Live data from Hacker News

Can a Living Creature Be as Big as a Galaxy?

nautil.us

71–80 of 204 posts

Re: Can a Living Creature Be as Big as a Galaxy?

#71
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?

Re: Can a Living Creature Be as Big as a Galaxy?

#72
post #63

Earlier quoted context omitted.

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.

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.

Re: Can a Living Creature Be as Big as a Galaxy?

#73
post #64
post #62

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…

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.

Re: Can a Living Creature Be as Big as a Galaxy?

#74
post #64
post #62

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…

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.

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".

Re: Can a Living Creature Be as Big as a Galaxy?

#75
post #64

Earlier quoted context omitted.

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 survi…

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".

Re: Can a Living Creature Be as Big as a Galaxy?

#76
post #9
post #2

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.

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?

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

Re: Can a Living Creature Be as Big as a Galaxy?

#78
post #64

Earlier quoted context omitted.

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 survi…

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").

Re: Can a Living Creature Be as Big as a Galaxy?

#79
post #50

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 observi…

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.

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...

Re: Can a Living Creature Be as Big as a Galaxy?

#80
post #75

Earlier quoted context omitted.

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 survi…

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…

> 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.

Post reply on HN