Discovery Transcript

Most often, ground-breaking discoveries in astronomy have been made by collecting additional light. 

Galileo was introduced to the spyglass by a friend. The spyglass was developed to bring distant things on Earth closer to view. But Galileo adopted the principles behind the spyglass to make his own telescopes which he turned to the heavens. With a magnification power of only thirty, Galileo’s telescopes were weak compared to even the simplest telescopes today; but that first step toward the heavens set the course for rethinking the structure of our universe. 

The primary purpose of a telescope is to collect more light than our eyes can do on their own. In its simplest form, a telescope uses lenses to focus the light from a large opening into a discernible image. The additional light allows us to see further and fainter objects than the naked eye is able to see. 

With his telescopes, Galileo saw that several moons circled the planet Jupiter. This proved to him that the universe did not rotate around a single point.

Galileo was also able to use his telescopes to safely project an image of the Sun. Examining these images, he observed changing spots on the Sun. This convinced him that the heavens  (the space above Earth and beyond our reach) were not immutable as philosophers of the day claimed. 

Other discoveries made with the telescope, added evidence which convinced astronomers that the Sun is at the center of our solar system.  Even though we cannot feel it, the Earth is moving through space at about sixty-seven-thousand miles per hour!

After Galileo’s discoveries, astronomers began to construct larger telescopes to collect even more light. In the 19th century, a different technology was developed that extended the view of even the best telescopes of the time photography.

Whereas telescopes alone can collect light over a large space; photography allowed light to be collected for a long time. 

Our eyes process a continual flow of light. To do this they refresh many times each second.  As a consequence, the dimmest stars do not register on our minds before being replaced by new light rays. That is why the distance we can see into the heavens with the naked eye is limited.

By directing the light gathered from large telescopes onto photographic plates, dim light rays accumulate over a long period of time. As the dim rays of light continue to arrive, they are collected bit by bit until an image emerges from the darkness and becomes visible to our eyes.

The presence and nature of galaxies beyond the Milky Way were discovered through these long exposure images.  

Today, digital devices take the place of photographic film in collecting light for a long time. 

In 1993, the new Hubble Telescope set out to collect an image of the deepest region of space ever seen. In an area roughly one-tenth the diameter of the full moon the light which became the original Hubble Deep Field South image was collected for more than one hundred hours and revealed approximately three thousand galaxies.  The Hubble Ultra Deep Field image taken over 278 hours in 2004 revealed about ten-thousand galaxies. With the advanced technology of the James Webb Space Telescope the current GOODS-South deep space image reveals more than forty-five-thousand galaxies. Larger and more powerful future telescopes will continue to reveal new cosmic discoveries, far beyond what mankind could have imagined less than a century ago.