Tag Archives: Fermi

Where Are They?

Astrophysics professor Adam Frank reminds us to ponder Enrico Fermi‘s insightful question posed in the middle of the last century. Fermi’s question spawned his infamous, eponymous paradox, and goes something like this:

Why is there no evidence of extraterrestrial civilizations in our Milky Way galaxy given the age of the universe and vast number of stars within it?

Based on simple assumptions and family accurate estimates of the universe’s age, the number of galaxies and stars within it, the probability of Earth-like planets and the development of intelligent life on these planets it should be highly likely that some civilizations have already developed the capability for interstellar travel. In fact, even a slow pace of intra-galactic travel should have led to the colonization of our entire galaxy within just a few tens of millions of years, which is a blink of an eye on a cosmological timescale. Yet we see now evidence on Earth or anywhere beyond. And therein lies the conundrum.

The doomsayers might have us believe that extraterrestrial civilizations have indeed developed numerous times throughout our galaxy. But, none have made the crucial leap beyond ecological catastrophe and technological self-destruction before being able to shirk the bonds of their home planet. Do we have the power to avoid the same fate? I hope so.

From 13.7:

The story begins like this: In 1950, a group of high-powered physicists were lunching together near the Los Alamos National Laboratory.

Among those in attendance were Edward Teller (father of the nuclear bomb) and the Nobel Prize-winning Enrico Fermi. The discussion turned to a spate of recent UFO sightings and, then, on to the possibility of seeing an object (made by aliens) move faster than light. The conversation eventually turned to other topics when, out the blue, Fermi suddenly asked: “Where is everybody?”

While he’d startled his colleagues, they all quickly understood what he was referring to: Where are all the aliens?

What Fermi realized in his burst of insight was simple: If the universe was teeming with intelligent technological civilizations, why hadn’t they already made it to Earth? Indeed, why hadn’t they made it everywhere?

This question, known as “Fermi’s paradox,” is now a staple of astrobiological/SETI thinking. And while it might seem pretty abstract and inconsequential to our day-to-day existence, within Fermi’s paradox there lies a terrible possibility that haunts the fate of humanity.

Enough issues are packed into Fermi’s paradox for more than one post and — since Caleb Scharf and I are just starting a research project related to the question — I am sure to return to it. Today, however, I just want to unpack the basics of Fermi’s paradox and its consequences.

The most important thing to understand about Fermi’s paradox is that you don’t need faster-than-light travel, a warp drive or other exotic technology to take it seriously. Even if a technological civilization built ships that reached only a fraction of the speed of light, we might still expect all the stars (and the planets) to be “colonized.”

For example, let’s imagine that just one high-tech alien species emerges and starts sending ships out at one-hundredth of the speed of light. With that technology, they’d cross the typical distance between stars in “just” a few centuries to a millennium. If, once they got to a new solar system, they began using its resources to build more ships, then we can imagine how a wave of colonization begins propagating across the galaxy.

But how long does it take this colonization wave to spread?

Remarkably, it would only take a fraction of our galaxy’s lifetime before all the stars are inhabited. Depending on what you assume, the propagating wave of colonization could make it from one end of our Milky Way to the other in just 10 million years. While that might seem very long to you, it’s really just a blink of the eye to the 10-billion-year-old Milky Way (in other words, the colonization wave crosses in 0.001 times the age of the galaxy). That means if an alien civilization began at some random moment in the Milky Way’s history, odds are it has had time to colonize the entire galaxy.

You can choose your favorite sci-fi trope for what’s going on with these alien “slow ships.” Maybe they use cryogenic suspension. Maybe they’re using generation ships — mobile worlds whose inhabitants live out entire lives during the millennia-long crossing. Maybe the aliens don’t go themselves but send fully autonomous machines. Whatever scenario you choose, simple calculations, like the one above, tend to imply the aliens should be here already.

Of course, you can also come up with lots of resolutions to Fermi’s paradox. Maybe the aliens don’t want to colonize other worlds. Maybe none of the technologies for the ships described above really work. Maybe, maybe, maybe. We can take up some of those solutions in later 13.7 posts.

For today, however, let’s just consider the one answer that really matters for us, the existential one that is very, very freaky indeed: The aliens aren’t here because they don’t exist. We are the only sentient, technological species that exists in the entire galaxy.

It’s hard to overstate how profound this conclusion would be.

The consequences cut both ways. On the one hand, it’s possible that no other species has ever reached our state of development. Our galaxy with its 300 billion stars — meaning 300 billion chances for self-consciousness — has never awakened anywhere else. We would be the only ones looking into the night sky and asking questions. How impossibly lonely that would be.

