If the universe originated from (the) Big Bang, which direction is it as viewed from earth. Where in the sky can we point and say that is where Big Bang happened? Is it possible at all?

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A slight inclination of the cranium is as adequate as a spasmodic movement of one optic towards an equinine quadruped utterly devoid of any visionary capacity.

Point anywhere, everywhere. That is where it happened.

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0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 ...

I mean, for example, with the balloon experiment the center would be the center point of the balloon.

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A slight inclination of the cranium is as adequate as a spasmodic movement of one optic towards an equinine quadruped utterly devoid of any visionary capacity.

Hum,
yeah,
Draw a rightangle to all the three directions.

The balloon is 4D

In the balloon analogy, the centre of the balloon isn't part of the Universe: only the surface. If the centre of the balloon has a direction from the surface, then it's backwards in time, as far as the 2D balloon-inhabitants are concerned. The whole surface of the balloon was involved in their "Big Bang" (when the balloon started to inflate) so there's no spacial direction they can point in that's better than any other.
Likewise, for the real Universe. The Big Bang happened everywhere, occupying all the space we can see; so there's no specific direction you can point in that's better than any other.

Grant Hutchison

galaxies are moving away from each other as the universe is expanding. Some galaxies are moving towards us. Where would be the point in the universe where every galaxy is moving away from you in all directions.

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A slight inclination of the cranium is as adequate as a spasmodic movement of one optic towards an equinine quadruped utterly devoid of any visionary capacity.

There's no such point. Wherever you stand in the Universe, you'll see almost every galaxy moving away from you, with the exception of a few nearby galaxies, the motion of which is more influenced by gravity in your local cluster than by the overall expansion of space.
That's the point of the balloon analogy: wherever you stand on the surface of an inflating balloon, you'll see the rest of the balloon's surface expanding away from you.

Grant Hutchison

The only galaxies moving toward us are those very close, in the local group. All others are receding from us. The view would be the same anywhere else in the universe. One would see a few nearby galaxies closing (blue shift) while all others are receding with a speed proportional to their distance from one(the Hubble constant). As others have pointed out, the answer to the question of "where" the BB occurred is "everywhere". At the time of the BB all of the universe was a singularity, and all space has expanded since then.

The principle that there is no center to the universe and that no point is "privileged" another (as a center would be) is referred to as the cosmological principle. Basically, it says that the universe looks the same regardless of where you are. I'd suggest getting a good text on introductory cosmology. One I'm working through now is entitled (appropriately enough) An Introduction to Modern Cosmology by Andrew Liddle. It goes into more depth than a "popular" book might, but not so much that someone with some college science couldn't understand it.

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"I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind." - William Thompson, 1st Baron Lord Kelvin

"If it was so, it might be, and if it were so, it would be, but as it isn't, it ain't. That's logic!" - Tweedledee

This isn't right. This isn't even wrong. - Wolfgang Pauli

I always thought the BB is like fireworks. And all galaxies are moving away form a center. Now that I think about it I think I get where I went wrong. Thanx for explaning to me

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A slight inclination of the cranium is as adequate as a spasmodic movement of one optic towards an equinine quadruped utterly devoid of any visionary capacity.

A brief history of the 20th Century Big Bang theory:

There is an interesting history about this topic that not too many people are familiar with. The original Lemaitre big-bang theory of 1927 was a “fireworks” theory: The universe began at a point and expanded outward in all directions, as in this illustration:

http://tinypic.com/jj1iso.jpg

Our position, of course, would be somewhere inside it.

However, this was not considered the “proper” way to look at the situation in mainstream astronomy, since that tended to place our viewing position in the “center” of the visible universe, with the origin of the big bang appearing to be right here in the vicinity of our own galaxy. That’s because during all the years we have looked outward in all directions, with bigger and bigger telescopes, we see an equal number of galaxies in all directions.

