GC Leong Test: The Earth & The Universe- 1 - BPSC (Bihar) MCQ

• The solar system comprises the Sun and its nine planets which are believed to have been developed from the condensation of gases and other lesser bodies.

• All the planets revolve around the Sun in elliptical orbits. Like the earth, they shine only by the reflected light of the sun.

Amongst the eight planets, Mercury is the smallest and closest to the sun, only 36 million miles away. It thus completes its orbit in a much shorter space of time than does Earth.

Ship's visibility: When a ship appears over the distant horizon, the top of the mast is seen first before the hull. In the same way, when it leaves the harbour, its disappearance over the curved surface is equally gradual. The earth was flat, the entire ship would be seen or obscured all at once.

• Explanation:

  Both statements are correct:

• In the summer (June) Daylight increases as we go polewards: This is correct because during the summer solstice in the Northern Hemisphere, areas closer to the poles experience longer daylight hours. As you move towards the poles, the duration of daylight increases, leading to phenomena like the "Midnight Sun" in polar regions.

• At the Arctic Circle, the sun never 'sets' at mid-summer (21 June): This is also correct. On the summer solstice (around June 21), the Arctic Circle experiences 24 hours of daylight, meaning the sun does not set, a phenomenon known as the "Midnight Sun."

• Since both statements are correct, the answer is that none of the above statements are incorrect.

By about 22. December, the sun will be overhead at the Tropic of Capricorn (23 1/2°S.). This is the winter solstice when the southern hemisphere will have its longest day and shortest night. The Tropics thus mark the limits of the overhead sun, for, beyond these, the sun is never overhead at any time of the year. Such regions are marked by distinct seasonal changes— spring, summer, autumn and winter. Beyond the Arctic Circle (66 1/2°N.) and the Antarctic Circle (66 1/2°S.) where darkness lasts for 6 months and daylight is continuous for the remaining half of the year.

• Latitude is the angular distance of a point on the earth's surface, measured in degrees from the centre of the earth. It is parallel to a line, the equator, which lies midway between the poles.

• The most important lines of latitude are the equator, the Tropic of Cancer (23 1/2 °N.), the Tropic of Capricorn (23 1/2°S.), the Arctic Circle (66 1/2°N.) and the Antarctic Circle (66 1/2°S.).

• As the earth is slightly flattened at the poles, the linear distance of a degree of latitude at the pole is a little longer than that at the equator.

• 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.

• We may thus conclude that places east of Greenwich see the sun earlier and gain time, whereas places west of Greenwich see the sun later and lose time.

• If we know G.M.T., to find the local time, we merely have to add or subtract the difference in the number of hours from the given longitude, as illustrated below. Simple memory aid for this will be East-Gain-Add (E. G. A.) and West-Lose Subtract (W.L.S.).

A traveller crossing the dateline from east to west loses a day (because of the loss in time he has made), and while crossing the dateline from west to east he gains a day (because of the gain in time he encountered).