Sorry, I guess I didn't finish the thought - nice recovery.

Better try not to think of those 10 dimensions too much, or you might wind up like these folks:

ABBA DABBA KABALLA


www.crystalinks.com/superstrings.html+CRYSTALINKS+STRING+THEORY+10+DIM ENSIONS&hl=en&ie=UTF-8]WOO WOO[/url]


www.ransom.co.uk/universe/press_12.htm+magic+string+theory+ten+dimensions&am p;hl=en&ie=UTF-8]MAGIC SCIENCE AT PRINCETON[/url]

Comparing M theory with Kaballistic string theory is like comparing astronomy to astrology, only moreso. M theory (and BTW, the M doesn't really stand for "magic;" it doesn't really stand for anything) is an attempt to merge five differnt types of superstring theory into one completely self-consistant theory. Nothing more odd than "standard" superstring theory. When people start trying to use string theory to justify the Genesis account of creation, however...let's just say they make you look like a main-stream thinker.

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"Nobody understands quantum physics." -- Richard Feynman

"So, does quantum physics predict circular orbits for electrons?" -- Student in my Intro to Quantum class

Showing that Feynman was especially correct about some individuals.

Oh? Why don’t we just ask a ghost to answer all our questions before we ask them? Or maybe we could go to a palm reader and she could tell us the answers before we even think up the questions. I think she would cost only about $5 per question.

Yes, I can definitely see a future for magic in physics.

Hey Sam5--

You asked earlier in the thread for "commonsense explanations." THen you go on to say that there are no scientific papers discussing the expansion (observed) of the universe. Let's get into a couple of things here.

First, space "expands" but it isn't like blowing up a balloon where you add something. It isn't just a mystery of nature either. The best analogy I can come up with is a rubber band -- you don't add anything to the band when you stretch it, but it is longer. Space, not being made of anything material, behaves in a similar fashion. But this is an analogy, NOT the thing itself.

Originally, Einstein and his colleagues thought the universe was static. But the implications of relativity were for a finite univese. This is quite aside frmo the Olbers' paradox observation, which says that the universe can't be infinite becuase if it was the sky would not be dark. (You would eventually see a star in every direction, and since an infinite universe immplies an infinite age, the light from infinitely far away stars has time to reach you, unless you posit an infinite universe of finite age, but then you run into problems explaining that).

The expansion of space is a function, in part, of all those virtual particles that pop in and out of existence. In one sense, the quantum foam that makes up space is coming from there. But again, that is a very rough way of putting it.

Yes, quantum physics says things that don't jibe with common sense, as does relativity. But they WORK. You are using a computer that would not function AT ALL if quantum tuneling did not happen (there would be no semiconductors, which are essential to any computer smaller than a room). Digital displays work. Redshifts in distant galaxies are observed, and the predicted observations from explanations that do NOT include universal expansion of some kind or other did not work. That is, the prediction (a mark of a real theory) did not test out. Now, it is possible that somethign is going on that we can't observe for whatever reason, but that puts it riht out of the realm of science unless you can come up with an experiment to falsify the theory involved.

So, if the universe was not expanding, one would expect redshifts and blue shifts to be randomly distributed. They aren't.

If the expansion was thought up to save relativity, and just a methematical convenience, one would have to come up with a more compelling explanation. There have been a few, but they too failed to produce confirming observations. (Like theories that require an ether).

If there were no space curvature, then Newton's mechanics would have been perfectly accurate, given the better instruments we have now to test that theory at more extreme conditions than he could. Again, no dice.

It is almost like you have thins thing that all scientists must be fools because the theories they propose and test don't confirm to a world view that is "common sense." Electricity didn't fit that bill either for some people, who philosophically objected to the idea of atoms. Well, Maxwell and atomic theory work. Oh well.

-J

Well, when you stretch the rubber band, you are expanding or “thinning out” its “fields”, whatever fields there are that hold the molecules of the rubber band together. “Space” is just the place where you stretch the rubber band.

I suspect this happens in deep space when the galaxies spread apart, i.e. the “thinning out” of the galaxies’ gravitational fields as they spread apart. “Space” is just the place where this “thinning out” occurs. So it is not “space” that “expands”, the fields become “thinner” or “weaker” in the area of space in-between the galaxies as they separate. So, the real expression should not be an “expansion of space”, but a “weakening of the gravitational fields in-between the galaxies” or an “expansion of the gravitational fields” or a “thinning out of the gravitational fields”.

This would match observation, it would make sense, and it would NOT be “counter-intuitive”.

