“Where is everybody?” wondered Enrico Fermi in 1950, trying to understand why we haven’t found life beyond Earth. The probabilities suggest that life may have arisen elsewhere, but we have yet to find evidence of life outside our own planet. Perhaps we are simply impatient, and if we wait for a few hundred or thousand years, someone might come to visit us.
Intelligent life developed on Earth, but we are not the only planet in the universe. The galaxy contains up to one trillion such planets, and there are up to two trillion galaxies in the universe. Most planets are unsuitable for life (many are too hot, too cold, lack an atmosphere, or are composed only of gases), but in a universe that is homogeneous, Earth’s “special” conditions should not be unique. If life emerged here, it should have emerged elsewhere as well.
There, “elsewhere,” life should have begun to build and explore around it. Even if most intelligent civilizations fail in their efforts (or simply move on to other things), the fact that our galaxy has existed for over 10 billion years means that at least one civilization should have already visited our solar system, or at least left some sign of its existence.
And yet, we haven’t seen anything. We have absolutely no evidence of any extraterrestrial civilization, let alone life. This is the great Fermi Paradox: If life can occur, it should be common, and if it is common, we should already know about it. But we do not.
Over the decades, astronomers have proposed many solutions to this mystery. The Rare Earth Hypothesis suggests that life is so rare that we might be among the first beings to appear in the Galaxy. Another hypothesis is the “Great Filter” theory, which argues that while life may be common, intelligent life is difficult to develop, and this is why we have not made contact. Or perhaps we are simply uninteresting and not worth visiting?
Amri Wandel at the Hebrew University of Jerusalem proposes a new explanation (Wandel, 2022). Our galaxy may have existed for billions of years and there may be many galaxies, but humans have only recently begun this exploration of the outside world, in the last century, with space exploration and technological advancement. Perhaps we just need to wait a little longer?
In his article, Wandel argues that civilizations (both extraterrestrial and terrestrial) calculate the probabilities of whether similar civilizations exist and the chances of their signals reaching us, depending on the speed at which they travel. Furthermore, extraterrestrials, like us, face practical problems such as energy collection and information processing, despite their advanced technological capabilities.
Assuming we are similar and that there is a vast number of habitable planets in the galaxy, it is unlikely that they could send active probes to all of them. Another hypothesis is that they might have constructed listening stations and are waiting to receive signals from other civilizations, similar to the radio signals we have been emitting for less than a century—a very short time relative to the age of the universe!
If this is indeed the case, due to the short duration of our transmissions, our “radio bubble” is less than 200 light-years in diameter, compared to the 100,000 light-years of the galaxy. This means that it might take hundreds or even thousands of years for our signals to reach an extraterrestrial civilization, and even longer to receive a response or detect a probe from them. Perhaps, therefore, we are not alone after all, and our galaxy might host many other advanced civilizations. They simply haven’t responded to our call—yet!
The article is based on Wandel’s publication https://arxiv.org/abs/2211.16505 as well as the popular article https://www.space.com/fermi-paradox-aliens-contact-earth-not-interesting
or are they already at Patissia?