Ask a science teacher: What creates the wind?

Wind is caused by a difference in pressure from one area to another area on the surface of the Earth. Air naturally moves from high to low pressure, and when it does so, it is called wind.

Generally, we can say that the cause of the wind is the uneven heating of the Earth’s surface by the Sun. The Earth’s surface is made of different land and water areas, and these varying surfaces absorb and reflect the Sun’s rays unevenly. Warm air rising yields a lower pressure on the Earth, because the air is not pressing down on the Earth’s surface, while descending cooler air produces a higher pressure.

But there are many other factors affecting wind direction. For example, the Earth is spinning, so air in the Northern Hemisphere is deflected to the right by what is known as the Coriolis force. This causes the air, or wind, to flow clockwise around a high-pressure system and counter-clockwise around a low-pressure system.

The closer these low- and high-pressure systems are together, the stronger the “pressure gradient,” and the stronger the winds. Vegetation also plays a role in how much sunlight is reflected or absorbed by the surface of the Earth. Furthermore, snow cover reflects a large amount of radiation back into space. As the air cools, it sinks and causes a pressure increase.

And wind can get even more complex. Some parts of the Earth, near the equator, receive direct sunlight all year long and have a consistently warmer climate. Other parts of the Earth, near the polar regions, receive indirect rays, so the climate is colder.

As the warm air from the tropics rises, colder air moves in to take the place of the rising warmer air. This movement of air also causes the wind to blow. It’s a dynamic, complex mechanism, which is why weather forecasting is not quite a precise science.

Today we see windmills, used to make electricity, in operation in all parts of the United States, but especially along our coasts. Coastal regions tend to have fairly strong winds blowing in from ocean to land during the day and out from land to ocean during the night. The cause of this phenomenon is that land heats up and cools down faster than water, again creating a pressure gradient.

From the book, "Ask a Science Teacher: 250 Answers to Questions You’ve Always Had About How Everyday Stuff Really Works"; Copyright © Larry Scheckel, 2013. Publishes December 17; available wherever books are sold.

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Astronomy Teacher Finds Hubble Telescope's Hidden Treasure

A Connecticut astronomy teacher has uncovered a dazzling view of a satellite galaxy to the Milky Way while exploring the "hidden treasures" of the Hubble Space Telescope.

The new Hubble photo, released Thursday (Jan. 17), shows an intriguing star nursery dotted with dark dust lanes in the Large Magellanic Cloud about 200,000 light-years from Earth. The Hubble observation used to create the image was discovered in the telescope's archives by Josh Lake, a high school astronomy teacher at Pomfret School in Pomfret, Conn., as part of the "Hubble Hidden Treasures" contest that challenged space fans to find unseen images from the observatory.

Hubble officials also released an eye-popping video tour of the Large Magellanic Cloud, which zooms in on the region highlighted in Lake's photo.

Lake won first prize in the Hubble photo contest with an image of the LHA 120-N11 (N11) region of the Large Magellanic Cloud. Hubble officials combined Lake's image with more observations of the N11 region in blue, green and near-infrared light wavelengths to create the new view.

"In the center of this image, a dark finger of dust blots out much of the light," Hubble officials said in an image description. "While nebulae are mostly made of hydrogen, the simplest and most plentiful element in the universe, dust clouds are home to heavier and more complex elements, which go on to form rocky planets like the Earth." [Hubble Telescope's Hidden Treasures: Winning Photos

The interstellar dust in N11 is extremely fine, much more so than household dust on Earth. It is more similar to smoke, researchers explained.

The Large Magellanic Cloud, or LMC, is one of two small satellite galaxies of the Milky Way (the other is the smaller, aptly named Small Magellanic Cloud). Because of its relatively close proximity, the Large Magellanic Cloud has long been used as a sort of cosmic laboratory to study how stars form in other galaxies.

"It lies in a fortuitous location in the sky, far enough from the plane of the Milky Way that it is neither outshone by too many nearby stars, nor obscured by the dust in the Milky Way’s center," Hubble officials said in a statement. "It is also close enough to study in detail … and lies almost face-on, giving us a bird’s eye view."

In addition to the N11 region, the Large Magellanic Cloud is also home to the spectacular Tarantula nebula, the brightest nearby star nursery, Hubble officials said.

The Hubble Space Telescope has been snapping spectacular photos of the universe since 1994 and is a joint project by NASA and the European Space Agency. This month, NASA officials said the long-lived space observatory could potentially last through 2018.

You can follow SPACE.com Managing Editor Tariq Malik on Twitter @tariqjmalik. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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