Heliocodex

Learn / Outward from here

Planets

On the scale of light: 2 light minutes to 4 light hours. 7 lessons, in the order to read them.

  1. Start hereRock, gas, ice: three kinds of planetThe eight planets come in three sorts, and where each one formed explains which sort it is.First look · How it works
  2. How the planets formedThe planets grew from a disc of gas and dust around the young Sun, from specks to boulders to worlds, in a few tens of millions of years.First look · How it works
  3. Air and the greenhouse: Venus, Earth and MarsThree rocky planets began much alike and ended as a furnace, a home and a frozen desert. The difference is their air.First look · How it works
  4. RingsAll four giant planets have rings. They are countless separate pieces of ice and rock, each on its own orbit, and astonishingly thin.First look · How it works
  5. What counts as a planetFor 76 years the Solar System had nine planets. In 2006 astronomers agreed on what the word means, and Pluto no longer fitted.First look · How it works
  6. The Earth as a planetSeen from outside, the Earth is one rocky planet among four. It is also the only one with seas on its surface, and the only place known to have life.First look · How it works
  7. Inside planets and their magnetic shieldsNobody has been more than a scratch below the ground, yet earthquakes show what is inside the Earth. The moving metal at its centre makes a shield round the planet.First look · How it works

Outline Still to be written here

  1. The dwarf planetsPluto, Eris, Ceres and the rest: what they are and how they were found.