Beginner's Astronomy

Beginner's Astronomy

&

The Lunar Mystery​

By Jim Aspinall

Can you remember all their names?

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Scientists think the solar system is about 4.7 billion years old, and the universe is 13.7 billion years old!

Welcome to the Solar System!

Multiple Choice

This is a

• surface

• star

• planet

• asteroid

Multiple Choice

How many planets are in our solar system?

• 8

• 9

• 4

• 12

Multiple Choice

A large planet with no rocky ground, like Jupiter or Saturn, is called a

• planetoid

• star

• aqueous planet

• gas giant

Multiple Choice

Our Sun is not a planet. It is a

• star

• nebula

• galaxy

• asteroid

Multiple Choice

This is a space rock. The correct word for it is

• meteor

• asteroid

• moonlet

• rock 'n roll

Multiple Choice

Earth has just one, but many of the other planets have more.

• Core

• Continents

• Atmosphere

• Moon

Multiple Choice

This is the force that pulls you down onto the earth. All planets have it.

• electricity

• gravity

• plasma

• synergy

Multiple Choice

The Moon moves in a ring around the Earth. This ring is called the

• system

• gravity

• orbit

• atmosphere

Many other planets in the solar system have moons, and our moon is not the largest one in the solar system. Jupiter's moon, Ganymede, is the largest.

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However, Ganymede is less than 2% the size of Jupiter, while the Moon is a bit more than 27% the size of Earth. Next to Earth, the Moon is very, very large!​ How can this be?

The moon has a radius of 1,635 miles!

The Mystery of the Moon

Some scientists think that maybe when the Earth was first made from gas and rock, it was spinning so fast a large piece of it broke off! And this piece became the Moon.

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The problem is: Earth has never been spinning fast enough for this to happen.​

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The Earth rotates at a speed of about 1,000 miles an hour

Theory No.1:

The Spinner

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Some other scientists think that maybe the Moon used to be an independent, free-moving planet that got caught in Earth's gravity and after a long time, got into an orbit.

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That seems unlikely too. Earth's gravity would have been too weak at that time. Also, the gravity of the Sun is much, much stronger.​

Theory No.2:

The Rogue Planet

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Scientists think there may be billions of rogue planets!

Some others think that when the Earth was formed, TWO worlds were formed. Earth and the Moon have always been together.

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However, rocks brought back from the Moon show this isn't true. If Earth and the Moon were brothers, they would be made of the same metals​!

Theory No.3:

Earth's Twin

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Moon rocks come in two kinds: highland rocks and sea basalts

Multiple Choice

People think Earth has a large moon because...

• it is the largest in the whole solar system!

• it spins so fast

• it is very large next to Earth

• most other planets have more moons

Multiple Choice

The Earth has never been spinning fast enough for the Moon to...

• break off the Earth

• lose its orbit

• build its own gravity

• be formed in space

Multiple Choice

The Moon does not have the same kind of rock metals as the Earth, which means...

• it is much larger than other moons

• it was not formed together with the Earth

• it is a planetoid

• it was made from asteroids

Nowadays, the most accepted theory is an asteroid the size of Mars hit the Earth billions of years ago. The hit kicked melted rocks into orbit, which joined together to form the Moon.

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But there is still a problem with this: we have not yet found any Moon rocks older than the rocks on Earth.

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The whole thing is a mystery.​

​Theory No.4: Theia's Meteor?

​By Citronade - Own Work, CC BY-SA 4.0

Poll

Which theory do you believe?

• No.1: The Spinner

• No.2: The Rogue Planet

• No.3: Earth's Twin

• No.4: Theia's Meteor