Solutions-Class 8-Geography-Chapter-1-Local Time and Standard Time-Maharashtra Board

The earth requires 24 hours for one rotation. In one hour 15 longitudes will face the sun

To calculate the difference between the local times of any two places on the earth, the difference in degrees of their longitudes should be known

The difference between the local time of any two consecutive longitudes is 04 minutes

• When the sun reaches its highest point in the sky, it is estimated that about half of the day has passed, and this time is regarded 12 noon.
• The time of a certain location is determined by the overhead position of the sun in the sky and is termed the local time of that location.
• During the rotation of the globe, when a specific longitude comes exactly in front of the sun, that longitude is regarded to be at noon (12 noon). This noon time is regarded as the longitude's local time.

In this way, the local time is decided by the noon time.

• The International Standard Time has been decided according to 0° longitude.
• 0° longitude passes through Greenwich, England.
• For an international coordination, it is essential to bring compatibility between the standard times of various countries in the world. For this purpose, the local time at Greenwich is considered to be the International Standard Time.

• With respect to the longitudinal extent, 82°30'E (82.5 °E) longitude passes through the middle of India.
• The difference between the local time at 82°30’ E longitude and the local time at the extreme east and West longitude passing through India is not more than one hour.

Therefore, the standard time of India has been decided by the local time at 82°30’ E longitude.

• The longitudinal extent of Canada is between 52°37’ W and 141° W.
• Thus, the difference between the extreme east and west longitude passing through Canada is of 88 degrees.
• The difference between the local time at extreme east and west longitude passing through Canada is of 352 minutes i.e. 5 hours and 52 minutes.
• Therefore, it is not practically helpful to consider single standard time in Canada. Therefore, for synchronizing the routine activities in the country, Canada has 6 different standard times.

(i) The difference between 60° E longitude and 30° W longitude will be of 90 degrees. (The difference of 60 degrees between 0° and 60° E + the difference of 30 degrees between 0° and 30° W = 90 degrees.)

(ii) Difference in local time

= 90 × 4

= 360 minutes.

= \(\frac{360\,minutes}{60\,,minutes}\)

= 6 hours.

(iii) Longitudes lying to the east of any longitude are ahead of the time of that longitude while those lying to the west are behind.

(iv) Therefore, if it is 12 noon at 60° E longitude, then it would be 6 a.m. at 30° W longitude. (behind by 6 hours)

• The local time at the longitude passing through the middle of a country/place is generally considered as a standard time of that country/ place.
• If the difference in local time between the extreme east and west longitudes travelling through a nation is less than one or two hours, the country is regarded to have one standard time. As a result, in a nation with a considerably smaller longitudinal (east-west) size, there is just one standard time.
• If the difference between the local time at the extreme east and west longitude passing through a country is more than one or two hours, more than one standard time zones are considered for a country. Thus, there exists more than one standard time zones in a country having comparatively more longitudinal (east-west) extent.

(i) Statement: For any longitude lying to the west of particular longitude, the local time decreases by 4 minutes for every longitude. (Sao Paulo is located to the west

of India)

(ii) The difference between the longitudes of Sao Paulo and India = 127°30'.

(iii) Difference in local time

= 127.5 x 4

= 510 minutes.

= \(\frac{510\,minutes}{60\,,minutes}\) = 8 hours 30 minutes.

(iv) Thus, if it is 6 a.m. at India, it would be 9.30 p.m. of the previous day at Sao Paulo.

Therefore, if a football match being played at Sao Paulo, Brazil started in India at 6 a.m. IST, the local time at Sao Paulo would be 9.30 p.m. of previous day.

(i) Midnight     (ii) Sunset

(iii) Sunrise    (iv) Noon