No, We Haven’t Solved The Drake Equation, The Fermi ...aldous/Real_World/fermi_riposte.pdf · uncertainties dissolves the Fermi paradox by showing that it is not at all unlikely…

7/19/2018 No, We Haven’t Solved The Drake Equation, The Fermi Paradox, Or Whether Humans Are Alone

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Ethan Siegel Follow

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer,astrophysicist, science communicator & NASA columnist.Jul 3 · 7 min read

No, We Haven’t Solved The Drake Equation,The Fermi Paradox, Or Whether HumansAre AloneThe absence of evidence is not evidence of absence,but substituting wild speculation for evidence isn’teven science.

. . .

In 1950, Enrico Fermi famously asked the question, “Where is

everybody?” It wasn’t because his retinas detached; it was because he

was curious about the lack of visits by extraterrestrials. If life in the

Universe is ubiquitous, the argument goes, then surely the signs of it

should be everywhere? Over the past 60+ years, we’ve developed a

number of possible explanations for this puzzle, known today as the

Fermi Paradox.

Intelligent aliens, if they exist in the galaxy or the Universe, might be detectable from a variety of

signals: electromagnetic, from planet modi�cation, or because they’re spacefaring. But we haven’t

found any evidence for an inhabited alien planet so far. We may truly be alone in the Universe, but the

honest answer is we don’t know enough about the relevant probability to say so. (Ryan Somma

/ �ickr)

https://medium.com/@startswithabang?source=post_header_lockup

https://medium.com/@startswithabang?source=post_header_lockup

https://en.wikipedia.org/wiki/Fermi_paradox



On the surface, this seems like a reasonable question to ask. There are

billions of stars in the galaxy, many of which have Earth-like planets,

and if Earth is fairly typical, some of these may have developed

intelligent life. Many of us on Earth are working to develop interstellar

travel, and even though the galaxy is 100,000 light years across, we’ve

been around for many billions of years. If life is common, then where is

everyone? A new paper claims to have the answer, but their

conclusions are highly suspect.

Clearly, if they’re out there, they haven’t shown up around these parts

or left sure�re signs of their existence. Our searches for alien

civilizations — such as with giant radio dishes and projects like SETI —

have all come up empty, with no signatures of an alien intelligence out

there. UFOs are likely to have earthly explanations, not extraterrestrial

ones. Exoplanetary searches, exempli�ed by NASA’s Kepler mission,

have turned up thousands of planets beyond Earth, many of which are

Earth-like in size, teaching us that there are literally billions of chances

for Earth-like life in our galaxy alone. Yet no life beyond Earth has ever

been found; not on those worlds, nor on any of the other worlds in our

Solar System.

An artist’s rendition of a potentially habitable exoplanet orbiting a sun-like star. When it comes to life

beyond Earth, we have yet to discover our �rst inhabited world. (NASA Ames / JPL-Caltech)

https://arxiv.org/pdf/1806.02404.pdf

https://en.wikipedia.org/wiki/Search_for_extraterrestrial_intelligence



Water, light, heat, organic molecules, and the ingredients for life are

indeed everywhere. But aliens of any type have yet to show themselves.

For all we have hard evidence for, Earth may be it for life in the entire

Universe.

If that sounds pessimistic to you, or, as Carl Sagan put it, “an awful

waste of space,” you’re not alone. Back in the early 1960s, Frank Drake

put forth an equation that allowed us to make an estimate of the

number of spacefaring, intelligent alien civilizations out there — in

either our galaxy or the entire observable Universe — at any point in

time. Although we knew very little about the various parameters in it,

the Drake Equation is still used by many today to estimate the number

of potential civilizations we can communicate with in space.

The hematite spheres (or ‘Martian blueberries’) as imaged by the Mars Exploration Rover. These are

almost certainly evidence of past liquid water on Mars, and possibly of past life. NASA scientists

must be certain that this site — and this planet — are not contaminated by the very act of our

observing. As of yet, there is no sure�re evidence for either past or present Martian life. (NASA/JPL-

Caltech/Cornell/ASU)

https://www.goodreads.com/quotes/282727-the-universe-is-a-pretty-big-place-if-it-s-just

https://www.forbes.com/sites/startswithabang/2018/04/05/the-drake-equation-is-broken-heres-how-to-fix-it/



While we can make better estimates, today, of quantities like:

the number of stars in each galaxy,

the number of galaxies in the Universe,

the fraction of stars that are like our Sun,

and the fraction of Sun-like stars with potentially habitable, Earth-

sized planets,

there are still a few enormous unknowns that are out there.

