Earth's Orbit, Seasons and Satellites

Section: Earth and Space | Syllabus: Cambridge Primary Stage 5 Science (0097)

Earth's Orbit around the Sun

Earth travels around the Sun in a path that is a slight ellipse (a gently stretched circle), not a perfect circle.
Viewed from above Earth's North Pole, the direction of travel is anticlockwise.
One complete orbit takes about 365.25 days, which is why a calendar year is usually 365 days.
The extra quarter-days build up and produce an additional leap day, 29 February, about every four years.

Earth's axis - the imaginary line it spins around - is tilted, not upright.
As Earth orbits the Sun, this tilt stays pointing in the same direction, so each hemisphere is tilted towards the Sun for part of the year and tilted away for part of the year.
A hemisphere tilted towards the Sun receives more direct sunlight and has longer days, which produces warmer conditions - this is summer.
The Northern and Southern Hemispheres always have opposite seasons at the same time.
Seasons are not caused by Earth being much nearer to the Sun in summer - the tilt is the main cause.

Earth's tilt, not its distance from the Sun, creates the seasons

A satellite is any object in space that orbits a larger object.
A moon is a natural satellite that orbits a planet.
Earth's Moon is a natural satellite; communication satellites and the International Space Station are artificial satellites, built and launched by humans.

A moon is a natural satellite; a space station is an artificial satellite

Worked Example: Natural or Artificial?

Question: Europa orbits Jupiter. A weather satellite made by humans orbits Earth. Classify both objects. [2]

Europa is a moon orbiting a planet, so it is a natural satellite. The weather satellite was made by humans, so it is artificial. Answer

Europa is a natural satellite of Jupiter. The weather satellite is an artificial satellite of Earth.

MistakeSummer happens because Earth is much closer to the Sun.

FixDifferent seasons are created mainly by Earth's tilt as it orbits the Sun.

Interactive revision notes, videos and practice questions load below.