During the first several decades after Lemaitre’s theory, there was a concern among many astronomers that our viewing position seemed to be in the “middle” of the universe, since we couldn’t see any outer “edge” or limit to the most distant galaxies. If there was an outer edge not too many billion light-years away, and if we are not in the center of the universe, we should see fewer galaxies in one direction of the sky (in the direction nearest we are to the outer spherical edge), and many more galaxies in the opposite direction. But that’s not what we see. We see an equal amount of galaxies in all directions.

So, to avoid this problem of our appearing to be visually in the “center” of the universe, and at the initial “origin point” of the big bang, the famous astronomer Arthur Eddington promoted the “expanding balloon” model in his important 1933 book, titled “The Expanding Universe.” It is not a proper 3-D physical model of the expanding universe, but it caught on and it is the “mainstream” model today. Everyone is just supposed to go along with it.

Here’s what Eddington said about it:

“For a model of the universe let us represent spherical space by a rubber balloon. Our three dimensions of length, breadth and thickness ought all to lie in the skin of the balloon; but there is only room for two, so the model will have to sacrifice one of them. That does not matter very seriously. Imagine the galaxies to be embedded in the rubber. Now let the balloon be steadily inflated. That’s the expanding universe.”

That’s pretty silly. We are NOT “embedded in the rubber” of the balloon, nor are we on the “surface” of our expanding universe. But that’s the standard answer you will get whenever you ask these two questions: “Where did the big bang begin?” and, “Where are we in the universe?”

My personal opinion is that we are way off center and the universe is much bigger than most people think it is, but since our viewing distance is limited, we see an equal number of galaxies in all directions. But this is not the “mainstream” theory or model. However, it does give you some background information about the history of this topic. The so-called “principle” that is called the “cosmological principle” is merely a postulate. It is not a known fact. It is merely a claim and an assumption. Since we are stuck in our position inside a really BIG universe, and with very SMALL telescopes, we just don’t know how large the universe is, we don’t know if it is finite or infinite, and a lot of people aren’t even sure it is “expanding” at all.

Don't feel bad -- that's a common misconception.

SciAm ran a nice article last spring addressing BB misconceptions, perhaps you'd find it helpful. The original story on the web contained graphical illustrations which have unfortunately since been removed, however their analogies are pretty handy and straightforward.

To me, the most misleading aspect of the balloon model is that the balloon is pictured as sitting within a larger, three-dimensional embedding space. One of the triumphs of Riemannian geometry was to free the mathematical treatment of metrized manifolds from the necessity of picturing an embedding space. Some two-dimensional manifolds, for instance, the Klein bottle, cannot be embedded in a larger three-dimensional Euclidean space*. Yet we could imagine a Klein bottle whose dimensions were increasing over the course of time. The Klein bottle would be expanding, not relative to a larger embedding space but in the sense that each pair of points on the Klein bottle would be getting further and further apart. There would be no temptation to point to a spot in the embedding space as the center of the expansion since there can be no(three-dimensional Euclidean) embedding space for the Klein bottle..

GR desribes the universe in terms of a four-dimensional spacetime, but this spacetime is not pictured as lying inside an embedding space - it is considered intinsically. Any embedding space that we picture is unnecessary and potentially confusing. One way to avoid confusion is to picture spacetime locally, instead of globally. This is really what mathemeticians did when they created the concept of a manifold. A manifold is a topological space which locally looks sort of like Euclidean space (except, possibly, for the metric). When we try to think globally, we encounter the difficulty that not all points lie within the same reference frame, and the situation becomes more difficult to picture.

*The pictorial representations of the Klein bottle are what are called immersions (rather than embeddings) because there is no way to draw them so that they don't intersect themselves. These drawings are just meant to be suggestive - don't take them too literally..

That was before the BB was discovered. That was back when Einstein tried to explain a non-expanding universe that had no center. That idea went out with his 1932 paper conceding the expansion. That old idea didn't apply to the universe anyway. It came from Beltrami's "Teoria Fondamentale Degli Spazii di Curvatura Costante" of 1869.