Read the entire article here.


So Where Is Everybody?

Astrobiologist Caleb Scharf brings us up to date on Fermi’s Paradox — which asks why, given that our galaxy is so old, haven’t other sentient intergalactic travelers found us. The answer may come from a video game.

[div class=attrib]From Scientific American:[end-div]

Right now, all across the planet, millions of people are engaged in a struggle with enormous implications for the very nature of life itself. Making sophisticated tactical decisions and wrestling with chilling and complex moral puzzles, they are quite literally deciding the fate of our existence.

Or at least they are pretending to.

The video game Mass Effect has now reached its third and final installment; a huge planet-destroying, species-wrecking, epic finale to a story that takes humanity from its tentative steps into interstellar space to a critical role in a galactic, and even intergalactic saga. It’s awfully good, even without all the fantastic visual design or gameplay, at the heart is a rip-roaring plot and countless backstories that tie the experience into one of the most carefully and completely imagined sci-fi universes out there.

As a scientist, and someone who will sheepishly admit to a love of videogames (from countless hours spent as a teenager coding my own rather inferior efforts, to an occasional consumer’s dip into the lushness of what a multi-billion dollar industry can produce), the Mass Effect series is fascinating for a number of reasons. The first of which is the relentless attention to plausible background detail. Take for example the task of finding mineral resources in Mass Effect 2. Flying your ship to different star systems presents you with a bird’s eye view of the planets, each of which has a fleshed out description – be it inhabited, or more often, uninhabitable. These have been torn from the annals of the real exoplanets, gussied up a little, but still recognizable. There are hot Jupiters, and icy Neptune-like worlds. There are gassy planets, rocky planets, and watery planets of great diversity in age, history and elemental composition. It’s a surprisingly good representation of what we now think is really out there.

But the biggest idea, the biggest piece of fiction-meets-genuine-scientific-hypothesis is the overarching story of Mass Effect. It directly addresses one of the great questions of astrobiology – is there intelligent life elsewhere in our galaxy, and if so, why haven’t we intersected with it yet? The first serious thinking about this problem seems to have arisen during a lunchtime chat in the 1940?s where the famous physicist Enrico Fermi (for whom the fundamental particle type ‘fermion’ is named) is supposed to have asked “Where is Everybody?” The essence of the Fermi Paradox is that since our galaxy is very old, perhaps 10 billion years old, unless intelligent life is almost impossibly rare it will have arisen ages before we came along. Such life will have had time to essentially span the Milky Way, even if spreading out at relatively slow sub-light speeds, it – or its artificial surrogates, machines – will have reached every nook and cranny. Thus we should have noticed it, or been noticed by it, unless we are truly the only example of intelligent life.

The Fermi Paradox comes with a ton of caveats and variants. It’s not hard to think of all manner of reasons why intelligent life might be teeming out there, but still not have met us – from self-destructive behavior to the realistic hurdles of interstellar travel. But to my mind Mass Effect has what is perhaps one of the most interesting, if not entertaining, solutions. This will spoil the story; you have been warned.

Without going into all the colorful details, the central premise is that a hugely advanced and ancient race of artificially intelligent machines ‘harvests’ all sentient, space-faring life in the Milky Way every 50,000 years. These machines otherwise lie dormant out in the depths of intergalactic space. They have constructed and positioned an ingenious web of technological devices (including the Mass Effect relays, providing rapid interstellar travel) and habitats within the Galaxy that effectively sieve through the rising civilizations, helping the successful flourish and multiply, ripening them up for eventual culling. The reason for this? Well, the plot is complex and somewhat ambiguous, but one thing that these machines do is use the genetic slurry of millions, billions of individuals from a species to create new versions of themselves.

It’s a grand ol’ piece of sci-fi opera, but it also provides a neat solution to the Fermi Paradox via a number of ideas: a) The most truly advanced interstellar species spends most of its time out of the Galaxy in hibernation. b) Purging all other sentient (space-faring) life every 50,000 years puts a stop to any great spreading across the Galaxy. c) Sentient, space-faring species are inevitably drawn into the technological lures and habitats left for them, and so are less inclined to explore.

These make it very unlikely that until a species is capable of at least proper interplanetary space travel (in the game humans have to reach Mars to become aware of what’s going on at all) it will have to conclude that the Galaxy is a lonely place.

[div class=attrib]Read more after the jump.[end-div]

[div class=attrib]Image: Intragalactic life. Courtesy of J. Schombert, U. Oregon.[end-div]