The Golden Age of Science Fiction in the 40s and 50s introduced the idea of, and interest in extraterrestrial life into the popular psyche. The idea that alien life forms could be out there in the universe has an almost universal appeal. Space is so big that anything could be out there. It seems rather reasonable that there could be alien life forms out in space some where. But if they’re out there, why haven’t our space neighbors stopped by to say hello? This apparent contradiction is the basis of the Fermi Paradox.
Let’s stop for a moment to consider how many planets there are in the universe. The universe contains hundreds of billions of galaxies; there are hundreds of billions of solar systems in those galaxies and potentially dozens of planets in those solar systems. So conservatively there are 1 septillion planets for life to potentially be on. That’s 1 million billion… billion planets. That’s 1 with 24 zeros after it. That’s 1 trillion times 1 trillion. That is roughly equivalent to the number grains of sand on Earth.
By statistics alone there would logically have to be other life in the universe. If we said the odds of life on other planets is 1 in a trillion, then we’re saying there must be life on a trillion planets in the universe. So to say that “there is life on other planets is a safe bet” is an understatement. In fact it has to be true… well almost.
In 1950, physicist Enrico Fermi observed and questioned, if there are likely so many planets with extraterrestrial life, why haven’t any been observed. While the universe is indeed vast, it is also very old. Extraterrestrial life forms could have evolved, grown highly advanced over millions of years and already become extinct. At least one life form would have almost certainly emitted some sort of signal via radio wave, but we humans on earth haven’t heard anything remotely intelligent from space.
Great efforts have been made to resolve the Fermi Paradox empirically though observational techniques. Due to the size of the universe and the time it takes for matter to travel, searching for faster traveling, intelligently generated radio waves is the most probable way for humans to detect the presence of alien life. One of the largest, best known endeavors to find alien intelligence is Search for Extra-Terrestrial Intelligence’s SETI@home project whereby anyone can allow their home computer to be part of a computer cloud that analyzes radio transmissions from space. Other attempts to empirically resolve the Fermi Paradox include observing planets outside our solar system, searching for artifacts like probes within space and searching for massive intelligently designed infrastructure deep in space. Due to the size of the universe though, the search for physical objects is inherently limited by our technology.
For now, we are left with resolving the Fermi Paradox by strictly theoretical means. That is to say theories that explain the paradox but can not be proved and can not be disproved. Such theories include the religious views about the universe, various theories about how long we’ve been looking, the way we’ve been looking, the massive size of the universe and even the will (or lack there of) of extraterrestrials to make their presence known.
Until such time as the Fermi Paradox can be resolved by empirical observation, and we have definitive evidence that we’re not alone in the universe, it will truly remain one of astronomy’s great paradoxes. It’s a lovely paradox to ponder, perhaps only eclipsed by the thought of what it will mean for us as a planet when it is resolved, one way or another.
