Astronomy units 5,6,7

Copernicus’s major book and year?

De Revolutionibus Orbium Colestium, 1543

What was the Commentariolus?

A private outline of Copernicus’s heliocentric ideas with 7 propositions

Main aesthetic objection to Ptolemy?

Equants broke uniform circular motion

How does heliocentrism explain retrograde motion?

A faster Earth overtakes a slower outer planet, so it appears to loop

Why are Mercury and Venus always near the Sun?

Their orbits are inside Earth’s, so elongation is limited

Copernicus’s answer to “no parallax”?

The stars are extremely far away

Who added the “need not be true” note?

Andreas Osiander

Which observation tests Ptolemy vs Copernicus?

Phases of Venus (Galileo’s Telescope)

Who proposed an infinite Copernican universe?

Thomas Digges

Fate of Giordano Bruno?

Burned at the stake in 1600

What made Tycho special?

The most accurate naked-eye observations (~1 arcminute)

Significance of the 1572 Stella Nova?

No parallax, so it was among the fixed stars, and the heavens could change

Significance of the 1577 comet?

No parallax, so it was beyond the Moon, Its tail points away from the Sun

Name of Tycho’s observatory and where?

A Uraniborg on the island of Hven

Who funded Tycho?

King Frederick II of Denmark

Describe the Tychonic system

Planets orbit the Sun, and the Sun orbits the Earth

Why did Tycho invite Kepler?

His data wouldn’t fit any of the 3 systems, and he needed a mathematician

Tycho’s later job?

Imperial Matheatician to Rudolph II in Prague

Kepler’s first book and idea?

Mysterium Cosmographicum, the 5 platonic solids nested between 6 planets

Why did he abandon circles?

Tycho’s Mars data differed from a circle by 8 arcminutes

First Law?

Orbits are ellipses with the Sun at one focus

Second Law?

Equal areas in equal times, so planets move faster when closer to the sun

Third Law?

P² = A³ (years, AU)

Which book has Laws 1 and 2? Law 3?

Astronomia Nova, Harmonies Mundi

Definition of an Ellipse?

The sum of the distances to 2 foci is constant (d1 + d2 = constant)

Eccentricity formula and range?

e = c/a. A circle is 0 and values near 1 are very elongated

What are perihelion and aphelion?

The closest and farthest points from the Sun

What are the Rudolphine Tables?

Tycho’s data, published by Kepler in 1627

Why was Kepler initially rejected?

People wanted to keep uniform circular motion

Do Kepler’s laws apply beyond planets?

Yes, to anything in a gravitational field