The Origin of Our Solar System (Great Chain of Origins and Origin Hypotheses) Review Sheet #1
1. For the Solar Nebula Theory (SNT) to be a successful theory on how our solar system came to be,
what must it do? What are some of the things that the SNT must explain?
It must account for all of the phenomena we observe in our solar system. It must account for the
counterclockwise revolution of planets around the sun, the presence of terrestrial and Jovian planets,
the presence of asteroids, comets, and other space debris, etc.
2. Compare and contrast an evolutionary type hypothesis/theory with a catastrophic type
hypothesis/theory.
An evolutionary theory utilizes gradual, “common,” highly predictable processes to explain the
formation of the solar system. A catastrophic theory utilizes highly improbable sudden events to
explain the formation of our solar system. If evolutionary forces predominate, then the universe
should be full of planets.
3. What was notable about Descartes’ hypothesis? What mechanism (how) did he suggest was
responsible for the origin of the solar system?
Descartes’ hypothesis was novel because it utilized physical processes to explain the formation of the
solar system. He posited that the sun and planets formed when a large vortex contracted and
condensed.
4. What kind of hypothesis was Louis de Buffon’s (evolutionary versus catastrophic) and what did he
posit (suggest) was the origin of the solar system?
Buffon proposed that the planets formed when a comet collided with the sun, thus it is a
catastrophic hypothesis, and pulled matter out of it.
5. How did Pierre-Simon de Laplace’s hypothesis explain the formation of the solar system? What
was his truly innovative contribution to astronomy (he incorporated something into his theory
that was very fresh and new)?
Laplace’s hypothesis combined more conventional astronomical theory with Newton’s laws of
gravity. Laplace hypothesized that vortices had been acted on by gravity. Gravity had acted on the
vortices and pulled them flat into a disk. As the disk spun, at a high rate of speed, it began to shed
rings of matter which developed into planets.
6. What was the problem with Laplace’s hypothesis? Why was it rejected?
The hypothesis depended on the sun having most of the angular momentum in the solar system – in
other words, the sun would have been spinning very fast. In fact, the sun rotates slowly and it is the
planets that have most of the angular moment. Laplace’s hypothesis could not explain this fact.
7. How does the Solar Nebula Theory account, in general terms, for the solar system’s formation? Is
it an evolutionary or catastrophic theory?
The Solar Nebula Theory states that the planets, including Earth, formed in a rotating disk of gas and
dust that surrounded the sun as it, the sun, formed. The planets grew within the disk through
processes defined by the basic properties of physics and chemistry. It is very much an evolutionary
theory.
8.
How is the Solar Nebula Theory tested?
Through observations of phenomena found in our solar system and in other solar systems. We utilize
the laws of physics, chemistry, geology, and biology to test the explanations put forward by the Solar
Nebula Theory. In the last twenty years, our ability to make observations has grown by leaps-andbounds as we have developed and employed more powerful and sensitive telescopes and other
instruments.
9.
How common should planets be according to the Solar Nebula Theory?
If planet formation is a natural part of star formation, from disks of gas and dust as the Solar Nebula
Theory indicates, then most stars should have planets orbiting them. The universe should be awash
in planets.