Physics, Chemistry, and Mathematics

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Physics, Chemistry, and Mathematics

Postby Typhoon » Fri Dec 16, 2011 2:59 am

Three-dimensional technique on trial

Critics take a hard look at ankylography, a proposed method for revealing molecular structures from single pictures.


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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Sat Dec 24, 2011 7:12 pm

PhysOrg |Pions don't want to decay into faster-than-light neutrinos, study finds

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When an international collaboration of physicists came up with a result that punched a hole in Einstein's theory of special relativity and couldn't find any mistakes in their work, they asked the world to take a second look at their experiment.

Responding to the call was Ramanath Cowsik, PhD, professor of physics in Arts & Sciences and director of the McDonnell Center for the Space Sciences at Washington University in St. Louis.
Online and in the December 24 issue of Physical Review Letters, Cowsik and his collaborators put their finger on what appears to be an insurmountable problem with the experiment.
The OPERA experiment, a collaboration between the CERN physics laboratory in Geneva, Switzerland, and the Laboratori Nazionali del Gran Sasso (LNGS) in Gran Sasso, Italy, timed particles called neutrinos traveling through Earth from the physics laboratory CERN to a detector in an underground laboratory in Gran Sasso, a distance of some 730 kilometers, or about 450 miles.
OPERA reported online and in Physics Letters B in September that the neutrinos arrived at Gran Sasso some 60 nanoseconds sooner than they would have arrived if they were traveling at the speed of light in a vacuum.

Neutrinos are thought to have a tiny, but nonzero, mass. According to the theory of special relativity, any particle that has mass may come close to but cannot quite reach the speed of light. So superluminal (faster than light) neutrinos should not exist.
The neutrinos in the experiment were created by slamming speeding protons into a stationary target, producing a pulse of pions — unstable particles that were magnetically focused into a long tunnel where they decayed in flight into muons and neutrinos.
The muons were stopped at the end of the tunnel, but the neutrinos, which slip through matter like ghosts through walls, passed through the barrier and disappeared in the direction of Gran Sasso.

In their journal article, Cowsik and an international team of collaborators took a close look at the first step of this process. "We have investigated whether pion decays would produce superluminal neutrinos, assuming energy and momentum are conserved," he says.
The OPERA neutrinos had energies of about 17 gigaelectron volts. "They had a lot of energy but very little mass," Cowsik says, "so they should go very fast." The question is whether they went faster than the speed of light.
"We've shown in this paper that if the neutrino that comes out of a pion decay were going faster than the speed of light, the pion lifetime would get longer, and the neutrino would carry a smaller fraction of the energy shared by the neutrino and the muon," Cowsik says.
"What's more," he says, "these difficulties would only increase as the pion energy increases.
"So we are saying that in the present framework of physics, superluminal neutrinos would be difficult to produce," Cowsik explains.
In addition, he says, there's an experimental check on this theoretical conclusion. The creation of neutrinos at CERN is duplicated naturally when cosmic rays hit Earth's atmosphere.

A neutrino observatory called IceCube detects these neutrinos when they collide with other particles generating muons that leave trails of light flashes as they plow into the thick, clear ice of Antarctica.
"IceCube has seen neutrinos with energies 10,000 times higher than those the OPERA experiment is creating," Cowsik says.."Thus, the energies of their parent pions should be correspondingly high. Simple calculations, based on the conservation of energy and momentum, dictate that the lifetimes of those pions should be too long for them ever to decay into superluminal neutrinos.
"But the observation of high-energy neutrinos by IceCube indicates that these high-energy pions do decay according to the standard ideas of physics, generating neutrinos whose speed approaches that of light but never exceeds it.

