Why earth experiences day and night

Understandably, students have a strong tendency to interpret reality only according to the way it is perceived from their own perspective. This has implications for their understandings of ideas that represent objects on a very large scale like the solar system. They observe the world from their own place on a very small region of the Earth. They often find it difficult to comprehend distances in the order of their own country and consequently larger distances like those involved with the solar system are often unimaginable for them.

In addition, students observe motion from their own point of reference. In order to understand the motion of the sun and Earth they must imagine a different point of reference. This can make ideas in this area very challenging for students to grasp. The views held by students about the shape of the Earth are varied and often unique to the individual. Even though students can often articulate that the Earth is a sphere, upon further investigation they often believe in fact that the Earth is how they perceive it, flat.

Some children view the Earth as round or circular as opposed to spherical see diagram 1 below. As Earth continues its spin, we are moved to the side facing away from our Sun, and we have nighttime. If we were looking down on Earth from above the north pole, we could see that Earth rotates counterclockwise, and we would watch daylight and darkness sweeping across our globe from east to west.

Do other planets have day and night? All the planets in our solar system spin on their axes so does our Sun! There are differences, however, in the length of day and night — the cycles are made even more complex by the tilt of a planet's axis and its rate of orbit. Some planets rotate faster than Earth and some rotate slower. Mars has a day and night cycle similar to Earth. Mars rotates on its axis once every Venus turns once on its axis every Earth days which is only slightly longer than it takes for Venus to go around the Sun!

Mercury's day and night cycle is more complex. Mercury rotates one-and-a-half times during each orbit around the Sun.

Because of this, Mercury's day — from sunrise to sunrise — is Earth days long. The larger planets spin much faster. All measurements of how far East and West places are are taken from this line. We call these measurements longitude. The sun has travelled half way across the sky and still has half way to travel.

For people living on the far side of the world, when it is midday in London, it will be the middle of the night for them. It is more useful for them to set their clocks by when the sun will be visible where they live than when it will be visible in London.

Most time zones are set as an exact number of hours ahead of or behind the time in London. Most countries prefer to be in only one time zone. That way all the schools and offices open and close at the same time and nobody gets confused. The USA is so big that it is in several time zones. On the far side of the world from Greenwich is the International Date Line. On the western side of the line the time is 12 hours ahead of London and on the eastern side of the line the time is 12 hours behind London.

This means that on the western side of the line it is one day later than on the eastern side of the line. Sometimes we change the time of the clocks so that we can make more use of the hours of daylight. If we used the same time all year around in Britain then, in the summer, the sun would rise at am and set at pm. Not many people are awake at am, but lots of people are awake after pm.

We set our clocks forward one hour in the spring so that the sun rises at am and sets at pm and we set them back one hour in the winter. This is called summer time.

Find out where it is daytime and where it is nighttime right now. Colour in some pictures of nocturnal animals. Try lots of different seasons games. Play a day and night simulation game. Spot animals in the dark in Night Light, an interactive game. Make your own paper sundial. Complete a World Day and Night Workshop online to understand more about day and night. Need help? You are almost done. Put the Philippine flag in place and also the Brazil flag opposite it. Make the room completely dark.

The flashlight should not move. When light strikes the Philippine flag day , take note that no light falls on Brazil night. Then turn the globe eastward from left to right slowly until their positions reverse. Brazil now experiences daylight while Philippines experiences nighttime.

In the end, the students should understand that the rotation of the Earth causes the occurrence of day and night. In addition, they should understand that two people on opposite sides will not experience simultaneous daytime or night-time.

Explore day and night of Earth. At the end of this exercise, students should be able to: Describe how the Earth is tilted and rotates about its axis. Explain how the rotating Earth results in day and night. Explain how your location on Earth affects the length of day and night at various times of the year.

A The Earth rotates upright B The Earth rotates while tilted on its side C The Earth speeds up and slows down while spinning 5 How many degrees is the equator of the Earth tilted relative to ecliptic?