No, the expansion was not “thought up to save relativity”. That’s not what I’m saying. The switch-over in terms occurred mainly in the 1990s, from “big bang” and “moving galaxies” to “expanding space” and “non-moving galaxies being carried along by expanding space”, and I say the switch-over in terms was designed to salvage and save the “c speed limit” of SR theory, AFTER the superluminal (faster than “c”) galaxies were discovered.

Look, if you run away from me at 5 mph, I can say you are “moving away from me at 5 mph”. Also, if you get in a car and the car drives you away from me at 5 mph, I can still say you are “moving away from me at 5 mph”. So, it doesn’t matter HOW the galaxies are “moving,” away from us at faster than “c”, they are still “moving away from us at faster than c”, whether “space is expanding” or not. But some cosmologists think this violates Einstein’s “speed limit of c”, so they don’t like it. They are afraid to “violate” anything Einstein said, even if what he said turned out to be wrong.

But, this might NOT violate the “speed limit of c” if the galaxies are not moving through any fields. The “speed limit” is actually based on Lorentz theory of the motion of atoms “through fields”, not the motion of atoms “through empty space”. So, “c” might still be a “speed limit” for atoms moving through fields, such as gravitational fields, but the distant galaxies might not be moving through fields.

Ummm... you do realise that *EVERYTHING* is always moving through a gravitational field, right? Any galaxy, however distant, creates a gravitational field by virtue of its mass so at very least it's smack in the middle of its own gravitational field. Moreover, *every other piece of matter in the universe* is creating a gravitational field that is, in some way, affecting every other piece of matter in the universe. It's impossible *not* to be travelling through a gravitational field.

OMFG sam you are so annoying

Classic Sam5-ism, join a debate, make an incorrect supposition, and then argue about definitions of words to try and make yourself seem right.

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<3

This can't be right because it is actually the opposite of what is observed. Judging from the way the galaxies are moving, there is more gravity in between galaxies than we can account for by summing the known mass.

No, I think the reason is more fundamental than that, and I think it derives from the observed fact that the the farther away an object is, the higher its redshift and therefore the larger its apparent recessional velocity. Why should this be so if all objects in the universe are just streaming "outward" through space? Why should more distant objects be moving away from us faster? Is there any explanation for this?

But if it's space that is expanding, this easily explains why more distant objects appear to be moving away at proportionately greater rates.

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Everyone is entitled to his own opinion, but not his own facts.

Well that doesn’t matter. Whatever the gravity strength is of the masses and in-between the masses, if the masses move apart the gravity strength between the masses becomes weaker.


Yes, a very simple one.

If you look at any video or old film of an explosion, you’ll see the outer most particles moving faster than the innermost particles. If you put one pound of explosives in a hole 3 feet deep, and set of the explosive, you will see a semi-circle of debris particles move upward from the point of the explosion, and the outermost particles will move faster than the innermost. Some of the particles nearest to the explosion will move only an inch or two. You can see this phenomenon in a simple spherical star-burst fireworks explosion, like this one. The outermost dots are where they are because they moved faster than the innermost dots. This is why the “big bang” was described as a kind of “explosion” for 65 years. This is why Eddington called Lemaitre’s 1927 big bang theory a “fireworks” model.

OK, but if that's the case, then the earth would be positioned right at the center of the big bang, since this Hubble law phenomenon is happening no matter which way we look. Why should our dinky little planet be at the center of everything? Considering the number of other stars and galaxies, the theory folds under the weight of its own coincidence.

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Everyone is entitled to his own opinion, but not his own facts.

No, not necessarily. This is apparently what the astronomers first thought when the BB theory was first accepted and this is why Eddington invented the “expanding balloon” model. The astronomers literally didn’t want the religious folks to get hold of the “apparent center” information, since a visually apparent “central position” would be too “Biblical” for the astronomers to accept.

But, if you do some diagrams on graph paper or if you do some vector analysis equations, you’ll find that we would see the same thing if we were way out in the middle areas of the “expansion”.

We don’t have to be in the center in order to see all the galaxies expanding away from us, just as we don't have to be in the center of our own galaxy in order to see stars on all sides of us or the Milky Way encircling us. In fact, Herschel thought we were in the “center” of a “circular” universe. He thought the Milky Way was the whole universe, and since it circles the earth, he thought we were in the center of the universe. But that turned out to be wrong. We turned out to be way out near the edge of our galaxy, not anywhere near the center at all.

If you look at some of the inner dots in the fireworks picture, they see exactly what we see, i.e. “redshifts” of the other dots in all directions.

Now, there would be a “sideways” motion of some of the galaxies, if we were way out away from the center, but we can’t measure the sideways motion since it is so slight from our point of view. We could go hundreds of years and compare photos from now and from hundreds of years from now and notice no “sideways” motion of the distant galaxies. All we can see is their redshifts which reveals their radial motion.

