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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 ass

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?

mr_mitm 1y ago
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.
- the_af 1y ago
  How can you extrapolate those terms from a single planet with known life without making assumptions?
  - mr_mitm 1y ago
    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.
- buran77 1y ago
  > 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.
howieburger 1y ago
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 1y ago
  >For all we know civilization exists inside our car battery. Rick Sanchez uses a microverse battery
scarmig 1y ago
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 1y ago
  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 1y ago
    That's "Dragon's Egg" by Robert L. Forward, a classic Sci-fi story: https://annas-archive.org/md5/4c381ac344506d10037fc8e774709863 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.
    - DennisP 1y ago
      There's also Sundiver by David Brin, which has plasma life forms in our sun.
    - dotancohen 1y ago
      Yes, that was it!
    - squigz 1y ago
      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
DennisP 1y ago
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 https://arxiv.org/abs/1806.02404
- mianos 1y ago
  A probability distribution describes how likely different outcomes are. It requires multiple observations or an assumed model that can represent variability.
  - graycat 1y ago
    Likely are also making a probabilistic independence assumption.
- lazide 1y ago
  Probability distributions based on a single data point (of where we know there is life) aren’t reliable distributions.
  - Tagbert 1y ago
    No, it’s just a starting point. We do need more data.
  - DennisP 1y ago
    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.
lordnacho 1y ago
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.

mr_mitm 1y ago

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.

the_af 1y ago
How can you extrapolate those terms from a single planet with known life without making assumptions?
- mr_mitm 1y ago
  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.
buran77 1y ago
> 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.

howieburger 1y ago

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 1y ago
>For all we know civilization exists inside our car battery. Rick Sanchez uses a microverse battery

scarmig 1y ago

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 1y ago
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 1y ago
  That's "Dragon's Egg" by Robert L. Forward, a classic Sci-fi story: https://annas-archive.org/md5/4c381ac344506d10037fc8e774709863 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.
  - DennisP 1y ago
    There's also Sundiver by David Brin, which has plasma life forms in our sun.
  - dotancohen 1y ago
    Yes, that was it!
  - squigz 1y ago
    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

DennisP 1y ago

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 https://arxiv.org/abs/1806.02404

mianos 1y ago
A probability distribution describes how likely different outcomes are. It requires multiple observations or an assumed model that can represent variability.
- graycat 1y ago
  Likely are also making a probabilistic independence assumption.
lazide 1y ago
Probability distributions based on a single data point (of where we know there is life) aren’t reliable distributions.
- Tagbert 1y ago
  No, it’s just a starting point. We do need more data.
- DennisP 1y ago
  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.

lordnacho 1y ago

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.