centre of the universe?

[zenith]

why do they teach high school physics students that there is no centre of the universe?<br /><br />If the universe did origionate from one single "big bang", wouldnt that therefore mean that the outer edges of the universe are traveling at a uniform (though possibly increasing) speed in all (x,y,z) coordinates? so therefore wouldnt the point of big bang be the centre of the universe, logically?<br /><br />for there to be no centre of the universe, wouldnt that mean to have several big bangs spread throughout the void of the primordial universe?, and for that to be possible, instead of all galaxies to be moving away from each other, as suggested, wouldnt there be a point where the density of galaxies is far higher than anywhere else found?<br />

 

[nexium]

Hi zenith: The present mainstream opinion also seems improbable to me, but it is not practical to teach 100 alternative opinions each of which is believed by ten or fewer experts. Neil

 

[zenith]

yeah i spose your right.. well what do you think then? is there a centre? id like to get as many opinions as possible, as you see, these are the types of questions i ask, which stray from what we are supposed to be learning, and get me in trouble..

 

[qzzq]

Zenith,<br /><br />Remember that we are <i>inside</i> the Big Bang, not looking from the outside in. There's an easy analogy to explain how every point in the Universe could serve as its center. Take a balloon and put some dots on it with a marker. Now inflate the balloon with air. You'll notice that every dot expands away from the others at an equal rate and no dot could be called the center - all of them equally qualify. That's basically how it is with the Universe. <div class="Discussion_UserSignature"> <p> </p><p>***</p> </div>

 

[qzzq]

eburacum45,<br /><br />You posted: <i>...some theories suggest it started from a three dimensional volume, by the way...</i><br /><br />Very interesting. Have you by any chance got a link to an online version of the theories? So that would mean that the spatial dimensions were already unfolded at the time of the Big Bang...so only time was added? <div class="Discussion_UserSignature"> <p> </p><p>***</p> </div>

 

[zenith]

but wouldnt the centre of the balloon you said, when deflated (or inflated so it resembled a small ball, as the universe was never "flat" as such), but wouldnt the centre of that point, remain in the same (x,y,z) coordinates? and that center of the non-inflated balloon, say (0,0,0), would be in the same position (provided the entire balloon isnt moving through space), as for the inflated balloon, where it would also be at (0,0,0), would it not?

 

[zenith]

after reading that.. it didnt make too much sense.. let me try again, without this balloon idea..<br /><br />using the current model of the big bang, we can safely say that all energy (to later form matter) origionates from one point in space (being an (x,y,z) coordinate, not the black stuff thats out there).<br /><br />And therefore because all energy/time/matter origionates from the point of big bang, say (0,0,0), and because the "explosion" was uniform, the speroidal shape that is the universe would have expanded in all directions at once.<br /><br />So therefore we should be able to assume, that as the big bang is continuing, all of the edges of the universe should still be expanding at the same speed, though the speed may have dropped, it is the same, in all directions.<br /><br />And hence we should be able to say, that the universe has a point of origion, the point where the big bang, well, banged, at the point (0,0,0).<br /><br />also i realise that we cannot use cartesian mapping to determine points in the universe, but i use it to help explain how i see it in my head.

 

[rogers_buck]

Think of the universe as being printed on the surface of a wrinkly defated balloon as tiny as anything in the universe can be. All of a sudden the balloon gets blown up. On the surface of the inflated balloon where the universe is there is no physical center just like the map of the earth has longitude and lattitude assigned arbitrarilly. The center of the universe ballon is off the surface (space time) and lays inside along an axis that is a special kind of time.<br /><br />The universe might not be curved like the surface of the balloon, it might be saddle shaped or flat like a computer screen. But like in a bad video game, flying off the right edge brings your spaceship back on the screen from the left. Again, no center.<br />

 

[zenith]

so by saying that, are you suggesting that the universe is an elipsoid.. flat, long and wide? because i was under the impression that it was more spherical because of the big bang, like in any explosion one does on a mailbox or in the back yard, an explosion pushes in all possible directions.<br /><br />and for it to be an elipsoid, wouldnt that mean that the universe is filling into something that is pushing enough against the "top" that it can no longer gain in height?

 

[spacechump]

Trouble is that you're still thinking in three dimensions...for really that's all humans can think in. But mathematics is not restricted to this fact. I found a great response online and wish to post it:<br /><br />http://van.hep.uiuc.edu/van/qa/section/New_and_Exciting_Physics/Relativity/20031024071957.htm

 

[zenith]

"the universe would not be (spatially) like a 3-dimensional sphere, but perhaps like the 3-dimensional surface of a 4-dimensional sphere."<br /><br />..what is a 4-dimensional sphere?

