# A special place in the Universe: Cosmology. **URL:** \ **Category:** Great Debates\ **Created:** [January 26, 2009, 2:48am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003 "2009-01-26T02:48:10Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Todderbob](https://avatars.discourse-cdn.com/v4/letter/t/e47774/32.png) [@Todderbob](https://boards.straightdope.com/u/Todderbob)\ **Post date:** [January 26, 2009, 2:48am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/1 "2009-01-26T02:48:10Z")
Continued from: [here](http://boards.straightdope.com/sdmb/showthread.php?t=503407). The question comes down to, basically, does Earth hold a special place in the universe? (if this isn’t the right place for this, sorry… I thought GD but then thought… I donno…) > [@Is it legitimate to say that all living things have DNA?](https://boards.straightdope.com/t/is-it-legitimate-to-say-that-all-living-things-have-dna/482849/31): > > If the Universe is infinite in size but contains a finite amount of matter, then the average density must be zero, and we living in a region where it’s not would have to be a very special region of the Universe indeed. The assumption that we occupy a special place in the Universe has had a very bad history, and it seems to go against everything that we can observe now. I don’t think that the we would have to hold a special place in the universe, in order for us to be as we are. If the universe itself is defined as the entirety of space (which is for the sake of this particular statement), then we are in a unique, but not necessarily special. It would be said that we just reside in the area which the big bang occurred. Much like a bubble is not necessarily special in a glass of coke. Our small sector of the universe (within our light-bubble) is not the limit of our inferred knowledge. We can infer that there is material beyond the observable universe by its Gravimetry (god, I feel like I just walked out of a cheap sci fi flick :smack:). I seem to recall, but can’t seem to find, an article about them detecting the pull of gravity on the most distant galaxies, based on their current (relative) speeds. Of course, I can’t find it… I’m trying, though. ETA: Just realized that reads like I think that our observable universe is the limit to the universe created at our big bang… that’s not what I meant. I meant our observable universe, including our big bang, might not be a unique thing, and even if it is it our observable universe might simply be a bubble of matter in an otherwise mostly empty universe. ---
**Author:** ![ivan\_astikov](https://avatars.discourse-cdn.com/v4/letter/i/58f4c7/32.png) [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)\ **Post date:** [January 26, 2009, 3:13am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/2 "2009-01-26T03:13:11Z")
Can I just ask for a clarification? If the universe started from a specific point in spacetime and is expanding outwards in all directions, does this mean all galaxies are moving away from each other? Only I’m sure I read something about galaxies actually colliding and combining. How would this be possible? ---
**Author:** ![Todderbob](https://avatars.discourse-cdn.com/v4/letter/t/e47774/32.png) [@Todderbob](https://boards.straightdope.com/u/Todderbob)\ **Post date:** [January 26, 2009, 3:15am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/3 "2009-01-26T03:15:38Z")
> [@ivan\_astikov](#): > > Can I just ask for a clarification? > > If the universe started from a specific point in spacetime and is expanding outwards in all directions, does this mean all galaxies are moving away from each other? Only I’m sure I read something about galaxies actually colliding and combining. How would this be possible? Galaxies do collide, due to mutual gravitational pull. In general, everything is moving away from everything else, but on a small scale this isn’t always true. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [January 26, 2009, 3:46am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/4 "2009-01-26T03:46:14Z")
At some point (not any time soon), our galaxy will collide with Andromeda. ---
**Author:** ![snailboy](https://avatars.discourse-cdn.com/v4/letter/s/97f17d/32.png) [@snailboy](https://boards.straightdope.com/u/snailboy)\ **Post date:** [January 26, 2009, 4:24am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/5 "2009-01-26T04:24:22Z")
> [@Todderbob](#): > > If the universe itself is defined as the entirety of space (which is for the sake of this particular statement), then we are in a unique, but not necessarily special. I’ve never seen the universe defined like that. It’s typically defined roughly as the matter contained in our region of space. Certain theories hold that there are multiple universes within our dimension seperated by vast expanses of empty space. So there can be finite matter in infinite space, but not finite matter in an infinite universe. If it’s finite, it has to stop somewhere. ---