The universe could have a center, but we don’t necessarily have to be in it.

But even if you take the “expanding space” point of view, that doesn’t get us out of the “center”. We’ve looked like we were in the “center” from the very beginning of the Big Bang theory.

Astronomers who say that they have “seen out to the very edge of the universe and back to within 5% of the beginning of the bb,” they are placing us in the “center”, since they claim they can see this “5%” in all directions of the sky. That puts us within 95% of the center.

However, I think the universe is much larger than they think it is. I think their “age of the universe” estimates are not correct, and I think the “inflation model” is wrong. The inflation model has the galaxies suddenly speeding up to almost an infinite speed, early on, and then suddenly slowing down again. I think that’s silly.

Look at it this way: We are in the “center” of our “sphere of visibility”, but that doesn’t mean we are in the “center” of the entire universe. It only means that our “radius of visibility” only goes so far, and the “radius of the universe” is much larger than our “radius of visibility”.

Well exactly. Space might even be infinite and we are always in the center of the visible universe, since the speed of light is constant. But we couldn't see a recession speed that is a function of merely the distance of a galaxe unless space is uniformly expanding. If there was a center, recession speed would depend also on the angle between the direction of the object and the direction of the center.

How do you figure that? What assumptions are you making?

I assumed Sam5's three dimensional explosion model which he so often illustrates. I also assumed that it would progress in a fashion that everything doubles its distance to the center in the same amount of time. And there I was wrong: As far as I can see this is just the big bang expanding space model with an arbitrarily chosen "center" (more of a viewpoint transformation, the center can be put anywhere).

Putting a real center into this model of course necessitates rapid acceleration. Every time an object doubles its distance from the center, it also has to double its speed. This doesn't work so good.

However, it does work with constant speeds that were set at the time of the big bang as far as I can figure. Problem with that is that in order for the universe to look uniform in every direction, the higher the speed the more likely any given particle would have to have it in order to fill the volumes that are expanding by the cube of the distance from the center. That, or I'm just confused now. 8-[

No.

Let’s say you have 3 guys in a line. Then they start moving forward. The guy out front runs at 5 mph. The next guy runs at 2.5 mph. The third guy walks at 1 mph.

So they are “expanding apart” with no increase in speed. 1 year from now, they will be very far apart, but with no increase in their original speed. Their starting point is the “center”. You can do this with several lines of guys, all radiating out from that same starting point in all directions.

I think the BA explains it pretty well in his book--all the world's a stage, and all the universe is a movie theater.

He imagines you sitting in a movie theater, and pressing a button, and all the seats move one meter apart. The seats farthest away would be moving faster, and they all would appear to be moving away from you. You could change seats, and it would still look that way.

Oh sure, I have no problem with understanding the expansion of space. I was thinking about whether other types of expansion like Sam5's explosion would look the same to the observer (one that isn't in the center).

For a constant speed expansion (initial impulse given at the "explosion") I figure they would... geometrically, in an Euclidian space. I'm not sure how exactly the low speed of light would mess with the observations. Plus there's still the problem that higher speeds would have to be more common than lower speeds to result in the observed homogenous distribution of matter.

You mean the higher speeds of the galaxies farthest from the earth?

I don’t think that would be a problem if we consider that they are probably not moving “through” fields.

Personally, I think the Lorentz “c” speed limit applies only to matter moving through strong fields, such as here at the surface of the earth. But if the distant galaxies and groups of galaxies are not moving through any other galaxies’ gravity fields, then the “c” limit might not apply at all.

One problem we’ve always had is that we are really little and our telescopes have always been limited in size, so we just can’t see very far into what I think is a very large universe.

If this big bang as exploding firework model is to have any validity, it needs to explain a couple of things.
•Why don't we see a central void? When something explodes, the debris cloud starts out spherical, but after a little time has passed, you always get an expanding shell of material around a central void, rather like a planetary nebula. If the universe contains such a void, it should be pretty easy to find.
•Why isn't there a large difference in the apparent size of galaxies, at the same redshift, on different sides of the sky? On this side of the explosion, everything is moving in the same outward direction as us, but the redshift for galaxies on the opposite side of the explosion would be due to the sum of our outward velocity, and the outward velocity of the distant galaxies. Without some serious kludgery, that'd require the redshift vs distance equation to be highly assymetric. AFAIK, it's not.

