Elliptical Orbits

530–400 BCE

The works of Pythagoras and Plato have persuaded Kepler that mathematics can be used to explain the cosmos.

1543

Although Copernicus' sun-centered universe aids in the visualization of a physical solar system, it still provides no information regarding the precise contours of planetary orbits.

1600

Tycho Brahe persuades Kepler that his planetary observations are accurate.

Tycho Brahe

In 1600, he persuades Kepler that his planetary observations are accurate.

1687

Isaac Newton understands that the planets follow Kepler's laws because of the inverse square law of gravitational force.

Isaac Newton

In 1687, he understands that the planets follow Kepler's laws because of the inverse square law of gravitational force.

1716

Edmond Halley transformed Kepler's ratios of planetary distance from the sun into absolute values using observations of the transit of Venus.

Edmond Halley

He transformed Kepler's ratios of planetary distance from the sun into absolute values using observations of the transit of Venus.

astrologers

Before the 17th century, all astronomers were also ____.

Astrologers

They made predictions based on the assumption that the planets moved in predictable patterns around a central object.

ecliptic

The planets, the sun, and the moon always appeared in a particular band of the sky known as the _____.

20

To improve the predictive tables, Tycho Brahe observed the celestial bodies for ____ years.

ellipse

In 1608, Kepler discovered the solution, which called for giving up both circles and constant velocity — this occurred when planets made an ____.

Eccentricity

A particular type of stretched-out circle, where the degree of stretching is quantified.

First Law of Planetary Motion

The motion of the planets is an ellipse with the sun as one of the two foci.

Second Law of Planetary Motion

A line between the planet and the sun sweeps out equal areas at equal times.

Astronomia Nova

In 1609, Kepler published ____ where he mentioned the two laws.

11 times

In Tycho's data set, Mars orbited the sun about ____, with an orbital period of just 1.88 Earth years.

Third Law of Planetary Motion

The square of the orbital period was proportional to the cube of the planet’s average distance from the sun.

Harmonices Muni

In 1619, Kepler included the third law in his book ______ — this book took him 20 years to produce.

specific regular "platonic" solid

A ________ inscribed and circumscribed the sun-centered spheres that contained each planetary orbit.

gravitational force

About 70 years later, Isaac Newton's theories brought about the notion that the movements were caused by a ______.

Astronomiae Pars Optica

Kepler made significant contributions to the field of optics as well, and his 1604 book _____.

Somnium

A book written by Kepler that explores space travel to the moon and what to expect there.

Epitome Astronomiae Copernicanae

This is Kepler’s most influential publication.

Rudolphine Tables

These tables of predicted planetary positions aided him greatly in the production of his well-paid calendars between 1617 and 1624.