Our planet Earth is constantly moving in an almost circular path around the sun. The Earth is said to be a Satellite of the sun. It takes one year (365.25 days) for the Earth to make one full revolution, or orbit, around the sun. Different planets take different times to orbit the sun. In addition, the Earth revolves on its own axis every 24 hours.

The moon is a satellite of the Earth. It makes one orbit of the Earth every 27.3 days.

At any on time, only half of the Earth is facing the sun. The side of the Earth facing the sun has day and the side yurned away has night. However, the Earth rotates on its own axis every 24 hours. This ensures that the half in the shade will eventually be in the light.

• The Sun is the primary source of energy for the Earth

• Different parts of the planet receive different amounts of light energy during the year.

• If you look at the picture above, you can see that the Earth is tilted on its axis of rotation. In summer time in the northern hemisphere, we are tilted towards the Sun. The amount of energy falling on the northern hemisphere is increased because:

  • The length of daytime when we receive energy from the Sun is increased

  • The rays of the Sun hit the Earth at almost right angles and their energy is spread over a smaller area

• In winter the opposite is true: The northern hemisphere of the Earth is tilted away from the Sun. The amount of energy falling on the northern hemisphere is decreased because:

  • The length of daytime when energy is received from the Sun is decreased

  • The rays from the Sun hit the Earth at oblique angles and have to spread the same energy over a larger area

• The Earths is always tilted t the same angle but, because of its rotation around the sun, different parts get different exposure to the sun during the year.

• When the northern hemisphere is tilted away from the Sun, the southern hemisphere is tilted towards the Sun. When we are in deep winter in Ireland it is high summer in Australia!

The moon orbits the Earth every 27.3 days. The moon also rotates on its axis every 27.3 days. Since the moon spins on its axis at the same rate it takes to orbit the Earth, the same side of the moon is always facing the Earth.

The moon is visible on Earth when it reflects light from the sun. However, different amounts of the illuminated face are visibel from the Earth as the moon orbits the Earth. The changing appearance of the moon as it orbits the Earth is referred to as the phases of the moon. The phases are summarized in the above image. More detail is given below.

• Day 1: New moon: From Earth, we cannot see any moon because the sunlit part of the moon is facing away from the Earth.

• Days 2-6: Waxing crescent: The word waxing means 'to increase in size'. The moon appears as a crescent. Since the moon is getting bigger, it is called a waxing crescent

• Day 7: First quarter: We see half of the lit face of the moon. (The word quarter here refers to the first quarter of the lunar month and no the amount of the moon that we can see)

• Days 8-13: Waxing gibbous: A gibbous shape is greater than a semicircle but less than a whole circle. We see more and more of the lit side of the moon.

• Day 14: Full moon: We see all of the lit part of the moon.

• Days 15-20: Waning gibbous: The word waning means 'to decrease in size'. We see less and less of the illuminated side of the moon until half of one face seems illuminated. Since the amount of the moon that is illuminated is getting less, it is called a waning gibbous.

• Day 21: Third quarter: We see half of the lit face of the moon.

• Days 22-26: Waning crescent: The illuminated portion of the moon gets less and less.

• Day 28: We gave a new moon and the cycle begins again.

The word eclipse means 'to obscure'. An eclipse occurs when a celestial body blocks the sunlight illuminating another celestial body.

• A lunar eclipse happens when the moon passes into the Earth's shadow. The Earth blocks some or all of the light moving between the sun and the moon and casts a shadow on it.

• A lunar eclipse happens only during a full moon and only if the moon passes into part of the Earth's shadow

• A lunar eclipse is shown above. You must be able to draw and label this!

The word eclipse means 'to obscure'. An eclipse occurs when a celestial body blocks the sunlight illuminating another celestial body.

• A solar eclipse occurs when the moon passes between the Earth and the sun. The moon blocks some sunlight travelling from the sun to the Earth.

• A solar eclipse can only happen during a new moon and only if the Earth passes through the shadow of the moon.

• A Solar eclipse is shown above. You must be able to draw and label this!