See pages 406-429:

http://visualiseur.bnf.fr/Visualiseu...a&O=NUMM-99432

Here are some knitted Klein bottles:

http://www.cs.xu.edu/~smbelcas/mkkb.html

The only point of using the example of the Klein bottle was to illustrate the fact that it is unnecessary and misleading to think that there has to be an embedding space.

Analogies can become misleading in some ways. The possibilty of an expansion that is not centered at any point on a manifold can be illustrated by the example of an expanding balloon. The objection that the expansion of the balloon has a center within the embedding space is irrelevant to GR because GR does not involve an embedding space. Let us not go off into a discussion of Klein bottles. My post was not about Klein bottles. If you think that an expanding manifold requires an embedding space to expand within, I am happy to discuss that matter; if you feel that an embedding space is not required, then I agree with you.

I did not pursue the link in your post #13 because I do not read French. The link above refers to Klein bottles "with boundary". These are not actual Klein bottles because part of the KB had to be removed to make what is left (the KB with boundary) fit into three-dimensions. The "boundary" is the edge of the hole that is left after the removed piece got cut out.

Here is a link describing some glass "klein bottles." It begins by discussing how actual Klein botlles cannot be embedded in three-dimensions but can be immersed - necessitating self-intersections - in three dimensions. The only way to avoid self-intersections is to cut out a piece where the intersection would have occurred. Again, let us not make this example into a distraction. If anyone wants to pursue the discussion of Klein bottles (which I doubt), send me a PM, and I will respond via PM.

I disagree. Far from being "silly", I think it is quite a reasonable idea, and shows a willingness to go beyond the level of ordinary thinking, in an attempt to understand the universe.

You cannot justify either of these, as statements of fact, as you have presented them. Just as you say of the mainstream view, "It is merely a claim and an assumption", so are your own statements no more than claims & assumptions.

There is no doubt that some aspects of modern cosmology are dominated by fundamental, metaphysical assumptions. The absence of a center to the Bang, or more appropriately, the assumption that we do not inhabit a favored spot (i.e., the center of the universe), is one of them. But there is nothing silly about it. For one thing, Eddington's model is logically both self consistent, and consistent with all observations, and that makes it a valid theory, quite regardless of whether or not one wishes to accept it as true ("true" and "valid" are not synonymous in this context).

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

To be clear, the cosmological principle, that we are not at a special place, is not simply an arbitrary assumption or philosophical axiom. It has substantial observational support. And I don't just mean galaxies, though Hubble can see them to a huge distance in all directions. I mean the cosmic background radiation, which is amazingly isotropic. While it is still possible that we are at a special place, no observation to date has indicated even a hint of this on the largest scales we observe. Thus the cosmological principle continues to be the simplest principle that is consistent with the observations, and as such, is a required assumption of good science, not an arbitrary one.

This is starting to be interesting. There is yet to be a sufficient answer for Radiations question. I have wondered it myself but put if off as something that someone has an answer for and I'm too lazy to go find out.

So for what it appears is that this board has effectivly removed a concept of an expanding universe. First off.

If the big bang happend everywere at once then why are we expanding. Forget the force thats causing the acceleration for one second.... so no darkmatter stuff please. lets say we quantatize the universe for one second creat a cube. Crap load of light years/craploads of light years in dimension. So what you are saying is big bang happend everywere at and within this finite universe and now there is matter eveywere H, He. Then that means that we cannot say that essintially that all the galaxies was in the same place 14 billion years ago.
This seems to sound more like the Big Scatter than the big Bang???

Someone please nail the head in this coffin cause im starting to really wonder bout this physics, and science thing. I think religion is staring to sound good. Don't let it get to that im counting on you

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Since there are so many galaxies in the universe does any one mind if I claim one? I need a place to put my stuff.

First, this is the Q&A section of BAUT, not the ATM one (so if folk would like to propose their own, ATM, ideas, please do so by starting a thread in that section).

