During my morning walk yesterday I was listening to Krista Tippett on the On Being podcast interviewing Jill Tarter, astronomer and co-founder of the SETI Institute, the Search for Extra Terrestrial Intelligence. (You can find the podcast at It Takes a Cosmos to Make a Human.) Jill was the inspiration behind the Jodie Foster character in the movie Contact, based on a novel by the cosmologist and visionary Carl Sagan.

A couple of weeks ago I mentioned the overview effect, the phenomenon experienced by astronauts looking back at our Earth from afar, and appreciating its vulnerability, uniqueness, and preciousness. The SETI perspective is somewhat similar. I’ll come back to that in a moment, but first, some background.

The SETI Institute was founded in 1984, and has been searching for evidence of extra-terrestrial intelligence ever since. Despite massive progress in Earth-based and space-based telescopes, no luck so far.

Admittedly, we’ve only explored up to around 4 billion miles from Earth, which would be a good long walk, but in the overall scale of the universe – or even the Milky Way – is effectively just around the corner, not even outside our own solar system.

But if there was intelligent life out there, rather than us having to go looking for it, wouldn’t it have made contact with us?

This is where we come to the Drake Equation. (Ah, thank heavens! you may be thinking… for once she’s not banging on about the IPAT equation!)

Simple, right?!

Actually, it’s quite easy to make sense of it once you know what the variables mean.

(Not to be confused with the search for Intelligent Wife.)

(Joe Scott does a good explanation of it on this video.)

According to Wikipedia, current estimates of the value of N (N being the number of civilisations in the Milky Way) vary from 9.1 × 10−13. i.e., suggesting that we are probably alone in this galaxy, and possibly in the observable universe, to 15,600,000, i.e. our galaxy is pretty darn crowded with friends (hopefully) we just haven’t met yet.

This brings us to the Fermi Paradox, most concisely stated as, “But where is everybody?” If there is indeed intelligent life out there, where are they? Haven’t they seen the Hollywood sci-fi movies? – they’re supposed to say hi to the humans, and ask to be taken to our leader!

(Joe Scott is good on the Fermi Paradox too.)

Suggestions fall into four main categories:

– we actually are all alone

– intelligent extra-terrestrial beings are extremely rare

– they exist – or who knows, could even be here already – but for various reasons we see no evidence (e.g. they exist in a dimension not perceivable by us, they choose to remain hidden, they are waiting and watching, etc.)

– the lifetime of such civilisations is short

This last category is maybe the most cautionary one. As I’ve written before, human empires are historically short-lived. It’s only been 50 years since the moon landing, and already we’re staring down the barrel of our own collapse. Hopefully we will have many centuries of space exploration ahead of us, but that is far from certain. For interplanetary civilisations to make contact with each other, they need to have some chronological overlap (adjusting for the speed of light) in which one civilisation has the technology to transmit, and another has the technology to receive the transmission.

As of now, we have yet to find any evidence of life on planets other than our own, let alone intelligent life. As far as we know, we might be all there is.

How does that make you feel? Special? Lonely? Grateful to be alive?

We take ourselves so much for granted, and yet we are absolutely amazing (even on a bad hair day). We have these incredibly useful and adaptable bodies that can climb mountains and row oceans. We have brains that have found ways to split the atom and understand quantum physics. We have emotions that make us capable of superhuman courage and allow us to appreciate the beauty of a symphony or an oil painting. Yet we walk around like we’re just another run-of-the-mill creature, rarely pausing even to appreciate our opposable thumbs (which we mostly use for texting on smartphones).

Jill Tarter’s main point, much like the overview effect mentioned above, is – we’re all on this Earth together. From down here, we mostly see what makes us different. But from space, we would all look very similar. An alien might notice that humans come in different shapes, sizes, and colours, but to the alien we would all be Earthlings, united by our shared habitation of this beautiful and infinitely varied planet. The alien might think it strange that we squabble with each other, make a mess of our home, and generally behave in ways incompatible with our long-term health and wellbeing.

As Jill says, if we would only recognise our shared humanity, and our shared dependence on this very special lump of rock, it goes without saying that we would take better care of it – and of each other.

I’ll leave you with Monty Python’s Galaxy Song…. Especially fast forward to the last two lines (lyrics below the video). And also Carl Sagan’s beautiful words about the pale blue dot.

Whenever life gets you down Mrs. Brown
And things seem hard or tough
And people are stupid, obnoxious or daft
And you feel that you’ve had quite enough…

Just, remember that you’re standing on a planet that’s evolving
And revolving at nine hundred miles an hour
That’s orbiting at nineteen miles a second, so it’s reckoned
A sun that is the source of all our power

The sun, and you and me, and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm at forty thousand miles an hour
Of the galaxy we call the Milky Way

Our galaxy itself, contains a hundred billion stars
It’s a hundred thousand light years side-to-side
It bulges in the middle, sixteen thousand light years thick
But out by us it’s just three thousand light years wide

We’re thirty thousand light years from galactic central point
We go round every two hundred million years
And our galaxy is only one of millions of billions
In this amazing and expanding universe

The universe itself keeps on expanding and expanding
In all of the directions it can whiz
As fast as it can go, the speed of light you know
Twelve million miles a minute and that’s the fastest speed there is

So remember when you’re feeling very small and insecure
How amazingly unlikely is your birth
And pray that there’s intelligent life somewhere up in space
Cause there’s bugger-all down here on Earth


Carl Sagan on the Pale Blue Dot:

“Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there-on a mote of dust suspended in a sunbeam.

The Earth is a very small stage in a vast cosmic arena. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot.

Our posturings, our imagined self-importance, the delusion that we have some privileged position in the Universe, are challenged by this point of pale light. Our planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yes. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.”

― Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space

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