For an explanation, see the main splats page
SPLATS about the solar system
The principles of the solar system
- Every body in the solar system has an albedo, though some have less than others. For small bodies, the albedo depends only on what they are made of.
- The closest point of a planet's orbit to the sun is called the perihelion, the most distant point of a planet's orbit from the sun is called the aphelion.
- Orbiting bodies obey Kepler's laws of planetary motion, whether they are planets around the Sun, or moons (or spacecraft) orbiting one of the planets.
- The planets obey Kepler's three laws of planetary motion, which can all be shown to follow naturally from the operation of gravitational forces.
- Kepler's first law says that all planets revolve around the Sun in elliptical orbits, with the Sun lying at one focus of the ellipse traced out.
- Kepler's second law says that for any planet, a radius line joining that planet to the Sun sweeps out equal areas of space in equal lengths of time.
- Kepler's third law says that the square of the period of revolution (year) of a planet is proportional to the cube of its mean distance from the Sun.
- In 1626, Godfried Wendilin verified Kepler's laws of planetary motion for the moons of Jupiter, showing that the laws apply to all orbiting bodies.
- In 1684 Isaac Newton proved that planets moving under an inverse-square force law obey Kepler's laws of planetary motion, that gravity is the same everywhere.
- In 1787, William Herschel found the planet Uranus, which he called a star, and claimed to have found volcanoes on the surface of the moon, but he got better.
- In 1613 Galileo Galilei used sunspots to demonstrate the rotation of the sun on its axis, and he also outlined the principle of inertia at the same time.
- In 1675 Giovanni Cassini reported his discovery that Saturn has separated rings and that they must necessarily be composed of small orbiting objects.
- We can measure the distances to the moon using radar transmission and reflection, though other methods can be used to get a reasonable estimate of the distance.
- Our solar system is made up of the Sun and nine planets and many smaller bodies, including asteroids, comets, moons, dust and Kuiper Belt Objects.
- Planets form from dust and debris from old supernovae that is drawn into the gravitational field of a star that is forming, where something pulls it together.
- Around 1640, René Descartes used a strange notion of vortices to present a model of the solar system which matched Galileo's, but avoided annoying the Church.
- In 1755 Immanuel Kant proposed his theory that the universe formed from a spinning nebula in an infinite hierarchy, which seemed like a good idea at the time.
- In 1905, Percival Lowell suggested there might be a ninth planet beyond Neptune, which he called Planet X. He photographed it before he died, but never saw it.
- In 1977, James L. Elliot discovered five rings around the equator of the planet Uranus, by the occultation of a star. Voyager 2 found four more rings in 1986.
- In 1980 Voyager 1 sent back pictures of Jovian system, in which researchers discovered the rings of Jupiter ,and these were further investigated by Voyager 2.
- Orbits are elliptical. Very rarely, the ellipse may be close to circular, but the circle remains just a special form of the ellipse, with equal semi-axes.
- Gravity acts everywhere: while people say that things in space are weightless, that is only because the entire frame is responding to gravity in the same way.
- Asteroids are relatively small bodies orbiting the sun, some of them in eccentric orbits that cross the Earth's. Some asteroids are large enough to have moons.
- In 1757 The Catholic Church removed Galileo Galilei's Dialogue on the Two Chief World Systems from its list of banned publications, after more than a century.
- There are places, the Lagrangian points, where objects may 'float in space', because they are points of stability where different gravitational fields balance.
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