Can a Living Creature Be as Big as a Galaxy? | Hacker News Reader

Can a Living Creature Be as Big as a Galaxy?

nautil.us

269 pointsdnetesn189 comments

The question is not correctly formed: what we really want to know is if there are life-like beings that could operate on a totally different scale than ours (both time and size wise, including viruses and whales here). Self centered thinking, i.e. restricting our inquiry to only include protein-based lifeforms or other qualities required on our scale obviously prevents us from having the required open minded mindset.

states, companies, religious communities, planets as whole ecosystems can all be construed as "single being"s.

Similarly fire ant colonies could be considered the same. https://youtu.be/NpiDADw5Omw

There are more bacterial cells in your body than there are human cells. Where exactly do you draw the line between what constitutes "you."

A zoo is still a zoo if there aren't any animals in it, but it wouldn't stay in business very long. No matter how important the animals are to the long-term viability of the zoo, they are not the zoo.

My gut bacteria may be vital to my survival, but they are not me. I don't find placing that line to be difficult at all.

The only part of the flesh which is "you" is the nervous system. Everything else can be hacked off or replaced without a loss of identity.

So if somebody has a limb amputation, losing a lot of nerves, are they a different person? Is somebody a different person when they're drunk? I've heard both of these thrown around colloquially. It's not obvious or straightforward to answer.

You could imagine a Ship of Theseus style replacement of all the neurons in your head with artificial ones. At what point would you stop being you?

My thoughts are that 'you' as a person change constantly, year to year, and who you are now is not the same as 5, 10, more years ago. I don't think it's so much that you are a different person because you lost a limb or are drunk, it's the change in personality and mind that accompany those that makes that person different. You could absolutely lose a limb and be 'the same' person, but you could also change significantly.

Sure but my past selves are also part of who I am. Without them I would not be me, and so I think they are more me than not me.

Never. "I" am a pattern of self awareness. The constituent parts are irrelevant. So long as the parts support the self awareness, "I" am.

So you would have no qualms about stepping into a Star Trek-style transporter, having your pattern scanned, your matter destroyed and recreated at the destination? If so, I would ask: what if the destroy step malfunctioned? There would be two of you. Which one would you be?

Both would consider themselves to be me, as both would be a legitimate continuation of the pattern of consciousness that is me. The divergence would create something of an ethical dilemma in the case of marriage, property ownership, rank, etc. Would both be granted the rank of the original, seeing as they are both a direct continuation of that being?

Seeing as at least one episode of Star Trek dealt with such a thing, I wonder if any ever dealt with the possibility of a single individual with access to a transporter creating a continuous set of copies from the original scan, perhaps saving at intervals and allowing the instantiation of variously youthful or experienced copies to be made. The divergences over time in such a branching consciousness would make for an interesting sci-fi thought experiment, I think.

Without instant loss of identity, I would add. It is widely known how semipathological states are cause of character, mood, life style, etc. There is no strict line between 'you' and your body (and internal-external environment); cutting or hacking non-utility parts of it will change you in short period of time, compared to original, as it happens with less radical change of climate, country, job, gender, food.

> A zoo is still a zoo if there aren't any animals in it

Is it? Identity is an interesting thing. To use a commonly-cited example-- if I swap out the muffler of my car and toss the original in the backyard, I think most would say I am still driving the same car. If I do the same with the front left tire, it's still essentially my car. Even if replace all four tires, same. But what if I swap one part a day with a replacement, after a while I'll have all my original car parts in the backyard-- and am in effect driving a car made of totally new parts, but is this still the same car? If not, when would you no longer say it's the same car? And, if I assemble the collection of gradually discarded parts sitting in the back yard into another car-- now what? Which is my car? The thing I'm driving or the car made of the old parts? Or are they both the same car?

Am I really the same person I was when I was 10 ...or 10 months? What is the "me"-ness, or are we talking about a different person? Where's the line...

Or... when Captain Kirk uses the transporter-- his molecules are disintegrated, and then a copy of him gets assembled on some planet (using local materials I believe)... So is "he" transported, or is he being killed and replaced with an exact copy? (I think this question made its way to a Breaking Bad episode)

Anyhoo. Is a zoo without animals in it still a zoo? I dunno.

It's an age old question indeed, the example you cited has been recorded from at least the first century: https://en.wikipedia.org/wiki/Ship_of_Theseus

This kind of stuff is fun to think about. In my opinion identity is based on behaviour, not composition. So long as an entity matches a given behaviour profile, then for all intents and purposes that entity IS the thing that the behaviour is normally attributed to. Kind of like Duck Typing: "If it walks like a duck and it quacks like a duck, then it must be a duck."

So my response to your car example is that both vehicles are "the same car" since both get you around and both are owned by you.

In that sense, as your behaviour changes so does your identity. If you were able to 100% accurately encode all the actions you could ever take into a Markov Chain, then I would argue that Markov Chain is what makes you "you" at that point in time.

So if an alien abducted you, created a clone to replace you while you are experimented upon, you'd still agree that you are living normally, and nothing happened to "you"?

Interesting! I would say that I am living both normally and abnormally since "I", in this case, is referring to two entities which are indistinguishable in terms of their behaviour.

Conversely, people usually go through profound behavioral transformations several times in their lives. Does that mean they are not "themselves" anymore?

Very broadly speaking, I would say yes. Again this is just my take, but I argue that different sets of behaviours are indicative of different identities.

For example, at work I may keep to myself and be very quiet - in that setting my actions would define me as an introvert. With my friends I may be more outgoing and talkative, which is more characteristic of an extrovert. So I have two identities depending on my behaviour. I am not my introverted self when with friends, and not my extroverted self when at work.

Few years ago, I was in a PR show for a shopping center where Paris Hilton showed up. Everyone was interested to see her. It turns out she was not the true Paris Hilton but a doppelganger.

Well, technically speaking, at least for a car, you can draw a pretty clear line. Your car is your car because it is registered in your name through a number soldered on its frame. Changing the frame would change that number and you wouldn't be driving the same car, at least from a legal point of view.

But yeah, is a zoo without animals still a zoo? Hard to say. Even without animals, a zoo would retain its potential to be a zoo. Meaning that you could put animals in it and would be back to being a zoo. Same thing can't be said about a restaurant, for example. You can put animals in a restaurant, but regardless of how good you can lock them in it's still not a zoo.

It's hard to say because it's not a yes/no question, and the most useful answer is going to be very context/state dependent.

A zoo isn't a collection of animals - it's a social, financial, and cultural structure with associated buildings, signage, web site, and staff, that usually houses animals.

If you lose the animals temporarily, you can keep the rest and still have a zoo. (This has actually happened during wartime evacuations.)

If you lose everything, you have a former zoo.

We have minds that put simple labels on complex relationships.

Interestingly, at the sub atomic scale, the quantum state _is_ the identity. If you have two particles at the same state, then it's meaningless to say you have two particles, add they are actually the same particle...

A zoo without animals is just a collection of buildings, sure it could be a zoo again but it could also be anything else.

A bit like a Lego house, you can break it up and you have all the parts to make a house, so it is potentially a house but it could also be anything else.

http://imgur.com/a/UBDSO

Indeed it could ;)

You are also not the same person as 1 millisecond ago, since numerous neuronal connections changed.

