Jump to content


Photo

Galactic evolution

  • Please log in to reply
21 replies to this topic

#1 deSitter

deSitter

    Still in Old School

  • -----
  • Posts: 6879
  • Joined: 09 Dec 2004

Posted 10 June 2013 - 10:54 PM

http://en.wikipedia....uence_photo.png

Pretty sad eh? Not much advanced from Air Earth Fire Water.

-drl

#2 Jarad

Jarad

    Fly Me to the Moon

  • *****
  • Posts: 6387
  • Joined: 28 Apr 2003
  • Loc: Atlanta, GA

Posted 11 June 2013 - 06:00 AM

That page is just the classifications.

While I agree that we have a lot to learn about galaxy evolution, at least point to a page that has a bit more info:
http://en.wikipedia....alaxy_evolution

Jarad

#3 Ira

Ira

    Mercury-Atlas

  • *****
  • Posts: 2633
  • Joined: 22 Aug 2010
  • Loc: Mitzpe Ramon, Israel

Posted 11 June 2013 - 09:48 AM

Since we can now look back into space about 11 billion years, why do we not actually see galactic evolution ocurring at different distance/time scales?

/Ira

#4 Jay_Bird

Jay_Bird

    Surveyor 1

  • *****
  • Posts: 1700
  • Joined: 04 Jan 2006
  • Loc: USA

Posted 11 June 2013 - 11:06 AM

I think that we DO see signs of galactic 'evolution' Ira, in the non-biological sense that word is used to describe say, landforms changing over time in response to ongong processes.

The wikipedia link Jarad posted is very good

Deepest imaged fields are 13+ Billion LY

That's 25 times the multicellular fossil record duration (and close to 3 times age of earth itself) so the galactic evolution dots to connect are farther apart compared to the record of life that we might think of as an analogue, and the galactic changes superficially seem more subtle in comparison.

Some things galaxies seem to be doing over time:

+ forming rapidly in early universe

+ getting bigger by collision or accretion

+ forming lots of disk or spiral galaxies - is why disks predominate not fully understood?

+ forming more and larger ellipticals over time by collision

+ galaxy clusters are still gravitationaly bound and coalescing, colliding, interacting in our era

+ maybe central black holes, which seem pretty ubiquitous, are changing over time too, active or quiet, or growing by collision as well?

#5 Ravenous

Ravenous

    Viking 1

  • -----
  • Posts: 607
  • Joined: 14 Nov 2009
  • Loc: UK

Posted 11 June 2013 - 11:27 AM

Quasars are invariably both ancient and distant too, as far as I can remember. A classic example of galaxy evolution.

#6 davidpitre

davidpitre

    Soyuz

  • *****
  • Posts: 3590
  • Joined: 10 May 2005
  • Loc: Central Texas

Posted 11 June 2013 - 02:57 PM

Though Edwin Hubble originally seemed to have thought his classification scheme represented a temporal evolution, it has been recognized for around 90 years that his scheme does not relate to galaxy evolution. Though the terms "early" and "late" are still used, they are not in an evolutionary context.

#7 deSitter

deSitter

    Still in Old School

  • -----
  • Posts: 6879
  • Joined: 09 Dec 2004

Posted 11 June 2013 - 03:35 PM

There is no theory of galactic evolution. There are stupid collision models based on wrong linear computer models. No one has thought seriously about it or published anything serious in decades. Those who would try are hounded out of the clergy.

-drl

#8 Joad

Joad

    Wordsmith

  • *****
  • Posts: 18176
  • Joined: 22 Mar 2005

Posted 11 June 2013 - 03:51 PM

"There is no theory of galactic evolution."

Here's one.

"There are stupid collision models based on wrong linear computer models."

In other words, there are some theories but you don't like them.

"No one has thought seriously about it or published anything serious in decades."

"Serious" and "seriously" are qualifiers, which simply indicate that you are dismissing all the thinking and publishing about this subject on the basis of your own personal insistence.

"Those who would try are hounded out of the clergy."

This is unsupported. Why not tell us exactly what has happened to you, and others, in specific and verifiable detail so your audience can make an independent judgment of your assertions.

[/quote]

#9 llanitedave

llanitedave

    Humble Megalomaniac

  • *****
  • Posts: 22554
  • Joined: 25 Sep 2005
  • Loc: Amargosa Valley, NV, USA

Posted 11 June 2013 - 04:33 PM

I wouldn't normal agree with asking for personal experiences, but Danny, you have made every single one of your assertions, opinions, and critiques here personal. You've either lionized or demonized every scientist in the business, seemingly making your personal character assessments supercede any data -- or lack of it.

Rarely do we get an objective analysis from you. It's all about the saints and the satans.

And that's just not scientific thinking.

