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The AEL Goes AudioVisual (Astrophysics)
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Mick Harper
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Well actually, Grant, AE says that a minority is just as much an orthodoxy as any other group. It is only when you are alone, when your view is unique, that yours is an AE viewpoint.

AE does not judge validity on how many people hold a view but nonetheless it does urge the consideration of minority views since much of value resides there. But of course everybody believes they hold minority views -- this is the true wonder of the age.
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Grant



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Mick wrote
But of course everybody believes they hold minority views -- this is the true wonder of the age.

That's certainly true. What always amazes me about liberals is how when they mouth their platitudes about racism, sexism, socialism blah blah blah, they always imply that they are being radical and in some sort of free-thinking minority.
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Grant



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Just finished watching SCUM. That's Mick's version not the Ray Winstone film.

I find it amazing that Mick can take a entire science and make me question the basic assumptions which were beaten into my unquestioning mind by the various popular science books I read as a child.

But as I look back I think I had some doubts then (or is that just the benefit of hindsight?). I think I remember being surprised that the heavy elements all came from supernovas, but how could it be wrong? Someone's writen a book about it and it was in the last edition of Look and Learn! That way we learn orthodoxy.

But Mick, I have a question. Is the universe full of dead planets mostly unconnected to living stars? Could this be where all the dark matter is hiding?
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Mick Harper
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Is the universe full of dead planets mostly unconnected to living stars?

I don't see that this is really possible. I suppose there are always going to be some waifs and strays but I assume that the age of the universe and the nature of gravity dictates that most will have homed in on still shining stars by now. But of course we won't know for certain until observational technology is way beyond what we have now.

Could this be where all the dark matter is hiding?

'Dark Matter' is a classic illustration of a Paradigm Defence, Emperor's Clothes Variant. Something doesn't add up so you invent a balancing item to slide into the equation. You make sure it is, by definition, impossible to see. Hence the sums now not only add up but the theory cannot be overthrown by advances in 'observational technology'. The theory is now immortal.

But of course it still might be true. If we take the present solar system and observe that twenty-five bodies are now earth-sized or less but used to be Sun-sized (ono) then where has all that missing mass gone? Gone to dark matter every one...as Peter, Paul and Mary nearly put it.
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Grant



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Mick wrote

If we take the present solar system and observe that twenty-five bodies are now earth-sized or less but used to be Sun-sized (ono) then where has all that missing mass gone?


And we need at least 25 times the amount of matter we can see to justify the motion of the galaxies. But I don't understand why the planets have to encircle live stars. Why can't they rotate around gas giants or larger rocks or even black holes if they exist?
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Grant



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Mick wrote

But of course it still might be true. If we take the present solar system and observe that twenty-five bodies are now earth-sized or less but used to be Sun-sized (ono) then where has all that missing mass gone?


Do the math(s). In our part of the universe only one object out of twenty-five is still live. But we can only live in a region displaying this characteristic. The rest of the universe must have a ratio of dead to live which is much higher.
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Mick Harper
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But I don't understand why the planets have to encircle live stars. Why can't they rotate around gas giants or larger rocks or even black holes if they exist?

But all this actually happens in SCUM. As I point out most of the 'planets' actually do 'rotate around' gas giants, it's just that the gas giants in our solar system happen to 'rotate around' a still shining star. Gas giants are still small compared to shining stars so presumably they will always have a tendency to gravitate towards them. But there might be loads out there, we have no way of knowing either way.

However there is reason to suppose that our Solar System will be the general case (leaving aside black holes which may or may not exist and may or may not have 'planets' nearby who haven't fallen in yet). Since gravity is dictated by mass it follows that small bodies will gravitate towards large ones. They cannot not be attracted and once captured there is no escape, so the current Solar System will be the norm in any fairly mature galaxy

Do the math(s). In our part of the universe only one object out of twenty-five is still live. But we can only live in a region displaying this characteristic. The rest of the universe must have a ratio of dead to live which is much higher.

