GC Leong Test: The Earth & The Universe- 2 - BPSC (Bihar) MCQ

• In winter the oblique rays of the sun, come through the atmosphere less directly and have much of their heat absorbed by atmospheric impurities and water vapour.

• The sun's rays fall faintly and spread over a great area. There is thus little heat, and temperatures remain low.

• Also, days are longer than nights in summer and more heat is received over the longer daylight duration. Nights are shorter and less heat is lost.

The brief period between sunrise and full daylight is called dawn, and that between sunset and complete darkness is termed twilight.

• There is Imaginary Prime Meridian (0°) on the surface of the earth from which all other meridians radiate eastwards and westwards up to 180°.

• Since the earth is spherical and has a circumference calculated at 25,000 miles, in the linear distance, each of the 360 degrees of longitude is 25,000-360 or 69.1 miles.

• The degree of longitude therefore decreases in length. It is longest at the equator where it measures 69.172 miles.

• Since the earth makes one complete rotation of 360° in one day or 24 hours, it passes through 15° in one hour or 1° in 4 minutes.

• The earth rotates from west to east, after moving 15 degrees eastwards, local time is advanced by 1 hour i.e. 15X4 is equal to 60.
  and it is noon so it is clearly  ahead in time so 60°E

• Most countries adopt their standard time from the central meridian of their countries. The Indian Government has accepted the meridian of 82.5° east for the standard time which is 5hrs. 30 mins. ahead of Greenwich Mean Time.

• The whole world has been divided into 24 Standard Time Zones, each of which differs from the next by 15° in longitude or one hour in time.

• U.S.S.R. the largest country, which extends through almost 165° of longitude is divided into eleven time zones.

• Travellers along the Trans-Siberian Railway have to adjust their watches almost a dozen times before they reach their destination.

• As the earth rotates from west to east, every part of the earth's surface will be brought under the sun at some time or other.

• Later, when it is gradually obscured from the sun's beams it experiences sunset. The sun is, in fact, stationary and it is the earth which rotates.

• Earth has seasons because its axis is tilted. Earth's axis is always pointed in the same direction, so different parts of Earth get the Sun's direct rays throughout the year. For example, in summer, the Sun's rays hit that region more directly than at any other time of the year.

• When it is summer in the northern hemisphere, the southern continents will experience winter. Mid-summer at the North Pole will be mid-winter at the South Pole.

• The stars appear small to us even through a telescope because they are so far away. The light from the nearest star travelling at the speed of light (i.e. 186,000 miles per second) takes something like four years to reach us.

• A ray of light from the sun takes about eight minutes to reach the earth. Light takes only a second to reach us from the moon.

• Lunar eclipses occur when Earth's shadow blocks the sun's light, which otherwise reflects off the moon. There are three types — total, partial and penumbral — with the most dramatic being a total lunar eclipse, in which Earth's shadow completely covers the moon.

The shadow cast by the earth on the moon during the lunar eclipse is always circular. It takes the outline of an arc of a circle. Only a sphere can cast such a circular shadow.