Latitudes and Longitudes are imaginary lines used to determine the location of a place on earth.
Earth is slightly flattened at the North and the South Poles and bulge in the middle – lending it a geoid shape.
- A true model (miniature form) of the earth
- Not fixed
- Can be rotated the same way as topspin or a potter’s wheel is rotated
- Countries, continents, and oceans are shown in their correct size
A needle is fixed through the globe in a tilted manner (called its axis). Two points on the globe through which the needle passes are two poles – the North Pole and the South Pole
An imaginary line running on the globe dividing the Earth into two equal parts
- Represents the zero degrees latitude
- Distance from the equator to either of the poles is one-fourth of a circle round the earth, it will measure ¼th of 360 degrees, i.e. 90°
- 90 degrees north latitude marks the North Pole
- 90 degrees south latitude marks the South Pole
Parallels of latitude
All parallel circles from the equator up to the poles.
All parallels north of the equator are called ‘north latitudes’ and all parallels south of the equator are called ‘south latitudes.’
Latitudes are measured in- Degrees
- Tropic of Cancer (23½° N) in the Northern Hemisphere
- Tropic of Capricorn (23½° S) in the Southern Hemisphere
- Arctic Circle at 66½° north of the equator
- Antarctic Circle at 66½° south of the equator
Heat Zones of Earth
- Also known as the Tropics; Receives the maximum heat
- Bounded on the north by the Tropic of Cancer and on the south by the Tropic of Capricorn; these latitudes mark the northern and southern extremes of regions in which the sun seasonally passes directly overhead.
- The mid-day sun is exactly overhead at least once a year on all latitudes in between the Tropic of Cancer and the Tropic of Capricorn
- The Sun is never directly overhead
- Climate is mild, generally ranging from warm to cool
- The occurrence of four annual seasons, spring, summer, autumn and winter
- Very cold: Areas lying between the Arctic Circle and the North Pole in the Northern Hemisphere and the Antarctic Circle and the South Pole in the Southern Hemisphere
- Slanting rays
Used to find out how far east or west these places are from a given line of reference running from the North Pole to the South Pole. These lines of references are called the meridians of longitude.
Distances between them are measured in ‘degrees of longitude’; each degree is further divided into minutes, and minutes into seconds.
- A Circle = 360 Degrees
- 1 Degree = 60 Minutes
- 1 Minute = 60 Seconds
They are semi-circles and the distance between them decreases steadily polewards until it becomes zero at the poles, where all the meridians meet.
Unlike parallels of latitude, all meridians are of equal length and therefore, it was difficult to number the meridians- Decision to begin from the meridian which passed through Greenwich, where the British Royal Observatory is located-Prime Meridian.
- Value is 0° longitude and from it, we count 180° eastward as well as 180° westward
- Divides the earth into two equal halves, the Eastern Hemisphere and the Western Hemisphere
- Remember: 180° East and 180° West meridians are on the same line
Longitude & Time
- Earth- Divided into twenty-four time zones of one hour each
- Each zone- Covers 15° of longitude
Best means to measure time: By observing the movement of the earth, the moon, and the planets
- Regularly rises and sets every day.
- 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
- How to calculate the rate of difference:
- 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 p.m. But at 15° west of Greenwich, the time will be behind Greenwich time by one hour, i.e., it will be 11.00 a.m.
- Similarly, at 180°, it will be midnight when it is 12 noon at Greenwich.
- At any place, a watch can be adjusted to read at 12 o’clock when the sun is at the highest point in the sky, i.e., when it is mid-day. The time shown by such a watch will give the local time for that place.
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References: NCERT Geography, Certificate Physical And Human Geography: G C Leong