There are different kinds of explosions. An atomic bomb explosion tends to send out a “bubble” or a “thin shell” of a shock wave. But there is another kind that is like an explosion in a pile of dirt or sand. That kind sends out particles in all directions, with the central stuff not moving too much at all and the outer stuff moving the fastest. But this is only speculation, which originally was based on the idea that if the galaxies are moving apart now, they must have been closer together in the past and maybe very close together in the distant past.

But no one really knows what happened or why the galaxies are moving (or appear to be moving). If our universe is bigger than suspected, the “center” could be so far away from us we might not be able to see it.

If the “explosion” was really uniform and the universe bigger than we think, then we would see what we see, but we wouldn’t have to be near the center at all.

One reason astronomers were able to detect our position in our own galaxy was because of the “sideways” motion of some of the distant stars (I think that’s the way to explain it). But, the problem with detecting any “sideways” motion of any of the distant redshifted galaxies is because they are so far away, a slight “sideways” motion is just too small to be noticed.

Newton offered a third alternative to the 1) collapsing or 2) expanding list of possibilities. He said the entire universe might be revolving, something like the way our solar system works. Well, if it’s revolving, it would have to be somewhat overall “flat” shaped similar to a galaxy, but from where we are I don’t think we see anything but a visual “sphere”. So I suppose it would have to be much larger than we think it is, in order for it to be revolving without our noticing it yet. But, actually, that’s pretty much the way the 19th Century astronomers thought of our own galaxy, non-rotating and made up of “fixed” stars and “nebula”.

Personally, I don’t know what’s going on with the overall universe. I don't even know if it's really "expanding". I’m just basing some of my comments on what I’ve read about the different theories over the years.

What Eddington did in his book in 1933 was just avoid the “center” problem by saying that the universe probably existed as a small sphere (many light-years across) for a long time and then started to expand. He just avoided discussing the very beginning.

I didn't mean matter moving. I was talking about the slow speed of light, the light we see, distorting the view of an explosion type expansion and making it distinguishable from an expansion of space. So far I didn't handle light cones and whatever to determine how exactly it would distort it. It only works so good on paper if light was infinitely fast.

The other problem is still that the probability of any mass gaining impulse i in the initial explosion has to be (C*i)^2 (C being some constant) to result in the distribution of matter that we see. And the initial acceleration has to be able to go past c, I suppose, unless we would be close to the center.

One time I tried to think of what the universe might look like if we could see it from the outside, and if it is an expanding sphere, but then I realized the limited light-speed problem that you are talking about. That’s a big problem when we are dealing with great distances and a big universe. We certainly do see a time-lag distortion.

Sam5 wrote:
The second kind of explosion only occurs when there’s a force, such as friction or gravity, which slows some of the central material. I don’t see how you could get that in space.
But if that were the case, we could approximate the LARGE spherical surface of the explosion with a tangent plane, and upon that plane all the galaxies would be moving away from the center of the sphere at roughly the same velocity, and have little or no recessional velocity with respect to each other. In other words, the observed redshifts of galaxies would depend strongly on their position within the sphere of the heavens. If the center of the explosion happened to be located in the direction of the line through the NS poles of the earth, then galaxies along the equator would show little redshift, with more northern or southern galaxies exhibiting a larger redshift as a function of distance. That’s not the case.

Hmm, I thought I glanced through another post which suggested this, but i didn't see it now. Anyway, I apologize if I've stolen someone else's argument.

You might be able to explain the current distribution of galaxies and redshifts if you postulate a pretty unusual explosion--one in which the amount of matter blasted out at a given speed is proportional to the speed squared. So if X amount was spit out at speed Y, 4X would be spit out at speed 2Y. That's a pretty bizarre distribution.

True, but 'very close' is a relative term. What kind of proximity are you talking about and how would that affect galactic evolution? Whether we're talking about an explosive event or spacetime expansion, we still have to account for the early universe being very hot and very dense - too hot and dense to allow gravity to form galaxies. Taken a step further, that also implies that the universe cooled unevenly, with the outermost regions cooling before the innermost regions.

If the Big Bang was an explosive event, how do you account for these facts? It would imply that the outermost galaxies formed well before before the innermost galaxies. No such disparity has been observed. It would also imply that the cosmic microwave background should be noticeably uneven, with the innermost regions of the universe having a higher temperature and, consequently, a higher-frequency background radiation than the older, cooler outer regions. Again, no such disparity has been observed - in fact the cosmic microwave background is one of the most consistently uniform features of the universe.