Next, a 'scope statement': 'the Big Bang theory' (it's actually a whole class of theories, but we can ignore that for now) is a scientific theory, in a branch of science called cosmology. If we are to answer the OP in terms of this scientific theory (and that's what this Q&A section's scope is), then we need to look at at least some contents of that theory. While Sam5's posts may (or may not) be interesting from the perspective of an aspect of the history of the theory, they aren't directly relevant.

So, as the BBT is based on GR, what are the key features of GR that answer the OP (and also bigbluestar's post about why we're expanding)?

It sounds to me like bigbluestar's conundrum is related to what is known as the Horizon Problem, which says that we can observe points in the universe that were not causally connected when the universe thermalized to one temperature (the Bang), yet they are at the same temperature nevertheless. This was viewed as such a large conundrum indeed that the theory of inflation was invented to explain it. Inflation gets you around the need to have the Big Bang happen at causally unconnected places at the same time, since everything we see comes from a region that was initially in causal contact. So you get both the Big Bang happening everywhere, and you get it to be basically all the same place, due to inflation. The variations we do see can then actually be attritubed to quantum uncertainties, in the ultimate irony. But that's inflation, which is kind of an add-on to the Big Bang theory. Whether or not it's right will require that we learn more about the fundamental particles and forces.

Tim,

Back in 1956 I had the good fortune to study astronomy in Junior High school at a time when the BB theory was being played down and not being discussed in popular astronomy books and not being covered much even in university textbooks. I learned that we are somewhere well inside a very large universe and that the universe is 3-D, plus it changes with time. Astronomical objects move around in time and within the 3 dimensions of space. I learned that the universe is “expanding”, but there was very little mention of high speed motion of the galaxies, so I assumed it was expanding rather slowly. So, I knew that we lived in a 3-D universe that was expanding with time. I also learned that time is NOT a spatial dimension. The progress of the so-called “dimension” of time merely moves things within the 3 spatial dimensions.

I also learned that we are not on the “surface” of our universe and that our universe was not a 2-dimensional expanding sphere with all the galaxies lined up around the “surface” as if they were people standing on the 2-D surface of a spherical planet. I also learned that we are not in the “skin” of a thin-walled spherical universe and we are not in any way like being on the “surface” of an “expanding balloon.” I could tell that simply by going out and looking at the sky through my 6-inch telescope.

So when the “balloon” analogy began to be revived in the 1960s and ‘70s, I thought it was stilly then, and I still think it is silly, because it IS silly. It doesn’t match observation at all. It is just as silly as the ancient belief in a “flat earth.”

When I renewed my interest in astronomy and cosmology, about 15 years ago, I found the new books filled with Big Bang stuff and the absurd “expanding balloon surface” model. I wondered why. I wondered how this incredibly wrong idea could be taught by so many people as if it were a true model of the universe. Well, I read enough books so that I finally found out why it is taught, even though it is wrong. I read this in Hawking’s “A Brief History of Time”:

“Now at first sight, all this evidence that the universe looks the
same whichever direction we look in might seem to suggest there is
something special about our place in the universe. In particular, it
might seem that if we observe all other galaxies to be moving away
from us, then we must be at the center of the universe. There is,
however, an alternate explanation: the universe might look the
same in every direction as seen from any other galaxy, too. This, as
we have seen, was Friedmann's second assumption. We have no
scientific evidence for, or against, this assumption.”

Note that Hawking says, “We have NO scientific evidence for, or against, this assumption.

He continues:

“We believe it only on grounds of modesty:”

Note that he says, “We BELIEVE it..” He says there is no scientific evidence for it, but he and other scientists “believe it” because that is part of their metaphysical “belief” system, and it is not based on any scientific or observational facts.

Hawking continues:

“It would be most remarkable if the universe looked
the same in every direction around us, but not
around other points in the universe!”

