Window dating

Posted by / 11-Oct-2016 19:38

Stand outdoors to see and feel the radiation pouring from the Sun.

Most of the energy of the Universe is transported in this way, by radiation.

These wavelengths are so short that astronomers use a small unit of distance, the "Angstrom" (A), which is 0.00000001 centimeters long.

This site, closely coupled to The Natures of the Stars and The Hertzsprung- Russell (HR) Diagram, provides an introduction to the spectra of stars and allied celestial objects.

Here we examine the principal way in which astronomers have learned so much about the stars. Pass sunlight through a triangular prism or bounce it off the finely grooved surface of a compact audio disk and see it break merrily into a band of pure sparkling color, its "spectrum," familiar in the colors of a rainbow, in light glittering from newly fallen snow, in the rings and haloes around a partly- clouded Sun and Moon, in the flash of a cut diamond, and in so many other facets of nature.

By the turn of the 20th century, spectra were being recorded photographically.

In the middle of the century, prisms were replaced by "diffraction gratings," finely ruled surfaces that produce spectra by the interference of light waves.

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The most familiar is "reflection," in which light is bounced from a surface, the light coming off at the same angle at which it hits, resulting in your undistorted face looking back at you from a mirror. When it passes into a substance, it slows and can be bent, a common phenomenon called "refraction." The effect is easily seen when looking at something through water.

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