We’ve looked at some of the attempts to communicate with extraterrestrial civilizations. How do we look for extraterrestrial intelligence. What sort of approaches are used. Well, there's no one mission to search for extraterrestrial intelligence in the SETI program. It's rather a collection of scientific programs designed to detect signals of extraterrestrial intelligence in the universe. The origins of the Search for Extraterrestrial Intelligence began in 1957 after the building of the Lovell Radio Telescope in Manchester. It was realized that once we had built radio telescopes, we could use them to do radio astronomy, but we could also use them to search for signals for alien intelligences. Cocconi and Morrison proposed that it would be worth using these telescopes to look for extraterrestrial intelligences. And this is what they said in 1959, they said that the probability of success is difficult to estimate, but if we never search, the chance of success is zero. Well, there are number of ways to search for extraterrestrial intelligences. One way is to look for optical signals, light signals, from alien intelligences. Another way is to use radio waves, the same radio waves that are used by radio stations to transmit music and other information. The problem is that there is pollution from space. There's noise, background noise in space, and also background noise from the atmosphere. So, we need to tune into specific narrow frequencies where the background noise is low, and where we have a greater chance of picking up alien signals. The first attempt to do this was made by Frank Drake in 1960. He and his colleagues used the 84 foot Tatel Telescope in West Virginia to scan for extraterrestrial radio signals. They targeted two nearby sunlight stars. They didn't find any signal but this was pioneering project. Project Ozma was the first project to try and seek out signals from alien intelligences. The problem is that radio telescopes are in high demand by astronomers and so how does a SETI program use these very expensive resources to search for alien signals. Well, there are three ways in which people do this. They rent time on existing radio telescopes for targeted searches of particular stars, carrying out very short searches, but looking at particular stars. They can also run SETI analysis from the radio telescope data of others. So, people are collecting this data, this data radio astronomy, and SETI researchers can troll through this data to hunt down signals from alien intelligences that might appear in that data. And then, of course, they can build their own new radio telescopes dedicated to the search for extraterrestrial intelligence. Project Phoenix which began in 1995 is an example of a SETI project that rented telescope time to search for extraterrestrial intelligences, and after looking at 800 stars they found no signal. They concluded that we live in a quiet neighborhood. Now this was a significant project because it was the first time a large number of stars had been systematically studied for the possibility of signals from alien intelligences. The SERENDIP Project is an example of a piggy back SETI search. The SETI researchers put an extra receiver onto the Arecibo Dish Observatory in Puerto Rico, which is used by other researchers. And so, they could use the radio telescope to search for extraterrestrial signals whilst it was being used for doing conventional radio astronomy. The only problem is you don't have much control over what stars you're looking at because, of course, that's decided by the radio astronomers doing their other research. But, the benefits of it are that you can piggy bank on a large amount of radio astronomy time, and try and seek out signals. They, too, have not found a signal from alien intelligences. Yet another project is the Allen Telescope Array. This is a new SETI search with an array of over 350 small telescopes that are planned, which combine their signal to search for radio waves in deep space. This project is housed near San Francisco, and heavily funded by Paul Allen of Microsoft. The project has not yet been completed, but it's a, it's an example of the way in which SETI researchers can establish dedicated facilities to search for signals from alien intelligences. So, as you can see, there hasn't been much success so far In finding signals from alien intelligences, and that in itself is significant. There was one signal that was detected in 1977 called the WOW signal, rather famous now, because some people believe it was a message from an alien intelligence. The WOW signal was 30 times stronger than anything that telescopes could normally detect. It was almost exactly in the place researchers expected to find a signal to come from alien intelligences, at least in the radio spectrum, and it hasn't been linked to any earth based emissions or pollution. So, on the face of it, this looks like rather an interesting signal, but the problem is it's never been detected ever again. It's never been found again, and that suggests that it is an experimental artifact, maybe an artifact of the electronics, or the radio telescope, or something else that we're seeing that has no connection with extraterrestrial intelligence. So, what have we learned. Well, we've learn that SETI has a very long history. We've learned that numerous attempts have been made to detect intelligent signals. There's been no success yet, but technology has improved, and might lend itself to larger and more systematic searches for a larger number of stars across the universe. Particularly stars that we might find host Earthlike planets in the future.
