Thread: Is there a minimum mass to the universe, according to the anthropic principle?

1. I always had difficulty with the Drake equation in that if we consider what we know about our evolution, we can see many historical points where our evolution seems unlikely, so the allocation of probabilities is arbitrary. We have seen discussion about how easy it would be to detect alien intelligence on a star let alone another galaxy, and we can only guess at our intelligent time window. So the assumption that there must be others or that there cannot be others are equally valid and untestable by probability theory. It is basically trying to force maths onto a faith based belief.

As we consider single celled life and its progress to big brained species, (plus its ongoing competition) the probabilities do seem to me to decline rapidly, requiring in our case multiple extinctions, tectonic movement and climate changes.

So i did wonder about those heavy elements and ratios within our planet, but i don’t know enough about how many star cycles are needed. If the big bang first stage is just protons, can we not draw a bubble around a volume and allow it to evolve to EArthlike?

2. Originally Posted by profloater
I always had difficulty with the Drake equation in that if we consider what we know about our evolution, we can see many historical points where our evolution seems unlikely, so the allocation of probabilities is arbitrary. We have seen discussion about how easy it would be to detect alien intelligence on a star let alone another galaxy, and we can only guess at our intelligent time window. So the assumption that there must be others or that there cannot be others are equally valid and untestable by probability theory. It is basically trying to force maths onto a faith based belief.

As we consider single celled life and its progress to big brained species, (plus its ongoing competition) the probabilities do seem to me to decline rapidly, requiring in our case multiple extinctions, tectonic movement and climate changes.

So i did wonder about those heavy elements and ratios within our planet, but i don’t know enough about how many star cycles are needed. If the big bang first stage is just protons, can we not draw a bubble around a volume and allow it to evolve to EArthlike?
My bold. If it is just protons, the electrostatic repulsion would blow the whole thing to kingdom come. We need an equal number of electrons to neutralize it.

3. Originally Posted by Hornblower
My bold. If it is just protons, the electrostatic repulsion would blow the whole thing to kingdom come. We need an equal number of electrons to neutralize it.
It’s a figure of speech, as you know the point here is the generation of larger atoms to make planets for life. Do we need to start with quarks? The big bang is not the point, unless it couldhave been a small bang and still made planets.

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Originally Posted by profloater
I always had difficulty with the Drake equation in that if we consider what we know about our evolution, we can see many historical points where our evolution seems unlikely, so the allocation of probabilities is arbitrary. We have seen discussion about how easy it would be to detect alien intelligence on a star let alone another galaxy, and we can only guess at our intelligent time window. So the assumption that there must be others or that there cannot be others are equally valid and untestable by probability theory.
That's all true, but the key point is, you don't need anything like good accuracy to still have a useful result. You should think of all the probabilities in the Drake equation in logarithmic space, where factors of 10 of uncertainty become order-unity windows. Then your question is basically, should there be intelligent life "now" in our solar neighborhood (some 103 stars)? How about in our galaxy (1011 stars)? How about the observable universe (1022 stars)? You see how you don't need tight estimates to answer those questions, you need very loose estimates!

Also, when reasoning anthropically, you don't care if the intelligent life exists "now", so you don't even have that most uncertain of all terms, the longevity of intelligence. That unknown factor doesn't appear in any relative probabilities, so doesn't play into anthropic thinking at all, it's only if there is ever intelligence that matters in the relative counting. So for that version of the "Drake equation," we know that in a galaxy you have some 108 candidate planets for life, and only a small fraction will actually get life. That is still quite uncertain, but I would tend to think in the range 103 to 107. Then the only remaining issue is, how many ever get intelligent life (intelligent enough to do science and ask philosophical questions about our place in the grand scheme), and that's quite a doozy. That might knock it down quite a bit, though I don't really feel like any less than about the range 1 to 106. So there you have it, you might need a whole galaxy to have intelligent life, but even if you don't need that much, you certainly need a whole lot of stars, so let's say at least a dwarf galaxy. If you need that much, you will certainly have all the nucleosynthesis you could ask for, that's the least of your concerns!

Also, even if we are somewhat pessimistic and say you need a whole galaxy to expect intelligent life even once, then you still end up concluding our universe is way, way larger than it needed to be to house intelligence. That right there pretty much destroys the prospects of ever using anthropic arguments to justify or explain the size of our universe, because such an argument would always have to look like our universe is in a kind of "sweet spot" between the number of such universes, and the number of intelligences within such a universe. But that kind of sweet spot is never going to happen unless the size of our universe is rather generic in the entire distribution, because the expected number of intelligences is proportional to universe size, and that's not going to produce a peak at a large number of intelligences unless our size is generic. But if our size is typical, then you don't need anthropic thinking in the first place, even non-anthropic arguments involving only one universe will start from that same assumption. So no help from anthropics, it seems that typical universes are strangely large and we don't have any way of understanding why that is!
Last edited by Ken G; 2019-Oct-15 at 12:37 AM.

