7
   

Where is the center?

 
 
Reply Sat 5 Mar, 2016 10:52 pm
If you look far into space, you're seeing it as it was long ago. So why do we see into the past in every direction? If we are in an expanding universe and we look in the direction of our motion, shouldn't we see nothing? Since the universe hasn't expanded in that direction yet, there should be nothing to see... I realize we're not at the outer edge, but surely we're not in the very center... Somebody please help me to visualize what the universe actually looks like!
 
oralloy
 
  2  
Reply Sun 6 Mar, 2016 12:20 am

There is no center, and no edge.

We see into the past in every direction because it takes time for light/information to travel to us regardless of the direction.
fresco
 
  5  
Reply Sun 6 Mar, 2016 01:41 am
@TomTomBinks,
Normal (Cartesian) geometry with axes heading for 'infinity' is not applicable to complex space-time problems, as Einstein showed. There are several types of 'geometry' which might be applicable, one of which called 'Projective Geometry, has 'minus infinity' and 'plus infinity' coinciding at a single 'point'. Obviously, this is almost impossible to visualize, but whether that particular geometry is employed by cosmologists or not, it illustrates the philosophical issue of whether 'visualization' is essential to 'explanation'. That point is the substance of your question.
0 Replies
 
Setanta
 
  1  
Reply Sun 6 Mar, 2016 04:27 am
dalehileman
 
  1  
Reply Sun 6 Mar, 2016 01:57 pm
@TomTomBinks,
Of course Ora and Fres hav e responded most adequately. But I pass this one along for what it's worth (not much, apparently)

http://able2know.org/topic/313482-1
TomTomBinks
 
  1  
Reply Sun 6 Mar, 2016 01:59 pm
@Setanta,
Yes, I see now. Thanks!
Setanta
 
  1  
Reply Sun 6 Mar, 2016 02:07 pm
@TomTomBinks,
I was, of course, just entertaining myself. But, you're welcome. Oralloy's answer was correct.
0 Replies
 
TomTomBinks
 
  1  
Reply Sun 6 Mar, 2016 02:10 pm
@dalehileman,
I appreciate your efforts but you people are killing me.
TomTomBinks
 
  1  
Reply Sun 6 Mar, 2016 02:17 pm
@oralloy,
So the "expansion" of the universe isn't real? If not, what is it expanding from if not the center? and what is expanding towards but the edge? I get that space is defined by the intervening distance between two objects, that without matter there is no space, and that as the universe expands more space is "created", but how is the ancient universe all around us? Another user suggested alternate geometries, which I will look into. Thank You.
dalehileman
 
  1  
Reply Sun 6 Mar, 2016 02:52 pm
@TomTomBinks,
Quote:
but you people are killing me
Alas, Tom, but how
fresco
 
  1  
Reply Sun 6 Mar, 2016 04:29 pm
@TomTomBinks,
Googling indicates that there seem to be three hypothetically possible 'shapes' for 'the universe'...flat, positive curvature, and negative curvature. Each of these models has different implications for concepts like 'center' and 'edge'. I seem to remember that Einstein used Riemann geometry( Non Euclidean positive curvature) to account for space-time.
0 Replies
 
TomTomBinks
 
  1  
Reply Sun 6 Mar, 2016 05:16 pm
@dalehileman,
By forcing me to delve so deeply into what I thought was a much simpler subject
dalehileman
 
  1  
Reply Sun 6 Mar, 2016 05:19 pm
@TomTomBinks,
Quote:
I thought was a much simpler subject
Yea Tom it's pretty involved
TomTomBinks
 
