The Misbehaving Universe

[CraigS]

Here’s an interesting one on the state-of-the-art in Spiral Galaxy formation modelling.
The following words caught my eye:

Being able to simulate a complex system like the formation of the Milky Way realistically is the ultimate proof that the underlying theories of astrophysics are correct.

Hmmm ... when it comes to theory in science, there is no ‘proof’, so we can dispense with that statement pretty quickly, but what does this exercise really then represent ?

In their simulation, the spiral galaxy shape forms on its own. In the model, they're tracking the behaviours of individual components of a galaxy comprising 790 billion solar masses and 18.6 million particles .. a huge number crunching task !

Principles Used (Inputs):
- cold dark matter paradigm;
- physical laws of gravity;
- fluid dynamics;
- radiophysics.

Model Outputs (Results):
- stars form in giant high density cold molecular gas clouds;
- star formation and distribution not uniform - clumped, clustered;
- heat build up by supernova explosions;
- visible matter accelerated to high redshifts by these explosions;
- removal of this matter from the core results in a concave disk;
- this results in the correct stellar mass as per observations;
- at the end, a thin curved disk forms corresponding to measured mass, angular momentum and rotational velocity ratios.

General Litmus/Reality Tests:
- can’t have too many stars at the centre;
- the overall stellar mass can’t be several times bigger than observed.

Predictions:
- distributions of stars and hot gases for the outer halos of the Milky Way (currently technologically, beyond detection).

There’s also a whole lot of extra ‘tweaks’ they’ve recommended going forward (of course).

Coming back to answer my original question though, to me, what it is they’ve actually shown, is that from the known individual component behaviours, a spiral shape forms which matches fairly closely to what we observe at the macro-scales .. which in itself, is amazing! That this happens, shows us that the universe is capable of forming galaxy shapes, which are not immediate directly relatable (in quantifiable terms), with the known individual component behaviours. (Ie: the whole is different from the sum of its parts).

If this is the way the universe behaves overall, then why should we ever expect the behaviours at any given level of scale, to necessarily be the same at the next level up or down ?

Cheers
PS: For anyone interested, the paper describing the model is here.

[renormalised (Carl)]

Well, damn it, send it to its room without any supper!!!!

[renormalised (Carl)]

It's not a matter of misbehaving. You haven't seen the forest for the trees. A forest doesn't have the same morphology as the trees which make it up. What is happening, is that the patterns of morphology at the micro and meso scales, when taken as a whole, drive other patterns at the macro scale which may bear little resemblance to those smaller scale patterns. Their combined effect creates the spiral patterns of the galaxies and in turn the megascale patterns also influence the others at the smaller scales. None can be taken in isolation, except if all you're studying is those particular patterns/processes. However, in order to truly understand what is happening at any scale, you must consider the whole system. This applies to any science...let alone astronomy. Actually, it applies to anything we do.

In order to study how the spiral density wave creates and drives the spiral structures in galaxies, you must know how the stars form within them and what other processes/patterns occur within them. And, in order to understand how the stars form and the clouds of dust and gas are related to this process (and others), you must also know how the spiral structures of these galaxies work. It can't be escaped.

The problem with being overly reductionist is that you lose sight of the interrelationships between the apparently disparate pieces of the whole. That is a big problem with science...this over reliance on reductionism and pigeon holing of everything. In many cases, more knowledge can be gained by considering the whole, rather than the parts.

[CraigS]

I think we're roughly on the same page here .. its very interesting this ..

Originally Posted by renormalised

A forest doesn't have the same morphology as the trees which make it up. What is happening, is that the patterns of morphology at the micro and meso scales, when taken as a whole, drive other patterns at the macro scale which may bear little resemblance to those smaller scale patterns.

I don't think there is a need to invoke a "driving process" between the various levels of scale. If there is no evidence of one in nature and the pattern spontaneously forms in the simulation, I don't think we can say that this is happening.

Originally Posted by renormalised

Their combined effect creates the spiral patterns of the galaxies and in turn the megascale patterns also influence the others at the smaller scales.

I can see that there is iteration at the lower-scale level, (the outputs from one step in time feed back, as inputs to the next), that's actually the function the computer performs in the model.
Maybe there's also a natural feedback process at this same level of scale in the real thing, also.
But once again, I can't see a need for invoking feedback between this level, and say, the next one up, when the simulation forms the pattern without such a mechanism.

Originally Posted by renormalised

In order to study how the spiral density wave creates and drives the spiral structures in galaxies, you must know how the stars form within them and what other processes/patterns occur within them.

