antibiotics are medicines that help the human body fight bacteria, either by directly killing the offending germs or by weakening them so that the body’s own immune system can fight and kill them more easily.
The most widely known antibiotic is penicillin, which is made from mold. Penicillin kills bacteria by interfering with the formation of the cell walls or cell contents of the bacteria.
The Soviet satellite Sputnik 1, which was launched into space on October 4, 1957, was the first spacecraft to go into orbit around Earth. It had no crew members or animals aboard, but instead contained machines that sent information back to Earth via radio.
The former Soviet Union’s (now Russia) launch of Sputnik prompted the United States to get its first satellite, Explorer 1, into orbit quickly, igniting the so-called space race. This was the two countries’ rivalry over being the “first” in many areas of space exploration. Explorer 1’s test run in December 1957 burned on the ground, but the satellite was successfully launched into orbit around Earth on January 31, 1958.
According to many religions based on Judaism and Christianity, heaven is a state of existence where a person’s spirit is at last united with God forever. In a number of Christian religions, heaven is believed to be the reward for people who have lived good lives according to certain rules of thought and behavior that God has made known through scriptures (sacred writings, like the Bible) and through the teachings of churches and religious leaders. (Those who have not followed these rules, it is believed by many, go to a place of punishment known as hell.) Many Christians believe that at the end of the world their human forms will be resurrected in a perfect state—just as the body of Jesus Christ was, when he arose from the dead on Easter morning—and join their souls or spirits in heaven for eternity.
This idea has led to the concept that heaven is an actual place—located above—with physical characteristics. Over the centuries, through pictures and writings, people have tried to create images of heaven, imagining a place of perfect happiness perched atop fluffy white clouds. It has often been portrayed as a place full of things that would bring happiness on Earth, possessing, for instance, pearly gates and streets of gold.
Babies are born with about 300 to 350 bones, but many of these fuse together between birth and maturity to produce an average adult total of 206. Bone counts vary according to the method used to count them, because a structure may be treated as either multiple bones or as a single bone with multiple parts. There are four major types of bones: long bones, short bones, flat bones, and irregular bones. The name of each type of bone reflects the shape of the bone. The shape of the bone also tells about its mechanical function. Bones that do not fall into any of these categories are sesamoid bones and accessory bones.
Explosive chemical reactions are what send spacecraft into space. A rocket burns fuel to produce a jet of hot, expanding gas. What fuel is used varies, but whatever the mixture, it causes the explosive chemical reaction.
Because a rocket needs thrust to escape Earth’s gravity, the explosive chemical reaction takes place in a confined chamber and releases gases into a cone-shaped nozzle out the back end of the rocket. The cone shape accelerates the gases and they blast out of the engine at up to 9,941 miles (15,998 kilometers) per hour.
Without the Sun, life on Earth would not exist. The planet would be a frozen dark ball, drifting in space. The Sun provides light, heat, and energy, which stirs up the atmosphere to create winds and rain. With it, plants grow, and animals and humans eat.
However, the Sun’s heat output changes over time, which affects our daily lives, the climate, and our satellite communications.
The phrase charley horse has its roots in baseball. At the beginning of the twentieth century, groundskeepers often used old and lame horses to pull the equipment used to keep the playing field in top condition.
The Baltimore Orioles had a player named Charley Esper, who, after years of injuries, walked with pain. Because his limp reminded his teammates of the groundskeeper’s lame horse, they called Esper “Charley Horse.”