## The Accidental Astrophysicists 97

An anonymous reader recommends a ScienceNews story that begins:

*"Dmitry Khavinson and Genevra Neumann didn't know anything about astrophysics. They were just doing mathematics, like they always do, following their curiosity. But five days after they posted one of their results on a preprint server, they got an email that said 'Congratulations! You've proven Sun Hong Rhie's astrophysics conjecture on gravitational lensing!'... Turns out that when gravity causes light rays to bend, it can make one star look like many. But until Khavinson and Nuemann's work, astrophysicists weren't sure just how many. Their proof in mathematics settled the question."*
## Suprise! (Score:5, Funny)

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## Re:Suprise! (Score:5, Interesting)

beany experimental evidence of it. Right now it's nothing but a mathematical curiosity, but there is no way of telling, from today's perspective based on today's knowledge, what may come of this mathematical curiosity in the future. I'm not a supporter of String Theory (not that my support would matter anyway, since my knowledge of physics is everything from highschool plus whatever I'm curious about at the time), but more research is required before we can dismiss it outright.## Re: (Score:2)

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but more research is required before we can dismiss it outright.

More research than needed into Christianity, Islam or Buddhism? Why, because it has those complicated-looking mathematical equations that require physics beyond high school level to comprehend? It's amazing how much scientists, especially astrophysicists neglect the same scientific method that they ridicule the general population for ignoring. We don't really know what happens inside black holes or if they actually exist as described in textbooks. We can scarcely comprehend the conditions that exists in th

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1) It's already had about 40 years, and

2) It's very fundamental basis is problematic when considering it for force unification. You see, it's based on particle physics which is frame dependant, where as GR is frame independent. There are other *far* more likely theories, e.g. quantum loop gravity, that are frame independent as well.

So, even if there is even just a hint of reality to string "theory", it'll prove *very* problematic in the long run for other very *very* necessar

## Re:Suprise! (Score:5, Insightful)

What String Theorists have been doing is building descriptive models of actual theories. It's a valuable exercise, but they shouldn't feel that String Theory is going to provide anything other than another modeling and analysis tool. Specifically, because String Theory is so expressive, it is impossible to make a falsifiable assertion in pure String Theory. You always need an outside theory, and it's the outside theory that provides the falsifiable assertion.

String Theory can describe just about any system, so it's impossible to prove right, and more importantly for this discussion, impossible to prove wrong. Which means that it is not science. Knowledge of this reality is gradually percolating through the physics establishment. Give it time.

## Why bother, though (Score:2)

Having one set of equations to rule them all, one set to find them, one set to bring them all and in the darkness bind them... erm... wrong movie

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Also, String "theory" doesn't have something very *very* important in it. Or at least by its nature it isn't in it. That being a "big bang". Quantum Loop Gravity has one of those in it *by the very nature of Quantum Loop Gravity*.

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Knowledge of this reality is gradually percolating through the physics establishment. Give it

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'String Conjecture'and then we'll all be happyI'll raise you one String Conjecture to your Electric Univarse [sic] :P

## There's a problem. (Score:1, Insightful)

But many of its professional adherents (ie, actual, paid-to-be-Cosmologists Cosmologists) would feel a tad miffed. They often get quite grumpy when the "conjecture" word is waved in front of them. And yet some of them are perfectly okay with it all, because they know as well as anybody that String Conjecture is just a bunch of really fascinating What Iffing.

The big problem i

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predictions. It's one thing for a theory to be unsupported by observation, it's entirely another thing for it to be untestable.## Re: (Score:1)

Hopefully more and more people will finally realize this. It truly irritates me when someone who has no rigorous training in physics comes up to me and rants on about how all this crazy stuff is possible just because they saw a show about it on the discovery channel or read an article in popular mechanics. things like needing to prove the assertion there are more than 3 spacial dimensions completely pass them by and they jump to the end conclusion.

it is nice that the crazy assertions do inspire a curiosity

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String theory makes predictions that can be tested - just not at energies that are within easy reach.

Just because this reminds me of it - I had a science teacher that explained it well with the 'faerie theory of gravity' - his pet theory that things were held to the earth by tiny faeries that grabbed on and flitted their wings.

Then he forced us to quit laughing and prove him wrong, based on the predictions of the faerie theor

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String theory makes predictions that can be tested - just not at energies that are within easy reach.

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Every one of those so called predictions not only cannot be currently tested, but those experiments that cannot be run also don't have the falsifiability requirement in them. And I've only hear of ONE so called experiment. And I've been paying attention to this nonsense from a while now. So, I'm calling bullshit on this statement.

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making predictions and testing them

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And String "theory" has done

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Oh - that's right, I did.

