Nova: Earth is Born

The small grains of ​ (a)   collide and grow ​ (b)   , slowly growing into ​ (c)   due to ​ (d)   .

• dust
• larger
• planets
• gravity

_______ are left over pieces of early planets. They are a window on the past.

• Lava

• Meteors

• Rocks

• Trees

The early Earth was ​ (a)   . The heavy ​ (b)   slowly sank to the ​ (c)   of the planet, forming our ​ (d)   .

• molten lava
• iron
• center
• core
• moon
• surface

The Earth's ​ (a)   pole is constantly ​ (b)   . The ​​ (c)   of the pole is picking up ​ (d)   .

• Magnetic
• moving
• movement
• speed
• dust
• electric

The moon has the ​ (a)   as the​ (b)   but is considerably ​ (c)   .

• same material
• Earth
• younger
• older
• Mars

(28:00) The ​ (a)   was once much ​ (b)   the Earth. It is still slowly ​ (c)   from the Earth.

• Moon
• closer to
• pulling away
• farther from

(32:00) Zircon ​ (a)   found in ​ (b)   were formed soon after the Earth's crust ​ (c)   . That meant that the crust formed only ​ (d)   years after the Earth was formed.

• rocks
• Australia
• cooled
• 150 million

The current theory is that the ​ (a)   was formed from a ​ (b)   of a ​ (c)   planet with the early ​ (d)   .

• moon
• collision
• Mars-sized
• Earth

(28:30) There is a ​ (a)   on the ​ (b)   , put there by Apollo Astronauts. It also us to precisely ​ (c)   the orbit of the Moon, using a powerful ​ (d)   in New Mexico.

• retroreflector
• Moon
• measure
• laser
• flashlight
• Mars

(29:06) The moon is moving away from the Earth at a rate of about ____.

• 1 ^1/2 inches per year

• 1 mile per year

• 60 miles per hour

• 2 miles per year.