So it definitely comes down to the definition. You would also be you if your brain were just in a glass with wires and you could process input and give output through a computer maybe without all the gut bacteria.

I think the key part is conrinuity here. What happens if you step into a device which disassembles you atom by atom then reassembles you (assuming that this is possible)? Relevant article: https://waitbutwhy.com/2014/12/what-makes-you-you.html

The Ship of Theseus question is certainly relevant to a discussion of identity changing over time (our body's cells are constantly turning over), but I think it's completely unrelated to a discussion of the line between my gut bacteria and me.

Though to answer your question, "I" am an emergent phenomenon resulting from the interactions of the atoms in my body. "I" am just a wave passing through the universe, with my body as the medium of transmission. Similarly, "wind" is merely a description of what the air is doing where you are. As the wind blows, the specific air molecules you're observing as "the wind" are completely different from moment to moment, but a breeze persisting through an afternoon is all perceived as being the same wind.

Your gut bacteria determine a lot of your behaviour.

And the most interesting animals determine the flow of traffic around the zoo. But the zoo is still not the elephants. My environment also influences my behavior, but I am not my environment.

> a copy of him gets assembled on some planet (using local materials I believe

Doesn't the Star Trek transporter use the _same_ atoms/materials without making a copy?

Are the dead cells you're carrying around like your hair "you?" What about food? At what point exactly in the digestion process does it cease to be something else and become part of "you?" Is your urine and fecal matter that's still within your body "you?" How about the oxygen in your blood? Is that you? Saliva? How about tears? When to tears stop being you and become something else?

Interestingly, the makeup of your gut biome con dramatically affect personality.

https://www.theatlantic.com/health/archive/2015/06/gut-bacte...

Parasites can also alter your personality. Perhaps they can even turn you into a cat lady/man.

http://abcnews.go.com/blogs/health/2013/09/19/cat-lady-paras...

> "A zoo is still a zoo if there aren't any animals..."

Sounds like a Zoo-Wannabe to me.

If you fall into a coma or vegetative state, are you still you?

What about during anesthesia, or deep sleep? (disregarding the certainty that you will wake up)

When you're tasting yoghurt, it's tasting you.

I guess you are just an ever changing object, referenced by a name, created by your parents and affected by your environment.

Human myName = new Human(mother, father, environment, spacetime); Location birthPlace = myName.mother.getCurrentLocation; location bithTime = myName.myMother.getCurrentBirthTime; myName.removeAllLimbs(); myName.upgradeAllLimbs(); CloneUtils.cloneHuman(myName, 'myClone') AssertEquals(myName, myClone) //false

Hm what happens if we make those values immutable?

That's a bit interesting, what WOULD you do to model this?

Human individuals are a dynamic, changing pattern that persist for 80 years or so.

>There are more bacterial cells in your body than there are human cells.

I couldn't believe this was true so I looked it up. Apparently it really is! Of course the bacteria are on average much smaller and lighter than human cells. Also this:

>The numbers are similar enough that each defecation event may flip the ratio to favour human cells over bacteria

I think it's instructive to consider an article written by a bacterium about the possibility of living creatures at the metre length scale.

Well that rules out Boltmann brains https://en.wikipedia.org/wiki/Boltzmann_brain

Whales are always the go to for examples of large lifeforms but even that is part of the issue you taken about, restricting the definition of a lifeform to being what we think it should be.

https://www.scientificamerican.com/article/strange-but-true-...

http://oddculture.com/biggest-animal-made-structures-in-the-...

It's answer of "No" is predicated on two assumptions: that the lifeform is not colonial in nature and that time is not a localized phenomenon. While on the surface that later assumption might sound absurd, our universe could very well be a Local Bubble of time. Time could even be a biological function of a higher dimensional being that is the size of the universe. There is also no way to disprove that without observing beyond the universe, which may get a bit dicey.

> There is also no way to disprove that without observing beyond the universe, which may get a bit dicey.

My high school physics prof had the best answer to "What is beyond the universe?" --> "Surely if we ever find something outside of the universe, we will be smart enough to call that the universe too"

He was referencing the idea that universe contains everything by definition.

Thats a clever but not very mathematical answer. The general problem here is the conflation of universe i.e. "all of spacetime and everything we will ever discover" with the idea of a universal set, which doesn't have to include all elements and is rather arbitrary/relative.

In terms of definitions, generally cosmos contains everything.

Universe is our local observable space-time with the earliest event we can detect being the big bang.

> Universe is our local observable space-time

So if we observe something beyond what is currently observable, would that not become observable and thus part of the universe?

Yes, but it might also be the case that we don't observe something outside of it, but rather infer the existence of something outside of it through some other phenomenon (which is much more probable - observing something outside of the visible universe as we know it would violate relativity). In that sense, it would be there, but would never be visible.

That's a really interesting question. If something is indirectly observable (you can observe/measure its effect), does that make it observable or not?

Transitivit would say yes. If A implies B and B implies C then A implies C. That is, if you can observe A and that implies B, then you can observe B. Which makes it observable, no?

All observations are inferences from indirect phenomena.

You're in a room. You give it label "room". Then you find a door, you go outside of the room, you don't call everything outside "room", you give new things new names.

For now we're stuck in our universe, we know it's expanding (in something, potentially). So we preemptively give the name "cosmos" to EVERYTHING. It's entirely possible that cosmos is equal to universe. But it's also possible there are other universes out there, or something entirely different.

In your scenario, the door is a clear divider between "room" and "not room." What's the equivalent divider in the universe scenario?

The term observable when used in the context of the observable universe doesn't necessarily mean something we can actually measure or look at, but rather that which could theoretically have interacted with anything we could interact with based on the speed of light, the age of the universe, and cosmic expansion. Think of it as a bubble of time and everything outside of it hasn't happened yet.

Thinking about what exists outside the universe always makes my brain feel weird. It seems impossible for your thoughts to imagine anything because your thoughts themselves are bound by the universe itself.

Well even worse, our thoughts are bound by some maximum distance of comprehension. We can abstract the stellar scale but we can't understand it like we understand the distance across the street or whatever. I find this frustrating :(

Well I think the implication that we can't understand/comprehend these things is itself frustrating and also wrong. Why does one assume that the scale of the universe and the scale of that street you refer to are any different? In both cases you are experiencing and considering an estimation of potentially infinite space at an almost metaphorical level as it relates to your experience, plans, and actions.

Indeed, you can consider the universe as this thing which is maybe boundless and has so much stuff and might go on forever but for some reason you think it's any harder than realizing that the street may be infinite in space as well, by virtue of continuous subdivision. Before trying to dive in on any estimate of the smallest thing, do remember that smart people once thought atoms were the smallest thing, and then particles, and so on. And remember that the street itself, even just the stretch you're concerned about, is composed of a ludicrously large number of the "smallest" things we current are aware of.

If we let go of this idea that at our own size, things are just some number of things that we can reason about (since that's clearly false, do you reason about the billions of living organisms in your own body right now? Could you?) then we can start to realize that smaller or bigger, we're merely consider a continuum at different scales and it's perfectly reasonable for the human mind to do so, it does so every day all the time.