You are correct, in that string theory predictions are not falsifiable *at our current level of technology* - the predictions they make are at higher energies than currently feasible. But it *does* make predictions, and frankly, if you are sitting here claiming it doesn't, and then claiming you've followed this for years, I have

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I mean Einstein & Born get all the credit but most of the time great physicists are just applying the maths of great mathematicians 50+ years before them

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The relationship between maths and physics (all of science really) goes both way. If you read the article, you'll see that the original astrophysics conjectures provided an instance of maximal solution that the mathematicians hadn't found.

If you read the history of general relativity, you'll find that Einstein did a lot of significant work with David Hilbert, the leading mat

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Dance: The Elegant Universe [worldsciencefestival.com]

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Thus mathematics = sex.

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## animation depicting gravitational lensing (Score:5, Informative)

## To update Clarke (Score:2, Funny)

## Perhaps I am missing something... (Score:2)

I think it relates to the mass creating the lens but since the mass is not an integer I don't see how the math could work.

Does anyone have a link or maybe an explanation?

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4images of a quasar in the article. Not only that, somebody links to the Wikipedia article on gravitational lensing, and that shows a picture of an "Einstein Cross:" four images of a quasar surrounding a galaxy between it and us. Four,## Re: (Score:3, Informative)

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## Re:Perhaps I am missing something... (Score:4, Informative)

4images of a quasar in the article. Not only that, somebody links to the Wikipedia article on gravitational lensing, and that shows a picture of an "Einstein Cross:" four images of a quasar surrounding a galaxy between it and us. Four, in both cases, not five. Yes, I realize that in both cases n = 1, but can anybody explain how you end up with four in that case?maximumnumber of images that can be seen. It doesn't mean that in general you will always see the full 5n-5, only that in some cases it is possible to see that many.So the number you see doesn't have to be a multiple of 5 always, even for n>1.

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There's no guarantee that you can see the 'straight through' image, because the object doing the lensing might be in the way.

And for n objects lensing, the effect is multiplicative.

What's so difficult about that?

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4 images from gravitational lensing, plus 1 image not distorted (straight through the lens) equals, in my book, 5.Thank you! Yes, of course, there would be an image in the center because light coming straight at us won't be displaced. I'd never thought of that. Of course, that image will be blocked by whatever's causing the lensing, but it's going to exist. And, I'd guess, with more than one object, there will me one or more images similarly blocked.

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If they were side by side, then the maximum would be 2n?

## Cross-Disciplines! (Score:1, Interesting)

And isn't that wonderful, that our sciences are so wide in breadth that one discipline may hold answers to other disciplines' questions?

And much much better is that someone in another discipline is willing to look across those divisions to see an answer that might have gone unremarked.

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## Can one of you mathematicians explain (Score:2)

TFA says 5n-5, but I don't get it because if n=1, then zero stars would be seen.

Can someone clear this up?

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I'm supposed to see a maximum of 5 stars through gravitational lensing, if there were two original light sources?

Something doesn't make sense here - why should there be discrete output from lensing? I would think it would be possible to output an elongated blob of light from a point light source.

Maybe this will need an astrophysicist to explain it.

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## Re:Can one of you mathematicians explain (Score:5, Informative)

Galaxies, on the other hand, are not point sources, which is why when we see gravitationally lensed galaxies they often look stretched out along arcs -- different points in the galaxy line up differently, and thus can look farther apart from each other than they would if we were seeing them without lensing.

## Further proof ... (Score:4, Funny)

## Re:Further proof ... (Score:5, Interesting)

I think the role of math as "leading" is oversold. I get the impression that a heck of a lot of math was inspired by physics. It seems as though the two develop in tandem. In particular, vector calc and E&M come to mind.

It can also be argued that philosophy is more basic than math. Some might say that we need our ontologies and epistemologies before we can do calculations involving them.

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Though it is a strange feeling to think that someone is able to share their knowledge of a subject even though they are no longer here in person; with a modern textbook the aut

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Generally things like propositional logic and the axioms of mathematics are held to be self-evident physically. However, some things were thought to be mathematically self evident until physicists p

## Re:Further proof ... (Score:5, Insightful)

I really want to agree with you, but people keep finding ways that obscure, useless little pieces of purely abstract math suddenly explain something interesting about the real world. Sometimes it takes a century or two, sure. But, if you told the first people to work on imaginary numbers how useful their math would be for expressing many engineering things, and how it would be a major tool for engineering students learning to build very real things, well they'd just call you a moron. Likewise, boolean algebra, or any number of other mathematical concepts that make our current world possible and relatively comprehensible.

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necessaryto describe something physical.## Mathematics can't do experiment (Score:1)

Matematics allow you to create an infinity of different topology. I'm sure that one of them will be able to represent the universe.

But The Mathematicien will never be able to say which one is the correct one. For them they are all the same, methematical models.

For the physician which have his experiments and data, only one is the correct one. The rest is just models.

Mathematics is not a science.

## Re:Further proof ... (Score:5, Informative)

The development of non-Euclidean Geometry argues against your point, rather than supporting it.

