Is E.T. Out There?

In the 1982 movie E. T. the Extra-Terrestrial, a friendly alien gets stranded on Earth and is saved by kids who befriend him and help him phone home. Is there really intelligent life in the universe outside of Earth? Many people think so. In fact, many people think aliens have visited Earth and some even think they are still here. I have a hard time believing any of the alien visit stories. These stories are always short on any real proof and long on people insisting they are telling the truth. For me, extraordinary claims require extraordinary evidence. I haven’t heard or seen any credible evidence regarding alien visits.

Is there intelligent life in the universe outside of Earth? Given the size of the universe it seems to me that it is very likely. Astronomers tell us there are 300 to 400 billion stars in our Milky Way Galaxy. Some galaxies are much larger than our galaxy containing many more stars. Astronomers also tell us there are likely 200 billion galaxies in the universe, maybe as many as 500 billion. So there are a whole lot of stars out there that might have planets that could support life. That certainly isn’t proof but if the universe is so big could we be the only intelligent life in it?

Distances within our galaxy are enormous and distances to other galaxies are incredibly larger. Certainly too far for any mode of travel that we currently have or can even reasonably imagine. If they exist, can we communicate with these other intelligent civilizations? It likely makes sense to only consider the possibility of communication within the Milky Way Galaxy as other galaxies are just too far away.

How can you estimate the number of intelligent civilizations in our galaxy? Well, a man named Frank Drake, a renowned radio astronomer, with the help of other scientists, put together a formula over 50 years ago to try to estimate that number. It has come to be known as the Drake Equation. Drake not only wanted to estimate the number of intelligent civilizations but also wanted to estimate how many could be detected from Earth through radio astronomy.  Earth has been emitting detectable signals since the 1940s when we started transmitting television signals worldwide through radio waves. We have also on rare occasions deliberately sent signals from Earth hoping to reach other civilizations telling them that we exist. Other civilizations might be doing the same thing.

The Drake Equation is as follows is

N = R* • fp • ne • fl • fi • fc • L

N           is the number of civilizations in the Milky Way Galaxy whose electromagnetic emissions could be detectable

R*         is the rate of formation of stars suitable for the development of intelligent life

fp          is the fraction of those stars with planetary systems

ne         is the number of planets, per solar system, with an environment suitable for life

fl            is the fraction of suitable planets on which life actually appears

fi            is the fraction of life bearing planets on which intelligent life emerges

fc           is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space

L            is the length of time such civilizations release detectable signals into space

Estimating each of these numbers is a bit subjective and pretty much one estimate is as reasonable as another. The original estimate made by Drake and his colleagues of N was between 1,000 and 100,000,000. More current and conservative estimates range from 127 to 245. We know the answer is at least one because Earth fits the definition, although some might argue that civilization on Earth is not all that intelligent.

Each of the numbers are interesting in their own way but L is a bit scary. The length of time such civilizations release detectable signals into space can mean that the civilizations become more efficient and don’t emit detectable signals unless they want to do so. Or it might mean that the civilizations destroy themselves in some way, such as nuclear destruction or pollution of their planet. Things that we are struggling with today.

So if there are other intelligent beings out there should we try to communicate with them? Some would say no as the extraterrestrials might be dangerous. Personally I don’t think there is much danger but no one knows for sure.

Are they trying to communicate with us? An organization called SETI (Search for Extraterrestrial Intelligence) is listening for such signals. No luck yet but maybe someday ET will phone us.

Drake Equation

http://www.seti.org/drakeequation

http://www.space.com/25219-drake-equation.html

http://en.wikipedia.org/wiki/Drake_equation

http://www.cosmosmagazine.com/features/are-we-alone-a-review-drake-equation/

SETI – Search for Extraterrestrial Intelligence

http://www.seti.org/

Contact, a novel by Carl Sagan written in 1985 (also made into a movie in 1997)

http://en.wikipedia.org/wiki/Contact_%28novel%29

Stephen Hawking – Aliens May Pose Risks to Earth

http://www.nbcnews.com/id/36769422/ns/technology_and_science-space/t/hawking-aliens-may-pose-risks-earth/#.U0qAcleXZEM