Become a fan of Slashdot on Facebook


Forgot your password?

Slashdot videos: Now with more Slashdot!

  • View

  • Discuss

  • Share

We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).


Comment: Re:Worthless BBC article (Score 2) 105

by fishicist (#46013319) Attached to: Study Doubts Quantum Computer Speed
Skip the BBC article and go straight to the arXiv preprint.
Quote from the abstract:

Our results for one particular benchmark do not rule out the possibility of speedup for other classes of problems and illustrate that quantum speedup is elusive and can depend on the question posed.

The study asks a very specific question and acknowledge its limited scope.

Comment: Re:Preventive tech? (Score 1) 76

by fishicist (#45115017) Attached to: MIT Develops "Kinect of the Future"

Imaging through scattering media, for noble causes such as medical imaging, is a current and productive research area in optics. You can account for essentially arbitrary scattering as long as it doesn't change quickly. While the technology would be different, but I expect that the mathematics and the techniques already exist to thwart and such wall which you might design.

On the other hand, a 5mm sheet of aluminium ought to do the trick. :)

Comment: Re:Yes, but... (Score 1) 139

by fishicist (#44552957) Attached to: Royal Navy Deployed Laser Weapons During the Falklands War
Did aluminium really catch fire on HMS Sheffield? It seems to be well known that it did, but is it true? Aluminium Design and Construction by John Dwight, Section 1.1.7 refutes the assertion:

Three of the British warships sunk in the Falklands war ... had aluminium superstructures. At the time, the press stated that ... the aluminium had actually burnt. This was completely untrue. The aluminium structures lost strength and distorted, but did not burn. Aluminium sections, plate, sheet, foil and wire will not support combustion. Only in the form of very finely divided powder or flake can the metal be made to burn, as can finely divided steel.

Comment: Re:Transporters (Score 1) 383

by fishicist (#43993231) Attached to: Dmitry Itskov Wants To Help You Live Forever Via an Android Avatar
I'm not quite sure how Star Trek handled the concept, but in reality the No cloning theorem of quantum mechanics tells us that, while teleportation is possible, you can never have two copies at the same time. Teleportation, used in this sense, is implemented by transferring all the information necessary to make a perfect copy of the original state; no cloning theorem tells us that this must destroy the original. And perfect really does mean perfect; the copy will be indistinguishable from the original. Such indistinguishability is a crucial part of quantum mechanics; it leads, for example, to the Pauli exclusion principle.

NASA Planes Fly Over Bay Area To Measure Air Pollution Levels 57

Posted by samzenpus
from the air-up-there dept.
An anonymous reader writes "NASA is trying to measure the air pollution by flying a plane at various altitudes over the bay area. The tests are a part of a larger effort led by the DISCOVER-AQ campaign — a multi-year program launched across the United States in 2011 by NASA's Langley Research Center in Hampton, Virginia. DISCOVER-AQ stands for Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality. NASA's Langley Research Center in Hampton, Va., is the lead center for the mission."

Comment: Re:Let's not jump the gun. (Score 1) 250

by fishicist (#39676299) Attached to: Major Networks Suing To Stop Free Streaming
I suppose I mean that, from my perspective, I have all the functions that Aero would provide. If I so chose, this could include streaming to multiple users since several mythfrontend instances can talk simultaneously to the backend over a network. I do note the difference, however, in Aero being run by a company, not by the user.

Comment: Re:Eventually... (Score 1) 169

by fishicist (#39339425) Attached to: Single-Ion Clock 100 Times More Accurate Than Atomic Clock
Citation for the parent:

n.b. the work [1] by Müller, Chu et al is related, but different, and the interpretation is strongly contested (e.g. [2])

Comment: Re:How do you measure how accurate it is? (Score 2) 169

by fishicist (#39338595) Attached to: Single-Ion Clock 100 Times More Accurate Than Atomic Clock
1) You make two and see by how much they differ after a certain time. (Further reading, see Allan variance.)
2) As with all the base units, we must 'define' the second in terms of something physical, which we can measure, so that we can use this abstract idea in the real world. This real-world embodiment is imperfect, and it is an engineering challenge to make something which better approximates the idea. For illustration, consider the kilogram, which is defined by a lump of metal in Paris. In principle, chipping a bit off this block makes everything else weigh more in terms of kilograms, but we immediate recognise this as crazy and we can imagine a better physical embodiment of the ideal kilogram (indeed, efforts are under way to do just this). So it is with the second: the caesium clock is the best we've got so far, but it's just a physical embodiment of the ideal second, and we can strive to make a more accurate (with accuracy defined as in (1) above).

Comment: Experimental work and some context (Score 2) 169

by fishicist (#39338333) Attached to: Single-Ion Clock 100 Times More Accurate Than Atomic Clock
It's an exciting idea, and it's streaks ahead of 'traditional' microwave transition atomic clocks. These do not represent the state of the art, however, for which one should look at the experimentally demonstrated ~9e-18 accuracy by the Wineland group at NIST ; , or the Strontium ion clocks at NPL (Teddington, UK) Essentially, the higher the frequency, the more clicks you get in a certain time, and the more accurate your clock can be (the smaller an error one missed click would represent). The caesium atomic clock is about 10 GHz (1E10 Hz). Strontium is in the optical, so a few 100THz (1E14). Aluminium ions are at about 1PHz (1E15 Hz). This new proposal with Thorium is around 7.6eV, which is about 2PHz, so not a million miles away from the current, demonstrated, state of the art. Also... orbit of the neutron around the nucleus isn't a fair description of a magnetic dipole transition, which would more accurately be describes as a flip in the direction of the neutron's spin axis. :)

"It's when they say 2 + 2 = 5 that I begin to argue." -- Eric Pepke