Starship Asterisk*

http://apod.nasa.gov/apod/ap080131.html

I an not an astronomer or scientist so these beautiful images are mostly "eye candy" for me. I am humbled both by the people that make these images available to us and the very intelligent people that post to further enlighten those of us searching to be enlightened.

This image for some unknown reason set me to wondering about the relationship between time and distance as viewed from earth. If I understand correctly If the universe were large enough and we could see far enough we would see the original event at that point

emc wrote: If the universe were large enough and we could see far enough we would see the original event at that point

I am no scientist but as I understand it you would not be able to see the light but you may be able to see the 'heat'. This heat left over from the big bang shows up in the form of microwave radiation (and is named the cosmic microwave background (CMB) radiation).

NASA's WMAP mission seeks out this CMB to 'map' this radiation. See the article titled "New Three Year Results on the Oldest Light in the Universe" http://map.gsfc.nasa.gov/m_mm.html

Also you can read a blurb on the history here: http://map.gsfc.nasa.gov/m_mm/sg_earlyuniv.html

emc wrote:This image for some unknown reason set me to wondering about the relationship between time and distance as viewed from earth. If I understand correctly :?: If the universe were large enough and we could see far enough :?: we would see the original event at that point :?:

Something like that. There was no "point" in the usual sense; any 3D point in the Universe can be considered the center. When we look farther- in any direction- we see farther back. But there is a limit to how far we can see using light because the earliest Universe was opaque to light. Since we can't see the Big Bang directly, we have to infer its properties based on how the earliest galaxies (which we think we have seen) appear, what their distribution is like, and other things that are observable.

Does anyone know how stars in clusters move? In the case of Westerlund 2, I expect they would be moving as a group around the galactic center, but within the cluster, are they also moving about a common gravitational center? If not, what keeps the cluster from collapsing in on itself?

npsguy: the WMAP CMB timeline http://map.gsfc.nasa.gov/m_ig/060915/CMB_Timeline75.jpg indicates there is a center point but...

Chris: says that

There was no "point" in the usual sense; any 3D point in the Universe can be considered the center.

I understand the WMAP CMB timeline graphic is only a schematic showing in simple terms what WMAP is teaching us (BTW thanks for the links) but my desire to understand almost requires that there be a tangible single point of origin we can locate or at least know which direction to look.

Chris: I don't believe I do, but if I understand what you are saying - there are multiple origins spread throughout the universe

emc wrote:I understand the WMAP CMB timeline graphic is only a schematic showing in simple terms what WMAP is teaching us (BTW thanks for the links) but my desire to understand almost requires that there be a tangible single point of origin we can locate or at least know which direction to look.

Chris: I don't believe I do, but if I understand what you are saying - there are multiple origins spread throughout the universe :?: :?: :?:

There is no direction you can look. The "center" doesn't exist in three-dimensional space, and therefore we can't see it. There are not multiple origins at all. Any direction we look is towards the [one] origin... the farther we look, the closer we are to it.

Chris Peterson wrote:

There is no direction you can look. The "center" doesn't exist in three-dimensional space, and therefore we can't see it. There are not multiple origins at all. Any direction we look is towards the [one] origin... the farther we look, the closer we are to it.

Sorry but I am still confused... if there is no direction we can look and the origin lies outside the 3 dimensions we reference but at the same time we can look deeply in any direction and be closer to the origin... has thrown me into a tail spin.

I can understand why we can't see the origin if we are looking back into time and can't see that far. And the farther we look the closer we are to it...

I hope you can forgive my ignorance, and I appreciate you patient answers... What is still holding me back is that if the universe has been expanding then how can the origin be away in every direction? Maybe I just can't shake my simple 3D roots?

emc wrote:Sorry but I am still confused... if there is no direction we can look and the origin lies outside the 3 dimensions we reference but at the same time we can look deeply in any direction and be closer to the origin... has thrown me into a tail spin.

I can understand why we can't see the origin if we are looking back into time and can't see that far. And the farther we look the closer we are to it...

