Having telescopes on Earth that allowed people to look at the relatively distant heavens was one of the most transforming (and controversial) developments in human history. Establishing that the Earth is not at the center of the solar system, let alone the whole universe, was an affront to the Church that nearly cost Galileo his life in the 1600s.
The ability to put Earth telescopes in space, such as the famed Hubble telescope, could also be described fairly as transformative, at least within the worlds of astronomy and astrophysics. Clearly, though, not all telescopes can be dispatched to space and operated remotely. There are advantages of space telescopes and there are advantages of Earth-based telescopes; which you use depends on your means, your goals and your general interests.
Telescopes and Human Knowledge Expansion
In addition to demonstrating conclusively that the Earth and the other planets revolve around the sun, and that the solar system in turn spins around the center of the Milky Way galaxy, ground-based telescopes have bolstered human knowledge about distant objects as the telescopes have become more powerful.
In addition to providing an ever-larger range and pool of space objects to catalog and classify, telescopes have both indirectly and directly helped scientists understand more about "invisible" concepts, such as gravity, the speed of light and the basic laws of physics that govern everything known to exist.
Advantages of Earth-Based Telescopes
Scientists and amateur astronomers have had time to work out the pros and cons of ground-based telescopes for several centuries now. The man advantages of today's Earth-based telescopes are fairly obvious – bigger and better lenses and means of manufacturing them, for example – but the ways in which Earth-based telescopes are still superior to their "overhead" counterparts cannot be ignored, either.
One plain example of an advantage of a telescope that is based on the Earth is the same advantage carried by all systems without remote components: If the telescope needs to be repaired or otherwise services, it can be done by human beings on the ground under normal conditions of gravity and oxygen.
Most other advantages of Earth telescopes also revolve around the notion of convenience (or avoiding extreme inconvenience). Scientists note that Earth telescopes are not at risk of being damaged by flying space debris, for obvious reasons.
Example of a Ground-Based Telescope: Large Binocular Telescope
The Large Binocular Telescope (LBT) at the University of Arizona in the southwestern U.S. is an example of a "terrestrial" telescope with advantages that have allowed it to be a part of major discoveries. Online since 2002 after being made in Italy, the telescope was the first on the ground to capture images of a distant planet in the process of being formed, just as Earth was formed some 4.5 to 5 billion years ago.
Advantages of Space-Based Telescopes
For optical telescopes such as the ones being discussed, the only real advantage of putting a telescope in space is that it can do its job much better there. This is not because such telescopes are materially closer to their objects of inquiry, but rather because the Earth's atmosphere can distort images so badly. This is why such telescopes are often built at very high altitudes if possible, such as the Mauna Loa Observatory in Hawaii.
- Telescopes that capture infra-red rays, x-rays and gamma rays, which cannot be seen but are very important in physics, have to be in space because the atmosphere occludes them completely.
Example of a Space-Based Telescope: The Hubble Telescope
The Hubble Telescope was a worldwide phenomenon even before it was launched into space, so anticipated was its ability to capture dazzling imagery from miles above Earth, where its optical apparatus would be unencumbered by the distorting effects of the Earth's atmosphere.
- NASA Jet Propulsion Laboratory: Have Telescopes Changed Our View of the Universe?
- University of Arizona: Space Versus Ground Telescopes
- Cornell University Astronomy: What Are the Advantages and Disadvantages of Using a Telescope in Space?
- Space.com: Why Are Space Telescopes Better Than Earth-Based Telescopes?
- NASA/Getty Images News/Getty Images