[JamesLeonis]

The Drake Equation is filled with assumptions, like life must appear on a planet in the Goldilocks zone of a star. The whole equation has only one datapoint to extrapolate from. Tweak the equation's parameters and it will predict universes that only have one civilization per galaxy or worse! We have no way of knowing what those parameters are because we haven't seen other examples.

A major reason we are interested in Europa is because it might have underground oceans. Hypothetically, through tidal forces with Jupiter, the moon's core is hot enough to create oceans under the ice crust. Combined with hydrothermal vents you have the possibility for deep sea life similar to our own deep oceans. The Drake Equation does not predict this possibility.

[mr_mitm]

The Goldilocks zone doesn't enter the Drake equation at all.

As a reminder, this is the equation: https://en.wikipedia.org/wiki/Drake_equation#Equation

It makes very few assumptions.

[buran77]

The equation itself makes no assumptions. But anyone trying to calculate something with it must.

The last five factors in the equation will be filled in by assumptions based entirely on one data point, life on Earth. From your link:

  ne = the average number of planets that can potentially support life per star that has planets.
  fl = the fraction of planets that could support life that actually develop life at some point.
  fi = the fraction of planets with life that go on to develop intelligent life (civilizations).
  fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space.
  L = the length of time for which such civilizations release detectable signals into space.

Can you define any one of those without assumptions, in a scientifically proven way?

[DennisP]

One approach is to give each variable a probability distribution. The greater our uncertainty about possible values, the wider the bell curve.

Drexler and colleagues did that, and found "a substantial probability that we are alone in our galaxy, and perhaps even in our observable universe (53%–99.6% and 39%–85% respectively). ’Where are they?’ — probably extremely far away, and quite possibly beyond the cosmological horizon and forever unreachable."

https://arxiv.org/abs/1806.02404

[mianos]

A probability distribution describes how likely different outcomes are. It requires multiple observations or an assumed model that can represent variability.

[graycat]

Likely are also making a probabilistic independence assumption.

[lazide]

Probability distributions based on a single data point (of where we know there is life) aren’t reliable distributions.

[DennisP]

Which is why they set very wide ranges on the things we know little about. Doing that is less unjustified than guessing specific values, as people have usually done.

It's nowhere near a precise estimate of the probability of life. What it mainly shows is that the Fermi "paradox" is no such thing. It can look that way if we guess specific parameter values, but if we fully account for our uncertainty on the various parameters, then the result is a decent chance that we are alone, given the knowledge we have so far.

[lazide]

I’m not saying precise. I’m saying it isn’t even an estimate.

You can’t have a distribution with one data point.

It’s similar to the arguments about 3I/Atlas being an alien spacecraft because it’s so ‘weird’.

With so few data points, everything is fundamentally ‘weird’ - or normal - we have no way to tell, so making any sort of statistical argument about it is fundamentally useless and misleading, as statistics is based on groups. And we don’t have a group yet.

[Tagbert]

No, it’s just a starting point. We do need more data.

[scarmig]

It does assume that life must be associatable with a planet. It's a plausible assumption, but you could also hypothetically have life develop on a star itself or its remnants, comets, clouds of interstellar gas. Maybe even something more exotic than that (dark matter? some weird correlated statistical properties of the quantum foam?)

[dotancohen]

About forty years ago I read a terrific book about life forms that live on a star. Maybe Starquake was it called? Did to the abundance of energy on the surface of a star, they live their lives a million times faster than humans. Thus for both them and the humans who discover them, communication is difficult. I think the humans push these life forms to develop civilization, which from the human's perspective had them go from primitive animals into sophisticated beings of technology past their own in something like a day.

[LeifCarrotson]

That's "Dragon's Egg" by Robert L. Forward, a classic Sci-fi story:

https://annas-archive.org/md5/4c381ac344506d10037fc8e7747098...

The cheela lived on the surface of a neutron star, and they lived faster because the nuclear physics that powered their metabolism are far faster than the chemical and mechanical physics that power our own.

[squigz]

I'm not against piracy, and I love Anna's Archive... but publicly linking directly to a pirate source for something like this seems wrong. Could've just linked the Wikipedia page and let people acquire however they prefer.

