Reality Straight Up!

Thoughts & Observations of a Free Range Astrophysicist

Looking for E.T.

Where Are They?

Why E.T. might stay home

It would be fun to think there is a flourishing interstellar civilization of humanoid aliens out there. But then it would also be nice to believe in unicorns and midichlorians. It would be nice, but they probably aren’t there.

This article originally appeared in my Astronomy Magazine column, For Your Consideration.


Along with a lot of you out there, I grew up on stories of sprawling interstellar societies full of creatures very like us. Spacecraft powered by unexplained technologies sidestep the laws of physics as we know them, allowing various species of bipedal humanoids to get together and do what we bipedal humanoids are wont to do. I still love a good space opera. But, alas, such things are not to be.

Enrico Fermi wondered, “If E.T. is out there, why aren’t they here?”

During an informal lunchtime conversation at Los Alamos in 1950, a group of physicists were joking about a cartoon in The New Yorker depicting aliens and a flying saucer. The cartoon inspired Enrico Fermi to ask a simple question: “Where are they?”

Enrico Fermi

Enrico Fermi was a brilliant, Nobel-Prize-winning nuclear physicist, but his name is perhaps just as widely recognized for his question, “Where is E.T.?”

If the universe contains numerous intelligent civilizations whose inhabitants routinely travel among the stars, then, Fermi reasoned, those civilizations should quickly spread throughout the galaxy. Yet, fantastical claims about UFOs aside, there is no evidence that we have been visited. Fermi never thought of this as a paradox. (That term didn’t appear for another 25 years.) He just took it as evidence that interstellar travel must be really hard, and that coming to Earth isn’t worth the effort.

For biological creatures, interstellar travel is hard

Concerns about the difficulty of interstellar travel are well founded. In the real world, you don’t get to sidestep physics, and physics says that sending humans across interstellar distances would require vast resources and journeys lasting many lifetimes.

From suspended animation to zygote-laden incubator ships to multigenerational vessels, people have played with lots of ideas for how we might mount such a campaign. But any way you slice it, space is a hostile environment for biological organisms. Protecting passengers and keeping them alive and healthy for centuries or more is a formidable task.

Then there are the extraordinary psychological stresses involved. Drawing on experience with Antarctic exploration, long-duration space flight, and numerous experiments aimed at understanding the human factors encountered during a quick trip to Mars, one thing seems clear. Managing the isolation, confinement, culture, and other psychosocial aspects of interstellar travel could be as daunting as the challenges facing spacecraft engineers. It seems likely that any intelligent social species would face their own versions of such hurdles.

E.T. and humans doubtless have very different biochemistry

Evolution has no destination. Each time you push the “go” button, you end up someplace different. Start things over on Earth (or on another Earth-like planet) and not only would there be different species with perceptions and intelligences that vary wildly from our own, the very chemistry of life would be altered as well!

That’s conjecture — but it’s pretty safe conjecture. To see why, let’s do a quick back-ofthe-envelope calculation.

Among other things, our DNA contains instructions for building proteins out of sequences of amino acids. For simplicity, let’s assume that life always evolves that same basic molecular machinery. There are 500 or so known amino acids, of which life on Earth uses only 23. Sticking with our KISS (keep it simple, stupid) approach, let’s assume all life uses those same 23.

Protein Molecule

There are 10613 different possible proteins with a length of 450 amino acids. Only about 10 million of those are used by life on Earth. The likelihood that life elsewhere uses any of those same proteins is effectively zero.

The average protein in a eukaryotic (nucleus-containing) cell on Earth is about 450 amino acids long. There are therefore 23450 (=10613) different proteins of that length that the machinery of our DNA might construct. That’s a huge number! Not surprisingly, terrestrial life has stumbled upon uses for only a small fraction of those possible proteins — about 10 million.

So now let’s take those 10613 possible proteins and split them into planet-proportioned groups of 10 million each. With no overlap at all, there would be 10606 of those piles! There are no more than about 1023 habitable planets in the entire observable universe. You could spread those stacks of proteins over the planets in 10583 similar universes without having to duplicate a single protein on any two planets!

The takeaway is this: The likelihood that any two lifebearing planets in the universe share even remotely compatible biochemistry is effectively zero.

That interstellar civilization might still exist. Watch this space.

Put all of that together, and a civilization looking at Earth as an interstellar destination might reasonably assume three things: 1) The existence of life means that Earth is at best useless and at worst highly poisonous, 2) communication might be as problematic as communication between humans and octopuses, and 3) a decision to send emissaries in our direction would be costly indeed.

