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Learn about planets outside our solar system through Exoplanets and Alien Solar Systems by Tahir Yaqoob, Ph.D., a book in our online store book collection.

ExploraTour - Looking at the World in a Different Light


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Windows to the Universe original artwork.

Radiant energy, called "electromagnetic radiation", is released every time an electron slows down, changes its orbit around an atom or vibrates back and forth. Through these changes in its motion, the electron creates a changing electric field.

It is an observed fact that when an electric field is changing, a magnetic field appears. And when a magnetic field is changing, an electric field appears. This is how an electromagnetic wave works and how it is able to travel immense distances from faraway stars to our small solar neighborhood. The wave's changing electric field produces a changing magnetic field which in turn creates another changing electric field and on and on and on.

If you observe the electric and magnetic fields as the wave passes by, you will note that the size of the fields go up and down again and again. The distance in space between peaks in the field is called the "wavelength". The number of peaks that a non-moving observer counts per second as the wave passes by is called the "frequency".

The electric and magnetic fields in the wave point in directions that are 90 degrees apart and both fields point 90 degrees away from the direction the wave is moving.

The most familiar form of radiant energy is visible light.


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ExploraTour - Looking at the World in a Different Light

Even though the sleeping man is no longer on the bed, you can still see where he was lying down. The heat from his body warmed up the bed sheets which are now radiating infrared light toward your eyes....more

ExploraTour - Looking at the World in a Different Light

All warm objects radiate in the infrared. The warmer the object, the higher the frequency and intensity of the radiation. Very hot objects give off other types of radiation in addition to infrared. Click...more

ExploraTour - Looking at the World in a Different Light

Your eye is a wonderful detector of visible light. Different frequencies of light produce different sensations in the eye which we interpret as colors. Our eyes detect light by using light sensitive components...more

ExploraTour - Looking at the World in a Different Light

Imagine you found a pair of special glasses that not only gave you telescopic vision but gave you the ability to see all forms of radiant energy. The universe in visible light contains all the familiar...more

ExploraTour - Looking at the World in a Different Light

This is a volcano on the island of Miyake in Japan. It has erupted, sending hot lava and ash into the air, a total of ten times. The time after one eruption until the next occurred was about twenty years...more

ExploraTour - Looking at the World in a Different Light

The awesome power of a giant black hole was revealed by looking at this galaxy in three different types of light. The picture that you see is of Centaurus A, a very peculiar galaxy. A galaxy is just a...more

ExploraTour - Looking at the World in a Different Light

This is a plant in Gary, Indiana where power is made. We use power to run things like television sets, radios, lights, and microwave ovens. The picture looks very strange because it was taken in infrared....more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part by the National Science Foundation and NASA, our Founding Partners (the American Geophysical Union and American Geosciences Institute) as well as through Institutional, Contributing, and Affiliate Partners, individual memberships and generous donors. Thank you for your support! NASA AGU AGI NSF