Our solar system was formed 4.6 billion years ago. If the sun were hollow, it would take a million moons to fill it up. The sun is average in temperature: 10,000 F. The energy of nuclear reactions at its core takes 30,000 years to reach the surface. Mercury’s temperature varies between 800 by day and -300 at night. One day lasts 1400 hours; it spins slow and orbits fast. Venus is the hottest planet at 900 F. Venus’ day is longer than its year, 225 earth days. Mars has no intrinsic magnetic field. It has two small moons, Phobos and Deimos, the Latin words fear and panic. Saturn’s rings are thousands of braided, differently colored rings of gas. It takes 29 earth years to revolve around the sun. The main rings of Saturn span 165,000 miles, but the bands are on average only 150 feet thick. Saturn is seven hundred times Earth’s size, but so light that if one could drop it in a pool, it would float. Saturn spins so fast that its day last less than eleven earth hours. The planet is still molten, mostly gas, but the force of the planet’s mass turned hydrogen into liquid metal that creates a great magnetism. So its wide atmosphere is wracked by updrafts and storms. Winds blast at supersonic speeds, thousands of miles an hour. Saturn has thirty-five named moons. Its moon, Iapetus, is half black, half white—one side of its icy surface may have been bombarded. The largest moon, Titan, more massive than Mercury, is like the surface of crème brulée, a thin burned cover on molten stone. Rain may fall every century or so. Jupiter is so large (a failed star) that it’s shrinking and that produces great heat; its core is hotter than the sun’s surface. Jupiter’s surface is covered with clouds hundreds of miles thick. Jupiter’s spot is two to three earths across; it’s a storm that has changed pattern but has never been known to move. Under the clouds, Jupiter is covered with volcanoes; it is entirely resurfaced every few years. It has at least sixteen moons; one, Io, is unique among moons for having volcanoes, too. Uranus is on its side and half is in a 42-year night. Neptune has the fastest winds, up to 700 mph. Neptune’s largest moon, Triton, orbits in the opposite direction of the other large moons in our solar system. It orbits the sun every 60,000 days or 164.7 years. Astronomers argue about whether Pluto is a planet or a sad piece of flotsam; it has not cleared an orbit for itself; its moon, Charon, is the biggest moon proportionally, jerks Pluto around. Its orbit is the only one on a different plane from the others, and it’s elliptical. Pluto is closer to the sun than Neptune 20 of every 250 earth years (it takes 250 earth years for Pluto to orbit the sun, at a speed of 10,000 mph.) It has hardly enough mass to keep an atmosphere. Ceres, the largest asteroid, is about the size of Texas, six hundred miles across. There are at least 64 moons in our solar system. Our moon always shows us the same face. Earth speeds eight times faster than a bullet. The earth is smoother than a billiard ball.