Unit 2 the BIG BANG

Unit 2—THE BIG BANG

This Word document contains ALL of the readings from the unit. All readings include multiple copies at different Lexile levels. You are free to repurpose these materials as needed for your classroom. Please do remember to properly cite Big History as the source. If you modify the text, it will change the lexile level. As always, only print what you need.

Changing Views 2

Ptolemy 2

Galileo 8

Copernicus 21

Newton 31

Hubble 38

Approaches to Knowledge 46

Structure of Scientific Revolutions 55

Henrietta Leavitt 66

Tycho Brahe 73

Science, Theology, & Copernican Revolution 77

The Vatican Observatory 87

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Changing Views

This is a collection of articles that details the changing view of the Universe from geocentric to heliocentric. There is an article on each of these scientists: Ptolemy, Galileo, Copernicus, Newton, and Hubble.

Ptolemy

He studied the stars with his naked eye, and put us at the center of the Universe.

Claudius Ptolemy: An Earth-Centered View of the Universe (1260L)

ByCynthia Stokes Brown

The Earth was the center of the Universe, according to Claudius Ptolemy, whose view of the cosmos persisted for 1,400 years until it was overturned — with controversy — by findings from Nicolaus Copernicus, Galileo Galilei, and Isaac Newton.

An astronomer in ancient times

Claudius Ptolemy lived in Alexandria, Egypt, from about 85 to 165 CE. The city was established by Alexander the Great about 400 years before Ptolemy’s birth. Under its Greek rulers, Alexandria cultivated a famous library that attracted many scholars from Greece, and its school for astronomers received generous patronage. After the Romans conquered Egypt in 30 BCE, Alexandria became the second-largest city in the Roman Empire and a major source of Rome’s grain, but less funding was provided for scientific study of the stars. Ptolemy was the only great astronomer of Roman Alexandria.

Ptolemy was also a mathematician, geographer, and astrologer. Befitting his diverse intellectual pursuits, he had a motley cultural makeup: he lived in Egypt, wrote in Greek, and bore a Roman first name, Claudius, indicating he was a Roman citizen — probably a gift from the Roman emperor to one of Ptolemy’s ancestors.

A geocentric view

Ptolemy synthesized Greek knowledge of the known Universe. His work enabled astronomers to make accurate predictions of planetary positions and solar and lunar eclipses, promoting acceptance of his view of the cosmos in the Byzantine and Islamic worlds and throughout Europe for more than 1,400 years.

Ptolemy accepted Aristotle’s idea that the Sun and the planets revolve around a spherical Earth, a geocentric view. Ptolemy developed this idea through observation and in mathematical detail. In doing so, he rejected the hypothesis of Aristarchus of Samos, who came to Alexandria about 350 years before Ptolemy was born. Aristarchus had made the claim that the Earth revolves around the Sun, but he couldn’t produce any evidence to back it up.

Based on observations he made with his naked eye, Ptolemy saw the Universe as a set of nested, transparent spheres, with Earth in the center. He posited that the Moon, Mercury, Venus, and the Sun all revolved around Earth. Beyond the Sun, he thought, sat Mars, Jupiter, and Saturn, the only other planets known at the time because they were visible to the naked eye. Beyond Saturn lay a final sphere — with all the stars fixed to it — that revolved around the other spheres.

This idea of the Universe did not fit exactly with all of Ptolemy’s observations. He was aware that the size, motion, and brightness of the planets varied. So he incorporated Hipparchus’s notion of epicycles, put forth a few centuries earlier, to work out his calculations. Epicycles were small circular orbits around imaginary centers on which the planets were said to move while making a revolution around the Earth. By using Ptolemy’s tables, astronomers could accurately predict eclipses and the positions of planets. Because real visible events in the sky seemed to confirm the truth of Ptolemy’s views, his ideas were accepted for centuries until the Polish astronomer, Copernicus, proposed in 1543 that the Sun, rather than the Earth, belonged in the center.

After the Roman Empire dissolved, Muslim Arabs conquered Egypt in 641 CE. Muslim scholars mostly accepted Ptolemy’s astronomy. They referred to him as Batlaymus and called his book on astronomyal-Magisti, or “The Greatest.” Islamic astronomers corrected some of Ptolemy’s errors and made other advances, but they did not make the leap to a heliocentric (Sun-centered) universe.

Ptolemy’s book was translated into Latin in the 12th century and was known asThe Almagest, from the Arabic name. This enabled his teachings to be spread throughout Western Europe.

We know few details of Ptolemy’s life. But he left one personal poem, inserted right after the table of contents inThe Almagest:

Well do I know that I am mortal, a creature of one day.

But if my mind follows the wandering path of stars

Then my feet no longer rest on earth, but standing by

Zeus himself, I take my fill of ambrosia, the food of the gods.

Claudius Ptolemy: An Earth-Centered View of the Universe (1090L)

ByCynthia Stokes Brown, adapted by Newsela

Ptolemy's view of the earth-centered view of the cosmos persisted for 1,400 years. Only until findings from Nicolaus Copernicus, Galileo Galilei, and Isaac Newton was it overturned.

An astronomer in ancient times

Claudius Ptolemy lived in Alexandria, Egypt, from about 85 to 165 CE. The city was founded by Alexander the Great. Under its Greek rulers, Alexandria developed a famous library that attracted many scholars from Greece, and its school for astronomers received generous funding. After the Romans conquered Egypt in 30 BCE, Alexandria became the second-largest city in the Roman Empire, but less money was provided for astronomy. Ptolemy was the only great astronomer of Roman Alexandria.

