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View Full Version : our "place" in the "universe"?



xfahctor
2008-Dec-21, 06:20 PM
I'm not sure how to ask this, so bear with me. Also, please try to avoid any physics, math, or such as I'm way below understanding that stuff and it makes my stupid-gland swell and hurt. So, on to my question. Where do we sit in the "universe"? As my simplistic way of thinking grasps things, everything we see in our sky, all the galaxies, which formed from the "big bang", would seem to me to have to be spherical in arrangement, the big bang expoding out from one central point. So, even though the space that the stuff in our universe occupies may be infinate, the objects in it should be sphericly arranged, yes? So based on this, where does the milky way galaxy sit in this sphere?

Second bonus question. If other "big bangs" had occured, forming other universes in this vast space, is finding those other universes a matter of waiting for the light to finaly reach us and knowing which direction to look? I mean if other big bangs had occured, could we be suprised by a find of this magnetude some day either through accidental discovery through hubble or other high end technology? Imagine how amazing it would be to witness the big bang of another universe forming, imagine the knowlage that could be gained.

hhEb09'1
2008-Dec-21, 06:30 PM
[/INDENT][/INDENT]I'm not sure how to ask this, so bear with me. Also, please try to avoid any physics, math, or such as I'm way below understanding that stuff and it makes my stupid-gland swell and hurt. So, on to my question. Where do we sit in the "universe"? As my simplistic way of thinking grasps things, everything we see in our sky, all the galaxies, which formed from the "big bang", would seem to me to have to be spherical in arrangement, the big bang expoding out from one central point. So, even though the space that the stuff in our universe occupies may be infinate, the objects in it should be sphericly arranged, yes? So based on this, where does the milky way galaxy sit in this sphere?
As near as we can tell, everything seems to be at the center

Here is a webpage (http://www.astro.ucla.edu/~wright/nocenter.html)that tries to get at that idea
Imagine how amazing it would be to witness the big bang of another universe forming, imagine the knowlage that could be gained.The early big bang looks to have been opaque for the interesting part :)

astromark
2008-Dec-21, 06:36 PM
our "place" in the "universe"?
So you want to know every thing about everything... welcome.
We can see some of the universe. From what is known by back ground radiation remnants of the Big Bang we have made some progress in understanding the shape of and our position in this universe. We are not in the middle. Everywhere is the middle, and its not a perfect ellipse. The space between matter is continuing to accelerate the expansion we have detected. I could not hope to explain all of everything here... A lifetimes work for some... Your understanding of the whole of the universe is a very complex task.

xfahctor
2008-Dec-21, 06:47 PM
To quote, "the more I learn, the more I am astounded by my own ignorance" Guess I was fundamentaly WAY far off in my assumptions. thanks for clarifying things for me.

Jeff Root
2008-Dec-21, 06:56 PM
There is no indication of any "edge" of the Universe, so we don't know
where or even if such an edge exists. It is theoretically possible, though
I think very unlikely, that the matter of the Universe is infinite in extent.
The conventional wisdom is that the Universe is finite but unbounded.
That is, even though it is finite in size, it has no edge of any kind. There
is nowhere you could go and no direction you could look that you would
see an absence of galaxies beyond.

In order for this to be, spacetime must be curved on the scale of the
entire Universe. Curved in a way similar to the curvature of the surface
of a sphere. You can move around forever on the 2-D surface of a 3-D
sphere without ever coming to an edge. Similarly, you could move
around forever through a 3-D finite but unbounded universe without
ever coming to an edge.

However, no such overall curvature of the Universe has been found.
That doesn't mean that the Universe isn't curved in that way. It just
means that IF it does curve in that way, the curvature is very gradual
and hence the Universe is very big-- even bigger than the part of it
that we can see.

In either an infinite universe or a finite but unbounded universe, there
is no edge, and no center.

I personally think that the Universe most likely is finite and bounded,
as you assumed, but in that case, too, it must be far larger than the
already absurdly enormous part of the Universe we can see, and there
are no observations to support my view over that of an unbounded
universe.

If "other universes" exist, and it is possible to tell that you are seeing
such a universe when you look at one (How could you tell?), then the
fact that none have shown up yet makes it appear unlikely that any will
show up in the near future-- say, the lifetime of the Sun. But maybe
there are other universes at the limits of Hubble's ability to see, and
maybe we will see them and recognize them for what they are. I would
be very surprised to see anything like that happen.

-- Jeff, in Minneapolis

antoniseb
2008-Dec-21, 07:03 PM
Adding to what Jeff has said so well, there is a concept of "The Visible Universe", which is not the whole universe, but that part of it thet we can collect information about. In the visible universe, we are very near the center, and moving in a specific direction relative to the CMBR.

