Read an Excerpt

Janice VanCleave's Scientists Through the Ages

John Wiley & Sons

Chapter One

A scientist is someone who observes and/or experiments to discover answers. But a scientist doesn't necessarily need special training or have to be a certain age or sex. A scientist is anyone who searches for answers to scientific questions.

Celestial bodies are the natural objects in the sky, including suns, moons, planets, and stars. Astronomy is the study of celestial bodies in the universe (Earth and all celestial bodies in space regarded as a whole). There is no record of the first astronomers (scientists who study celestial bodies), but they were ancient peoples who looked at the heavens and tried to explain what they saw. These ancient astronomers studied the heavens without the aid of a telescope (an instrument that permits distant objects to be viewed as if they were brighter and closer to the observer). Their universe was what they saw around and above them. They studied the movements of the Sun, the Moon, the planets, and the stars and often used these changes to try to explain events on Earth.

To some ancient peoples, the universe was a mountain rising out of a sea with a dome over it. The dome was lighted by the Sun during the day and by the Moon and the stars at night. Stories such as this, which answer basic questions about the nature of the world or express the beliefs of a group of people, are called myths. Myths generally date before the introduction of writing and were passed orally from one generation to the next. The study of the myths of a particular culture is called mythology.

Astrology is a study that assumes that the positions and the motions of celestial bodies, particularly the Sun, the Moon, the planets, and the stars, at the time of a person's birth affect the person's character and therefore his or her destiny. Astrology is an ancient practice that seems to have developed independently in different civilizations. As early as 3000 B.C., the Chaldeans, who lived in Babylonia (now Iraq), studied astrology. Many scholars viewed astrology and astronomy as complementary sciences until about the 1500s. At that time, the discoveries made by such astronomers as the Polish priest and scientist Nicolaus Copernicus (1473-1543) and the Italian scientist Galileo Galilei (1564-1642) disproved some of the foundations of astrology. Since that time, scientists have considered astrology a pseudoscience (a set of beliefs pretending to be scientific but not based on scientific principles).

The branch of astronomy dealing with the study of the universe as a whole-its distant past and its future-is called cosmology. Many early scientists were Greek philosophers, which, as defined by the ancient Greeks, meant people who search for knowledge for its own sake. Philosophy (the investigation of truth, wisdom, and knowledge) included all areas of instruction, such as art, science, and religion. One famous Greek philosopher, Aristotle (384-322 B.C.), is thought to have been one of the earliest cosmologists (scientists who specialize in cosmology). Aristotle made many observations of the natural world and developed theories to explain things he saw. He was the most influential philosopher in the history of European thought for almost two 2,000 years. Even into the 1600s, Aristotle's theories were considered the truth by the Roman Catholic Church. To disagree with his ideas was considered heresy (an act against the teachings of a church, especially by a person professing the beliefs of that church) and was punishable by imprisonment or death. Galileo disagreed with Aristotle's theories on astronomy and narrowly escaped being killed.

One idea that Galileo disagreed with was Aristotle's geocentric (Earth-centered) theory of the universe, which put a stationary Earth at the center of the universe and had all the other heavenly bodies moving around it. Aristotle wasn't the first to express this idea. In fact, it had been the accepted theory for thousands of years. But since Aristotle agreed with it, it became the accepted theory for almost 2,000 more years. Another accepted idea that Galileo disagreed with was that all heavenly bodies, including the Moon, were perfectly smooth spheres.

Aristotle was a thinker, not an experimenter. He didn't try to prove his ideas. The Greek astronomer and mathematician Claudius Ptolemy, who lived in Alexandria (in Egypt) from approximately A.D. 100 to 170, created a model to explain the motion of celestial bodies in a geocentric universe. Since his model agreed with Aristotle's theory of the universe, its accuracy was basically unchallenged until Nicolaus Copernicus proposed a heliocentric (Sun-centered) model. There were so many unexplained parts to Copernicus's model that the Church didn't take it seriously, but many scientists of the day became interested, including the Danish astronomer Tycho Brahe (1546-1601) and the German astronomer Johannes Kepler (1571-1630). Brahe was at first reluctant to share his discoveries with others for fear they would take credit for his works. But in time Brahe and Kepler shared their ideas and research.

It wasn't easy for anyone to work with Brahe. Brahe once fought a duel with another man over who was the better mathematician. Brahe may have been the best mathematician, but his lack of skill at sword fighting resulted in his losing a part of his nose and having to wear a metal plate over it to hide the missing end.

Brahe and Kepler's combined efforts led to the discovery that planets must have an elliptical (the shape of a slightly flattened circle) orbit (the curved path of one object around another) around the Sun, not around Earth. Previously, it had been believed that the orbits were circular, not elliptical.

In 1609, Galileo started studying the sky with his own homemade telescopes. His observations provided proof of Copernicus's theory of a Sun-centered universe, but Galileo was forbidden by the Church to talk or write about his ideas. However, he had already published them, and other scientists were beginning to agree that the universe was heliocentric. The big missing piece to the puzzle was the force that kept celestial bodies in orbit. The English scientist Sir Isaac Newton (1642-1727) discovered this force, which is called gravity (the force of attraction between all objects in the universe). He worked out equations to explain how gravity affected the motion of celestial bodies. These equations were so accurate that they are still used today.

Newton thought that there were three basic parts of the universe: time, which was the same all over the universe; space, where every object had its own size and position; and mass, the amount of matter (the substance from which all objects are made) in an object, which was constant. Mass is commonly measured in metric units of grams and kilograms. In 1915, the German scientist Albert Einstein (1879-1955) made waves in the astronomical community by disagreeing with Newton's theories. In his theory of relativity, Einstein showed that time, space, and mass were different for observers moving at different velocities in relation to one another. (A theory is an idea or a statement, based on evidence, that explains how or why something happens, but it can be changed as new information is discovered.)

