165 posts • joined Thursday 9th August 2007 10:42 GMT
Re: Oh yes, power cuts in the '70s
These days I might just hope that at least if the power was to cut out, that it was on a cloudless night, so that for a change I might see the stars properly.
Re: CS graduates are choosing unemployment over becoming teachers?
Remember, they'd have to retrain as teachers - so its not a trivial job switch, and they may well reckon they'll get a more standard CS job before finishing (and paying for) teacher training.
Re: a bit fast to be called flapping.
What do hummingbirds do with /their/ wings then?
I think the "flapping" debate might just as well be applied to slower flying jellyfish; it's more about the action than the speed.
on the subject of an icy north (or not)
... this is an interesting semi-technical read:
Re: It may be a dumb question but ...
I've just skimmed the paper. Although its not my field at all, they have thought about alternatives.
E.g. this quote: "We consider this scenario unlikely as it would require a common recent coalescence of these ancestral wolf and dog sequences from geographically disparate areas. Nevertheless, ..."
But there are plenty of caveats scattered through the paper -- as with lots of this sort of science, their eurodog hypothesis is the most reasonable conclusion >>given the available evidence<<.
Re: cash to waste
Other reporting has pointed out that India's social aid budget vastly dwarfs the money spent on this Mars shot, and that India's poor would benefit more from more effective (and less wasteful) use of their existing budget rather than adding by some tiny fraction to it by cutting sci/tech funding.
 Either or both the Indy or Gruniad articles I read over the weekend, for example.
Re: the worst way of disseminating information.
maybe I didn't look around the site enough, but why is it you think that's how they're proposing the courses are run?
Instead, I would assume some set reading and exercises to set up the lectures; as in e.g. http://arxiv.org/abs/1309.0852
Re: nothing contradictory about both those propositions being true at once
As I understand it (Seth Lloyd's paper), to determine whether or not you have free will or not you need a third proposition:
3. It is physically possible that another (not-you) entity or system could have a model of you that reliably predicts your actions /before/ you so act .
If this (3) is true, then you fail Seth Lloyd's "free-will" test; if false, you pass, and might have free will after all.
 Note: A prediction generated using prior information, but without looking at the outcome, but which is calculated after you act, does not satisfy (3)
Re: "Free will" is rather poorly defined.
Physical models explicitly disallow free will. The most free-will-like thing they can do is add in some statistical uncertainty to either the initial conditions or the dynamics; and then consider this uncertainty to be a proxy for whatever free-will might be. Note that chaos cannot help here, since it is still strictly deterministic, although it can be a handy way of making things more complicated when constructing a pseudo free-will fr your models.
How do you build a mathematical (or physical) predictive model of something with free-will? The notion of a predictive model of free-will is an oxymoron. If I've got a good model, the decisions no longer look free, they are just consequences of the state of the system. Hence, there are (can be) no predictive models of free-will.
Hence the article's focus on "practical unpredictability" -- i.e. "we cannot in-principle predict in advance" -- as a way of assessing the likelihood of free-will being present. It's about as close as we can (currently) get to understanding free-will.
Re: confused, moi?
I once read some Bertrand Russell, and had to read each sentence twice in order to understand it and its in-context meaning. Some time you just have to keep banging the (mental) rocks together and hope it eventually becomes clear.
But if you'd prefer a more IT angle, why not try this instead?
"When does a physical system compute?"
Re: try your body clock
This sort of thing mostly works for me, although I wake seconds earlier, not minutes. If not, then the light from my trusty old Zaurus's screen (as it wakes) wakes me, and if not that, then it's really rather pleasant alarm chirp.
The most exciting radio alarm event I've had was when Mark F decided to play Ministry's "Jesus built my Hotrod" on 4ZZZ at 6:55 one morning, just in time for my usual wakeup. Thanks, Mark!
Re: Who uses bing?
Now that a large proportion (maybe even most) searching is done online, we no longer need a special word to denote online searching. Thus we can use that one we all used to use before we got all excited about computery stuff. You need only say -
"Just search for it"
Re: "wholly out of light"
The only way you get light to not travel at lightspeed is to make it interact with something. E.g. in water, visible light interacts with the water molecules, and it slows by about 30% (hence the refractive index of 1.5). To make light really slow, you have to get it to interact very strongly - in this case, using a specific frequency of light tuned to specific transitions in carefully managed rubidium atoms.
This "slow light" therefore, is a rather misleading name - it isn't just light - it's a strongly coupled light-matter system, which some would prefer to call a polariton.
I can therefore only assume the down votes were for the poor quality joke.
Re: Got a [...] Sharp Zaurus SL-5500
... I not only still have my Zaurus, I still use it :-) ... albeit mainly as an alarm clock and a place to take notes at conferences.
