Composite photo showing difference
in water level 
during low tide and high tide.


  • sea tides are the rise and fall of the water level in the earth’s oceans – they happens twice a day.
  • gravitational pull of the Moon and the Sun create the tides on Earth.
  • the Moon’s pull creates two bulges in the sea – one below the Moon and one on the opposite side of Earth.
  • as the Earth’s spins, the tidal bulges seems to move around the world, creating two high tides every day.

Diagram of neap tides and spring tides

  • neap tides – small tides – that happen when the Sun and the Moon are ar the right angles to the Earth and their pulls are weakened by working against one another.
  • spring tides – very high tides – that happen when the Sun and Moon are in line, and combine their pull.
  • the solid earth has tides too – they are very slight and the Earth only moves about 0.5 metres – this is called Earth Tide or Body Tide.
  • tides are also any uplift created by the pull of gravity, as one space object orbits another.



Did you know?

  • some moons orbiting large planets – Jupiter’s moon – Io which have stretched so much that its interior is heated enough to create many volcanoes today.

Io’s volcanoes today

  • whole galaxies can be affected by tidal pulls – making them stretch as they are tugged by the gravitational pull of other passing galaxies.

NGC 6050/IC 1179 (Arp 272) is a remarkable collision between two spiral galaxies,
NGC 6050 and IC 1179, and is part of the Hercules Galaxy Cluster,
located in the constellation of Hercules.
(Picture: NASA, ESA, the Hubble Heritage Team)



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