The German-born British astronomers Caroline Herschel (1750-1848) and her brother William Herschel (1738-1822) made many important contributions to astronomy. Among these were eight comets, discovered by Caroline, and the planet Uranus, discovered by William. Comets are small celestial bodies made up of dust, gases, and ices (mainly, water and carbon dioxide) that move in an extremely elongated orbit around the Sun. Comets and planets are natural satellites (celestial bodies that revolve around other celestial bodies).

Caroline Herschel was the first acknowledged woman astronomer, but her accomplishments didn't cause any great changes in the attitude of the scientific community toward women scientists. Yet Caroline's scientific work, as well as that of other women scientists, such as the American astronomer Maria Mitchell (1818-1889), was a model for women scientists who followed. Mitchell was America's first, but certainly was not the last, recognized woman astronomer. Henrietta Leavitt's (1868-1921) astronomy studies made possible the first accurate determination of distances between celestial bodies.

Another modern astronomer is the famous English cosmologist Stephen Hawking (1942-). Hawking's most famous scientific contribution is providing better arguments for the presence of black holes in space. A black hole is thought to be an extremely dense celestial body that has such strong gravity that not even light can escape from it. Since light can enter it but cannot get out, it would appear to be black.

FUN TIME!

Purpose

To confirm Galileo's observations that the Moon is not a perfectly smooth sphere.

Materials

sheet of white copy paper pen ruler binoculars and/or telescope

Procedure

1. Use the paper, pen, and ruler to draw a Moon Data table like the one below.

2. Observe the Moon for as many days as possible during a 29-day period. During each observation, make a diagram of the Moon, shading in the dark areas.

3. Use the binoculars and/or a telescope to study the boundary on the Moon between the dark and the light parts. Make a note on your drawings about how straight or uneven this boundary is.

4. Label your drawings with the names of the different moon phases, as shown.

Results

Your observations should show that the boundary between the light and the dark sides of the Moon is uneven.

Why?

Using a telescope that he made, Galileo studied the Moon phases (regularly recurring changes in the shape of the lighted part of the Moon, facing Earth) and discovered that the boundary between the light and the dark sides of the Moon, called the terminator, was rough and uneven. From this and many other observations made with his telescope, Galileo concluded that the Moon's surface consists of valleys, plains, and mountains, much like the surface of Earth, so it is not perfectly smooth.

MORE FUN WITH THE MOON!

The same side of the Moon always faces Earth because the Moon rotates (turns about an axis-an imaginary line through the center of an object) and revolves (moves in an orbit-a curved path around an object) at the same rate. While the same lunar features are always seen by an observer on Earth, in the Northern Hemisphere (the region north of the equator-an imaginary line around the center of Earth) these features appear to rotate in a clockwise direction during the day. This is because an observer on Earth sees the Moon from a different direction as Earth rotates on its axis. The "Man in the Moon" (or, as seen by some, "The Moon Rabbit") is the design on the Moon that results from shadows made by its different land features. Make note of the position of the design when the Moon is in the eastern part of the sky and then again later when the Moon is in the western part of the sky. If the Moon is in a crescent phase (the lighted part of the Moon that looks like a ring segment with pointed ends), instead of observing its design, note any change in the direction that the pointed ends of the crescent face.

Chapter Two

Biologists are scientists who specialize in biology, which is the study of organisms (living things). In 1800, the French naturalist (a scientist who studies plants and/or animals) Jean-Baptiste de Lamarck (1744-1829) introduced the word biology. Lamarck is also famous for developing a theory of inheritance, which attempted to explain how particular traits (characteristics) are passed down from parents to their offspring (the young of a particular organism). Lamarck's scientific theory of inheritance and his other theories were largely ignored or attacked during his lifetime, and he spent most of his days struggling to make a living. He was so poor that he was buried in a rented grave; after five years his body was removed, and no one knows where his remains are now.

A scientist who studies microbes (tiny organisms visible only under a microscope) is called a microbiologist. The founder of microbiology (the study of microbes) was Antoni van Leeuwenhoek (1632-1723), who prepared his own microscopes and studied everything from blood to scrapings from his teeth. In 1865, the French scientist Louis Pasteur (1822-1895) published his findings that some microbes cause diseases. Pasteur called these disease-causing microbes germs. A later microbiologist who was able to discover a cure for diseases caused by microbes was Alexander Fleming (1881-1955).

One of the earliest detailed studies of organisms was made by the British naturalist Charles Darwin (1809-1882). His renowned studies were made aboard the HMS Beagle, during a British science expedition that traveled around the world from 1831 to 1836. Darwin studied plants and animals everywhere he went. From his studies, he proposed the theory of natural selection, sometimes called "survival of the fittest." This theory is based on the fact that all living organisms compete for things like water, food, and shelter, in order to survive Those organisms with traits best suited for survival live and produce offspring with traits similar to their own. For example, in areas where trees are tall, giraffes with longer necks would compete for food more successfully and would live to produce offspring with long necks like themselves. Genetics is the branch of biology that deals with the study of heredity, which is the transfer of traits (characteristics) from parents to offspring. Geneticists are scientists who study things that deal with heredity.

In the 1900s, the Austrian monk Gregor Johann Mendel (1822-1884) made the greatest single contribution to the study of heredity. Most scientists of that time supported the "blending" theory of heredity, which basically said that hereditary material from both parents blends together in the offspring. Mendel experimentally disproved the blending theory by using plants.

Continues...

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Excerpted from Janice VanCleave's Scientists Through the Ages by Janice VanCleave Excerpted by permission.
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