So what? There are a lot of “remarkable” things in nature. Why rule out one more “remarkable” thing based only one one’s “belief system” and personal prejudices?

Hawking continues:

“In Friedmann's model, all the galaxies are moving
directly away from each other. The situation is rather
like a balloon with a number of spots painted on it being
steadily blown up. As the balloon expands, the distance between
any two spots increases, but there is no spot that can be said to be
the center of the expansion. Moreover, the farther apart the spots
are, the faster they will be moving apart.”

So, here is a modern explanation of the metaphysical “belief system” that leads to the false “expanding balloon” model. And I’m not going to blindly believe in Hawking or Friedmann’s “belief system” just because Hawking tells me too. If he wants to preach, he should start a church or become a metaphysical guru, and he should keep his personal metaphysical “beliefs” out of his science books and out of the classroom.

Anyway, he and Friedmann are wrong about the statement: “the universe might look the
same in every direction as seen from any other galaxy, too.”

This is impossible. What he should stay is that as far as we can tell now, the universe looks “similar” in every direction as seen from other galaxies that we can see.

And since we do not know if the universe is infinite or finite, then we don’t know if it is spherical or not, and since we can’t see any end to distant galaxies the further we look out with the bigger telescopes, we have no way of determining, yet, if the universe is spherical or not or finite or infinite. Any attempt to answer these questions are merely guesses, just like mankind has been guessing about this same question for the past 50,000 years.

What we can see from our viewing position is that the universe seems to be expanding and that the more distant galaxies and the galaxies that are far apart seem to be moving away from each other at faster rates than the galaxies that are closer to each other. If that is correct, then what that strongly suggests is an expanding Euclidean sphere of an expanding universe, with us SOMEWHERE inside it, but we don't have any clue as to where we are inside it.

We don’t have to be in the “center” in order to observe this phenomenon, nor do we have to proclaim that every galaxy “sees exactly the same thing”.

We could be anywhere inside the universe and not be able to tell our location as long as we can’t see any end to the distant galaxies in any direction in which we look.

It’s like being in a long line waiting to get into a movie. We are somewhere in the line, but the line stretches around the corner in front of us and behind us, so we don’t know where we are located in the line.

We could be near the front of it, or we could be near the end of it, but since we can’t see the front of it or the end of it, we can not tell where we are within the line.

Nor can we tell where we are within the universe, since we can see no end of it in any direction in which we look. For anyone to falsely assume that we are “in the center”, is merely a delusion. For anyone to falsely assume that we can’t possibly be near the center is also a delusion. And we should not proclaim where we are NOT, any more than we should proclaim where we are, just based on our personal ideological or religious or anti-religious or metaphysical belief system. That “belief system” stuff should be kept out of hard science, and out of the classroom. And we are certainly not on the 2-D “surface” or our universe and we’re not embedded in the thin “skin” of our universe.

As far as being in a “favored position” is concerned, I think as humans our “favored position” is right here on earth, and that of course is a scientific fact that we don’t need to debate. Where we are, or are not, in the universe, is yet to be determined, and I refuse to live in fear that we either might be somewhere near the center or well out of it. It doesn’t matter to me, and it shouldn’t matter to anyone else. We aren’t in the center of our own galaxy and that is fine with me. We aren’t in the center of our solar system, and that’s fine too. We aren’t in the center of the earth, and that’s very good. But the truth about our position in the whole universe is that we just don’t yet know where we are within it. Maybe we’ll never know, but in the meantime I’m not going to fall for Hawking’s or Friedmann's personal ideological and metaphysical beliefs about it.

Nereid,

I think it would help a lot of astronomy students to study the history of the Big Bang concept, going all the way back to Newton’s ideas about it. He often wondered about why the universe didn’t seem to be collapsing, even with all the gravity trying to “pull” all the stars together. He proposed several ideas about it: 1) maybe it was collapsing but we couldn’t tell it because of the great distances of the stars, 2) maybe it was expanding but we couldn’t determine that, 3) maybe it was rotating with the centrifugal force just counterbalancing the centripetal force, 4) maybe it was infinite, so that there would be an equal “pull” on all the stars from all directions.

