This idea would turn the Earth into a giant space telescope

The ‘terrascope’ would use a detector on a satellite to collect light bent by Earth’s atmosphere

The bending of starlight caused by Earth’s atmosphere could be used to create a giant telescope, one scientist suggests. It would require placing a detector out in space (illustrated).

James Tuttle Keane

Telescopes keep getting bigger — and more expensive. Researchers with the European Southern Observatory are building one telescope in Chile, for instance, called the Extremely Large Telescope. It will cost more than $1 billion. But one astronomer thinks there might be a better way. He suggests turning our entire planet into a telescope lens. It would rely on Earth’s atmosphere to bend and focus light.

When it hits Earth’s atmosphere, starlight will bend, or refract. That bending concentrates the rays. It focuses them in a region of space on the opposite side of the planet. Put a spacecraft in the right place and it could catch the focused rays, says David Kipping. He’s an astronomer at Columbia University in New York City. A good place to put the spacecraft is about 1.5 million kilometers (900,000 miles) from Earth, he estimates. He describes such a system as a “terrascope.”

Instruments aboard the spacecraft might be able to collect more light from dim objects than is possible with current telescopes on Earth. That means the terrascope might be able to make ultrasensitive measurements. Such measurements might reveal, for instance, new features of exoplanets, he says. These features might be something like mountain ranges or clouds.

Kipping has outlined the idea in a paper accepted in Publications of the Astronomical Society of the Pacific. But some scientists question the idea’s merits.

Slava Turyshev is an astrophysicist. He works at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. The new concept is not feasible for a variety of reasons, he suspects. For instance, it would be difficult to block out unwanted light from Earth. That light would make it hard to see the stars. Another problem: The images could be blurry. That’s because light would be bent by a different amount depending on how high in the atmosphere it travels.

Other researchers are a bit more optimistic. “There’s clearly a lot of work to do before we’ll know if it will work,” says Martin Elvis. He’s an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. “Even if this neat idea doesn’t pan out, this is the kind of creative thinking that will get astronomy out of the linear thinking trap of wanting a bigger version of what we already have.”

Physics writer Emily Conover studied physics at the University of Chicago. She loves physics for its ability to reveal the secret rules about how stuff works, from tiny atoms to the vast cosmos.

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