Examine the following statements and select the proper options :
Statement (A) : Every longitude has a different local time due to the rotation of the Earth.
Statement (B) : Standard time system is ut

Question

Examine the following statements and select the proper options :
Statement (A) : Every longitude has a different local time due to the rotation of the Earth.
Statement (B) : Standard time system is utilized to remove the difference in the local time.

UnlockIAS · Accepted Answer

Correct — option (1). Both statements are sound, and they belong together as a problem and its remedy. Statement (A) says that every longitude has a different local time because the earth rotates. Local time is time reckoned from the sun as it is seen at a particular place: noon is the moment the sun crosses that place's meridian. Since the earth turns on its axis from west to east through three hundred and sixty degrees in twenty-four hours, it turns through fifteen degrees in an hour and through one degree in four minutes, so the sun reaches the meridian of a place four minutes later for every degree of longitude further west. Two places on different meridians therefore keep different local times, and the difference is exactly four minutes for each degree between them; a place forty-five degrees east of another has its noon three hours earlier. Statement (B) says that the standard time system is used to remove the difference in local time, and that is what standard time is for. If every town kept its own local time, timetables, telegraphy, administration and broadcasting within a single country would be unworkable, so a country adopts the local time of one chosen meridian and applies it uniformly across its territory. India has adopted the meridian of eighty-two degrees thirty minutes east, which passes near Mirzapur in Uttar Pradesh, and Indian Standard Time is five hours and thirty minutes ahead of Greenwich; the whole country from Gujarat to Arunachal Pradesh uses it, although the local time at the two ends of the country differs by about two hours. Standard time does not abolish local time as an astronomical fact; it replaces it for civil purposes, which is precisely what the statement claims. Both statements being correct, option (1) is the answer.

Why the other options are wrong — (b) This option accepts the first statement and rejects the second, and the doubt behind it is usually about the word remove. A candidate reasons that the difference in local time is astronomical, that it goes on existing whatever clocks people agree to use, and that standard time therefore removes nothing. The reasoning is sound as far as it goes but it misreads the claim. Statement (B) is about the practical difference — the difference between the clocks in use at different places within a country — and that difference is exactly what a common standard meridian removes, since every clock in India shows the same reading at the same instant. The habit worth building is to read a statement for what it asserts rather than for the strictest possible sense its words could bear, because an examiner writing a two-sentence assertion pair is describing a system, not drafting a definition.  (c) This option rejects the first statement, and to do so it must deny either that local time varies with longitude or that the earth's rotation is the cause. Neither denial can be sustained. The variation is arithmetically fixed: fifteen degrees of longitude to an hour, one degree to four minutes, so no two meridians can share a local time. As for the cause, candidates sometimes attribute the difference to the earth's revolution around the sun rather than to its rotation on its axis, and the two must be kept apart — the revolution, together with the tilt of the axis, gives the seasons and the varying length of the day through the year, while the rotation gives the daily cycle and with it the succession of local noons from east to west. Statement (A) attributes the difference to the rotation, and that is the right cause.  (d) This option rejects both statements and can be dismissed by the same reasoning that establishes each of them. It is chosen mainly by candidates who cannot decide between the middle two options and take the fourth as a way out. That is worth naming as a habit, because an assertion pair of this form always offers exactly four rows — both true, the first only, the second only, neither — and the fourth is printed whether or not it is the answer, so its presence carries no information. The disciplined procedure is to judge Statement (A) on its own and mark it, then judge Statement (B) on its own and mark it, and only then to look for the row that matches the two marks. Here both marks are ticks, and the row that records them is the first one.

Concept: The earth turns on its axis once in about twenty-four hours, and every question about time on the globe follows from that single fact and its arithmetic: three hundred and sixty degrees in twenty-four hours is fifteen degrees an hour, one degree in four minutes and one minute of arc in four seconds of time. Local time is what this gives directly — the time shown by the sun at a particular meridian — and it changes continuously as one moves east or west, so it is useless as a common standard. The remedy is to choose one meridian, take its local time and impose it over a wide area, which is standard time. The system is anchored on the prime meridian through Greenwich, from which the world's time zones are counted, and standard meridians are ordinarily chosen as multiples of fifteen degrees, or of seven and a half degrees where a half-hour offset is wanted. India uses eighty-two degrees thirty minutes east, giving a whole-country offset of five and a half hours from Greenwich, and it keeps a single time zone although its territory stretches from about sixty-eight to about ninety-seven degrees east, which is why the sun rises in Arunachal Pradesh roughly two hours before it rises in Gujarat. Large countries such as Russia, the United States and Canada take the opposite course and use several zones. The International Date Line, drawn approximately along the one hundred and eightieth meridian with deviations to avoid dividing island groups and territories, is where the date changes.

State PCS 2022 Q15 — Geography PYQ with Answer

State PCS 2022 Q15 — Geography PYQ with Answer