Directions: Complete the following sentences with the correct word or words.

1.             1.   Earth has seasons because it_________________________________
2.             2.   One complete revolution of Earth around the sun takes about _______________ days.
3.             3.   Earth’s rotation takes about ________ hours.
4.             4.   Day and night are caused by Earth’s ______________________ on its axis.
5.             5.   When the north end of Earth’s axis is tilted toward the sun, North America will experience the season of __________________________.
6.             6.   The phase of the moon you see depends on how much of the _______________ side of the moon faces Earth.
7.             7.   From new moon phase to full moon phase, you see an ___________________ amount of the lighted side of the moon.
8.             8.   For a solar eclipse to occur, the ____________ must be directly between Earth and the_________.
9.             9.   A lunar eclipse occurs during the __________________ phase of the moon.
10.           10.   Tides are caused mainly by differences in how much the _________________ pulls on different parts of Earth.
11.           11.   _________________ on the moon’s surface were formed by ancient lava flows.
12.           12.   Galileo saw that much of the moon’s surface is covered with round pits called _______________.
13.           13.   The moon is about ____________________ the diameter of Earth.
14.           14.   Scientists think the ___________________ was formed when a large object struck Earth, and ejected material from the collision combined.
15.           15.   In the Southern Hemisphere, the summer _______________ occurs when the sun is farthest south.
16.           16.   An __________________ occurs when neither end of Earth’s axis is tilted toward or away from the sun.
17.           17.   Because the moon rotates once for each revolution around Earth, you never see the ________________________ of the moon from Earth.
18.           18.   The amount of the lighted side of the moon you can see is the same during ______________ quarter and ___________________ quarter phase.
19.           19.   You are less likely to see a total _________________ eclipse than a total ________________ eclipse because the moon’s umbra only covers a small area on Earth’s surface.
20.           20.   All objects are attracted to each other by the force of_______________________.
21.           21.   The different shapes of the moon seen from Earth are called _________________.
22.           22.   The temperature of the moon’s surface varies greatly from day to night because the moon has no________________________.
23.           23.   A total solar eclipse is visible from only within the moon’s __________________.
24.           24.   Water might be found on the moon near the _____________________.
25.           25.   Satellites in a __________________________ orbit stay above the same point on Earth.
26.           26.   A large artificial satellite on which people can live and work for long periods is called a _____________________________.
27.           27.   Rockets move forward because _______________ is propelled out of the back of the rocket.
28.           28.   Rocket technology originated in_________________.
29.           29.   The reaction force that propels a rocket forward is called ___________________.
30.           30.   The space race was between the United States and the ________________________.
31.           31.   The first human in space was ______________________________.
32.           32.   The American program to land people on the moon was called ___________________.
33.           33.   A _________________________ can be used many times to carry astronauts into orbit.
34.           34.   The main source of power for the International Space Station is __________________.
35.           35.   Exploration of space beyond the moon has been done by ________________________ with no human crew.
36.           36.   The beginning of spring in the Northern Hemisphere is marked by the __________________ equinox.
37.           37.   _______________ are flat areas, once flooded with lava, on the moon’s surface.
38.           38.   During a ______________ eclipse, Earth blocks sunlight from reaching the moon.
39.           39.   The moon formed after a planet-sized object collided with ___________________.
40.           40.   Scientists learned much about the moon by studying _____________ brought back by astronauts.
41.           41.   A _______________________ rocket has parts that fall off after their fuel is burned up.
42.           42.   ____________________________ was the first person to walk on the moon.
43.           43.   Small robots that can move around on the surface of a planet are called space ______________________.
44.           44.   The space station being built now is called__________________________________.
45.           45.   It takes the moon _____________ days to complete one full cycle of phases.
46.           46.   The ______________ stage of a multistage rocket creates thrust for takeoff.
47.           47.   The ______________ stage of a multistage rocket reaches space.