  0  
Reply Sun 6 Mar, 2016 06:20 pm
@dalehileman,
I mean, I've known about the big bang since I was a kid. Pretty basic; universe explodes from a single point, expands from the force of the explosion, eventually gravity will slow down, stop and then re-collapse into a single point, and then, "Boom!", next universe. Since then there have been some complications: not enough matter to re-collapse. is the universe an open ended one time event leading to total entropy? Then they discover dark matter and dark energy: now there's enough matter to re-collapse but dark energy is making the expansion accelerate instead of decelerate (WHAT!?!?). And only recently have I wondered why the ancient universe is visible in all directions instead of only in the direction of the big bang. So if the universe is expanding from a point it should be shaped like a bubble, and we're somewhere in the thickness of the bubble. But maps of the universe don't show that. Now I'm exposed to the idea that since the universe is all there is, it's misleading to think of concepts like "center" and "edge". That would only apply to an expanding mass in "already created" space. This leads me to believe that if I spend the next few decades studying diligently I may only be able to grasp a tiny portion of these concepts. And my point is.... ?
cicerone imposter
 
  1  
Reply Sun 6 Mar, 2016 06:47 pm
@TomTomBinks,
Infinite expansion of space is difficult to picture. Where is it going, and how far? There's no limit.
rosborne979
 
  2  
Reply Sun 6 Mar, 2016 07:47 pm
@TomTomBinks,
Picture the Universe like a giant loaf of uncooked raisin bread which is expanding in the oven. Then imagine you are on any one of the raisins, then realize that from your perspective everything is moving away from you and you seem to be at the center. Then note that the observation would be the same from any raisin. Then imagine that the expanding loaf of raisin bread has already expended to fill the entire oven and it's forcing the oven to expand, but you don't know what's outside the oven for it to expand into, so that part remains a mystery.

That's about as close as you can get with a 3 dimensional analog.
dalehileman
 
  1  
Reply Mon 7 Mar, 2016 12:12 pm
@TomTomBinks,
Quote:
.....Pretty basic; universe explodes from a single point, .... eventually gravity will slow down, stop and then .... "Boom!", next universe.
Well put, Tom

Quote:
....complications: not enough matter .... is the universe an open ended one time event....?
I think not, too much contradiction and parxadox

Quote:
Then they discover dark matter....making the expansion accelerate instead of decelerate (WHAT!?!?).
Yes Tom, that's what I say

Quote:
And only recently have I wondered why the ancient universe is visible in all directions instead of only in the direction of the big bang.
I believe the other guys have covered this pretty god but as Your Average Clod I'm wondering why I haven't also wondered

Quote:
So if the universe is expanding from a point it should be shaped like a bubble,
Nah, Tom, think about it some more. It's not that there's nothing outside but there simply is no outside. Hence we simply don't have a shape

Quote:
.... it's misleading to think of concepts like "center" and "edge".
Ye, yea, Tom, exactly

Quote:
That would only apply to an expanding mass in "already created" space.
Yea, precisely the reason why so ,any of our buddies are confused. It's something one can't see in minds' eye

Quote:
.... my point is.... ?
Of course Tom you've answered your own q
dalehileman
 
  0  
Reply Mon 7 Mar, 2016 12:13 pm
@cicerone imposter,
Quote:
Infinite expansion of space is difficult to picture
Cis, exactly
0 Replies
 
dalehileman
 
  0  
Reply Mon 7 Mar, 2016 12:14 pm
@rosborne979,
Quote:
observation would be the same from any raisin
Well put Ros
0 Replies
 
TomTomBinks
 
  0  
Reply Tue 8 Mar, 2016 01:01 am
@dalehileman,
I appreciate your input and the effort to help me understand, but I don't. You and some others seem to, or you're not letting not understanding bother you. You call yourself the Average Clod, but I think you must be a professor of physics... Since I'm not familiar with the math, I need a visual. I can imagine if one WAS well versed in the high math required to study cosmology, then at least he could fall back on it. Like "...if the value of this variable is less than n , then the universe has no definite shape, and since we can observe this to be true, then I accept the fact that the universe has no definite shape." But the rest of us are just left completely in the dark. My imagination is not great enough to fathom the concept of "No Space", or "Nothing Outside" or "Infinite", and I don't know the math. Possibly there's no way to "get" it without the math...
 

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