Astronomy

The motions of Earth relative to the Sun, and the motions of the Moon and Sun relative to Earth affect different phenomena on Earth, including day and night, the seasons, tides, and phases of the Moon.

The Eight Phases of the Moon

Just like Earth, half of the moon is illuminated by the sun, the other half is in darkness. The phases of the moon that we see come from the different angles at which sunlight hits the moon.
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The Lunar Cycle is 29 days.
If the Moon is full on Day 1, it will be full again on Day 30.

Tides

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Tides are the regular rising and falling of Earth’s surface water in response to the gravitational attraction of the Moon and Sun. The Moon’s gravity pulls upwards on Earth’s water, causing it to bulge out in the direction of the Moon. On the other side of the Earth, a high tide is produced where the Moon’s pull is weakest. The gravity of the Sun also pulls Earth’s water towards it and causes its own tides. Because the sun is so far away, its pull is smaller than the Moon’s.

Spring Tide

When the Sun and Moon are in line, during the new moon and the full moon, their high tides add up and create a spring tide. During a spring tide, high tides are really high, which means that low tides are really low.

Neap Tide

A neap tide occurs when the high tide of the Sun adds to the low tide of the Moon and vice versa so the tidal range is relatively small.

Tidal Days

The tidal cycle is 24 hours and 50 minutes.

  • Diurnal or daily tides - have a single high-tide and a single low-tide per tidal day.
  • Semidiurnal or semidaily tides - have two high-tides and two low-tides of approximately equal height each tidal day.

Eclipses

Lunar Eclipse

Where the Earth blocks the sun's rays from partially reaching the moon.



  • Partial Eclipse - The moon is in the Earth's penumbra shadow
  • Total Eclipse - The moon is in the Earth's umbra shadow

Solar Eclipse

Where the moon blocks the sun's rays from partially reaching the Earth.


  • Partial Eclipse - The Earth is in the moon's penumbra shadow
  • Total Eclipse - The Earth is in the moon's umbra shadow

SEASONS

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The seasons are caused by the 23.5° tilt of Earth’s axis of rotation relative to its plane of orbit around the Sun. The tilt tilt on its axis leads to one hemisphere facing the Sun more than the other hemisphere and gives rise to seasons.

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During the summer, areas north of the equator experience longer days and shorter nights. In the Southern Hemisphere, the Sun is as far away as it will be and so it is their winter so these areas will have longer nights and shorter days.


The Earth's revolution (trip around the sun) takes 365 days!