Life-changing science discoveries

Try to imagine life without antibiotics. We wouldn't live nearly as long as we do without them. Here's a look at some discoveries that have changed the world. It's impossible to rank their importance, so they're listed in the order they were discovered.

The Copernicum System ·In 1543, while on his deathbed, Polish astronomer Nicholas Copernicus published his theory that the Sun is a motionless body at the center of the solar system, with the planets revolving around it. Before the Copernicum system was introduced, astronomers believed the Earth was at the center of the universe.

Gravity · Isaac Newton, an English mathematician and physicist, is considered the greatest scientist of all time. Among his many discoveries, the most important is probably his law of universal gravitation. In 1664, Newton figured out that gravity is the force that draws objects toward each other. It explained why things fall down and why the planets orbit around the Sun.

Electricity · If electricity makes life easier for us, you can thank Michael Faraday. He made two big discoveries that changed our lives. In 1821, he discovered that when a wire carrying an electric current is placed next to a single magnetic pole, the wire will rotate. This led to the development of the electric motor. Ten years later, he became the first person to produce an electric current by moving a wire through a magnetic field. Faraday's experiment created the first generator, the forerunner of the huge generators that produce our electricity.

Evolution · When Charles Darwin, the British naturalist, came up with the theory of evolution in 1859, he changed our idea of how life on the Earth developed. Darwin argued that all organisms evolve, or change, very slowly over time. These changes are adaptations that allow a species to survive in its environment. These adaptations happen by chance. If a species doesn't adapt, it may become extinct. He called this process natural selection, but it is often called the survival of the fittest.

Microorganisms · Before French chemist Louis Pasteur began experimenting with bacteria in the 1860s, people did not know what caused disease. He not only discovered that disease came from microorganisms, but he also realized that bacteria could be killed by heat and disinfectant. This idea caused doctors to wash their hands and sterilize their instruments, which has saved millions of lives.

Theory of Relativity · Albert Einstein's theory of special relativity, which he published in 1905, explains the relationships between speed, time and distance. The complicated theory states that the speed of light always remains the same – 186,000 miles/second (300,000 km/second) regardless of how fast someone or something is moving toward or away from it. This theory became the foundation for much of modern science.

The Big Bang Theory · Nobody knows exactly how the universe came into existence, but many scientists believe that it happened about 13.7 billion years ago with a massive explosion, called the Big Bang. In 1927, Georges Lemaître proposed the Big Bang theory of the universe. The theory says that all the matter in the universe was originally compressed into a tiny dot. In a fraction of a second, the dot expanded, and all the matter instantly filled what is now our universe. The event marked the beginning of time. Scientific observations seem to confirm the theory.

Penicillin · Antibiotics are powerful drugs that kill dangerous bacteria in our bodies that make us sick. In 1928, Alexander Fleming discovered the first antibiotic, penicillin, which he grew in his lab using mold and fungi. Without antibiotics, infections like strep throat could be deadly.

DNA · On February 28, 1953, James Watson of the United States and Francis Crick of England made one of the greatest scientific discoveries in history. The two scientists found the double-helix structure of DNA. It's made up of two strands that twist around each other and have an almost endless variety of chemical patterns that create instructions for the human body to follow. Our genes are made of DNA and determine how things like what color hair and eyes we'll have. In 1962, they were awarded the Nobel Prize for this work. The discovery has helped doctors understand diseases and may someday prevent some illnesses like heart disease and cancer.

Periodic Table · The Periodic Table is based on the 1869 Periodic Law proposed by Russian chemist Dmitry Mendeleev. He had noticed that, when arranged by atomic weight, the chemical elements lined up to form groups with similar properties. He was able to use this to predict the existence of undiscovered elements and note errors in atomic weights. In 1913, Henry Moseley of England confirmed that the table could be made more accurate by arranging the elements by atomic number, which is the number of protons in an atom of the element.

X-Rays · Wilhelm Roentgen, a German physicist, discovered X-rays in 1895. X-rays go right through some substances, like flesh and wood, but are stopped by others, such as bones and lead. This allows them to be used to see broken bones or explosives inside suitcases, which makes them useful for doctors and security officers. For this discovery, Roentgen was awarded the first-ever Nobel Prize in Physics in 1901.

Quantum Theory ·Danish physicist Niels Bohr is considered one of the most important figures in modern physics. He won a 1922 Nobel Prize in Physics for his research on the structure of an atom and for his work in the development of the quantum theory. Although he helps develop the atomic bomb, he frequently promoted the use of atomic power for peaceful purposes.

Atomic Bomb · The legacy of the atomic bomb is mixed: it successfully put an end to World War II, but ushered in the nuclear arms race. Some of the greatest scientists of the time gathered in the early 1940s to figure out how to refine uranium and build an atomic bomb. Their work was called the Manhattan Project. In 1945, the U.S. dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki. Tens of thousands of civilians were instantly killed, and Japan surrendered. These remain the only two nuclear bombs ever used in battle. Several of the scientists who worked on the Manhattan Project later urged the government to use nuclear power for peaceful purposes only. Nevertheless, many countries continue to stockpile nuclear weapons. Some people say the massive devastation that could result from nuclear weapons actually prevents countries from using them.

HIV / AIDS · In 1983 and 1984, Luc Montagnier of France and Robert Gallo of the United States discovered the HIV virus and determined that it was the cause of AIDS. Scientists have since developed tests to determine if a person has HIV. People who test positive are urged to take precautions to prevent the spread of the disease. Drugs are available to keep HIV and AIDS under control. The hope is that further research will lead to the development of a cure.