Who Was Galileo Galilei?
Galileo was a man of many interests. Unlike today's scientists who become experts in very specialized areas, Galileo studied a wide range of topics from mathematics to astronomy to physics. He was also a teacher, inventor, and writer.
Galileo may be best known for opposing the Catholic Church's view that Earth was the center of the universe, but he was in fact a religious person. As a teenager, he attended school in a monastery and dreamed of becoming a monk.
In 1581, Galileo's father sent him to the University of Pisa, Italy, to study medicine. He wanted Galileo to become a doctor so he could make a good living and eventually support his younger siblings. Galileo had other ideas. While at the University, he became fascinated with mathematics. He left the University to become a tutor of mathematics and then a professor.
Galileo next became interested in falling bodies. Whether or not he dropped cannonballs from the Leaning Tower of Pisa is not known, but he did discover that the speed at which objects fall depends on air resistance, not on how much they weigh.
At around this time, Galileo's love for tinkering with mechanical things led to his invention of a simple thermometer, a geometric and military compass, and an improved telescope.
He observed the surface of the Moon and found it to be surprisingly similar to Earth; he witnessed four objects circling around Jupiter (four of its moons); and then he sketched pictures of the changing pattern of spots on the Sun. He proposed, quite rightly, that these sunspots were on the surface of the Sun and that their changing pattern was evidence that the Sun rotated.
Unfortunately, one of the books Galileo published included a strong argument that the Sun and not Earth was at the center of the solar system. This went against church teachings, and Galileo was brought before a church organization known as the Inquisition.
In 1633, the Inquisition placed Galileo under house arrest, where he stayed until he died in 1642. Although Galileo was old and sick at this point, he continued scientific experimentation. Going blind, he could no longer study astronomy. Instead, he returned to his studies on motion. Galileo's studies of inclined planes, falling bodies, projectiles, and other laws of motion became the foundation of modern physics. Throughout his life, Galileo was strongly supported by his eldest daughter, Virginia (Sister Maria Celeste), who entered into a convent in 1613 and corresponded with him regularly.
By following his many interests and pursuing questions that intrigued him, Galileo contributed greatly to science. He made many discoveries in astronomy and laid the foundation for modern physics.
Galileo's Battle for the Heavens.
In a companion Web site, learn about Galileo's life, his place in the world of science, his experiments, and his mistaken belief that Earth's daily rotation and its annual orbit around the Sun trigger ocean tides. www.pbs.org/nova/galileo/
Discover more at your local library.
Astronomy and physics are much different today than they were in Galileo's time. Today's scientists are much more likely to subspecialize in a main area of interest. For example, physicists interested in subatomic objects are called particle physicists. Astronomers interested in the origin of life in the universe are called astrobiologists.
Almost anyone can become a scientist. Here are brief biographies of some of the scientists who are making contributions to astronomy and physics today.
Vera Cooper Rubin
Vera Rubin's interest in stars began when she was 10 years old. Her father helped her build a telescope from scratch and attended amateur astronomy club meetings with her. In the early 1960s, Rubin became the first woman permitted to observe at the Palomar Observatory, which is run by the California Institute of Technology. One of her major contributions to astronomy was finding evidence to support the theory that there may be large amounts of unseen matter, known as dark matter, in the universe.
She is currently an astronomer at the Carnegie Institution of Washington (D.C.) for the Department of Terrestrial Magnetism. In 1993, she was awarded the National Medal of Science. She has four children, all of whom have pursued careers in science. In addition, she has been very active in encouraging women and minorities to pursue science careers.
Neil de Grasse Tyson
Neil de Grasse Tyson is an astrophysicist who has pursued science and spent years helping others understand it.
Tyson first looked up at the sky from the rooftop of his Bronx, New York, apartment house with a pair of binoculars. He was 9 years old. He would later become the youngest-ever director of the Hayden Planetarium at the American Museum of Natural History in New York City. He also spends time as a visiting research scientist in astrophysics at Princeton University, New Jersey.
Since 1995, Tyson has written a monthly essay "Universe" for Natural History magazine. He has also written numerous books to help others understand the universe. His research interests include star formation, exploding stars, dwarf galaxies, and the structure of our Milky Way. He has two children.
Stephen Hawking likes to think big. He spends time working as a cosmologist, a person who studies the origin, present state, and future of the universe. One of his greatest contributions has been in the understanding of black holes, which are thought to be places in space where there is so much concentrated mass that anything nearby is sucked into their gravitational pull.
Hawking has also had to overcome great physical challenges. For most of his adult life, he has had a disease called amyotrophic lateral sclerosis, or ALS. Also known as Lou Gehrig's disease, this illness makes it progressively more difficult to move, speak, breathe, and swallow. Adaptive technologies have allowed him to continue to write and deliver scientific papers and lectures worldwide. He has three children and one grandchild.
Rubin, Vera C.
Women in Astronomy: An Introductory Resource Guide
Tyson, Neil de Grasse
Neil de Grasse Tyson
McDaniel, Melissa and Jerry Lewis.
Stephen Hawking's Web Site
In the Swing of Things
For ages 10 and older.
It is thought that Galileo first started studying pendulums when, in 1583, he watched a suspended lamp swing back and forth in the cathedral of Pisa. He used his pulse to time the swings and discovered that the duration of each swing was the same. This would later become an important concept in regulating clocks. Do this experiment with a pendulum and see whether you can learn what makes it work.
You will need
What to do
Bonnet, Robert L. and Dan Keen.
Galileo's Pendulum Experiments
How Pendulum Clocks Work
You're Getting Very Sleepy
Have you ever seen a hypnotist swing a watch back and forth to put somebody in a very relaxed state? The watch on a chain is a type of pendulum. The idea is that the swinging motion is so regular that the person looking at it will become so entranced that she will be susceptible to anything you tell her. Whether this is true is debatable. But how a pendulum works is not. Galileo discovered the laws under which pendulums work, one of the main principles being that they swing in an almost constant, steady interval. Later, scientists used those principles to design pendulum clocks.
The Tick Tock of a Water Clock
For ages 10 and older.
Water clocks measure time by using the fact that water will flow at a constant rate through a certain size hole. The same amount of water flows into its receiving container every second. By measuring the amount of water in the container, it is possible to measure how much time has passed. In this experiment, you will build a water clock that measures time.
You will need
What to do
A Walk through Time: Early Clocks
Clock a History
Today it is difficult not to be conscious of time. Wall clocks, radio announcements, computer monitors, watches, and cell phones all tell us how much time is passing. Thousands of years ago, measuring time was more difficult. The ancient Egyptians, Greeks, Romans, and Chinese used clocks that depended on nature. For instance, the sundial kept track of the time during daylight hours. To measure smaller increments of time, or when the Sun was not shining, ancient people used different variations of clocks, such as water, sand, or candle clocks.
Support provided by
For new content
visit the redesigned