The Solar System

Now we're going to talk about the solar system the keyword here is solar and the root there is "Sol" which is the Latin name for the Sun. The solar is the system of things around the Sun specifically it's all the celestial bodies that are bound to the Sun by the Sun's gravity. You basically think of it as the Sun and the planets although there are other things in there besides the planets.

This picture shows the Sun and things orbiting the Sun. The planet Mercury is closest to the Sun and then Venus and then you see the earth and the moon orbiting the earth. All orbiting the Sun and then there's Mars and then the next thing up from Mars is this band around of asteroids. That is the asteroid belt and then beyond that, you see the larger outer planets there's Jupiter, Saturn, Uranus, and  Neptune, and then way out here this is Pluto.
Pluto was recently Declassified as a planet it was originally considered a planet, but now they call it it's a separate category it's what they call a dwarf planet it doesn't quite fit the description of an actual planet. There are other things in the solar system as well this is a comet. For example, comets are orbiting the Sun even though this one looks like it's about the plow right into the Sun and that certainly can happen. A lot of comets orbit the Sun sometimes in very elongated orbits.

Other planets besides the earth have moons. For example, Mars has two moons and Jupiter and Saturn have lots of moons. There are other things besides the Sun and the planets but that's what the solar system is, the solar system is the system of bodies that are bound to the Sun by the Sun's gravity.
 Now one thing to note is that this picture here is not to scale. If this was drawn to scale if the Sun were this size then the planets would be much smaller compared to the Sun, much farther away what this does show though is all of the things orbiting the Sun. So it's accurate in the sense that it gives it a decent idea of the arrangement and the order of things: Mercury, Venus, Earth, and Mars near the Sun. And then the asteroids. Jupiter, Saturn, Uranus, and Neptune further out. 

Just to know that this diagram is not drawn to scale. One important thing about this diagram that is correct though is that the Sun is at the center, and that was actually A big intellectual breakthrough to realize that the Sun is the center of the solar system. That idea though has not been held by most people throughout the history of the world. Throughout history, most people haven't even been aware of the solar system as we see it here in this picture. Most people have thought that the earth was at the center. That has been the dominant view historically what we call a geocentric system, Geocentric meaning earth is at the center.

Now the ancient Greeks were aware of some things about the solar system. They were aware for example that there were planets when you look at the night sky you see the Stars, and they're sometimes referred to as the fixed stars. Even though the stars are moving the stars are so far away that we can't discern any motion from night tonight and even year after year they all appear to stay in the same place relative to each other. But because the planets are moving around the Sun when we see the planets in the night sky their position changes night after night relative to the background stars or the fixed stars.

The Greeks were aware of this they were aware of five planets and they called them Wanderers, the Greek word for the planet actually means wanderer. Some of the Greek thinkers had some pretty good ideas Aristarchus for example was able to make some measurements about the distance to the moon and the distance to the Sun and the size of each of those. He actually put forth the idea of a heliocentric system that is sun-centered as we see in the picture. A few other ancient thinkers from other cultures did also but they were in the minority. The majority report throughout all of history has been a geocentric system that has been the dominant view and specifically the geocentric system as described by Ptolemy the Alexandrian astronomer.