Five Billion Years of Solitude by Lee Billings Read Free Book Online Page A

yielding larger images of nearby exoplanets that, though still very low-resolution, could reveal a world’s shorelines, continents, and cloud patterns. Such telescopes would go a long way toward determining whether a planet was worthy of being anointed “Earth-like.” Based on a fragmented astronomical community, an apathetic public, a gridlocked political system, and a struggling global economy, however, none appeared likely to be built anytime soon—at least not by the federal government of the United States of America.
    Drake felt that if something could happen, somewhere it would happen, even if not right here and now. He wondered whether, if advanced cultures existed around nearby stars, they might have been watching our planet for quite some time using large space telescopes of their own.
    “I’m speculating far out on a limb here,” he said as we walked around his yard. “But I would guess that most every civilization with technological capabilities slightly beyond our own uses lenses on the order of a million kilometers in diameter to explore the universe and communicate between stars.”
    Beginning in the late 1980s, Drake had begun exploring an idea that made a lunar far side dotted with telescopes seem like child’s play.In retirement, the work had come to consume him, and now occupied much of his remaining time. He wanted to create a telescope that would surpass all others, one with a magnifying lens nearly a million and a half kilometers in diameter. Drake had found a way to transform the Sun itself into the ultimate telescope.
    A consequence of the Sun’s immense mass is that it acts as a star-size “gravitational lens,” bending and amplifying light that grazes its surface. This effect, first measured during a solar eclipse in 1919 by the astronomer Arthur Eddington, was one of the key pieces of evidence that validated Einstein’s theory of general relativity. Simple math and physics, judiciously applied, show that our star bends light into a narrow beam aligned with the center of the Sun and the center of any far-distant light source. As first calculated by the Stanford radio astronomer Von Eshleman in 1979, the beam comes into focus at a point beginning some 82 billion kilometers (51 billion miles) away from the Sun, nearly fourteen times farther out than the orbit of Pluto, and extends outward into infinity. There are as many focal points and Sun-magnified beams as there are luminous objects in the sky—imagine a great sphere surrounding our star, its surface painted with amplified, high-resolution projected images of the heavens.
    Reviewing Eshleman’s calculation, Drake had discovered that, due to electromagnetic interference generated by ionized gas in the Sun’s outer layers, ideal seeing conditions for this ultimate telescope weren’t at 82 billion kilometers, but almost twice as far out, at a distance of 150 billion kilometers (93 billion miles), a thousand times our distance from the Sun. For perspective, in June of 2011, humanity’s fastest and most-distant emissary, the Voyager 1 spacecraft launched in 1977, was just under 18 billion kilometers from the Sun, a bit more than a tenth of the distance to Drake’s ideal focus. It had taken thirty-five years to get that far from Earth. Clearly, utilizing our solar system’s ultimate telescope was a goal that could potentially take centuries to achieve. But the payoff might be worthwhile. Placed at any distantobject’s given focal point, a light-gathering telescope on the order of 10 meters (33 feet) in size could beam images back to Earth about a million times higher in resolution than what a network of large telescopes on the lunar far side could deliver. If, for instance, we wished to examine a potentially habitable planet orbiting one of the two Sun-like stars in Alpha Centauri, the Sun’s nearest neighboring stellar system, a 10-meter telescope aligned with the Sun–Alpha Centauri gravitational focus could resolve surface