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MH2
climber
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I dunno, both infinities and infinitesimals have been used in productive ways. Just a question of asking, "What happens if...?"
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Tony Bird
climber
Northridge, CA
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Then again.....can it be infinite? Either possibility boggles the imagination.
snap answer, buddy. the universe is indeed a big mofo, but it's either expanding or contracting. if it's expanding, it will either expand beyond the point of no return, or it will reach equilibrium and begin to contract. if it ultimately contracts to collapse, think reverse big bang. this is called a singularity. physicists dare not predict what'll happen if that happens ("the laws of physics break down, blah, blah, blah ..."), but i would venture it'll be like a pogo stick, bouncing back again with another big bang. just a hunch. then we gots more spacetime to evolve stuff again, and, hopefully, be able to make war, as we're all meant to do.
now, if it expands beyond the point of no return, that's another story. second law of thermodynamics wins, our progeny will have to sit around and wait for heat death, entropy beats cyclicality. don't worry, it'll be long after locker's hallowed prediction* comes true for us and even our great-great-grandchildren, if anyone lives long enough to see one.
however, if everyone realizes the key to universal salvation is praying the rosary and does that, nothing bad will happen and i'll bet god will clue us in on the real basics of it all--after ... *.
*you know this.
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Ed Hartouni
Trad climber
Livermore, CA
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Riley Wyna sez: How the heck do you weigh the universe?
That's a ridiculous statement.
I'll reply later, it's not so ridiculous. But also probably not as grand as you imagine.
Also, it is easy to dismiss something you don't agree with because you don't understand the language it is expressed in. Mathematics affords a precise language with which to describe observations, and to deduce or infer relationships that allow us to predict the outcome of an experiment or an observation.
Math does not "lie."
You can also wind yourself up in knots worrying about truth and proof and such... and forget that our scientific understanding of the universe is provisional, but that it is consistent with our observations, and there are many observations. You can have an opinion, but you might want it to be a bit more informed than your own sensibilities before you go spewing...
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WBraun
climber
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I have to go along with Ed that our Universe is finite.
I have to go along with the view that we can not go beyond it, but that only applies to our present material bodies.
The only way to escape the material universe is in our true spiritual body which is now in this material universe covered by the material elements.
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nature
climber
Aridzona for now Denver.... here I come...
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it's an infinite multiverse.
and I even know where the center is.
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Tony Bird
climber
Northridge, CA
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they had the weight of the universe pretty much figured up--one of those 10 to the googolplexth power deals. then someone discovered dark matter. they've got it pretty much refigured now, but they're just starting to discover spew.
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Captain...or Skully
climber
Where are you bound?
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Uh, it's "slain", not "slayed". Not a Nazi, I just love the language & detest its mangling.
What is wrong with infinity? I like Werner's infinity, too, for it puts infinity within infinity. Beautiful.
Have a nice day.
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steveA
Trad climber
bedford,massachusetts
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Jim
You opened up a can of worms here.
I'm sure, even the caveman thought of this.
You two have fun down there!
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Ed Hartouni
Trad climber
Livermore, CA
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On Weighing the Universe, which might seem so much non-sense to some... apparently...
First off, you can look at the universe and just count everything you see to get the approximate number of stars, then multiply the number of stars by the average stellar mass... you need to estimate the size of the universe you could see, and then count the stars in the area you can see and adjust to take into account the unseen bits. This is described here:
http://www.grc.nasa.gov/WWW/K-12/Numbers/Math/documents/ON_the_EXPANSION_of_the_UNIVERSE.pdf
Bottom line is that we can't see past 13 billion light years, the Hubble telescope lets us see back to 10 billion light years, so we can see about 75% out to the limit. Counting the number of stars gives about 5E+21, taking this all together gives about 1E-9 stars per cubic light year, and a total of about 1E+22 stars.
The total mass, assuming something like 3E+30 kg per star, to be 3E+52 kg. The total volume of what we can see translates to 4E+80 m^3 and a density of 7.5E-29 kg/m^3
Since we have measured that the universe is "flat," we can calculate the critical density which turns out to be 9.3E-27 kg/m^3, or a mass of about 4E+54 kg, which is a lot larger than what is in stars alone. Observations reveal that only about 10% of the atoms in the visible universe are in stars, so it isn't quite as bad, but still, the visible universe only represents less than 10% of the total mass of the universe.
How do you "see" the other stuff?
It has gravity. First, Fred Zwicky argued, back in 1934, that the distribution of star velocities around the center of mass of galaxies didn't match the visible mass and our understanding of Newtonian gravity. There was a need for more mass and a different distribution. Later observations also looked for and found the "lensing" effect that matter exerts through its gravity on light, bending it... so you can look for the out-of-focus images of the stuff behind the mass to map out its location.
But wait, there's more! Observations of far away supernova indicate that the expansion of the universe is changing, and getting faster... the reason: dark energy... called it "vacuum energy" above (I think, but maybe I left that out...). In the modern cosmology, the so called Lambda-CGM model this stuff, what ever it is, represents roughly 73% of the total mass of the universe, the dark matter is 23% and our stuff is 4% as much as it is.
Mostly this is the consequence of General Relativity and some well motivated assumptions, like the "cosmological principle". And the ramifications of the predictions of this model will dominate physics for decades to come.
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rgold
Trad climber
Poughkeepsie, NY
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I'm no cosmologist, nor any kind of physicist, just a lowly mathematician, a member of the priesthood in charge of the definitions (but please---this is far from our only job). In that capacity, it is my sad duty to report that the use of the word "finite" in this discussion appears to be subject to various, sometimes conflicting assumptions, so that it is not clear what we are actually speaking about here.
