In 1610, Galileo changed the way we understood both the universe and our place in it.

In the winter of 1610, the Italian scientist Galileo Galilei, using a telesc0pe he had designed, saw the night skies as they had never been seen before. He observed the face of the Moon, identified sunspots, and puzzled over the changing illumination of Venus over a period of weeks. He saw moons of Jupiter that vanished and reappeared periodically. He saw that the Milky Way is not merely a whitish band across the sky but consists of a vast number of stars, far more than the few thousand visible to the naked eye. Though human beings had been studying the sky for centuries, Galileo was the first to observe its elements at high magnification - and the conclusions he drew from those observations would change the way human beings understand both the universe and our place in it.

Astronomy is unique among the sciences because most of the objects it studies are not directly accessible; huge distances separate Earth from even nearby astronomical objects. With the exception of bodies in our own solar system, all the objects are too far away for direct sampling or spacecraft reconnaissance (techniques in use for only a few decades). Instead, information about distant objects is gleaned from the collection, analysis, and interpretation of electromagnetic radiation - light, X-rays, and other forms of energy given off by all objects in the universe. Collection of data is done through the use of a variety of telescopes far more powerful and sophisticated than the device used by Galileo some 400 years ago.

No single astronomical instrument has changed the way we perceive the universe more than the Hubble Space Telescope, launched into space by the United States in 1990. Named after the great 20th-century astronomer Edwin Hubble, the telescope sent back images that were like nothing ever seen. Since it observes from a low orbit in space, the Hubble telescope captures images undistorted by Earth's atmosphere and is able to record more clearly very faint amounts of light from the farthest and darkest parts of the universe. More than 6,000 articles based on data from the Hubble have been published, including a more accurate dating of the age of the universe (14 billion years), information on how galaxies form, the discovery of numerous extrasolar planets, as well as new theories about the nature of energy and gravity. In 2013, the Hubble will be replaced by the even more powerful James Webb Telescope, which will be sent deeper into space. (The New York Times ‘Smarter by Sunday – 52 Weekends of Essential Knowledge for the Curious Mind’)