I was thinking along the lines of evolutionary biology - I'm assuming my human brain is only capable of truly processing scales that realistically my ancestors would experience.

> we can't understand

Understanding is just a psychological phenomena. Its your brains who choose what ideas they mark as 'understood'. Thus its under your control what you understand and what you are not.

Once beeing a drunk teenager I felt myself understaning all the things in the whole Universe. Its pretty hard I'd say, because I never felt like this thereafter. Though I didn't tried to repeat it. Probably alcohol is not the best fit for it, maybe there are some drugs that can make you to understand.

I believe that somewhere in the brain there is some special spot, and all you need to understand everything is to thrust an electrode in that spot.

If you live your brain as I do and prefer not to control your brains in possible harmful way, than (I'm pretty sure) if one get some special training on this he could come eventually to everything-understanding state of mind. Maybe it even allow to switch by volition between that state of mind and state of mind of Socrates, who used to claim that he understands nothing. I didn't try it myself because I'm not sure about arbitrarily control option, and generally prefer Socrates' way of thinking.

But if you don't like to cheat, there is honest way to start understanding a very large distances. In general mind mark as understood all the things it is used to. You may train yourself at imagining large objects through some sort of succession. You should do all sorts of mental work with those objects in your imagination -- moving them, rotating, colliding, flying by or through them... Try to use different and constant kind of objects for every order of magnitude -- it might be really helpful. It will take time, but its still possible.

I find such thoughts extremely fascinating. I've even toyed with the idea of podcasting this line of thinking. I put two test episodes up on Soundcloud for anyone who's interested.

https://soundcloud.com/martin-adams-387371255/sets/lost-in-t...

I think it feels weird because we define universe as having neither outside nor boundaries. There's a contradiction in terms. It ceases to feel strange as soon as you update the concept to something that has a boundary either in its spacial extension or through some kind of extra dimension.

The analogy I use to explain this to people is simply how it is impossible to go further south than the South Pole.

There is no physical barrier stopping you from moving in any direction, but due to the shape of the Earth you have reached the southernmost point.

It is likely the same with our universe, and its inherent morphology, too.

> we define universe as having neither outside nor boundaries

Do we?

> boundaries

There's one at the Big Bang. You can go through contortions to try to remove it (Hartle & Hawking's "no boundary proposal"; Carroll & Chen's "two-ways-to-de-Sitter from arbitrary initial surface") but so far attempts have come at the cost of introducing a lot more conceptual baggage.

> outside

"more of mostly the same" unless you think that one metre or one light year or two hundred million light years beyond the Hubble radius the universe is vastly different from the stars and galaxies we have around here. What could have happened to early galaxies that 200 million years ago were in principle observable from the Milky Way, such that they wouldn't now resemble the descendants of early galaxies that are 200 million light years closer to us?

If time were a different thing somewhere else, then physics in that somewhere else would very different, and our local concept of spatial size and even mass would not be applicable. So you still wouldn't have a life form "the size" of Galaxy.

But you would still have something just as remarkable.

Given no context I would have guessed that this comment was made on a Star Trek fan forum.

The position that time is not a localized phenomenon is preposterous. Given the observations of relativity and the effect that local gravitational force has on passage of time, and more recent experiment and theory about time actually arising as an effect of quantum entanglement (https://arxiv.org/abs/1310.4691), to presume in the context of such a big, extremely-theoretical idea that time is not local is plain nuts.

It's not so hard to imagine that the rules of relativity are imposed and that outside of that imposition, they don't exist or are discontinuous to some degree. Indeed, it doesn't even take any imagination if one considers the theories and research related to what I linked above.

So personally I'd dismiss the conclusion given its predication on this idea. To me, time not being local is the controversial position.

>It's not so hard to imagine that the rules of relativity are imposed and that outside of that imposition, they don't exist or are discontinuous to some degree.

As if some not widely accepted recent papers without empirical verification are the ultimate source of truth in physics? All kinds of bizarro ideas are a dime a dozen in papers...

Time as an emergent phenomena is hardly a fringe idea.

> preposterous

Well, specifically, proper-time intervals are path-local in General Relativity (GR). There is a unique coordinate-invariant proper-time interval between two points on a timelike worldline.

I think that extending that to "time is a localized phenomenon" is harder than it seems, notably because worldlines depend on the full solution of the Einstein Field Equations. In a Big Bang cosmology (with a hyperbolization of the EFEs and ignoring constraints and diffeomorphism freedom), it's pretty brave to deny a relationship between the early boundary and the values of the fields at any point p on the manifold given that the causal cone at p of M contains the Big Bang.

> effect that local gravitational force has on the passage of time

It's the metric that leads to Lorentzian observables between observers at different points in the manifold. The metric near bodies like Earth closely approximates that of Schwarzschild spacetime in the way it generates geodesics including the null geodesics (among others) carrying information from one observer to another. Effects like gravitational redshift arise from the fact that in spacetime more-curved paths are shorter than less-curved paths (as opposed to how curved paths are longer than straight paths through Euclidean space).

The metric's generation of geodesics is difficult to relate to a classical force or potential in general. Two objects in vacuum free-fall can be at different gravitational potential while feeling no force whatsoever; the one at higher potential ticks faster. It's a bit easier in near-Schwarzschild. Consider two atomic clocks falling from different altitudes[1] towards the same point on the (practically atmosphere-free) moon; almost all observers will agree that the higher clock runs faster than the lower clock until they are both smashed together on the surface. Yet if each clock is equipped with an vector accelerometer, both accelerometers will point nowhere in particular with a magnitude of zero from the start of their free-fall trajectory until collision with the moon's surface -- the first time force is reported by the accelerometers is when "lithobraking" starts.

However, properly considering gravitational potential as a 4-vector generally requires some choices which eat the redundancies in the Einstein Field Equations. In General Relativity one has only the metric and Christoffel symbols and tedious arguments about which mathematical objects correspond to a Newtonian notion of a gravitational field (answer: "it depends" or "none of them"). Gauge-fixing lets one set a "depends" condition such that one can recover a vector potential field and a scalar field strength at each point; this approach is taken very seriously in Fedosin's covariant theory of gravitation for instance.

> effect that local gravitational force has on passage of time

Even if one takes steps to model some aspects of the gravitational interaction as a force, the proper time interval of an object doesn't change with the force acting on it. But the frequencies, lengths and related quantities of an object at some distance does depend on the force the object feels compared to the force the observer feels. (Moreover, if observers are in vacuum free-fall then they will feel no force at all, and can only infer the gravitational interaction from either a deviation from a straight-line track on a choice of coordinates, or by comparing the ticking rates of their own wristwatch with the wristwatch of several observer at some distance -- from [Synge 1960] this would take a minimum of five freely-falling wristwatches in total).

Generally the complexities of setting down this kind of gauge-and-coordinate conditions leads relativists away from worrying about relating GR's mathematical objects and Newton's, and it's easier to say "gravitation is not a force" rather than "with some effort you can treat gravitation as a force in local coordinates and in a local gauge but you'll still find yourself returning to the Special Relativistic forms of physics equations because they genuinely are the simplest form and are always valid in the neighbourhood around a point on a geodesic".

