Renaissance Scientists And After - Part II

Galileo Galilei was another man of the Italian Renaissance, gifted with brilliant, many-sided genius. He made so many discoveries and explained them so clearly that he has been called the "father of experimental physics."

Most of us have heard of his discovery of the principle of the pendulum and his important work in astronomy.

Galileo was a dramatic genius, but his ideas were too bold, too modern for many people of his day. This man's life shows that the whole period in which he lived was kind of a bridge.

Some minds still looked backward to the past, and were reluctant to accept new knowledge. While others were charged with the excitement of learning. Galileo belonged to the latter group.

Some authorities in the past thought and even today think that Galileo's work in other branches of science was even more important than his astronomical work.

He invented the first thermometer, using air (where we would now use mercury) in a glass bulb. The ancients had said "nature abhors a vacuum," but Galileo is said to have remarked that nature apparently does not abhor a vacuum above thirty-four feet, since he found that no suction pump, however powerful could raise water above that distance.

He knew that it does not take any force to keep objects moving. He also knew that force is needed only to start motion or change its direction.

The Belgian doctor, Jan Baptista van Helmont made many valuable discoveries and at the same time clung to old errors.

He invented the word "gas" to describe the bubbles he saw rising in fermenting beer and from vinegar in which he had dropped shells. He thought this gas was made of water.

In a famous experiment Van Helmont grew a tree in a pot. After five years he dug up the tree. He found it had gained one hundred and sixty-four pounds and two ounces.

Since the soil had lost only two ounces in weight, Van Helmont decided that all the rest of the gain had come from the distilled water he had used to moisten the soil.

What he did not know was that some of the weight had come from a gas in the air (the same gas he had seen in fermenting beer!).

Van Helmont still believed that a way might be found to transmute mercury into gold, but in the years after his time this notion was gradually given up, and the study of chemistry went forward.

Beginning in 1606 a sort of professorship of chemistry was established in France and public lectures were given at the Botanical Garden in Paris.

One of these French chemists, Nicolas Lemery wrote a five hundred page textbook, Course In Chemistry, in 1675. This made the author a fortune. Lemery made a miniature volcano by burying moistened sulphur and iron in a heap of earth.

After a while, the two elements combined, cauing heat which turned the water to steam and presently there was a volcanic eruption on a small scale.

William Harvey is remembered as the man who first explained the circulation of the blood as we now understand it.

He was born in Folkestone, England, the eldest of seven children.

William was small, with black eyes, black hair and a quick and alert manner. After studying at Cambridge and then in Italy under Fabricius (who demonstrated the valves in the veins), Harvey became royal physician in England.

Thus, he had the opportunity to examine the hearts of animals wounded in the chase, being the first man since Galen to work in this way.

In his experiments, Harvey measured the amount of blood which passed by a spot on the release of a ligature and realized that far more blood was pumped in an hour by the heart than the whole body contained.

Therefore, he concluded, the blood must circulate and return. Lacking a microscope, he could not prove the passage of blood from arteries to veins.

Ten years after his death, Malpighi showed this capillary connection in the lung of a frog.

Harvey was one of the most modest of scientists, giving great credit to his predecessors, and scarcely claiming that his great discovery was original.

Evangelista Torricelli, a pupil of Galileo, was the first to construct a mercury barometer and to prove that the air exerts pressure. Aristotle had said that air has no weight or pressure.

Another early worker on the problem of air pressure was Otto von Guericke of Magdeburg, Germany, who invented the air pump and carried out ingenious experiments with vacuums.

• He discovered that "a clock in a vacuum cannot be heard to strike.
• He learned that a flame dies out inside a vacuum.
• He learned that a bird inside a vacuum who opens it's bill wide, struggles for air, and dies.
• He discovered that fish perish in a vacuum.
• He learned that grapes can be preserved for six months in a vacuum.

In his most striking experiment, he had two hollow metal hemispheres placed tightly together.

Through a pump attached to this globe, he drew out the air -- so that inside the globe there was a vacuum.

