In the late 1970s, astronomers had a problem: The scale of their telescopes no longer matched the size of their ambitions. To see deeper and deeper into our universe's past, they needed a bigger telescope. To build a bigger telescope, they needed a larger mirror, but mirrors larger than 5 meters had the pesky habit of deforming, producing bad images and frustrating attempts to surpass the resolution of the 5-meter Hale Telescope, first built in 1948.

"Many people thought [the Hale] was the biggest telescope that would ever be built," said Mike Bolte, director of the University of California Observatories.

When the Russians built a 6-meter telescope by the old methods in 1976, it produced awful, distorted images. Scientists across the world realized that a new design for the telescope had to be created.

The scientist who eventually found the key disruptive telescope technology was an unlikely UC Berkeley physicist, Jerry Nelson (now at UC Santa Cruz).

"When giving a talk, his manner was so matter-of-fact you would think he was discussing a new offering of municipal sewer bonds, not the world's largest telescope," the Los Angeles Times wrote of him. "Yet he was a persistent and capable scientist with a gift for devising elegant solutions to unexpected problems."

The elegant solution he designed — to build 36 smaller mirrors and fuse them together like a honeycomb — underpinned the construction of the Keck Observatories' twin 10-meter telescopes on Mauna Kea in Hawaii.

"Everybody thought that was an extremely risky thing. There was a big debate. Nobody trusted that it could be done," Bolte said. "The prototype was the first Keck 10-meter telescope. It's really a breakthrough that seems obvious, but it wasn't."

Telescope design has seen two distinct periods in the last hundred years. First, astronomers switched away from the lens-using refracting telescopes to mirror-based reflecting telescopes. This opened the way for the Mount Wilson Observatory's 1.5-meter telescope in 1908, the 2.5-meter Hooker in 1917, and the Hale telescope at Palomer in 1948. The Keck inaugurated the next era of telescope building via segmented mirror or mosaic construction.

In fact, Nelson's construction method and other segmented mirror designs have proven so flexible and scalable that three new telescopes that are more than twice the size of the world's current record-holder are preparing to leave the drawing board and enter the construction phase. Now, the Giant Magellan Telescope at 24.5 meters, the Thirty Meter Telescope, and the 42-meter European Extremely Large Telescope are expected to be completed within a decade. In the glacial world of large 'scope building, this is just around the corner.

These telescopes have two goals that could redraw our place within the universe, much as previous discoveries — like Edwin Hubble's discovery with a previous world-record holding telescope that the Milky Way was just one galaxy among many — redefined the centrality of our own galaxy.

First, the telescopes will bring the study of Earth-sized planets around local stars within human reach. We will be able to determine how rare Earths are, and by extension, how likely Earth-like life is to exist elsewhere in the galaxy. Second, by gathering more light than ever before, astronomers will be able to detect fainter objects that are further back in our universe's history. They hope that the new telescopes will see "first light," when the first stars formed out of the primordial universe's post-Big Bang mass.

Working in tandem with the segmented mirror design is a complementary technology borrowed from the military called adaptive optics. Adaptive optics allows astronomers to account and correct for disturbances in the Earth's atmosphere. It's a complex task that requires measuring the air within the telescope's view for temperature variations and adjusting the Keck's mirrors to compensate 2000 times a second with tiny controllable magnets.

"Behind each magnet, there are a series of acoustic voice coils that can refresh the amount that that magnet is pulling at a rate of 500-1000 Hz. At that frequency, we can correct for turbulence in the Earth's atmosphere that occurs," said Peter Wehinger, staff astronomer at the Steward Observatory Mirror Lab, which is building mirrors for the Giant Magellan Telescope.

Driven by faster and faster computers, the technology has allowed ground-based telescopes to rival and in some cases surpass the Hubble Space Telescope, and its future successor the James Webb Telescope.

"All this really depends on things like Moore's Law, fast computers, technology to change shape of mirrors. We're like slaves to technologies," said Taft Armandroff, director of the Keck Observatory. "With the Keck we can get images with a better spatial resolution than we can get with Hubble Space Telescope."

With the technological challenges largely out of the way, what the new telescope projects need now is money. And when it comes to funding the world's largest telescopes, astronomers have often turned to philanthropists.

George Ellery Hale was a master of funneling astronomical amounts of private money — particularly from Andrew Carnegie — into astronomy projects. His fundraising skill was responsible for the Mount Wilson and Hooker telescopes, both world record holders. While the Keck's funding history is convoluted, it eventually was built almost entirely with a single family's money.

"All the way back to 400 years ago, there was some patron that paid for Galileo's telescope and that started an incredible trend that forefront telescopes have almost always been privately funded," said UC's Bolte.

The Thirty Meter Telescope appears to have found that donor, in Intel's Gordon Moore. The Gordon and Betty Moore Foundation pledged $200 million for the construction of the telescope late last year.

The Giant Magellan Telescope is still waiting for its Keck or Carnegie or Moore, and they could struggle with the current economic climate.

Still, the odds are that at least one of these telescopes will be built by 2018 and we could soon be exploring reaches of the universe — and time — that no human has ever been seen before.

"The science questions are more compelling than ever. There's so much to explore. It's really exciting to get these new tools," Armandroff said.

See Also:

Image: Giant Magellan Telescope. Courtesy of Carnegie Observatories.

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