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rrrADAM
Trad climber
LBMF
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Finite, yet unbounded.
It is harder to describe this with a 3D space, let alone 4D (3 spatial, 1 time), but it is easy to describe using a 2D model...
Imagine sheet of paper that is connected at two ends, forming a cyclinder or ribon. That is a "finite" space, as it has x amount of area, but it is unbounded in one direction, as if you keep going in that direction you will not come to an end.
I am of the camp that space is finite, yet unbounded.
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Dingus McGee
Social climber
Laramie
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Yes rgold,
I summarize this problem with my often repeated statement:
All Measurements are Local. Yes, in time and space.
Applying statistics to data does not produce measurements but data manipulation.
There are no true dM/dt measurements physically possible. We use a finite interval rather than an infinitesimal interval for dt.
The solution to the mass of the universe requires some type of an integral formulation. This means knowing a distribution function and we will never know this for the universe because light travels at a finite speed.
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drunkenmaster
Social climber
santa rosa
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it can and it can't at the same time - we can understand that but we can't understand how or why.
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Mike Bolte
Trad climber
Planet Earth
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its like i almost had something to say, but it wasn't quite there,
My favorite quote from this thread!
Dingus, they just gave out the Nobel Prize for measurements of the expansion rate of the Universe at z=1! Far away and long ago. Hardly a local measurement. If you respond by saying "no their telescopes and computers were right here in the near and now", I'll chuckle.
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jstan
climber
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There is growth here.
Not so much debate about whether climb X is harder than climb Y, as if we all had identical physical characteristics - which we don't.
A good part of everything around us, including ST, issued from the invention of the transistor. Giving us something better than a Marchant calculator to work with our data. I can't conceive of solving the human genome on a Marchant. Thanks to Shockley, Bardeen, and Brattain we now know a little about where we came from.
History attempts to assist us in using knowledge of where we came from to make guesses as to where we are going - the ultimate question.
I wonder. When will we get the next "transistor". What will it be?
Has it already arrived?
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Norwegian
Trad climber
Placerville, California
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Dec 10, 2011 - 07:50am PT
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anything is possible,
and nothing is substantial.
dont commit to any belief,
because all thoughts are loosely
adhered to wisdom.
the universe hyper-exhists
within your mind and mine,
but does not exhist at all
within in it's own dream.
i cannot grasp beyond the
sweaty pint of ale sliding toward
the nucleus of now,
i guess each of us
has measurable mass,
thus we gravitationally attract the earth,
in small proportion to it's pull upon us,
unless you quantify my minds and their
emotions cause they behold a
within-density
such that my internal
heat compares to that of the sun-star,
and this i'm imploding
upon my own intensity.
and shining brightly upon all of you.
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Ed Hartouni
Trad climber
Livermore, CA
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Dec 10, 2011 - 03:47pm PT
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in answer to Dingus McGee
the cosmological principle posits that everywhere in the universe is the same...
http://en.wikipedia.org/wiki/Cosmological_principle
and we assume the universality of the physical laws.
Not only that, but "all physics is local." (Though Largo might have a bone to pick with that...)
to Riley
you should stoke the morning excitement throughout the day and post on the warmth of those embers after work... unless your work is cosmology...
First off, the "Big Bang" is a singularity in time, at some time in the past the entire universe came to be, not just a point in space, but the whole nine yards.
http://en.wikipedia.org/wiki/Big_bang
The Hubble Space Telescope looks "deep" (at very faint objects), but only corresponding to 10 billion years ago. The James Webb Space Telescope will look deeper, if Congress appropriates the funds to complete and launch it.
http://en.wikipedia.org/wiki/Hubble_Space_Telescope
http://en.wikipedia.org/wiki/James_Webb_Space_Telescope
The distribution of mass in the universe does, indeed, distort the path of light. A technique that utilizes this fact is called "gravitational lensing" there are two types: strong and weak...
