Have you ever wondered what the terms “full moon”, “new
moon”, or “blue moon” mean? Did you know there are phases of the moon?
The moon is the Earth’s only natural satellite. It has a
diameter of 3476 km and is approximately 384 400 km from Earth. It is the
second brightest object in the sky after the sun.
The moon orbits around the Earth once per month. The moon
keeps the same face towards Earth at all times; this is known as synchronous
rotation. As it orbits our planet, we see the cycle of the moon’s phases due
to the changes in relative positions of the Earth, the moon, and the sun.
The sun illuminates the half of the moon facing the sun
(except during lunar eclipses). When the sun and moon are on opposite sides
of the Earth, the moon appears bright or “full”.
When the moon is between the Earth and the sun, it appears
dark, or as a “new” moon. In between, the moon’s illuminated surface appears
to grow (wax) to full, then decreases (wanes) to the next new moon.
To learn more about the moon and it phases, visit
The Moon: Royal Observatory
of the Moon
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