The best means of measuring time is by the movement of the Earth, the Moon and the planets. The Sun regularly rises and sets every day and naturally, it is the best time-keeper throughout the world. Local time can be reckoned by the shadow cast by the Sun, which is the shortest at noon and longest at sunrise and sunset. When the Prime Meridian of Greenwich has the Sun at the highest point in the sky, all the places along this meridian will have mid-day or noon.
As the Earth rotates from West to East, those places East of Greenwich will be ahead of Greenwich time and those to the West will be behind it. The rate of difference can be calculated as follows. The Earth rotates 360° in about 24 hours, which means 15° an hour or 1° in four minutes. Thus, when it is 12 noon at Greenwich, the time at 15° East of Greenwich will be 15 × 4 = 60 minutes, i.e., 1 hour ahead of Greenwich time, which means 1 pm but at 15° West of Greenwich, the time will be behind Greenwich time by 1 hour, i.e., it will be 11.00 am Similarly, at 180°, it will be mid-night when it is 12 noon at Greenwich.
(i) How is local time affected in places East of Greenwich ?
(a) Local time is behind Greenwich time.
(b) Local time is ahead of Greenwich time.
(c) Local time is the same as Greenwich time.
(d) Local time is not affected.
(ii) How is local time determined according to the passage ?
(a) By the movement of the Moon.
(b) By the shadow cast of the Sun.
(c) By the rotation of the planets.
(d) By the position of the Prime Meridian.
(iii) How does the Earth’s rotation affect time in different places ?
(a) It causes variations in local time.
(b) It determines the length of the day.
(c) It influences the movement of the Moon.
(d) It creates differences in sunrise and sunset times.
(iv) How is the time difference calculated between two locations, according to the passage ?
(a) By the length of the day.
(b) By the Earth’s revolution around the Sun.
(c) By multiplying the distance by 4 minutes.
(d) By calculating the Moon’s position.