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Here you can watch video lectures on astronomy topics. Watch one of 29 individual playlists, or use the Wikimap to find similar topics.

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Articles related to: Retrograde Motion  Read article

1. Formation of Satellites  Read article

Satellites or moons in the solar system have diverse properties and several different types of origin. The most important process is similar to the accretion that formed the planets themselves. Each of the four giant planets in the outer solar system was massive enough to attract gas from the sola...

2. Orbit of Uranus  Read article

Uranus has two very unusual aspects to its orbit. The first is the large degree of tilt of the spin axis with respect to the plane of its orbit around the sun. This tilt is ninety-eight degrees, so the pole of Uranus is essentially in the plane of its orbit around the Sun. This is more extreme ev...

3. Triton  Read article

Neptune's Triton is the seventh largest moon in the solar system. With a diameter of 2,700 kilometers it's somewhat larger than Pluto. It has an unusual retrograde or backwards orbit of the planet which probably indicates that it was captured from interplanetary space somewhere during the history ...

4. Copernicus  Read article

The man responsible for the Copernican revolution was born in Poland. He was widely read, a master of Greek and Latin, a doctor of law, and a doctor of philosophy, and a doctor of medicine. This highly educated man was also a minor official in the Catholic Church. Copernicus adapted the heliocent...

5. Orbit Inclination  Read article

For most planets in the solar system the orbital inclination is very small. That is, the axis defined by the north and south poles of the planet is almost exactly perpendicular to the plane of the planet’s orbit of the Sun. The only two exceptions to this are the Earth and Uranus. In the case of ...

6. Geological Activity  Read article

Heat generation by radioactive decay and subsequent heat transfer from the interior to the exterior explains the geological differences among the planets. For example, in the inner solar system, the Earth has a still hot interior, few craters, active volcanism and plate tectonics, and a mean crust ...

7. Chaotic Orbits  Read article

Most orbits in the solar system are regular and repeatable. The orbits of the planets, for example, change very little over periods of hundreds of millions of years. Comet orbits, however, can be quite different. Comets are examples of solar system objects where the orbits can be chaotic. A chao...

8. Problems with Greek Cosmology  Read article

The Greek geocentric cosmology of Aristotle, as propagated by Ptolemy, was highly complex in trying to explain the motions within the solar system. Because the planets do not have uniform motion, the model needed the centers of their motion to be displaced from the Earth. Because Mars, Jupiter, an...

9. Formation of Planets  Read article

The formation of planets in the solar system by the process of accretion occurs efficiently and quickly. The trapping of radioactive isotopes within meteoric material indicates that the entire accretion process from small-sized objects to planet-sized objects took only a couple of million years, a ...

10. Abundance of Terrestrial Planets  Read article

Virtually every extrasolar planet found so far, and there are over a hundred, is an object like Jupiter or Saturn. These gas rich planets with giant atmospheres probably have conditions in their interiors that are utterly inhospitable for life. This fact is significant because the techniques used ...