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? How to videos Why join? Day and night. The planets also rotate, or spin, around an internal axis. One manifestation of rotation is the cycle of night and day. Day after day, month after month, year after year, the alternation of night and day continues.
Sometimes it is sunny outside, and other times it is dark. In addition to rotation, day and night occur because the Earth is spherical. When a portion of the Earth faces the Sun, it is daytime.
When the same are rotates away from the Sun, it is nighttime. The cycle of light and dark is continuous except near the North and South Pole. During the Northern Hemisphere summer, the North Pole always faces the Sun, so daytime is continuous for several weeks. In this way the research is more directed and not simply a fact finding exercise.
Opportunities to make models and to manipulate the models to help students explain their ideas should be provided. The manipulation of models also assists students to view the motion of the sun, Earth and the moon from a new perspective of an observer of the whole system as opposed to their usual perspective as an observer on a very small region on the surface of the Earth. This can be used as a starting point to challenge existing ideas and to explore new ideas.
Student drawings and their associated explanations of the motion of the Earth and sun can be used to challenge their existing ideas and to help them to reflect on their understanding. To help students move from their usual perspective of an observer on a small part of the Earth to an observer outside the Earth simulation computer programs or websites can be used.
Students could present posters or diagrams suitable for display on an overhead or data projector to help them to interpret and share new perspectives with their peers. Students could also explore indigenous interpretations of the motion of the sun and Earth. Some useful sites are:. Our website uses a free tool to translate into other languages. Pluto, at the farthest reaches of our solar system, spins on its axis once every 6. Pluto is so distant from the center of our solar system that our Sun would look like a very bright star in its sky!
Why does Earth's day length change during the year? Every location on Earth experiences an average of 12 hours of light per day but the actual number of hours of daylight on any particular day of the year varies from place to place. Locations around Earth's equator only receive about 12 hours of light each day.
In contrast, the north pole receives 24 hours of daylight for a few months in the summer and total darkness for months in the winter. These two annual times of light and dark are separated by a long sunrise and a long sunset. Earth rotates on its axis; this causes us to experience day and night.
But Earth's axis is tilted As Earth orbits our Sun, the axis points toward the same location in space — almost directly toward Polaris, the North Star. This means that during Earth's movement around our Sun each year, our polar regions spend loooooooong periods pointed toward our Sun in the summer for example, July in the northern hemisphere, or December in the southern hemisphere and long periods pointed away from our Sun during the winter.
At latitudes greater than Because of this tilt and Earth's movement around our Sun, there is a time when Earth's north pole is tilting
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