This technique has been used to search for brown dwarfs (a "normal matter" candidate for dark matter, eliminated by the results of the search) and in recognizing objects that are the same, just optically distorted at our vantage point by some intervening large mass.
In the future the observable universe will be "tomographed" by the lensing used to measure the large scale distribution of dark matter.
http://en.wikipedia.org/wiki/Gravitational_lens
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GDavis
Social climber
SOL CAL
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Dec 12, 2011 - 03:52pm PT
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I've been watching a lot of documentaries and man, there is nothing like some mindf*#k.
What I think is interesting is the idea that we try to put the understanding of space into our tiny, 200,000 year old human brains. We only realized gravity several hundred years ago, we can't grasp infinite laws of space and time.... we also try to fit those laws into charts and graphs when there are clear examples that refuse to fit them, like black holes and string theory. I kind of liken it to trying to measure the volume of water in a cup with a ruler, sure if all the cups are shaped the same you can get an idea but once you come up to a saucepan you need a different instrument.
Fascinating, fascinating, fascinating. The world of the infinitely large and the infinitely small. Planets made up of atoms that are thousands of times the size of ours, of nothing but molecules, no steps in between.
All space is going outward, one would think it is coming from a single point and therefore must have an end, but that's us taking our own examples to extrapolate it. Perhaps space follows a different path, bending time to be finite but unbound?
Either way, I should probably stop smoking the devils cabbage.
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throwpie
Trad climber
Berkeley
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Dec 12, 2011 - 04:07pm PT
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throwpie
Trad climber
Berkeley
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Dec 12, 2011 - 04:11pm PT
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cliffhanger
Trad climber
California
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Dec 12, 2011 - 04:57pm PT
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Richard Feynman once said that there is plenty of room at the bottom. Indeed why can it not go down forever? Atoms are made of protons, neutrons, etc which are made of quarks. And then maybe quarks are made of something smaller. And those then are made of something yet smaller. An infinite series of fundamental particles going down to the infinitely small. And maybe a trillion trillion orders of magnitude down (10^-10^24) the particles at that level contain, in the view of the vastly smaller inhabitants, vast universes. Like in the Mandelbrot set as you go smaller and smaller more, and more stuff appears forever down to infinity.
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Ed Hartouni
Trad climber
Livermore, CA
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Dec 13, 2011 - 12:12am PT
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the universe is expanding everywhere, there is no "edge" to it... where ever you are you will measure the galaxies around you receding at the Hubble constant times the proper distance to that galaxy...
as Mike Bolte suggested, think about being on the surface of a balloon as it is inflated, every point on the surface is moving away from every other point... in the balloon universe, the curvature is positive, the universe is finite but not bounded...
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bmacd
Mountain climber
100% Canadian
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Dec 13, 2011 - 12:21am PT
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Certainly this 3d presents us with puzzles, but what about another sometime place ?
Can we assume all geometric dimensions are known at this time ?
Define dimension.
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rrrADAM
Trad climber
LBMF
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Dec 14, 2011 - 11:42am PT
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Riley, there is no "edge" to the universe... The best way to explain it is like this:
Space, as we know it, (we'll leave spacetime out of this for the time being) is three dimensions, consiting of up/down, forward/back, left right (x,y,z). But it is hard, if not impossible to wrap your head around what's to follow in a physical sense, so I will use a 2 dimenional model...
Imagine the surface of a balloon, but only the surface, not the inside of the sphere, or the "space" above it. THAT is a 2D surface, just like the surface of the Earth.
On the surface of this ballon, there is no starting point or edge... If you go in one direction long enough, you will come back to where you started.
Note - I'm not going to get into the possible shapes of the universe, as it is unimportant, for the point I am trying to make.
Now, on this balloon, randomly draw a whole bunch of dots with a black marker, and randomely put one red dot and one blue dot on it.
Now if we inflate the balloon, from the perspective of the red dot, we will notice that ALL of the dots move away from the red one, AND the further out we go away from the red dot, the faster the dots are moving away... This is EXACTLY* what we see when we look into space, as galaxies further away from us are moving away faster from us than ones that are closer. THAT is Hubble's Law.