Newton wrote most of his speculative ideas in various letters and not in his main books, but years later some of the letters were published and read by various scientists in the 19th Century. Based on Newton’s ideas about this, here is something written about the Big Bang idea in an 1803 astronomy book that I have, and this is based on Newton’s ideas:

“But many of the heavenly bodies, as the sun and fixed stars are stationary. Their rest must be the effect of an absence or of an equilibrium of attractions. It proves also that a projectile impulse was originally given to some of the heavenly bodies, and not to others. But further; if attraction act at all distances, there can be only one quiescent center of gravity in the universe: and all bodies whatever must be approaching this center, or revolving around it. According to the first of these suppositions, if the duration of the world had been long enough to allow it, all its parts, all the great bodies of which it is composed, must have been gathered together in a heap round this point.”

Note the term “projectile impulse”. That is an 1803 version of the Big Bang theory.

This topic was discussed in various science and philosophy books in the early 19th Century, since books of Newton’s letters were in publication at that time, and amazingly Edgar Allen Poe even wrote an essay about it in 1848, titled titled “Eureka,” available here: http://xroads.virginia.edu/~HYPER/poe/eureka.html

Among other things, Poe said this:

“The assumption of absolute Unity in the primordial Particle includes that of infinite divisibility. Let us conceive the Particle, then, to be only not totally exhausted by diffusion into Space. From the one Particle, as a centre, let us suppose to be irradiated spherically -- in all directions -- to immeasurable but still to definite distances in the previously vacant space -- a certain inexpressibly great yet limited number of unimaginably yet not infinitely minute atoms.”

Note that Poe says “From the one Particle, as a centre, let us suppose to be irradiated spherically – in all directions”. That is the BIG BANG as hypothesized by Edgar Allen Poe in 1848.

GR was NOT the origin of the Big Bang theory. In fact Einstein tried to use GR to prove that the universe was NOT expanding or contracting. In that regard, if the universe is indeed expanding, GR turned out to be wrong, because in 1905-1917 Einstein thought all the stars were “fixed” in space, except for some small random motions at slow speed.

I am a researcher. I’ve spent a lot of time researching this topic. I think it is important that students understand the true facts of science and part of that education is understanding the history of various science theories. The history of the BB theory is that it goes back to Newton in the 17th Century, it was discussed in books in the early 19th Century, it was denied by Einstein in 1917, and he had to back down from his position in a paper he wrote in 1932. That paper is here:

http://tinypic.com/hvny95.jpg

The idea about 4-Ds of space did not originate with Einstein or the GR theory. He got the idea from geometers of the 19th century, such as Riemann, Beltrami, Helmholtz, Poincairé, Cayley and others, who were speculating about “what if”.... what if there were 4 dimensions of space, then how would they describe it in geometrical terms. Einstein tried to artificially patch their ideas into his new GR theory in an attempt to promote his belief that the universe was neither expanding nor contracting, and of course he had to back down when Hubble announced his discovery about the redshifts of the galaxies in 1929, and after Lemaitre’s 1927 Big Bang paper began to be widely published.

All of this history should be taught in astronomy and science books today, but it is not, because too many science writers are influence by their own ideological and metaphysical personal beliefs about it, and they want to promote those ideas and avoid discussing the 300 year history of the Big Bang concept, and I think that is a shame and is unscientific.

Sam

Sam, the balloon analogy is just that, an analogy. Of course we are not embedded in the rubber of a balloon. But the point of the balloon analogy is to explain how the universe can be expanding everywhere at once, rather than expanding away from a common centre, which can be counterintuitive.

P.S. Other analogies for the Big Bang.

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"A witty saying proves nothing" Voltaire.
"All your bias are belong to us" Ara Pacis.

this all matters if the universe did indeed start with a bang anyway.