Re: The subheading is also erroneous
In my experience, the embargo is really just a handy way of maximizing press impact, rather than some kind of evil plot. I'm not sure there's any likelihood a journal would refuse to publish a "press-worthy" paper just because the authors didn't want to respect an embargo - it'd still be a good paper, and still publishable.
Remember that this is science news, and is not really all that time sensitive, nor does it matter which day you hear about it. You still get the news (and so not unfair to taxpayers, who aren't denied anything important), just when the science journalists have had a week or so to talk to the authors and get a proper write up done.
Further, in practical terms, the sanctions for breaking an embargo are most likely as weak as "we wont give you pre-notice again" ... which hardly stops any journalist from reporting on the other 99.99% (or whatever) of science that there is out there. Just (eg) subscribe to some journal (ore arXiv) RSS feeds if you want non-embargoed science.
Re: [phone] modem-like add-on
... hmm, my decade-old Zaurus PDA had a CF phone add-on thingy advertised at one point, if I recall correctly (although I never got - or wanted - one at the time). Might not even have been Z specific, I suppose.
Re: Shurely shome mishtake?
Er, nope. You can split photons (although perhaps its better to call it conversion) using an optical nonlinearity, as long as you conserve energy. And since the "colour" of a photon depends on its energy (frequency), splitting a high frequency "blue" photon will (can) give you two "red" ones. And with a different setup you can produce photon pairs with mismatched colours.
Re: New Scientist
I agree the general state of New Scientist is depressing. While I stand by my belief that BBC reporting should remain at a very broadly accessible level, NS is exactly the kind of publication which should pitch to a higher level - indeed, I thought that would have been the entire point of a magazine with that name. That said, when some of my work was reported in NS, I was perfectly happy with the result.
I also distinguish between "(news) reporting", which need not (and imo perhaps should not) be technical at all, especially in the mass media, since the point of news reporting is primarily to make the audience aware of something. This is distinct to features or documentaries, which people usually choose to watch, and where greater expectations of their knowledge are entirely appropriate.
As for "an essential part of the [scientist] job description is to ensure that society gets dragged along with one. The two aspects of the job are hand in glove", I would like to agree. But media & outreach interaction can be a vast time sink, and while I do not begrudge it, it can and does affect research output; and, further, not all scientists are very suited to it, and in many cases, neither is their research topic. By all means call for a larger cohort of science communicators, which is indeed the current trend, but expecting all scientists to turn into some sort of media/outreach enthusiast is neither practical, nor a good use of their time and resources.
ICE Cube - moon shadow
Re: Ottman001's generalised perception
> My generalised perception of younger generations is that they are less likely to look something
> up unless it is some fickle celebrity nonsense.
On the face of it, this is a plausible claim. But my understanding of school education these days is that is (at least) intended to promote more self directed learning. Whatever its failings, why would this make "younger generations" less likely to look non-celeb stuff up? So, can anyone provide evidence that it is actually true?
Re: written by someone who clearly has no idea about science or technology
In my experience as a physicist, who occasionally has got media interest, science journalists are well motivated and do the best they can at converting quite difficult things down into a form digestible to their (target) mass market. As for "there is no excuse for general publications to assume all of their readers have no knowledge at all", well, the great majority of their audience probably does have no useful knowledge at all (i.e. on the specific subject being presented). Why should the majority be excluded from mass market reporting? You knowledgeable types can just feel all smug at your extreme cleverness - and know enough to go and find a more specialist publication. Just treat the mass media reporting as a supply of adverts, or trailers, for the real sci/tech story.
Re: We are in a state of such confusion we will definitely learn something"
Such as: "Actually, we have learned that we are even more confused than previously thought!" :-)
Re: Very Large Phones
hmm ... if you think about it, these Personal Digital devices Assist us in so many ways - phone calls, notes, media , apps, and so on. Maybe we could call them by some sort of related acronym ... e.g. PDA?
Just a random thought. :-)
Re: the problem of how to catalogue, ...
So if big data isn't "big" then "big data" is a pretty silly name for it. Since supposedly the phrase is used to indicate a soup of factoids elements with had to discern structure, we need a better name. Random stuff assembled together in a way posing as something interesting? Hmm... the art world may have got there first ... how about we just call it "dada" (singular "dadum") instead?
Re: Seems rather cruel
Not really. They're just testing the waters to see if they might be able to sell these dolphins phone contracts and subscriptions to fins reunited.
Actually, why not test if dolphins really could get the hang of telephones? It'd be interesting if they could!
Re: First seen here in the 1940s
... indeed, quite a sucessful way of generating scientific output is to trawl through old journals, and re-attempt what failed back then, but with today's technology. (not saying that's what happened here, mind you).
