Geography.......................

 Moon.............

1. Gravitational Pull: 1/6th of Earth.

2. Takes 27 days, 7 hrs,43 minutes and 11.47 second to complete one revolution around earth.

3. Rotates on its axis in exactly the same time as that of its revolution. That is why we see only one side of the moon (only 59% of its surface).

4. Moon has no atmosphere.

5. Moon-light takes 1.3 seconds to reach earth.

6. Neil Armstrong and Edwin Aldrin reached moon on July 21, 1969 on Apollo XI (Landing spot is called 'Sea of tranquility'.

The Earth............

1. Also called ‘Blue Planet’. It is the densest of all planets.

2. Circumference: 40,232 km Area: 510 million sq km 

3. 2 types of movements

1. Rotation or daily movement

2. Revolution or annual movement

Rotation...............

1. Spins on its imaginary axis from west to east in 23hrs, 56 minutes and 40.91 seconds.

2. Earth’s rotation results in

(i) causation of days and nights;

(ii) change in the direction of wind and ocean currents;

(iii) rise and fall of tides everyday.

3. The longest day in North Hemisphere is June 21, while shortest day is on 22 December (Vice-versa in S Hemisphere).

4. Days and nights are almost equal at the equator.

Revolution.................

1. It is earth's motion in elliptical orbit around the sun. Earth’ s average orbital velocity is 29.79 km/s.

2. Takes 365 days, 5 hrs, 48 minutes and 45.51 seconds. It results in one extra day every fourth year.

3. Revolution of the earth results in (i) change of seasons; (ii) variation in the lengths of days and nights at different times of the year; (iii) shifting of wind belts; (iv) determination of latitudes.

Equinoxes.............

1. These are dates when days and nights are equal. During these days the sun shines directly over the equator.

2. March 21: Vernal equinox

3. September 23: Autumnal equinox

Solstice..................

1. The time of the year when the difference between the length of days and the length of nights is the largest.

2. During these days the sun shines directly over the tropics.

3. June 21: Summer Solstice

4. December 22: Winter Solstice

Latitude.............

1. Imaginary lines drawn parallel to the equator. Measured as an angle whose apex is at the centre of the earth.

2. The equator represents 0˚ latitude, while the North Pole is 90˚ N and the South Pole 90˚ S.

3. 23 ½ N represents Tropic of Cancer while 23 ½ S represents Tropic of Capricorn.

Longitude............

1. It is the angular distance measured from the centre of the earth. On the globe the lines of longitude are drawn as a series of semicircles that extend from the North Pole to the South Pole through the equator. They are also called meridians.

2. India, whose longitudinal extent is approx. 30, has adopted only one time zone, selecting the 82.5 for the standard time which is 5 hours and 30 minutes ahead of GMT (Greenwich Mean Time).

International Date Line...................

1. It is the 180 meridian running over the Pacific Ocean, deviating at Aleutian Islands, Fiji, Samoa and Gilbert Islands.

2. Travellers crossing the Date Line from west to east (ie, from Japan to USA) repeat a day and travelers crossing it from east to west (ie, from USA to Japan) lose a day.

Eclipses

Lunar Eclipse....................

1. When earth comes between sun and moon.

2. 0ccurs only on a full moon day. However, it does not occur on every full moon day.

Solar Eclipse.............

1. When moon comes between sun and earth.

2. Can be partial or total.

3. 0ccurs only on a new moon day when the moon is in line with the sun. However, due to the inclination of the moon’s orbit, a solar eclipse doesn't occur on every new moon day.