Latitude and Longitude:
- It is an angular distance of a point on the Earth’s surface measured in degrees from the Earth center.
- These are called parallels as they are drawn parallel to the equator.
- These lines are actually circles becoming smaller poleward.
- The Equator represents 0° whereas the North pole and South pole are 90°N and 90°S respectively. Between this three-point of reference, lines of latitudes are drawn at an interval of 1° each.
- The Equator is called the greatest circle because it is the largest possible circle drawn on the earth’s surface.
- There are 179 lines of Latitude.
- How many latitudes are there? – 181.
- Linear distance– is the distance between two consecutive lines of latitude. This goes on to increase towards the pole. For example- at 0°C it is 68.704 miles, at 45°C it is 69.054 miles, and at 90°C it is 69.407 miles. The average linear distance is 69 miles. It increases because earth is likely flattened at the poles, so the linear distance of a degree of latitude at the pole is a little longer than that of at the equator.
- The most important function is that we can know how much northward and southward we are placed from the equator.
- It is an angular distance measured in degrees along the equator east or west of the prime meridian.
- On the globe, longitude is shown a series of semi-circles that run from pole to pole passing through the equator. These are also called meridians.
- Unlike the equator which divides the earth into two equal parts and is centrally placed between the poles, any meridian could have taken to begin the numbering of longitudes. But it was divided in 1884 by international agreement to chose the zero meridian the one which passes through the royal astronomical observatory at Greenwich near London. This is the zero meridian or prime meridian, from which all other meridians radiates eastward and westward up to 180°.
- There are 360 lines of Longitude.
- Linear distance– It decreases towards the pole when it becomes zero.
- The most important function they perform is that they determine local time in relation to Greenwich mean time popularly known as world time.
International Date line (IDL):
- International Date Line is an imaginary line that runs across the surface of the earth at 1800 longitude.
- If you cross the line from east to west, you gain one day. If you cross it from west to east, you lose one day.
- From where we can cross the International Date Line – Only water and air.
- It passes through the Pacific ocean and island nation of the pacific deviating at Aleutian Island, Fiji, Samoa, and Gilbert Island.
- It is the 180th meridian which also passes from the Bering Strait between Siberia and Alaska.
- Is an International Date Line is a straight line- It is not a straight line rather it is zig-zag in nature for administrative convenience.
- How many times the International Date Line deviates from the normal 1800 longitude- 4 times.
- The Equator is an imaginary line that divides the earth int two equal halves or parts i.e. Northern hemisphere and Southern hemisphere.
- The northern hemisphere is also called the land hemisphere and the southern hemisphere is also called the water hemisphere.
- The majority of the population and climate are found in the northern hemisphere.
Apparent movement of Sun:
- Rotation is the movement of the earth on its axis. The movement of the earth around the sun in a fixed path or orbit is called Revolution.
- Revolution plus tilt of the earth is called the apparent movement of the sun.
- Because of the revolution and tilt of the earth, it appears as if the sun is moving north of equator and south of the equator.
- The northernmost and southernmost limit of this movement is represented by the Tropic of Cancer and Tropic of Capricorn in both the hemisphere.
Arctic and Antarctic Circle:
- These are the lines joining places where there is the beginning of the whole day of 24 hours or a whole night of 24 hours during the summer and winter season respectively.
- Alaska, Norway, and Sweden, etc. beyond the arctic circle.
- Developed countries are available in the temperate zone.
- The most tropical of all the continents are Africa because the tropic of Cancer, tropic of Capricorn, and equator pass through it.
- The most temperate of all the continents is Europe.
- Is Sun stationary- No.
- Is Sun stationary with respect to the solar system– Yes.