Cowsik's objection to the OPERA results isn't the only one that has been raised.
Physicists Andrew G. Cohen and Sheldon L. Glashow published a paper in Physical Review Letters in October showing that superluminal neutrinos would rapidly radiate energy in the form of electron-positron pairs.
"We are saying that, given physics as we know it today, it should be hard to produce any neutrinos with superluminal velocities, and Cohen and Glashow are saying that even if you did, they'd quickly radiate away their energy and slow down," Cowsik says.
"I have very high regard for the OPERA experimenters," Cowsik adds. "They got faster-than-light speeds when they analyzed their data in March, but they struggled for months to eliminate possible errors in their experiment before publishing it.
"Not finding any mistakes," Cowsik says, "they had an ethical obligation to publish so that the community could help resolve the difficulty. That's the demanding code physicists live by," he says.
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Re: Physics, Chemistry, and Mathematics

Postby ansuchin » Mon Jan 02, 2012 12:13 am

Last year came across this splendid little Masud and Scovazzi paper in Wiley that presents a mechanism for bridging information between disparate scales that are induced by multiscale source terms. Even though I am not a climate modeler, it has stimulated my further study and consideration. Modeling error in heterogeneous systems has been a huge issue in my work, particularly in modeling the flow of multiphase fluids in reservoir engineering problems. While I am quite familiar with the up-scaling and down-scaling of the associated mathematical models, the authors proposed error estimators for the heterogeneous multiscale frameworks are quite interesting. :geek:

A heterogeneous multiscale modeling framework for hierarchical systems of partial differential equations, Int. J. Numer. Meth. Fluids 2011; 65:28–42
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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Tue Jan 03, 2012 7:59 pm

ansuchin wrote:Last year came across this splendid little Masud and Scovazzi paper in Wiley that presents a mechanism for bridging information between disparate scales that are induced by multiscale source terms. Even though I am not a climate modeler, it has stimulated my further study and consideration. Modeling error in heterogeneous systems has been a huge issue in my work, particularly in modeling the flow of multiphase fluids in reservoir engineering problems. While I am quite familiar with the up-scaling and down-scaling of the associated mathematical models, the authors proposed error estimators for the heterogeneous multiscale frameworks are quite interesting. :geek:

A heterogeneous multiscale modeling framework for hierarchical systems of partial differential equations, Int. J. Numer. Meth. Fluids 2011; 65:28–42


From the abstract, it sounds like an interesting paper that could find applications in numerous fields beyond fluids.
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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Tue Jan 03, 2012 8:02 pm

arXiv | Faster-than-Light Neutrino Puzzle Claimed Solved by Special Relativity

The relativistic motion of clocks on board GPS satellites exactly accounts for the superluminal effect, says physicist.


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It's now been three weeks since the extraordinary news that neutrinos travelling between France and Italy had been clocked moving faster than light. The experiment, known as OPERA, found that the particles produced at CERN near Geneva arrived at the Gran Sasso Laboratory in Italy some 60 nanoseconds earlier than the speed of light allows.

The result has sent a ripple of excitement through the physics community. Since then, more than 80 papers have appeared on the arXiv attempting to debunk or explain the effect. It's fair to say, however, that the general feeling is that the OPERA team must have overlooked something.

Today, Ronald van Elburg at the University of Groningen in the Netherlands makes a convincing argument that he has found the error.

First, let's review the experiment, which is simple in concept: a measurement of distance and time.

The distance is straightforward. The location of neutrino production at CERN is fairly easy to measure using GPS. The position of the Gran Sasso Laboratory is harder to pin down because it sits under a kilometre-high mountain. Nevertheless, the OPERA team says it has nailed the distance of 730 km to within 20 cm or so.

The time of neutrino flight is harder to measure. The OPERA team says it can accurately gauge the instant when the neutrinos are created and the instant they are detected using clocks at each end.

But the tricky part is keeping the clocks at either end exactly synchronised. The team does this using GPS satellites, which each broadcast a highly accurate time signal from orbit some 20,000km overhead. That introduces a number of extra complications which the team has to take into account, such as the time of travel of the GPS signals to the ground.

But van Elburg says there is one effect that the OPERA team seems to have overlooked: the relativistic motion of the GPS clocks.

It's easy to think that the motion of the satellites is irrelevant. After all, the radio waves carrying the time signal must travel at the speed of light, regardless of the satellites' speed.