Now, one might be tempted to think that we are at the center of the universe since all objects are moving away from us, but this is where the blue dot on the ballon comes in... From the blue dot, all other dots will be moving away from it EXACTLY like they are moving away from the red dot. No matter where we put the red or blue dots, it will always be the same. This is because it is the surface of the balloon that is expanding, and the dots are just being carried with it.
What we see in the universe is because it is actually space itself that is expanding, and, like the dots on the balloon, the galaxies are being carried with it. And, just like the balloon get's larger in surface area as it inflates, the universe grows larger in size as it inflates.
But remember, in this model, we are confined to the surface of the balloon ONLY... Same thing goes with the universe, as all of space IS the universe, so while it expands, it doesn't expand "into" anything.
Now, one might also be temped to think that the galaxies may be flying away "through" space, as if from an explosion, as the do call it the Big Bang, but that's not what the term really means**. If it were galaxies flying through space as the result of an explosion, all objects would be moving at the same rate, or even slowing down the further out we go due to gravity, AND if we were to go to another dot/galaxy, we would see our neighbors (dots/galaxies) roughly moving in the same direction as us. But this ISN'T what we see... We see acceleration the further out we go, as it is space that is expanding (see Hubble's Law above).
Thus, the 2D model of our 3D universe works well to convey what is actually happening.
Make sense?
*The rate at which all galaxies move away from us isn't perfectly linear, as, for example, there are some group of galaxies that excert a gravitational influence on their neighbors, and slightly alter their movement, but it is very small. Also, dark energy/dark matter has an influence as well, where DE is posited to be the source of the accelerating expansion observed, and DM seems necessary for galaxy formation and stability.
** The term Big Bang came crom Fred Hoyle as a term of derison, as he believed in an infinate steady state universe, that wasn't expanding.
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mitchy
Trad climber
new england
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Dec 14, 2011 - 12:26pm PT
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not really sure if i just sharted or if my fart was a little juicy.
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JeffR
Trad climber
Cayucos, CA
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Dec 14, 2011 - 02:16pm PT
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According to Lewis Black, the universe is finite, and in fact he has found the end of it:
"From the time in which man first gazed at the heavens until now, the belief has been that the end of the universe exists out in space. It doesn't. It's here in the United States. And oddly enough, it is in Houston, Texas. I know, I was surprised, too. There's a comedy club there called The Laugh Stop, and if you walk to the end of the block, there sits a Starbucks. And directly across the street, in the exact same building as that Starbucks, there is...another Starbucks. There is a Starbucks across the street from a Starbucks. And, gentlemen, that is the end of the universe. People have asked me, "How do you know this?" Well, go there. Stand between those two Starbucks, and when you look at your watch, time stands still. And what's truly amazing, if you turn and look just at one Starbucks, immediately you think,"You know, when I turn around, there can't possibly be a Starbucks behind me." If there's a just and loving God, how can he allow that to happen? So you turn slowly, thinking maybe there's a McDonald's there, or possibly an Exxon station or maybe a Gap...but there's another Starbucks! Many people have asked, "Are there too many Starbucks?" Well, now we know. Yes. When you build a Starbucks across from a Starbucks, the game is over. You can build no more. What I wonder about, is the gentleman who stood in the empty building, and looked across the street at the Starbucks , and then turned to his wife and kids and said, "You know? I have a vision. I'm going to build a Starbucks right here." "Why daddy?" "Because it will be known as the end of the universe." I wonder, who are the people that would need a Starbucks across from a Starbucks. What demographic could this possibly be? I thought about it long and hard, and I mean no harm by this, but it must be a community filled with people with Alzheimer's. Who else could it be? Someone who's sitting there, drinking a cup of coffee...finishes it and walks to the door... "Oh look! A Starbucks! You know, I think it's time I had a cup of coffee."
