The Copernican Revolution

Nicolaus Copernicus 1473 – 1543

“On the Revolutions of the Heavenly Spheres” – 1543 Proposed a heliocentric model of the universe

Copernicus wasn’t the first to propose a Sun-centered universe. But he published his idea at a time when the world was just about ready for it. Unfortunately, he clung to the ancient idea that the planets must move in perfect circles His model ended up no less complex, and no more accurate, than the Ptolemaic model

Tycho Brahe 1546 – 1601 The most accomplished naked-eye observer ever

Tycho Brahe Lost part of his nose in a duel Party animal Hired a dwarf named Jepp as his court jester Had a pet moose He was also a really bad theorist

Tycho’s pet model: Not pretty! He was willing to allow that the planes went around the Sun, but he insisted that the Sun still went around the Earth.

Johannes Kepler (1571 – 1630) Pretty much the exact opposite of Brahe!

Kepler went to Brahe’s observatory to join his staff, but the two did not get along, and did not trust each other.

Kepler published his model in 1609 in Astronomia Nova (New Astronomy)

Kepler’s First Law: Planets orbit the Sun in ellipses with the Sun at one focus Semimajor axis PerihelionAphelion A planet’s semimajor axis = its average distance from the Sun

Kepler’s Second Law: A line from the Sun to the planet sweeps out equal areas in equal times This says that planets move fastest at perihelion and slowest at aphelion.

Kepler’s Third Law: The square of a planet’s period is proportional to the cube of its average distance

Kepler’s Third Law: The square of a planet’s period is proportional to the cube of its average distance If an asteroid is found whose average distance from the Sun is 5.6 AU, what is its orbital period?

Kepler’s Third Law: The square of a planet’s period is proportional to the cube of its average distance If an asteroid is found whose average distance from the Sun is 5.6 AU, what is its orbital period? 13.3 years

Kepler’s Third Law: The square of a planet’s period is proportional to the cube of its average distance How far away from the Sun is a dwarf planet whose orbital period is 75 years?

Kepler’s Third Law: The square of a planet’s period is proportional to the cube of its average distance How far away from the Sun is a dwarf planet whose orbital period is 75 years? 17.8 AU

At what part of its orbit does Earth move fastest? A) Perihelion B) Aphelion C) It moves at the same speed throughout its orbit

At what time of year does Earth move fastest? A) Summer B) Fall C) Spring D) Winter

Galileo Galilei 1564 – 1642 First person to record his observations of the heavens using a telescope

Observations started in 1609 He observed the four large moons of Jupiter They are now called the “Galilean moons”

He observed the phases of Venus Phases of Venus in a geocentric universe Phases of Venus in a heliocentric universe Clearly, not everything orbits the Earth!

He observed sunspots. He saw that not everything in the heavens is perfect! He observed mountains, valleys, and craters on the Moon.

Galileo’s contributions to our view of the universe were: 1.To show us the utility of telescopic observations 2.To provide evidence supporting the heliocentric model of the universe

Who is credited with showing us how the planets actually move through space? A) Tycho Brahe B) Johannes Kepler C) Nicolaus Copernicus D) Claudius Ptolemy E) Galileo Galilei

Astro-Cash Cab! BRING YOUR CALCULATOR! Andrew Saucedo Alex Torres Marc Ramirez Connor Johnson Colt Allred

1) An asteroid is discovered that takes 5 years to orbit the Sun. What is its average distance from the Sun?

2) Who made the most accurate measurements of planetary positions before the telescope? Galileo Galilei Tycho Brahe Johannes Kepler Claudius Ptolemy Nicolaus Copernicus

3) True or False? Planets further from the Sun move faster in their orbits.

4) Galileo’s contributions to our view of the universe included… Lending observational support to the geocentric model of the universe. Determining that the planets move in ellipses with the Sun at one focus. Publishing a book promoting a Sun-centered universe. Discovering that there are some objects that definitely do not orbit the Earth. Convincing the Catholic church that the Earth is not the center of the universe.