The Solar Nebula Theory: Formation of the Solar System

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  • 0:01 Competing Hypotheses
  • 0:56 Evolutionary vs.…
  • 1:52 The Solar Nebula Theory
  • 3:45 Lesson Summary
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Lesson Transcript
Instructor: Artem Cheprasov
This lesson will go over the theory that explains how the solar system formed, what theory had once competed with it, and what important implication this theory carries.

Competing Hypotheses

Paleontologists who study the extinction of the dinosaurs seem to be split into two camps. There are the intrinsic gradualists and the extrinsic catastrophists.

Since this lesson isn't really about the debate of what killed giant lizards, I'll put everything this way: the gradualists believe that the extinction of the dinosaurs was mainly caused by gradual changes involving things like volcanism that caused climate change. The catastrophists point to something more sudden and, well, catastrophic, like an asteroid hitting the earth and causing the extinction.

Such gradual vs. catastrophic hypotheses are nothing new to science, and the same types of hypotheses have been proposed to explain the formation, as opposed to destruction, of the solar system. We'll discuss which theory won out and how the theory explains the formation of the neighborhood we call home.

Evolutionary vs. Catastrophic Hypothesis

Back in the 20th century, the two competing theories as to what force was responsible for the creation of the solar system were the catastrophic hypothesis and the evolutionary hypothesis.

The catastrophic hypothesis is a hypothesis that states that our solar system formed thanks to a sudden and improbable event such as the collision of two stars.

The evolutionary hypothesis is a hypothesis that states that gradual and natural changes caused the formation of our solar system.

Although many astronomers and physicists tend to lean towards the catastrophic explanation for the extinction of the dinosaurs, they don't seem to do so for the explanation of the solar system. Odd bunch they are. In the 20th century, enough evidence was gathered to conclude that the evolutionary hypothesis was correct, and it's now really more than a hypothesis, it's a theory.

The Solar Nebula Theory

What came out of the evolutionary hypothesis was the solar nebula theory, the theory that posits that the planets and sun in the solar system formed from the solar nebula. The solar nebula is a cloud of interstellar gas and dust that condensed to form the entire solar system, including the sun and planets.

So, what this theory is saying is as follows:

Originally, there was a rotating cloud of gas that condensed and flattened out like a pancake. At the center of this thin disk of dust and gas, the sun began to form. But the dust and gas are also the ingredients for the planets themselves. So, as the sun formed, the planets formed from these ingredients. Eventually, when the sun became luminous enough, the unnecessary dust and gas was blown away into space, leaving the planets around the sun.

This is sort of like taking a pizza dough ball and rotating it to the point that it becomes like a pancake shape. After it flattens, you plop it onto a plate. Then you cut a circle into the center with something like the edge of an upside-down cup, then other circles around the center with smaller cups, and then remove the pieces in between to get our solar system.

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