Nobody wants you to believe that you live inside the 2 dimensional membrane of a baloon. That would indeed be most silly.

Sam, you have to realize that the baloon analogy is a 2 dimensional analogy to our 3 dimensional universe. The surface that is expanding is not 2D but 3D as you very correctly have observed. So the Universe is analogous to the 3D surface of a 4D hypersphere (4 dimensional baloon) - except we don't need the 4D sphere in order to have the 3D surface, as explained by:
To S. Hawking's comment on Friedmann's second assumption about the Universe looking the same from ANY point in the Universe

“We believe it only on grounds of modesty:”
“It would be most remarkable if the universe looked
the same in every direction around us, but not
around other points in the universe!”

you argue:
Okay - so you, Sam, argue that we astronomers base our theories on the most whimsical ideas.
I am afraid it isn't so.

First of all, if you get out of your house you'll see that your house is not particularely special - there are thousands of other houses in your town. Even your town is not all that special - there are thousands of other town in you country. Your Country is not that special either, or our planet, or our Solar system, or our galaxy, or our galaxy cluster.
It is indeed most logical to assume that we are not particularely special and we are NOT the centre of the Universe. Wouldn't you think that our Galaxy would have looked rather different from other galaxies if it had been the centre of the giant explosion that now make everything fly away from us?!?!?

Second: There would be no cosmic background radiation if BB was an exposion into space. The explosion would start somwhere in our galaxy and all light would leave us at the speed of light [duh] never to be seen by us again.

In reality, the cosmic background radiation is light from the BB coming to us from other parts of the Universe - since it looks the same in all directions that whole spherical shell must have been part of the BB. The spherical shell has a radius of
[speed of light] x [age of Universe] = 13.7 billion lightyears - that is the shell that sent out the light from the BB that we see today. Tomorrow that shell will be one light-day further away from us. It is of course not a material shell, but just the sphere described by the lighttravel-time from the BB to us in the present.

I think it would be extremely contrived to assume that the galaxy we just happen to sit in, as well as a spherical shell of 13.7 billion lightyears in radius that just so happens to be sitting at the edge of the observable Universe as observed by us, both were part of the same explosion - without the space in between or beyond, also being part of that "explosion".

Furthermore, we have equations derived from fundamental principles that describes expanding universes (where it is space itself that expands) beautifully.
Coming up with a (physical) model for an explosion into already existing space would actually be a lot harder.

Regner Trampedach

I do not understand why you carry on with such force, when you say in fact, nothing that we don't already know. What's the point? We all know it is a metaphysical principle, and I already said that more than once. Of course we might be at the center of the universe, and we might be in a favored spot, we simply assume that is not the case because it is unlikely on probabalistic grounds.

Your comments on the history of the expanding universe are interesting, and I wish you would tell us some of your sources. The oldest astronomy book I have, from 1820, talks only about planets. I should like very much to see one that goes beyond that scope.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

<showing my ignorance of the subject>

If the Big Bang started as a singularity, wouldn't all points be at the "center"?

Perhaps we really are at the center of the universe. And perhaps every other point is as well, from it's own perspective.

</showing my ignorance of the subject>

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Home of the Illumi-Llama:
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Hum,

<showing my knowledge of the subject>

yeah, all is one

</showing my knowledge of the subject>

Most likely, it did not. The singular beginning of the universe is only an artifact caused by an overly literal interpretation of general relativity, suitable for "public consumption", but not really correct. The singularity is an indication of a failure of the theory, not a true physical state.

Strange as it may seem, big bang cosmology is not a theory of the origin of the universe, and never was. It is a theory of the evolution of the universe, beginning from the time it is old enough to be described by the classical physics of general relativity. A new theory of spacetime, one that goes beyond general relativity, is required to extend big bang cosmology into the arena of including the origin, as well as the evolution of the universe. That is the motivation behind the search for a quantum theory of gravity.

__________________
The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell