Man's physical universe

xanabras

UNIT II

SECTION 2

TELESCOPES HAVE GREATLY EXPANDED MAN'S

CONCEPTION OF THE MATERIAL UNIVERSE

Like buried treasures, the outposts of the universe have beckoned to the

adventurous from immemorial times. Princes and potentates, poHtical or

industrial, equally with men of science, have felt the lure of the uncharted seas

of space, and through their provision of instrumental means the sphere of

exploration has rapidly widened.^ — George Ellery Hale.

Introduction.

Galileo's application of the telescope to astronomy was very significant

because it extended the observational basis for generalizations

in the telescope.

concerning the heavenly bodies. It revealed an unknown universe,

whose vast proportions have been expanded with each improvement

This section deals with the development of the telescope

and the information thus made available.

Telescopes Have Been Greatly Improved Since the Time of Galileo.

Galileo's telescope was a refracting type, based on the extremely

simple, familiar principle that a convex lens will bring light to a focus

by bending (refracting) it. There are two lenses in a refracting telescope

— one, the object glass, brings the light to a focus; the other, the

Piece

Fig. 3.

The principle of the refracting telescope.

eyepiece, magnifies the image. The focal length of the magnifier, or

eyepiece, in relation to the focal length of the objective, determines

the magnifying power of the telescope, and the amount of magnification

may be changed by merely changing the eyepiece.

The telescope concentrates the light which is too faint to be visible

'

Signals from the Stars, Charles Scribner's Sons, New York. 1931.

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