Thoughts on the Drake Equation

Ray McCarthy said:

We need to start taking steps. At least discovering someone else, even if we can't communicate would seriously motivate the politicians to spend the money on the next step. Really now we are not doing much beyond commercial and military satellites. A tiny amount on Space exploration and research. India did a Mars Mission for $75M.
Look how much ONE nuke powered sub or nuke powered Aircraft carrier costs?

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The obscene amount of money wasted for weapon systems. It's a travesty that we spend so much money on weapons.

Imagine what kinds of exploration would be possible if Nasa had access to the kind of money that defense gets. Who knows ,we might have gotten a manned mission to Mars 15 years ago. Maybe a whole lot more.

BAYLOR said:

You might want also rule out Binary star systems,. Having twin suns even the same if they both yellow would mean double the energy and radiation output and what would orbits be like. Worse if the companion star is white dwarf or a black hole .

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Well, in the case of a binary with one member a collapsed object some rather violent things have happened in its past. But binary systems in general are possibilities, providing that they are either extremely close (and thus have a shared Goldilocks zone) or at least as far apart as Saturn is from the Sun because reasonably stable orbits could exist around either. The Alpha Centauri system would be suitable; a similar system with the B star being in a less eccentric orbit would be even better.

Regarding Mars and Venus, I've heard an opinion that if the two planets were swapped in position Sol system would have three habitable planets. Mars, somewhat warmed up, would be habitable and Venus twice as far from the Sun probably would be as well - or at least it would have a chance.

Mirannan said:

Well, in the case of a binary with one member a collapsed object some rather violent things have happened in its past. But binary systems in general are possibilities, providing that they are either extremely close (and thus have a shared Goldilocks zone) or at least as far apart as Saturn is from the Sun because reasonably stable orbits could exist around either. The Alpha Centauri system would be suitable; a similar system with the B star being in a less eccentric orbit would be even better.

Regarding Mars and Venus, I've heard an opinion that if the two planets were swapped in position Sol system would have three habitable planets. Mars, somewhat warmed up, would be habitable and Venus twice as far from the Sun probably would be as well - or at least it would have a chance.

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Alpha Centauri A Sun is a yellow sun like our only 20 percent larger, Alpha Centuri B is an orange star slightly smaller and slightly less radiant then our Sun . Proxima Centauri is red dwarf . That system might have possibilities for habitation.


Venus in Mars orbit , I could be wrong here but wouldn't it be Ice age conditions? If so it probably habitable at the equator regions . Venus would still need a large moon to steady its axis to have stable seasons. Mars in Venus orbit could be like Death Valley only much much hotter and probably not might be habitable on the surface. I could definitely be wrong here as well.

Ray McCarthy said:

That's an assumption. If in fact if the life we have is the only way it works, then there is no reason to suppose all life came from one kind of life. There is actually no historic evidence for a single origin.

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Less of an assumption than the opposite. As far as I know all life on Earth shares a significant part of it's DNA. We, for example, share around 7% of our DNA with bacteria. The chances of that happening with independent genesis is vanishingly small. As far as I am aware the accepted scientific view is currently that all living organisms have a single common ancestor.

That's true. A hilarious attempt was recently made to prove "Life 2.0" here on Earth, something to do with arsenic metabolic systems or owt... got laughed out of court.

Vertigo said:

accepted scientific view is currently that all living organisms have a single common ancestor

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But it's purely a consensus based on the assumption that any commonality of DNA means a single origin. It's a circular argument not actually based on evidence. A supposition.

Till we can examine life elsewhere, we can't tell. There are no preserved records of early enough life, nor any method to prove or disprove the any commonality of DNA = common origin theory.

I'm not saying I believe all life here hasn't a common origin, but there is a difference between supposition and real evidence.

Ray, you are saying more or less what I did. But to clarify:

If ET life in the Solar System turns out to have identical basic chemistry (DNA/RNA with the same nucleic acid bases, genetic code and amino acids in use) as ours then it means that either (a) that's the only way life can work or (b) all life in the Sol system comes from a common origin on one of the planets. There is no clear proof either way, although I don't see how biochemistry with opposite chirality from ours and no other differences couldn't work - for example.

If, however, ET life (in vaguely Earthlike places such as Mars or Europa's ocean) has different basic chemistry from ours then that certainly does prove something. And that something is that life is extremely easy to get started.

Incidentally, some interesting although very preliminary work has been done on the formation of cell membrane-like structures at Titan temperatures in non-polar solvents like liquid methane, with the basic chemicals being polar molecules such as acrylonitrile - which happens to be detectable in Titan's atmosphere so it obviously can form somehow under Titan conditions.