5. Originally Posted by Ken G
That's all true, but the key point is, you don't need anything like good accuracy to still have a useful result. You should think of all the probabilities in the Drake equation in logarithmic space, where factors of 10 of uncertainty become order-unity windows. Then your question is basically, should there be intelligent life "now" in our solar neighborhood (some 103 stars)? How about in our galaxy (1011 stars)? How about the observable universe (1022 stars)? You see how you don't need tight estimates to answer those questions, you need very loose estimates!

Also, when reasoning anthropically, you don't care if the intelligent life exists "now", so you don't even have that most uncertain of all terms, the longevity of intelligence. That unknown factor doesn't appear in any relative probabilities, so doesn't play into anthropic thinking at all, it's only if there is ever intelligence that matters in the relative counting. So for that version of the "Drake equation," we know that in a galaxy you have some 108 candidate planets for life, and only a small fraction will actually get life. That is still quite uncertain, but I would tend to think in the range 103 to 107. Then the only remaining issue is, how many ever get intelligent life (intelligent enough to do science and ask philosophical questions about our place in the grand scheme), and that's quite a doozy. That might knock it down quite a bit, though I don't really feel like any less than about the range 1 to 106. So there you have it, you might need a whole galaxy to have intelligent life, but even if you don't need that much, you certainly need a whole lot of stars, so let's say at least a dwarf galaxy. If you need that much, you will certainly have all the nucleosynthesis you could ask for, that's the least of your concerns!

Also, even if we are somewhat pessimistic and say you need a whole galaxy to expect intelligent life even once, then you still end up concluding our universe is way, way larger than it needed to be to house intelligence. That right there pretty much destroys the prospects of ever using anthropic arguments to justify or explain the size of our universe, because such an argument would always have to look like our universe is in a kind of "sweet spot" between the number of such universes, and the number of intelligences within such a universe. But that kind of sweet spot is never going to happen unless the size of our universe is rather generic in the entire distribution, because the expected number of intelligences is proportional to universe size, and that's not going to produce a peak at a large number of intelligences unless our size is generic. But if our size is typical, then you don't need anthropic thinking in the first place, even non-anthropic arguments involving only one universe will start from that same assumption. So no help from anthropics, it seems that typical universes are strangely large and we don't have any way of understanding why that is!
I like all those arguments, But, if it is true that any two intelligent life forms are very unlikely to ever communicate, the absolute size becomes irrelevant. If to plaY devil’s advocate, there is an organising principle to the universe among possible universes, then the odds suggest there is a separation of variables to protect the universe from the high probability of conflict. Is that stretching the anthropic philosophy too far?

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Originally Posted by parallaxicality
All the anthropic principle says is that we can exist in a universe this massive. Not that we have to. The range of possible alternatives may be very large, or very small.
Yes but why would the universe go to all this trouble if it was not needed? This is the only "real" universe, all others are virtual.
Would not the lower energy universes be much more likely, if they were sufficient?

7. That's like an ant asking, why is there so much world beyond this jungle? The world (or universe) isn't made for us. It just so happens to be capable of having us in it.

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Originally Posted by profloater
I like all those arguments, But, if it is true that any two intelligent life forms are very unlikely to ever communicate, the absolute size becomes irrelevant. If to plaY devil’s advocate, there is an organising principle to the universe among possible universes, then the odds suggest there is a separation of variables to protect the universe from the high probability of conflict. Is that stretching the anthropic philosophy too far?
I think you're right that the way the universe works, there's a low probability of conflict. As to whether or that that could be "explained" anthropically, you'd have to hold that conflict is fundamentally bad for the propagation of intelligences. You are then trying to anthropically "explain" the Fermi paradox by saying that universes that do not make it impossibly difficult for intelligent species to conflict with each other suffer mass extinctions of their intelligent species and so end up with less "anthropic weight" than do universes like ours. But there's a lot of assumptions in there, because conflict might not matter if it doesn't hold back the "winner", and some interactions could be beneficial (sharing breakthroughs, trading commodities, etc.)

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Originally Posted by parallaxicality
That's like an ant asking, why is there so much world beyond this jungle? The world (or universe) isn't made for us. It just so happens to be capable of having us in it.
Well actually that is a good argument for what I am saying.

