# If we live in a multiverse, what percentage of universes will be capable of harboring life **URL:** \ **Category:** Factual Questions\ **Created:** [April 17, 2017, 6:41pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651 "2017-04-17T18:41:47Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [April 18, 2017, 5:21pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/41 "2017-04-18T17:21:53Z")
> [@Chronos](#): > > I can envision, for instance, a form of life not dependent on any form of matter at all, and composed entirely of gravitational waves. Only if you are stupendously lazy\*. Gravity waves, like all light waves, pass through each other without interacting. Life actually requires a number of far more specific characteristics to work : a. It requires something able to catalyze something else into a piece of the same something. Gravity waves are right out because of the lack of interaction. b. Complex life requires a pool of these self-catalyzing devices to be present in the same place and time such that they can compete with one another. A cloud of gas or small specs of nanometer scale dust expanding forever into the void cannot become complex life. c. Complex life requires the environment to be stable enough that the _information_ - the catalyzing “something” - is not destroyed faster than it can be created. This also means there must be an energy gradient to create information. Thus, a ball of matter at a smidgen over zero kelvin can’t create life, no energy gradient. The hot gas cloud of our sun doesn’t support life starting there, too much disruption for it to ever evolve. And like 10 others, point is, gravity waves fail the first test and many other tests will fail out a great many other possibilities. \*Ok, I apologize for being harsh, but I don’t see how you could have “envisioned” this working. You would have needed to think of a way for a gravity wave - which requires mass to be created - to catalyze the creation of an identical gravity wave to itself, or a sub-component of itself that can be assembled into itself. That’s the _first_ step towards life. The very first one. ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [April 18, 2017, 6:08pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/42 "2017-04-18T18:08:49Z")
> [@SamuelA](#): > > Only if you are stupendously lazy\*. Gravity waves, like all light waves, pass through each other without interacting. Life actually requires a number of far more specific characteristics to work : > > a. It requires something able to catalyze something else into a piece of the same something. Gravity waves are right out because of the lack of interaction. > > b. Complex life requires a pool of these self-catalyzing devices to be present in the same place and time such that they can compete with one another. A cloud of gas or small specs of nanometer scale dust expanding forever into the void cannot become complex life. > > c. Complex life requires the environment to be stable enough that the _information_ - the catalyzing “something” - is not destroyed faster than it can be created. This also means there must be an energy gradient to create information. Thus, a ball of matter at a smidgen over zero kelvin can’t create life, no energy gradient. The hot gas cloud of our sun doesn’t support life starting there, too much disruption for it to ever evolve. > > And like 10 others, point is, gravity waves fail the first test and many other tests will fail out a great many other possibilities. > > \*Ok, I apologize for being harsh, but I don’t see how you could have “envisioned” this working. You would have needed to think of a way for a gravity wave - which requires mass to be created - to catalyze the creation of an identical gravity wave to itself, or a sub-component of itself that can be assembled into itself. That’s the _first_ step towards life. The very first one. I have to admit it would be difficult to imagine how gravitational waves could form the necessary structures that we might recognize as being something akin to light, but they are non-linear (i.e. gravitational waves interact with gravitational waves unlike em waves) ---
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [April 18, 2017, 6:12pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/43 "2017-04-18T18:12:12Z")
> [@Asympotically\_fat](#): > > I have to admit it would be difficult to imagine how gravitational waves could form the necessary structures that we might recognize as being something akin to light, but they are non-linear (i.e. gravitational waves interact with gravitational waves unlike em waves) Ok, I stand corrected on that point. You then do have to posit how they can catalyze creation of similar waves, and how the system deals with perpetual energy loss. If waves are ever expanding and ever growing weaker, you cannot have “something” creating itself - the fundamental definition of what life is. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [April 18, 2017, 6:23pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/44 "2017-04-18T18:23:11Z")