**Author:** ![Todderbob](https://avatars.discourse-cdn.com/v4/letter/t/e47774/32.png) [@Todderbob](https://boards.straightdope.com/u/Todderbob)\ **Post date:** [January 26, 2009, 4:39am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/6 "2009-01-26T04:39:35Z")
> [@snailboy](#): > > I’ve never seen the universe defined like that. It’s typically defined roughly as the matter contained in our region of space. Certain theories hold that there are multiple universes within our dimension seperated by vast expanses of empty space. So there can be finite matter in infinite space, but not finite matter in an infinite universe. If it’s finite, it has to stop somewhere. If space is curved, and going in a straight line eventually gets you back to the point at which you started if you go in any direction, space is finite. That would be the Spherical Universe. If you can go in a straight line and never reach the point at which you begin, in any direction, you would, by definition, even if there is no matter **anywhere** else in the universe, be in an infinite universe. There is space, and then there is matter. They are two entirely separate measures. Matter doesn’t have to exist within a space for space to exist. Space is its own discrete thing (at least, according to most theories). ---
**Author:** ![AllWalker](https://avatars.discourse-cdn.com/v4/letter/a/db5fbb/32.png) [@AllWalker](https://boards.straightdope.com/u/AllWalker)\ **Post date:** [January 26, 2009, 4:43am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/7 "2009-01-26T04:43:48Z")
**Todderbob** , matter and spacetime are intimately bound - where you have one, you have the other\*. So having “space” outside our universe, if our universe is defined in terms of matter, doesn’t make sense. So if space is infinite, there is an infinite amount of matter. If space is finite… well, what exactly does that mean? Does space have a boundary? Is space like the surface of the Earth, curving on itself so it is finite in size but without boundaries? Is there some kind of meta-space that separates pockets of space? Or is there an infinite amount of nothingness “outside” of space, a turn of phrase which does not quite make sense. **Todderbob** , what do you mean by unique and special? Are you saying there are no other Earth-like planets, or are you saying there are no other Universe-like realities? \*vacua don’t have _no_ matter, rather they have zero matter _on average_. Brush up on your QM and GR is you want to talk cosmology. ---
**Author:** ![Todderbob](https://avatars.discourse-cdn.com/v4/letter/t/e47774/32.png) [@Todderbob](https://boards.straightdope.com/u/Todderbob)\ **Post date:** [January 26, 2009, 4:54am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/8 "2009-01-26T04:54:26Z")
> [@AllWalker](#): > > **Todderbob** , matter and spacetime are intimately bound - where you have one, you have the other\*. So having “space” outside our universe, if our universe is defined in terms of matter, doesn’t make sense. > > \*vacua don’t have _no_ matter, rather they have zero matter _on average_. Brush up on your QM and GR is you want to talk cosmology. And, that 0 matter, on average, stays that way. If there’s a vacuum, it will **always** have 0 matter on average, it will not spontaneously gain matter, which will stay. Therefore, that 0 _average_ matter will stay 0 average matter. When taken as a whole, all of space has 0 average matter, no matter how much space you have. I’m… erm… decently informed (although I’m hesitant to call myself that) in regards to QM and GR, thank you. > [@AllWalker](#): > > If space is finite… well, what exactly does that mean? Does space have a boundary? Is space like the surface of the Earth, curving on itself so it is finite in size but without boundaries? My understanding is that > [@AllWalker](#): > > Is there some kind of meta-space that separates pockets of space? I have no way of knowing this. > [@AllWalker](#): > > Or is there an infinite amount of nothingness “outside” of space, a turn of phrase which does not quite make sense. I think you’re misunderstanding my point in the OP… but you definitely didn’t read my follow up post. > [@AllWalker](#): > > **Todderbob** , what do you mean by unique and special? I’m saying that we’re _not_ necessarily unique and special, and that a (mostly) empty universe doesn’t necessarily make us unique and special, or even a universe that is nearly empty in its entirety. > [@AllWalker](#): > > Are you saying there are no other Earth-like planets, or are you saying there are no other Universe-like realities? … Neither? ---
