the earth

SCIENCE

Today in science we have learned why do we have day and night.

The Earth takes 24 hours to make one complete turn. We have day and night because the Earth rotates. It spins on its axis, which is an imaginary line passing through the North and South Poles. The Earth spins slowly all the time, but we don't feel any movement because it turns smoothly and at the same speed.

At any time half of the Earth faces the sun. This part has day. The other half of the Earth faces away from the Sun. It receives no light. It is dark and has night.

The sun is the source of light for day.

The Sun does not move. It seems to move across the sky starting in the east in the morning, moving toward the south at noon, and then toward the west as the day ends.

It is the Earth turning that makes it seem as though the Sun is moving.

Daytime starts at sunrise and ends at sunset.

Day length (length of the day) is the time from sunrise to sunset when it is light.Daylight hours are exactly opposite for the Southern and Northern Hemispheres.

The Equator and Prime Meridian are circles that stretch all the way around the Earth.

The Equator separates the Northern and Southern Hemispheres. The Equator is at 0° latitude.

The Prime Meridian separates the Eastern and Western Hemispheres. The Prime Meridian runs through Greenwich, England and is at 0° longitude.

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Day length at the Equator At latitude 0° (the Equator) day length will be approximately 12 hours. Areas on the Equator have a constant 12 hours of day light all year round.

Moving away from the Equator As latitude increases to 80° (polar circles - north or south) day length can be seen to increase to 24 hours or decrease to zero (depending on time of year).

Land of the Midnight Sun and Polar Winters where the sun never rises.

In summer, the regions north of the Arctic Circle enjoy between one and two months of Midnight Sun – 24 hours of sunlight due to the relative tilt of the Earth towards the Sun. It is the opposite below the Antarctic circle (South Pole).

In winter, the regions north of the Arctic Circle experience a 24-hour period when the sun never rises above the horizon. This is known as the Polar Night. Again it is the opposite below the Antarctic circle (South Pole).Latitude and Longitude

Any location on Earth is described by two numbers -- its latitude and its longitude.

What is latitude?

Latitude tells you how far north or south of the Equator you are located.

It is measured in degrees ranging from 0° at the equator to 90° at the poles. Latitude lines are imaginary lines that are marked every twenty degrees north and south of the equator.

The Equator at 0° latitude divides the Earth into the northern and southern hemisphere.

What is longitude?

Longitude is the location of a place east or west of a north-south line called the prime meridian.

Longitude is measured in angles ranging from 0° at the Prime Meridian to 180° at the International Date Line. The longitude lines, or meridians as they are sometimes called, are imaginary lines every 20° east or west of the Prime Meridian.

The Prime Meridian divides the Earth into the eastern and western hemisphere.

Locations on similar latitudes have similar day lengths where as different latitudes have different day lengths. Depending on the time of year, day length will either increase or decrease as locations progress north or south.

Day length at the Equator At latitude 0° (the Equator) day length will be approximately 12 hours. Areas on the Equator have a constant 12 hours of day light all year round.

Moving away from the Equator As latitude increases to 80° (polar circles - north or south) day length can be seen to increase to 24 hours or decrease to zero (depending on time of year).

Land of the Midnight Sun and Polar Winters where the sun never rises.

In summer, the regions north of the Arctic Circle enjoy between one and two months of Midnight Sun – 24 hours of sunlight due to the relative tilt of the Earth towards the Sun. It is the opposite below the Antatarctic circle (South Pole).

In winter, the regions north of the Arctic Circle experience a 24-hour period when the sun never rises above the horizon. This is known as the Polar Night. Again it is the opposite below the Antatarctic circle (South Pole).