[This Commentary originally appeared in the October 11, 1990 issue of The Mendon-Honeoye Falls-Lima Sentinel.]
One hundred and eighty six thousand miles per second. It takes light about one and one-third seconds to go from the Earth to the Moon. We know this because scientists have shot lasers at the reflectors the Apollo astronauts left on the lunar surface. The Moon orbits at a distance of 240,000 miles from the Earth.
One hundred and eighty six thousand miles per second. The light emitted from our Sun has aged a little over eight minutes by the time it hits the Earth. The Earth circles the Sun from a span of 93 million miles away.
One hundred and eighty six thousand miles per second. That’s equal to nearly six trillion miles in one year. We refer to this distance as one light-year. The nearest star (Proxima Centauri) looms a mere 4.3 light-years from our Solar System. That translates to just under twenty-six trillion miles. That’s the closest star.
By the way, most teachers say Alpha Centauri is the closest star. Actually, Alpha Centauri represents the closest star we can see from Earth without the aid of a telescope. Proxima Centauri orbits Alpha Centauri in the same way the Moon orbits the Earth. The heavenly dance between these stars (actually, a third star is involved) puts Proxima Centauri about one third a light-year (or two trillion miles) closer to the Earth than Alpha Centauri. Proxima Centauri, though, does not shine bright enough to see from Earth without a telescope; hence, Alpha Centauri gets all the press.
Now, before we go any further, I should state immediately we will not be discussing wave-particle duality in today’s commentary. (If you wish to know more about the fascinating subject of wave-particle duality, just ask me about it next time you see me.) We’ll merely comment on the concept of the speed of light.
Albert Einstein made the then remarkable assertion that light travelled at the same speed all the time. His bold remark helped explain the results of the famous experiment made by two American physicists in the latter part of the nineteenth century.
A.A. Michelson and E.W. Morley wanted to prove an invisible ether existed through which the Earth – and everything else in the universe – moved. They set up an elaborate system of mirrors which reflected a beam of light. In the system, sometimes the light would go “upstream” and sometimes it would go “downstream” relative to the current of the hypothetical ether.
These two guys figured light, just like boats, would travel slower when moving upstream and faster when moving downstream. They also figured, when they showed this, they would prove beyond a shadow of a doubt the mysterious ether existed. Everybody rooted for the two Americans, because everybody wanted this ether to exist, (its existence would help explain a lot of things).
The first time Michelson and Morley tried this experiment, the velocity of light stayed the same whether it traveled upstream or downstream. They guessed something went wrong with the equipment. They tried the experiment several more times, each time getting the same consequences. They had no choice but to tell everybody.
The outcome of the experiment confused the world of science. Still, scientists continued to believe the ether really existed. They just thought the experiment showed light possessed special enigmatic properties. They tried to explain the results not by fooling around with the concept of ether, but by changing the way we looked at light. All these noble schemes failed either in the mathematical rigors of the blackboard or in the physical realities of the laboratory.
Then along came an irreverent patent clerk. Albert Einstein shocked the staid world of physics by drawing the following conclusion from the Michelson-Morley experiment: Michelson-Morley did not prove the existence of the ether because the ether did not really exist. Einstein then surprised the whole world by inventing and applying the mathematics of the Theory of Relativity to prove his point.
The fact light travels at the same speed all the time represents one of the cornerstones of the Theory of Relativity. It causes us to reject the everyday practicality of the Galilean Transformation (which Sir Isaac Newton institutionalized in Principia).
A Galilean Transformation can be easily explained. Suppose you walk on a train at five miles per hour in the same direction which the train moves. The train travels at sixty miles an hour. A Galilean Transformation would simply add the two speeds (60 mph + 5 mph = 65 mph), which means you are moving sixty-five miles per hour relative to the ground.
You can’t do this with light. A beam of light always moves at 186,000 miles per second. It doesn’t matter if you’re on the ground, in a train or in a rocket. (Unfortunately, for you Doubting Thomases, proving this requires more than two newspaper columns worth of math, so you just have to trust Einstein on this one.)
The real killer of the whole idea, though, deals with Einstein’s proof that nothing can go faster than the speed of light. This really irks science fiction writers, who have to invent all these fascinating – and entertaining – excuses whenever one of their characters travels faster than light.
Yet, a renegade group of physicists today believe one day someone will show even Einstein can be wrong. They feel the speed of light can be broken just like the speed of sound. If they’re right, then all H-E-double toothpicks will break loose!
Next Week #80: EDITORIAL (originally published on October 4, 1990)
Next Week #82: Penalize Colorado! – Ethics Begins on the Football Field (originally published on October 18, 1990)
[What is this and why is here? See Interested in Discovering My Time Machine? for more details.]