**Author:** ![AllWalker](https://avatars.discourse-cdn.com/v4/letter/a/db5fbb/32.png) [@AllWalker](https://boards.straightdope.com/u/AllWalker)\ **Post date:** [January 26, 2009, 5:16am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/9 "2009-01-26T05:16:01Z")
> [@Todderbob](#): > > And, that 0 matter, on average, stays that way. If there’s a vacuum, it will **always** have 0 matter on average, it will not spontaneously gain matter, which will stay. Therefore, that 0 _average_ matter will stay 0 average matter. When taken as a whole, all of space has 0 average matter, no matter how much space you have. And yet it [will have energy…](http://en.wikipedia.org/wiki/Casimir_effect) quite a lot of it, too. An average of zero mass isn’t the same as zero mass, even if none of the particles which spontaneously come into being last more than a picosecond, at least according to this experiment and, from what I understand, the models. Let me ask this - is space and matter are separate, and mass is constant but space is increasing, are you saying this flux of particles should decrease in intensity with the age of the universe? > [@](#): > > I’m… erm… decently informed (although I’m hesitant to call myself that) in regards to QM and GR, thank you. sorry, that was ruder than I intended. > [@](#): > > I think you’re misunderstanding my point in the OP… I wasn’t addressing the OP, exactly. I was bringing up how difficult this topic is to debate, as questions like this pop up. > [@](#): > > but you definitely didn’t read my follow up post. Hard to read a simulpost. I agree with the spherical universe idea, but I still insist matter and space are fundamentally linked. > [@](#): > > I’m saying that we’re _not_ necessarily unique and special, and that a (mostly) empty universe doesn’t necessarily make us unique and special, or even a universe that is nearly empty in its entirety. Then I am having trouble with this part of the OP: > [@](#): > > I don’t think that the we would have to hold a special place in the universe, in order for us to be as we are. > > If the universe itself is defined as the entirety of space (which is for the sake of this particular statement), then we are in a unique, but not necessarily special. > > It would be said that we just reside in the area which the big bang occurred. Much like a bubble is not necessarily special in a glass of coke. Paragraph 1, we are not unique. Paragraph 2, we are. Paragraph 3, we are not. Little help, please? ---
**Author:** ![foolsguinea](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/foolsguinea/32/14751_2.png) [@foolsguinea](https://boards.straightdope.com/u/foolsguinea)\ **Post date:** [January 26, 2009, 5:21am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/10 "2009-01-26T05:21:51Z")
The crust/atmosphere interface of Earth, wherein we have our biosphere, is a special place in the Solar System. It has temperatures in the liquid water range, a nice pH balance, & is also a good vantage point to visually observe outer space. A unique combination. Oh, sure, there may be life-forms deep in the atmosphere of Jupiter who see in the microwave spectrum who would pooh-pooh this. But as far as we know, this is the one place where carbon based life can not only survive, but both have access to solid stone & metal for tools, AND look to the stars & see what’s out there. Outside the solar system, well it doesn’t matter, we can’t get there. Read up on Astronomical Distance sometime. ---
**Author:** ![Todderbob](https://avatars.discourse-cdn.com/v4/letter/t/e47774/32.png) [@Todderbob](https://boards.straightdope.com/u/Todderbob)\ **Post date:** [January 26, 2009, 5:31am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/11 "2009-01-26T05:31:47Z")
> [@AllWalker](#): > > And yet it [will have energy…](http://en.wikipedia.org/wiki/Casimir_effect) quite a lot of it, too. An average of zero mass isn’t the same as zero mass, even if none of the particles which spontaneously come into being last more than a picosecond, at least according to this experiment and, from what I understand, the models. > > Let me ask this - is space and matter are separate, and mass is constant but space is increasing, are you saying this flux of particles should decrease in intensity with the age of the universe? I’m going to deffer to you on this one, if you say that > [@AllWalker](#): > > sorry, that was ruder than I intended. I didn’t take it as rude. I figured you meant it the way it sounded. I try not to take offense to internet posts, because it is difficult to convey meaning. And… I only have a passing understand of GR/QM anyway, so I really do need to brush up. I was trying to be psuedo-snarky, without actually being rude. I didn’t mean my side of the conversation offensively, either. > [@AllWalker](#): > > I