> if one considers the theories and research related to what I linked above

General Relativity is in extremely precise accord with observation at many length scales and direct experiment within the solar system. Deviations from General Relativity that are different in the limit of the parameterized post-Newtonian formalism (which applies at solar system scales) are almost entirely ruled out. Although it is perfectly reasonable to consider General Relativity to be an emergent theory, the theory it emerges from is (a) unknown (b) unobvious and (c) extremely difficult to take guesses at. Indeed, your offer of 1310.4691 is wholly rooted in this: canonically quantized GR conflicts violently with observations and experiments, and the usual workaround is to do some condition-fixing (which your referenced paper does) and then to try to get around the pseudo-forces brought in to describe local physics (in models like Page-Wooter these pseudo-forces appear as constraints in the theory ([2], which your authors reference in their first sentence and several times thereafter). The paper you point to also notes that the proposed experiment cannot select among a number of theories including General Relativity (where the Hamiltonian itself is a constraint).

> To me, time not being local is the controversial position.

I dunno, we do appear to live in an observable universe which admits an obvious equatorial 3+1 slicing in which there are an awful lot of Eulerian and nearly-Eulerian observers. Is the hill to die on the alignment of one's "natural" choice of timelike axis with the metric expansion or the way you put down coordinates on that axis? And how do you square either of those choices with the initial value formalism?

- --

[1] This is implicitly fixing a gauge wherein the surface of the moon is special; this is analogous to having a set of tunable air-pressure gauges at a point at sea level and setting it to 0 there, then using the readings of the tuned pressure gauges in helicopters riding above one another over the 0 point in order to say things about the state of each helicopter. In particular, one would use the reading of the pressure gauge as the basis of a coordinate axis (e.g. in marking coordinates on the radial axis in spherical coordinates on the 0-calibration point, or on the z axis in a choice of Cartesian coordinates on the 0-calibration point).

[2] K. Kuchař, in G. Kunstatter, D. Vincent, and J. Williams (eds), Proceedings of the 4th Canadian Conference on General Relativity and Relativistic Astrophysics, (Singapore, World Scientific, 1992).

We still don't know if the Universe itself isn't a living organism with us playing the role of tiny viruses that require intelligence/consciousness to fulfill certain tasks, like what gut bacteria does for us.

We do. If you bothered to read the article, it makes a point that the communication speed between the components would be slow enough (even at light speed signaling) that the age of the universe would not have permitted sufficient time for such an organism to evolve and do anything.

Well, maybe the age of universe is indeed "too short" for it to do anything useful yet? Your argument seems to be supporting the idea that the universe is like a baby who is still too young to do anything.

Or that it might not be useful to conceptualize the entire universe as a single biological organism.

I mean, before humans, there were eukaryotes, and prokaryotes before them. My argument is not supporting that the universe is a baby. It is saying that the being does not exist because it could not have evolved on this timescale, in the same way that single celled organisms are not human babies.

If we assume that the big bang was actually the conception event of some other cosmic entity, the universe could very easily be a living organism that's the equivalent of a few microsecond old fertilized zygote.

So yes, a universe sized lifeform could not have evolved randomly since the big bang, but you can only be confident about that if you assume that nothing exists outside the spacetime bubble we call the universe.

or it could be the big bang is the relaxing of a muscle cell is some cosmic monster. Or perhaps the big bang was kinda like enzymes, breaking something hard to eat into a nice easily digestible heat bath. or it could be an edge transition of one wire of some cosmic computer.

It's fun to kick around crazy ideas on Saturday afternoon. It could be anything. Sadly, there's no way i'll ever know. But the idle speculation is still amusing.

Or, you can write a science fiction short story and make it true in a fictional world you invent.

Suppose an organism is born and lives for 100 years. The organism is 10 metres across. However the rate of propagation of chemicals, blood, nerve signals, etc across its body is only 1mm per year. So over the 100 years if someone touched one of its extremities, the signal for that event would only have propagated across 10% of the diameter of the organism in its lifetime.

Does it really make sense to talk about it as being a single organism? How could it do anything in a coordinated way?

Or how about an organism that grows at say 10m in diameter per year, but signals across its body only propagate at 1cm per year? Again, how can it be considered to be functioning as a discrete organism? Surely if such a being evolved, its parts would perforce do so independently of each other? There could be no cross-organism coordination. It would have to disintegrate or devolve into local functional or operational units if it were to do anything effective at all.

What if it lived for 500,000 years? You can solve your problem by assuming the organism lives longer. Maybe the universe is an organism that lives 10^100 years. We have no idea. And, as pointed out other places in the thread, by the time we are pondering about organisms of that scale, the very laws of physics (speed of light, spacetime, etc.) may be different.

Ae could be in it's stomach, where processes slow down the speed of light by a factor of trillions so that we are easier to digest.

None of these are testable hypothesese of course. But one day they may be testable.

Though most stars will have burnt out in a couple of billion years and heat death will come, where no cellular life can exist, so not sure if this is more useduo than now.

Universe is full of particles with quantum entanglement; those can be your "immediate" messengers of information. But anyway, there are way too many assumptions in your objections about the character of such life and its requirements, as well as in the article itself. We still don't know the fabrics of the Universe, just some rough approximations in certain areas with known confidence; there likely are many surprises awaiting us in the future (like discovery of radioactivity etc. in the past).

As I understand it, quantum entanglement doesn't allow for affecting causality faster than the speed of light. So that doesn't solve the problem.

Your comment doesn't really give accurate credit to the current state of knowledge.

Yeah, it was kinda stupid in this context; I meant to show that some actions are happening "immediately" even across huge distances and not that we need to wait for e.g. gravitational waves to move at the speed of light. Not that we can actually utilize this for conveying information immediately.

I think you're onto something.

Yes, quantum entanglement doesn't seem to allow for transmission of information in the conventional sense. However...

Take a universe full of particles, many of which are entangled with each other. If you consider the entanglement as primary you can think of the entangled particles as single entities that have "extensions" into space-time that can be widely separated. I don't think it's at all clear that "living" processes cannot be carried out on this "substratum" of interspersed non-local entities.

But I'm waaaay over my head here, so I'll stop waving my hands. :-)

What if quantum entanglement is simple an indicator that there is another way to send information - but we haven't discovered that function of that mechanism to do so yet?

It's a fun idea. I'm not sure if there is any reason to think that quantum entanglement actually indicates this. I haven't heard anything like that before, and it doesn't seem like a small leap of logic, so I would guess not. But I'm also not a physicist.

Possibly, but then it would break relativity and potentially a lot of other things.

That's the point. Relativity is a barrier and we want a way to break through it.

> Given that our brains are composed of neurons, which are themselves, in essence, specialized cooperative single-cell organisms

Don't humans to a degree fulfill this role; the mass behavior of the species (recently) acting as form of brain with emerging self-awareness of the galaxy/universe; since we study it, and are also part of it?

I argue against this idea. Part of our sapience is that our neurons can coherently aggregate into specific thoughts leading to choices (and actions performed on those choices). What would the nature of supersapience be? Just sapience, so a single human brain is a holon.

Behavior can be influenced by others, but will isn't superceded by a crowd.

> Behavior can be influenced by others, but will isn't superceded by a crowd.