I really don't think there is any such thing as a "driving spiral density wave". I think the fact that the spiral shape appears spontaneously without any cause, suggests that it is nothing more than an illusion, which our pattern-recognition sensors pick up. There is not necessarily any "driving force" (of nature) behind it. The structure merely self-assembles in this pattern, because of the behaviours of the individual parts, at the lower scale.

Originally Posted by renormalised

And, in order to understand how the stars form and the clouds of dust and gas are related to this process (and others), you must also know how the spiral structures of these galaxies work. It can't be escaped.

Once again, I don't think there are any "workings" we can attribute as being at cause in creating the spiral structure .. there is no need for any such mechanism, as it appears purely because of interactions between the 'standard' behaviours, of the lower scale components.

Originally Posted by renormalised

The problem with being overly reductionist is that you lose sight of the interrelationships between the apparently disparate pieces of the whole. That is a big problem with science...this over reliance on reductionism and pigeon holing of everything. In many cases, more knowledge can be gained by considering the whole, rather than the parts.

I whole-heartedly agree !

Cheers

[CraigS]

PS: The "Misbehaving" term in the title of this thread is intended as a tongue-in-cheek reminder, that it is not nature that's misbehaving … more likely, it is that we are expecting something to be at "cause" for the spiral pattern, which didn't actually turn up!!
How dare it !!
I'm gonna call that "misbehaving" !

Cheers

[avandonk]

The only quantum computer than can mimic the Universe is the Universe!

Bert

[CraigS]

But Bert … we align our lifestyles to live in accordance with what these models are telling us.

Should I stop doing this ?

[renormalised (Carl)]

Originally Posted by CraigS

I think we're roughly on the same page here .. its very interesting this ..

Most certainly

Originally Posted by CraigS

I don't think there is a need to invoke a "driving process" between the various levels of scale. If there is no evidence of one in nature and the pattern spontaneously forms in the simulation, I don't think we can say that this is happening.

If there is no connection between the scale level processes other than some randomly generated pattern at the macroscale level of structure, then any shape could be generated from the processes...any shape that obeyed all the physical laws which govern the interaction of systems. Maybe we don't "see" a connection in nature because we're too busy looking at the components and not the whole system. It's like saying here we have a human, but that human bears no relation to what their cells are doing. We may not even see the connections simply because we don't recognise any. Did that pattern spontaneously form in the simulation because it was just going to happen, or did the conditions that were programed into the individual components within that simulation, when taken as a whole, generate that spiral pattern due to the interactions between its components. Then, did the spiral become self sustaining because it was just something of consequence or did the pattern that was generated influenced the particles at the smaller scale.

Originally Posted by CraigS

I can see that there is iteration at the lower-scale level, (the outputs from one step in time feed back, as inputs to the next), that's actually the function the computer performs in the model.
Maybe there's also a natural feedback process at this same level of scale in the real thing, also.
But once again, I can't see a need for invoking feedback between this level, and say, the next one up, when the simulation forms the pattern without such a mechanism.

Again, is it just a matter of consequence and coincidence or do they both interact with one another to produce the results given. It's very easy to just say there's no connection since we can't see one, but that is probably a case of missing the point, so to speak. Nothing happens in isolation, anywhere. It's why you have to be careful when using laws/theories of physics to describe what is happening in the Universe. They can only be approximates. They act as a set of ground rules and initial scaffolding to hang your ideas/observations on, but they never tell you the whole picture. There's always room for improvement. That's why theories come and go. Some theories hold good for a long time, others drop by the wayside rather quickly. But, no theory is immutable.

Originally Posted by CraigS

I really don't think there is any such thing as a "driving spiral density wave". I think the fact that the spiral shape appears spontaneously without any cause, suggests that it is nothing more than an illusion, which our pattern-recognition sensors pick up. There is not necessarily any "driving force" (of nature) behind it. The structure merely self-assembles in this pattern, because of the behaviours of the individual parts, at the lower scale.

It's in part because of the spiral density wave moving through the cold, molecular clouds of the galaxies that we have any stars in the first place. A cold cloud of gas is just going to sit there and do nothing unless something prompts it to collapse and form stars.