Which means a rather weak hint that life in conditions very unlike those of Earth might, just might, be possible. It is worth noting that doing chemistry with liquid methane is very difficult on Earth. Apart from the obvious difficulties with cryogenic chemistry, there is also a serious fire and/or explosion risk.

Mirannan said:

very preliminary work has been done on the formation of cell membrane-like structures at Titan temperatures in non-polar solvents like liquid methane, with the basic chemicals being polar molecules such as acrylonitrile

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Though the researchers are ONLY demonstrating a membrane and admit they are not biologist.

Interesting, but a long way from biology or life. Certainly Ammonia rather than water has been postulated. But as with this only a few isolated aspects have been demonstrated.

The chirality thing is very odd indeed. You'd expect the opposite shape but otherwise same formula organic chemicals to have the same properties. But some don't. Perhaps because everything, like Alice through the Looking glass needs reversed. An oddity too is that synthesised compounds (sugars?) often seem to be opposite handed. You can make a Kerr cell with a sugar solution and detect the chirality (handedness) with polarised light.

Do Clouds naturally polarise light in one aspect? A sunstone is a primitive polariser and I think helps to spot sun's location when sky overcast?
https://en.wikipedia.org/wiki/Sunstone_(medieval)

If clouded skies are ALWAYS a particular polarisation, then for photosynthesis there is advantage of same "handedness" (chirality). Then everything is going to have chirality to match the handedness of that first photosynth cell. Otherwise enzymes etc don't work so well, sugar won't be as sweet etc...

Maybe all completely nonsense, just thinking about it as I type. It's odd.

Plants use Xanthophyll (not just Chlorophyll), apparently we have it in our eyes too

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

Ray - I did look into the chirality thing and it appears that there are two ways of defining chirality for a particular molecule, one of which is more fundamental than the other. They are distinguished in the literature by using lower or upper case letters, I believe.

Essentially, just about all biological molecules are interconvertible. By some accident of stereochemistry, if one follows the long chain of reactions to make (say) glucose from an l-amino acid then that glucose is in the d form. For further explanations, it turns out Wikipedia explains it all quite well:

https://en.wikipedia.org/wiki/Chirality_(chemistry)

I did organic chemistry back in the Plasticine age.
It's fascinating stuff.

I accept what you say Ray, and I know you are not rejecting the single origin idea, but I think he argument is somewhat stronger than you suggest. It's not like it's just the chemistry that is the same it is the actual gene sequences that are the same and that is a level of complexity that it is hard to imagine being duplicated in any other way. But beyond that I'll bow out as my knowledge of organic chemistry goes no further than what I have learnt from documentaries etc

But I'd still go back to my original point that the conditions that have produced higher life forms on Earth are far far more complex than just being in the habitable zone and having water. Which is why I tend to think the Drake equation overly optimistic. The single origin idea is really just one of those factors though if correct a pretty major one. But I can't see how we'll ever really know that one for certain.

Vertigo said:

the conditions that have produced higher life forms on Earth are far far more complex than just being in the habitable zone and having water.

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Very much agree - it's limiting ourselves to the familiar, rather than possible.

Ray McCarthy said:

Till we can examine life elsewhere, we can't tell. There are no preserved records of early enough life, nor any method to prove or disprove the any commonality of DNA = common origin theory.

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There are a lot of scientists who agree that abiogenesis on earth is problematic - Fred Hoyle and Francis Crick both calculated that statistically it is improbable. There are further concerns about just how quickly life actually appeared for it to have been a random event, with the additional problem that all the ingredients required for life to develop might not have been available. The number of objections appears fairly significant.

Am currently reading about this very topic in "Evolution of life from space" by Chandra Wickramasinghe of Cardiff University - fascinating reading.

Brian Turner said:

There are further concerns about just how quickly life actually appeared for it to have been a random event, with the additional problem that all the ingredients required for life to develop might not have been available. The number of objections appears fairly significant.

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These to my mind are minor, or even irrelevant concerns. Even with people like Andrew Knoll around, we still don't know enough about the very early conditions to say anything with conviction. Imo, Fred and the rest have vivid imaginations. Just a personal opinion.

I think until we have some idea how frequently life evolves it is just to hard to make any sensible conclusions. If life happens easily, the chances of cvilizations arrising is good, if life is incredibly unlikely to evolve then intelligent life may be unbelievably rare no matter how many goldilocks planets there are.

True. One reason I want to live to see the results of the Europa expedition!