But there is an additional subtlety. Although the speed of light is does not depend on the the frame of reference, the time of flight does. In this case, there are two frames of reference: the experiment on the ground and the clocks in orbit. If these are moving relative to each other, then this needs to be factored in.

So what is the satellites' motion with respect to the OPERA experiment? These probes orbit from West to East in a plane inclined at 55 degrees to the equator. Significantly, that's roughly in line with the neutrino flight path. Their relative motion is then easy to calculate.

So from the point of view of a clock on board a GPS satellite, the positions of the neutrino source and detector are changing. "From the perspective of the clock, the detector is moving towards the source and consequently the distance travelled by the particles as observed from the clock is shorter," says van Elburg.

By this he means shorter than the distance measured in the reference frame on the ground.

The OPERA team overlooks this because it thinks of the clocks as on the ground not in orbit.

How big is this effect? Van Elburg calculates that it should cause the neutrinos to arrive 32 nanoseconds early. But this must be doubled because the same error occurs at each end of the experiment. So the total correction is 64 nanoseconds, almost exactly what the OPERA team observes.

That's impressive but it's not to say the problem is done and dusted. Peer review is an essential part of the scientific process and this argument must hold its own under scrutiny from the community at large and the OPERA team in particular.

If it stands up, this episode will be laden with irony.
Far from breaking Einstein's theory of relatively, the faster-than-light measurement will turn out to be another confirmation of it.
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Re: Physics, Chemistry, and Mathematics

Postby Azrael » Wed Jan 04, 2012 1:30 am

It appears that van Elburg may have made an error, which would invalidate his conclusion.
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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Wed Jan 04, 2012 1:42 am

Mathematical Embarrassments

Mathematical embarrassments are problems that should be solved already


What is it like to have an understanding of very advanced mathematics?
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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Wed Jan 04, 2012 7:42 pm

Azrael wrote:It appears that van Elburg may have made an error, which would invalidate his conclusion.


Surprised to see what appears to be a basic SR error. Back to the drawing board.
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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Thu Jan 05, 2012 5:35 pm

Cornell | Cloaking a moment in time

In movie magic, people and objects can appear or disappear or move from place to place in an instant. Just stop the camera, move things around and start it again. Now, Cornell researchers have demonstrated a similar "temporal cloak" -- albeit on a very small scale -- in the transport of information by a beam of light.
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Re: Physics, Chemistry, and Mathematics

Postby ansuchin » Fri Jan 06, 2012 12:47 am

Typhoon wrote:Mathematical Embarrassments

Mathematical embarrassments are problems that should be solved already


What is it like to have an understanding of very advanced mathematics?


Thanks Typhoon. Great thread by Dick Lipton. 8-)

Terry Tao's great blog for the interested is here. Much of his blog is directed to graduate mathematicians but he does have a section that is not as technical.

Terry is not just an exceptionally gifted mathematician, but probably one of the most creative and productive mathematicians of our time. I met him before I left the states. He presents a mix of shyness and a barely contained, brilliant enthusiasm. A genuinely, friendly, helpful, and nice man. No Perelmanish misanthropy for him. :D

As far as understanding advanced mathematics goes, that aptitude has always seemed to me to be close to a combination of linguistic and music skills. Some of the most natural mathematicians I have known accomplish musical instrument and theory skills quite easily as well as a capacity to pick up new languages. Perhaps it has something to do with the posterior left hemisphere of the brain that may be involved in these matters.
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Re: Physics, Chemistry, and Mathematics

Postby Azrael » Fri Jan 06, 2012 2:07 am

Typhoon wrote:Mathematical Embarrassments

Mathematical embarrassments are problems that should be solved already


Some Examples

The and problem. The problem is to prove that and are both transcendental numbers. We know that one of these must be transcendental. For if both were algebraic, then so would,

1/2 * (pi + e + pi - e) = pi

which contradicts the known fact that is transcendental.