#10 Ravenous

Ravenous

    Viking 1

  • -----
  • Posts: 607
  • Joined: 14 Nov 2009
  • Loc: UK

Posted 12 June 2013 - 04:41 AM

First: bear in mind when Mr Hubble proposed this classification, there wasn't even direct evidence what galaxies were. They were thought by many to be "nebulae" not even independent from our our own island galaxy.

Second: based on the above, it was certainly not intended as a proposed evolution.

Third: He was trying to find a good way to classify the structure of these things, whatever they were, for reasons of doing bulk statistics. There was a letter to the RAS I think (sorry I don't have a reference) where he tried to clarify it all, between the lines acknowledging it was all a bit rough and ready. Fascinating reading. Interesting that his first provisional stab at characterising the main features has held for so long.

Fourth: no doubt the current computer simulations/models of galaxy behaviour (evolution and/or collision) will one day be regarded as naive, and there are surely bits missing, but at the moment they're quite useful. Trashing them isn't.

#11 deSitter

deSitter

    Still in Old School

  • -----
  • Posts: 6879
  • Joined: 09 Dec 2004

Posted 12 June 2013 - 11:24 AM

[quote name="Joad"]"There is no theory of galactic evolution."

Here's one.

"There are stupid collision models based on wrong linear computer models."

In other words, there are some theories but you don't like them.

"No one has thought seriously about it or published anything serious in decades."

"Serious" and "seriously" are qualifiers, which simply indicate that you are dismissing all the thinking and publishing about this subject on the basis of your own personal insistence.

"Those who would try are hounded out of the clergy."

This is unsupported. Why not tell us exactly what has happened to you, and others, in specific and verifiable detail so your audience can make an independent judgment of your assertions.

[/quote] [/quote]

I'm just not going to accept a computer model that is almost surely wrong in principle even from the very naive standpoint of only using gravity as the driving force, as a "theory". A theory of galactic evolution would stretch from gas to arms or gas to elliptical halo or whatever. You would not need to even worry about dark matter because that is already a plain error (Cooperstock). I will also point out that there is not even a theory of globular cluster evolution.

What we have is a naive description based on the assertion that GR is absolutely correct as it stands, that plasmas and magnetic fields and other large-scale electrodynamic phenomena are irrelevant, and even then, that a linear model for GR is right. This isn't a theory, it's fancy taxonomy based on half-baked assertions.

-drl

#12 Jarad

Jarad

    Fly Me to the Moon

  • *****
  • Posts: 6387
  • Joined: 28 Apr 2003
  • Loc: Atlanta, GA

Posted 12 June 2013 - 03:03 PM

Well, I agree that at this point in its development we have more of a set of hypotheses than a cohesive theory.

But I disagree that it is as bad as you seem to think. Yes, the hypotheses so far are based primarily on gravity and ignore electromagnetic effects. But those aren't unreasonable assumptions - the net charge of objects at large scale tends to be close to 0. And while we can see intense local magnetic fields, magnetic field strength drops of with the cube of distance vs. the square for gravity, so again at large scales gravity will dominate.

I think plasma currents and magnetic effects are probably important in terms of stellar collapse in supernovas, and in the behavior of accretion disks and jets, and I think those explosions and jets are probably important to early galaxy development, so I agree they probably have important indirect effects that still need to be explored. But it's not easy to take measurements of those things over great distances, and it's hard to develop good theories on them in the absence of data.

We still have lots to learn, I just think it would be more productive to pick a piece and work on it than to point out that we still have lots to learn. Especially if you point it out in a less than diplomatic fashion - that tends to make people stop listening...

Jarad

#13 Classic8

Classic8

    Viking 1

  • -----
  • Posts: 550
  • Joined: 12 Apr 2006
  • Loc: Naperville, IL, USA

Posted 12 June 2013 - 07:53 PM

This is a somewhat different question, but is there any discrepancy between the level of organization of galaxies and how much time they needed to form, according to current models? Is dark matter required for them to have formed as quickly as they did?

#14 Joad

Joad

    Wordsmith

  • *****
  • Posts: 18176
  • Joined: 22 Mar 2005

Posted 12 June 2013 - 08:42 PM

Danger, Will Robinson!

Let's put it this way: the reason why astrophysical theory appears to have stalled is not because of some conspiracy on the part of physicists, nor because physicists today are stupid or venal or anything of the sort, but because technological advances in the past couple of decades have triggered an avalanche of data that have never before been available. Those data have presented problems and have left a lot of unanswered questions. Two of those unanswered questions involve apparent (please note the word "apparent") universal expansion beyond what would be expected according to current understanding, and various observed phenomena that appear to require a lot more gravitational mass than can be observed. Not yet knowing for certain what is behind such observations, physicists have coined the terms "dark energy" and "dark matter," in a gesture of humility. I have seen Cal Tech physicists themselves note, with humility, just how little they know.

So my point is that it probably isn't a good idea to base a theory of anything based upon "dark matter" until "dark matter" ceases to be dark and is fully understood or discredited.

#15 sirchz

sirchz

    Vostok 1

  • -----
  • Posts: 152
  • Joined: 21 Sep 2009

Posted 13 June 2013 - 12:28 PM

Yes, the hypotheses so far are based primarily on gravity and ignore electromagnetic effects. But those aren't unreasonable assumptions - the net charge of objects at large scale tends to be close to 0. And while we can see intense local magnetic fields, magnetic field strength drops of with the cube of distance vs. the square for gravity, so again at large scales gravity will dominate.


Just a comment that charge neutrality doesn't imply electromagnetic effects aren't important. I'm not saying they are important, just that this argument doesn't really justify neglecting them.

If applied to a Hydrogen atom it would say that electromagnetic effects can be ignored, but we know they are very important.

Plasmas are quasi neutral by definition and electromagnetism drives their properties and behavior.

#16 Jarad

Jarad

    Fly Me to the Moon

  • *****
  • Posts: 6387
  • Joined: 28 Apr 2003
  • Loc: Atlanta, GA

Posted 13 June 2013 - 01:21 PM

If applied to a Hydrogen atom it would say that electromagnetic effects can be ignored, but we know they are very important.



Depends on what you are calculating about the hydogen atom and what scale they are on. Eletromagnetic effects are very important in determing chemical reactions with the hydrogen atom, but those happen at the atomic scale where separation of charge is significant. In terms of calculating the attraction between one hydrogen atom and a second one a few meters away in a vacuum, we can neglect the electrmagnetic effect and only consider gravity.

On a more macro level, van der waals forces are electromagnetic, and are quite important for how two materials in close contact react with each other (how sticky they are, how much friction, etc.). But again, they have zero impact on how two bodies orbit each other in space.

Plasmas are quasi neutral by definition and electromagnetism drives their properties and behavior.



So that brings us to the question of scale again. We know there are plasma currents within stars, for example. And we are pretty confident about them in accretion disks. But do we have any evidence of them on a galactic scale? Not that I am aware of.

So rather than complain about lack of plasma and magnetic effects in the model, perhaps it would be more productive to think about how we would detect such effects if they really exist. Then we can get some useful data to help develop a better theory.

Jarad

#17 Joel F.

Joel F.

    Apollo

  • *****
  • Posts: 1392
  • Joined: 19 Mar 2006
  • Loc: Overland Park, Kansas

Posted 13 June 2013 - 04:40 PM

Perhaps the most complee reference to dat on galaxy evolution is the book "Galaxy Formation and Evolution" by Houjun Mo, Frank van den Bosch, and SimonWhite published in 2010 (with 820 pages).

However, it may already be out of date. In the 2012 issue of Annual Reviews of Astronomy and Astrophysics there is an article on hot galactic halos at perhaps one million degrees. Thus therare plasmas and at that temperatue have significant currents. A bit latter an article was published in which there may be some evidence of very significant baryonic mass in these halos.

It is also important torealize that galaxies do have magnetic fields. Also, a hydrogen atom has a magnetic moment, but a hydrogen molecule does not. Thus, the hydrogen atoms ten to be polarized and held in place by these magnetic fields. However, the hydrogen molecule is more easily displace by a disturbance.

#18 Neutrino?

Neutrino?

    Messenger

  • *****
  • Posts: 419
  • Joined: 14 Dec 2009
  • Loc: Wasatch Front

Posted 13 June 2013 - 05:12 PM

This is a somewhat different question, but is there any discrepancy between the level of organization of galaxies and how much time they needed to form, according to current models? Is dark matter required for them to have formed as quickly as they did?


Yes. Without it, the epoch of the formation of galaxies would have started later and thus would not match current observation.

#19 Joad

Joad

    Wordsmith

  • *****
  • Posts: 18176
  • Joined: 22 Mar 2005

Posted 13 June 2013 - 06:35 PM

"You would not need to even worry about dark matter because that is already a plain error (Cooperstock)."

Sorry, but that cannot be allowed to stand on a science forum. I've done some research on F.I. Cooperstock with regard to his alternative ideas about using GR, rather than Newtonian physics, to calculate galaxy rotation figures.

First, he is a bona fide astrophysicist; his papers have been accepted for publication in peer reviewed publications; and, all in all, he (along with his major co-author) has some very interesting ideas. Because of this he has been taken seriously, and other astrophysicists have assessed his conjecture, and, especially in a paper referring to measurements within the Milky Way galaxy, they have refuted his conjectures in a way that the scientific community has accepted (given the silence on Cooperstock's work since about 2007).

