Announcements

• 1st Quarter Observing Night Wednesday night. Set-up starts at 6:45pm. We will be in the SSC Atrium as the temperature will be too cold to be outside. If the skies are clear we will set-up a couple of Dobs outside for a quick look.

Nicholas Copernicus

• 1473 – 1543

• The Sun is the center

• Mathematical model no better than Ptolemy’s

• Model had predictive power

• Watch video from Museo Galileo on the Copernican System

The Copernican Universe

The Sun is at the center of the solar system and Earth is just another planet going around it. The only thing

that goes around Earth is the Moon.

Copernicus publishes his book in the year he dies

De Revolutionibus Orbium Coelestium is published in 1543 and the first printing is delivered to him on his death bed. He had delayed publication for fear of excommunication. Original foreword by a local priest claimed that Copernicus didn’t really believe the Sun was the center, just that it was a mathematical model.

Tycho Brahe: last great naked-eye astronomer

• 1546 – 1601

• Made detailed observations of Mars

• Observed a “nova stella”

• Doesn’t believe in the Copernican model but doesn’t like the Ptolemaic model either.

The Tychonic Solar System

Tycho’s Uraniborg and Stjerneborg

Tycho’s Mural Quadrant

Tycho directs while his apprentices make the observation, read the scale and record the measurements. Others work elsewhere on calculations and instrument making

Johannes Kepler

• 1571 – 1630

• Hired by Tycho Brahe in 1600 to do calculations on the orbit of Mars

• Appointed Imperial Astronomer after Tycho’s death

Rudolphine Tables

As part of his duties as the Astronomer Royale for the Holy Roman Emperor, Kepler was to recalculate the positions of the planets. He did so using his three Laws of Planetary Motions. The book was eventually published in 1627 after several legal battles with Tycho’s heirs

Watch Mechanical Universe Kepler’s Laws video

Kepler’s 1st Law

The planets move in elliptical orbits with the Sun located at one focus

The Law of Ellipses

Major change since everyone that came before had used circles, including Copernicus

Kepler’s 2nd Law

A line drawn from a planet to the Sun will

sweep out equal areas in

equal time periods

The Law of Areas

Kepler’s 3rd Law

The Law of Harmonies

The ratio of the square of the orbital period to the cube of the orbital semimajor axis (the radius) is the same for all the planets

Galileo Galilei

• 1564 – 1642

• First to turn the telescope skyward

• Developed new physics to replace the physics of Aristotle

• Got into deep trouble with the Catholic Church

Galileo’s first major

discovery concerned the planet Jupiter

Over a week long period in January 1610 he makes observations that prove the existence of four moons orbiting Jupiter.

Another of his observations that support the Copernican views is the

phases of Venus

In late 1632, Galileo’s book Dialogues is banned and he is put

on trial by the Inquisition

In June 1633 he is found guilty and sentenced to prison. After recanting

his views, his sentence is commuted to house arrest

If you ask a physicist, Galileo’s most important contributions

were in mechanics