Non-Euclidean geometry arose out of pure mathematical attempts to correct a "flaw" in Euclidean geometry. Namely, that the parallel postulate was so big and complex that it didn't seem like a proper axiom, not like Euclid's other four axioms.

Lots of mathematicians had tried various ways to prove that the parallel postulate wasn't necessary, that it could be derived from the other four, and many flawed "proofs" were constructed. A few mathematicians, notably Saccheri, decided to take a less constructive route and try to disprove the necessity of the parallel postulate by contradiction.

The idea was: Replace the parallel postulate with something else that means the opposite, and then show that geometry breaks down, that logical contradictions can be shown. Saccheri thought he succeeded because he was able to prove some things that made no sense within the Euclidean framework.

Later mathematicians realized that, in fact, Saccheri had "failed" to find a contradictions, that his results resulted in a geometry that was weird and non-Euclidean, but perfectly consistent, and in fact made perfect sense if you applied it in the context of a hyperbolic surface. Under a different modification of the parallel postulate, you get a geometry that makes perfect sense on the surface of a sphere.

Later still, physicists picked up on these alternative geometries and began applying them to great benefit. Notably, Einstein's notion of spacetime as non-Euclidean.

It goes both ways, of course. Physics often motivates math, and pure math is often adopted and applied by physics. Neither would be as rich without the independent work of the other.

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In fact in this case, Rhie found the limit first but just couldn't prove it.

As for proving stuff, Math can help prove some stuff, but not other stuff (it can't normally be used to prove what you had for lunch yesterday).

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There is a reason why that is, math and physics are part of the the same discipline, whether anyone else has realized it or not one only has to look to geometry to see how they cannot be dis-united. The real physical world is full of geometry (i.e. physics) and you need an abstract representational system to describe that geometry (math

## Re:Further proof ... (Score:5, Interesting)

Firstly I don't think there are any absolutes, sometimes math and physics develop in tandem and other times there's a lag time with one or the other leading. I personally think math "leads" the way. Not because it wants to describe the physical world but because it's interesting. Just remember that the math you learn in high school is hundreds of years old, you don't get to the current stuff until grad school. Whereas a physicist uses math as his tool to achieve his goal and will only invent a new tool if his toolbox is insufficient, a mathematician creates new tools just because he wants to understand them. In other words the goal of a mathematician is to make to tools, the goal of a physicist is to apply the tools. That's personally why I think math is "leading" most of the time. I'd rather not get into naming specifics examples as there are millions and I don't believe anyone could win that argument.

As far as math being a subset of philosophy I'll have to disagree; I think they are inexorably linked but neither proper subsets. They share the same grammar, logic, but differ in their dictionaries.

Those are just my thoughts on the matter though.

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Physics is the subject matter.

So yeah, they change together. Different from the normal relationship between language and subject, you've got plenty of math without a known application in the real world, but as long as you're using the same axioms, it all seems to eventually make sense...

## Re:Further proof ... (Score:5, Insightful)

Some might, but I wouldn't.

Mathematics has its own ontology - namely the axioms that it is based upon.

It has no need for a separate epistemology - it is what it is, and that's that.

Propositional calculus, on which Russell, Frege and Wittgenstein based their mathematical philosophy (which I see as applicable to all rational thought) is itself the root of mathematics - thus mathematics (or logic, however you wish to phrase it) is fundamental to philosophy, rather than philosophy being fundamental to mathematics.

You can't have an ontology without maths - epistemologies are more equal, but essentialy the whole of philosophy is based on the propositional calculus, which is only one of many possible formulations of mathematics.

## Too Narrow view of philosophy (Score:2)

Get out more. Read some Kierkergaard and Tao Te Ching. Check out existentialism, phenonemology, and sunyata in buddhism....

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Philosophy -> Physiology -> Biology -> Chemistry -> Physics -> Math -> Philosophy ->

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think the role of math as "leading" is oversold. I get the impression that a heck of a lot of math was inspired by physics. It seems as though the two develop in tandem. In particular, vector calc and E&M come to mind.Many fields of mathematics were created simply to solve the real-world physics problems of the time. Attempts to predict tide levels in the 1800's led to the development of mechanical calculators and signal processing (sum of weighted sine waves).

A Renaissance parlor trick of placing salt

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## Curiousity Killed the Cat (Score:2)

Some of these theories offer (often long standing as I understand) a financial reward for the person(s) who proved them. I did some looking and I'm not seeing any for this one in particular. My questions (yeah, I ask those a lot here) total just two today. Was there one in this case? If there was then, well, who would get it?

## Am I the only one (Score:2, Funny)

who thought that this was about Penzias and Wilson?

I mean, C'mon.

I'm thuper thereal, guys!

## "totally extraterrestrial" (Score:2)

"I find the whole experience totally extraterrestrial", wins the Internet.