 

[rogers_buck]

I was non-commital about the shape. Spherical, hyperbolic parabaloid (saddle), flat, any shape is likely. The universe is finite in extent, but it has no edges or boundaries.<br /><br />For some models dark matter can be explained by a saddle or other highly curved shape, but in others it might be explained by an adjacent universe (p-brane) that contains mass. In some models dark energy could be explained by a leak of gravitons to an adjacent p-brane.<br /><br />I'm not sure which is the current top contender (or even if there is one), but for contemplation I would pick the sphere because nature likes spheres and it meets the requirement for finite in extent, but with no edges or boundaries. The true shape will be tough to sort out since that vantage point in our balloon visualization is meaningless. <br /><br />The geometries are a little strange to think about because what we are saying is that the three dimensions of space plus time exist on the surface of the sphere. For string theories there are additional dimensions that ride along with the four that we perceive. For M-Therory the total is 10 plus time. The reason we do not perceive these additional dimension is that they are Plank sized, that is to say the smallest dimension that can exist in this universe due to quantum effects.<br /><br />So in considering a spherical geometry for the universe you have to imagine that the sphere is not really expanded into anythng, it is just the curved shape of space-time (p-brane). We are visualizing it as a sphere from a vantage point that does not exist. Three really big dimensions and time replace out 2-dimensional curved surface of the balloon. This might be easier to visualize if you imagine another really big p-brane nested in a few of those higher dimensions hidden from us by the plank sized pin hole (dimension 5).<br />

 

[zenith]

well im afraid this thread has opened up more questions than it answers.. but i suppose that was to be expected wasnt it.. but i suppose i understand better why there is no centre.

 

[alkalin]

You cannot find the center of something if you do not know where the edges are---which we do not. Sort of like if you were on a ship lost in some very large ocean and not knowing the distance to any shore. You therefor could not determine if you were near the oceans center.

 

[meteo]

This is how I imagine the universe (really a mulitverse)<br /><br />*A table filled billiard balls which represents a THREE (for illustrative purposes) dimensional VISIBLE universe.<br /><br />*Now...at the center of each billiard ball is a reference point (an alien world, or earth).<br /><br />*That reference point in each billiard ball is the center of that reference point's own visible universe. We are in the center of our visible universe. The surface of each billiard ball is the "apperant beginning" of time when viewed from the center of each billiard ball, and the edge of the universe for all practicle purposes.<br /><br />*These billiard balls began as very small spheres (big bang) and are expanding over time.<br /><br />*Now there are two ways of thinking of the "center" of the universe.<br /><br />*If we are asking about the center of the visible universe (our billiard ball) then we are the center of our VISIBLE universe; that universe which is defined by what information has had time to reach us since the beggining.<br /><br />*Or maybe you were asking where is the center of the table! Now things get interesting, since we have never seen outside our billiard ball (it isn't possible to, speed of light!) how can we say how big the table is? It could be 3 billiard balls across, or one, or an infintite number of billiard balls. (With an INFINITE number of billiard balls probability states that some will be identical!) I thing ever 10^110'th on average.<br /><br />*Now we think that we are one of many billiard balls because ours is uniform. So this "suggests" the table is large relative to the billiard ball.<br /><br />Edit:<br />*The billiard balls are really 3-dimensional surfaces on a 4-dimensional sphere.<br />*The billiard balls are expanding do to the light having more time to travel.<br />*The billiard balls are "part of or connected" to the table which is expanding at an accelerating rate. Reason...still to be determined.<br />*This system is of some higher number of

 

[zenith]

very interesting way to look at it.. i must say though, i know we will never be able to locate the centre of the universe (speed of light and ever expanding universe and all), but using your analogy, my question would be not where is the centre of the table, but does the table have a centre? or do all the tables have a centre each, and then is there a centre of all the tables?<br /><br />also using your visualisation, does seem rather presumptuous that we call it a "uni"verse, when as you say, we cant see outside our billiard ball, let alone to the edge of our table...

