Book 8, Question 127
Why Are Many Top Telescopes on Mountains?
Many top telescopes are on mountains because the air up high is thinner, drier, and steadier! Higher, darker sites sit above much of the blurry, wet air and the glow of city lights. Clearer, steadier views win.
More fun facts
- Many of the best spots for telescopes that see visible light are on mountaintops, out in the country.
- Far from towns, there is less light pollution, and any lights nearby end up below a mountaintop telescope.
- Layers of air act like lenses and bend starlight. On a mountaintop there is less air above you to blur the view.
- The ALMA telescope in Chile has 66 antennas on a high, dry plateau about 16,400 feet (5,000 meters) up.
- The South Pole Telescope sits on a thick ice sheet almost 10,000 feet (3,000 meters) high.
- The twin Gemini telescopes, one in Hawaii and one in Chile, can observe the whole night sky together.
- Not every observatory is up high. Japan's Super-K detector lies more than half a mile under a mountain.
Sources: Exploratorium, National Geographic, Smithsonian Magazine
Questions kids ask
Why does dry air help telescopes?
Many top observatories, like ALMA, sit on high, dry ground where there is less air and water above to get in the way.