Hopefully the embarrassment over this will motivate proving Schanuel's conjecture.
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Re: Physics, Chemistry, and Mathematics

Postby AzariLoveIran » Fri Jan 06, 2012 3:41 am

.


Sometimes its better to believe in yourself


"Man will never reach the moon regardless of all future scientific advances."
-- Dr. Lee DeForest, "Father of Radio & Grandfather of Television."

"The bomb will never go off. I speak as an expert in explosives."
- - Admiral William Leahy , US Atomic Bomb Project

"There is no likelihood man can ever tap the power of the atom."
-- Robert Millikan, Nobel Prize in Physics, 1923

"Computers in the future may weigh no more than 1.5 tons."
-- Popular Mechanics, forecasting the relentless march of science, 1949

"I think there is a world market for maybe five computers."
-- Thomas Watson, chairman of IBM, 1943

"I have traveled the length and breadth of this country and talked with the best people, and I can assure you that data processing is a fad that won't last out the year."
-- The editor in charge of business books for Prentice Hall, 1957

"But what is it good for?"
-- Engineer at the Advanced Computing Systems Division of IBM, 1968, commenting on the microchip.

"640K ought to be enough for anybody."
-- Bill Gates, 1981

This 'telephone' has too many shortcomings to be seriously considered as a means of communication. The device is inherently of no value to us,"
-- Western Union internal memo, 1876.

"The wireless music box has no imaginable commercial value. Who would pay for a message sent to nobody in particular?"
-- David Sarnoff's associates in response to his urgings for investment in the radio in the 1920s.

"The concept is interesting and well-formed, but in order to earn better than a 'C,' the idea must be feasible,"
-- A Yale University management professor in response to Fred Smith's paper proposing reliable overnight delivery service. (Smith went on to found Federal Express Corp.)

"I'm just glad it'll be Clark Gable who's falling on his face and not Gary Cooper,"
-- Gary Cooper on his decision not to take the leading role in "Gone With The Wind."

"A cookie store is a bad idea. Besides, the market research reports say America likes crispy cookies, not soft and chewy cookies like you make,"
-- Response to Debbi Fields' idea of starting Mrs. Fields' Cookies.

"We don't like their sound, and guitar music is on the way out,"
-- Decca Recording Co. rejecting the Beatles, 1962.

"Heavier-than-air flying machines are impossible,"
-- Lord Kelvin, president, Royal Society, 1895.

"If I had thought about it, I wouldn't have done the experiment. The literature was full of examples that said you can't do this,"
- - Spencer Silver on the work that led to the unique adhesives for 3-M "Post-It" Notepads.

"Drill for oil? You mean drill into the ground to try and find oil? You're crazy,"
-- Drillers who Edwin L. Drake tried to enlist to his project to drill for oil in 1859.

"Stocks have reached what looks like a permanently high plateau."
-- Irving Fisher, Professor of Economics, Yale University , 1929.

"Airplanes are interesting toys but of no military value,"
-- Marechal Ferdinand Foch, Professor of Strategy, Ecole Superieure de Guerre , France ..

"Everything that can be invented has been invented,"
-- Charles H. Duell, Commissioner, US Office of Patents, 1899.

"The super computer is technologically impossible. It would take all of the water that flows over Niagara Falls to cool the heat generated by the number of vacuum tubes required."
-- Professor of Electrical Engineering, New York University

"I don't know what use any one could find for a machine that would make copies of documents. It certainly couldn't be a feasible business by itself."
-- the head of IBM, refusing to back the idea, forcing the inventor to found Xerox.

"Louis Pasteur's theory of germs is ridiculous fiction."
-- Pierre Pachet, Professor of Physiology at Toulouse , 1872

"The abdomen, the chest, and the brain will forever be shut from the intrusion of the wise and humane surgeon,"
-- Sir John Eric Ericksen, British surgeon, appointed Surgeon-Extraordinary to Queen Victoria 1873.