This is not to diminish Cooperstock's intelligence, ability, or sincerity in the least. It sounds like he has been doing good theoretical science, just as it should be done. But he hasn't done away with dark matter.

This is all made clear by a review of papers at Cornell University's arXiv.org.

#20 sirchz

sirchz

    Vostok 1

  • -----
  • Posts: 152
  • Joined: 21 Sep 2009

Posted 14 June 2013 - 12:42 PM

So rather than complain about lack of plasma and magnetic effects in the model, perhaps it would be more productive to think about how we would detect such effects if they really exist. Then we can get some useful data to help develop a better theory.


I don't disagree and would be surprised if E&M effects were critically important. They may play some role, but for now ignoring them seems reasonable to me. I was merely being pedantic.

#21 Starman1

Starman1

    Vendor (EyepiecesEtc.com)

  • *****
  • Vendors
  • Posts: 23139
  • Joined: 23 Jun 2003
  • Loc: Los Angeles

Posted 15 June 2013 - 07:22 PM

This 9-page article will illuminate many things about galactic evolution:
http://aramis.obspm....sciam-19aug.pdf

#22 CounterWeight

CounterWeight

    Cosmos

  • *****
  • Posts: 8202
  • Joined: 05 Oct 2008
  • Loc: Palo alto, CA.

Posted 18 June 2013 - 11:40 AM

In the McScience press we are treated to McFactoids. In other places there is a lot of publication going on based on data and mostly scientific method, not nearly as exciting or headline grabbing. And we are learning often just how much we don't know, but would like to learn about. I look at the Hubble 'tuning fork' as a natural consequence of what was understood at the time, 'nearly nothing'... and in the spirit of Darwinism. 'perception based', it was in ways thought of as science at the time though there were those that felt more research necessary and it was possibly a bit pre-mature.

I gave a talk on this topic some years ago and one thing prevails. As we look for more and always find more, our concept of a galaxy has changed accordingly. Looking at visual wavelength pictures we were able to grasp a certain amount, and sending satellites up and using radio we find the structure and energy distributions different again. The largest features of galaxies being invisible to us at our visual sensory level.

But taking a step back, consider for a moment the Voyager program in our own solar system, if it wasn't for the more primitive 'Pioneer' program Voyager would have been burnt out by the massive radiation field (profiled by the Pioneer) around Jupiter. There is so much more here. The speed of matter in the atmosphere of the planets as a function of temperature took some time to understand, and there are some things about that we still have difficulty with. Matter and temperature and energy - seems simple, but not simple. In our lab's on earth we know that matter has some extremely interesting characteristics and even some bordering on extraordinary phenomena at very low temperatures, not just the ho-hum members of the periodic table but the isotopes as well!. Every bit as interesting as that at the other end of the temperature spectrum. And area wise the lions share of the universe as we understand it is not at that very high temperature end of things, just an extremely interesting tiny fraction of it - and that we can easily see. Not encountered in everyday life in the 'habitable zone' here on Terra.

So there are 'laws' and there are 'laws' and then the math's that we manipulate them with according to our understanding and experience. These 'math's' are evolving as well.

How computers can help is then when we get some perceived insight we can model extraordinarily difficult ideas, even many at a time and 'see' the results, try and compare that to other observation. The idea of 'observing', binoculars, telescopes, radio telescopes, gamma ray and infra-red satellites and each time we see something we modify accordingly and try to go to a next step in the understanding. Try as we might, it is still observational as we as humans function in a large way by the input from those things going right to the center of our brains - very helpfully so. Here the computer can be a helper, but it does not replace the brain, which I feel is the only thinking machine that makes sense in any organic way 'at large'.

In a humorous way the galaxies we have been observing have not evolved nearly as much as our ability to see them, and each time we see more they are still the same - it's our (or at least some that are interested) perception of them that changes, and we are too largely the same for the effort. And we still have that periodic table and Helium which is very interesting stuff!

Plasma is also interesting stuff. Light and dark. Swaths of it light years long at extremely low temperatures of photonically activated at less than low temperatures all over the galaxy disks.

Our brain at this point is the only satellite that can encounter these things.

"The Secret Sits

We dance round in a ring and suppose, But the Secret sits in the middle and knows" Robert Frost



Sometimes I feel as though with all the publicizing and hunger to fill web page and other space that someone is hoping for 'a lucky shot' and it will all somehow congeal into a compact and succinct understandable whole. Analyzing computer algorithms and comparing to other data. Could happen, then too might not. One new satellite with one new type of data could hurl it off the throne. That said, with the massive increase in media and folks access to it, desire to get research $$, the rise of science - especially cosmology and relativistic cosmology as entertainment has increased. This is very important, keeping it in the public conversation while asking for massive amounts of funding. Is it a distraction from scientific method because it is entertainment? Maybe for the easily distracted.






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics