UNIT SUMMARY

1. The Earth is an oblate spheroid or almost spherical in shape due to its flattened poles and bulging equator.

2. Rotation is the movement of the earth on its axis that gives rise to the occurrence of day and night. Revolution is the movement of the earth around the sun, which spans one year.

3. Different places on the earth experience different length of daytime and nighttime due to the inclination of the earth’s axis by 23 ½ degrees.

4. The changes in orientation of the earth axis with respect to the movement of the earth around the sun give rise to the phenomenon of regular seasonal changes.

5. The earth’s immediate neighbor space is the eight planets of the Solar System. The farthest planet, Pluto, has the longest period of revolution. Pluto is the smallest planet while Jupiter is the largest. Earth is the densest among other planets due to its rocky materials. Venus has the highest temperature because of its thick clouds of carbon dioxide.

6. Gravitational pull of the moon on the opposite sides of the Earth causes tides. Two tidal bulges emerge, which result in two high tides and two low tides.

7. Eclipse is another effect of the moon on the earth. It occurs only when the moon. The earth and the sun are in line with one another, when the moon comes between the sun and the earth, solar eclipse is observed. On the other hand, lunar eclipse takes place when the earth comes between the sun and the moon.

8. Comets revolve around the sun in long, elliptical orbits. It has a “head” of burning gases and a long, gaseous tail.

9. Meteors can be seen at night as “shooting stars”. The friction between this stony matter and the air produces a streak of light that makes them appear like shooting stars. Meteorites are meteor chunks that fall on earth.

10. Stars are made of hot gases and they emit their own light. Stars differ in size, color, and temperature. The apparent brightness of a star is referred to as its magnitude.

11. Groups of stars that form a definite pattern are called constellations.

12. Celestial body’s together with other star systems make up galaxy. Our galaxy is named the Milky Way. It is 100,000 lights years in diameter.

13. The universe is composed of millions of galaxies. It is believed that the universe is expanding.