Bob Doyle, Columnist
Every summer, I teach two physics classes that I find enjoyable. The first course is about motion, forces, rotation, orbits, fluids and heat. The second course covers waves, light, electricity and magnetism.
Since I’ve been doing this for two decades, I’ve tried many teaching ideas. I hope that by the end of each course, my students will understand how physics principles apply to their own lives.
I’ve found a small book that explains the basic features of physics to an interested reader. This book is not loaded with equations, which tends to put off most readers. The title is “E = m x c squared: Simple Physics” by Jeff Steward, a Reader’s Digest book, published in 2010 with ISBN 978-1-60652-167-0.
First, I should explain what E = m x c squared means. E stands for Energy, m is mass and c is the speed of light, which is multiplied by itself. Since the speed of light is huge (300 million meters/second), the squared value in the metric system (9 followed by 16 zeroes) makes the U.S. National Debt in dollars look puny.
Einstein in his Special Theory of Relativity showed the conversion of mass into energy yields a tremendous amount of energy, far greater than any chemical reactions. One grain of sand (with a mass of 1 millionth of kilogram) converted to energy, yields 90 billion Joules of energy.
Each day an average American takes in 9 million Joules of chemical potential energy by eating and drinking. The energy in 1 sand grain is 10,000 times the energy of three meals by each of us.
The energy released by mass conversion is used in nuclear reactors, nuclear bombs and stars. Our sun each second converts 4 million tons of matter into energy. (A Joule is the energy needed to move a 1/4 lb. object (such as a small apple) upward 1 meter.)
Now what makes physics so powerful is that it can tell us about how the universe came about, the formation of the first atoms, the first stars, how our solar system arose and why our planet has conditions favorable for life as we know it.
Physics is a collection of the Laws of Nature. Physics has allowed us to develop many different types of technology, especially computers, cell phones, air conditioners, our car engines… the list goes on and on.
Physics started when Greek thinkers about six centuries before Christ decided that events in nature (lightning, Earthquakes, driving rainstorms, droughts) weren’t caused by irritable deities but due to natural principles that we could learn and understand.
Unfortunately, these same Greek thinkers felt that the mind alone could reveal these natural principles; carefully recorded observations or experiments were not needed.
One Greek thinker named Thales believed that earthquakes were caused by the sloshing of water; Thales believed that Earth floated on a huge ocean, so as big waves hit the coast, the Earth would shake.
Probably the most mistaken conclusion by the Greeks was their agreement on an Earth centered universe (the geocentric model) where all the celestial bodies moved around the Earth each day.
The Greeks reasoned that if the Earth moved, we would feel Earth’s quivering or shaking. If the Earth rotated, there would be a strong prevailing wind that would blow all trees down and make normal life impossible. For 1,500 years, this model was accepted by all educated people.
A careful reading of the Bible indicated that the Earth was a very special place where God looked down to watch his creations, especially humans who struggled to follow his laws.
Not all the Greeks accepted this model, but the sun centered model of Aristarchus was ridiculed. If the Earth moved about the sun, it would cause the star groups to grow and shrink in size.
The constellations would grow as the Earth moved towards them and then shrink as it we moved away from them. (The stars are vastly far away, so the Earth’s motion around its orbit would not produce a noticeable change in the star group’s appearance.)
Then in the 15th century, a Polish cleric named Copernicus proposed a sun centered system as being simpler. The central body, the powerful sun could be seen as a representation of a mighty God controlling his planetary children.
Five decades later, Galileo was first to turn a telescope on the heavens and drew what he saw. Galileo’s telescopic observations of Venus’ changing shapes (like our moon) indicated that Venus must orbit the sun rather than the Earth. Then there were four moons orbiting Jupiter, an insult to our planet that has only one moon!
Kepler, a contemporary of Galileo showed that the planets move elliptically about the sun, allowing great precision in predicting their positions. Six decades later, Newton’s great work, the Principia was published. The Principia stated principles that allowed Newton to derive Kepler’s laws as following from his Law of Gravitation.
Slowly over Europe, the Earth centered model was dropped by scientists and universities. So with this abandonment of the geocentric model, physics began its real start, relying on predictions to test any proposed explanations.
SKY SIGHTS AHEAD: The moon is now a crescent in the dawn sky. Late in the morning of June 8, the moon will swing from the morning to the evening side of the sun (New Moon). Starting June 10, the moon will return to the evening sky, appearing near the brilliant planet Venus low in the western dusk that evening.
You now can see both Venus and Mercury in the 9:15 p.m. twilight. On Wednesday, June 12, Mercury will reach its greatest angle from the sun.
Bob Doyle invites any readers comments and questions. E-mail him at firstname.lastname@example.org . He is available as a speaker on his column topics.