And last but not least...
"There is no reason anyone would want a computer in their home."
-- Ken Olson, president, chairman and founder of Digital Equipment Corp., 1977

Lotfi's Additions:

"There is no problem in applied mathematics that this computer cannot solve."
-- Professor Howard Aiken, Director of Harvard's Computation Laboratory, on the occasion of the inauguration of IBM's relay computer; this computer had a memory of about 1000 words, 1948.

“Fuzzy theory is wrong, wrong, and pernicious. I cannot think of any problem that could not be solved better by ordinary logic... The danger of fuzzy theory is that it will encourage the sort of imprecise thinking that has brought us so much trouble.”
--William Kahan, a recipient of the Turing Prize and a professor of computer sciences and mathematics at Cal who is a colleague of Lotfi Zadeh.
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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Fri Jan 06, 2012 3:32 pm

Classic quotes.

Evidence that the track record of experts in predicting the future in their or related fields is no better than than of anyone else.
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Re: Physics, Chemistry, and Mathematics

Postby AzariLoveIran » Fri Jan 06, 2012 5:14 pm

Typhoon wrote:.

Classic quotes.

Evidence that the track record of experts in predicting the future in their or related fields is no better than that of anyone else.

.


scientist no visionary

Vision need phantasy, dream and chance for reality

all, with very few exception (maybe Einstein exception), scientist had any phantasy

.
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Re: Physics, Chemistry, and Mathematics

Postby ansuchin » Sat Jan 07, 2012 12:09 am

AzariLoveIran wrote:
Typhoon wrote:.

Classic quotes.

Evidence that the track record of experts in predicting the future in their or related fields is no better than that of anyone else.

.


scientist no visionary

Vision need phantasy, dream and chance for reality

all, with very few exception (maybe Einstein exception), scientist had any phantasy

.

That is not really true, Azari. To do science one must be able to generate hypotheses, theories, and possible relationships in nature that have not been tested or confirmed. As such, these conjectures, which form the starting point of scientific investigations, often remain no more than imaginative fantasies formed by a vision inspired by observed anomalous phenomena and mathematical results. As Thomas Kuhn noted:

Scientific development depends on a process of non-incremental or revolutionary change. Some revolutions are large, like those associated with the names of Copernicus, Newton, or Darwin, but most are much smaller, like the discovery of oxygen or the planet Uranus. The usual prelude to changes of this sort is, I believed, the awareness of anomaly, of an occurrence or set of occurrences that does not fit existing ways of ordering phenomena. The changes that result therefore require 'putting on a different kind of thinking-cap', one that renders the anomalous law like but that, in the process, also transforms the order exhibited by some other phenomena, previously unproblematic.

Such functions require true creative vision, but a vision one must be willing to articulate in a way that it can be proven wrong within established methodology. Artists, writers, and musicians do not have to face the rigour of scientific method, they need the confirmation of an audience or of patrons - who are far more irrational and unpredictable. I would rather be a mathematician.

Some of the most dynamic and creative people I have known have been scientists and mathematicians. Those who can simply solve technical problems based upon established principles have their place, but such students, in my experience, are incapable of doing science or comprehending advanced mathematics.
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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Mon Jan 09, 2012 4:28 am

ansuchin wrote:
AzariLoveIran wrote:
Typhoon wrote:.

Classic quotes.

Evidence that the track record of experts in predicting the future in their or related fields is no better than that of anyone else.

.


scientist no visionary

Vision need phantasy, dream and chance for reality

all, with very few exception (maybe Einstein exception), scientist had any phantasy

.

That is not really true, Azari. To do science one must be able to generate hypotheses, theories, and possible relationships in nature that have not been tested or confirmed. As such, these conjectures, which form the starting point of scientific investigations, often remain no more than imaginative fantasies formed by a vision inspired by observed anomalous phenomena and mathematical results. As Thomas Kuhn noted:

Scientific development depends on a process of non-incremental or revolutionary change. Some revolutions are large, like those associated with the names of Copernicus, Newton, or Darwin, but most are much smaller, like the discovery of oxygen or the planet Uranus. The usual prelude to changes of this sort is, I believed, the awareness of anomaly, of an occurrence or set of occurrences that does not fit existing ways of ordering phenomena. The changes that result therefore require 'putting on a different kind of thinking-cap', one that renders the anomalous law like but that, in the process, also transforms the order exhibited by some other phenomena, previously unproblematic.

