Hahaha. I like the part in the AiG article about ‘historical science’. So very much compartmentalization is required for a scientist to accept such a distinction.
On a ‘tangential’ subject to whirling galaxies, I remember reading about the challenges associated with explaining the rotational momentum of galaxies and how cosmologists weren’t sure what the answer to that was. I don’t recall how many years ago I read the article, and as you can see, I’m not recalling the details. But can anybody shed light on the “conservation of rotational momentum” challenge, and elaborate as to if cosmologists have since settled on plausible explanations?
I guess it is (or was?) known as the “Angular momentum problem”, at least as titled in this 2009 paper.
So, just to help me visualize things a bit better, the “spinning arms” of a spiral galaxy really are not spinning stars that circle the center of the galaxy, but rather stars that are born and burn out in what we see as arms, but are actually gravity waves of some sort, sort of like a bay filled with bio-luminous organisms, stimulated by passing waves? Or is that off base?
Hi Merv,
I think that paper covers the angular momentum problem for galaxies pretty well.
Anything that collapses has to get rid of rotational energy, because small initial rotations become more intense during collapse and start to counteract the collapse. This holds for proto-galactic clouds (to become galaxies), proto-stellar clouds (to become stars), and proto-planetary clouds (to become planets). There are different solutions for these different scales, but it boils down to radiating away the energy one way or another. It is an interesting exercise to determine “how” exactly energy is radiated away, but it does not cause sleepless nights for astronomers because more realistic models are leading to better solutions all the time. For example, in the paper you linked to, the authors took into account how exploding stars (supernovae) help to diffuse energy and that led to improved results.
Not sure whether that answers your question, but that’s about all I can tell you.
Hi Phil,
The spiral arms start as density waves in the galactic disc, caused by gravitational effects (watch out: not to be confused with “gravitational waves”, which are ripples in spacetime itself, something totally different!). A local increase in density tends to attract more mass (mostly in the form of gas and dust clouds, but also already formed stars), further increasing the density. That increased density spurs on the formation of new stars, which are very bright and blue of color, which is why spiral arms are generally bright and blue (seen in the picture). However, in simulations these stars don’t usually “die” in the spiral arm where they are born. Instead, they move on and travel ahead of the spiral arms, just as cars manage to leave behind the traffic jam on the highway at some point. Hope that helps to make sense of it.
Casper
Thanks for the explanation. The more you learn, the more amazing it all becomes.
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I’m fascinated by the work you mention on computer simulations. In the early 1970s I was a research assistant at NRAO. Computers in those days were enormous mainframes, and CRTs (some with the capability of showing as many as 16 colors) were only just beginning to be used to interface with them. (The programs I wrote for the staff astronomers were all submitted on punched cards.)
My memory is certainly faded, so don’t bet the ranch on this, but I seem to recall that one or two of the astronomers were messing around with simulations to see how star clusters and galaxies might possibly form as a result of gravitational interaction. I think the number of “stars” (i.e., mathematical points in the program) was limited to just a few hundred, since the machines couldn’t do more than that without blowing up, but the results were pretty interesting to watch.
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Thank you for sharing this, Ted. I love to hear stories that bring into perspective the scientific and technological developments of the past decades. It helps me to appreciate how amazing the opportunities are that we have nowadays in science.
This is a tangent, but I am also looking forward to the kinds of stories that might be told another few decades from now. Me and my younger brother differ just six years in age but it already seems like we grew up in different worlds. I still remember how we used the phone cable to get a few minutes of internet, while my brother has grown up with WiFi everywhere.
Thanks Casper. To be honest, I didn’t read the paper I linked to (but just used it to recall the name given to the challenge.) I should probably do that, though many other matters also vie for my attention right now.
Meanwhile I remember being impressed by having read a similar paper years ago that used this very explanation (collapse and then the counter-effect of greater angular velocity) to explain the flat disk shape of galaxies. I.e. galactic matter ejected from such a spinning system would tend to take on planar features. It made so much sense to me at the time, but from what you say about how the spiral arms themselves are explained, I may need to modify my mental model for how this works. Is it still true to say that our sun does have a somwhat stable orbital velocity around the galactic hub?