Now, that's where you're going right out on a limb and stretching quite a few physical laws...spontaneous generation with no causative mechanism. That's tantamount to creation from nothing, which is one reason why laypeople find digesting what scientist say about the BB rather difficult and gives the looney tunes brigade their ammunition to go on with what they do. The reason why scientists say things like the BB (or in this case the spiral pattern in galaxies) has no cause is that they don't understand the mechanisms behind it very well, if at all. You can't have laws of physics saying one thing and then totally disregard one of the underlying principles behind them (cause and effect) just because you can't fathom why something happens, given your present state of understanding. There's quite a bit we do understand, make no bones about that, but we do waffle on too much and dig our own graves when it comes to making pronouncements on areas of knowledge we've barely begun to even figure out, let alone know what's happening.

There's nothing wrong with self assembly in natural systems or even spontaneous generation due to interactions at a lower level in the whole system. However, there has to be a cause and an effect which generates the final result. This could be an area where chaos theory and fractal mathematics excel in because it's pretty clear that it's the patterns created through a vast number of variables interacting with one another at all sorts of levels which eventually build to the structures that we see.

Sometimes, even illusions can have a reality all of their own. We may know they're illusions, but we still perceive their existence and reality.

Originally Posted by CraigS

Once again, I don't think there are any "workings" we can attribute as being at cause in creating the spiral structure .. there is no need for any such mechanism, as it appears purely because of interactions between the 'standard' behaviours, of the lower scale components.

Mechanisms are not necessarily just one causative "force" driving a system to attain anything in particular. A mechanism can be the sum of a complex set of interactions between an infinite number of variables which ultimately create a "desired" effect within a system. The sum of all the causative behaviours generate the whole which becomes greater than the sum of its parts. The whole then affects the standard behaviours of the lower level components.

Originally Posted by CraigS

I whole-heartedly agree !

Cheers

We all have to be careful in our approaches to understanding these things. There's also a downside of seeing too much forest and not enough trees, too. In looking too heavily at the big picture, you can miss the little things which are generating the problems or processes as the case may be. You need to take a balanced, holistic approach. That way, hopefully you won't miss anything important and you might come to an understanding of what you're studying...or, at least, the snotty nosed little undergrad that's going to be a future postgrad student of yours will come to that understanding. After you check into the big science lab in the sky, that is

[renormalised (Carl)]

Originally Posted by CraigS

PS: The "Misbehaving" term in the title of this thread is intended as a tongue-in-cheek reminder, that it is not nature that's misbehaving … more likely, it is that we are expecting something to be at "cause" for the spiral pattern, which didn't actually turn up!!
How dare it !!
I'm gonna call that "misbehaving" !

Cheers

What if it's just our interpretation which is heretical....either way and depending on your PoV. Nature might be doing something, saying, "Hey, you in the lab coat with the pocket protector, leaky pens and buck-teeth. Look at me!!!!", and because we don't have a clue at what we're looking at or doing, we're the ones who are actually misbehaving

[renormalised (Carl)]

Originally Posted by avandonk

The only quantum computer than can mimic the Universe is the Universe!

Bert

Precisely, because to mimic the Universe, the quantum computer must contain the same number of qubits as the Universe itself. In order to model its processes down to the nth level, you have to have the same level complexity as the test subject itself. Otherwise, you just get an approximation.

[xelasnave]

I simulate a galaxy formation when my tea bag breaks and the milk powder clumps stir it up and ....

Most interesting.
Now they need a number of galaxies to see how/if they intereact during formation.

alex

[CraigS]

Originally Posted by xelasnave

I simulate a galaxy formation when my tea bag breaks and the milk powder clumps stir it up and ....

Most interesting.
Now they need a number of galaxies to see how/if they intereact during formation.

alex

G'Day Alex;

Somewhere is all this, I read that it took the supercomputers 8 months to create this simulation, and it would take a PC 570 years to come up with the same result.

Can you imagine how long it would take to come up with what you're suggesting ??

Cheers

[sjastro]

Can you imagine how long it would take to come up with what you're suggesting ??

Cheers

About as long as the EU crowd using an abacus.

Steven

[renormalised (Carl)]

Originally Posted by sjastro

About as long as the EU crowd using an abacus.

Steven

I thought they'd be using their fingers and toes, instead

[CraigS]

Originally Posted by CraigS

I really don't think there is any such thing as a "driving spiral density wave". I think the fact that the spiral shape appears spontaneously without any cause, suggests that it is nothing more than an illusion, which our pattern-recognition sensors pick up. There is not necessarily any "driving force" (of nature) behind it. The structure merely self-assembles in this pattern, because of the behaviours of the individual parts, at the lower scale.