Such functions require true creative vision, but a vision one must be willing to articulate in a way that it can be proven wrong within established methodology. Artists, writers, and musicians do not have to face the rigour of scientific method, they need the confirmation of an audience or of patrons - who are far more irrational and unpredictable. I would rather be a mathematician.

Some of the most dynamic and creative people I have known have been scientists and mathematicians. Those who can simply solve technical problems based upon established principles have their place, but such students, in my experience, are incapable of doing science or comprehending advanced mathematics.


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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Mon Jan 09, 2012 4:30 am

Nature | Mathematician claims breakthrough in Sudoku puzzle

Puzzles must have at least 17 clues to have a valid solution.

An Irish mathematician has used a complex algorithm and millions of hours of supercomputing time to solve an important open problem in the mathematics of Sudoku, the game popularized in Japan that involves filling in a 9X9 grid of squares with the numbers 1–9 according to certain rules.

Gary McGuire of University College Dublin shows in a proof posted online on 1 January1 that the minimum number of clues — or starting digits — needed to complete a puzzle is 17; puzzles with 16 or fewer clues do not have a unique solution. Most newspaper puzzles have around 25 clues, with the difficulty of the puzzle decreasing as more clues are given.
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Re: Physics, Chemistry, and Mathematics

Postby AzariLoveIran » Mon Jan 09, 2012 5:12 am

ansuchin wrote:.
AzariLoveIran wrote:.
Typhoon wrote:.

Classic quotes.

Evidence that the track record of experts in predicting the future in their or related fields is no better than that of anyone else.

.


scientist no visionary

Vision need phantasy, dream and chance for reality

all, with very few exception (maybe Einstein exception), scientist had any phantasy

.


That is not really true, Azari. To do science one must be able to generate hypotheses, theories, and possible relationships in nature that have not been tested or confirmed. As such, these conjectures, which form the starting point of scientific investigations, often remain no more than imaginative fantasies formed by a vision inspired by observed anomalous phenomena and mathematical results. As Thomas Kuhn noted:

.

Scientific development depends on a process of non-incremental or revolutionary change. Some revolutions are large, like those associated with the names of Copernicus, Newton, or Darwin, but most are much smaller, like the discovery of oxygen or the planet Uranus. The usual prelude to changes of this sort is, I believed, the awareness of anomaly, of an occurrence or set of occurrences that does not fit existing ways of ordering phenomena. The changes that result therefore require 'putting on a different kind of thinking-cap', one that renders the anomalous law like but that, in the process, also transforms the order exhibited by some other phenomena, previously unproblematic.

.


Such functions require true creative vision, but a vision one must be willing to articulate in a way that it can be proven wrong within established methodology. Artists, writers, and musicians do not have to face the rigour of scientific method, they need the confirmation of an audience or of patrons - who are far more irrational and unpredictable. I would rather be a mathematician.

Some of the most dynamic and creative people I have known have been scientists and mathematicians. Those who can simply solve technical problems based upon established principles have their place, but such students, in my experience, are incapable of doing science or comprehending advanced mathematics.

.



Ansuch ,

Phantasy is something different than " hypotheses, theories, and possible relationships in nature, whether tested or confirmed "

Phantasy lacks any reason & logic, usually crazy, ridiculous AND stupid

Phantasy not same as imagination

imagination reason & logic based, not so Phantasy

Imagination is more important than knowledge.
Albert Einstein

Imagination is everything. It is the preview of life's coming attractions.
Albert Einstein

.
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Re: Physics, Chemistry, and Mathematics

Postby Azrael » Mon Jan 09, 2012 8:13 pm

Azrael wrote:
Typhoon wrote:Mathematical Embarrassments

Mathematical embarrassments are problems that should be solved already


Some Examples

The and problem. The problem is to prove that and are both transcendental numbers. We know that one of these must be transcendental. For if both were algebraic, then so would,

1/2 * (pi + e + pi - e) = pi

which contradicts the known fact that is transcendental.