Ptolemy was also a mathematician, geographer, and astrologer. Along with many intellectual interests, he had many different cultural influences in his life. He lived in Egypt, wrote in Greek, and had a Roman first name, Claudius, which showed he was a Roman citizen.

A geocentric view

Ptolemy collected and summarized Greek knowledge of the known Universe. His work enabled astronomers to pinpoint the planets and predict solar and lunar eclipses. Because of this, his ideas were accepted by Byzantine, Islamic and Europe scholars for more than 1,400 years.

This idea of the Universe did not fit exactly with all of Ptolemy’s observations. He was aware that the size, motion, and brightness of the planets varied. So he incorporated Hipparchus’s notion of epicycles to work out his calculations. Epicycles were small circular orbits around imaginary centers on which the planets were said to move while making a revolution around the Earth. By using Ptolemy’s tables, astronomers could accurately predict eclipses and the positions of planets. Because real visible events in the sky seemed to confirm the truth of Ptolemy’s views, his ideas were accepted for centuries. They only came into doubt when the Polish astronomer, Copernicus, proposed in 1543 that the Sun belonged in the center – not the earth.

Ptolemy’s book was translated into Latin in the 12th century and was known asThe Almagest, from the Arabic name. This enabled his teachings to be spread throughout Western Europe.

We know few details of Ptolemy’s life. But he left one personal poem, inserted right after the table of contents inThe Almagest:

Well do I know that I am mortal, a creature of one day.

But if my mind follows the wandering path of stars

Then my feet no longer rest on earth, but standing by

Zeus himself, I take my fill of ambrosia, the food of the gods.

Claudius Ptolemy: An Earth-Centered View of the Universe (890L)

ByCynthia Stokes Brown, adapted by Newsela

The Earth was the center of the Universe, according to Claudius Ptolemy. His view of the cosmos was accepted for 1,400 years. Later, Nicolaus Copernicus, Galileo Galilei, and Isaac Newton contradicted Ptolemy’s ideas.

An astronomer in ancient times

Claudius Ptolemy lived in Alexandria, Egypt fromabout 85 to 165 CE. Alexandria was established by Alexander the Great about 400 years before Ptolemy’s birth.

Under its Greek rulers, Alexandria had a famous library that attracted many scholars from Greece. Its school for astronomers received generous support.

After the Romans conquered Egypt in 30 BCE, there was less funding provided for scientific study of the stars. Ptolemy was the only great astronomer of Roman Alexandria.

Ptolemy was also a mathematician, geographer, and astrologer. Along with many intellectual interests, he had many cultural influences. He lived in Egypt, wrote in Greek, and had a Roman first name, Claudius, which showed he was a Roman citizen.

A geocentric view

Ptolemy collected and summarized Greek knowledge of the known Universe. His work allowed astronomers to predict eclipses of the sun and moon, and the positions of planets. His view of the cosmos was accepted for more than 1,400 years in the Byzantine and Islamic worlds and throughout Europe.

Ptolemy accepted Aristotle’s idea that the Sun and the planets revolve around a spherical Earth. This is called a geocentric view. Ptolemy developed this idea by observing the sky and using mathematics.

Aristarchus of Samos lived in Alexandria about 350 years before Ptolemy. Aristarchus claimed that the Earth revolves around the Sun. He couldn’t produce any evidence to support his view, and Ptolemy rejected it.

Ptolemy made observations of the stars and planets with his naked eye. He imagined a Universe with Earth in the center. Around Earth was a set of transparent spheres. He thought that the Moon, Mercury, Venus, and the Sun all revolved around Earth. Past the Sun were Mars, Jupiter, and Saturn. Past Saturn was a final sphere that had all the stars attached to it. This final sphere revolved around the other ones.

This idea of the Universe did not fit exactly with all of Ptolemy’s observations. He knew that the size, motion, and brightness of the planets changed. Ptolemy solved this problem by borrowing a centuries-old idea from Hipparchus. The idea was epicycles: mini-orbits that the planets made while revolving around the Earth.

Astronomers could accurately predict eclipses and the positions of planets by using Ptolemy’s tables. His ideas were accepted for centuries because real visible events in the sky seemed to confirm his views. But in 1543, the Polish astronomer Copernicus proposed that the Sun, not the Earth, belonged in the center.

Ptolemy’s book was translated into Latin in the 12th century. It was known asThe Almagest, from the Arabic name. This allowed his teachings to be spread throughout Western Europe.

We know few details of Ptolemy’s life. But he left one personal poem, inserted right after the table of contents inThe Almagest:

Well do I know that I am mortal, a creature of one day.

But if my mind follows the wandering path of stars

Then my feet no longer rest on earth, but standing by

Zeus himself, I take my fill of ambrosia, the food of the gods.

Claudius Ptolemy: An Earth-Centered View of the Universe (780L)

ByCynthia Stokes Brown, adapted by Newsela

Claudius Ptolemy was an ancient astronomer who studied the skies with his naked eye. He believed the Earth was at the center of the Universe. This view was accepted for 1,400 years until Nicolaus Copernicus, Galileo Galilei, and Isaac Newton came along.