Anyway, sounds interesting, gunna add that to my list

[dreamcompiler]

And "The World at the End of Time" by Frederik Pohl.

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

[DennisP]

There's also Sundiver by David Brin, which has plasma life forms in our sun.

[dotancohen]

Yes, that was it!

[ElFitz]

Andy Weir’s Project Hail Mary had an interesting take on that.

[gcanyon]

I was bothered by the nearly a-scientific-ness of PHM. The story was nicely done in general, but it feels like he pretends to be hard science fiction when he's really Star Trek-level.

[lordnacho]

It actually adds excessive structure.

The underlying model is just:

N*f

How many planets are there, and what proportion of them have detectable life?

The f does not have to be structured as fl->fi->fc, although we can see why you'd assume that kind of structure. It's simple to calculate the PI(series) when the model is just a funnel. Like the Million Dollar Money Drop gameshow.

But you could imagine a more complex model of probabilities that branches and merges. There could be events on the bayesian tree that amplify downstream events. For instance, suppose there is some pathway that if reached will leave certain minerals that future civilizations could use. This has happened already on earth at least once: lignin bearing plants could not be easily digested for a long time, and that led to coal formation during the carboniferous period.

You could imagine many such potential trees, but we only have one iteration.

[howieburger]

Those variables come with embedded assumptions they are essential and meaningful to discovery of life and civilization elsewhere in the universe.

For all we know civilization exists inside our car battery. Why assume it only exists on planets.

It's not explicit in it's assumption but implicit assumption the equation is meaningful.

[PepperdineG]

>For all we know civilization exists inside our car battery.

Rick Sanchez uses a microverse battery

[mr_mitm]

Thanks, I read that part before I shared it. It's pretty clear to me, these are pretty well defined quantities, just hard to measure. What is unclear is perhaps the definition of life. But at no point does it assume a planet must be in the Goldilocks zone. So perhaps you want to point out those assumptions you are talking about to me, because I don't see them.

Edit: the parent post has been edited substantially after I replied.

[buran77]

> these are pretty well defined quantities, just hard to measure.

They are "defined" conceptually, in words, not in physical quantities. It assumes we can assign a known value to any of that when we don't and likely never will. It's like saying "Let X answer the unanswerable question. X is the answer".

> at no point does it assume a planet must be in the Goldilocks zone

You could say it implies it with fl.

> Edit: the parent post has been edited substantially after I replied.

Only for legibility.

[the_af]

How can you extrapolate those terms from a single planet with known life without making assumptions?

[mr_mitm]

I can't, but the equation itself doesn't to that. The assumptions are up to the reader to make. That's why I think that the equation isn't particularly useful.

[crazygringo]

I'm assuming they were referring to this term:

> n_e = the average number of planets that can potentially support life per star that has planets.

The fact that the planet is neither too hot nor too cold would seem to be a major component of this term:

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

[mr_mitm]

That's just your interpretation. Take the equation at its face value and it does allow for life originating around some deep sea vents, like JamesLeonis speculated.

[DennisP]

It does seem unlikely that such life forms would ever become spacefaring.

[rowanG077]

That's a separate term in the equation.

[DennisP]

Yes, but we should consider these linkages when setting values. If we assume that volcanic vent life is very unlikely to become spacefaring, we should either leave it out of the "life" term, or leave it in but lower the probability of the "becomes spacefaring" term.

[acestus5]

yeah you are right the Drake equation does not assume Goldilocks zone.

[stouset]

It goes the other way around. The Goldilocks zone is a shorthand attempt at helping us guess how many planets out there are capable of supporting life.

[hotstickyballs]

The biggest assumption is that it assumes only a single path to intelligent life.

[corimaith]

Even if you only had a handful of civilizations, the sheer time that has passed and size of the universe should mean that life should still be alot more apparent.

With sublight velocities achievable today, I recall it would only take around a million years for a Von Newmann probe to cover the entire galaxy. Such a probe is quite conceivable, so why isn't there more evidence of such probes everywhere?

