To my mind, one of the coolest things that a basic understanding of science allows you to do is stare up at the night sky and imagine that somewhere in that mess of twinkling dots is another life form doing exactly the same thing. However, even mentioning the idea of aliens is enough to make a portion of people snicker and roll their eyes, but when you consider the probabilities at work in the universe the odds are on the side of believers.
One of the key pieces of the argument for the existence of aliens has long been the fabled Drake Equation created by astronomer Francis Drake in 1961 to help encourage investment in SETI (the Search for Extra Terrestrial Intelligence). The drake equation basically takes the huge number of planets and stars that we think exist and whittles it down to a conservative estimate of the number of alien civilizations. It takes into account six variables: the rate of star formation in the galaxy you are looking at, the fraction of stars that form planets, the number of planets that could support life, the probability that life actually emerges on one of these planets, the probability that intelligent life evolves, the probability that one of these civilizations develops a way to communicate with us and finally the length of time that a civilization like that is likely to exist.
Basically it is a lot of multiplying down that gives an estimate that there are around 12,000 civilizations capable of communication that should exist in our galaxy alone. So how can we find them?
The answer might lie in a combination of the laws of thermodynamics and something called the Kardashev Scale. The latter describes three types of civilizations that can exist at advancing levels of awesomeness. Civilizations are defined by the amount of energy they use and include:
- Type I – Similar to Earth now. Some people have argued that Type I civilizations should be able to make use of all the energy produced by its planet (geothermal, wind, tidal energy, etc.). Based on that definition, humans have a Type 0.7 civilization, possibly reaching 1.0 in the next few centuries.
- Type II – Civilizations that can use all the energy produced by the star(s) at the heart of their solar system.
- Type III – Civilizations that can use all the energy produced by their galaxy.
While it may be fun to imagine what life would be like at each level, all we really need to focus on right now is that each level uses an insane amount of energy compared to the level before it. The thing about energy is that is produces heat, and heat is something that we can see from very far away.
With that in mind, a group of scientists recently set out the find advanced societies across a section of the universe. Researchers at Penn State recently surveyed 100,000 galaxies using NASA's Wide-Field Infrared Survey Explorer (WISE) – a very fancy telescope. They looked at the heat signature from each galaxy and compared it to what you would expect if only natural processes were at work. The idea was that if a galaxy is hotter than you expect it to be, it might be because a civilization there is consuming a lot of energy. What they found was kind of scary…
Out of 100,000 galaxies, 50 where in the “hotter than expected” group. That is a very, very low number. Low enough that when they look at those 50 more closely, they could quickly become zero. If each of those galaxies is supposed to have 10,000ish advanced civilizations according to the Drake Equation, why are things so chilly? Either we aren’t looking at things in the right way or there might not be as much company out there as we thought. Maybe it’s just me, but that is a lonely thought.