Telescopes from the Ground Up

Galileo’s Refractor

The first telescope used the same principles that all telescopes would rely upon. The combination of the two lenses gathered more light than the human eye could collect on its own, focused it, and formed an image. Because the image was formed by the bending of light, or refraction, these telescopes came to be known as refracting telescopes or, simply, refractors.

Galileo’s best telescope magnified objects about 30 times. Because of flaws in its design, such as the shape of the lens, the images were blurry and distorted. But it was good enough for Galileo to explore the sky.

Seeing is believing

As his investigations progressed, Galileo began to make enemies. Some people argued that the telescope made people see illusions. Others claimed that the planets’ details couldn’t be seen with the naked eye, and therefore didn’t matter.

The hostility arose from a dispute about the way the universe worked. One belief, outlined by the astronomer Ptolemy long ago, held that the Earth was the center of the universe, and that everything revolved around it. The more recent view, proposed by the astronomer Copernicus, put the Sun in the center of the universe.

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