Speculative Term in Drake's Equation

[Buzz Bloom]

The Drake Equation has been around since 1961,

https://en.wikipedia.org/wiki/Drake_equation​

and there have been some later extrapolations as well. The probability of there being life somewhat similar to Earth life somewhere else in our Milky Way galaxy seems to be strongly dependent on the equation factor

f_l = the fraction of planets that could support life that actually develop life at some point.​

This seems to me the most speculative of all the terms in the Drake equation. For example, the following article discusses the possibility that the Earth's unusual moon may have played an essential role in life occurring on our planet.

http://www.scientificamerican.com/article/moon-life-tides/
​

I have unsuccessfully tried to find any source that discusses the probability of an exoplanet "that could support life" having an unusual moon like the Earth's.

One way of describing the unusual nature of the Earth's moon is that it is the only moon in our solar system that has a larger angular momentum than its planet's rotation.​

Quite a few computer simulation models have been developed to explain the moon's origin. Can someone cite a reference that discusses the statistics from such models so that some ballpark estimate might be made for the probability that an exoplanet might have a moon like ours?

 

[phyzguy]

I think it is worse than this. All of the last four terms in Drake's equation (fl, fi, fc, L) are completely unknown - we can't even begin to estimate them. I hear people say things like, "what if each of these terms is only 1 in 1000...". Sure, but what if each of these terms is 1 in 10^20? We really have no idea.

 

[Buzz Bloom]

Hi phyzguy:

I appreciate that the probabilities for the factors relating to intelligent life are even more speculative than for life. However, my current interest is about any life at least somewhat similar to Earth life, say perhaps carbon and water based and cellular. For this issue, f_l seems the most speculative.

Regards,
Buzz

 

[Chronos]

Most of the terms in the Drake equation are difficult to reliably quantify. While it is widely accepted the moon probably played an important role in the emergence of life on earth, the nature of its influence is still uncertain. You could also make the case there is something fairly unique about every large moon in the solar system, but, Earth remains the only planet known to harbor life. So any unique properties of Earth's moon looks to me like a red herring until we have clear evidence some particular factor was vital to the emergence of life on earth. Factors that are merely favorable towards life only suggest life would be delayed by their absence. My suspicion is the moon probably was favorable, but, not vital to the emergence of life on earth.

 

[Buzz Bloom]

Hi Chronos:

As I said in Post #1, I agree that the role of the moon is speculative. However, I would like to know, if it is possible to do so, what value for f_l could be ballpark estimated assuming that the role of the moon is vital for life to get started. I am hoping that at least one participant in the PF will know enough about the computer simulations of the moon's origins to help me make an estimate of f_i under this assumption.

Regards,
Buzz

 

[Jando]

Even if it turns out that the moon was vital to start life on this planet - that would tell you nothing about the value you're looking for. Because it doesn't tell you anything about whether it's vital for other planets too.

 

[Buzz Bloom]

Even if it turns out that the moon was vital to start life on this planet - that would tell you nothing about the value you're looking for. Because it doesn't tell you anything about whether it's vital for other planets too.

Hi Jando:

I find that the descriptions of the reason given in various sources, e.g. the Scientific American article I cited, seem to all have the characteristic of being necessary for one or more of the pre-life chemical processes to actually occur on any planet that could support life. Which of the particular reasons given in the S.A. article for the moon's necessary role do you find to be restricted to just the Earth?

Regards,
Buzz

 

[Jando]

Which of the particular reasons given in the S.A. article for the moon's necessary role do you find the be restricted to just the Earth?

Awfully sorry, but all of them. :) The article only talks about this solar system, this Earth and this moon. Whether that has any relevance for other systems, other planets and other moons is completely unknown.

 

[Buzz Bloom]

The article only talks about this solar system, this Earth and this moon. Whether that has any relevance for other systems, other planets and other moons is completely unknown.

Hi Jando:

Would you also conclude that whether or not the fact (that Earth has life) has any relevance to life on any other planet in the galaxy is also completely unknown?

Regards,
Buzz

 

[hutchphd]

Would you also conclude that whether or not the fact (that Earth has life) has any relevance to life on any other planet in the galaxy is also completely unknown?

It seems to me you are in danger heading down the same bad road as the creationists. The probability of the ecosystem of Earth being recreated is an absolutely unknown small fraction of possible "earthlike" recreations of life. Your estimate will still be no better than the worst factor. I suppose one can perhaps identify crucial steps.

I fear I have lost track of the consensus creation mode for the moon...are we still at collisions?
A former colleague of mine (Neil Comins) wrote a book "What if the Moon Didn't Exist ' a while back. Had some interesting stuff.

 

[Buzz Bloom]

It seems to me you are in danger heading down the same bad road as the creationists.

