This force keeps the planets in orbit around the Sun.
What is gravity?
100
The sun is made mostly of these.
What are hot gases (hydrogen and helium)?
100
This is the amount of time it takes Earth to rotate on its axis.
What is 1 day?
100
The rims, of these circular pits, make our Moon appear to have hills and even mountain ranges.
What are craters?
200
This planet is positioned closest to the Sun.
What is Mercury?
200
This is the center of our solar system.
What is our Sun?
200
The Sun is a major source of these two forms of energy.
What are light and heat (thermal) energy?
200
This is the amount of time it takes Earth to revolve around the Sun.
What is 1 year or 365 days?
200
These are the shapes the moon appears as, including a circle (full moon), a half moon (quarter) and a crescent.
What are the phases of our Moon?
300
This is the fourth planet from the sun.
What is Mars?
300
This is the movement a planet makes, as it moves around the Sun in a year.
What is a revolution?
300
These areas appear as small dark spots on the Sun's surface.
What are sunspots?
300
This layer of gases surrounds Earth, keeps temperatures on Earth at a habitable range, and protects us from small meteors.
What is our atmosphere?
300
This repeating pattern, of the phases of our Moon, takes 28 days to complete.
What is the lunar cycle?
400
This planet is located between Mars and Saturn.
What is Jupiter?
400
This is an imaginary line, that runs through the top, center, and bottom, of a planet or moon.
What is an axis?
400
This is the outer edge of the Sun's atmosphere.
What is a corona?
400
This is the condition of Earth's atmosphere, at a particular place and a specific time.
What is weather?
400
Without this around the moon, temperatures are too high and low for life, and breathing is impossible, without an oxygen mask. Our Moon has so many craters because it lacks this.
What is an atmosphere?
500
This planet is positioned after Uranus, and before the dwarf planet-Pluto.
What is Neptune?
500
This is when a planet or moon makes a complete turn on its axis.
What is a rotation?
500
The sun heats up part of the air on Earth, while other air masses are cooled, causing air to rise and fall.
What is wind?
500
This causes weathering and erosion when it flows. It also provides organisms with one of our most basic needs to survive.
What is liquid water?
500
The moon's gravitational pull causes Earth's ocean water levels to rise and fall, near the shore.