100,000 Galaxies. Each one contains Billions upon Billions of stars. Each star could have planets, leading to countless possibilities of variation and the potential for life. But would we see the signs of civilization from Earth? Could a highly advanced civilization control the entire population of stars in their galaxy and harness that energy for their industry? Would they alter their stellar environment enough that we could see them?
This is exactly the line of questioning that led astronomers to look at over 100,000 different nearby galaxies in mid-infrared emission to see some potential signs of Alien life. In these particular wavelengths, nothing interesting was found. But does this mean that the Universe is devoid of intelligent life? Possibly. But with our lack of technology and ability to look closely, its as if we are in space and looking for signs of ants on Earth. We have no evidence for what the by-products of these civilizations are, and if we did we couldn’t look closely enough to see them. The idea of looking at mid-infrared wavelengths comes from Physicist Freeman Dyson in the 1960s, taking simple thermodynamics and suggesting that any civilization using a vast amount of energy will produce heat as a by-product that could be seen at mid-infrared.
But there is a lot to consider. Will such advanced civilizations lose energy to heat? Or will they be so efficient as to use energy without unsettling their environment? Do they even exist? If they do, and if others do, are they part of Universal pact to not show signs or disturb the evolution of other civilizations such as humanity? The possibility leads to so many amazing questions that we have no way of answering.
How do we classify ‘civilizations’ when talking about alien life? We generally fit them into categories based on how much energy they can harness and use, what we call the Kardashev Scale:
Type I – This is what humanity is. We harness the energy of the Sun that strikes our planet (almost)
Type II – A civilization that can harness the entire energy output of their home star
Type III – A civilization with the energy output and use of their entire Galaxy’s worth of stars
As you can see, there are pretty huge leaps between the three classes. We don’t even know if type II and III civilizations could exist, because of another idea called the Fermi Paradox. The idea was put forth by famous physicist Enrico Fermi. He figured that with the number of stars much older than our own, the amount of time available to develop interstellar travel, and the vast amount of time with which to colonize a galaxy, if an extraterrestrial civilization existed at this level is would have found the Earth and colonized it, and we would have already seen evidence of their existence. So if we can’t find any evidence, there much be no intelligent civilizations. There are a lot of different ways to interpret this, and a lot of different outcomes because we have little data to constrain it.
One of the interesting ideas that derives from the Fermi paradox is the idea of the great filter. Any intelligent civilization that reaches a certain point inevitably is destroyed by themselves, an act of nature (such as a large asteroid impact), or some other unforeseen action. If humanity has not yet reached the great filter, it’s possible that no civilization can pass it and we will inevitably be destroyed. If humanity is past the great filter than maybe many civilizations have passed it as well. If humanity is the first civilization to pass the great filter than we can continue to grow unbounded.
The Universe is indeed a great experiment, and I find it difficult to think that humanity is the first to evolve what we call intelligence, especially with so many possibilities. It may simply be that interstellar travel is impossible on any reasonable time scale, and the intelligent civilizations of the Universe are stuck where they are. I don’t know, but I hope we can narrow down the answers to some of these questions before the end of my life, or at least before the end of the human species.