Swift
2008-Dec-21, 07:08 PM
The conventional wisdom is that the Universe is finite but unbounded.
That is, even though it is finite in size, it has no edge of any kind. There
is nowhere you could go and no direction you could look that you would
see an absence of galaxies beyond.

In order for this to be, spacetime must be curved on the scale of the
entire Universe. Curved in a way similar to the curvature of the surface
of a sphere. You can move around forever on the 2-D surface of a 3-D
sphere without ever coming to an edge. Similarly, you could move
around forever through a 3-D finite but unbounded universe without
ever coming to an edge.

The way I like to imagine it is thinking of the Universe sort of like a giant balloon, and we're a very tiny ant crawling around on it. The Big Bang was the original creation of the balloon and it just keeps getting blown up bigger and bigger. The ant can crawl around the surface of the balloon and never find an edge.

antoniseb
2008-Dec-21, 07:27 PM
The way I like to imagine it is thinking of the Universe sort of like a giant balloon, and we're a very tiny ant crawling around on it.

While I like this analogy, let's be clear that unlike the ant, we have NO chance of finding a place where some big guy is blowing in to a dimension we can't see... and there is no giant clown getting ready to twist us into a poodle.

cosmocrazy
2008-Dec-21, 07:37 PM
QUOTE=xfahctor;1393242] As my simplistic way of thinking grasps things, everything we see in our sky, all the galaxies, which formed from the "big bang", would seem to me to have to be spherical in arrangement, the big bang exploding out from one central point.

Just to help you by clarifying a few things, the BB was not regarded to be an "explosion" per-say, but a very rapid expansion. Also the universe expanded everywhere at the same time so the universe is the central point, (but much larger than it was 13billion+ years ago)


Second bonus question. If other "big bangs" had occurred, forming other universes in this vast space, is finding those other universes a matter of waiting for the light to finally reach us and knowing which direction to look? I mean if other big bangs had occurred, could we be surprised by a find of this magnitude some day either through accidental discovery through Hubble or other high end technology? Imagine how amazing it would be to witness the big bang of another universe forming, imagine the knowledge that could be gained.

One other thing that is believed in the BB scenario, is that space-time expanded, rather than the matter/energy expanding into pre-existing (certainly as we know it)space.

Its mind numbing stuff and the more you learn the more amazed you will be.:)

xfahctor
2008-Dec-21, 07:54 PM
There is no indication of any "edge" of the Universe, so we don't know
where or even if such an edge exists. It is theoretically possible, though
I think very unlikely, that the matter of the Universe is infinite in extent.
The conventional wisdom is that the Universe is finite but unbounded.
That is, even though it is finite in size, it has no edge of any kind. There
is nowhere you could go and no direction you could look that you would
see an absence of galaxies beyond.

In order for this to be, spacetime must be curved on the scale of the
entire Universe. Curved in a way similar to the curvature of the surface
of a sphere. You can move around forever on the 2-D surface of a 3-D
sphere without ever coming to an edge. Similarly, you could move
around forever through a 3-D finite but unbounded universe without
ever coming to an edge.

However, no such overall curvature of the Universe has been found.
That doesn't mean that the Universe isn't curved in that way. It just
means that IF it does curve in that way, the curvature is very gradual
and hence the Universe is very big-- even bigger than the part of it
that we can see.

In either an infinite universe or a finite but unbounded universe, there
is no edge, and no center.

I personally think that the Universe most likely is finite and bounded,
as you assumed, but in that case, too, it must be far larger than the
already absurdly enormous part of the Universe we can see, and there
are no observations to support my view over that of an unbounded
universe.

If "other universes" exist, and it is possible to tell that you are seeing
such a universe when you look at one (How could you tell?), then the
fact that none have shown up yet makes it appear unlikely that any will
show up in the near future-- say, the lifetime of the Sun. But maybe
there are other universes at the limits of Hubble's ability to see, and
maybe we will see them and recognize them for what they are. I would
be very surprised to see anything like that happen.

-- Jeff, in Minneapolis
or perhaps the light from their forming just hasn't reached us yat

loglo
2008-Dec-22, 02:01 PM
.. and there is no giant clown getting ready to twist us into a poodle.

Well, there goes my theology out the window!! :lol:

mugaliens
2008-Dec-22, 06:14 PM
Wherever I go, there I are.

Tzarkoth
2008-Dec-22, 06:56 PM
Adding to what Jeff has said so well, there is a concept of "The Visible Universe", which is not the whole universe, but that part of it thet we can collect information about. In the visible universe, we are very near the center, and moving in a specific direction relative to the CMBR.

Could you elaborate on this a little more?

I'm not sure you mean what I think you mean.

speedfreek
2008-Dec-22, 09:08 PM
The visible or observable universe is, as antoniseb put it, the part of the universe that we can collect information about. We collect that information by detecting the electromagnetic radiation coming at us from all directions. This radiation can be radio waves, microwaves, infra-red light, visible light, ultraviolet light, x-rays or gamma rays but they all have one thing in common - they travel at the speed of light.

