This is the amount of time required for the Earth to spin once on its axis.

• calendar
• day
• month
• year

This is roughly the amount of time required for the Earth to orbit the Sun once.

• calendar
• day
• month
• year

This is roughly the amount of time required for the moon to orbit the Earth once.

• calendar
• day
• month
• year

This scientist was the first to publish a theory stating that the Sun was at the center of the planets and universe.

• Brahe
• Copernicus
• Kepler
• Newton

This is a system for organizing time.

• calendar
• month
• year
• day

This scientist was the first person to use a telescope to observe celestial bodies.

• Brahe
• Copernicus
• Galileo
• Newton

This scientist explained that the force that keeps all of the celestial bodies in their orbit is gravity.

• Brahe
• Copernicus
• Galileo
• Newton

This type of telescope uses curved mirrors to gather and focus light.

• refracting
• reflecting
• obstructing
• abstracting

This is composed of the sun and planets and other bodies that travel around the sun.

• comet
• galaxy
• solar system
• universe

Tiny building blocks of planets are called

• asteroids
• comets
• meteors
• planetesimals