Hi hunch:

I am not trying to convince anyone of any point of view. I was trying to understand what @Jando had in mind by the quote from post #8 which I included in post #9. If you have an interpretation of what this quote implies, I would be interested to see your thoughts.

Regards,
Buzz

 

[hutchphd]

I in no way was trying to impune your intent as proselytizing!
The problem for me with speculations in this area is sort of the problem with normalizing path integrals. There are so many different ways to get from an initial state (no life) to final state (us alive) that comparisons are extraordinarily tricky. They are even more tricky if we allow variation in many parameters (i.e. a different but "similar" solar system) so the process is fraught. That is (my interpretation of) @Jando point.
I do love the subject but I'm not sure I agree this is necessarily the limiting factor.

 

[Lren Zvsm]

Awfully sorry, but all of them. :) The article only talks about this solar system, this Earth and this moon. Whether that has any relevance for other systems, other planets and other moons is completely unknown.

Best evidence indicates that the Moon formed after the Earth was struck by a Mars-sized object. Doesn't that make it less likely that other Earth-sized planets also have moons about the size of ours?

 

[Jando]

Would you also conclude that whether or not the fact (that Earth has life) has any relevance to life on any other planet in the galaxy is also completely unknown?

Hello! (and what an old thread revived)

The fact that Earth has life is certainly relevant because it tells us that life is possible. But then we already knew that. :)

However that alone doesn't tell us anything about life happening elsewhere. It only tells us that it is possible. Whether it has happened elsewhere or may happen elsewhere in the future is an unknown.

 

[Buzz Bloom]

However that alone doesn't tell us anything about life happening elsewhere. It only tells us that it is possible. Whether it has happened elsewhere or may happen elsewhere in the future is an unknown.

Hi Jando:
I am guessing you would likely agree with adding an adverb to the quote above.

However that alone doesn't tell us anything about life happening elsewhere. It only tells us that it is plausibly possible. Whether it has happened elsewhere or may happen elsewhere in the future is an unknown.

Regards,
Buzz

 

[sciFax]

I'm surprised that people expect the Drake equation to be capable of actually predicting some value or other. Surely it should be understood to be simply a back-of-an-envelope didactic tool with which one might gain an appreciation of how difficult it is to predict the occurrence of life in the cosmos.

A better handle on the occurrence of life in the cosmos might be got from investigating the subsurface oceans which may or may not exist in some moons in the solar system.

 

[Buzz Bloom]

I'm surprised that people expect the Drake equation to be capable of actually predicting some value or other.

Hi sciFax:

Drake's equation was produced for a conference in 1961.

https://en.wikipedia.org/wiki/Drake_equation#History​

As I planned the meeting, I realized a few day ahead of time we needed an agenda. And so I wrote down all the things you needed to know to predict how hard it's going to be to detect extraterrestrial life. And looking at them it became pretty evident that if you multiplied all these together, you got a number, N, which is the number of detectable civilizations in our galaxy.​

(Underlining is mine to focus on Drake's intent regarding the equation.)​

I interpret this as Drake making a warning to professional researchers seeking to detect exolife that that task is extremely difficult. When a professional makes guesses at the value (or value range) of the seven variables, it is intended for that person to expect a result showing that the task of searching is very hard. I also believe when an amateur makes such guesses, is should also reveal to them how hard it is to make reasonable guesses.

Regards,
Buzz

 

[sophiecentaur]

I also believe when an amateur makes such guesses, is should also reveal to them how hard it is to make reasonable guesses.

They see the prospect through rose tinted spectacles, imo. It's the same thing with terraforming Mars and starships. But Oh Boy the upset if we ever did receive a message from far away that made sense. Just imagine Trump putting his space force up in orbiting sentry boxes.

 

[Buzz Bloom]

They see the prospect through rose tinted spectacles, imo.

Hi sophie:

In the 1970s I read Oparin's The Origin of Life. In the 1980s, as an amateur without tinted spectacles, I started trying to guess at values for the Drake equation's seven factors. I found it to be impossibly diffficult. In the 1990s I read a book by Christian de Duve, but I am not sure which of his books that was, but there was a lot in it about the RNA world. It was a bit after that I read about the role of the moon in the origin of life, although I do not remember the source.

I apologize for disagreeing with you about the amateurs, also some may be as you describe them.

Regards,
Buzz

 

[sophiecentaur]

I apologize for disagreeing with you about the amateurs, also some may be as you describe them.

Buzz; you seem somewhat offended about my comment but no offence was intended. Rose tinted specs are a great weapon against the world and we all wear them at times. But nothing you have written implies that you had / have a cold rational approach to the topic in hand - or that you acknowledge the implications of the Drake Equation, if you include the present level of knowledge of the values of the variables. Of course you found it impossible to come up with meaningful values on your own. Me too.