It often is by governments though. Also judging by polling on small sample sets, which often match whole population elections they do coherently aggregate; and then those governments make laws which incarcerate or penalize going against them.

Also isn't that the nature of science to provide coherent aggregation of knowledge that is agreed upon (though testable hypothesizes). Which is generally different from government policy, which usually doesn't use evidence based decision making in the scientific sense.

You're presuming the speed of light is the hard limit. Whereas we know for a fact faster movement is possible - the space-time itself was expanding faster.

^This. The universe expanded faster than light, that's why we still can't see everything, so saying things like 'the communication speed is too slow to permit evolution' is just wrong, it also doesn't take into account things like time doesn't actually exist, it's just a biological construct.

The whole article is predicated upon a bunch of faulty assumptions, it's like it was written by a simple minded child.

You have some misunderstandings about the expansion of the universe. I would recommend reading http://www.preposterousuniverse.com/blog/2015/10/13/the-univ...

In addition to that, positing a 'life form' that exists in the presence of space continuously and literally pulling it apart doesn't seem likely to be a net positive for our galaxy-sized life form.

No, it's you who gets incorrect information from some random blogs.

The size of the observable universe: ~93 billion light-years

Time since the big bang: ~13.7 billion years.

http://curious.astro.cornell.edu/about-us/104-the-universe/c...

https://phys.org/news/2015-02-fast-universe.html

The author of that random blog is Sean Carroll, professor of physics at Caltech specializing in cosmology and GR.

That doesn't mean he must be right, but I feel pretty comfortable citing him.

I bothered to read the article, and I don't buy that premise at all.

It seems to indicate that for a thought to happen, a signal must traverse the entire length (width?) of your brain.

That isn't how it works at all. Many thoughts are localised in the brain. Further, some signals don't need to get to the brain at all. And some functions of life don't even need signals to ever leave the localised region at all.

If you are cut, your blood cells spill out, clot, and prevent further bleeding from happening, all without anything outside of the immediate vicinity of the cut to be notified (although it's good to let other parts of the body nearby, say another finger, from exacerbating the wound).

If the organism were larger than say a planet, then why would not the brain become distributed, with the parts needed to deal with one quadrant of the planet located at that part of it?

Basically, this article is lazy. It makes a couple of very dubious assumptions, then runs full-forward on those assumptions, never stopping to think if those assumptions even make sense.

Yes, if we are to try to imagine a life form that looks exactly like a human (or other life-form that we find on Earth), but is the size of the galaxy, we start to laugh, because that couldn't work. But that thought experiment is pretty silly.

We don't. How do we know that the big bang wasn't part of the internal activity of another organism? There are just some things we will never know.

> If you bothered to read the article

This particular nasty swipe is not only not ok on HN, there's a specific rule against it. Please (re)-read https://news.ycombinator.com/newsguidelines.html.

I'm no expert on xenobiology, but it seems like in our search for life we're always looking for life like Earth's. Are we even looking for life at much different scales of size or time?

> Are we even looking for life at much different scales of size or time?

Yes, see: http://www.xenology.info/Xeno.htm

This book is amazing. Thank you for this

No, because we have no idea what the bounds are. We don't know what dissimilar life could possibly look like.

If I send you to a junk yard and say "Find my old microwave" can you do it? You'll probably start by looking for things that look like what you think a microwave looks like, right? But what if mine looks different?

We know life is probably somewhat rare in the universe, at least compared to the raw number of planets. But we know that Earth ticks all the right boxes to generate life, despite that adversity. So we look for things like Earth because it's more likely to be productive than a blind search with no bounds.

That comes out of the fact that life is an arbitrary label we apply to certain chemical systems. It lacks a rigorous physical definition.

Life on smaller, faster scales has been posited, but not in anywhere we can currently see. See, for instance, Dragon's Egg [1], which is a science fiction novel that very seriously tries to discuss life on the surface of a neutron star. I know it's fiction, but it's probably still one of the best treatments of the idea out there. Even if such a civilization would have zero interest in our resources we still certainly see no evidence of a star-faring galactic civilization of that type.

Life on larger, slower scales rapidly hits the problem that 15 billion years turns out not to be all that long when you start dividing it by thousands or millions at a time. The problem is that if you're spread out that far, you're probably mostly running at the ambient temperature, which is very cold and much slower, so not only do you need to take 3-6ish orders of magnitude of speed off for dispersion in space, you need to take 3ish orders of magnitude off for being very cold and thus chemistry being very slow. And you may need to take another 3-6+ orders of magnitude off for waiting for your very dispersed, very cold molecules to encounter each other at all, in order to do whatever reactions are supposed to be supporting you. The problem you have there is that on that time scale, the galaxy is a very active and violent place, with supernovae popping off and galactic collisions and passages through the arms and all these stars flying about far faster than you can react to them (rather than the stately procession we think we see) and all kinds of things that tends to make a sensible person thinking about this problem starting thinking that even were some magical force to create such a life form, it wouldn't subjectively live very long before being violently destroyed from its point of view.

(And there are really quite a few more factors missing from the story of how one could have such an enormous life form, like how one forms from what are, to a first approximation, hydrogen atoms with trace contaminants. The biggest "contaminant" also happens to be helium, which you're not going to be doing much chemistry on. Seems difficult to imagine what "chemistry" would be going on here. (And if you want to say "energy being", be concrete about what sort of energy it is you are talking about, and how it manages to accomplish any sort of reaction or computation. It turns out that at least in our universe, "energy being" is probably just a nonsense phrase with no possible physical referent.))

I wouldn't write the idea off perhaps as entirely as some people here have, but if such large organisms or civilizations are going to ever exist, they're going to have to exist in a later epoch of the Universe, i.e., they're still many, many billions of years in the future. Right now the universe is too young and vibrant and explosive for anything like that to exist for very long.

If these sorts of things intrigue you, and you'd like a semi-realistic treatment of some of the similar ideas, you might consider https://www.youtube.com/watch?v=Pld8wTa16Jk . The boundary between "science fiction" and "the optimal possible engineering" is fuzzy but that video does a decent job of riding the line. One of the things I don't think he mentions is that some of the "slow" civilizations he mentions, where a thousand years literally pass like a single thought, is that they might be geographically dispersed, for at least some of their components, on this scale. As you hypothesize beings or civilizations (and honestly, from where we sit, there isn't necessarily that great a difference between the two things) that exist orders of magnitude more slowly than we do, the speed of light stops being such a bummer and "virtually" speeds up.

[1]: https://en.wikipedia.org/wiki/Dragon%27s_Egg

This is my belief. I've always wondered how the reproductive mechanism will work. It's a little anthropocentric and pseudoscientific, but I like to imagine it's our destiny as humans to reproduce the universe.

I would rather hack and reprogram it ;-)

It's a thoughtful article, and I love the reference to Burroughs' Soft Machine. But it doesn't distinguish clearly enough between self-conscious organisms and the rest. It's true that consciousness and evolution thereof likely crap out when latency goes over a few hundred milliseconds.

However, I see no limit to the size of zero-gravity organisms like the honey fungus. Fungi are filamentous, so there's no unsurmountable problem with heat dissipation.

And even for self-conscious organisms, I can imagine hierarchical organization, such as Rajaniemi's "metaself" or Watts' Bicameral Order.