I make this point specifically in my critique (hah!) of the Main Star Sequence.
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Rocky



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I was reading this article
http://www.vancouversun.com/technology/Victoria+native+makes
+astronomical+discovery/1790839/story.html

Rita Mann has cast her eyes skyward and found something previously unseen: a binary star-disc system with two distinct areas of mass capable of forming a pair of planetary arrays.

[She] spotted two stars about 1,300 light years from Earth that are linked by gravity and orbit a common centre. The unusual thing is that each star is surrounded by a distinct ring of substances with enough mass to form planets like those in our own solar system.

“People have been saying that because the sun is alone, and lone stars are very rare, maybe the Earth is very rare or the planets are very rare. I think this shows for the first time that even when stars are born in groups or in pairs, discs of stuff out of which planets can form are still there,” Navarro said.


Why is this significant? Can someone explain? It seems like it's saying that two stars formed and there was some residual stuff floating around.
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DPCrisp


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...If we take the present solar system and observe that twenty-five bodies are now earth-sized or less but used to be Sun-sized (ono) then where has all that missing mass gone? Gone to dark matter every one...as Peter, Paul and Mary nearly put it.

Dark Matter being nothing more exotic than matter we can't detect... except that otherwise unexpected behaviour would normally count to anyone (including past astronomers) as a means to detect previously unknown matter. So that's everything from chunky stellar cores to supernova dust, everywhere from connected to unconnected to living stars; all too cold and/or far away to show up. D'you suppose a gert mass of cooling-down stuff might give off -- Oh, I don't know -- say, microwaves everywhere you look in the cosmos, almost like a background?

Why is this significant? Can someone explain? It seems like it's saying that two stars formed and there was some residual stuff floating around.

To them, it's big news because they can't get excited by the bleedin' obvious unless they have the relevant experimental result. And because everything is news, because they are so specialised, individual horizons very small. And everything has to be reported as though it's a big deal. So to get quoted you have to say it's a big deal...

To everyone else, it's bleedin' obvious. What's more important to us is the way such news is treated and the context in which this could be treated as a discovery. Is their thinking really so confined to the results already obtained... if not to extravagant flights of fancy?

Gaping holes left (highlighted) here include whether these discs of material will ever form planets and how on Earth a pair of stars form. The account of our Solar System is all wrong, so don't expect to find the answers over the page.

Maybe they did think it through... and concluded that you can have either a star plus planets, or a star plus another star... in which case their surprise points to what we already knew: they haven't got a bleedin' clue.
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Rocky



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DPCrisp wrote:

Maybe they did think it through... and concluded that you can have either a star plus planets, or a star plus another star... in which case their surprise points to what we already knew: they haven't got a bleedin' clue.


But there's nothing special or fundamental about a two-star system compared to a one-star or n-star system is there?
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DPCrisp


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But there's nothing special or fundamental about a two-star system compared to a one-star or n-star system is there?

Well, if you start with a spinning cloud, you get a disc of material with a star at the centre... so single stars ought to be fundamental, with 2+ requiring some further explanation... but binaries are actually in the majority, followed by solos and then 3+... but the spinning-cloud-cum-accretion-disc flannel doesn't work for a single star, let alone 2 or more. They haven't a bleedin' clue.
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Rocky



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Here's some animated pictures for various barycenter configurations:
http://en.wikipedia.org/wiki/Center_of_mass#Animations

It says in the fifth picture, that that is a common configuration for a binary star system - two bodies with similar mass orbiting around a common barycenter with elliptic orbits.

Why is this more common for a binary star system than the configurations in any of the other pictures?
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DPCrisp


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The short answer is that elliptical orbits are normal: a circle is a special case of an ellipse, but it takes work to make an orbit circular. (Actually, I don't know of any.)
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Rocky



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And there aren't any solar systems with exactly two objects either, are there?
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DPCrisp


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Dunno whether we can tell that yet. Binaries are common... and they make a fuss every time they find what they take to be planets (and they have to be giants to be spotted) or the potential for planets ("accretion discs"), so I guess all those binaries are not known to be accompanied by other stuff... but they may yet prove to be.
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