The Greek astronomer who believed that the sun and other objects in the sky revolved around Earth.
Who was Ptolemy?
100
The unit that astronomers use to measure distances in the solar system.
What are astronomical units, or AUs.
100
This object is nearer to Earth than any other object in the solar system.
What is the moon?
100
A ball of ice, dust, and gases that revolves around the sun in a long, narrow path.
What is a comet?
200
Almost 1,400 years after Ptolemy, this Polish astronomer published a new model suggesting that the sun was at the center of the solar system.
Who was Copernicus?
200
The paths that planets travel in as they revolve around the sun.
What are orbits?
200
This rocky object is like a small planet. It orbits around the sun in a "belt" located between the inner and outer planets.
What is an asteroid?
200
As a comet gets near the sun, its tail streams out in this direction due to the sun's radiation, or "solar wind".
What is away from the sun?
300
In the 1600's, Johannes Kepler, a German astronomer, made a model showing the planets traveling in these paths instead of the circular ones described by Copernicus.
What are elliptical paths?
300
The force that keeps planets in their orbits as they revolve around the sun.
What is gravity?
300
This small piece of rock or metal is formed when asteroids collide or comets break up.
What is a meteoroid?
300
The pull of gravity from the moon and sun causes this on Earth.
What is the rise and fall of tides?
400
A representation of how something looks or works.
What is a model?
400
Aside from the sun, these objects are closer to Earth than any star, causing them to look brighter than stars. They were known as "wanderers" by ancient people.
What are the planets?
400
As a meteoroid passes through the Earth's atmosphere, friction makes it so hot that the rock burns, causing this streak of light.
What is a meteor?
400
When the sun and moon are lined up with Earth, their pulls combine and cause very high tides, otherwise known as these.