Since mankind first gazed up at the stars, we have wondered if we are alone in the universe. We have yet to find any definitive proof that other life exists on other planets. However, every indicator in physics and astronomy points to the existence of other life as not only likely, but almost with certainty. There are about 400 billion stars in the Milky Way alone and about 170 billion galaxies in the observable universe. Most physicists also agree that the entire universe has the same periodic table of elements and laws of physics. Therefore, it would be shocking if there were not other life forms out there. Even more likely, other life might be completely different from life-as-we-know-it and thrive in different environments. We could find strange forms of life anywhere from the clouds of gas giants like Jupiter to the cold vacuum of space to the bottom of oceans hundreds of miles deep under crushing pressure. Life is most likely diverse and plentiful in the universe.
A more interesting question than “is there other life out there” is whether or not there’s other intelligent life in the universe. Dr. Frank Drake was an astronomer and astrophysicist who wondered whether or not other civilizations existed in the cosmos. In 1961, he created an equation to determine this potential scenario. The Drake Equation is a series of variables designed to determine how many other civilizations in the universe with whom we can communicate at any given time. The equation employs such factors as the number of stars formed in the galaxy per year, the fraction of planets that develop a civilization, and the length of time any civilization would be able to communicate with us. Unfortunately, most factors in the equation are unknown, leading to estimates ranging from tens of millions to infinitesimal fractions. As useful as the Drake Equation might be some day, we simply do not know enough of the various inputs needed to make any reasonable estimates.
Of particular note is the last factor in the Drake Equation: the length of time a civilization is able to communicate with us. This is usually interpreted as the length of time before a civilization is destroyed (for example, in a nuclear war, climate change, or an asteroid impact). However, it could also mean that after a certain period of time, a civilization will develop a method of communication that we cannot yet comprehend. This brings me to the other major measurement of civilizations: the Kardashev Scale. According to this scale, there are multiple types of civilizations, based on the amount of energy they consume. A Type I civilization consumes the energy of a planet. A Type II civilization consumes the energy of a star. Finally a Type III civilization consumes the energy of an entire galaxy. There is some dispute over the validity of the Kardashev Scale, mostly due to whether or not more advanced civilizations will even need a lot of energy, so I will refer to the three types based on how widespread the civilization becomes. For example, a Type II civilization will have dominion over one or more star systems and a Type III civilization will have dominion over entire galaxies. Given these sample civilizations, where do we stand? As of now, we are at Type 0. We do not consume
all of the energy of the Earth, nor do we have complete dominion over the planet. We are probably around a Type 0.75.
If there were an imaginary line, charting the stages of life (as we know it), bacteria and other primitive single-cell organisms would be on one end and Type III (and beyond) civilizations would be on the other end. With this scale in mind, are we still unique? To answer this, we must figure out how much time life spends at each part of the scale. On Earth, single-cell life forms have existed for far longer than any complex life, about 3.6 billion years. Since primitive life has been around the longest, it is logically the most common form of life (as we know it) in the universe. However, once a civilization advances to Type III and beyond, it would be essentially immortal. Therefore, advanced civilizations, while most likely few in number, would be almost as widespread as primitive life and last even longer. The two extremes of the scale, primitive life and advanced civilizations, would therefore be the most common forms of life in the universe.
In concluding, between widespread primitive life and galactic civilizations, would humanity still be unique? No, but we would most likely be rare. Today, we are inching ever closer to becoming a Type I civilization. We have only been at Type 0 for about 10,000 years. This window of time is so tiny in the grand scheme of the cosmos, primitive civilizations like ours are probably one of the scarcest occurrences in the universe. Life spends so much time either at one extreme or the other, that humanity in its current state goes by in a blink. While we may not be unique, our collective egos can take solace in the probability that we are one of the oddest sights in the universe, at least until we become advanced enough to venture into deep space.