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Center of the universe

by superdave
Tags: universe
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DaveC426913
#55
Mar25-10, 06:57 PM
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Quote Quote by xxChrisxx View Post
Fantastic response. Care to elaborate?
OK, technically it's incorrect, but in spirit it's correct.

There are some nearby galaxies that are blue-shifted due their to inherent relative velocities.

It's kind of like saying the steep hill you're driving down is not entirely downhill; the road itself is quite uneven so there are a few places right near the beginning where the unevenness results in a very localized uphill slope.

Is it accurate to say the hill is only mostly downhill?
RWHITE
#56
Jul15-10, 03:39 PM
P: 2
Very good stuff guys.
But it started from a singularity.Which is a single point .Hence a center.
Of course the singularity is nothing but the most Super Massive Black Hole there ever was.
George Jones
#57
Jul15-10, 03:58 PM
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Quote Quote by RWHITE View Post
Very good stuff guys.
But it started from a singularity.Which is a single point .Hence a center.
No, a singularity is not necessarily a single point. A singularity is usually more like an edge. In the case of standard cosmological models, this "edge" is located in all directions.
Quote Quote by RWHITE View Post
Of course the singularity is nothing but the most Super Massive Black Hole there ever was.
No, the cosmological singularity is not a supermassive black hole.
Ich
#58
Jul15-10, 04:07 PM
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P: 1,893
But it started from a singularity.Which is a single point .Hence a center.
Nope.
A singularity is not within the manifold. Hence not an event.
You say "point". A point has a location, and persists through time. It is one-dimensional (extended in time direction), like a line.
But if the singularity were removeable (like in Milne's Model), it would not be a point. It would be an event. Events are a point in space at a certain moment in time. After that moment, there may be an infinity of "points" that all contain this "big bang event". They all have been at the "center".
Cuetek
#59
Jul15-10, 05:20 PM
P: 47
Quote Quote by RWHITE View Post
Very good stuff guys.
But it started from a singularity.Which is a single point .Hence a center.
Of course the singularity is nothing but the most Super Massive Black Hole there ever was.
No one knows what a singularity is in the real world. We only have a mathematical model of a singularity in terms of two sets of very theoretical phenomenon. One is the black hole, and what actually abides at its "center" is unknown. The other is the Big Bang and what it might have constituted its origin is even less certain. We have mathematical models that presume all manner of outlandish properties in order to make them viable systems withing our mathematical capabilities. But no one can tell you with confidence what a singularity is in the real world.

But perhaps more importantly, you presumption that "it all" started with what was at the origin of the part of the expanding profile we can see is a presumption that is equally unfounded. Men like to think that everything they happen to be able to see is sufficient to describe the universe. Since it never has been the case, I can confidently say that it is unlikely to be so now. The Big Bang is a little pop among countless billions, just like every other physical phenomenon you can identify.

All material phenomenon are finite and multiply manifest. You can find the end of every phenomenon and another example of it somewhere else. We look at the largest phenomenon and idiotically say that's everything. We cling to our localized mythologies again and again, only to find more universe again and again. The stuff is all finite. The context is infinite. That's what the evidence shows most clearly.

-Cuetek (Cling away.)
xxChrisxx
#60
Jul15-10, 05:32 PM
P: 2,044
Quote Quote by Kronos5253 View Post
What is the Andromeda galaxy's shift color?
I can't believe I didn't read this earlier.

Oh come on, thats just being picky. You KNOW why Andromeda is blueshifting. Becuase the gravitational attraction with the Milky Way is pulling us together. It was obvious to all that I was referring to Cosmological Redshift. Andromeda certainly isn't moving towards us because that bit of spacetime is 'expanding in the wrong direction'. This was a thread about the centre of the universe and expansion.

Dave's analogy is good for this. You'd never say that due to a highly localised upwards gradient that it wasn't downhill.
seanm
#61
Feb15-12, 03:05 PM
P: 1


I have two arrows on this screenshot... One (on top) points to somewhere around where earth is... The second, points to a giant bright glowing center of our universe (at least, I think it is our universe - is there something bigger than our universe but smaller than "everything"?). What is the giant glowing thing... Of course, you could argue that SOMEONE created this 3d depiction of our universe, so maybe they are wrong... But I have seen this same concept in several different depictions, so there has to be some logic behind the giant glowing light... Can anyone answer?
Hoku
#62
Feb15-12, 05:27 PM
P: 166
Actually, by definition, the universe IS everything. I know there's a new popular movement about the "multi-verse", but that's ultimately semantics. The "universe" is intended to describe everything that is.

What you appear to have a picture of is not the universe, but a galaxy. There are a gajillion galaxies in the universe. I'm not sure that the giant glow in the center of galaxies has an official name, but I'm sure someone on here can answer for you if it does. The "glowing" is due to a greater clustering of stars and space dust, which both emit and reflect a great amount of light.

I hope that helps!
DaveC426913
#63
Feb15-12, 05:34 PM
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seanm, yes as Hoku points out, what you have there is not a picture of the universe, but a picture of a galaxy, specifically a spiral galaxy. Our galaxy is called the Milky Way, and it is but one of billions in the universe. There's another one nearby, called Andromeda, about 2 million light years away.

The central area in a spiral galaxy is called by many names - most often the core or the central bulge. It's a dense packing of millions and millions of stars.

http://en.wikipedia.org/wiki/Galaxy


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