Is there any conceivable way that a self-aware being could arise in any universe except through natural selection? Thus, to restate **SamuelA** ’s requirements slightly differently: in addition to suffiient basic stability, we need a mechanism for reproduction and heredity (variation is also required, but that’s almost inevitable). The actual mechanisms for reproduction and heredity could be beyond our wildest imagination, but I think they must exist in some form. What alternative is there? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 18, 2017, 8:05pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/45 "2017-04-18T20:05:47Z")
> [@](#): > > Quoth **SamuelA** : > > \*Ok, I apologize for being harsh, but I don’t see how you could have “envisioned” this working. You would have needed to think of a way for a gravity wave - which requires mass to be created - to catalyze the creation of an identical gravity wave to itself, or a sub-component of itself that can be assembled into itself. That’s the first step towards life. The very first one. Life as we know it is based on atoms. Is there any way for an atom to catalyze the creation of an identical atom? It’s not the gravitational waves themselves which need to be reproduced; it’s the patterns in them. ---
**Author:** ![Sage\_Rat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sage_rat/32/399_2.png) [@Sage\_Rat](https://boards.straightdope.com/u/Sage_Rat)\ **Post date:** [April 18, 2017, 8:42pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/46 "2017-04-18T20:42:48Z")
The safest guess would be that our universe is “average”. That might be wrong, but it’s the safest assumption for a sample size of 1. So the best guess would be something over 50%. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [April 18, 2017, 8:45pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/47 "2017-04-18T20:45:00Z")
> [@Chronos](#): > > …I can also envision a form of life based on strong-force “chemistry” instead of electromagnetic, which could only have existed in the first few minutes of our Universe’s history… The hard SF novel “Dragon’s Egg” by Robert L Forward describes the evolution of life (in our universe) in a strong-force environment on the surface of a neutron star. ---
**Author:** ![MacLir](https://avatars.discourse-cdn.com/v4/letter/m/9e8a1a/32.png) [@MacLir](https://boards.straightdope.com/u/MacLir)\ **Post date:** [April 19, 2017, 2:48pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/48 "2017-04-19T14:48:11Z")
> [@Stranger\_On\_A\_Train](#): > > We naively assume that life would be chemical in nature and similar to our own fundamental construction of proteins and cellular organization which is reasonable given the lack of other examples but exclusionary to other possibilities of self-reproducing regulated net thermodynamic systems with large scale organization which could, depending on the qualifications you apply, be considered as life. > Stranger “Meat. They’re made of meat.” 😃 ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [April 19, 2017, 8:58pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/49 "2017-04-19T20:58:31Z")
> [@Mijin](#): > > Well I’ve never been clear on that aspect. But if it’s as you say then ISTM the multiverse doesn’t really help with the issue of why all the constants in our universe appear fine-tuned. Because it just kicks it further down the road: considering the infinity of multiverses that could not harbour life, what good fortune this is the one that exists. It’s amazing that we exist in a universe that is able for us to exist and not in a universe that we can’t exist in. So there are a bajillion universes where any kind of life like us could exist. Well, we don’t exist there, so speculating why we exist where we exist is like speculating why fish swim in water rather than fly through the air. (Except for flying fish - shush, don’t bring up silly exceptions.) > [@Mijin](#): > > As I mentioned in my previous post, I’m not sure that the fine-tuning “problem” is really a problem that needs or could be solved. However, I also don’t find the anthropic principle compelling either. The fine-tuning “problem” is that we developed in a universe in which we could develop. That seems hardly something that needs explaining. Without knowing what other possibilities there are, it’s meaningless to try to evaluate the likelihood that we have arisen at all. The likelihood is now 1 - we’re here. Asking why the universe exists at all is one thing. Asking why our universe is the way it is requires mostly speculation and very little actual science. It’s a guessing game with no answer book to check and see who is right. > [@](#): > > A pretty sizeable chunk of science is investigating and understanding phenomena that human life depends on. > Now it’s true that why this constant is 4.3 instead of 4.2 is a different kind of question to “How does water dissolve so many things?”, say. It’s a Why question vs a How question, for a start. Maybe it’s a why question instead of a how question because we don’t yet have enough foundational information to make it a how question. Suppose there are some constraints that we haven’t yet identified. Those would be like the chemistry rules that make water a dissolver. > [@Riemann](#): > > The actual mechanisms for reproduction and heredity could be beyond our wildest imagination, but I think they must exist in some form. What alternative is there? Well, proponents of the fine-tuning argument say “God”, not that I think that’s a scientific explanation. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [April 19, 2017, 9:25pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/50 "2017-04-19T21:25:03Z")