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MH2
climber
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Dec 14, 2011 - 03:09pm PT
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I wonder, who are the people that would need a Starbucks across from a Starbucks. What demographic could this possibly be?
Bikers versus Suits if I understand correctly.
[Click to View YouTube Video]
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rrrADAM
Trad climber
LBMF
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Dec 15, 2011 - 06:37am PT
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Riley, there is no "edge" to the universe...
Spoken like a True Convert, lol.
Love ya rrrAdam but you really should learn to equivocate when it comes to things you cannot prove.
DMT
D... We also cannot "prove" that 1+1 equalled 2, one billion years ago, but we must assume that it did, since there is no reason to think it didn't.
Point being, from what we understand, which is quite a bit, and it (cosmology) can and has even been tested in many independent ways to a pretty high degree of accuracy, there is no "edge" to the universe.
(Note - A lot is coming to light recently that has changed much, but more of detail that a complete overhaul. [E.g., dark energy, dark matter])
Think about it this way... If there were an "edge", then that means that there was another dimension of space on the other side of that edge, and nothing suggests that to be the case... In fact, there is much to suggest there isn't... This is why we use the word "universe".
With the analogy of the balloon (2D), many often still think up and down, but one cannot think this way with that analogy, as the "universe" in that model has only 2 dimensions, thus adding one dimension (outside the universe) would be flawed, unless of course you had "reason" to add another dimension. Can you think of any?
This is what many do in envisioning an edge to the universe... Adding another dimension, outside the universe, from which they view the universe in their minds, and this is where they see an edge... But it is still flawed, as there is no "outside the universe".
Now, we can speculate about multiverses"...
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rgold
Trad climber
Poughkeepsie, NY
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Dec 15, 2011 - 09:50am PT
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Things are starting to repeat. The expanding balloon analogy has now been offered at least three times, for example.
As for the proper equivocation for Dingus, I think it is this. We have a certain amount of experimental data. We also have a bunch of mathematical models of space; these are based on pure logic and not on any preconceived notions of what should or shouldn't be. A number of these models are consistent with all the observations we have, and these models are all closed compact manifolds without boundary, which means that they are finite in some sense (e.g. Ed's geodesic description) and, having no boundary, do not have whatever the intuition says is an "edge." So what is certainly fair to say is that everything we know about the universe is satisfied by models that are finite in an appropriate sense and which have no "edges."
In a philosophical sense, we can never take the next step and say the universe "is" some particular manifold. Physics builds mathematical models whose logical features provide all of our observations. If new observations conflict with the logical consequences of the model, then we either have to improve the model or discard it and try to find a better one. But if we imagine, for a moment, that we have a mathematical model whose logical consequences accurately predict all observations, then we have a serious philosophical question about the extent to which the model "is" reality. That may be as much a matter of theology as anything; in any case it is not a matter of physics, if I may be so bold as to suggest to physicists what their subject is about.
The Greeks had a complex heliocentric model of the universe that accurately predicted observations like the retrograde motion of the planets. For a time, this model explained all the observations that could be made. We now know that the model bears no relation to the solar system, much less the universe, but it did its job in its time. Can we ever really ask for more?
If we actually attend to the question Jim posed which started this thread, "can the universe possibly be finite" (emphasis mine), then "yes" becomes an unequivocal answer.
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Dingus McGee
Social climber
Laramie
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Dec 15, 2011 - 10:55am PT
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rgold,
an equivocation arises from the word "universe". Just what is all that is?
We think the beginning of physics as we know it began with the Big Bang. Descriptively we sort of say the some infinitesimal region once contained all the matter-energy/space that we measure/suppose to be in this "universe". Was this (our) Big Bang simply the explosion of a collapsed (infinitesimal) super black hole exploding in some local region of the Universe?
Can the sum of all matter-energy that arose from the Big Bang just be a true vacuum fluctuation. In other words all this came from pure nothing and so it will end as such? Nothing left.
I think your ideas about compact spaces are not satisfied when we have infinitesimals.
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