Ever since we realised that space travel was possible mankind has been intrigued by what has become known as the Fermi paradox. In 1950 Enrico Fermi posed the question in an informal discussion on the subject of extra terrestrial civilisations (ETCs) “If they exist, where are they?”. To bring this a little more into today’s context, we now know that rather than being an exception, planetary solar systems seem to be the norm in our neighbourhood.
To date 891 extra solar planets have been discovered including 262 that might be habitable. Planets are identified by looking at the light from a star and searching for transits or more specifically, the dimming of a star caused by a planet passing in front of it from our viewpoint.
So if there are all these potentially inhabitable planets out there in our galactic neighbourhood, why hasn’t anyone come to see us or at least said “Hi!”?
Until now The Search for Extraterrestrial Intelligence (SETI) project has looked for ETCs using radio telescopes. Other than the now famous “Wow!” signal picked up in 1977 by the Big Ear Radio Telescope at Ohio State University, we haven’t heard a peep out of E.T. However, radio frequencies may not be a great way to look for ETCs. We assume that because we use radio frequencies to communicate then CETs would as well. This may be entirely erroneous for a couple of reasons:
– Radio frequencies travel at the speed of light and as such, aren’t a great method for communicating over stellar distances because a signal from the nearest star other than our Sun would take years to arrive.
– Civilisations may only use radio frequency communication for a very short time during their technological development. The chances of us just happening on that period in history during which they’re using that form of communication are probably infinitesimally small.
The Colossus telescope is interesting because it will look for variations in the infrared spectrum which indicate the thermal signature of a civilisation. In other words, people use power and this power can be seen from space as heat. The problem is that this thermal signature is really hard to pick out with current technology because the heat of the host star tends to mask it. Build a big enough telescope with powerful enough optics and some very clever software and you can disentangle the planet’s thermal signature from that of its host star. If a planet has an unusually high thermal signature it’s good evidence that an ETC may exist on its surface. As the technology progresses we might even be able to see the distribution of heat across the planet’s surface.
The only snag is that building a football sized telescope costs quite a bit of money…around a billion US dollars. So whether Colossus ever gets enough funding remains to be seen. If it is ever built though, the resulting data could at last provide us with evidence as to whether or not we’re alone in the cosmos.