Every Day Is Special: January 8 - Celebrate Galileo!

January 8 - Celebrate Galileo!

Posted on January 8, 2021

This post is an update of the 1/8/2010 post:

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 - but it took it's sweet time! The pardon and apology occurred in 1992!!)

Galileo's achievements

January 7 marks 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.

Above, this is something like what Galileo was able to
see as he looked at Jupiter. The four "fixed stars" that
always seemed to be near Jupiter were, as Galileo
realized, moons that orbited Jupiter rather than the
Earth. In modern times, we have sent robotic space
probes past Jupiter, and we have managed to get some
close-up photos of these four moons - which are called
the Galilean moons.

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 website is Space.com.

Remember, we are used to seeing fantastic photos of space stuff...but many of these photos come from space probes or telescopes launched into space, out of Earth's atmosphere!

You will not be able to see these sorts of gorgeous nebulae in your home telescope - but you will see the Moon more up-close-and-personal, and you can even learn to take rad pix like this one:

And you can study the skies even without a telescope. Maybe you can borrow a good pair of binoculars? If so, you may get the sort of peek into the heavens that Galileo had with his telescopes!