Are We Alone In The Universe?
By Quamrul Haider
For millennia, we thought that our solar system was the only planetary system in the Universe. We even thought that it was home to the only planet in the cosmos where intelligent life evolved and is sustained due to a large number of happy coincidences.This viewpoint changed in the early 1990s, when astronomers began to discover planets orbiting stars other than our Sun. Since then, more than 3,600 such planets orbiting about 2,700 host stars have been discovered.
With a plethora of extra-solar planetary systems, it is quite natural to ask the question: How likely is it that there are other intelligent civilisations in the Universe? Our current knowledge of the Universe suggests that it is very unlikely that we are the only intelligent life in it. In fact, scientists believe that intelligent civilisations in our galaxy, the Milky Way, which is home to about 100 billion stars, are likely to number anywhere from ten thousand to one million. If indeed there are so many extra-solar planets with intelligent aliens, the question becomes: What is the best way to establish contact with them?
Astronomers prefer to scan the sky employing radio telescopes to eavesdrop on radio signals that an alien civilisation might broadcast. Radio signals emanating in narrow, focused bands could indicate the presence of intelligent life. Although radio signals decrease in intensity as they move out into the cosmos, they can propagate for few hundred light years and still carry enough information to connote the presence of intelligent life. They would eventually be drowned out by the background noise in the Milky Way.
The search focusses on the habitable zone of the nearby host stars, since signals from their inhabited planets would be strongest. The habitable zone is the area surrounding a star where it is neither too hot for life-giving liquid water to exist, nor too cold for the planet to be anything but a giant snowball.
Furthermore, astronomers concentrate on stars similar to the Sun, the only star known to support life. Moreover, they train their telescopes on the Lilliputs of our galaxy red dwarf stars. Their sheer number, at least 75 billion, statistically increases the probability that there might exist habitable planets orbiting some of them. They also live billions of years longer than Sun-like stars. Additionally, astronomers target globular clusters because, as the name suggests, they contain hundreds of thousands of stars, many formed 10 billion years ago.
The long life of the red dwarfs and the older stars in the clusters give the inhabitants of their planets enough time to not only bloom, but evolve into technologically advanced beings. After all, it took life on Earth about three billion years to develop from primitive to its present form.
The search started in earnest in 1984 with the establishment of SETI acronym for Search for Extraterrestrial Intelligence, located in Mountain View, California. Scientists at the SETI institute monitor signals from outer space, using ground-based radio telescopes in California, Hawaii, Puerto Rico and Chile.
They use space-based telescopes too, mostly the Hubble, Spitzer and Herschel telescopes, to look for signals being sent out with infrared pulses. Being more energetic than radio waves, these pulses will have little trouble cutting through the vast cosmic distances and penetrate our galaxys dusty medium without much attenuation, thereby extending the search to thousands rather than hundreds of light years away. A new state-of-the-art space-based telescope called The James Webb Space Telescope, scheduled to be launched in October 2018, will enable the SETI scientists to peer even deeper.
To date, SETI program has scanned about 20,000 objects, mostly Sun-like stars. Unfortunately, nothing interesting has been discovered so far. There have been some false alarms though, such as signals detected by the Russians from the star HD164595, about 95 light years away and a riot of faint signals from Barnards star, a mere six light years away. After careful analysis, it was determined that the signals were cosmic static, a disturbance in nature which manifests itself as radio waves arriving from the sky. Just last month, an interference from a distant satellite was believed to be a signal from a red dwarf 11 light years away.
The search got a boost earlier this year after NASA announced the discovery of seven rocky, Earth-sized planets orbiting Trappist-1, a red dwarf 40 light years away. Three of the planets seem to be within the stars habitable zone. In January 2016, astronomers discovered a planet even more suitable for life than Earth, orbiting the star Alpha Centauri B, sitting just 4.37 light years away.
We have sent out several emissaries, hoping to contact the smart aliens, wherever they are. One of the emissaries, Voyager 1, is carrying the Golden Record containing greetings for them in 55 different languages as well as images showing and explaining who we are. Launched in August 1977, the robotic spacecraft is still within the heliosphere -the Suns domain.
We are also leaking signals into space - primarily radio, television and radar - albeit unintentionally for more than 50 years. Spreading outward at the speed of light, by now, they have crossed the paths of approximately 1000 stars in a 50 light year radius.
It is quite likely that aliens may very well be out there looking for us too. If so, our best chance of finding one another is to presume that their ability to see across the chasm of space is effectively the same as our own.
Scientists believe that contact with intelligent aliens wont be an Archimedes-type eureka moment. Instead, it would likely be a prolonged, step-by-step process that would take a very long time, perhaps decades. Until then, we are alone, at least in our galactic neighbourhood, if not in the Universe.
The writer is a Professor of Physics at Fordham University, New York.
Photos: Google Images.