wasn’t addressing the OP, exactly. I was bringing up how difficult this topic is to debate, as questions like this pop up. Oh, okay. > [@AllWalker](#): > > Hard to read a simulpost. I agree with the spherical universe idea, but I still insist matter and space are fundamentally linked. Understandably so. > [@AllWalker](#): > > My understanding is that Then I am having trouble with this part of the OP: > Paragraph 1, we are not unique. Paragraph 2, we are. Paragraph 3, we are not. Little help, please? That’s because I’m a man rife with contradictions! And, it’s just poorly phrased. We may be out of the norm, but still not unique or special. I should not have used unique, because that, by definition, means one-of-a-kind. I should’ve said said that we may be a one-off, and still not be unique. Sorry, that’s just me… poorly phrasing. ---
**Author:** ![Staggerlee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/staggerlee/32/3134_2.png) [@Staggerlee](https://boards.straightdope.com/u/Staggerlee)\ **Post date:** [January 26, 2009, 10:14am UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/12 "2009-01-26T10:14:53Z")
> [@Todderbob](#): > > I don’t think that the we would have to hold a special place in the universe, in order for us to be as we are. > > If the universe itself is defined as the entirety of space (which is for the sake of this particular statement), then we are in a unique, but not necessarily special. > > It would be said that we just reside in the area which the big bang occurred. Much like a bubble is not necessarily special in a glass of coke. I haven’t noticed any reference to the Anthropic Principle [http://en.wikipedia.org/wiki/Anthropic\_principle](http://en.wikipedia.org/wiki/Anthropic_principle) - apologies if I missed it. The principle suggests that life on Earth formed under very \*particular \*(if not ‘special’) conditions. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [January 26, 2009, 12:40pm UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/13 "2009-01-26T12:40:04Z")
Moving thread from IMHO to Great Debates. ---
**Author:** ![Henrichek](https://avatars.discourse-cdn.com/v4/letter/h/5daacb/32.png) [@Henrichek](https://boards.straightdope.com/u/Henrichek)\ **Post date:** [January 26, 2009, 2:16pm UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/14 "2009-01-26T14:16:39Z")
> [@Todderbob](#): > > In general, everything is moving away from everything else, but on a small scale this isn’t always true. Galaxies being referred to as small scale really makes me feel insignificant :dubious:. ---
**Author:** ![Walker\_in\_Eternity](https://avatars.discourse-cdn.com/v4/letter/w/46a35a/32.png) [@Walker\_in\_Eternity](https://boards.straightdope.com/u/Walker_in_Eternity)\ **Post date:** [January 26, 2009, 2:48pm UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/15 "2009-01-26T14:48:38Z")
> [@AllWalker](#): > > **Todderbob** , matter and spacetime are intimately bound - where you have one, you have the other\*. So having “space” outside our universe, if our universe is defined in terms of matter, doesn’t make sense. In terms of our universe that is true, but the solutions to general relativity can describe universes without matter such as the [De\_Sitter\_universe](http://en.wikipedia.org/wiki/De_Sitter_universe). ---
**Author:** ![Walker\_in\_Eternity](https://avatars.discourse-cdn.com/v4/letter/w/46a35a/32.png) [@Walker\_in\_Eternity](https://boards.straightdope.com/u/Walker_in_Eternity)\ **Post date:** [January 26, 2009, 2:51pm UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/16 "2009-01-26T14:51:15Z")
> [@panache45](#): > > At some point (not any time soon), our galaxy will collide with Andromeda. But as the Mily Way is bigger than previously thought and is moving roughly 15% faster we will hit Andromeda sooner than originally expected. Although it will still take billions of years. [Cite](http://news.bbc.co.uk/1/hi/sci/tech/7813635.stm) ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [January 26, 2009, 3:06pm UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/17 "2009-01-26T15:06:24Z")
> [@Todderbob](#): > > Our small sector of the universe (within our light-bubble) is not the limit of our inferred knowledge. We can infer that there is material beyond the observable universe by its Gravimetry (god, I feel like I just walked out of a cheap sci fi flick :smack:). I seem to recall, but can’t seem to find, an article about them detecting the pull of gravity on the most distant galaxies, based on their current (relative) speeds. Of course, I can’t find it… I’m trying, though. I don’t really have time to read the thread in detail right now, but I believe you’re thinking about what’s been dubbed [dark flow](http://en.wikipedia.org/wiki/Dark_flow). ---