Since proteins cannot exist in space, then, using the currently accepted definition of "life" at the basic level as the complex of processes that allow protein molecules to exist, then the answer must be 'no'.

On the other hand, it is an interesting mental exercise to also consider other reasons why such creature might be impossible. One reason could be because the time needed for such creature to grow from something much, much smaller (as it usually happens in biology) would be longer than the age of the universe.

Another one is that nerve impulses travel slower than the speed of light, and so, again, it would take forever for a signal to reach the central nervous system. One could argue that the creature can be "decentralized", i.e. look more like a large colony of smaller organisms, but then the question arises as to what makes it a single creature in the first place.

Yet another issue concerns what drives the evolution of this particular species, and, again, the time it takes.

So far, all these considerations unavoidably lead to the answer 'no'.

Maybe you should expand your definition of life to not require proteins.

From Wikipedia:

> From a physics perspective, living beings are thermodynamic systems with an organized molecular structure that can reproduce itself and evolve as survival dictates. ... A major strength of this definition is that it distinguishes life by the evolutionary process rather than its chemical composition.

Is a sterile human not alive by this definition? I find that life needing to reproduce is a questionable condition. If we say reproduction is not requisite, then neither is evolution as evolution requires generations.

"Evolve as survival dictates" is a bit pointless, as if you don't change to survive (Assuming the change is requisite) you do not survive. Survival is defined as still being alive, so if you don't survive you are no longer alive and thus not living. We've then defined a state where a living being must continue living to be living, well sure - I agree.

If you remove reproduction, remove evolution, what else is left?

Evolution doesn't necessarily involve reproduction. A sufficiently advanced human (or computer) could enhance itself technologically, continuously replace it's organs (Ghost in the Shell), even change it's form and this would count in my book as a form of (non-biological) evolution. You could say the same thing about culture.

I think that definition is more for lower level life forms, where is not clear (see viruses).

Higher forms of life could be defined differently - agency, ability to sustain/repair itself, opposition towards environment. But then you might encounter difficulties with classifying a self repairing (non-sentient) robot as "alive".

> Evolution doesn't necessarily involve reproduction.

According to Darwin, it does. A giraffe got its long neck not by stretching it but by dying if the neck was not long enough to survive and letting the ones with (accidentally) better genes to live on and - importantly - reproduce.

My apologies, I was being a bit pedantic - Evolution is formally traits changing over generations, while adaption is changing traits over an organism's lifetime, though I believe you are using them interchangeably as "something changing".

I don't know what is left, but I have a hard time using such an embattled definition.

Well, your sterile human appears to be a strawman. Obviously, a person may be sterile, but the organism cannot stay alive if the continual process of reproduction (of cells, their organelles, and molecules) inside it ever stops.

A multi-cell organism is an emergent phenomenon that helps protein-based molecular structures to do their thing ("life").

No, it isn't. Imagine a hypothetical sterile human that was single celled - suddenly we've reached the same conclusion without the sub-organism reproduction issue. Making reproduction a core premise of being alive really drives to the idea of mortality, as reproduction is a way of overcoming our mortal coils. Yet, it is truly reasonable to classify reproduction as the only way? It also assumes a lineage, which is not required for synthetically created organisms.

I've said this elsewhere, but proteins are not required, in any regard, for life. They are an emergent phenomenon of the Earth's chemistry, not a rule for life. I mean, what is a cell even - "A fluid filled, membrane enclosed thing"? The reason cells are structured as they are is because of water, so a non-water based organisms would likely look much, much different.

Somehow I am having hard time imagining a single-celled, synthetically created, non-water-based, sterile human being...

I am not sure I understand the drive to redefine life beyond the life as we know it (i.e. what it actually is, as a fact), the drive that leaves one in what can only be seen as the domain of fiction at best (and pseudo-science at worst).

Do you believe its possible for a computer, more specifically an Artificial General Intelligence, to be "alive" (if one such thing ever gets built)?

Conscious? Yes (possibly). Alive? No.

I'd say It differently. Intelligent? Yes Conscious? Probably not.

Does intelligence imply life? I'd say no.

The drive was that I don't believe the original question, "Can a living creature be as big as a galaxy" is reasonable for organisms we are familiar with. If we hope to answer such big hypothetical questions, we may need to find ourselves in foreign lands as well.

We are discussing hypothetical life forms, different to the ones on Earth. Obviously we can not use a definition of life which only applies to earth-based life: we need to generalize more.

There are a few things that are wrong with Wikipedia's (re)definition of life; one thing I would like to mention is that what is missing from it is that a "living being" cannot exist outside of a pretty rich (and sufficiently dense) material environment, which 'space' as such is not.

Incidentally, a galaxy-size dense environment (and the creature itself) would collapse into a bunch of stars and black holes "in no time".

> a "living being" cannot exist outside of a pretty rich (and sufficiently dense) material environment

What makes you say that, though? I don't see any reason for it. Some ethereal galaxy-scale lifeform might be thinking as well that "life cannot exist in the extremely hot, hyperdense environment of a planet" for example. This is pure speculation from your part.

You may be right about ethereal lifeforms, but real ones need to eat, breathe, etc.; they are also subject to the laws of thermodynamics: they need energy, and also in order to maintain low entropy inside they must increase the entropy of the environment - which would be hard if there was no environment to speak of.

There are animals on Earth with a decentralised nervous systems (most famously the octopus) and there isn't any confusion about whether they're classed as one animal or multiple ones.

Octopus does have the "central brain" though - which, I guess, may account for making it "one animal". On the other hand, an animal with a truly decentralized nervous system often can regenerate from its pieces, which makes the question of it being "one animal" in the first place a bit fuzzy.

There was an article just yesterday on HN about such a creature, with a decentralized nervous system:

> Ctenophores have no brain or central nervous system, but instead have a nerve net (rather like a cobweb) that forms a ring round the mouth and is densest near structures such as the comb rows, pharynx, tentacles (if present) and the sensory complex furthest from the mouth ... Ctenophore nerve cells and nervous system evolved separately from other animals and have a different biochemistry.

A starfish might be a better example.

There are also a lot of living beings with no nervous system at all, and there's no confusion either about whether they're classed as living beings or not.

I don't get why nervous systems should be brought into the discussion. Most living beings on Earth do not have any kind of nervous system, and I don't see any obvious reason for why fungi or plant-like life forms could not be as big as galaxies.

Proteins (Or the ability to make them) is not requisite for life, nor are nerve impulses, nor is evolution. If we encountered an immortal (Does not evolve), sterile (Does not reproduce), silicon-based alien (No proteins), that would most certainly be heralded as finding extraterrestrial life.

Reasoning about much large systems than our own is difficult. Imagine a bacteria attempting to reason about a human - the existence of fluid transport and centralized heating may seem a bit odd, as bacteria have developed to solve an entirely different class of problems at the organism level.

I'm not necessarily disagreeing, but what's the definition of life you're saying that would satisfy?

The "I'll know it when I see it" variety.

I don't have one. The normal definitions of life are useful approximations of some property, but we should always be reminded that they are just that, approximations.

What if a stable exotic location exist, where chemisty is able to form boolean processes.. is that live, if it computes and thinks, and is still just a huge state machine.