Re: Anyone working on these models like to comment?
Any professional climate scientist would need a thick skin to even contemplate posting commentary here. Climate debate in forums such as this is a pretty ugly process, and, in fact, tends to have very little to do with any of the formal scientific output - it's largely based around rehashed (& sometimes misread) press releases, superfically relevant technical issues, and/or poorly-founded assumptions about conspiracies, groupthink, or special-interests (on any side of the argument).
This thread is a brilliant example of an internet forum "climate debate". But not so much a brilliant example of any science. Really, what would some putative "regtard" climate scientist have to offer this thread? And what would it offer them? Would it really be worth it? Do you really think you could convince them it would be worthwhile? No, really?
Re: Art? ART?
Or these, maybe (not as good as Jansen, but they have a certain something)
Re: useful presents, eh?
Costly but worthless gifts facilitate courtship
Proceedings of the Royal Society B: Biological Sciences, Vol. 272, No. 1575, p1877-1884 (2005)
by Peter D. Sozou, Robert M. Seymour
What are the characteristics of a good courtship gift? We address this question by modelling courtship as a sequential game. This is structured as follows: the male offers a gift to a female; after observing the gift, the female decides whether or not to accept it; she then chooses whether or not to mate with the male. In one version of the game, based on human courtship, the female is uncertain about whether the male intends to stay or desert after mating. In a second version, there is no paternal care but the female is uncertain about the male's quality. The two versions of the game are shown to be mathematically equivalent.
We find robust equilibrium solutions in which mating is predominantly facilitated by an ‘extravagant’ gift which is costly to the male but intrinsically worthless to the female.
By being costly to the male, the gift acts as a credible signal of his intentions or quality. At the same time, its lack of intrinsic value to the female serves to deter a ‘gold-digger’, who has no intention of mating with the male, from accepting the gift. In this way, an economically inefficient gift enables mutually suitable partners to be matched.
Re: may, might, could
Further to the "unscientific" claim regarding the use of these words, I did a quick search on the APS website for journal papers containing all three words: there were 112k hits. As a quick check against mismatches, notably regarding "May" as e.g. a date or part of a name rather than a Word, I checked 10 of those (with a slight bias towards those with May in the dates), and found only 1 without May as a word.
This would suggest either that that the APS (see http://publish.aps.org/) has published many tens of thousands of unscientific articles, or that instead, contrary to your assertion, that "may", "might", "could" indeed do have a perfectly normal place in the scientific literature.
Re: not how I was trained to express scientific results
In fact, scientific papers often contain words like "may', 'might', 'could', etc Notably in the abstract, introduction or conclusion, when trying to explain the motivation of the study, or to communicate why they think the results are or might be important. Typically the phrases using these words are rather distinct from the specific scientific conclusions reached or methodology used.
However, (media or commentator) reporting of the results tends to focus on those more exciting "may', 'might', & 'could' parts, especially since the technical details are usually way beyond the educational level of their readership.
Re: a lab toy with zero practical use.
Common practical uses for lab toys with "zero practical use" are as a demonstrations, proof-of-concept, or as educational equipment. I think this can function as all three.
Re: Silly question, but...
It's an illusion - it (the event) hasn't gone anywhere, it just doesn't get seen.
Re: the work [...] follows on from a 2010 experiment
I think you meant to say: follows on from the concept as proposed by McCall et al in J. Optics (2010/11), followed up by an experiment at Cornell (published in Nature 2012).
And re "but when it comes to security the ability to drop one's data into a time hole isn't quite as useful as it sounds cool" -- what, sounding cool isn't a useful thing? I mean, it got you to report on it, didn't it? :-)
Re: Does superluminal signalling automatically imply time travel?
To clarify - the "hidden variables" superluminal signalling is only partial; you can only extract information once you get the other part - but unfortunately that has to be sent in the ordinary way - i.e. by lightspeed limited means.
Re: I never totally understood why X couldn't be explained by simple hidden variables
They can - if you also permit superluminal signalling. However, most physicist prefer to live with "spooky action" than with a violation of relativistic causality.
why does the world stick to a few wavelengths for communications?
Because the low-loss wavelength ranges in silica, the primary material used in optical fibres, are at about 1330 and 1550 nm. The amplifiers are designed largely to match these.
Re: Smart buildings
Wires are old hat. Better to use optical fibres, since frequently they can also act as both the sensor and transmission medium, and are largely immune to most sources of electrical and magnetic interference (although properly designed, they can act as E or M sensors as well). And if you use them to make an interferometer, they can also be fantastically sensitive.
Re: The Shard
Nah. Use green lighting, a few baubles, and stick a fairy on top. It's a giant Shardmas tree,
Re: It's impossible to send data this way ...
