Where are they? Where is everybody? Where are all the aliens? Are we alone?

Back in 1950, Sir Enrico Fermi was taking a lunch break away from making nuclear bombs at Los Alamos National Laboratory, when he posited a question to his lunch companions:

Where are they? Where is everybody? Where are all the aliens? Are we alone? Or could we be really alone?

Considering the age of the universe, and the mind-boggling number of planets that could possibly sustain life — shouldn’t by now the universe be teeming with life, much of it intelligent, and some significant portion of that able to travel amongst the stars? And if you take all these things for granted (which it makes sense to), we should’ve been visited by this intelligent life time and time again by now. And yet we only have anything approaching definitive evidence that we’re alone in the universe.

This observation became known as the Fermi Paradox. And ever since 1950, people have sought to explain it. And since then, numerous papers are published, hypotheses are written and debated around the globe as a fitting answer to the fermi paradox.

The Fermi paradox is the apparent contradiction between the lack of evidence for extraterrestrial civilizations and various high estimates for their probability

In 1960, Arthur C. Clarke, author of “2001: A Space Odyssey”, once said: “Two possibilities exist: Either we are alone in the universe, or we are not. Both are equally terrifying.”

So why don’t we see life out there in the cosmos? It’s a puzzle really. And by every passing year, the lack of evidence for any alien activity gets more puzzling because we should see them, shouldn’t we?

The universe is 13.8 billion years old. So in a matter of scale, if we represent the age of the universe by one year, then our species came into existence about 12 minutes. Civilization has existed for a few seconds.

Extraterrestrial civilizations could have started in a few months. A civilization developing a level of technology more advanced than ours could program self-replicating probes to visit every planetary system in the galaxy. And they could/should have colonized the galaxy by now. Since many of the stars similar to the Sun are billions of years older, the Earth should have already been visited by extraterrestrial civilizations, or at least their probes.

But it doesn’t seem to be the case. Extraterrestial life should have engaged in some recognizable activity although an advanced life would be indistinguishable from magic, it would still be visible in some form or another. Maybe a Dyson sphere? Or maybe sending out signals towards the universe saying “We. Are. Here”

So where is everybody?

It’s a puzzle because we do expect these civilizations to exist, don’t we?
After all, there could be a trillion planets in the galaxy maybe more. We know that there are up to 500 billion planets in the Milky Way, at least 10 billion Earth-like planets. Many have been around billions of years longer than Earth. But we’re observing zero galactic civilizations.

We should be able to see something……but there’s nothing. When we look and search in space, it seems to be empty and dead.

This means something is preventing living things from climbing the staircase,
beyond the step we’re on right now. Something that makes becoming a galactic civilization extremely hard, maybe impossible.

This is the Great Filter.

The Great Filter

Habitability — A planet that exists in the habitable zone of the star. Too near and it can burn everything on it and too far, everything will freeze to death. A planet where water can exist. (Goldilocks Zone)
Abiogenesis — The creation of life from nonlife. A.K.A Dead Chemistry, that needs to assemble itself to give birth to life. (The simple building blocks). Water, acids, nutrients, etc. A gradual process of increasing complexity of the first self-replicating molecules by a randomly occurring chemical process.
The development of technological civilization- From apes to humans using and creating technology. It took us 200 thousand years to evolve from hunter-gathers to the current civilization.
Communication across space — Maybe advanced civilizations choose to explore inner space rather than outer space, or engineer at small distances rather than large. Maybe they just don’t want to risk an encounter with a potentially more advanced and hostile neighbor. Maybe they choose to stay silent or don’t spend long trying to communicate.
The universe being hostile — The universe in the past was way more hostile and only recently things have cooled off for life to give a chance and enable it.
Good weather — Although it seems nonessential, the weather is one of the most important part of survival. But long-term climate stability is strange, if only because astronomical influences can push a planet towards freezing or frying. There’s a hint our moon has helped, and that’s interesting because the prevailing theory is that the moon came into being when Theia, a body the size of Mars, crashed into a newly formed Earth. Since the moon is of the perfect size we exist. If it didn’t, the earth would have a dangling axis and we would not be able to exist due to constant temperature changes.

Stephen Webb gave an illustration of more barriers for Eg: A one-in-a-thousand chance of making it across each of the barriers. Some chances might be one in a million.

If the galaxy contains a trillion planets, how many will host a civilization capable of contemplating like us?

Right sort of planet around the right sort of star — the trillion becomes a billion.
A climate that stays benign for eons — the billion becomes a million.
Life must start — the million becomes a thousand.
Complex life forms must arise — the thousand becomes one.
Sophisticated tool use must develop — that’s one planet in a thousand galaxies.
To develop the techniques of science and mathematics — that’s one planet in a million galaxies.
To reach the stars, they’ll have to be social creatures, capable of discussing abstract concepts with each other using complex grammar- one planet in a billion galaxies.
And they have to avoid disaster — not just self-inflicted but from the skies, too. One planet in a trillion galaxies.

The Filter ahead of us:

A lot of scientists believe that we might be all alone. A depressing hypothesis but plausible that once a species takes control over its planet, it’s already on the path to self-destruction. The greatest and harder filter is still yet to come. Nuclear war. Global warming. Nanotechnology. Genetic Engineering. Hostile AI etc. which extinguishes us from the planet and it’s just about a matter of time till we vanish.

Technology is a good way to achieve that. It needs to be something that’s so obvious, that virtually everybody discovers it, and so dangerous, that its discovery leads almost universally to an existential disaster.