**Author:** ![Whack-a-Mole](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/whack-a-mole/32/141_2.png) [@Whack-a-Mole](https://boards.straightdope.com/u/Whack-a-Mole)\ **Post date:** [January 26, 2009, 3:20pm UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/18 "2009-01-26T15:20:19Z")
The OP is presuming an infinite universe. Thing is it is not infinite. It can’t be since it had a definite beginning and only a finite amount of time to expand. Anything “outside” of our universe, if there is such a thing, cannot reasonably be talked about. You could say it is all peanut butter outside our universe and it’d be as correct as anything else you could say about it. Also, our universe is not believed to be spherical. The best evidence so far ([from WMAP measurements of the cosmic microwave background](http://map.gsfc.nasa.gov/universe/uni_shape.html)) is that the geometry of the universe is flat, like a sheet of paper. So, you will not come back to where you started if you travel in a straight line. Thing is space is expanding at faster than light speed so you cannot reach the “edge” either no matter how fast you go. There is no “special” place in the universe either. Wherever you go the universe will look pretty much the same in all directions. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [January 26, 2009, 5:20pm UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/19 "2009-01-26T17:20:36Z")
> [@Todderbob](#): > > Continued from: [here](http://boards.straightdope.com/sdmb/showthread.php?t=503407). > > The question comes down to, basically, does Earth hold a special place in the universe? > If the universe itself is defined as the entirety of space (which is for the sake of this particular statement), then we are in a unique, but not necessarily special. > > It would be said that we just reside in the area which the big bang occurred. Much like a bubble is not necessarily special in a glass of coke. I take the Universe in the quote as being our universe, since we can’t say anything about the meta universe. We can’t even meaningfully talk about volume, and thus density, where there is no space. The problem with the quote is that the density of our universe is not 0, but close to 0, which is a big difference. The implication is that locally the density must be the average density, which is clearly not the case. Lumpiness in the universe a few seconds after the Big Bang meant that there were lumps of matter, and gravity took over from there making some small areas of the universe very dense. I think the application of the anthropic principle that **Staggerlee** mentioned is that intelligent life only arises in areas of higher than average density, so finding such areas nearby should not be surprising. Of course “special” is a loaded word, and if anyone wants to feel special, be my guest. But I agree with you that where we live is not all that unusual. ---
**Author:** ![Todderbob](https://avatars.discourse-cdn.com/v4/letter/t/e47774/32.png) [@Todderbob](https://boards.straightdope.com/u/Todderbob)\ **Post date:** [January 26, 2009, 5:57pm UTC](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003/20 "2009-01-26T17:57:18Z")
> [@Whack-a-Mole](#): > > The OP is presuming an infinite universe. I am most definitely not. From the other thread: > [@Is it legitimate to say that all living things have DNA?](https://boards.straightdope.com/t/is-it-legitimate-to-say-that-all-living-things-have-dna/482849/27): > > I tried to edit in the following, but missed my deadline. > > ETA: There are 4 possibilities. (I won’t go into the specifics of each theory, just the overall basics of what they are.) > > A1. A2. B1. B2. > > A) The universe is of infinite size. > > B) The universe is of finite size. > > 1. The universe contains an infinite amount of matter. > > 2. The universe contains a finite amount of matter. > A1: This is internally consistent, though difficult for me to believe, mathematically speaking. > > A2: This is internally consistent as well, and would lead to a ‘big rip,’ eventually. Because we do know that the universe is – or has so far been --expanding (See: [The Metric Expansion of Space](http://en.wikipedia.org/wiki/Metric_expansion_of_space)). > > B1: This is internally inconsistent and difficult for me to believe, because for an infinite amount of material of material to reside in a finite space, it would have to be infinitely dense… and… that’s just not how the universe seems to me. > > B2. This is the theory I lean towards, because it’s internally consistent and it seems to account, best, for what we observe in the universe. The universe has a finite, if undefined, size, and a finite, if undefined amount of matter. [Next page](https://boards.straightdope.com/t/a-special-place-in-the-universe-cosmology/483003.md?page=2)