Originally Posted by renormalised

Now, that's where you're going right out on a limb and stretching quite a few physical laws...spontaneous generation with no causative mechanism. That's tantamount to creation from nothing, which is one reason why laypeople find digesting what scientist say about the BB rather difficult and gives the looney tunes brigade their ammunition to go on with what they do. The reason why scientists say things like the BB (or in this case the spiral pattern in galaxies) has no cause is that they don't understand the mechanisms behind it very well, if at all. You can't have laws of physics saying one thing and then totally disregard one of the underlying principles behind them (cause and effect) just because you can't fathom why something happens, given your present state of understanding. There's quite a bit we do understand, make no bones about that, but we do waffle on too much and dig our own graves when it comes to making pronouncements on areas of knowledge we've barely begun to even figure out, let alone know what's happening.

Yes Carl … fair enough, too. My words may have been misleading.
There is clearly a cause .. that would be the non-linear behaviours which take on a life of their own, once the smaller scales interact with eachother, within the simulation. So I guess one can point to this as the 'cause'.

What I meant to say, is that it is not caused by something external which takes on the form in our thinking of a physical "spiral density wave".
If we give such a thing the ontological status of say a primitive entity that can be demonstrated by experiment, then it should be able to be described separately from its constituents ... and I don't think we can do this for "a spiral density wave" .

Also, there are systems which have feedback operating between dissimilar levels of scale … which produce a verfiable cause and effect on the components. Eg: I can kill off a few thousand brain cells by having a few drinks, eh ? This would be a different system from the ones simulated in the model we're talking about here, though.

Cheers

[xelasnave]

Originally Posted by CraigS

G'Day Alex;

Somewhere is all this, I read that it took the supercomputers 8 months to create this simulation, and it would take a PC 570 years to come up with the same result.

Can you imagine how long it would take to come up with what you're suggesting ??

Cheers

Yes Craig I noted their work and it would be a major task but why not... think of the time that can be wasted on developing a mere game...
alex

[avandonk]

Originally Posted by CraigS

But Bert … we align our lifestyles to live in accordance with what these models are telling us.

Should I stop doing this ?

Our minds have evolved for survival and enjoyment of life in the biosphere of Earth. Even if our brains work at the quantum level it is still remarkable we can begin to model the Universe which is far outside our needs for mere survival or earthly material enjoyment. I was just pointing out that our feeble efforts can only be at best a very poor approximation of reality. That does not mean we should stop trying. Even a negative experimental result carries meaningful information.

Consider this statement.

A brain that thinks it could fully understand it's own workings would be very feeble indeed!

If I had a full answer to your last question I would be omniscient and you know who HE/SHE is!

Bert

[CraigS]

Understood.
I know others have been around this loop a few times, and the points raised are usually very consistent, but I always find it difficult to reconcile how we can dismiss our 'best effort' complexity models, as merely very poor approximations of reality, whilst at the same time, we embrace them, in a manner which asserts the opposite (in terms of the reality of their predictive capabilities) (??).

It seems that we have invented something, which our brains are incapable of classifying, using reality as the reference. (And that is regardless of whether they actually represent a likeness to reality, or not !)

Cheers

[avandonk]

Craig when you are on a modern airliner at 40,000 feet while having a meal that you would not feed to your dog just think that outside it is -50C and the air is too thin to breathe. This airliner was built by approximate models and trial and error. We do not fully understand airflow and complex structures but we get away with our approximate models as long as we stay within the parameters that we think we understand.

We cannot do better than this. We are bound by our own ignorance. It is the few that that dare to go outside this comfortable envelope that gives us more understanding. It is simply by asking better questions that progress is made in our finite knowledge.

Godel showed we can never know all without paradoxes that cannot be disproved or proved. It is this indeterminism that makes our Universe so complex. Determinism leads inexorably to simplicity. Ask any fundie.

I prefer to live in a very complex Universe even if I do not fully understand it. I also do not need to invoke a mythical entity that oversees it all. We are all surviving on our own efforts not some sky god that some idiot invented to explain the rather large bit he did not understand!

I always think that we humans are are bit like two ants crossing my infinite carpet and one ant says to the other see that everchanging glowing image I know how it works. This ant now makes himself leader and arbiter of morality and laws for his fellow ants. They were watching home and away on my TV!

Bert

[renormalised (Carl)]

Turn up the volume and they'll think it's the voice of God, Bert

All you'll need then is a burning bush

And a few slabs of rock with some scratches on them

Or, maybe the TV guide