Hopefully the embarrassment over this will motivate proving Schanuel's conjecture.


Top Ten Transcendental Numbers
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Re: Physics, Chemistry, and Mathematics

Postby Antipatros » Wed Feb 01, 2012 5:03 pm

Chun-Yung Sung and Ji Ung Lee, Graphene: The Ultimate Switch

Graphene could replace the transistor with switches that steer electrons just like beams of light

http://spectrum.ieee.org/semiconductors/materials/graphene-the-ultimate-switch/0

From the outside, transistors seem so simple and straightforward. But inside, they're actually a mess. If you could watch them working at the level of atoms, you'd see the electronic equivalent of a game of bumper cars. Electrons moving through even the best transistor channel can't go in straight lines. Instead they're buffeted continually by a host of imperfections and vibrations, which together put a strict limit on speed and generate a lot of heat in the process.

The good news is that it doesn't have to be that way. By a quirk of quantum mechanics, electrons moving through atom-thick sheets of carbon—known as graphene—don't suffer much at all from these sorts of collisions. Instead, they behave like massless particles, speeding along in straight lines for long distances just like photons do. And just like light, these electrons can be made to bend or bounce back when they move from one medium to another.

What can you do with this light-mimicking behavior? Well, here's what we'd like to do: Replace the logic circuitry at the heart of every computer processor. Everyone today agrees that the days of the ever-shrinking CMOS transistor are numbered; the only disagreement is about what that number is. After 50 years of steady miniaturization, chipmakers have just about shrunk the device to its limits. The future gets hazy beyond 2020, but we know that to continue making faster, cheaper, and more energy efficient chips, we'll need a new technology....
Be not too curious of Good and Evil;
Seek not to count the future waves of Time;
But be ye satisfied that you have light
Enough to take your step and find your foothold.

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Re: Physics, Chemistry, and Mathematics

Postby Antipatros » Wed Feb 01, 2012 5:04 pm

Richard B. Miles, Arthur Dogariu, and James B. Michael, Using Lasers to Find Land Mines and IEDs

A laser could ionize a distant puff of air and thus safely detect the fumes from buried explosives

http://spectrum.ieee.org/semiconductors/optoelectronics/using-lasers-to-find-land-mines-and-ieds/0

Today we rely on dogs to sniff out hidden explosives. The problem is, you can't debrief a dog, so you can't identify the kind of explosive or even be sure that the animal is smelling explosives rather than packaging material. And who wants to risk the lives of dogs and their handlers? If you had an instrument that could safely identify any explosive at a distance—with the doglike power to detect molecules at concentrations of just one part in billions—you could get around these difficulties.

The problem of land mines is certainly not new, nor is even the problem of hidden homemade bombs, called improvised explosive devices (IEDs), although the latter came to prominence during the wars in Iraq and Afghanistan. Now these ghastly devices are proliferating around the world: The number of such bombings has increased from close to zero a decade ago to more than 4 000 per year in Afghanistan alone. It's a concern that will be with us for a long time, and as such it deserves serious efforts to address. Nor is the problem merely one of war and sabotage. Any device capable of sniffing explosives at a distance could also monitor all sorts of peacetime poisons and pollutants—carbon monoxide, mercury vapor, the oxides of nitrogen and of sulfur, and of course carbon dioxide and methane, the principal greenhouse gases.

We propose to find and identify such materials at a distance by using a laser to sample the spectroscopic fingerprints of trace gases in a distant volume of air. We use two complementary techniques to probe that volume: one involving a backward-propagating laser generated in the air sample itself, and the other a radar echo off ions and electrons from trace gas molecules that have been selectively ionized by a laser. At Princeton University we are examining both approaches because either one, taken alone, may sometimes be inconclusive and because at this early stage in development it's important to have more than one option. We've already achieved promising results in our research, which has been funded by the United States' Office of Naval Research....
Be not too curious of Good and Evil;
Seek not to count the future waves of Time;
But be ye satisfied that you have light
Enough to take your step and find your foothold.

