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Earth and Space - The shape of the Earth, Sun and Moon

Grade 3Cambridge (IGCSE)

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Understanding the difference between 2D2D and 3D3D shapes is vital. A circle is a 2D2D flat shape, whereas a sphere is a 3D3D solid shape. The Earth, Sun, and Moon are spheres.

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Relative sizes: If the Sun were the size of a large beach ball, the Earth would be the size of a small pea, and the Moon would be the size of a pinhead.

📐Formulae

Shape=Sphere\text{Shape} = \text{Sphere}

Size Comparison: Sun>Earth>Moon\text{Size Comparison: Sun} > \text{Earth} > \text{Moon}

Sun Diameter≈109×Earth Diameter\text{Sun Diameter} \approx 109 \times \text{Earth Diameter}

Earth Diameter≈4×Moon Diameter\text{Earth Diameter} \approx 4 \times \text{Moon Diameter}

💡Examples

Problem 1:

If a student draws the Moon as a flat circle on a piece of paper, is this a scientifically accurate representation of its 3D3D shape?

Solution:

No.

Explanation:

A drawing on paper is 2D2D (flat). In reality, the Moon is a 3D3D sphere, similar to a ball. The circle only represents the 'face' of the Moon that we see from Earth.

Problem 2:

Why does the Sun look about the same size as the Moon in the sky, even though the Sun is much larger?

Solution:

Because of the distance from Earth.

Explanation:

The Sun is approximately 400400 times further away from Earth than the Moon is. This makes the giant Sun appear to be the same size as the much smaller Moon when viewed from our planet.

Problem 3:

Arrange the following in order of size from smallest to largest: Earth, Moon, Sun.

Solution:

Moon<Earth<Sun\text{Moon} < \text{Earth} < \text{Sun}

Explanation:

The Moon is the smallest, the Earth is medium-sized, and the Sun is the largest body among the three.