On this date in 1642, Galileo Galilei died. At 78 years of age, Galileo was blind and ill, and he had lived the last 8 years of his life under house arrest, although he was permitted to travel to doctors and to receive visitors.
House arrest? For one of the world's greatest scientists?
Galileo believed that the Earth moved around the Sun, rather than the reverse, and this seemed to go against some Biblical passages when interpreted literally. Because of this, there was controversy between Galileo, on one side, and the Pope, the Inquisition, and the Catholic Church, on the other. After a trial, Galileo was found guilty of heresy and placed under house arrest. (The Church has of course since then pardoned Galileo, and apologized as well, in 1992.)
Yesterday marked the 400th anniversary of one of Galileo's achievements: observing some of Jupiter's moons. He didn't immediately know what they were—he labeled them “three fixed stars”—but as he observed the “stars” each night, he realized that they were circling Jupiter. A fourth appeared, as well. Galileo realized that they were moons orbiting another planet just as our moon orbits Earth.
This is one bit of evidence that Galileo was able to use when discussing the old idea that everything circled the Earth—these moons were clearly circling Jupiter, not Earth.
Galileo is credited with pioneering the experimental scientific method, building the first high-powered telescope, discovering the phases of Venus and sunspots, confirming the Copernican theory of the solar system, and developing many key ideas of physics. He demonstrated that the velocity of a falling body is not proportional to its weight (the experiment pictured below), described the parabolic paths of cannonballs, and invented a water pump.
Timeline of the greats
This timeline shows the lifetimes of some of the greats of the time: Michelangelo in green, Shakespeare in orange, Galileo in red, and Newton in purple.
Notice that Galileo was born the year Michelangelo died... and died just a few days after Isaac Newton was born. Using the birth and death years given, can you compute how old each of these men were when they died?
One of my favorite Galileo quotes:
“Mathematics is the language in which God wrote the universe.”Galileo is often called the founder of modern science because, instead of merely sitting and pondering things, he did experiments and measured his data as carefully as he could. He also set up standards of length and time so that others could replicate his experiments at other times and places. But he went further: he used mathematics to reason out laws of motion and so forth.
Star gaze tonight!
Winter can be a great time to watch the skies, since in gets dark early. (Of course, it's not so good when it's cloudy!) Before you head outside, try checking out what you can expect to see. One site is the JPL “up?” videos.
Remember, you can study the skies even without a telescope. Maybe you can borrow a good pair of binoculars?
Do some experiments.
There are some good ideas here (halfway down the page, in blue; the first is called "Lunar Observation").
Do some virtual experiments.
This site has some great interactive demos (on the central panel) on the topics of falling objects, projectiles, inclined planes, and pendulums. Great stuff!