--T.S. Eliot
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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Tue Feb 14, 2012 2:56 am

Phys Rev Lett | Ponytail physics

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Ponytailed physics professors may now be able to use their coif as a lecture prop. Researchers have for the first time disentangled the factors that determine how hairs hang together, as reported in Physical Review Letters. The analytical model, which was based on a statistical characterization of ponytail shapes, treats the forces on individual hair fibers as continuous quantities inside a hair bundle. The resulting hair “equation of state” could apply to other fibers in biology and industry.

Many scientists (and even more hairdressers) have wondered about the meanderings of hair. Leonardo da Vinci thought hair flowed like water, and this sort of fluid analogy has guided computer animators trying to recreate hair and fur on the movie screen. However, no model has yet addressed one of the most basic hair problems: what shape is a ponytail?

For their part, Raymond Goldstein of the University of Cambridge, UK, and his colleagues obtained human hair switches (a type of commercially available hairpiece) and measured the random curvature (or curliness) of a sample of individual hairs. They then assembled different ponytails—all about 25 centimeters long—and recorded the average shape. This data helped in the formulation of an equation of state that balanced four competing effects: gravity, tension, an elastic restoring force, and a “swelling pressure” coming from the curliness. The model correctly predicted the shape of ponytails as the lengths of the switches were progressively shortened. The authors believe their surprisingly simple equation of state could be used to study other hair “styles,” as well as dynamic problems like a swinging ponytail.
All the world's a stage.
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Re: Physics, Chemistry, and Mathematics

Postby Sparky » Thu Feb 16, 2012 7:57 pm

Typhoon wrote:Phys Rev Lett | Ponytail physics

Image

Ponytailed physics professors may now be able to use their coif as a lecture prop. Researchers have for the first time disentangled the factors that determine how hairs hang together, as reported in Physical Review Letters. The analytical model, which was based on a statistical characterization of ponytail shapes, treats the forces on individual hair fibers as continuous quantities inside a hair bundle. The resulting hair “equation of state” could apply to other fibers in biology and industry.

Many scientists (and even more hairdressers) have wondered about the meanderings of hair. Leonardo da Vinci thought hair flowed like water, and this sort of fluid analogy has guided computer animators trying to recreate hair and fur on the movie screen. However, no model has yet addressed one of the most basic hair problems: what shape is a ponytail?

For their part, Raymond Goldstein of the University of Cambridge, UK, and his colleagues obtained human hair switches (a type of commercially available hairpiece) and measured the random curvature (or curliness) of a sample of individual hairs. They then assembled different ponytails—all about 25 centimeters long—and recorded the average shape. This data helped in the formulation of an equation of state that balanced four competing effects: gravity, tension, an elastic restoring force, and a “swelling pressure” coming from the curliness. The model correctly predicted the shape of ponytails as the lengths of the switches were progressively shortened. The authors believe their surprisingly simple equation of state could be used to study other hair “styles,” as well as dynamic problems like a swinging ponytail.

Ahh, so that explains the Beautiful Women thread - you're writing a paper! :)
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Re: Physics, Chemistry, and Mathematics

Postby Typhoon » Fri Feb 17, 2012 2:58 pm

Sparky wrote: . . .
Ahh, so that explains the Beautiful Women thread - you're writing a paper! :)


I've been found out :wink:
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Re: Physics, Chemistry, and Mathematics

Postby Nonc Hilaire » Fri Feb 17, 2012 3:08 pm

Typhoon wrote:
Sparky wrote: . . .
Ahh, so that explains the Beautiful Women thread - you're writing a paper! :)


I've been found out :wink:

Here you go, Typhoon. You will be needing these.
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“Christ has no body now but yours. Yours are the eyes through which he looks with compassion on this world. Yours are the feet with which he walks among His people to do good. Yours are the hands through which he blesses His creation.”

Teresa of Ávila
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