> Another one is that nerve impulses travel slower than the speed of light, and so, again, it would take forever for a signal to reach the central nervous system.

Signals in the human body do not arrive instantaneously. A life form at the galactic scale would either be decentralized as others have suggested, or it would operate at a much longer time scale.

I'm surprised to find no mention of Solaris by Stanislaw Lem among the fiction references. In this novel, a whole planet is somehow a living organism, truly alien to human conception of life.

An excellent read! I had the same thought. It's almost negligence not to mention it.

A bit of tangent -- the article talks about powers of ten, and hints at how powerful a tool it is for analyzing everything around us. This resonates very strongly with me. The entire known universe, from the smallest particle to the width of the cosmos itself, fits within several dozen points on this scale. It's incredible.

Personally, the last few years, I have felt that working to understand how all phenomena can be sketched out on the log scale has helped me gain a deeper understanding of the world. Of course, this goes hand in hand with related ideas, such as having a generally skeptical mindset, seeking first principles, etc.

These ideas has been very powerful for me, and I thought it might be worth sharing.

P.S. the book "The Black Cloud", mentioned in the article, is a really fun and quick read. I recommend it for any sci-fi fans.

This theory was once proven in a famous documentary http://www.youtube.com/watch?v=AJOVUF-HaDw&t=0m37s

> Stars are best regarded as living organisms, but organisms which are physiologically and psychologically of a very peculiar kind. The outer and middle layers of a mature star apparently consist of “tissues” woven of currents of incandescent gases. These gaseous tissues live and maintain the stellar consciousness by intercepting part of the immense flood of energy that wells from the congested and furiously active interior of the star. The innermost of the vital layers must be a kind of digestive apparatus which transmutes the crude radiation into forms required for the maintenance of the star’s life. Outside this digestive area lies some sort of coordinating layer, which may be thought of as the star’s brain. The outermost layers, including the corona, respond to the excessively faint stimuli of the star’s cosmical environment, to light from neighboring stars, to cosmic rays, to the impact of meteors, to tidal stresses caused by the gravitational influence of planets or of other stars. These influences could not, of course, produce any clear impression but for a strange tissue of gaseous sense organs, which discriminate between them in respect of quality and direction, and transmit information to the correlating “brain” layer.

From Star Maker by Olaf Stapledon, Chapter 11, Stars and Vermin

https://ebooks.adelaide.edu.au/s/stapledon/olaf/star/chapter...

Does a group of people have an emergent consciousness in its own right that no one person can individually experience?

Perhaps certain parts of the brain too "think" they are conscious but can't individually experience the same consciousness we as people experience.

Related: On Being the Right Size

https://irl.cs.ucla.edu/papers/right-size.html

It make me think of Von neuman probe. If we can consider that a robot or something with connections similar to our neurons can be a living creature. Then maybe if something like Von Neuman probes existed it could have colonized the whole galaxy (actually it could be done in a few hundred millions years) then those probes, while each one have is own brain, could communicate with the other probes and even if two probes at two opposite sides of the galaxy couldn't communicate, they would still be connected. Then maybe this network could be consider as a living creature.

Quick reminder: We don't know what the majority of the mass/energy of the universe is. Dark matter is ~20% of the universe and pretty much all we know about it is that 'it falls down'. Dark Energy is ~75% of the universe and all we know about it is that it makes galaxies accelerate away from each other. So, defining life or intelligence as we do is maybe not the best idea for long term thinking.

The ocean is mostly water, so hypothesizing the size of a whale is not the best idea for long term thinking.

When thinking about such things, you've got to ask yourself: under what circumstances would such a creature appear and under what circumstances could it die? What does it need? What constitutes a good or bad thing for it. How does it learn? How does it perceive? How does it act out its intentions? Does it have a self preserving instinct?

It doesn't make much sense for a creature the size of the galaxy. If it did, it would be extremely slow and alien to us.

A more plausible way would be if a human-scale civilization would create self replicating probes that would spread in the galaxy and bootstrap some sort of large biological or AI civilization.

I love topics like this :)

If yes, the next question might be:

> Imagine a creature that is as big as the galaxy, imagine its organ that is analogous to our brain is as efficient and big as is possible, what is the most complex concept that that brain can fully comprehend?

It's a different topic, but related. I was marveling at the diversity of life on Earth, which led me wonder: to what extent does sustained life on Earth depend on that diversity? I.e., what would be required or different for a planet to host and sustain a single species of life?

Given the nature of evolution, and that one subscribes to it, life on Earth started with a single organism that replicated. From that point until a replication modified the organism into a different species, there would have been one species. But was it necessary to have multiple species in order to sustain life?

Yes. Evolution is actually its own evidence. Biological evolution evolved out of necessity. Without constantly changing evolutionary pressures exerted by an organism's external environment there would be no need for evolution and it therefore wouldn't have evolved.

That's the opposite of an evolutionary argument. Evolution is not teleological, it doesn't arise to meet a need.

It's a kind of feedback loop in low-entropy systems that given enough time can produce interesting phenomena, including this message board.

"life on Earth started with a single organism that replicated."

I would tend to ponder that life in it's simplest form is not singular and never has been and this is the cause of evolution.

Available evidence suggests that life on Earth has a common ancestor.

This doesn't mean it was the only origin of life on Earth, but it is the only surviving line.

It also took a few days for complexity to arise. About a trillion of them.

"Available evidence" : that's because we still don't know how to look for it, or what to look for, and the reasons for that are complexity and time.

Wrong.

"Available evidence", because there are no extant lifeforms which diverge from the known set of amino acids, no prokaryotic life which doesn't have (or at least didn't once have) mitochondria, utilisation of the Krebs Cycle, and numerous other elements.

Again, other variants might have emerged. But they haven't survived, suggesting the extant line out-competed (or possibly out-lucked) any challengers

"Exhalation" by Ted Chiang is, I think, a great literary exploration of this topic and brings the essence of what is required for life, though it doesn't get into what life is as opposed to other phenomena. For those who've not read it, I may be giving off too much if I said anything more.

It is certainly more insightful (again imho) than this article.

http://www.nightshadebooks.com/Downloads/Exhalation%20-%20Te...

Sort of tangentially related is the physicist Geoffrey West, who decided to try to apply the thinking of a theoretical physicist to biological systems. His book Scale is excellent, and this is one of the most interesting podcasts I've ever heard:

https://www.samharris.org/podcast/item/from-cells-to-cities

Hmm, but what if the living creature had a density of neural circuitry similar to ours, and mainly interacted with things inside itself, and had slow propagation of knowledge? Not sure I understand this except under the hidden assumption of having a similar number of neural circuit elements

The comparison about surface areas is wrong. A creature could drastically increase its surface area by having many tendril-like appendages (i.e. hairy surface) and limiting the core body to consist of thin shapes. A fractal web of tendrils would dissipate energy far more effectively.

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

If anyone is interested in a sci-fi novel series that explores these kinds of themes for intelligent life, I highly recommend Ancillary Justice by Ann Leckie. (I've left the statement above intentionally vague to avoid excessive spoilers.)