•

•

•

•

The Drake equation is one way to arrive at an estimate of the number of spacefaring, technologically

advanced civilizations in the galaxy or Universe today. But until we know how to estimate these

parameters, we’re just guessing at the possible answers. (University of Rochester)

The possibilities of having another inhabited world in our Milky Way are incredible and tantalizing,

but if we want to know whether it’s real or not, we absolutely have to get the science right.

(Wikimedia Commons user Lucianomendez)



In particular, there are a few steps that we simply don’t know how

frequently they occur. They clearly occurred here on Earth, but we

haven’t, as of yet, discovered anyplace else in the Universe where even

one has occurred. These are the steps that lead us from non-living

molecules to the complex, di�erentiated, intelligent species that we

fancy ourselves to be.

This equates to two (in the Drake equation) unknowns that are

absolutely necessary to reach the ultimate goal of intelligent aliens:

the likelihood of creating life from non-life on an Earth-like world,

and the likelihood of that life evolving into an intelligent,

communicative, and possibly interstellar species.

In terms of raw probability, we have no idea how likely or unlikely these

events are.

Sure, there are plenty of sensible things we can say about them. We can

talk about the experiments we’ve done to create organic molecules

from raw, inorganic ingredients. We can discuss the complex organic

molecules we �nd in interstellar space or in meteorites. We can

mention the tantalizing hints that worlds in our Solar System house

1.

2.

Structures on ALH84001 meteorite, which has a Martian origin. Some argue that the structures shown

here may be ancient Martian life, but others contend that this is Earth-originating life that has made

its way into a Martian rock. No such fossils have been found in situ in the rocks examined on Mars.

(NASA, 1996)



about watery pasts, sub-surface liquid oceans, and potentially fossilized

microbes. And we can look at the fact that, if we extrapolate the genetic

information encoded in extant organisms back to the formation of the

Earth, they indicate that what we consider “life” to be may have had its

origin billions of years before our planet came into existence.

But none of that is reasonable for calculating a probability for the

likelihood of life arising from non-life, given an Earth-like world. The

odds may be extremely high, like a few percent, as some have

estimated. But the odds could be catastrophically low: one-in-a-million,

or even worse. Life could be incredibly rare. The fact that life exists on

Earth does not mean we didn’t win the cosmic lottery. We cannot draw

a reasonable conclusion from a sample size of one.

And things get even worse if you try and extrapolate that second

conditional probability: given life, what are the odds that it becomes

intelligent, sentient, spacefaring and communicative across interstellar

distances?

On this semilog plot, the complexity of organisms, as measured by the length of functional non-

redundant DNA per genome counted by nucleotide base pairs (bp), increases linearly with time. Time

is counted backwards in billions of years before the present (time 0). Note that, if we do this

extrapolation, we might conclude that life on Earth began billions of years prior to Earth’s formation.

(Shirov & Gordon (2013), via https://arxiv.org/abs/1304.3381)

https://arxiv.org/abs/1304.3381%29



Again, we have a sample size of one. There are many steps that life took

on Earth to bring us to this point, including mass extinctions, selection

pressures, a changing environment, asteroid strikes, and much, much

more. For over four billion years on this world, there was nothing we’d

call “intelligent” by human standards. For over half a billion since the

Cambrian explosion, it’s only for the past 200,000 or so that a species-

of-interest existed on Earth: less than 0.05% of that time. And

remember: we are the great cosmic success story. We are the winners of

the cosmic lottery.

The Atacama Large Millimeter submillimeter Array (ALMA) are some of the most powerful radio

telescopes on Earth. These telescopes can measure long-wavelength signatures of atoms, molecules,

and ions that are inaccessible to shorter-wavelength telescopes like Hubble, but can also measure

details of protoplanetary systems and, potentially, alien signals, that even infrared telescopes can’t

see.(ESO/C. Malin)



The new paper that is getting a lot of buzz right now, by Anders

Sandberg, Eric Drexler, and Toby Ord of Oxford, is titled Dissolving the

Fermi Paradox, and their main argument is this:

Our main result is to show that proper treatment of scienti�c

uncertainties dissolves the Fermi paradox by showing that it is not at all

unlikely… for us to be alone in the Milky Way, or in the observable

universe.