Yes, the sun orbits at a roughly constant velocity of 220 km/s around the galactic center, as do most stars that make up the rotating galactic disc. The disc became so flat due to a balance between collapse and rotation, I think that is what you are also referring to. (Though no ejection of matter occurs, the system shrinks from a huge diffuse proto-galactic cloud to a much smaller, much denser galactic system.)
Collapse results in a relatively flat, rotating system: the disc, which then allows for the formation of spiral arms. The most important characteristic of spiral arms is the increased density of stars/gas/dust. When our sun heads towards a spiral arm, it gets pulled forward slightly on its orbit. When it moves away from that spiral arm, it gets slowed down slightly. That slight “stalling” becomes visible in luminosity when you take into account billions of stars, plus the important fact that the increased density also triggers the birth of new (extra bright) stars.
So you don’t have to make any major revisions to your mental model, I suppose 
.
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One revision for my model will be that I was visualizing the arms as being moving stars in their own right – a bit like imagining visible stream-lines in a fluid that get warped into a spiral as the fluid (say, water) spins faster and faster the closer to the drain it is. Not that our galaxy is collapsing toward center – but just as a picture of my old model where the direct motion of the particles themselves are making a spiral pattern. It sounds though like the “spiral arms” are more of an emergent effect (the traffic jam as you called it) of something a bit more complicated (at least for what it takes to understand its origins). Thanks for your continued explanation.
-Merv
-heard recently: “we are not in a traffic jam; we are part of the traffic jam.”
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Fascinating stuff. Our tendency is to see it as something we are familiar with, like the rotating turbine fan blades of a jet engine, and it is interesting that the spiral arms are really much different.
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It is difficult to overcome confirmation bias when locked in a false choice between YEC and “godless Darwinism.”
This false choice is the real problem, not the false science presented.
Interesting critique of the YEC scientific approach to astronomy and indeed cosmogony.
It does raise a few eyebrows though in the following statements:
- " With my own eyes, I had seen computer simulations of galactic discs in which spiral arms formed by themselves and persisted for billions of years"
- " Recent simulations have shown that these spirals form naturally and easily remain stable over the course of billions of years."
Firstly, you can correct me if I’m wrong here, aren’t galaxies supposed to “form” all by themselves over billions of years?
AS far as I know there is no direct and clearly confirmed observation that shows how stars “form all by themselves” and then furthermore how galaxies can form all by themselves consequent to that fact. If there is such a recent real life observation I’d be delighted to examine that documentation.
Secondly, you might have seen with your own eye a real life simulation - but a simulation is in now way the exact representation of physical reality - and indeed is subject to our own mental biases. The starting assumptions in all simulations are critical to the outcome.
Thirdly, you seem to use the simulations as “fact” of newer knowledge that makes that of Dr Faulkner outdated. Is this how science works these days? In the absence of real, confirmed observations ( which by the way are currently out of our reach since no one can go back in history or live that long) of star and galaxy self-formation we now resort to relying on our fractured and positively meagre knowledge of cosmogony to infer that our simulations represent “fact”. Is this how science works these days?
Furthermore, relying on CDM as explanation for galaxy formation is unfortunately not in the realm of science. It again lacks true observational evidence at this point and relies on inference, no matter how good the data is. Of course the inference is based on certain assumptions which have not been confirmed and indeed cannot be tested.
Indeed one can even make the valid claim that very little if anything in cosmology/cosmogony is science at all.
Hi Prode,
You seem to have some fundamental misconceptions about what science actually is, how it works, and what role assumptions actually play in the matter.
First of all, before you dismiss the starting assumptions of simulations as “just assumptions,” you need to demonstrate that you know what those assumptions actually are. You then need to explain (a) exactly how they could be violated, and (b) exactly how such violations would affect the outcome. Dismissing simulations as “meh, assumptions” without being able to answer these questions is not science — it is cluelessness.
