Round 1
What shape do planetary orbits take?
Ellipses (oval-shaped orbits).
What is a moon?
A natural satellite that orbits a planet.
Name the five planets visible without a telescope.
Mercury, Venus, Mars, Jupiter, and Saturn.
Which model places Earth at the centre of the universe?
The geocentric model.
What causes the phases of the Moon?
We see different amounts of the Moon’s lit side as it orbits Earth.
Who discovered that planets move in elliptical orbits?
Johannes Kepler.
Name a planet that has no moons.
Mercury or Venus.
Why didn’t ancient astronomers include Earth in this list?
They thought Earth was the centre (geocentric model) and we cannot see Earth move from Earth.
Which scientist first proposed the heliocentric model?
Nicolaus Copernicus.
Why is there a “new moon” phase even though the Moon is still there?
During a new moon, the side facing Earth is dark because sunlight is hitting the far side only.
Why do planets move faster when closer to the Sun?
The Sun’s gravity is stronger at closer distances, pulling harder → greater acceleration → higher orbital speed.
Why do gas giants tend to have many more moons than rocky planets?
They have much stronger gravity, so they can capture and hold more moons.
Why can’t Uranus or Neptune be seen with the naked eye?
They are too far away and too dim to be seen without telescopes.
Give one piece of evidence that proved the geocentric model wrong.
Galileo saw moons orbiting Jupiter.
Why don’t we get a solar eclipse every new moon?
The Moon’s orbit is tilted, so its shadow usually misses Earth.
What does the word “orbit” mean?
The curved path an object follows as it moves around another object due to gravity.
Why doesn’t the Moon fly off into space even though Earth is moving?
Earth’s gravity keeps the Moon in orbit;
List all five visible planets in order from the Sun.
Mercury
Venus
Mars
Jupiter
Saturn
Why did the geocentric model seem correct to early astronomers?
Because the Sun and stars appear to move around Earth, and Earth feels still.
What is the difference between waxing and waning?
Waxing = the lit part seen from Earth is increasing.
Waning = the lit part seen from Earth is decreasing.
Explain why gravity alone cannot produce a circular orbit for most planets.
Distances from the Sun vary slightly as planets move.
Their speed changes depending on distance.
These variations create ellipses rather than circles.
Explain the difference between a moon’s orbital period and a planet’s rotation period.
Orbital period = time the Moon takes to go around Earth.
Rotation period = time the Moon or a planet takes to spin once on its axis.
Explain why these planets were called “wandering stars.”
They appear to move across the night sky differently from stars (change position relative to stars), so ancient astronomers thought they wandered.
State two variables that the gravitational force between two objects depends on.
Distance between the two objects and the mass between the two objects.
Explain in detail why we always see the same side of the Moon from Earth.
Its rotation period equals its orbital period, so the same side always faces Earth.