The Earth at night emits electromagnetic signals, but it would take a telescope of incredible

resolution to create an image like this from light years away. Humans have become an intelligent,

technologically advanced species here on Earth, but we occupy only a tiny fraction of Earth’s history

in time. (NASA’s Earth Observatory/NOAA/DOD)




This is not a surprise to anyone who has thought about the

consequences of drawing sweeping conclusions from a position of

insu�cient evidence and ignorance. If you haven’t thought about it, the

main results is that you probably shouldn’t do it if you care about your

conclusions being based in facts.

You cannot simply state, “here are my estimates for these quantities”

and then calculate how many civilizations you expect. What are the

probability ranges for your estimates? How robust are they? What

evidence backs them up?

It’s long been theorized that the �rst detection of extraterrestrial intelligence will come from radio

waves. The lack of an observed signal doesn’t mean that aliens aren’t out there, transmitting, or

waiting to be discovered. But drawing conclusions about the number of civilizations out there

without any such evidence is not only a fool’s errand, it’s unscienti�c. (Danielle Futselaar)



The answer is “none.”

Despite the replacement of point estimates with probabilistic

distributions, as the authors impose, there is still no evidence that we

can say anything sensible about these likelihoods. In the absence of

evidence, theorists aren’t theorizing based on sound science; they’re

simply making numbers up. The authors state their methodology as

such:

In this paper, we shall look at two di�erent ways of extending this

approach beyond a toy model — generating probability distributions for

the parameters of the Drake equation based on the variation in

historical estimates and doing so based on the authors’ best judgment

of the scienti�c uncertainties for each parameter.

Unfortunately, this falls prey to what I call the �rst law of computer

science: garbage in, garbage out. Historical estimates and the authors’

judgments are no substitute for the data we need, and do not have.

Alan Chinchar’s 1991 rendition of the proposed Space Station Freedom in orbit. Any civilization that

creates something like this would de�nitely count as scienti�cally/technologically advanced, but

inferring their existence is no more than wishful thinking at this point.(NASA)


https://en.wikipedia.org/wiki/Garbage_in,_garbage_out



No amount of fancy probabilistic analysis can justify treating guesswork

and wishful thinking as having any sort of scienti�c weight. Applying

scienti�c techniques to an inherently unscienti�c endeavor, such as

inventing estimates to unknowns about the Universe, doesn’t make it

any more scienti�c. The opposite of knowledge isn’t ignorance; it’s the

illusion of knowledge.

It’s still possible that life, and even intelligent life, is ubiquitous in our

galaxy and the Universe. It’s also possible that one is common and one

is uncommon, or that both are extraordinarily rare. Until we have more

information, don’t be fooled by the headlines: these aren’t brilliant

estimates or groundbreaking work. It’s guessing, in the absence of any

good evidence. That’s no way to do science. In fact, until we have better

evidence, it’s not science at all.

. . .

Once intelligence, tool use and curiosity combine in a single species, perhaps interstellar ambitions

become inevitable. But this is an assumption that isn’t backed in science, and we must be careful

(and suspicious) about any such conclusions we draw from them.(Dennis Davidson for

http://www.nss.org/)

https://www.sciencealert.com/three-of-the-world-s-greatest-minds-just-published-a-disheartening-take-on-the-fermi-paradox

http://www.nss.org/%29



Starts With A Bang is now on Forbes, and republished on Medium thanks

to our Patreon supporters. Ethan has authored two books, Beyond The

Galaxy, and Treknology: The Science of Star Trek from Tricorders to Warp

Drive.

https://www.forbes.com/sites/startswithabang/

https://www.patreon.com/startswithabang

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No, We Haven’t Solved The Drake Equation, The Fermi ...aldous/Real_World/fermi_riposte.pdf · uncertainties dissolves the Fermi paradox by showing that it is not at all unlikely…