Question

What is local time? Estimate the time at the following longitudes assuming the Greenwich Mean Time as 10 am.
 (i) 45° East longitude
 (ii) 30° West longitude

Answer 1

Hint:In geographical terms, Meridian can also be described as a line of longitude. In the Royal Observatory in Greenwich located in London, the mean solar time which is established by calculation from Midnight can be defined as Greenwich Mean Time (GMT) This time remains constant all the year.

Complete answer:
 We can describe local time as the time which is based on Meridian passing through a particular area in contrast to the meridian of the time zone in which the place is located.
. As we know the earth rotates west to east direction. Time remains in minus towards west and advances towards the east. The time of Sun rising and setting occurs later towards west and advances towards east.

i) When the time is at 45° longitudes East As we know earth rotates one round in 24.hours it means 360 longitudes move facing the Sun and in one hour 15° longitudes pass.( 360 divided by 24=15) So, 45° divided by 15°=3 hour or 45° times 4 minutes= 180mintes and 180 minutes divided by 60.minutes=3.hours. Therefore at 45° East will be 3. hour plus the given time( 10 a.m).
So, the required estimated time is 10 a.m. plus 3 hours i.e, 1 p.m.

ii) When the time is at 30° longitudes west As we know earth rotates one round in 24.hours it means 360 longitudes move facing the Sun and in one hour 15° longitudes pass.( 360 divided by 24=15) . So, 30° divided by 15°=2.hour or 30°multiplied by 4minutes= 120 minutes and 120 minutes divided by 60 minutes=2 hours. Therefore at 30° West will be 2 hour minus the given time (10 am).
So, the required estimated time is 10 a.m. minus 2 hours i.e., 8 a.m.

Note:Because of the relative differences in the position of the sun in different places the time In each place varies. Time zones in different regions of the globe can be called as local time of the respective regions. To bring uniformity in these differing times we use local mean time which is determined by combining all the variation of the time in local regions. All the time zones depend on the location of the place that means it varies according to the longitudes and latitudes of the place.