Re: New weight unit!

From a quick scan of t'internet, an average short-beaked echidna can be about 3kg, whereas an adult male red kangaroo can have a mass up to around 90kg (although i thought this would be higher), so I'd say the echidna to kangaroo conversion factor is around the 1:30 mark.

Re: @new weight unit

Much as I love brown session ale (it's my favourite kind) I'd always assumed it was a nice light ale like Enville or HPA.

We just have to know now

What is the speed of a kangaroo in vacuum?

Mine is the one with the roo-leather Barmah hat

Re: We just have to know now

Well, is it an African or European swallow, err kangaroo.

If his audience where he made the quoted comparison was mostly Australian...

...we understood him perfectly well.

The rest of the world is too insignificant to cater to anyway.

@sarev

If you're unfamiliar with echidnas, just think of it as the same as 1.25 bilbies.

Hope that makes it clearer.

Penguin, 'cos everyone knows what they're like.

Re: @sarev

Penguin, 'cos everyone knows what they're like.

There called Tim-Tams (Well they where '99-'00) ar*e end of the world. Nice when used as a straw with a nice cuppa.

Ozzie units...

See, the author was using Aussie Units of Measure, because the article really speaks to the fantastic science that is being done here in Australia (I'm writing this from Melbourne today). Now, IF the US was doing really cool things, then the units would be either robins to deer, or bibles to obese children. You know, things that are common in that country. However, as the majority of the US seems bent on thinking that the world is only 600,000 years old, and that evolution didn't really occur, and that you didn't _need_ a Superconducting Supercollider, and that most public schools should have their budgets slashed for teaching science (expensive subject compared to Home Economics or Gang Looting)...well then, I guess we should get used to more stories with weird, non-American units of comparison. Up next, El Reg will use the silkworm to panda ratio when they discuss just how badly China is out-researching the US...

Re: What about the gaps between galaxies?

Maybe a wallaby

Re: What about the gaps between galaxies?

And what about relative absorption of other, heavier free elements? While there are less of them around, they're heavier. Again, it may not solve the dark matter problem in the calcualtions, but it could provide another echidna or three'2 worth of those 30 echidnas in the Large Kangaroo-sized hole in the equations.

Re: Echidnas?

It'll be the SI echidna.

The one that's kept in a special protective atmosphere at a fixed temperature at an underground location.

Probably in Paris.

Re: Echidnas?

But what is the mass of a football pitch, in Kangaroos?

Re: Echidnas?

European or African football pitch?

Re: Echidnas?

Laden or un-Laden?

Q: what's the difference between yoghurt and Australia

A: culture

An old one but it wears it well.

(an Auk, for variety. Unladen)

Re: It's confirmed by the money as well - !!

Easy, just put 2 kangas on the $2, 5 of them on the $5...

Re: What's fascinating about this

(and the need for dark matter goes away.)

About bloody time too, the sooner we get rid of this magical dark matter, that can't be detected what soever, the better.

Except to balance our accepted theory of the universe, nothing else in astronomy or sub atomic theory, supports it's existence. Either the missing mass is out there in good old fashioned mass somewhere, or our theory of the universe is wrong!

Re: What's fascinating about this

Yep, every time I hear "dark matter" or "dark energy", I'm thinking "phlogiston" and "epicycles".

Re: What's fascinating about this

Dont forget empirical evidence also supported "bad humours" supporting the spread of disease. ie Bad Smell = cause not symptom of illness. Until the microscope was invented it was a perfectly good theory that matched established facts.

Im sure Dark Matter and Dark energy were only created as terms because some stuffy old physicists voted down "Stuff", "Magic" and the "Reversible Sedgewick particle"

Re: What's fascinating about this

I love it when half-informed amateurs wave their magical internet schlongs about and dismiss problems that have been troubling professionals for decades.

