According to the ancient Greeks, the classical elements of the universe were earth, air, fire, and water. This view point continued through the Dark Ages into the Age of the Enlightenment. Once scientists began measuring things and performing experiments to test the truth of our understanding of the world, earth, air, fire, and water were replaced by the chemical elements that we have today – Hydrogen, Helium, Lithium, Beryllium, Boron, Carbon, and so forth.

Although well educated people never really believed that the earth was flat, there was a time when they did believe that the earth was the center of the universe and that the Sun, planets, and stars all moved around the earth. Soon after people like Galileo began looking at the skies through telescopes, we dropped that idea. Now we believe that the earth and the other planets of our solar system travel around the Sun. The Sun in turn travels around the center of the Milky Way Galaxy and the Galaxies themselves all travel around something.  It seems that there is no real center of the universe. Everything is just in motion around everything else.

These are but two examples of the hundreds of scientific ideas that have changed over the centuries. Things that were once accepted as scientific facts were proven wrong and other ideas took their place.

The reason for this change is that science began to test its ideas with actual experiments. For many centuries, much of what we call science came under the category of philosophy. People would debate one another and come up with their world view. Part of that world view had to do with the way the universe worked. When scientists began to test this world view with actual experiments, they discovered that much about the way we thought the world worked was wrong. Science had to change.

Science struggled long and hard with these changes. The scientific community had to get used to the idea that speculation and debate are not reliable. You must have an external standard. This external standard must tell you that one way is right and the other ways are wrong.