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I was reading this question about if the number of stars can or cannot be infinite. The answer to this question is:

"if the universe is considered infinite, the number of stars can be infinite, otherwise not."

So, I came across a mental problem: If the universe is considered infinite, and therefore we can consider that the number of stars is too, then, we can consider that the number of humans (example) is also infinite, or the number of anything is also infinite?

If the answer is No, please describe why u think this is not a real affirmation.

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closed as off-topic by Rory Alsop, LDC3, Joan.bdm, Envite, Stan Liou Aug 5 '14 at 15:46

  • This question does not appear to be about astronomy, within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

This question appears to be off-topic because it is not about astronomy – Rory Alsop Aug 4 '14 at 21:48
I think that you are right. But an infinity of humans is a bit uncomfortable to accept. How would we make a voting list of all humans? – Nicolas Barbulesco Jun 27 '15 at 19:02

IMO, this sounds more like a philosophical question rather than an astronomical question, but since I like both subjects, I'll give it a shot.

Note: This is hypothetical question, so this answer is purely subjective (and hypothetical).


  • If the number of stars is infinite, so would the numbers of humans.

I believe that in every system where an entity of infinity is introduced, all other entities will (eventually) be infinite. But, (and this is the fun "part") you cannot measure infinity. It would give you infinite results over a time span of infinity.

Take your example for instance. If there were infinite numbers of stars. Picture youself flying around in a spaceship with the goal to find out if this question is true or not. What do you see? "Worse case" scenario; you see only stars. Wherever you go. Forever. The opposite; only humans.

One might think that it's the "in between" that is the most likely scenario. But given the probability theory, we should flatten out at approx. 50%.


If there is a finite numbers of stars then I think it's "safe" to conclude that there ain't an infinite number of humans as we're all made of starstuff.


Yes: If there's an infinite numbers of stars.

No: If there's a finite numbers of stars.

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Yeah, its a philosophical question based in a astronomical question. I like both too haha. Thanks for the answer, your conclusion was funny. – Only a Curious Mind Aug 4 '14 at 20:46
Other planets have other kinds of life. So there will be an infinite number of living beings and an infinite number of life forms but only one Earth full of humans. – what Aug 11 '14 at 19:39
@what But what if at some point we travel to another earth like planet that might be in this galaxy and then those travel to another earth like planet and so on? This will lead to an infinite number of humans in the universe if the number of stars and thus planets is infinite. – Caters Jan 28 '15 at 7:32

This is relatively an assumption so theoretically you can say Yes as you dont know if there are other planets on which life exists and there are humans on these planets. If humans on those planets exist then what is the count of those humans. So assuming that there are other planets on which humans exist you can say that there are infinite number of humans on this planet but since we only have a proof that only earth has humans so practically the number of humans on earth is countable

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but statistically speaking, if the universe is infinite and there is a chance that there are human beings on other planets, tending to infinity always exist humans in anothers planets.. – Only a Curious Mind Aug 4 '14 at 18:37
@LucasAbilidebob:- Yes that is true but in my opinion that would be a sort of an assumption considering the fact we have still not explored our own planet system! :( – R.T. Aug 4 '14 at 18:41

See this article. There are only a finite number of states the observable part of the universe can be in, therefore you will end up with an infinite number of copies of the entire visible part of the universe. And that leads to the conclusion that all histories which are not forbidden by conservation laws will occur. This means that not only are there an infinite number of copies of you, there are also an infinite number of the fictional characters that appear in soap series in sectors of the universe where the story they appear in is reality.

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is funny imagine that exists multiple copies of me. Hahaha tanks for the answer. – Only a Curious Mind Aug 5 '14 at 11:25
In this article, the essential premise is that there are a finite number of possible histories, until now, in an observable universe. I totally disagree with that. – Nicolas Barbulesco Jun 27 '15 at 19:23
There are an infinite number of possible states for our observable universe. The phenomena are continuous. It's like in maths. In the interval [0;1] there are an infinite number of real numbers. – Nicolas Barbulesco Jun 27 '15 at 19:33

There are different infinities.

You could say that there are an infinite number of planets, so probability says that there could be humans on a small percentage of them. Say for arguments sake humans exist on 0.001% of those planets.0.001% of infinity is infinity, right? Well, sort of, but it's obviously a smaller infinity than the number of planets.

Conversely there are 99.999% of planets without humans, which is a much bigger infinity.

So to all intents and purposes the answer is no, for this mental exercise.

And in reality it's a no, as any humans on other planets would pretty much have to not be humans any more, as they are so far away that unless we have instantaneous or FTL travel, evolution would have changed them/us.

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if 0.001% is still infinity, then there are infinitely many human, but an infinite smaller than the rest. :) – Only a Curious Mind Aug 4 '14 at 19:05
Lucas - that isn't how infinity works :-) – Rory Alsop Aug 4 '14 at 19:37
The kinds of numbers that answer "how many?" are called cardinal numbers--they are the generalization of counting, and include non-finite amounts. So when you say things like "it's obviously a smaller infinity" or "which is a much bigger infinity", you are mistaken, primarily because that's not how cardinal numbers work. But also because your claims are not at all obvious even if they were correct. – Stan Liou Aug 4 '14 at 23:48

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