Why only as big as a galaxy? Why not the entire universe?

http://www.geoffreylandis.com/infinite.htp

(Geoffrey Landis, the Melancholy of Infinite Space)

re heat dissipation - the author assumes a mostly-convex form, but if the life form as concave spaces (e.g. tentrils) then the surface-area-to-volume ratio can be arbitrary.

Aren't creature body sizes a function of some combination of food size and quantity? If so, what this hypothetical creature would eat?

What if the galaxxy itself were a living being, but we are so small to grasp this form of life

may be galaxy on itself is a living creature, and we are just like neurons in it. or cells.

So this requires a few things,

First off, single organisms can have pretty advanced local processing of control. An octopus has a nerve cluster for each tentacle that can operate independently of the main brain [1]. So in at least one case, biological brains delegate work out to another region of the body. An argonaut octopus actually detaches part of it body, which as far as i can tell, keeps living for a while. it's kind of creepy. The only thing i can't find an example of, is remote control. A detachable body part, with a nerve cluster, that responds to light or sound seems like what would be needed for the base creature. Evolution hasn't stumbled on that trifecta here on earth. But it sure seems like something that could have come about.

The latency argument isn't compelling. If i can send one message, i can send another hundred billion messages along with it. So, sure only a few thousand round trips, but a fabulous amount of information transferred. There's no actual biological equivalent to a semi autonomous drone, so i'm not sure what that would look like before the creature took to the stars.

There's also no real obvious way for this lone detatched tentacle to consume the resources of a planet. But whatever. I think one entity with those three features might have a chance.

Also, is the creature smart? Does it get to genetically engineer itself? do cyborgs count? That greatly simplifies things as well. The detachable parts could have detachable parts, and recurse down to whatever arbitrary degree is useful.

Alternatively if you admit superorganisms, then everything is much easier.

So anyway, you don't really need to send many messages when the message is "here are the latest designs for industrial architecture to dismantle a solar system and send the resources back" It's up to the billions of lone tenticles and their machines to execute the will of the super brain.

On the other hand, yeah, there's not going to be a galaxy sized amoeba or panther or anything like that. maybe an incredibly fine mist of fungus or mold, but i think it'd be too hard to keep a system like that from collapsing in on itself from too much mass. a galaxy sized ring of spider silk orbiting a black hole sounds like great science fiction. but i can't imagine that working.

[1] https://en.wikipedia.org/wiki/Octopus#Nervous_system_and_sen... [2] https://en.wikipedia.org/wiki/Argonaut_(animal)#Sexual_dimor... [3] https://en.wikipedia.org/wiki/Superorganism

Challenge accepted

Look, the vast majority of a galaxy is empty space. A living creature is obviously not empty space, so all that space would have to be filled with the creature's matter. Well, if you put that much matter so close together, it will all collapse on itself and create a black hole.

So no, you could not have a living creature as big as a galaxy.

Uh. The vast majority of what constitutes YOU is empty space.

Sometime go look up the amount of space between the protons, neutrons, and electron cloud in an atom.

The center of every galaxy is a black hole. Lol so the center of this creature would be a black hole?? Some weird creature

This article does not take into account quantum phenomenon. It's possible that instead of being limited by the speed of light transmissions, such a system uses quantum phenomenon for communication. Which then would make the whole argument that this article makes invalid. It's based on the premise that life would be based on the same sort of physics as life on Earth... which does not make sense as such life if it exists would evolve using a different set of rules which would include things such as limits on speed of light transmission in such large systems... so it would've learned to exploit quantum phenomenon for transmission.

edit:

Superluminal, or faster than light, communication is said not to work because it allows information to be sent into the past. There is however non-locality which is not the same thing. Sorry not an expert on this, but this seems to apply to the exact discussion.

https://en.wikipedia.org/wiki/Bell%27s_theorem#Importance_of...

There are no quantum effects that allow superluminal communication of information.

Sure there is. You've just not seen it on HN yet.

It is not possible to use quantum phenomena for faster-than-light communication. It's fine to speculate about completely new physics allowing for such communication, but it really doesn't have to do much with what we call quantum physics.

It doesn't need to take into account "quantum phenomenon" because the phenomenon you are citing is fictitious.

All communication relies on quantum phenomenon. The universe is a big mess of quantum phenomenon. It's not magic that lets you violate the laws of physics, it is the laws of physics.

It's funny with all the downvotes, first I never said that anything violated the laws of physics, I said that they don't follow the physics as life on earth. Second, there are many downvotes, but no actual evidence of what I said being wrong. I feel as if I am arguing with self-reassured people.

The burden of proof lies on you, not 'them'. https://en.m.wikipedia.org/wiki/Russell%27s_teapot

The same analogy can be applied in reverse.

The article here is the one that is making an unfalsifiable claim that "a living creature cannot be as big as a galaxy", but offers no definitive proof of nonexistence of such creative.

No, that analogy can't be applied in reverse. You're right that placing the burden of proof on the positive assertion is a dialectic oversimplification. But the specific claim, "A living creature cannot be as big as a galaxy" does not suffer from the problem of induction - we can use deductive reasoning to falsify it given relevant, empirical observations.

The classic example of white swans and black swans adheres to the problem of making universal generalizations because we simply have not yet observed a black swan, and we cannot use the continued observation of white swans as empirical evidence. However, we are not attempting to make a universal generalization based on inductive reasoning.

We have, available to us, a schema for enforcing the testability of this claim, which the article and its references explore in detail. The square-cube law and our current model of physics both make it impossible for a "living creature" to be as large as a galaxy, for any definition of "living" and "creature" that is reasonably agreeable.

The normal processes of life; including temperature regulation, metabolism, energy expenditure and movement would all be severely impeded in a single discrete organism of that size. Moreover, it would have severely limited cognition even if signals traveled at the speed of light, which handicaps both its own sophistication and potential evolution.

It doesn't seem appropriate to characterize something that cannot have these functioning traits as "living"; the only way forward seems to be to broaden our definition of "living" or "creature" to some sort of aggregated, abstract consciousness that makes organisms like ourselves analogous to bacteria. But that can hardly be called a discrete organism in the same way that our brains are cognitively independent of the life around them.

You're arguing with a physicist.

There's no such thing as "quantum phenomenon" that is distinct from any other phenomena. All phenomena are quantum. You're using that word the same way any other woo-peddler uses it: to worship ignorance and preserve the 'majesty' of the unknown.

> All phenomena are quantum.

This sounds rather reductionist. (I am not sure if all "physicists" are prone to making this mistake.) Surely, the French Revolution was not a quantum phenomenon.

Non-locality doesn't allow FTL communication. Our universe seems to obey the same laws of physics everywhere. We can speculate all day about other universes, but there's no evidence we'd ever reach them even if they do exist. If you want to figure out what things are likely you have to start with what's possible.

The physics degree can certainly reassure a person when talking about what is pretty fundamental physics. I'm surprised the irony about accusing others of being self-reassured isn't lost on you. Then again, maybe I shouldn't be surprised.

I've thought about this a bunch also. Once you start to think about say, the outside of the outside of a pilot wave...or the determination of the resonance of a string... I don't think it's fair to say the article is invalid, but it doesn't account for a lot of the more fringe areas of quantum mechanics for sure. I'm surprised you're getting downvoted.

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