What is a knot? History of sailing
Phoenician ship A knot is a way to measure how fast a ship is travelling on the ocean or how fast a boat is going on a river. A knot [...]
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09, 2017
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08, 2017
Where do tornadoes come from? – Weather – Earth science
A tornado wrecked a town in northern France When there's wind coming from more than one direction at the same time, sometimes the air begins to spin around in one place. This [...]
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08, 2017
Why does it rain? Weather – Earth science
Thanks to Rocbike for the great picture! When the Earth first formed, about 4.5 billion years ago, it didn't rain here. Until about four billion years ago, Earth was too hot for raindrops to form, [...]
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08, 2017
Nimbus clouds – Rain clouds – Weather
Cumulonimbus clouds are a type of nimbus cloud What is a nimbus cloud? Nimbus clouds often mean that a thunder storm is brewing: there may soon be thunder and lightning. Get out of [...]
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08, 2017
What makes thunder and lightning? – Weather science
A bolt of lightning in the sky Hot air and cold air are constantly moving around the Earth, as the hot air rises and the cold air sinks - that's what [...]
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08, 2017
Why does earth have weather? – Earth Science
A thunderstorm in South Africa The weather on Earth happens because of the evaporation and condensation of water, and because of the spinning of the earth and the tilt of the earth on its axis. Does it [...]
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08, 2017
What causes wind (Hot air rises) – Wind and weather Science
Hot air balloon - hot air rising is what causes wind Hot air is lighter than cold air When something is hot, its molecules are farther apart than when it is cold. When air [...]
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08, 2017
Kleenex balloon – Hot air rises project
Making your own hot air balloon (Thanks to American Aircraft Modeler) How to make a hot air balloon You can make your own tiny hot air balloon to see how [...]
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08, 2017
What’s the atmosphere? Weather science
Earth's atmosphere: Did the Earth look like this right after it cooled down? What is the atmosphere? The atmosphere is the air that is wrapped all around a planet. Read more [...]
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08, 2017
What is gravity? Physics
What is gravity? The Moon orbiting Earth (taken from space) - NASA What does gravity do? Gravity attracts all objects towards each other. Gravity has been around since the very [...]