One day, in an open field with Emperor Ferdinand III and a group of distinguished persons watching the show, he hitched horses to the two hemispheres.

Not until sixteen horses attached to each side stained their utmost could the hemispheres be pulled apart. The air, pressing against the hemispheres from all sides held them together (since there was no air inside to equalize the pressure).

Yet, when Guericke turned a valve in the air pump, letting air flow into the globe, the two hemispheres could easily be separated by one man.

It is not easy to explain the great work of Rene Descartes. He was the author of the first textbook of physiology, the originator of the branch of mathematics called analytical geometry, and one of the world's greatest philosophers.

Descartes was born near Tours, France, to wealthy parents. A sickly youth, he was allowed to do about as he pleased. He formed the habit of sleeping late and he claimed that he thought out most of his scientific problems in bed.

Although sickly, he stated that he intended to die of old age. However after a lifetime of getting up late and pampering himself, he accepted an appointment from the Queen of Sweden.

Lessons in philosophy were to begin at five in the morning. The strain was too much. After one winter of getting up early in a cold climate, he developed inflammation of the lungs and died soon after, at the age of fifty-four (or so the story goes).

Blaise Pascal was a French man of the Renaissance. He was a philosopher, a student of mathematics and of science. He was ill nearly all of his short life, but he made important discoveries in mathematics and science.

He heard of Torricelli's mercury barometer, and he went further. He decided that if the mercury in the barometer was forced up the tube by the pressure of air, there should be less air at a high altitude and therefore the pressure should be less and the column of mercury shorter.

At Pascal's request his brother-in-law climbed a mountain, the Puy-de-Dome, and to Pascal's delight they found that the mercury dropped three inches during the ascent.

Among other discoveries, Pascal found that fluids transmit pressure without loss. This is called Pascal's law of fluid pressure. Every time you use a hydraulic jack to day to raise your car with only a slight effort, you have a demonstration of Pascal's law.

Robert Boyle, born in Munster, Ireland, spent most of his life at Oxford and in London. A Frenchman, Rey, had already shown that metals increase in weight when burned.

Boyle confirmed this and found that a candle would go out and a mouse die in a vacuum in about the same time.

He also showed that even fishes require air (dissolved in water).

Apparently Boyle was the first to produce the gas hydrogen by treating iron filings with mineral acid.

Boyle's greatest discover was what is known as Boyle's Law:

"If we double the pressure on any gas, the volume shrinks to one-half. If we reduce the pressure by one-half, the volume (amount of space occupied) doubles, if the temperature remains the same."

One of the greatest problems of early chemistry was that of burning. When wood burns the ashes weigh less than the wood.

However, when metals burn, the resulting "calx" weighs more than the metal. Why?

Johann Becher, thought that something was given off whenever a solid burned.

Then, there was Ernest Stahl, physician to the King of Prussia, who called this something "phlogiston."

The phlogiston theory seemed to explain many things, but since metals gained weight when they burned, it was assumed that phlogiston was a substance which weighted less than nothing.

Chemists continued to believe in this strange theory until the time of the French Revolution, when it was overthrown by Lavoisier.

Robert Hooke was an Englishman, a mathematician. He put some lenses together to make a microscope and with it was able to see the cell walls in cork.

He was the one who named these tiny structures cells. He believed that light is a series of waves, or vibrations.

Back in the third century, another scientist, Euclid believed that vision was due to particles sent out from the eye. One of the first scientists to form a theory of light resembling the modern known science in this area was Christian Huygens of Holland, who decided (as had already been suggested by Robert Hooke) that light is a series of waves.

By this means he explained the refraction (or bending) of light when it goes from one medium, such as air, into another, such as water or glass.

All our microscopes and telescopes are due to this fact that light changes its direction when it goes from air to glass or glass to air.

Finally, the Dane, Olaus Roemer studying the moons of Jupiter, concluded that it takes light a definite length of time to travel a given distance.

Roemer estimated that the speed of light, getting a figure surprisingly near the truth.