I hope you can forgive my ignorance, and I appreciate you patient answers... What is still holding me back is that if the universe has been expanding then how can the origin be away in every direction? Maybe I just can't shake my simple 3D roots?

Our whole existence is based on those 3D roots, so shaking them isn't easy. I'm afraid there's no rule that says everything about the Universe needs to be obvious or intuitive.

First, lets distinguish between the origin in terms of time and the origin in terms of space. We can observe the former if we can see something far enough away (although as previously noted, we can't observe with photons quite to the very beginning). But we don't observe the latter in any meaningful way because, at least in 3D space, it doesn't exist as a point.

There is a popular analogy used to describe the Universe, using a balloon. It has been used here and elsewhere, and is very useful if not misused. You are asked to imagine that the balloon represents the Universe, expanding outwards from the center. But unlike the real Universe, this is a 3D universe with a 2D surface. The entire contents of this universe lie on the surface of the balloon. Points on it are getting farther from each other with time. Beings living on the surface could look all around, but not "up" or "down" because those directions don't exist for them. It is obvious to them that their universe is expanding, but there is no center of expansion on the 2D surface they have access to. Some 2D Einstein might work out the math demonstrating that this universe is actually undergoing a 3D expansion, but most of his 2D friends won't really grasp what that means in any intuitive sense.

Now try to extend that analogy to the Universe we live in. All matter and energy lies on the 3D surface of this 4D universe. There is a center of expansion (the origin of the Big Bang) but it doesn't lie on the 3D surface we can study. Theory predicts this center, and the theory is well supported by experimental evidence, but we still can't observe that center directly.

By looking at distant objects we can learn about conditions near the beginning of the Universe, because we see those objects as they were. But we don't see them where they were with respect to the Big Bang, because every point [we can see] is equidistant from the origin, and always has been.

Chris: I think I understand a better now... equidistant from the center in 4D made it a little clearer. Again, thanks for your willingness to share and patient answers! I believe I understand God in a similar fashion to your 4D model.

I admire you folks that can wrap your heads around the mechanics of the cosmos. I am doing well to find my way back to my 'tree' each day

Agreed. That was damned good, Chris!

-Noel

zbvhs wrote:Does anyone know how stars in clusters move? In the case of Westerlund 2, I expect they would be moving as a group around the galactic center, but within the cluster, are they also moving about a common gravitational center? If not, what keeps the cluster from collapsing in on itself?

There's two types of star clusters, open and closed.

In an open cluster, the stars are not gravitationally bound, meaning they have enough momentum to escape the group. As I understand it, open clusters are really just chance concentrations of stars.

Closed clusters are gravitationally bound. There isn't sufficient mass to pull the group into the pretty flat spirals like galaxies, but the stars generally do tend to move about a common, if difficult to pinpoint, gravitational center.

And of course, the group as a whole moves around the galactic center.

iamlucky13 wrote:There's two types of star clusters, open and closed.

That should be "open" and "globular".

In an open cluster, the stars are not gravitationally bound, meaning they have enough momentum to escape the group. As I understand it, open clusters are really just chance concentrations of stars.

The stars in an open cluster are gravitationally bound, although not so tightly as in a globular cluster. As a result, open clusters tend to be very young, since they are easily disrupted.

NoelC wrote:Agreed. That was damned good, Chris!

-Noel

Hi Noel: I feel a little funny this morning... so thought I would point out the dichotomy of your comment... "damned" and "good"... if I were an alien monitoring APOD trying to learn english I think I would be confused... ... but hey, maybe that's a good thing!

Chris is very good at explaining his mind, but we don't want to give him the big giant head... we have enough ground based astro visual challenges from clouds already. ... Hence, Chandra and Spitzer... 8)

Our MILITARY INTELLIGENCE discovered
that the JUMBO SHRIMP tasted
DAMNED GOOD

Chris Peterson wrote:...

Aha...I had a feeling I mixed up some of the details. Thanks for correcting it.

excellent photo