Arguing that an explosive Big Bang would produce a larger universe than the currently held belief in spacetime expansion doesn't work since the generally accepted theory proposes an infinitely large universe where as an explosive Big Bang implies a finite universe. That would seem to bring the question back to the age of the universe. Most cosmologists would agree that the age of the universe is known to within half a billion years to be about 12.6 billion years old. The chief argument against this is the age of certain globular clusters, but that's only known to an error of +/- 3.5 billion years (11 - 18 billion years old). That's a sevenfold increase in uncertainty making this number less reliable by far. It would seem that for an explosive Big Bang to produce a universe that was large enough to render these predictions unobservable would require the universe to be far *older* than the current theory allows.

How do you account for this? Is our understanding of the age of the universe flawed? If so, how do you propose we recalculate its age? Keep in mind that to do this you would need to predict the cosmic microwave background, the average temperature of the universe, the distribution of galaxies, the motion and speed - apparent or otherwise - with which galaxies are receeding from us, *and* the rate or rates at which the universe cooled allowing everything from atoms to galaxies to form. It would also need to do this within the restrictions of lookback time.

A couple of points here:

I disagree that we don't know the 'why.' An explosive event and spacetime expansion would explain why they're moving. They differ on *how* they're moving.

An explosive Big Bang requires a finite universe. Spacetime expansion allows for an infinite universe. Since there's no way that a finite universe could be bigger than an infinite universe, you can't argue that the current theory predicts a size for the universe that is too small to account for the observational evidence.

You can't speek of a metaphorical center to the universe and argue for the finite universe. An explosive Big Bang requires a finite, spherical universe which, for obvious reasons, *must* have a center. You only avoid the issue of the universe not having a center with an infinite universe.

Again, a poor argument. We think the universe is infinitely large. Literally.

Actually, as I understand this, the problem isn't detecting 'slight' tangential (sideways) motions. The problem is detecting *any* tangential motion. Remember that although the objects in question are moving at large speeds compared to, say, the orbital speed of Jupiter, the distances involved are so large that it would take millions of human lifetimes to observe any change in relative position. As far as I know, the only way we have to measure the motion of distant galaxies is by calculating their redshift. However, redshift is completely useless for measuring tangential motion. The only reason it works for figuring out the rotation of the Milky Way is that stars in different *parts* of the Milky Way have different redshifts relative to the Earth (i.e., stars nearer the center of the galaxy have a lower redshift than stars nearer the edge). Since galaxies essentially move as a whole relative to the Earth, this technique won't work.

Not necessarily. Planets and stars revolve, but they're essentially spherical. Globular clusters can revolve, but they're also, as their name implies, essentially spherical. Therefore, it seems reasonable that the universe could be revolving at a low enough speed to keep its mass distribution essentially spherically symmetric.

A spherical observable universe is an unavoidable consequence of lookback time. Light travels at a finite speed. Light has only been travelling through the universe for a finite length of time (since the universe cooled to become opaque). Therefore, we should not be able to see any object whose light would take longer to reach us than the age of the universe. Since this is true with both an infinite universe and a large enough finite universe, the issue is not the size of the universe, but its age.

All the evidence suggests that the universe is expanding. Everything not gravitationally bound to the Milky Way is moving away from it. Either the universe is a finite cloud of matter with a center and edge, as predicted by an explosive Big Bang, or spacetime itself is expanding causing the distance between galaxies to increase, as predicted by the generally accepted theory that the Big Bang was the beginning of this expansion. There is no evidence that the universe is contracting (no unbound galaxies moving towards the Milky Way), nor that the universe *will* contract (the expansion is accelerating).

I haven't read the book myself so I can't check this argument (Anyone have a citation?). However, if he said this he was wrong. If the universe was the same as it is now, only smaller, there is no reason why it would suddenly start to expand. There are only two possible scenarios with this model. If the universe was not rotating, it could not start expanding without violating the law of momentum conservation. Objects at rest *stay* at rest until acted upon by an outside force. This scenario does not propose any method of generating that force. On the other hand, if the universe was rotating stably (centripital force balanced gravitation), some torque would have been needed to speed up the rotation and make the centripital force greater than the binding gravity. This violates the law of angular momentum conservation. Spinning objects remain spinning in a constant speed and direction unless acted upon by an outside force. The only way around this would be for the universe to have never been stable as a sphere, which this model doesn't allow.

In addition, spheres have centers. Period.


(Edited once for grammar)

Yahbut, the center is nowhere on the sphere.

I agree, totally. My point is just that a geometrically flat, three-dimensional, spherical universe will have a center. That no center has been observed implies that either the universe doesn't have that geometry or that it's old enough that the universe will have evolved to the point where all geometric evidence for its structure is outside of what we can observe, which is, I suspect, older than the universe is currently believed to be.

Aren't the terms "geometrically flat" and "spherical universe" contradictory? And besides, what kind of "evidence" would support a particular point as being the "center." You'd have to know what to look for before you could find it.