Warning: rant ahead

Exactly this. I'm a professional astronomer, but I don't work in dark matter so even *I'm* not a professional on it. In my half-amateur opinion, it gets a bit grating to read people making wide swinging statements like "nothing points to its existence". There are very many reasons to assume the existence of dark matter. Theoretical reasons include virtually any models of particle physics beyond the standard model (and, by the by, the standard model is *wrong*, absolutely, categorically wrong, so we need a model beyond it. Whether that model bears any resemblance to supersymmetric theories is a different matter, but the standard model is definitely wrong). Supersymmetric theories, for instance, which are the most common extensions, predict a "lightest supersymmetric particle". This particle is (meta)stable; it can't decay into normal matter because if it could, it wouldn't be in the supersymmetric sector. The LSP, if such exists (and it seems likely to me that it does, little though I like supersymmetry; alas, the universe wasn't constructed to suit my prejudices any more than it was anyone else's). That makes it a dark matter. It doesn't make it *the* dark matter, but it makes it a dark matter. Have we observed it? No. Will we observe it? Hopefully, though even the LHC isn't guaranteed to get anywhere near it - but it will pin down extensions to the standard model better than we have before.

(Also, neutrinos are a dark matter. Since they have mass, they're a dark matter. Unfortunately they're also not *the* dark matter; there arent enough of them and their mass is far too low. They're what's known as "warm dark matter" -- too fast moving, too light, and not clumping enough. But they're there too. This much we can say with as much certainty as anything in astrophysics.)

Observational evidence for dark matter comes from galactic rotation curves -- which this additional hydrogen alleviates, by a pretty much negligible amount -- and from the motions of galaxies in galaxy clusters -- which it doesn't really address. In both cases we seem to need a lot of dark matter. It also comes from cosmology. To produce the observed amounts of hydrogen, deuterium, helium, lithium etc., you need to very finely tune your model of the universe. In particular, you *cannot* have more than about 5-7% of the critical mass of the universe in the form of normal, standard model matter. But unfortunately the universe is *at* the critical mass, or near as damn it. So 95% of the mass is "missing". This observation doesn't even begin to address this. When you look at the structures in the universe, we can say with high certainty that at most 25% of the universe or so is "dark matter".

That doesn't say it's one thing. Frankly, there are loads of alternatives. There are things like MOND, which fit galaxy rotation curves with astonishing accuracy and require no dark matter, which tells us that *something* interesting is going on... but alas MOND is pure phenomenology, badly motivated, non-relativistic, and no-one treats it as a serious theory (including those who proposed it such as Milgrom and Bekenstein) -- but it's very interesting. What's worse for MOND, it totally falls apart when you try and fit galaxy clusters. Even so, something interesting is going on and dark matter is not the only solution to galaxy rotation curves.

There's also the matter that gravity is geometric. A galaxy would be much better modeled with a cylindrical metric than it ever would in Minkowski space. People can point out to me that the Newtonian potentials remain small so it's Minkowski+perturbations, missing the point that the Newtonian potentials are small *on a different background*, which will be roughly cylindrical. Studies of this are extremely controversial, and at most have suggested that perhaps a fifth of the "dark matter" is actually from geometric effects... and most likely much, much less than that.

There's also the matter that we're simply applying gravity wrongly. You can get things that act like cosmological dark matter from more carefully addressing what "average cosmology" means and quantifying the difference in behaviour between an assumed average behaviour, and the average behaviour of a real universe. But it's never been shown that it's enough.

My hunch, as a relatively informed amateur? Dark matter is all these things. It's composed of neutrinos, of something similar to an LSP, of modifications of gravity a la MOND, of geometric effects we typically naively neglect, of the simple fact we're fitting average behaviours to theories that don't *possess* averages, and most likely other things too.

But in all of that, I also strongly suspect that the dominant contribution is from one or more species of particles. And in any event, there is absolutely no grounds for anyone to say "there is no evidence for dark matter".

Re: What's fascinating about this

So the step from "we have observed this happening" to "some strange stuff must exist which has these properties" is bogus.

Fortunately, no scientist has ever made this step so you can stop worrying about it.

Re: What's fascinating about this

I think Finagle's constant...

http://c2.com/cgi/wiki?FinaglesVariableConstant