So if the universe is only 13.7 billion years old, we will only be able to detect electromagnetic radiation that has been travelling for up to 13.7 billion years and this means that we will only be able to see up to a certain distance away - the distance that the radiation has travelled in 13.7 billion years.

The radiation we detect that has been travelling for the longest time is the Cosmic Microwave Background Radiation (CMBR) which was emitted throughout the universe around 300,000 years after the Big-Bang. As it was emitted throughout the universe it comes at us from all directions so you can imagine if you were to ask where all the CMBR photons that we detect today were, say 1000 years ago, then those CMBR photons were all heading towards this position in the universe at that time. They were all 1000 light-years away in all directions from this place, so you could imagine them forming a conceptual sphere around this position, all heading towards it.

But we weren't at this position 1000 years ago.

Due to the peculiar motion of our galaxy within the Virgo cluster of galaxies of which we are part and perhaps the peculiar motion of the Virgo cluster itself, we have a speed and direction relative to that sphere of CMBR photons.

This is my basic understanding of the situation, at any rate.

Durakken
2008-Dec-23, 02:24 AM
We are at the center of the universe...If you were to move to another galaxy...nothing would change.

WayneFrancis
2008-Dec-23, 03:22 AM
The visible or observable universe is, as antoniseb put it, the part of the universe that we can collect information about. We collect that information by detecting the electromagnetic radiation coming at us from all directions. This radiation can be radio waves, microwaves, infra-red light, visible light, ultraviolet light, x-rays or gamma rays but they all have one thing in common - they travel at the speed of light.

So if the universe is only 13.7 billion years old, we will only be able to detect electromagnetic radiation that has been travelling for up to 13.7 billion years and this means that we will only be able to see up to a certain distance away - the distance that the radiation has travelled in 13.7 billion years.

The radiation we detect that has been travelling for the longest time is the Cosmic Microwave Background Radiation (CMBR) which was emitted throughout the universe around 300,000 years after the Big-Bang. As it was emitted throughout the universe it comes at us from all directions so you can imagine if you were to ask where all the CMBR photons that we detect today were, say 1000 years ago, then those CMBR photons were all heading towards this position in the universe at that time. They were all 1000 light-years away in all directions from this place, so you could imagine them forming a conceptual sphere around this position, all heading towards it.

But we weren't at this position 1000 years ago.

Due to the peculiar motion of our galaxy within the Virgo cluster of galaxies of which we are part and perhaps the peculiar motion of the Virgo cluster itself, we have a speed and direction relative to that sphere of CMBR photons.

This is my basic understanding of the situation, at any rate.

Well put. The key here is that we do have a relative motion in respect to the overall universe. In practicality it isn't very large but is still measurable.

Ken G
2008-Dec-25, 07:26 PM
The conventional wisdom is that the Universe is finite but unbounded.There is no observational evidence in support of the idea that the universe is finite but unbounded. It is an example purely of assuming what best fits in our head, which is much more a statement about us and how we like to do science than it is a statement about the universe. We cannot conceive infinity, and we cannot understand how the universe could have a boundary, so if we marry what we can conceive with what we can understand, voila, finite and unbounded. But the history of science is littered with the foolishness of telling reality how to fit into our head, rather than the other way around. As such, it is better to avoid making pronouncements about reality, wise or not, and just talk about our own models of it and why we use them. A finite but unbounded model is consistent with the data, as is a finite and bounded, as is an infinite universe. That's really about all we can say-- so far our accomplishment has been to pretty well rule out the possibility that we will ever be able to tell which of those the universe "really is", leaving us free to design models to our own liking.

cosmocrazy
2008-Dec-25, 11:46 PM
There is no observational evidence in support of the idea that the universe is finite but unbounded. It is an example purely of assuming what best fits in our head, which is much more a statement about us and how we like to do science than it is a statement about the universe. We cannot conceive infinity, and we cannot understand how the universe could have a boundary, so if we marry what we can conceive with what we can understand, voilą, finite and unbounded. But the history of science is littered with the foolishness of telling reality how to fit into our head, rather than the other way around. As such, it is better to avoid making pronouncements about reality, wise or not, and just talk about our own models of it and why we use them. A finite but unbounded model is consistent with the data, as is a finite and bounded, as is an infinite universe. That's really about all we can say-- so far our accomplishment has been to pretty well rule out the possibility that we will ever be able to tell which of those the universe "really is", leaving us free to design models to our own liking.

An excellent post Ken, hitting the nail on the head with "our" perception of how the universe might be. Rather than how the universe might be which we cannot perceive. ;)

Ken G
2008-Dec-26, 12:47 AM
Thanks cosmo-- there's nothing wrong with making models that work for us, but we shouldn't ignore our own role in deciding what that means.