Earth, and the rest of the solar system, formed from a giant cloud of gas and dust in space called a __.

• protosun

• nebula

• galaxy

• comet

Answer explanation

As the cloud collapsed, it begin to spin. This spinning caused it to flatten, forming a ___.

• protosun

• protoplanetary disk

• planetesimal

• nebula

Answer explanation

As the solar system continued to evolve, material in the disk collided with other material and grew into planetesimals, then protoplanets, and then planets. This process of growth by collision created a lot of heat, melting the early Earth. Growth by collision is called ___.

• differentiation

• accretion

• adsorption

• kinetic molecular theory

Answer explanation

Since the early Earth was molten, the most dense material sank to the center forming the core. Less dense material rose towards the surface, forming the crust. This process is known as ___.

• differentiation

• accretion

• adsorption

• kinetic molecular theory

Answer explanation

What is the name for the scientific explanation for the origin of stars and planets?

• The accretion hypothesis

• The nebular hypothesis

• The gravitational collapse hypothesis

• The protoplanetary hypothesis

What did students from our school (as part of a collaborative team of students from several school) use the Spitzer Space Telescope to look for signs of star formation in?

• The Orion Nebula

• The Milky Way

• a dark nebula (LDN 981)

• Andromeda

How old is Earth?

• 4.6 thousand years

• 4.6 million years

• 4.6 billion years

• 4.6 trillion years

Answer explanation

What type of energy is related to the velocity and mass of an object?

• potential

• chemical

• gravitational

• kinetic

How old is our planet?

• 13.8 billion years

• 13.8 million years

• 4.6 million years

• 4.6 billion years

Where did all of Earth's original rock go?

• It was carried back into the mantle by subduction

• It was weathered by wind and water.

• Both answers are correct

• neither answer is correct