Seeing the man on the moon

The inner Solar system (only terrestrial planets) as seen at 50 light years away from the Sun by the Colossus. The Sun to Mars distance will be seen at the angle of about 100 milliarcseconds. The sizes of the planets and the Sun on this image are not scaled with the distance.

Something big is up on Haleakala.

At Friday’s lecture at Maikalani, Jeff Kuhn, head of the Haleakala Observatory of the UH Institute for Astronomy, talked about The Colossus, which would be the world’s largest telescope. Kuhn modestly said he is only part of an international team,  but he’s the project leader.

In the past, every new largest telescope has been able to see more and more of the night sky. The Colossus would turn this approach on its head — it is designed not to see the Universe but to zero in on a single star.

The purpose would be to identify advanced civilizations. As Kuhn explained, as a civilization gets bigger, it acquires more data. Data requires energy to keep. Eventually, such a civilization would use up more than 1% of its star’s light. (Earth is at about 0.4% now.)

According to the laws of thermodynamics, using energy degrades it, changing light to heat. So to find one of these advanced civilizations, you need to see an extrasolar planet in its stars Earth-like “habitable zone” that is optically dim but bright in the infrared. Even the largest telescopes today cannot come near doing this, because they are too small and too general.

The Colossus would be a circle of 60 8-meter mirrors, arranged in a collector close to 250 feet across.

Its location, if built, is open. Hawaii and Chile would be the best sites.

Its cost would be a billion dollars, more or less. All private money. In fact, said Kuhn, for 150 years, each successive largest telescope (currently the Kecks on Mauna Kea) has been built with private money.

Although designed for a special purpose, the Colossus could do other things as well. It could see a man on the moon. A man your size — 2 meters.

How soon? Technically, Kuhn said, if the money is available, it could happen in 5 years. The 60 closest stars would have to be observed every night for several years to accumulate the tiny differences that would detect a planet that absorbs light and emits heat.