During the Renaissance, astronomy made great advances. For almost 2000 years, people believed the Earth was the center of the universe based on Greek scientists like Aristotle and Ptolemy. Nicolaus Copernicus proposed the sun-centered model, though few believed him. Galileo greatly improved the telescope and made discoveries like the moon's craters and Jupiter's moons. After his observations, Galileo agreed with Copernicus' model, though the Catholic Church arrested him for this view. Tycho Brahe took precise planetary measurements, and his student Johannes Kepler developed laws of planetary motion and showed planets need not orbit in perfect circles.

1. During the Renaissance people began once again to explore and experiment with the world around them.
One area of science which made great leaps during this time was astronomy. Astronomy is the study of
celestial bodies in outer space such as the Moon, the planets, and the stars.
Earth as the Center of the Universe
For almost 2000 years the people of Europe had relied on the discoveries of the Ancient Greeks. Greek
scientists such as Aristotle and Ptolemy had produced theories that the Earth was the center of the
Universe. They said that the sun and the planets orbited around the Earth. People considered this as a
fact for all that time.
Nicolaus Copernicus
Astronomer Nicolaus Copernicus put forth a new theory during the Renaissance. He said that
the Sun was the center of the universe and that the Earth and the planets orbited the Sun. Of course, he
was right about the Earth and the planets orbiting the Sun, but very few people believed him!
Galileo Galilei
Galileo was one of the greatest scientists in history. A lot of his scientific work was in the area of
astronomy. Galileo was already interested in studying the planets when he heard about the concept of the
telescope. He improved the telescope and constructed one that could be used to observe the planets.
Using his telescope, Galileo was able to make all sorts of new discoveries. He found out that the Moon
was not really smooth, but covered with craters. He also thought that the moon didn't make its own light,
but reflected light from the sun. Other discoveries included the moons of Jupiter, the phases of Venus,
and sunspots.
Galileo Agrees with Copernicus
After recording and studying his observations of the planets and the moon with his telescope, Galileo
believed that Copernicus' theory of the planets, including the Earth, rotating the Sun was correct. He wrote
a famous work that explained why he thought this was the case. The Catholic Church did not agree,
however, and put Galileo under house arrest.
Tycho and Kepler
Two other major astronomers from the Renaissance were Tycho Brahe and Johannes Kepler. Tycho was
a Danish nobleman who took many precise measurements of the planets and stars over a long period of
time. Tycho made many strides in the work of observing the heavens.
Kepler was a German astronomer who worked as Tycho's assistant for a time. Kepler developed the three
laws of planetary motion and supported Copernicus' view of the planets orbiting the Sun. He also charted
the orbit and position of many of the planets showing that they did not need to orbit the sun in a perfect
circle.

2. 1) What types of things do astronomers study?
a) Animals and plants
b) History and philosophy
c) Books and literature
d) Paintings and sculptures
e) Planets and stars
2) What did people think was the center of the universe fornearly 2000 years?
a) The Sun
b) The Moon
c) The Earth
d) The North Star
e) The planet Jupiter
3) What did Galileo do that got him in trouble with the Catholic Church?
a) He invented a telescope that could see the stars
b) He argued that the planets, including the Earth, orbited around the sun
c) He said that there were moons orbiting the planet Jupiter
d) He disagreed with Copernicus
e) He presented a theory on where the light from the Moon came from
4) True or false: When Copernicus explained that all the planets orbited the Sun, pretty much everyone believed
him.
TRUE
FALSE
5) What did Galileo claim was the source of the light of the Moon?
a) It was from an energy source at the middle of the Moon
b) It was from still hot meteors that had crashed into the Moon
c) It was from glowing lichen that grows on the Moon
d) It was sunlight that was reflectedoff the surface of the Moon
e) It was from fires lit by little green men
6) What astronomer showed that the planets did not need to orbit the sun in a perfect circle?
a) Johannes Kepler
b) TychoBrahe
c) Galileo
d) Copernicus
e) Aristotle
7) What tool did Galileo greatly improve so it couldbe used to observe the planets?
a) The microscope
b) The telegraph
c) The telescope
d) The bifocal
e) The pendulum
8) What discovery did Galileo make while studying outer space?
a) That the Moon was coveredin craters
b) The moons of Jupiter
c) The phases of Venus
d) Sunspots
e) All of the above
9) What Renaissance astronomer took many precise measurements of the planets over a long period of time and
had Johannes Kepler as his student?
a) Galileo
b) Copernicus
c) Ptolemy
d) TychoBrahe
e) Aristotle
10) True or false: The Renaissance was a time when many great discoveries were made in the field of astronomy.
TRUE FALSE