APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Comments and questions about the APOD on the main view screen.
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Anthony Barreiro » Mon Jan 20, 2014 6:01 pm

geckzilla wrote:That's very odd, Ann. Heat death has to be the most depressing possible end the Universe could face. The idea that it could one day collapse and then be somehow reborn again in a new big bang was quite cheerful.
If there were going to be a "big crunch" (and now we believe there won't), what reason is there to believe that it would have been followed by another big bang, other than hope and faith?

It's quite remarkable that we're able to see (or hear!) back to the cosmic microwave background radiation just a few hundred thousand years after the big bang, and to infer that the expansion of the universe is currently accelerating. But extrapolations backward and forward in time rest upon foundations of assumptions piled on assumptions. Maybe we've finally made all the right assumptions and none of the wrong ones, but history suggests otherwise.
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Ann » Mon Jan 20, 2014 6:14 pm

geckzilla wrote:That's very odd, Ann. Heat death has to be the most depressing possible end the Universe could face. The idea that it could one day collapse and then be somehow reborn again in a new big bang was quite cheerful.
Well, am I a claustrophobiac or am I a claustrophobiac?

Please, universe, don't do this to me (and don't make me think it could ever happen on a cosmic scale):
Click to play embedded YouTube video.

Slightly more seriously, I agree with Anthony. What reason do we have to think that a big crunch would be followed by another big bang? And if there was another big bang, what reason do we have to think it would give rise to a universe where stars, planets, let alone sentient beings could exist?

(And Anthony, you are probably right about the assumptions piled upon assumptions. Oh well. It is interesting to be alive and see what astronomy is going to come up with, that much is certain.)

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Chris Peterson » Mon Jan 20, 2014 6:45 pm

Ann wrote:What reason do we have to think that a big crunch would be followed by another big bang?
If all the energy comes back together, it merely opens up the possibility of a cyclic universe. That doesn't seem possible with a universe that expands forever.
And if there was another big bang, what reason do we have to think it would give rise to a universe where stars, planets, let alone sentient beings could exist?
Not much reason at all to make any assumptions. But again, if it is possible, it is probably only possible in a Big Crunch scenario.
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Dustin M. » Mon Jan 20, 2014 7:51 pm

I am not sure I understand this either but here is what I think I might understand. Tell me if I am wrong. I believe we have actually observed these filaments of stars in our current universe. The black voids would then be a form of repulsion pushing matter away? Like a repulsive force that has cleared out a region of space from stars while pushing the stars that are into dense filaments because there are so many of these expanding voids? These regions are all throughout space like little pockets of repulsive force or maybe it is expanding space? Over a long distance all these expanding spaces or repulsive forces are pushing the universe apart?

Would they have any idea what it is that is in these pockets that is making these voids? Maybe this is what the author of the drawing is wondering because he drew something in the center of the bubble.

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Anthony Barreiro » Mon Jan 20, 2014 7:55 pm

Ann wrote:
(And Anthony, you are probably right about the assumptions piled upon assumptions. Oh well. It is interesting to be alive and see what astronomy is going to come up with, that much is certain.)
Yes, we live during interesting times. I wonder how many people understand the math and physics of the Lambda - Cold Dark Matter cosmological model well enough to even be able to articulate its assumptions, let alone to question them. Fortunately cosmology is almost entirely abstract from our human lives, so even if the cosmologists are completely wrong about everything, it won't hurt anyone, except maybe a few post-docs and assistant professors whose dissertations were published two weeks before a major theoretical breakthrough.
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Chris Peterson » Mon Jan 20, 2014 7:59 pm

Dustin M. wrote:I believe we have actually observed these filaments of stars in our current universe.
We do observe filamentary structure, although it is far less organized than this APOD might suggest.
The black voids would then be a form of repulsion pushing matter away? Like a repulsive force that has cleared out a region of space from stars while pushing the stars that are into dense filaments because there are so many of these expanding voids? These regions are all throughout space like little pockets of repulsive force or maybe it is expanding space?
No, the structure isn't caused by any sort of repulsive forces. It is a fossil of acoustically generated structure in the baryon plasma of the very, very early universe.
Over a long distance all these expanding spaces or repulsive forces are pushing the universe apart?
Dark energy seems to be responsible for pushing the entire universe apart. But it's on a scale larger than the voids in the cosmic bubbles.
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Chris Peterson » Mon Jan 20, 2014 8:18 pm