Simulations may be “only” approximate representations of physical reality, but you need to be able to demonstrate that the approximations are sufficiently large to invalidate the conclusions.
Basically, you need to know what you’re talking about.
Are you aware of how much research goes into trying to reduce or minimise the effects of mental biases? Or how many protocols are set in place? Ever heard of double-blind studies, for example?
Yes it is. When new data comes in, it allows you to either refine or invalidate your models. That’s how science has always worked. Who told you otherwise?
Prode, you need to realise something important here. The “were you there?” argument is wrong. I believe this has been explained to you before: science works by making testable predictions and by cross-checking results. Neither of these require you to have “been there.”
Also, where do you get the idea that our knowledge of cosmogony is “fractured and positively meagre”? Yes there are a lot of unanswered questions, but have you any idea how much data cosmologists actually work with, or how many peer reviewed papers have been published on the subject? I’m guessing here (and @Casper_Hesp may probably be able to provide a better idea), but it wouldn’t surprise me if you see one of these things turning up at NASA, Jodrell Bank or CERN from time to time:
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Hi Prode,
Thank you for responding with these critical questions and comments.
I am equally delighted to present you with that documentation. There is plenty of evidence of ongoing star formation in the universe. The “Pillars of Creation” are a very famous example, dust clouds that are currently forming stars and are being eroded by the light of new-born stars:
The wavelengths of light emitted from inside these pillars correspond very well with expectations based on our theoretical understanding of star formation.
Concerning galaxy formation, we observe many galaxies with very different characteristics in the universe (e.g., in terms of color, presence of heavy elements, star formation rates, lumpiness). Current understandings of galaxy and star formation explain these differences very well. For example, such properties nicely track the history of our universe:
Faulkner claims in “Is Genesis History” that galactic spiral arms form a problem within the cosmological standard model. The simulations I discussed were based on the assumptions of the standard model and produced long-lived galactic spiral arms. They are therefore direct evidence against Faulkner’s claim that galactic spiral arms are problematic. Despite being an oversimplified representation of reality, these simulations produce results that correspond with observations. Simplicity is actually a strength of such computational work, not a weakness.
I think I have addressed your third point too with this. Yes, these simulations produce new knowledge concerning the formation and stability of galactic spiral arms within the standard model, making Faulkner’s claim outdated. Also, it allows for comparison with the abundant observations of “real, confirmed” galactic spiral arms, thanks to our telescopes…
Dr. Faulkner himself actually disagrees with you concerning dark matter. He even wrote an article for Answers in Genesis, in which he argues that the idea of dark matter is legitimate science:
That assertion might have been valid in the first half of the 20th century, when little data was available to constrain cosmological theories. However, cosmological science has made great progress ever since. As an interesting example, scientists have predicted and observed the cosmic microwave background, radiation left over from the early universe:
I hope all of that helps to address your concerns!
Casper
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Hi Adam, Good questions. I am not an astronomer, but I do understand some things about the scientific process, so I will share some thoughts.
It is not scientific in the least to assert that new data such as dark matter create problems for a model. You actually have to
- perform computational simulations that incorporate the new data,
- Get peers to review the work, then
- Publish your findings publicly.
Faulkner has skipped directly to the 3d step without performing the first two. Therefore his conclusions are not scientific; they are, at best, informed speculation.
Moreover, much scientific work has been done since Faulkner’s 2011 article. Hesp’s article incorporates findings from this recent work.
As for the supposed non-evolution of galaxies, I would point out that Faulkner has not given us any data. Given an ancient universe, what differences would we expect between older and newer galaxies? Which of those differences do not appear?
Finally, even if I were to in arguendo accept everything in Faulkner’s article, I would conclude that the universe is very young, as indicated by the blue stars in spiral galaxy arms. This would imply a universe that is a few million years old, not a universe that is 8000 years old. Why does Faulkner use the phrase “very young” instead of giving a number?
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