FSS - Accretion Theory Lesson
Accretion Theory
The most widely accepted scientific theory of how the solar system was created is the accretion theory. Accretion would have occurred within the giant cloud of gas and dust, called a nebula, that surrounds our solar system. This theory proposes that, since even the smallest particles have gravitational and other attractive forces between them, nearby particles were attracted together to form clumps of particles. Since these clumps had the combined mass of the original particles, these clumps (called planetesimals) now behaved like larger masses, which allowed them to pull on other particles that were farther away. Clumps of matter pulled neighboring clumps together, forming "clumps of clumps". Given enough time, the masses of particles ultimately coalesced into the structures that make up our solar system.
Watch the animation showing the theory of an accretion model of planet formation created by NASA.
Suppose that you spill some salt on the floor. The gravitational attraction of the Earth prevents the individual grains from moving towards each other; they are being pulled towards the center of the Earth with much more force than they are to each other. However, the same is not true if the Earth's gravitational force can be minimized. In 2003, astronaut Donald R. Pettit, while filming simple investigations on board the International Space Station for a show called "Saturday Morning Science", filled up some plastic bags with various particles - one with sugar, one with coffee, and one with salt - gave each of them a vigorous shake, and then observed what happened. Within seconds, particles began to clump together, forming centimeter-sized clumps inside the bags.
When you bake a batch of chocolate chip cookies, you first mix all of the ingredients together in a larger mixing bowl, and then you spoon out dollops of cookie dough onto a baking pan. You can make some spoonfuls bigger and others smaller, and some spoonfuls might have a few more chocolate chips than others. Larger dollops might be chewy after baking, while smaller dollops might be crunchy but, overall, all of the cookies are pretty much the same. In many ways, this is a good analogy for how the solar system formed. The nebula from which it formed is a giant cloud of gas and dust, and the objects that clumped together would be like the dollops of cookie dough that were spooned out of the mixing bowl. In other words, all of the planetary bodies (and the sun) are essentially made of the same ingredients - even though they have different properties today. In fact, if all of the objects we know as planets had continued to grow, they might have become stars just like the sun!
IMAGES CREATED BY GAVS OR OPENSOURCE