krit.club logo

Earth and Space - Introduction to the Solar System

Grade 3IGCSE

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

🔑Concepts

The Solar System consists of the Sun and all the objects that travel around it, including 88 planets, their moons, asteroids, and comets.

The Sun is a star at the center of the Solar System. It is a massive ball of glowing gas, primarily Hydrogen (HH) and Helium (HeHe).

The eight planets in order of distance from the Sun are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

Earth rotates on its axis once every 2424 hours, which creates the cycle of day and night.

Earth revolves (orbits) around the Sun. One full revolution takes approximately 36514365 \frac{1}{4} days, which we call a year.

The Moon is Earth's natural satellite. It does not produce its own light; it is visible because it reflects light from the Sun (LightSunMoonEarthLight_{Sun} \rightarrow Moon \rightarrow Earth).

Gravity is the invisible force that pulls objects toward each other and keeps the planets in orbit around the Sun.

📐Formulae

1 Day=24 Hours1 \text{ Day} = 24 \text{ Hours}

1 Year365.25 Days1 \text{ Year} \approx 365.25 \text{ Days}

1 Lunar Month28 Days1 \text{ Lunar Month} \approx 28 \text{ Days}

DistanceEarthSun1.5×108 kmDistance_{Earth-Sun} \approx 1.5 \times 10^8 \text{ km}

💡Examples

Problem 1:

If the Earth takes 36514365 \frac{1}{4} days to orbit the Sun, how do we handle the extra 0.250.25 day in our calendar each year?

Solution:

We add one extra day to the calendar every 44 years.

Explanation:

Since 0.25×4=10.25 \times 4 = 1, we add a 'Leap Day' (February 29th) every four years to keep our calendar synchronized with the Earth's orbit.

Problem 2:

Why does the Sun appear to rise in the East and set in the West?

Solution:

Because the Earth rotates on its axis from West to East.

Explanation:

The Earth spins at a constant rate of 360360^{\circ} every 2424 hours. This rotation makes stationary objects in space, like the Sun, appear to move across our sky.

Problem 3:

Which planet is known as the 'Red Planet' and where does it sit in the order from the Sun?

Solution:

Mars; it is the 4th4^{th} planet from the Sun.

Explanation:

Mars appears red due to iron oxide (rust) on its surface. In the order of planets (11: Mercury, 22: Venus, 33: Earth, 44: Mars), it follows Earth.