Over the last few decades, humans have been employing various means to detect aliens. From trying to send radio signals to developing highly sensitive telescopes, we have been tirelessly working to find a space neighbor – and there just seems to be none. In a universe that is 90,000,000,000 light years wide (and rapidly expanding), could we be alone? Where are all the extraterrestrial life? This question is answered – or rather, addressed – in a popular puzzle: The Fermi Paradox.
Our universe, as far as we know it, is home to a 100 billion galaxies. These in turn house about 100 billion to 1000 billion stars. And these stars together have around 10 to the power of 24 planets. Our home galaxy, the Milky Way, has a hundred billion planets. Moreover, the Milky Way is roughly 13 billion years old. Subtly speaking, the probability of us encountering extraterrestrial species is enormous. This raises a troubling question: where is all the alien life?
One fine day in 1950, physicist Enrico Fermi asked the very same question to his colleagues over lunch. Today, this famous question is known as the Fermi Paradox or the Great Silence. Since then, endless theories have been contrived to explain why we have not detected any sign of extraterrestrial life. Many of these theories are perfectly conceivable, and some of these can be eerily dark.
THE KARDASHEV SCALE
In 1964, a Russian astrophysicist, Nikolai Kardashev came up with a civilization scale now known as the Kardashev scale. The physicist had been scouring for extraterrestrial life when he came up with this. The Kardashev scale measures a civilization’s level of technological advancement. Initially, the scale had 3 levels – type I, II and III, which has now been extended to types IV and V.
A Type-I civilization is one which can utilize all the energy on its planet. Scientists believe that the human race will reach this level of advancement in another 100 to 200 years when our energy production is around 100,000 times greater than the production today. A Type-II civilization can utilize the power of its home star by controlling it. A hypothesis has it that such civilizations will build a megastructure called the Dyson Sphere around their star, to harness all of its energy. A Type-III civilization will be one that can utilize all the energy of its galaxy, making this type of civilization close to supernatural.
Evidently, the human civilization on this scale is in its primitive stage. If there were at least one advanced alien civilization, we should have come across them by now. However, there is a possible explanation that we are not sophisticated enough to recognize their signals yet. Another explanation would be that the emergence of intelligent life is far rarer than we think.
THE GREAT FILTER
This theory puts forward that there might be something that stops civilizations from attaining the aforementioned advanced levels. These “somethings”, called filters, might be events or situations that destroy the civilizations before they reach technologically advanced levels of interstellar travel or communication. Either this or the civilizations destroy themselves at some point of time. Both of these are particularly unnerving.
Scientists behind this theory believe that once a civilization has come into being, its destruction is inevitable.
Quite a number of scientists believe that climate change could be the Great Filter for the human civilization. However, there are other theories to the paradox that give us a non-apocalyptic ending.
Another credible reason to missing extraterrestrial life is that we do not pick up the signals that they send us. We could be operating in an entirely different frequency zone, while our alien mates are trying to convey their message in another frequency altogether. This demands more sensitive detection instruments than the ones we already have.
Moreover, given all the dust, planets and stars, the signals we send out or the signals that other intelligent life send out could get easily lost in the depths of space. Hence, SETI (Search for Extraterrestrial Intelligence) is concentrating on limiting its frequency ranges and aims at a certain region of space to transmit signals, since doing so will increase their transmission distance to more than a hundred light years.
According to a theory, any extraterrestrial civilization with insufficient amounts of carbon cannot become technologically advanced. As a result of not having enough amounts of energy, the civilization would not be able to send out any radio signals, and we would not be able to detect it. This theory is built on the basis that a necessary condition for the development of a civilization is adequate amounts of carbon to give thermal energy from combustion.
In 2017, scientists laid out another hypothesis which says that aliens might be hibernating or aestivating. The theory states that aliens might be hibernating till the surrounding environment cools down. The laws of thermodynamics place a rule that computational technologies have to be cool enough for them to function. This is observed in real life, with quantum computers and supercomputers being operated at near 0 Kelvin temperatures. Thus, it is quite possible that aliens are maintaining torpor till the universe naturally cools down, to build super civilizations after the conditions become optimal.
WE HAVE TO WAIT LONGER
Our first search for intelligent life began only in 1937. That means we have given ourselves too little time to conclude their existence. In the timescale of the universe’s age, we have been searching only for seconds. Moreover, we have been able to touch only less than 1% of our own galaxy. It is safe to say that we have to wait for thousands of years before we detect any form of alien life. That will give us enough time to extend our space exploration to deeper regions of our galaxy, and evolve better means to detect alien signals.
Science is known for its occult nature – for there are more unknowns than knowns. There are many mysteries yet to unravel as we move forward, and we got to be patient whilst we keep wondering.