Hundreds of millions of galaxies move through the visible universe, with billions of stars in each, with an average of several planets orbiting each. Even if a trillion planets in each galaxy are not habitable, countless moons orbiting these lifeless worlds could be.
But again, despite these numbers, humans have yet to detect signals from intelligent aliens. The prophetic question of physicist Enrico Fermi from 1950, “Where is everyone?” is still unanswered.
It is too early to expect results
A new study claims that humanity has just scratched the surface of the universe, and therefore there is no reason for cynicism. According to this research, all previous searches for extraterrestrial life (SETI) hardly form a pool of water within all the world's oceans that represent space.
“We haven’t even started looking right yet,” said Shubham Kanodia, an astronomy student and co-author of the study, which concludes that somewhere in that cosmic ocean, within our galaxy, intelligent aliens may be just saying “hello, here we are”. But we just cannot know that, at least not yet.
Over the past 60 years, numerous SETI projects have sought and still seek alien signals. Some scan large parts of the sky in search of strong signals, while others target individual star systems in search of weaker systems. But except for a few anomalies that never happened again (like the discovery of the ‘Wow!’ Signal in 1977), these searches have so far remained without results.
How close are we?
FrancoisMalan / flickr.com
Kanodia and his colleagues at Penn State University wanted to know exactly how much figurative ‘haystack’ they covered in search of the alien ‘needle’. Researchers agree with renowned SETI astronomer Jill Tarter, who back in 2010 said it was simply ridiculous to conclude that intelligent aliens do not exist because we have not yet discovered their messages. Even if such signals exist and are directed towards the Earth, we have scanned such a small part of the sky, and in addition we may not even be looking for the right type of signal, or long enough, to find it.
“Let’s tell you that something totally interesting is just taking place in Houston” Canodio said during his speech at NASA. "I'm not telling you exactly where it is. I am not telling you what time it is. I am not telling you what it is. Is he in the bookstore? Is it a music concert? I am not giving you absolutely any additional information. It would be really hard to try to find it.”.
"Houston, we have a problem," he added. "We don't know what we're looking for at all, or where we should start looking".
In their study, Kanodia and his colleagues built a mathematical model that they considered to be a cosmic haystack of reasonable size. Their haystack is a sphere almost 33,000 light-years in diameter, with the Earth at its center. This area encompasses the core of the Milky Way, as well as numerous giant clusters of stars above and below our galaxy.
In addition, they selected eight dimensions for the search for aliens, factors such as signal frequency, bandwidth, power, location, repetition, polarization, and modulation (complexity), and defined reasonable limits for each. “This results in an 8D layer with a volume of 6.4 × 10 ^ 116 m ^ 5 Hz ^ 2 s / W,” the authors wrote. That is 6.4 with 115 zeros, or a space of truly giant proportions.
How much of that layer have we searched so far?
SETI radio telescopes explore the sky in search of intelligent life. Kanodia and his colleagues then researched SETI projects carried out over the last 60 years and compared them to past. The scientists then determined that the collective search of humanity for aliens covered about 0.000000000000000058% of the volume of the layer. “It’s like a tub of water in all the oceans of the world,” Kanodia said. Or like a piece of land five by five inches in relation to the entire surface of the Earth.
These figures make humanity’s attempts so far weak and ineffective, but Kanodia sees this as an opportunity, especially as modern telescopes are getting better at scanning more and more objects with greater sensitivity and speed. For example, he said, a 150-minute search through the Murchison Widefield network covered a higher percentage of ‘haystack’ than any other SETI project in history.
“That is the purpose of this layer… to help better informed future search strategies,” Kanodia said. He added that his team's calculations assumed that there was only one extraterrestrial civilization within Earth's range, not more. But maybe there are more nearby.
“By ocean analogy, we don’t have to drain the entire ocean to find fish,” he said. "By analogy with Houston, if there were two interesting events, you shouldn't ask for so much."
40% chance we are alone in the galaxy
rick shide / flickr.com
But on the other hand, there is no guarantee that a figurative fish, needle, or interesting event exists at all.
Another group of scientists, from Oxford University, recently decided on a different approach to the issue of aliens. Instead of concentrating on the probability of finding ‘techno-signatures’ that could be detected, they explored the probability that intelligent life exists at all.
Oxford scientists have researched dozens of studies on variables in Drake’s famous equation, which calculates the probability of the existence of an extraterrestrial civilization. They analyzed the results and came to the not-so-popular conclusion that there is a 2 in 5 chance that humans are completely alone in the Milky Way.