Thursday, April 11, 2013

History of Science -- Part Three: Galileo Galilei

In 1591, at only twenty-seven years of age, Galileo Galilei became a professor at the University in Padua, but he soon left for a post at Florence. Today’s university faculty would understand why: He was offered more time for research and less teaching. (Not me, I prefer teaching!) His talent included music and art as well as science. Brilliant, witty, and charming, Galileo could also be arrogant, brash, and petty. We could envy his skill with words. He liked women, and they liked him. He was, what we call now, a renaissance man.

Galileo was a convinced Copernican. That is, he was certain the Earth revolved around the Sun and not vice-versa. The simpler system made sense to him. But unlike Copernicus, Galileo did not merely claim a new technique for calculation; he argued for a new worldview. A humble approach was not his style.

The Church had to stop Galileo’s call for independent thought — the business of the Church was saving souls, not scientific validity. Found guilty by the Holy Inquisition and given a tour of the torture chambers, Galileo recanted his heresy of a sun-orbiting Earth. For his last years, Galileo lived under house arrest — a lesser penalty than that of Copernican Giordano Bruno, who was burned at the stake.

Recantation not withstanding, Galileo knew that the Earth moved and that Aristotle’s explanation of motion could not survive on a moving Earth. Friction, not desire for rest in the cosmic center, caused a sliding block to stop, and air resistance, not less desire, caused a feather to fall more slowly than a stone.

Contradicting Aristotle’s claims, Galileo asserted, “In the absence of friction or other impressed force, an object will continue to move horizontally at a constant rate.” And, “In the absence of air resistance, heavy objects and light objects will fall at the same rate.”

Galileo’s ideas were obvious — to him. How could he convince others? Rejecting Aristotle’s teaching for the motion of matter was not a minor issue. Aristotle’s philosophy was an all-encompassing worldview. Reject a part, and you appear to reject it all.

To compel agreement with his ideas, Galileo needed examples that conflicted with Aristotle’s mechanics — but that conformed to his own ideas. But looking around, he could see few examples, so he decided to create them!

Galileo would contrive special situations: “experiments.” An experiment tests a theoretical prediction. This may seem an obvious approach to us here in the twenty-first century, but in that day it was an original and profound idea.

In his most famous experiment, Galileo supposedly dropped a ball of lead and a ball of wood from the leaning Tower of Pisa. The simultaneous click of the wood and the thud of the lead proved the light wood fell as fast as the heavy lead. Such demonstrations gave reason enough, Galileo argued, to abandon Aristotle’s theory and to accept his own.

Galileo used inclined planes to “reduce” the acceleration of gravity, and measured the acceleration of objects rolling down the planes measuring time with his own pulse. He also developed early telescopes and made many discoveries including the phases of Venus (further proof of an heliocentric solar system) and discovered the moons of Jupiter as well as sunspots. Through experiments and observations, Galileo was rapidly filling in new science and discarding incorrect theories.

Some faulted Galileo’s experimental method. Though the displayed facts could not be denied, Galileo’s demonstrations were contrived situations, therefore insignificant because they conflicted with matter’s intuitively obvious nature. Moreover, Galileo’s ideas had to be wrong because they conflicted with Aristotelian philosophy. Galileo had a far-reaching answer. Science should deal only with those matters that can be demonstrated. Intuition and authority have no standing in science. The only criterion for judgment in science is experimental demonstration.

Within a few decades, Galileo’s approach was accepted with a vengeance. Science progressed with vigor never seen before. The experimental method had been discovered. The scientific age had dawned.

Now we’re really getting to the “crux of the biscuit.” I know most of my friends are not scientists and mathematicians. That’s OK. I’m writing this series specifically for those people. You may not be a scientist or a technologist, but I’m certain you are aware that we now live in a highly scientific and technological world. It can be very confusing and difficult to understand. I hope this will help you understand.

Science is not politics, it is not philosophy, and it is not religion. Nor is it opposed to any of those concepts. This idea of experimental confirmation is how you “do science.” Let me explain.

Let’s agree on some rules of evidence for accepting a theory as reliable science. They will stand us in good stead when we consider quantum theory and will serve as a test for any ideas that theory might inspire.

But first, a remark on the word “theory.” We speak of quantum theory but Newton’s laws. Why? “Theory” is the modern word. I can’t think of a single twentieth- or twenty-first-century “law” in physics. Plus, Newton’s “laws” have been proven incorrect, replaced — or more specifically, “corrected” by Einstein’s theories and the experiments that demonstrate Einstein’s superiority in cases of high velocity or high gravity. Although “theory” is, at times, used in science for a speculative idea, it does not necessarily imply uncertainty. Einstein's relativity theory is, as far as is known, completely correct. Newton’s laws are an approximation.

For a theory to compel consensus, it must, first of all, make predictions that are testable with results that can be displayed objectively. It must stand with a chip on its shoulder challenging would-be refuters.

“If you truly believe, then you will go to heaven.” That prediction may well be correct, but it is not objectively testable. Religions, political stances, or philosophies in general are not scientific theories. Aristotle’s testable theory of falling — that a two-pound stone will fall twice as fast as a one-pound stone — is a scientific theory, albeit an incorrect one.

A theory making testable predictions is a candidate for being reliable science. Its predictions must be tested by experiments that challenge the theory by attempting to refute it. And the experiments must be convincing, even to skeptics. For example, theories suggesting the existence of extra-sensory perception (ESP) makes predictions, but, so far, tests have not been convincing to skeptics.

To qualify as reliable science, a theory must have many of its predictions confirmed without a single disconfirmation. A single incorrect prediction forces a theory’s modification or abandonment. This scientific method is hard on theories — one strike and you’re out. Actually, no scientific theory is ever totally reliable — it is always possible that it will fail some future test. A scientific theory is, at best, tentatively reliable.

The scientific method, setting high standards for experimental verification, is hard on theories. But it can also be hard on us. If a theory meets these high standards, we are obligated to accept it as reliable science — no matter how violently it conflicts with our intuitions. And that is the rub where quantum mechanics is involved. QM definitely violates our intuitions. Yet the experimental evidence is solid. And that is how we do science.

But, before we can get to these modern theories of how tiny particles that make up atoms and the like work, we need to introduce the giant of Classical Physics, the science that came before Quantum Physics and Relativity.

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