Another point I feel is that proliferation of life should be an self-reinforcing affair, for intelligent life even more so. A spacefaring nation may terraform or just seed planets, and these in time will replicate similar behaviors. At a certain point, a galaxy teeming with life should be very hard to reverse given all the activity. A life itself isn't necessarily evolved from biology, AI machine lifeforms should also well suited to proliferate, yet we don't see them anyways.

[littlestymaar]

> With sublight velocities achievable today, I recall it would only take around a million years for a Von Newmann probe to cover the entire galaxy. Such a probe is quite conceivable, so why isn't there more evidence of such probes everywhere?

What are the incentives to build and deploy such a thing though? We as a civilization fail to fund things that have a ROI of more than a few years, how are you going to fund something that pays off after a million year?

[antonvs]

Exactly. Some of the biggest explanatory factors for the Fermi paradox are likely to be economics and politics: interstellar travel is unreasonably expensive, unimaginably slow, and has negative ROI unless your time horizons are beyond anything that's ever been used on Earth.

Consider that in some countries on Earth, we can't even get consensus that obtaining energy directly from the Sun via solar panels is a good idea.

[littlestymaar]

Also, people vastly underestimate how hostile space is: colonizing Mount Everest, the Antarctic or the continental plateau under sea would be far easier than colonizing Mars. And Mars is the most hospitable extraterrestrial place we know of.

[corimaith]

I don't think we would colonizing Mars, free floating colonies akin to O'Neil Cylinders orbiting Earth would probably be the more logical option. And with increasing robotic automation capabilities, it's not improbable to see these being built in the future.

[antonvs]

> it's not improbable

"Extremely improbable" would be a better assessment.

Even ignoring the project complexity, difficulty, and energy budget, which can't simply be handwaved away by "robotic automation", one reason is simply that such colonies don't solve any problem that we're likely to have, that can't be solved much more cheaply, safely, and effectively.

But even the idea that we'll eventually have the technology to build such structures is debatable. Will this be before or after we solve climate change, for example? Because that issue is likely to severely impact our technological capabilities over the timescales involved. And as of today, the most technologically advanced nation is doubling down on atmospheric carbon production.

[littlestymaar]

Having the technology to build it isn't the hard part. The question is why you'd do that in the first place and who would fund such a colony.

First of all it's going to be massively more expensive than any housing we've ever built on earth so only a very small elite could afford living there.

But then again, space is a very hostile environment: it's super dangerous (any incident will almost certainly snowball into a dramatic accident), very unhealthy (billionaires are currently funding longevity research, so I don't think they'd like to go in a place where they would age up significantly faster than on earth…), and life is just worse up there on all respect…

[mr_toad]

At some point replicative drift will set in. How many replications is two million years? How long before the probes evolve? How long before they speciate? How long before a species turns on itself?

[fooker]

> Such a probe is quite conceivable, so why isn't there more evidence of such probes everywhere?

Time, not space, is your answer here.

Two reasons -

(1) civilizations might not survive long enough to do this.

(2) 13 billion years is a long time. So you have the reciprocal of that as the chances to be in the right year to see such a probe. And with results from the new telescope we now have hints that the 13 billion number is bogus, the universe is likely far older.

[raverbashing]

Yup

The fundamental problem with the Drake equation is that it's frequentist, not Bayesian

Hence why you get too high sensitivity to parameters you have no way of having an estimate with a small margin of error

We "don't care" about how many civilisations are out there, we care to the point where we can interact with them.

As mentioned, it has several assumptions. "Rate of birth of sun like stars" means nothing. You can "always" have an exception for life that will throw the data off: "star too bright but with a hot Jupiter tidally locked in front of your moon, shielding it" etc

[antonvs]

> star too bright but with a hot Jupiter tidally locked in front of your moon, shielding it

It seems unlikely that such exceptions would amount to more than part of a reasonable margin of error.

[raverbashing]

It is very likely that Earth itself is the exception of the exception and is part of a "margin of error"

[adastra22]

FYI just about every outer solar system moon or planetoid has a liquid ocean somewhere underneath. Europa is neither exceptional or even that interesting anymore.

[bethekidyouwant]

Not really there’s always gonna be water comets in the frost zone.