Eavesdropping on the Universe

There’s a law of unintended consequences that seems to operate everywhere: if you find a way to do or discover something, there’s almost always another thing you can do or discover with your method. So, for example, when Ball Aerospace was developing detectors for an instrument on the Hubble Space Telescope that would look at distant objects bright in ultraviolet light, someone figured out that you could use the same detectors in another setting: to detect breast cancers. You’ve probably done something like that around your home—found a different use for a familiar tool. My dad used to tease us kids (I have five sisters and two brothers) that we could be fair mechanics, just using hairpins.

The image below is a shot of an array being built in Western Australia called the Mileura Wide-field Array (now renamed Murchisan Wide-field Array. A consortium of groups is working on this, including MIT Haystack Observatory near my home. I’ve been working with Haystack on some projects, and have been following the MWA with great interest.

MWA is being built to survey the sky at radio frequencies below 1.6 GHz. What can we see at these low frequencies? Since it’s located in a radio-quiet area (free of interference from our own radio, TV, satellite radio, military radars, etc.), this array is expected to see objects and events in the dynamic radio sky—the active cores of galaxies, for example, or variations in the light coming from quasars. It should be able to help astronomers detect signals from neutral hydrogen that existed back when the universe was being lit up by radiation from the first stars, more than 13 billion years ago—during a time called the “Epoch of Reionization.” (You can read more technical details about MWA at the Low Frequency Demostrator array pages.

So, what unintended consequences do you think might happen as astronomers use MWA to scan the universe? It turns out that the array will be sensitive to waves of light (particularly in radio and radar frequencies) that are streaming from other civilizations around any of the 1,000 nearest stars that happen to have intelligent life on them.

Astronomer Avi Loeb (of Harvard-Smithsonian Center for Astrophysics) and a team of researchers are proposing to use MWA to search between 80-300 MHz (wherein our civilization’s broadcast signals—including military radars— exist) to search for signals similar to those that WE put out to the cosmos. Dr. Loeb presented his ideas this morning at AAS, showing once again that when you build a tool for one purpose, even in astronomy, you can almost always find another equally good and pretty darned exciting use for it to make some cool discoveries. Stay tuned!