So perhaps the answer to Fermi’s question is that everybody out there with technology that might allow them to travel the stars in search of life understands that there is no reason to do so.

Or perhaps not.

Personally, I think there probably is a thriving civilization out among the stars. Watch this space.

Where Are They? ^ Why E.T. might stay home  © Dr. Jeff Hester
Content may not be copied to other sites. All Rights Reserved.

Reality Straight Up!

  • A Dunning-Kruger Universe  Everyone, it seems, has a “theory”Posted in For Your Consideration
  • Our Need to Know  We crave certainty, even when it is only an illusionPosted in CoachingThoughts
  • A Saguaro’s universe  Building a cactus starts with the Big BangPosted in For Your Consideration
  • Oklahoma Skies  To all the amateurs out there, thanks!Posted in For Your Consideration
  • Fight-or-Flight  How our Pleistocene brains (mis)handle modern threatsPosted in Coaching
  • In a Shark’s Eye  Science and the experience of wonderPosted in For Your Consideration
  • The Quandry of Unpredictability  Chaos, climate and an unpredictable futurePosted in For Your Consideration
  • Why I March for SciencePosted in Thoughts
  • Waiting for Skynet  The benefits of being a machinePosted in For Your Consideration
  • Where Are They?  Why E.T. might stay homePosted in For Your Consideration
  • Pulsars and Neutrinos  The history that LIGO forgotPosted in For Your Consideration
  • Not The End of Science  The emerging science of processPosted in For Your Consideration
  • A Dunning-Kruger Universe
    Everyone, it seems, has a “theory”

    Some people are sure they know more than the experts, but it can take a lot of knowledge to realize just how wrong an idea is.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

    Read Article

  • Our Need to Know
    We crave certainty, even when it is only an illusion

    The human brain craves the sensation of knowing like a drug addict craves the next fix. If real knowledge is uncomfortable or not at hand, we are quite content to just make something up, then convince ourselves it’s real. In a world where knowledge matters, that’s dangerous.

    Read Article

  • A Saguaro’s universe
    Building a cactus starts with the Big Bang

    The iconic saguaro cactus gives the desert an otherwordly beauty. That beauty does not exist in isolation. It embodies the fascinating and awe-inspiring processes that have shaped the universe, going all the way back to the Big Bang itself.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

    Read Article

  • Oklahoma Skies
    To all the amateurs out there, thanks!

    Looking at room full of amateur astronomers, gathered for the Okie-Tex Star Party under the spectacularly dark skies of the Oklahoma Panhandle, I am reminded of my own roots and those who helped me discover the universe.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

    Read Article

  • Fight-or-Flight
    How our Pleistocene brains (mis)handle modern threats

    A strong fight-or-flight reaction served our evolutionary ancestors well. If the leopard catches you, that’s it! But today a visceral response to a not-so-mortal threat seldom improves things. If you want to get a handle on those intense, counterproductive bouts of emotion, start by understanding where fight-or-flight came from in the first place.

    Read Article

  • In a Shark’s Eye
    Science and the experience of wonder

    Alone, 100 feet underwater, with a shark in its element, I am overwhelmed by a mixture of awe, beauty, joy, and intellectual wonder at the world that brings us together. In that moment, I experience just what science is all about.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

    Read Article

  • The Quandry of Unpredictability
    Chaos, climate and an unpredictable future

    Chaos is a sticky wicket for science. There are things a correct theory like climate change cannot predict, but there are a lot of things that it can. It’s important to understand which is which.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

    Read Article

  • Why I March for Science

    On Earth Day, April 22, 2017, people around the nation will March for Science. It seems strange to need to march in support of the idea that pronouncements from politicians cannot change the nature of reality, or that evidence matters when making decisions. But such are the peculiar times in which we live.

    Read Article

  • Waiting for Skynet
    The benefits of being a machine

    For biological organisms, interstellar travel is hopelessly difficult, and probably pointless. For sentient machines, however, home is the environment you were built for.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

    Read Article

  • Where Are They?
    Why E.T. might stay home

    It would be fun to think there is a flourishing interstellar civilization of humanoid aliens out there. But then it would also be nice to believe in unicorns and midichlorians. It would be nice, but they probably aren’t there.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

    Read Article

  • Pulsars and Neutrinos
    The history that LIGO forgot

    Gilding the lily makes everybody look bad. When the Laser Interferometer Gravitational-Wave Observatory detected ripples in the fabric of space-time from a pair of merging black holes, it was a technological and scientific accomplishment without peer! But LIGO did not “discover” gravity waves.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

    Read Article

  • Not The End of Science
    The emerging science of process

    Fundamental change is always messy. As science tackles the complex processes that shape the real world it is having to reinvent itself on the fly. Welcome to the Wild West!