 

[alkalin]

Per Meteo (and well done too) but in two dimensions, you would see the sea around you (the ocean example) in some ‘flat lander way’ in a circular form due to the horizon---a plane in a billiard ball. Someone on some other ship could do the same and your two circles could overlap. Sooo maybe if we somehow could communicate with said neighbor, we might learn more about some neighboring territory, an extension of what we know. And this neighbor might know of many other neighbors, and so on. So is communication the Key? <br /><br />

 

[meteo]

Yes that is true, the each table of course could be of infinite size, so there would of course be no center. The table could also be of any object, although I believe it is a saddle.<br /><br />Is there a center of all the tables. It is pure speculation that there are other tables. Other tables would represent other "branes." This is a fringe theory largely because it is PURE speculaton, and to my knowledge not directly testable. However, the idea goes (The Cyclic or Ekpyrotic or Brane Universe model) that when two branes (table) colide the resultant energy of the virtual particles (particles that come in and out of existance)coliding, would create the matter in both branes (the big bang). This theory is as I said so speculative, so despite the fact that I like it I cannot wholly endorse it.<br /><br />Yes, I agree we are just inferring when we talk about outside our visible universe. Which is why I make sure to call the make sure I clarify that what we see is that part of the table which is visible to us.

 

[meteo]

Remember the speed of light. In the end we cannot see outside our visible universe no matter what, there are no loopwholes. We can only see further by letting time pass. <br /><br />If we made contact with someone 1 billion light years away. They would be able to see 1 billion light years farther in a certain direction then us. However, their message would take 1 billion years to get to us. By then OUR visible universe would have expanded by 1 billion light years. So the information that comes from the alien and that information coming from our telescopes cannot see farther than the other.

 

[alkalin]

Aah, speed of light, you are right. But suppose we can establish contact and communicate instantaneously as some quantum physics results so far indicate might also be true, then what? (Granted, this is some future scenario)

 

[Maddad]

zenith<br />"<font color="yellow">..what is a 4-dimensional sphere?</font><br /><br />A 3D sphere is a ball that has equal dimensions in length, width, and height. A 4D sphere should have it's 4th dimension, time, equal to the radius of the ball. We normally do not consider how long the ball exists, but it was manufactured at some point, when its time starts. Later on a kid kicks it flat, so it's time ends. If your ball is 15 centimeters in radius, about a foot in diameter, then it must exist for the time it takes light to travel 15 centimeters. This is about half a pico second (0.000 000 0005 seconds or 500 femto seconds).<br /><br />The whole issue about whether the universe has a center misses some important points. If it does, or does not have a center, then it should maintain this property whether you look at it from the inside or the outside (whatever looking at the universe from the outside means!). If the universe has a center when you look at it from the outside, then it must have a center if you are looking from the inside. If it does not have a center when you are inside it, then it cannot have a center when you look at it from the outside. Since we are willing to say that the universe has a center if you look at it from the outside, I have a problem with saying that it has no center simply because we are inside it.<br /><br />The next point the discussion misses is that even though every point in the universe was at one time at the center, the singularity, that does not equate with all points remaining at the center now. While I am perfectly happy granting the first half of the statement, I take exception to the second.<br /><br />The third problem with the universe having no center is that I don't like it.

 

[meteo]

Now I am not entirely clear on this photon "teleportation" even though that isn't really what it is. It's states via entaglement not acual photons.<br /><br />When an entangled photon pair is generated, the state / spin of the photons are purely random. Only when the original state information from the sending side A of the experiment is matched against the altered state on the receiving side B, the transmitted information can be pieced together. This requires a normal, sub-lightspeed, means of communication (back where you started).<br /><br />If I'm mistaken (good chance) someone please correct me.

 

[zenith]

Maddad- your theories on the centre of the universe are intruiging. Especially the third, though it may not have any scientific proof, nor does any other argument that has been posted, i mean, this isnt proven work, and for as far as i can see, will never be proven.<br /><br />After all these posts, i still beleive that the universe must have a centre. any 1st, 2nd, 3rd dimension objects must have a centre, and so must therefore any 4th, 5th and so on..<br /><br />of course this centre will never be found if the universe increases in size as it will become impossible to map, no, it will become even MORE impossible, as it is quite impossible today.

 

[anoolios]

To address the original poster: Current astronomical observations support the theory that the <i>observable</i> universe is a sphere approximately 15 billion light years in radius. String <i>hypothesis</i> aside, this means that there is, according to theory supported by obeservations, a center point.

 

[kmarinas86]

The center of an enclosed space exists (defined).<br />The center of an unenclosed space does not exist (undefined).<br /><br />If the universe is an enclosed space, then the center of the everything is defined. If the universe is an unenclosed space then the center of everything is undefined.