Anthony Barreiro wrote:I wonder how many people understand the math and physics of the Lambda - Cold Dark Matter cosmological model well enough to even be able to articulate its assumptions, let alone to question them.
Only a few understand the math well enough to question it, or to add new knowledge. Quite a few more understand the physics well enough to articulate it. And there's no reason that anybody of reasonable intelligence and education can't understand the model reasonably well (or any other ideas of modern science, for that matter).
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Dustin M. » Mon Jan 20, 2014 8:28 pm

I did a search but haven't found anything yet that I can tell. Are there any papers out that could be referenced that explain why these voids are not what is causing this expansion of the universe on a large scale? Would I be correct then in assuming that the expansion of the universe will push these voids apart making them less dense? Do they believe the dark energy that is pushing the universe apart is coming from a certain point in the universe or is it coming from everywhere.

Here is the song that came to mind when it was mentioned not to fear the death of the universe. http://www.youtube.com/watch?v=ZdXfkkyI1nQ

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Boomer12k » Mon Jan 20, 2014 8:39 pm

It is very interesting....as....they look like ATOMS.....a Central Nucleus, with a surrounding Field...or Ring of others...in this case, Galaxies...

But I think it is the wrong depiction....as the Structure of the Universe, and I would think even back then, would be more like a FILAMENT...but maybe after so much time, that Atom-like structure broke apart, or changed....

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Chris Peterson » Mon Jan 20, 2014 8:40 pm

Dustin M. wrote:I did a search but haven't found anything yet that I can tell. Are there any papers out that could be referenced that explain why these voids are not what is causing this expansion of the universe on a large scale?
That's not really a subject of research, not the sort of thing you'd normally find a paper about. Rather, you'll find papers about BAOs, which describe observations and their relationship to the early universe. More generally, people don't usually write papers about why things don't act in certain ways. Before somebody would argue that the voids aren't responsible for universal expansion, somebody would first have to offer evidence that they are.
Would I be correct then in assuming that the expansion of the universe will push these voids apart making them less dense?
Not necessarily. Dark energy pushes things apart that are very far apart. It cannot overcome gravitational attraction on a smaller scale.
Do they believe the dark energy that is pushing the universe apart is coming from a certain point in the universe or is it coming from everywhere.
Dark energy appears to be a property of space, or of the vacuum. As such, it pervades the Universe.
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Chris Peterson » Mon Jan 20, 2014 8:43 pm

Boomer12k wrote:It is very interesting....as....they look like ATOMS.....a Central Nucleus, with a surrounding Field...or Ring of others...in this case, Galaxies...

But I think it is the wrong depiction....as the Structure of the Universe, and I would think even back then, would be more like a FILAMENT...but maybe after so much time, that Atom-like structure broke apart, or changed....
This image shows the universe in its evolved state, similar to today. It does not show the early universe. And the circles are simplifications, to illustrate the concept of periodic density fluctuations. The actual filaments we observe don't lie on nice spherical surfaces, but exhibit more complex shapes.
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Boomer12k » Mon Jan 20, 2014 8:50 pm

Well....The Universe is Energy.....of ALL TYPES.....

I guess that is what makes it so fascinating....

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Boomer12k » Mon Jan 20, 2014 8:54 pm

Chris Peterson wrote:
Boomer12k wrote:It is very interesting....as....they look like ATOMS.....a Central Nucleus, with a surrounding Field...or Ring of others...in this case, Galaxies...

But I think it is the wrong depiction....as the Structure of the Universe, and I would think even back then, would be more like a FILAMENT...but maybe after so much time, that Atom-like structure broke apart, or changed....
This image shows the universe in its evolved state, similar to today. It does not show the early universe. And the circles are simplifications, to illustrate the concept of periodic density fluctuations. The actual filaments we observe don't lie on nice spherical surfaces, but exhibit more complex shapes.
Yes...it said about HALF it's current age, so, I was not commenting on it being the Early Universe...but the depiction makes it appear to be less Filamental...and more uniform...but then it is just an "Artists Conception"....

Maybe those outer lanes became the filaments, like in the Sound and sand demonstration....are we just a changing sound???? As I observed earlier...The Universe is Energy....We are Energy...