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

    Read Article

Click on thumbnail to select post:

Recent Article Mobile

  • A Dunning-Kruger Universe  Everyone, it seems, has a “theory”Posted in For Your Consideration
  • Our Need to Know  We crave certainty, even when it is only an illusionPosted in CoachingThoughts
  • A Saguaro’s universe  Building a cactus starts with the Big BangPosted in For Your Consideration
  • Oklahoma Skies  To all the amateurs out there, thanks!Posted in For Your Consideration
  • Fight-or-Flight  How our Pleistocene brains (mis)handle modern threatsPosted in Coaching
  • In a Shark’s Eye  Science and the experience of wonderPosted in For Your Consideration
  • The Quandry of Unpredictability  Chaos, climate and an unpredictable futurePosted in For Your Consideration
  • Why I March for SciencePosted in Thoughts
  • Waiting for Skynet  The benefits of being a machinePosted in For Your Consideration
  • Where Are They?  Why E.T. might stay homePosted in For Your Consideration
  • Pulsars and Neutrinos  The history that LIGO forgotPosted in For Your Consideration
  • Not The End of Science  The emerging science of processPosted in For Your Consideration
  • Some people are sure they know more than the experts, but it can take a lot of knowledge to realize just how wrong an idea is.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

  • The human brain craves the sensation of knowing like a drug addict craves the next fix. If real knowledge is uncomfortable or not at hand, we are quite content to just make something up, then convince ourselves it’s real. In a world where knowledge matters, that’s dangerous.

  • The iconic saguaro cactus gives the desert an otherwordly beauty. That beauty does not exist in isolation. It embodies the fascinating and awe-inspiring processes that have shaped the universe, going all the way back to the Big Bang itself.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

  • Looking at room full of amateur astronomers, gathered for the Okie-Tex Star Party under the spectacularly dark skies of the Oklahoma Panhandle, I am reminded of my own roots and those who helped me discover the universe.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

  • A strong fight-or-flight reaction served our evolutionary ancestors well. If the leopard catches you, that’s it! But today a visceral response to a not-so-mortal threat seldom improves things. If you want to get a handle on those intense, counterproductive bouts of emotion, start by understanding where fight-or-flight came from in the first place.

  • Alone, 100 feet underwater, with a shark in its element, I am overwhelmed by a mixture of awe, beauty, joy, and intellectual wonder at the world that brings us together. In that moment, I experience just what science is all about.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

  • Chaos is a sticky wicket for science. There are things a correct theory like climate change cannot predict, but there are a lot of things that it can. It’s important to understand which is which.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

  • On Earth Day, April 22, 2017, people around the nation will March for Science. It seems strange to need to march in support of the idea that pronouncements from politicians cannot change the nature of reality, or that evidence matters when making decisions. But such are the peculiar times in which we live.

  • For biological organisms, interstellar travel is hopelessly difficult, and probably pointless. For sentient machines, however, home is the environment you were built for.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

  • It would be fun to think there is a flourishing interstellar civilization of humanoid aliens out there. But then it would also be nice to believe in unicorns and midichlorians. It would be nice, but they probably aren’t there.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

  • Gilding the lily makes everybody look bad. When the Laser Interferometer Gravitational-Wave Observatory detected ripples in the fabric of space-time from a pair of merging black holes, it was a technological and scientific accomplishment without peer! But LIGO did not “discover” gravity waves.

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

  • Fundamental change is always messy. As science tackles the complex processes that shape the real world it is having to reinvent itself on the fly. Welcome to the Wild West!

    This article originally appeared in my Astronomy Magazine column, For Your Consideration.

Over his 30 year career as an internationally known astrophysicist, Dr. Jeff Hester was a key member of the team that repaired the Hubble Space Telescope. With one foot always on the frontiers of knowledge, he has been mentor, coach, team leader, award-winning teacher, administrator and speaker, to name a few of the hats he has worn. His Hubble image, the Pillars of Creation, was chosen by Time Magazine as among the 100 most influential photographs in history.
©Dr. Jeff Hester LLC, 5301 S. Superstition Mountain Dr., Suite 104 #171, Gold Canyon, AZ 85118