Unit equivalent to 1 Solar Mass 1.989 x 1030 kg 333,000 Earth Masses 1,050 Jupiter Masses 1 Solar Radius 6.960 x 108 m (or 696,000 km) 109 Earth Radii 0.0046 AU 1 Solar Luminosity Unit 3.83 x 1026 W

Unit equivalent to 1 Earth Mass 5.977 x 1024 kg 1/318 Jupiter Masses 1 Earth Radius 6.380 x 106 m (or 6,380 km) 1/11.2 Jupiter Radii 1 Earth Density 5.52 g/cm3 1 Earth atmosphere mass 5.14 x 1018kg 1 Earth Escape Velocity 11.2 km/s 1 g (Earth Gravity) 9.81 m/s2

Unit equivalent to 1 Astronomical Unit 1.496 x 1011 m (or 149,600,000 km) 215 Solar Radii 1/63240 LY 1 Light Year 9.461 x 1015 m

Coriolis Force: The force generated by a rotating body to "bend" normal currents in the atmosphere, hydrosphere and geosphere. More on this in Part II.

Diurnal: Daily.

IR: Infra-red, radiation emitted in longer wavelengths than the light we can see (off the "red" end of the spectrum). It is usually divided into near-IR, mid-IR and thermal IR. Only thermal IR is directly related to the sensation of heat.

Life Zone: The approximate area around a star where a world can sustain liquid water and moderately advanced life. The life zone used here is pretty wide.

Main Sequence: The "normal" stage in a star's life. The Sun is a main sequence star. These have the suffix "V" to their spectral class. Non-main sequence stars include for instance giants and white dwarves.

Parsec: 3.26 LY = 1 pc. One kiloparsec (kpc) is thus 1000 parsec, and one megaparsec (Mpc) 1000000 parsec. The parsec is a commonly used distance unit in astronomy. In this document light years are used instead.

Planetesimal: Chunk-like protoplanet-bodies which later form terrestrial planets and larger chunks. Exist in a young systems survivors will be asteroid-like remnants of decent size (perhaps up to moon-size).

Primary: Typically this refers to the star in a system which the body in question orbits. The Sun is Earth's primary.

Retrograde: Clockwise motion. It is not the normal motion a body in retrograde orbit moves in the wrong direction.

Roche Limit: The distance a sizeable moon must have to avoid being torn apart by the planet it orbits. It is about 2.5 planetary radii, counted from the center or the world, if the density of the satellite and the planet are the same.

Tidal Lock: Situation for a planet or moon when it rotates so it always shows the same side to the primary. Moons are generally tidally locked to the planets they orbit, and planets close to their primaries are often tidally locked to. This is a form of regular rotation see TWO/1 for more info.

UV: Ultra-violet, radiation of shorter wavelengths than visible light. UV radiation is important in breaking down molecules and high UV infall is detrimental to unprotected life.