The ant needs there to be a world beyond the jungle. It needs an Earth-size planet orbiting a suitable star. An ant won't be aware of it, but it needs a solar system.

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Originally Posted by parallaxicality
That's like an ant asking, why is there so much world beyond this jungle? The world (or universe) isn't made for us. It just so happens to be capable of having us in it.
But the crux of anthropic thinking, as a scientific principle, is that the properties of our universe are the most likely ones for intelligence to find itself in. So you could look at all the jungles in the world, and ask, are most ants found in jungles that are barely large enough to support ants, or are most found in jungles much larger than an ant colony really needs? I'm arguing that what you should expect to find is that most ants live in jungles of "generic" size, meaning that the question of how big are jungles usually, and how big are jungles that a random ant is likely to live in, are more or less the same question. Whenever that is the case, "ant-hropic" thinking is of no value for understanding why ants find themselves in the jungles they do-- instead you'd have to know something about jungles themselves.

11. Originally Posted by Ken G
But the crux of anthropic thinking, as a scientific principle, is that the properties of our universe are the most likely ones for intelligence to find itself in. So you could look at all the jungles in the world, and ask, are most ants found in jungles that are barely large enough to support ants, or are most found in jungles much larger than an ant colony really needs? I'm arguing that what you should expect to find is that most ants live in jungles of "generic" size, meaning that the question of how big are jungles usually, and how big are jungles that a random ant is likely to live in, are more or less the same question. Whenever that is the case, "ant-hropic" thinking is of no value for understanding why ants find themselves in the jungles they do-- instead you'd have to know something about jungles themselves.
Ant-thropic, I love that ! I feel our immediate past in the ice age was a change challenge that favoured big brain ability to imagine better outcomes. Sharks had no such pressure and seem to be the same over millions of years. What that means is that we need a planet, OK, but to evolve intelligence we need tough challenges in a suitable sequence. I suppose our sequence has a low probability so ergo we need lots of planet systems to make us happen. The sequence has to be tough but not fatal to our rapidly evolving species, so the one we had so far is actually very unusual as planets go. Having evolved intelligence, the general view is that we are well endowed for future challenges, but I hope we don’t test that too rigourously!

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Originally Posted by profloater
Ant-thropic, I love that !
That's probably the last time parallaxicality will us an ant metaphor!
I suppose our sequence has a low probability so ergo we need lots of planet systems to make us happen. The sequence has to be tough but not fatal to our rapidly evolving species, so the one we had so far is actually very unusual as planets go.
I agree, going a long time without anything really awful happening is probably quite rare, much rarer than having challenges-- the latter is probably pretty common.
Having evolved intelligence, the general view is that we are well endowed for future challenges, but I hope we don’t test that too rigourously!
There's also the possibility that intelligence is great in the short run, but runs into problems in the long haul even without anything happening. Intelligence allows us to save our successes and pass them on to future generations with almost no degradation, but that kind of power can also be misused. It has been argued that Cro Magnon intelligence led to the extinction of the Neanderthals, and also the extinction of a number of other species. If it is a natural consequence of intelligence to extinct competitors, it may also be a longer-range consequence to extinct itself. The ability to extinct ourselves has never been part of our evolutionary history until quite recently, we really don't know what impact that has on the longevity of intelligence!

Another possibility is that intelligence is a spandrel that has not played any significant role in our overall survival as a species, only to our spatial propagation. After all, there are many unintelligent species that have set much greater longevity records than any we've yet approached. Moreover, it appears that every 50-100 million years something happens to our Earth that only a few species can survive (asteroid hits or drastic seismic/volcanic activity), and I'm not sure we're one of them.

13. Originally Posted by Ken G
Whenever that is the case, "ant-hropic" thinking is of no value for understanding why ants find themselves in the jungles they do...
I though this was amusing enough that I had to respond and say so.

14. Yes indeed. Intelligence does not over-ride the animal emotional drives, it just adds terrible efficiency. It encourages over population just as surely as abundance, while accelerating the competitive instincts. I fear we really need those severe challenges for our own lomg term improvement. A natural corollary of the same anthropic principle is the invention of mechanisms to reduce risk so space probes are logical and potentially longer lived. in the end one Drake probe will encounter another to fix the debate.Perhaps.

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Originally Posted by Grey
I though this was amusing enough that I had to respond and say so.
It was the first time I've seen ants used in an anthropic metaphor, so I had to seize an opportunity that may not come again! Maybe the closest thing is that they often use anthropic thinking to try to justify fine-tuning in the physical constants, so we could call that effort "constant-hropic" thinking. I'm going to have to claim the copyright on that one!

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