Solar system

The four inner planets are...

• Rocky and small
• Very large and made of ice
• Small and made of ice
• Very large and made of gases

The outer planets are...

• Rocky and small
• Very large and made of ice
• Small and made of ice
• Very large and made of gases

Why is space travel difficult for people?

• We cannot take the air or food we need into space
• the distance are very great; it is dangerous and expensive.
• It is impossible to escape the sun's or Earth's gravity.
• We do not have a destination to visit that we know will support life.

What holds the planets in their orbits around the sun?

• gravity
• speed
• string
• air currents

Which object has the most gravity?

• Earth
• moon
• Jupiter
• sun

What is a planet?

• a group of stars that forms a pattern in the sky
• a large ball of hot gases that gives off heat and light
• a large ball or rock or gas that moves around the sun
• a toy aliens play with

This picture shows the path Earth takes as it moves around the sun. What is the path called?

• a constellation
• a moon
• an orbit
• a planet

What is another word for rotate?

• orbit
• skip
• spin
• run

Which of the following are gas giants?

• Earth

• Jupiter

• Pluto

• Saturn

• Mars

A force of attraction between any two objects is called _____________.

• static electricity 
• rotation
• gravity
• orbit