I, in my youth, read Erich Von Daniken and there's nothing more rose tinted than what he had to say. He was so convincing that I had actually decided that my Physics teacher probably came from Venus! At least I never challenged him about it. Could have been a great topic of staffroom gossip.

Your mention of Christian de Duve is interesting. Yes, the views of a biochemist would probably be great for establishing the likely timescale of developing life at a location but that only accounts for just one of the variables. It's pretty well established that the presence of the Moon could well have speeded up evolution at some stage. Would the conditions there have been favourable for lunar life to have developed?

The point of my post was that humans actually want life to exist elsewhere and Drake gives a possible way into discussing the subject. There's a kind of paradox there. The most basic forms of life could be in inaccessible locations and the highest developed forms (civilisations etc) would be too far away for communication to be established. Frankly, if people on Earth find it so hard to communicate constructively amongst themselves then is there any great point in expecting things to be easier if we were to pick up TV broadcasts from the Planet Zog? Conversely, would they be interested in the contents of our broadcasts?

 

[Buzz Bloom]

... acknowledge the implications of the Drake Equation, if you include the present level of knowledge of the values of the variables.
...
It's pretty well established that the presence of the Moon could well have speeded up evolution at some stage.

Hi sophie:

I find that the way you think about the issues I discussed to be quite interesting, although I am not confident I understand your view correctly.

Can you give a short summary of what are "the implications of the Drake Equation" based on the current "level of knowledge of the values of the variables"?

Also, your interpretation of the role of the moon is quite different from mine. You seem to see it as making the origin of life happen faster than it would have been without the moon. I see the moon as plausibly likely to have been necessary for life to have come into existence at all.

Regards,
Buzz

 

[sophiecentaur]

current "level of knowledge of the values of the variables"?

We know that the number of extrasolar planets is much more than people even hoped for, up until the 1990s. But now we have become more specific about what the 'Golidilocks' term really means and that there's more to it than just a suitable temperature. Time is very important in this. Using the Earth as our (only reliable) model, we ('they') can establish that, despite the basic life forms (prokaryotic) being around for most of the life of Earth ( probably 3.5 of the 4.5 billion years available) euckaryotic life took another billion or so years to develop. Interestingly, the evidence about Mars is that the usable water probably disappeared well before the possible era of any eukaryotic life - which sort of excludes Mars type planets as a candidate for little green man with radio sets.
I would say that estimates of likely advances in tecknology are better these days - but, otoh, we have less naked optimism about what is actually needed for travel or even communication, both of which involve enormous timescales to achieve (not just the 'c' limit but the possible signalling rate over thousands (millions?)) of light years.
It seems to me that, on one hand, things seem to be getting better, the hurdles are getting further away.
The lifespan for possible tecnichological civilisations is hard to estimate but personally I have no great hopes for more than a few thousand years. Optimists seem to ignore history and reckon that tech will get us out of any problems - rather than get us into countless problems.

Re. the Moon. My take on the Moon is that the existence of tides produced an enormous reason for the move from water to land. But that was a mere few million years ago. What are your ideas for suggesting that prokaryotic life arrived thanks to the presence of the Moon? Something to do with the atmosphere?

 

[Buzz Bloom]

What are your ideas for suggesting that prokaryotic life arrived thanks to the presence of the Moon?

Hi sophie:

The role of the moon as I described it in post #21 has nothing to do with prokaryotic life. It is about the pre- development of the of the first living cell.

I see the moon as plausibly likely to have been necessary for life to have come into existence at all.​

From various sources regarding the idea that the moon played a role related to life existing on Earth is based are a variety of specific situations. The particular single situation that I find most interesting involves something that happened long before the first cell came into existence. This situation involves the development of the chemistry that enabled RNA to act as a rybozyme in the reproduction of itself. I discuss this is some detail in another thread.

https://www.physicsforums.com/threads/novel-idea-on-the-origin-of-life.851106/page-3#post-5369545​

Up until now this phenomenon has not yet been reproduced in a laboratory. However, the following post in another thread may be of some interest related to RNA self reproduction.

https://www.physicsforums.com/threa...-rna-polymerase-ribozyme.882293/#post-5545883​

Regards,
Buzz

 

[sophiecentaur]

the following post in another thread may be of some interest related to RNA self reproduction.

Ah yes. I must have missed that thread at the time. The 28 day cycle, in addition to the solar influence would certainly produced slightly special tidal conditions (plus the even longer times between equinoctial extremes). I think that the later evolution of land animals would easily have been stimulated by the need to survive in tidal pools for long periods.