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LO: Comparing times for the rotation of Earth, Sun and Moon, and comparing the times for the orbits of Earth and the Moon
Humans have always been fascinated with the Sun and Moon. In fact, most ancient civilisations have created stories on how the sun and Moon where created.
In Norse mythology the sun and moon are dragged across the sky in chariots, ridden by the children Sol (sun) and Mani (Moon).
Image source: https://norse-mythology.org/skoll-hati/
In ancient Greek mythology, Helios was the god of the sun, rode a golden chariot across the sky each day.
Image source: https://www.theoi.com/Titan/Helios.html
These days, we know a lot more about the Sun, Moon and Earth.
Spoiler alert, there is no golden chariot in the sky.
WHAT WILL YOU LEARN?
The Sun is a star that makes up 99.8% of our solar system, but compared with other stars in the universe it’s considered small. The Earth is 100 times smaller than the sun in diameter and our largest planet (Jupiter), is still 10 times smaller than the sun in diameter.
Even though it is over 150 million km from earth, its light only take 8 minutes to reach us! This light energy provides the earth with energy and heat for everything living thing on earth.
We are one of 8 plants in our solar system. We are the third closest to the sun, and the sun is the centre of our whole solar system. All the planets, dwarf planets, moons and asteroids orbit (circle) the sun.
The path that a planet takes as it orbits the sun, is called its orbit and usually follows an oval or elliptical shape.
Earth is our home and is the only planet in our solar system with complex life. We sit in a ‘Goldilocks Zone’, which is just the right distance from the sun, to keep water liquid and allow life to flourish. The atmosphere is a mixture of nitrogen (78%) oxygen (21%) and other gases (1%).
The moon orbits the Earth, and is the Earth’s only natural satellite. As it circles the earth over 27.3 days it slowly spins, taking 29.5 days to complete a full rotation of it’s own. This is why we only see one side of the moon from earth. You’ll often see at night how bright the moon is. This is because the moon reflects the light from the sun. We’ll talk more about the moon in the next section.
These days, we know that the day is not brought by Sol in a chariot and the night by Mani. Day and night is caused by the Earth spinning of it’s axis. The Earth’s axis is an imaginary line that goes through the Earth from the North to South Pole.
As the Earth rotates, it takes 24 hours to complete 1 full rotation. When it’s around 9pm in Melbourne, Australia it’s 8am in Brazil. This is because of how the Earth is shaped, only part of the Earth is exposed to sunlight at any given time. When parts of the Earth experience day time other are experiencing night time. As the Earth rotates, it exposes other parts of the Earth to the sunlight.
1 day is how long it takes the earth to do a complete rotation. 1 year or 365.25 days, is how long it takes the Earth to orbit the sun once.
So that we don’t loos a day every 4 years (because of the .25 days), we add an extra day in February, called a leap year.