Catch up on stories from the past week (and beyond) at the Slashdot story archive


Forgot your password?
DEAL: For $25 - Add A Second Phone Number To Your Smartphone for life! Use promo code SLASHDOT25. Also, Slashdot's Facebook page has a chat bot now. Message it for stories and more. Check out the new SourceForge HTML5 Internet speed test! ×

Comment Re:Found at 125 GeV (Score 4, Insightful) 396

Beware that there are 2 kinds of mass: (1) inertial mass and (2) gravitational mass. In principle, the Higgs particle helps explain the inertial mass, that is, the resistance of an object to a change in motion. Hence the (in my opinion somewhat poor) analogies of the Higgs field to a snow field or a bowl of syrup, where some particles are sticking into more deeply than others. It's only because of the equivalence principle that inertial and the gravitational mass are indeed "equivalent" (and quantitatively the same), which, if you think about it for long enough (or "too long" if you one of those people who think that all research should only be done for some practical purpose), is actually surprising.

Comment parachuting to McMurdo (Score -1, Offtopic) 96

If you are a good linux sysadmin, you have a physics degree or related, you are in good physical health (including good teeth), you are neither claustrophobic nor agoraphobic nor nyctophobic nor frigophobic, you are a stable person with good communication skills and you are in for an adventure: apply for the position of IceCube winterover. You'll pass through McMurdo several times, possibly staying there for a few days depending on weather conditions. Parachuting is usually not part fo the deal, but who knows. They also run marathons there on the ice. Deadline for application is March 30, so if you like this idea you need to act fast.

Comment Significance (Score 4, Informative) 113

Being a physicist myself I am very happy that this topic makes it into the news. But it is important to keep cool and skeptical. The statement that a statistical fluke has a probability of 0.05% implies that it is bound to happen if you let 2000 students do data analyses on independent data sets. There are indeed literally thousands of PhD students doing such analyses LHC data, trying to address hundreds of specific research questions that each require different data selections. So it is very likely that some of them will find a result several standard deviations away from the expectation. Actually 3.5 sigma deviations happen very often, because of all sorts of mistakes and inaccuracies in the analyses, but most of the time these mistakes are scrutinzed away before loud public announcements are made. After all scrutiny a few genuine statistical flukes should still remain, and recognized as such.

(For the xkcd inclined: green jellybeans linked to acne.)

More caveats:

  • On slide 14 and 15 you see a summary of the estimated systematic errors and the final result: the deviation of the observed value from the expected value is 0.82 ± 0.21(stat.) ± 0.11(sys.) %. Estimating and combining systematic errors is almost by definition dark magic. It looks like the "3.5 sigma" was obtained by adding the statistical and systematic error in quadrature, which yields a total error of 0.237, and 0.82/0.237=3.5.
  • The statement that the probability of this 3.5 sigma deviation is 0.05% is based on the assumption that if you repeat this analysis several times on more data with exactly the same experimental setup, the deviations from expectation are distributed like a Gaussian (bell curve) with a sigma equal to the total error mentioned in the previous bullet point. That is a major idealization, it could be distributed in many other ways, and then the relation between the deviation (in units of sigma, which is also defined for non-Gaussian distributions) and "the fraction of events with such a deviations or larger" can be quite different. Furthermore, when repeating the identical experiment the systematical errors do *not* fluctuate (that is one of the aspects in which they differ from statistical errors), so aforementioned idealized Gaussian would have an arbitrary offset with a magnitude of the order of the estimated systematic error (0.11), in either direction, and a width of the actual statistical error, 0.21. Depending on what this systematic error really is, the true statistical significance is much larger or much smaller than the quoted 3.5 sigma.

So this is a very interesting result, but more study is needed and in my experience such flukes almost always evaporate in the light of more data and scrutiny. Still, it's not completely excluded that this was indeed the first hint of a real discovery (otherwise no researcher would ever do all that work).

OK, enough for now. Sorry for misinterpretations and other errors I might have made.

Comment Number of replies (Score 2) 2254

Previously, for every story on the front page the total number of replies was listed. I thought that was a nice popularity indicator and I used it when deciding if I would read a story or not. In the new design it only says "Read the comments". I did not find a setting in the "Options" that would re-enable this feature. If I overlooked it, please enlgihten me, if it's just not there then please add it...

Comment Re:So it's possible after all... (Score 1) 98

Actually practically all IceCube servers at the Pole, running the data acquisistion, processing & filtering are running linux. So those penguins would not have much to do, except join the party. :-)

(And a nitpick: IceCube is actually at the geographic South Pole, too far away from the Antarctic coast for any penguin to reach it.)

Comment Re:Interesting... (Score 2, Informative) 165

I agree that the background reduction due to lack of atmosphere is very convenient, but as zero.kalvin points out, you still need a 'refracting medium', that is, a really large volume of transparent material such as water or ice (in which you can catch the Cherenkov light whenever a neutrino is kind enough to interact and produce fast charged particles). The large volume is not needed to suppress background, but to beat the very small cross section; in order to detect neutrinos you need them to interact with your detector, and the only way to achieve that is to make it as big as possible.

There is ice on the Moon, but to harvest that and turn into a detector poses some interesting challenges. To use it in frozen form is hard, because you need it with a clarity and purity similar to the exceptionally clear deep Antarctic ice that IceCube uses and which is even clearer and purer than laboratory ice. To use it in liquid form requires keeping it heated, which is probably easier (you need a solar panel farm to power the heating system, but for the ice option you would also need those panels, to power the elaborate purification system + clear ice machinery). Either way: probably science fiction.

Comment Re:Go the "Green Spin" (Score 1) 276

Another "green" issue is that while a puffin may consume less power than a propellor plane powered by a combustion engine, flight is still less energy-efficient than transport by wheels (train, car, bike). As far as I know currently only a tiny fraction of electric power worldwide is generated with environmentally friendly techniques. So I'd like to see the kWh scores compared between a puffin and an electric car.

Comment 100 per cent objective (Score 1) 1174

I am surprised by how serious people take this light-hearted article. It clearly states:

So, let's take a 100 per cent objective* look at the plugs and plug sockets of the world,...

where the footnote clarifies: "*Objectivity in this sentence has a one-off, government-approved change in definition. Its meaning here, and only here, is the exact opposite of what it usually means." Do /. readers really recognize a tongue-in-cheek story only when the summary got the humor icon stuck on it?

Comment in combination with a wearable display (Score 1) 166

When you have toy like this or somesuch, then you do not need a regular screen. A screenless laptop plus wearable display seems to me a nice solution for mobile computing. Of course the laptop should have a battery life of 8h then. Which should actually be easy, because I would expect those display goggles to use less power than a regular screen.

As a side note: for tall people like me this would be kind of ideal for computing in an airplane. Unless I'm in an exit row or bulk head seat there is no way I can see my regular laptop screen. With display goggles that problem is completely solved.

Slashdot Top Deals

Promising costs nothing, it's the delivering that kills you.