Latitude
It is the angle between equatorial plane and the straight line that passes through a point on earths surface and the center of the earth. This will give the latitude of the point as the angle in this case. If we join all the points on the surface of the earth at same angle with the equatorial plane in the given hemisphere, we get circle called as the latitudinal circle of the given angle. Example the Tropics are the circle of 23.5 degree latitude, Polar are the circle of 66.5 degree latitude. Hence the latitudinal lines are parallel to each other and distance between them remains always same, which is 111 km approximately.
Range of the angle is from 0 to 90 degree. Hence latitudes has values ranging from 0 to 90 degree.
Tilt of the Earth is always in the same direction as shown in above figure. The earth when revolve around sun, somewhere at one position the northern half of earth is tilted towards sun and at opposite to that location the southern half of earth is tilted towards the sun.
The rays that pass through the center is always perpendicular or the rays which fall perpendicular to earth surface passes through the center.
The Earth is tilted 23.5 degree. The sun rays which fall perpendicular to earth surface passes through center. As the earth can't tilt more than 23.5 degree, hence the latitude over 23.5 degree will never get sun rays vertically overhead because at that point the maximum tilt we can have is 23.5 degree.
Tropic of Cancer: It is the northern most latitude upto which sun rays will be vertically overhead. It is 23.5 degree north latitude.
Then around 6 months later the earth position will be such that the southern half will be tilted towards the sun and the same phenomenon applies here also.
Tropic of Capricorn: It is the southernmost latitude upto which sun rays will be vertically overhead. It is 23.5 degree south latitude.
Tropical Region: The tropics or tropical region is the region where the Sun rays are vertically overhead i.e it is the region between Tropic of cancer and Tropic of Capricorn.
21st June or Summer Solstice: It is the date on which the earth's northern half is tilted maximum towards the sun i.e on this date the vertical overhead is on Tropic of Cancer.
21st/22nd December or Winter Solstice: It is the date on which the earth's southern half is tilted maximum towards the sun i.e the vertical overhead is on Tropic of Capricorn.
21st September and 21st March or Equinox: On this date the sun is vertically overhead the equator. These dates are also called Equinox. When the day and night is of equal length. 21st march is called Spring equinox and 21st September is called Autumn equinox.
Polar circle:
Polar circle is known as the minimum latitude at which there is 24 hours day or night one day in a year. 66.5 degree north and south both, there is 24 hours day and 24 hours night once in a year. 66.5 degree North is the Arctic circle whereas 66.5 degree South is the Antarctic circle.
At poles there is 24 hours day or night for 6 months. Hence we can say that as one moves from Polar circle to the poles, the number of days for which the region experiences 24 hour day or night depending on the respective hemisphere being tilted towards and then away from the sum, the number of days will vary from one on polar circles upto six months at poles.
Length of the day depends on latitude and on the tilt of earth respective hemisphere with respect to the sun(Except for equator). Hence length of day and night on equator is always equal round the year. Higher the latitude is, the longer will be the day or night depending on whether the earth tilted towards or away from the sun respectively.
Longitude
Longitude, is a geographic coordinate that specifies the east–west position of a point on the Earth's surface. Which longitude should be taken as 0 degree longitude was a problematic question in early days because ideally, any longitude could be considered as 0 degree longitude but for practical purpose the longitude passing through The Royal British Observatory, in Greenwich is taken as 0 degree longitude also called as prime meridian.
180 degree longitude is considered as the International date line. Either we call it 180 degree east or 180 degree west both are same.
The distance between two longitude at equator is approximately 111 km. But the distance decreases as we go towards the pole where it becomes 0 degree.
1 degree longitude rotation is equal to 4 minutes i.e (24 hours / 360)*60 minutes = 4 minutes. Every 1 degree longitude towards east is 4 minutes ahead and every 1 degree longitude towards west is 4 minutes behind.
82.5 degree East is Indian Standard time passing through Prayagraj.
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