Subtitles section Play video Print subtitles Will ET phone home? Who knows! But we'd better pick up the call, wouldn't want to make those guys angry. Hello, I'm Ian O'Neill, space producer for Discovery News. As we discover more and more alien worlds orbiting distant stars, the question "Are we alone?" becomes more and more pressing. Surely there are other life forms out there -- perhaps even alien civilizations. Unfortunately, space is big. Really, REALLY big. In the future we might be able to send a probe to another solar system to find intelligent extraterrestrial life, but that's a tough prospect. The nearest star is around 4 light-years away and using current propulsion technology it would take us tens of thousands of years to get there. So until we develop new ways of speeding around the galaxy to find intelligent life, astronomers are thinking up some ingenious methods of detecting their presence without even leaving Earth. Here are some of my favorites: The first is an obvious one and is currently the main method behind the Search for Extraterrestrial Intelligence, or "SETI". This is to look for radio signals (or even laser pulses) that may be transmitted by ET. Humanity has been leaking artificial signals into space for over 100 years and we've been blasting radar into the solar system for many decades. This "accidental" leakage could be picked up by a nearby alien civilization. We are also beaming radio signals at stars known to have planets in orbit in the hope our electromagnetic "message in a bottle" gets picked up. What if aliens are leaking radio signals into space as well? That's why we are trying to "look out" for their signal using radio antennae. So far, there have been a few isolated cases of bizarre signals, but nothing definitive. A second cool way we may detect an alien civilization is if we observe dust and small chunks of depleted asteroids in a distant star system. Astronomers may be confused by the anomalous quantities of dust and may hint at a spacefaring alien race mining asteroids for resources. Now that we're getting rather good at detecting exoplanets, eventually we'll be able to develop telescopes that will be able to analyze the chemical makeup of atmospheres of small planets orbiting very close to their stars. Astronomers can use spectroscopy to identify the fingerprint of certain atmospheric chemicals. Say if they detected chemicals like chlorofluorocarbons, or CFCs? Humanity has been struggling with CFCs for some time and they were commonly used in pressurized containers like hairspray and refrigerators -- but when released into the atmosphere the chemical breaks down our protective ozone layer. But CFCs are ONLY created through industrial processes. So imagine if we saw CFCs in the atmosphere of an exoplanet! It could mean only one thing: industrialized aliens! Many other chemical groups that have no known natural production mechanism would also make for a fascinating discovery. Astronomers could also search for astronomical signatures of alien mega-engineering projects like Dyson spheres, huge artificial planets or even extreme stellar power stations that use black holes as fuel! This search is called, perhaps unsurprisingly, the Search for Extraterrestrial Technology, or simply "SETT." But ultimately, the only sure-fire way we'll find any form of alien life -- intelligent or otherwise -- is to actually get out there. In the short term, we need to send robots and eventually humans to planetary bodies in the Solar System to seek out basic lifeforms -- perhaps even complex lifeforms in the oceans of Europa... who knows! But if we do happen to stumble across an intelligent alien civilization, or if they happen to stumble across us, let's just hope they're friendly. Do you think we should seek out intelligent aliens? Or should we just keep quiet to avoid being attacked? Tell us in the comments below, and don't forget to subscribe for more DNews.