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Then lighter pieces gathered and formed Earth's crust.Īs Earth's mass added up from all this matter and gravitational forces increased, the matter attempted to take the most efficient shape possible: a sphere. Earth's rocky core was the first part of our planet to form, with dense matter sinking to the center and binding together. As gravity pulled the matter in on itself, it began to spin and clump up, forming the sun, planets, moons, and other space objects. Scientists theorize that about 4.6 billion years ago, the solar system was a cloud of dust and gas. The amount of mass throughout Earth, however, is huge and really adds up. Smaller objects, such as a car or a house, have tiny gravitational forces. Mass attracts other mass, resulting in the force we call gravity. These features are, in fact, interrelated. Two features of Earth that determine its shape are mass and gravity. But why is it round? And is it perfectly round like a rubber ball? Let's see what science can tell us about the answers to those questions. We now know different, but were those views really all that crazy back then? Probably not! The evolution of scientific knowledge has proven that, when it comes to astronomy, you can't always rely on your senses. Hundreds of years ago, people believed Earth was flat and that the Sun traveled around Earth. Without that sideways motion, it would fall to the center and without the pull toward the center, it would go flying off in a straight line, which is, of course, exactly what happens if you let go of the string. That might be one of the most awesome interesting facts ever. If you swing it around, you are constantly pulling it toward your hand, just as the gravity of the Sun pulls the planet in, but the motion sideways keeps the ball swinging around. This is the same as if you have a weight on the end of a string. Now if the Sun is pulling the planets, why don't they just fall in and burn up? Well, in addition to falling toward the Sun, the planets are moving sideways. Heavier objects (really, more massive ones) produce a bigger gravitational pull than lighter ones, so as the heavyweight in our solar system, the Sun exerts the strongest gravitational pull. The Sun's gravity pulls on the planets, just as Earth's gravity pulls down anything that is not held up by some other force and keeps you and me on the ground.
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Newton realized that the reason the planets orbit the Sun is related to why objects fall to Earth when we drop them. In the same way, the moon and satellites we launch orbit Earth because they are so much lighter than our planet, from enjoyyourlifeinet. The Sun is 1000 times heavier than the largest planet, Jupiter (which also happens to be my favorite planet), and it is more than 300,000 times heavier than Earth (another planet I am very fond of). Now why does a planet orbit the Sun and not the Sun orbit the planet? The lighter object orbits the heavier one, and the Sun is, by far, the heaviest object in the solar system. A planet orbiting the Sun is like the moon or a NASA satellite orbiting Earth.
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I'll touch on a few.įirst of all, saying the planets go around the Sun is just another way of saying the planets are in orbit around the Sun. Most people take this fact for granted, but the answer involves many interesting ideas and important concepts. Some visitors to the Gheens Science Hall & Rauch Planetarium at the University of Louisville in Kentucky recently asked why the planets go around the Sun.