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by neufer » Mon Jan 20, 2014 8:59 pm


Anthony Barreiro wrote:
Ron-Astro Pharmacist wrote:
In this tutorial Mark Whittle gives us a bit of the repercussions of the acoustic universe.
http://www.astro.virginia.edu/~dmw8f/BB ... _home.html
Thanks, Ron. I was going to make the same suggestion. Whittle explains big bang acoustics very clearly and accessibly. He even includes sound clips of what the universe would sound like if it were in a frequency range perceptible to human ears.
In space everyone can see the universe scream. :arrow:
http://en.wikipedia.org/wiki/The_Primal_Scream wrote:
<<The Primal Scream. Primal Therapy: The Cure for Neurosis is a 1970 book by Arthur Janov, the inventor of Primal therapy. The book describes the experiences Janov had with 63 patients during his first 18 months (starting in 1967) discovering and practicing Primal therapy. Janov claimed in the book a 100% cure rate. The book, which has been called "incredibly popular", was read by tens of thousands of Americans and brought Janov fame and popular success. This inspired many therapists who had not met Janov to start offering imitation primal therapy, and led to the proliferation of programs offering happiness through radical personal transformation.>>
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by bayareajohn » Mon Jan 20, 2014 10:00 pm

So glad to have this cleared up.

Huh?

It's especially nice to know that the baryons ripples are 2-dimensional and all aligned on a plane perpendicular to our view, it makes it so much easier to understand.

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Nitpicker » Mon Jan 20, 2014 11:27 pm

Chris Peterson wrote:Here's an analogy. Ripples form on the surface of a pond because of the way sound travels in water.
I stumbled at the first hurdle of your analogy. Ripples form on the surface of a pond because of some external force acting on the pond. The nature of water in a constant gravitational field, and the conservation of mass, momentum and energy is what causes the ripples to propagate. Sound propagates through water as longitudinal waves because of the nature of water. Sounds waves travel a lot faster through water, than the ripples on the surface, which propagate as a combination of transverse and longitudinal waves.

...

Whilst I think I get the fact that scientists are exploiting the natural existence of some kind of resonance in the universe, to make these distance measurements (and resultant findings on dark energy), I've decided to stop there. I'm not ready to jump in to the deep end of this topic just yet. I'm heeding Psnarf's cartoon.

Edit reason: can't spell.
Last edited by Nitpicker on Mon Jan 20, 2014 11:40 pm, edited 2 times in total.

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Chris Peterson » Mon Jan 20, 2014 11:36 pm

Nitpicker wrote:I stumbled at the first hurdle of your analogy. Ripples form on the surface of a pond because of some external force acting on the pond. The nature of water in a constant gravitational field, and the conservation of mass, momentum and energy is what causes the ripples to propagate. Sound propagates through water as longitudinal waves because of the nature of water. Sounds waves travel a lot faster through water, than the ripples on the surface, which propagate as a combination of transverse and longitudinal waves.
This is the risk that comes from overanalyzing a simple analogy.

The point is, by studying the ripples in a pond it is possible to make inferences about the material properties of water (including the velocity of sound in water) without actually having any water to examine directly. Indeed, if the water has changed to vapor and you are studying the ripples that have survived to that point, you may be inferring properties of something that doesn't even exist anymore.
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Nitpicker » Tue Jan 21, 2014 12:00 am

Chris Peterson wrote:This is the risk that comes from overanalyzing a simple analogy.

The point is, by studying the ripples in a pond it is possible to make inferences about the material properties of water (including the velocity of sound in water) without actually having any water to examine directly.
Fair enough. But I would be interested in how to derive the speed of sound in water, from nothing more than visual observations of surface waves. I didn't think that was possible.

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Chris Peterson » Tue Jan 21, 2014 12:03 am

Nitpicker wrote:Fair enough. But I would be interested in how to derive the speed of sound in water, from nothing more than visual observations of surface waves. I didn't think that was possible.
It may not be. But that's not to say that you couldn't use the ripples to place constraints on the speed of sound in the water, or that if you had separately derived a value for the speed of sound in water using some other theory, that the structure or frequency observed in the ripples couldn't either disprove that theory, or bolster it.
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by FearNot » Tue Jan 21, 2014 12:11 am

Chris Peterson wrote: Suppose a burst of hail hits a pond, creating thousands of individual ripple rings. These run into each other, producing a complex surface that we can observe. We'd certainly not see anything like circles in that surface .
Depends on when we observed the surface .. if we observed at time of impact we'd certainly see the circle rings. But in any case, and as you infrer, if we observed water surfaces struck by objects often enough we would see what the circles become .. patterns of great beauty with histories to tell which we could understand if we studied the examples enough.

