Module 1 - The Solar System

The Solar System


Before we can discuss the processes that affect planets, it makes sense to take stock of the inventory of our solar system.   We live in a solar system with our star (the sun) at its centre.  In orbit around the sun are 8 planets, 5 dwarf planets, 181 moons and an enormous number of small solar system bodies that range in size from about 950 km in diameter to mere specs of solid material.  The whole thing is approximately 4.6 billion years old.  And while it seems to be working fairly smoothly right now, you'll see in module 2 that its early history was much more exciting.

To us earthlings, the most important body in the solar system is the Earth (followed closely by the Sun) because we live here and without the Sun to keep us warm and the water wet we wouldn’t exist. 
However, the Earth is just a tiny, almost insignificant part of the solar system; the total mass of the Earth amounts to only 0.2% of the total mass of all of the other planets combined.  The Sun accounts for 99.86% of the total mass of the entire solar system with planets only accounting for the remaining 0.14%.  This means that the Earth’s share of the total mass of the solar system is only 3*10-6
or 3 millionths of the mass of the solar system…..a trivial proportion by anyone’s standards.  Fortunately, our almost insignificant planet just happens to be in the right location to have conditions that allowed not only creation of life but was right for early simple life to evolve to the diversity of complex life that includes humans.

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