astronomy

• weight = mass x gravitational field strength

  w = mg
• our solar system consists of the sun which lies in the centre (heliocentric) and there are 8 planets which orbit it, natural satellites, asteroids/comets and dwarf planets (orbit the sun e.g. Pluto or Ceres)
• the planets have natural satellites which orbit it - moon orbits the earth, a planet
• order of planets - closes to sun to furthest :

  Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune
• smaller planets mostly rocks and larger planets mostly gas
• larger planets have rings because their large gravitational field strength pulls debris towards it
• geocentric model :

  • earth seemed to be in the centre, other planets and the sun orbited the earth
  • it has a fixed background of stars stars
• Galileo, using a telescope, saw Jupiter have moons orbiting it therefore indicating every body doesn't fully orbit around the earth
• Kepler showed planets orbited in ellipses not circles