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by geckzilla » Tue Jan 21, 2014 12:19 am

Is this kind of like measuring the speed of light with a microwave and a hot dog? http://imgur.com/gallery/uiwcv
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Chris Peterson » Tue Jan 21, 2014 12:22 am

FearNot wrote:
Chris Peterson wrote:Suppose a burst of hail hits a pond, creating thousands of individual ripple rings. These run into each other, producing a complex surface that we can observe. We'd certainly not see anything like circles in that surface .
Depends on when we observed the surface .. if we observed at time of impact we'd certainly see the circle rings. But in any case, and as you infrer, if we observed water surfaces struck by objects often enough we would see what the circles become .. patterns of great beauty with histories to tell which we could understand if we studied the examples enough.
But considering the intent of this analogy, we can't observe the hail when it hits. In the case of the early universe, the sound waves were traveling through the baryonic plasma prior to recombination- earlier than 377,000 years, at a time when the Universe wasn't transparent and we can't observe it. The ripples we observe now are the fossil structure of those acoustic oscillations, billions of years after the conditions that allowed them to form ceased to exist.
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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Boomer12k » Tue Jan 21, 2014 1:45 am

Neufer's side ways picture from SDSS III website...is very interesting....the background radiation, and the spaces or gaps there....appear to be PROJECTED into present time...only larger....the expansion.

This is like STEAM...the water vapor rising, and expanding outward, and the physical elements spreading, and the cooling process condensing the vapor into larger, more solid droplets, of more mass....and as they continue, those droplets will dance around with other droplets....

So...we have a radiated, super heated vapor of energy, that as the Universe expands, it cools...and the matter condenses into more and more matter, that clumps together, forming Filaments of Galaxies,....and the expanding space in between them, and leaving this pattern, of voids....and that is a projection of the Resonance of the Energy from the beginning of the Universe...Amazing....

We are not JUST an Expanding Universe....but a Condensing Universe....at the same time...

This is like a Projection of light...when you see a movie, or a slide from a Projector,....the IMAGE, is very small at the source,...and the spaces...are very small...but when projected to the wall, or a movie theater....they become very large and noticeable. I have a mini-DLP projector...it fits in your hand...I can project a 50-80 inch image...that small internal image, becomes expanded....just like the depiction of the SDSS III page....

Like with the Heat of Steam....the Heat of the Energy at the beginning of the Universe...that radiation...I think...causes the expansion...and is the so called "Dark Energy"....perhaps???? But even after a bullet is fired, and the projectile is well away from the initial expansion of gas...it can continue on with its momentum, and inertia...without further influence from the original gas. As Space has ever decreasing pressure...maybe things are just continuing along...I wonder when and where that originating Energy started to dissipate, or is it still continuing on as the "Matter of the Universe", keeping its momentum as a different substance.

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Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Dustin M. » Tue Jan 21, 2014 2:12 am

Chris Peterson wrote:
Dustin M. wrote:I did a search but haven't found anything yet that I can tell. Are there any papers out that could be referenced that explain why these voids are not what is causing this expansion of the universe on a large scale?
That's not really a subject of research, not the sort of thing you'd normally find a paper about. Rather, you'll find papers about BAOs, which describe observations and their relationship to the early universe. More generally, people don't usually write papers about why things don't act in certain ways. Before somebody would argue that the voids aren't responsible for universal expansion, somebody would first have to offer evidence that they are.
Would I be correct then in assuming that the expansion of the universe will push these voids apart making them less dense?
Not necessarily. Dark energy pushes things apart that are very far apart. It cannot overcome gravitational attraction on a smaller scale.
Do they believe the dark energy that is pushing the universe apart is coming from a certain point in the universe or is it coming from everywhere.
Dark energy appears to be a property of space, or of the vacuum. As such, it pervades the Universe.
If there hasn't been any research yet into the idea that there could be a repulsive force in those voids pushing the universe away then how can we be so sure that this isn't the case and that it has to be something that happened a long time ago but is not occurring any more? if the repulsive force of dark energy pervades the universe on a massive scale then maybe it could be distributed similar to these voids? Not saying that this is the case, but I don't see how it can be eliminated if no one knows for sure.

Dustin M.

Re: APOD: Baryon Acoustic Oscillations from... (2014 Jan 20)

Post by Dustin M. » Tue Jan 21, 2014 2:22 am

Chris Peterson wrote:
Dustin M. wrote:I did a search but haven't found anything yet ...
On second thought I will say you are right. People generally don't try and prove what isn't possible. They do generally look into what is possible. I should have phrased it if any Papers were known of that support the idea. Please excuse my poor choice of words.