> [@Irishman](#): > > …The fine-tuning “problem” is that we developed in a universe in which we could develop. That seems hardly something that needs explaining… That is not the fine-tuning problem. See e.g. the account from Andre Linde that I linked at post#36, or read the rest of this thread. The fine-tuning problem arises from the fact that the only viable models that we have for the universe do not constrain parameter values (and we can’t find one that does, despite decades of trying); all parameter values seem to be possible, and the vast majority are not consistent with life. > [@Irishman](#): > > …Well, proponents of the fine-tuning argument say “God”, not that I think that’s a scientific explanation. The fine-tuning argument for God is little more than “we don’t understand X, therefore Jeebus”. But don’t confuse this with the _real_ fine-tuning problem in physics. When physicists call this a “problem” it does not imply that it’s paradoxical or insoluble of that we must turn to God. It’s just a problem in the sense that we don’t know which of several possible naturalistic explanations is the correct resolution. One of the possible resolutions is the multiverse and the anthropic principle. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [April 21, 2017, 1:58pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/51 "2017-04-21T13:58:33Z")
Scientific American had an article pointing out that the fine-tuning argument overlooks that there might be _combinations_ of alternate constants that could allow for life to exist. ---
**Author:** ![SamuelA](https://avatars.discourse-cdn.com/v4/letter/s/c77e96/32.png) [@SamuelA](https://boards.straightdope.com/u/SamuelA)\ **Post date:** [April 21, 2017, 3:52pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/52 "2017-04-21T15:52:27Z")
> [@Chronos](#): > > Life as we know it is based on atoms. Is there any way for an atom to catalyze the creation of an identical atom? It’s not the gravitational waves themselves which need to be reproduced; it’s the patterns in them. For the purposes of chemical reactions, different atoms of the same element are indistinguishable, and this is nearly always true even in the case of differing isotopes. Only the outer electron shell matters in most cases. I guess when I said “identical” I meant “Functionally indistinguishable”. So by what mechanism can gravity ways accomplish, this even in theory? Give the simplest case you can think of. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 21, 2017, 4:57pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/53 "2017-04-21T16:57:06Z")
All gravitons are also indistinguishable. What you would have would be a Universe entirely filled with gravitational waves. Each wave would pass through any given region at c, and quickly leave for parts unknown. But new gravitational waves would also be entering the region at the same rate, so there would still always be gravitational waves present. Meanwhile, the waves would be interacting with each other, and patterns would emerge within the waves. These patterns would also be moving, but _not_ necessarily at c: It’s possible, for instance, to have sound waves propagating through a gas of massless photons, and those sound waves travel at 1/3 c. Now, I realize that there’s a heck of a big step from “self-interacting patterns which propagate at less than c” to “life”. But then, there’s a heck of a big step to our kind of life, too. And once you have the self-interacting patterns, it’s at least possible. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [April 21, 2017, 6:32pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/54 "2017-04-21T18:32:45Z")
> [@Lumpy](#): > > Scientific American had an article pointing out that the fine-tuning argument overlooks that there might be _combinations_ of alternate constants that could allow for life to exist. Once again, to be clear, I don’t think physicists would use the term fine-tuning _argument_ for anything. That expression tends to be associated with the “we can’t explain this, therefore God” crowd. There is a fine-tuning _problem_ in cosmology. But that problem does not rest on excluding alternate combinations of parameter values (perhaps there are very many such combinations) that might allow for “life” in the broadest sense. The question is what _proportion_ of parameter values have this property? And if string theory’s lack of constraint on parameter values is correct, it seems to be true that the overwhelming _majority_ of combinations of parameter values are inconsistent with life. Hence the multiverse idea. Or, if ours is the only universe, the need for an explanation for why our apparently “lucky” set of values occurred - perhaps some other as-yet unknown model. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [April 21, 2017, 9:25pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/55 "2017-04-21T21:25:05Z")
