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…)
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.
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?
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).
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.
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.
My understanding is that
I have no way of knowing this.
I think you’re misunderstanding my point in the OP… but you definitely didn’t read my follow up post.
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.
And yet it will have energy… 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?
sorry, that was ruder than I intended.
I wasn’t addressing the OP, exactly. I was bringing up how difficult this topic is to debate, as questions like this pop up.
Hard to read a simulpost. I agree with the spherical universe idea, but I still insist matter and space are fundamentally linked.
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?
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.
I’m going to deffer to you on this one, if you say that
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.
Oh, okay.
Understandably so.
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.
I haven’t noticed any reference to the 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.
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.
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.
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.
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.