Its impossible to send information FASTER THAN LIGHT, because in order to know whether your measurement ("here") is an encoded 1 or 0, you need to compare it against the other distant measurement ("there"). E.g. if they both are the same, it's "1", if they differ, its "0". So to understand your result, you have to wait for the results from over there to be sent to you here, and that waiting time depends on the speed of light.
Re: "it's so strong that there's no give or elasticity in it"
No, it isn't that strong.
More specifically, the atoms/molecules in the wire are held together with electromagnetic fields, whose (maximum) speed is that of light. Therefore, the effect of your pull can also only be transmitted at the same speed; the wire therefore can never have "no give" and be as strong as you would like..
And as long as you insist that your wire is made of stuff subject to a relativistic universe and its maximum speed, that same holds.
Re: You cannot make the test you mention
I didn't mention any specific test, therefore there is no way you can claim it cannot be made :-)
But to help clarify, by "test", I meant examine the experimental consequences of both interpretations; and which the authors (claim to) have done for this one setup.
Just because the predictions of HV (of interpretations (a)) produce the same results as those of (b) is beside the point here - they have different consequences for how we think and motivate or justify results. Results of the type in this reported experiment have serious consequences for those who prefer HV whilst sidelining the issue of speed-of-light causality.
Neither (a) nor (b) allows a traditional physical intuition relying on both standard probability /and/ speed-of-light causality to survive. I think (b) proponents have come to terms with the weird nature of quantum probability. This experiment forces the (a) proponents to do the same regarding causality.
Re: you don't understand quantum mechanics.
Hmm. If this forum were full of physicists working in the relevant subfields of quantum mechanics or quantum information, then you might well be able to prove something. But not necessarily the "don't understand quantum mechanics" part.
Some context ...
You can interpret QM predictions of separated measurements on entangle systems like this in two ways:
(a) You insist that any quantum uncertainty might be a result of ``hidden variables'', and so follow the rules of classical (ordinary) probability. This requires the two parts of the experiment to be able to signal to each other instantaneously: i.e. the so-called ``spooky action at a distance''
(b) You prefer to retain the speed-of-light speed limit for cause and effect, but at the cost of disallowing hidden variable (standard probabilistic) models, and thus need to describe things using complex probability amplitudes - i.e. quantum probability.
Most physicists prefer to choose (b), because they prefer to retain causality over a model respecting classical probability theory.
Nevertheless, it is valuable to test both ideas. As I understand it, here the authors' have said: if we choose a hidden variable interpretation (choice (a)), what is the experimental bound on the speed of information transfer?
This doesn't mean that the interpretation (a) is the ``true'' interpretation. It doesn't even mean that the authors necessarily prefer (a) over (b). But it does tell us something about how things (might) work /if/ (a) were the best interpretation.
Re: Light travels at the speed of light, full stop
"speed of light" might mean one of two different things, depending on context. Either the fundamental speed limit as determined by relativity, which is the same as the speed of light in a classical vacuum. Alternatively, it might mean the spped that light gets from one end to the other of this stuff I have here (which will be less than the other definition).
Here, the context given, i.e. "99.7% of the speed of light" strongly suggests that the first "relativistic speed limit" definition is the one meant.
Lastly, most materials and waveguides have (both) temporal and spatial dispersion - their wave speeds vary with frequency (wavelength). This variation gives rise to a "group velocity", which is the speed a pulse will travel through, and this need not be especially similar to the (usually quoted) phase velocity. Generally, high-frequency (short wavelength) signals feel the medium/waveguide less; this has to be true in the very high frequency limit or something has gone wrong with causality. This high frequency behaviour means that you can get optical precursors that travel at near (vacuum) c even in a material, even if you send in an otherwise unremarkable pulse into a "slow" medium.
The author's original paper states: "This novel radio technique allows the implementation of, in principle, an inﬁnite number of channels in a given, ﬁxed bandwidth, even without using polarization, multiport
or dense coding techniques."
Note the "in principle", this is a pretty strong qualifier, essentially meaning (in this context), "ignoring all practical constraints, and only considering (this) simple theoretical model".
The big constraint here is alignment - the antennae need to be aligned, because you wont be able to get good enough OAM information from the edge of the beam, especially if its centre is off the receiving antennae. So mobile might be ok, but only if lined up carefully .... not if you are wandering down the street! This is more of a prepared fixed-point to fixed-point scheme.
No - there are two circular polarization states; but this is not the same thing as the (orbital) angular momentum of a light beam. You can have a "plane wave" in LH or RH circular polarization states without any spatial structure, but for OAM you need it. E.g. try looking up "optical vortex" on wikipedia.
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