> [@Riemann](#): > > But don’t confuse this with the _real_ fine-tuning problem in physics. When physicists call this a “problem” it does not imply that it’s paradoxical or insoluble of that we must turn to God. It’s just a problem in the sense that we don’t know which of several possible naturalistic explanations is the correct resolution. One of the possible resolutions is the multiverse and the anthropic principle. Okay, so what you’re saying is that in physics, it’s a problem of why is the universe the way it is rather than a question of why are we here. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [April 21, 2017, 10:02pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/56 "2017-04-21T22:02:24Z")
> [@Chronos](#): > > All gravitons are also indistinguishable. Photons have wavelength and spin angular momentum which can be used to distinguish them a bit. Gravitons don’t have these properties or are you excluding such properties in terms of distinguishability? ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [April 21, 2017, 10:09pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/57 "2017-04-21T22:09:50Z")
> [@Irishman](#): > > Okay, so what you’re saying is that in physics, it’s a problem of why is the universe the way it is rather than a question of why are we here. I’m not quite sure what distinction you are drawing. Our universe has a set of parameter values that allow life to exist. But we have no model for making universes that constrains the parameters; our best models (our _only_ models) allow a vast range of possible parameter values, the overwhelming majority of which are _not_ compatible with life. Under these circumstances, the anthropic principle is sufficient to explain why we are sitting here looking at a universe compatible with life, but only if universes with all possible parameter values do actually come into existence. But the multiverse hypothesis has a deeper foundation than just this point, it has a well-developed theoretical basis - it arises naturally from these models of inflation & string theory. (Without any _empirical_ support whatsoever, of course.) > **[Andrei Linde | Inflationary multiverse and eternal chaotic inflation](https://en.wikipedia.org/wiki/Andrei_Linde#Inflationary_multiverse_and_eternal_chaotic_inflation)** > > Perhaps the most far-reaching prediction made by Linde was related to what is now called the theory of inflationary multiverse, or string theory landscape. In 1982-1983, Steinhardt, Linde and Alexander Vilenkin realized that exponential expansion in the new inflation scenario, once it begins, continues without end in some parts of the universe. On the basis of this scenario, Linde proposed a model of a self-reproducing inflationary universe consisting of different parts. These parts are exponenti... > **[Multiverse](https://en.wikipedia.org/wiki/Multiverse)** > > The multiverse is the hypothetical set of all universes.\[a\] Together, these universes are presumed to comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them. The different universes within the multiverse are called "parallel universes", "flat universes", "other universes", "alternate universes", "multiple universes", "plane universes", "parent and child universes", "many universes", or "many worlds". One... ---
**Author:** ![Snarky\_Kong](https://avatars.discourse-cdn.com/v4/letter/s/a183cd/32.png) [@Snarky\_Kong](https://boards.straightdope.com/u/Snarky_Kong)\ **Post date:** [April 21, 2017, 10:12pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/58 "2017-04-21T22:12:24Z")
> [@Tranquilis](#): > > If we live in a multiverse, the question is essentially meaningless - How can you take a percentage of infinity? Easily. I flip a fair coin infinite times. 50% of the time it will be heads. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [April 21, 2017, 11:11pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/59 "2017-04-21T23:11:09Z")
Exactly so. In math, it’s called “probability density,” which is just a fancy way of saying that, even among infinite sets, some subsets are “bigger” than others. If you rolled a pair of dice an infinite number of times…yes, you’d get an infinite number of 7s and an infinite number of 2s (snake-eyes.) Nevertheless, there will be six times as many 7s as there are 2s, or, perhaps more accurately, the distribution of the 7s is six times as dense as the distribution of 2s. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [April 21, 2017, 11:34pm UTC](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651/60 "2017-04-21T23:34:26Z")
Again, it’s _sometimes_ possible to speak meaningfully of probabilities in infinite sets. Not always, and not necessarily here. [Previous page](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651.md?page=2) [Next page](https://boards.straightdope.com/t/if-we-live-in-a-multiverse-what-percentage-of-universes-will-be-capable-of-harboring-life/784651.md?page=4)