Ed seems to be using "finite" to mean "finite volume." I have to say that he seems to be begging the question by saying essentially, that if we assume the universe has finite volume, then we can calculate it. If this is true, a calculation based on the assumption of finite volume can hardly be used to prove the volume is finite, but I've probably misunderstood something here; most likely that finite volume is not an assumption but rather a consequence of some other cosmological "fact," probably the big bang, and the "weighing of the universe" is not the fact that proves "finiteness." In any case, as some of you may remember from your calculus courses, there are solids of infinite extent with finite volume, so even a bona fide calculation of finite volume wouldn't, by itself, prove that the universe is finite.
Some of what has been written seems to suggest that "finite" means the universe is bounded, meaning that there is, at least at any one moment in time, a constant that is greater than the distance between any two points in the universe. (There are, I think, relativistic problems with the concept of "any one moment in time," so that the condition of boundedness, given that the universe is expanding, probably requires a more sophisticated statement than I've provided. And the question of distance itself is problematic...)
Being bounded may not capture the sense of finiteness people have in mind, however. A hypothetical microbe confined to live on the line strictly between 0 and 1 lives in a bounded space, but can never reach the boundary points, since they are not part of the microbe's universe, and so experiences its world as infinite, whatever we might think from the outside. Mathematically, one is obliged to eliminate such possibilities by insisting that the universe be closed as well as bounded if it is to be "finite," where closed means, roughly, that any point you seem to be approaching really is there (unlike the 0 and 1 of the open interval above). Skipping over various niceties, the appropriate term for closed and bounded is compact, and I think that this is perhaps what most people mean when they speak of the universe being finite.
But compactness does not necessarily have the kinds of properties that make people think there is something "wrong" with the universe being "finite." Most particularly, compact, and therefore finite, does not mean that if you travel "far enough" you will bump into some fence at the end of the property, with dragons and other unmentionables beyond. The universe can be closed and bounded without having a boundary, which is a different concept. Perhaps the best and oft-cited example, which includes the expansion and isotropy of the universe (but not its apparent "flatness") is the two-dimensional analogy with the surface of an expanding balloon. If our hypothetical microbe lives entirely within that surface, it resides in a compact expanding universe. Everything in that universe appears to be moving away from everything else, no matter what point the observing microbe occupies. But there is no boundary to bump into after extended travel, no fence separating the universe from anything else. The one thing that is true, as Ed mentioned, is that extended travel in what the microbe thinks is a straight line, but which we recognize as a great circle, ultimately brings it back to its starting point.
A mathematical reality that is hard for us to visualize is that these spaces can have intrinsic existences, they do not have to be embedded, as the balloon is, in something bigger, namely our "ordinary" three-dimensional Euclidean space. The surface of the balloon can be all there is, so that there is not only no "boundary" to be approached or breached, but also there is nothing "outside" that universe at all.
I mention all this primarily to point out that when one starts to pin down what "finite" really means, it ceases to become a difficult to imagine it as a possibility.
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WBraun
climber
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How do you "see" the other stuff?
This will probably be too simple for anyone here to "see" (understand).
When chic breaks out of the egg shell .......
The egg shell being the finite universe.
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Dr.Sprock
Boulder climber
I'm James Brown, Bi-atch!
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it is finite, we are bordered on six sides by el capitan.
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its like i almost had something to say, but it wasn't quite there,
maybe a little more weed?
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Ed Hartouni
Trad climber
Livermore, CA
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don't stand by your statement,
explain it...
you think it is ridiculous but that's all you've said, really, why?
you have blown this stuff out of proportion, and think that scientists are arrogant where they are just putting the pieces together over the last century of observation and experimentation, lots of little pieces that fit into a bigger picture
you might dismiss it as all a big error, but you should show just what that house of cards rests on, and why it will topple so easily
if you are informed, and you obviously have strong opinions, you might help out the thread telling about the basis of those opinions.
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Ed Hartouni
Trad climber
Livermore, CA
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rgold... I thought the description of "infinite" and "finite" with the apple example up thread was clear and simple, maybe not...
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Dr.Sprock
Boulder climber
I'm James Brown, Bi-atch!
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ok brainiac, what was the first planet discovered by telescope?
clue: think anatomy,
how many ridges on a dime?
126, or 129?
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Karl Baba
Trad climber
Yosemite, Ca
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If the definition of Infinite and Finite is too limited, the answers will just make an ignorant box for us to live in.
We have NO IDEA at this point in human Evolution. Science suspects multiple universes, Spirituality suggests the physical universe to be a small subset of existence, and even "finite and Infinite" are seen relative to each other and our human perspective. How to account for the unknown in our speculations?
The Truth is way beyond our minds, even though we can go way far out with that
Peace
Karl
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Dr.Sprock
Boulder climber
I'm James Brown, Bi-atch!
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the universe has to be infinite, otherwise, where would you put all the sewage?
it would build up after a while,
we would be swimming in our own sh#t,
no wait, we already are, anti politics,
oh man, i gotta drop a deuce.
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rgold
Trad climber
Poughkeepsie, NY
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I thought the description of "infinite" and "finite" with the apple example up thread was clear and simple, maybe not...
Clear and simple, yes, although perhaps one needs to add something about the return of the apple being eventual, that we don't know how long that "eventual" might be, and so when the apple, having been tossed at escape velocity, doesn't return, we don't know whether it never will or whether we have to wait longer.
Beyond that, the definition in terms of closed geodesics is a way from intuitions of finiteness, which means, in a discussion like this, that it can comfortably coexist with various misapprehensions, some of which I attempted to clarify.
Finally, the connection between the closed geodesics definition and the weight of the universe argument for finiteness, if that's what it was, surely involves a collection of inferences not present here.
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eeyonkee
Trad climber
Golden, CO
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Finite. Got any tougher questions for us?
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