Friday, July 30, 2010

Theoretical and Experimental Analysis of the Physics of Water Rockets

When I read the title of this paper, my first remark was "No!!".

Anyone reading this blog for a while would have seen my entry on The Physics of Human Bottle Rocket, which includes a crazy video of a crazy man being strapped to one of these bottle rocket. So now it appears that there is a paper describing water rockets. I'm not sure if it is the same thing, but it is amusing nevertheless.

R Barrio-Perotti et al., Eur. J. Phys. v. 31, p.1131 (2010).

Abstract:A simple rocket can be made using a plastic bottle filled with a volume of water and pressurized air. When opened, the air pressure pushes the water out of the bottle. This causes an increase in the bottle momentum so that it can be propelled to fairly long distances or heights. Water rockets are widely used as an educational activity, and several mathematical models have been proposed to investigate and predict their physics. However, the real equations that describe the physics of the rockets are so complicated that certain assumptions are usually made to obtain models that are easier to use. These models provide relatively good predictions but fail in describing the complex physics of the flow. This paper presents a detailed theoretical analysis of the physics of water rockets that concludes with the proposal of a physical model. The validity of the model is checked by a series of field tests. The tests showed maximum differences with predictions of about 6%. The proposed model is finally used to investigate the temporal evolution of some significant variables during the propulsion and flight of the rocket. The experience and procedure described in this paper can be proposed to graduate students and also at undergraduate level if certain simplifications are assumed in the general equations.

Published 29 July 2010

Note that you may obtain a free copy of the paper within 30 days of online publication.


Probing the Superfluid–to–Mott Insulator Transition at the Single-Atom Level

I continue to be amazed at such optical lattice experiments. The ability to trap atoms in lasers and have each atom placed in an optical lattice is such an amazing accomplishment. It opens the door to performing so many studies on strongly correlated systems since the strength of the individual coupling can be tuned via the optical lattice separation.

A new experiment using such technique has appeared in Science this week.

W.S. Bakr et al., Science v.329, p.547 (2010).

Abstract: Quantum gases in optical lattices offer an opportunity to experimentally realize and explore condensed matter models in a clean, tunable system. We used single atom–single lattice site imaging to investigate the Bose-Hubbard model on a microscopic level. Our technique enables space- and time-resolved characterization of the number statistics across the superfluid–Mott insulator quantum phase transition. Site-resolved probing of fluctuations provides us with a sensitive local thermometer, allows us to identify microscopic heterostructures of low-entropy Mott domains, and enables us to measure local quantum dynamics, revealing surprisingly fast transition time scales. Our results may serve as a benchmark for theoretical studies of quantum dynamics, and may guide the engineering of low-entropy phases in a lattice.

Read the Perspective on this work in the same issue of Science.


Thursday, July 29, 2010

APS Journals Available For Free In US Public Libraries

Latest press release from the APS:

Ridge, New York: The American Physical Society (APS) announces a new public access initiative that will give readers and researchers in public libraries in the United States full use of all online APS journals, from the most recent articles back to the first issue in 1893, a collection including over 400,000 scientific research papers. APS will provide this access at no cost to participating public libraries, as a contribution to public engagement with the ongoing development of scientific understanding.
APS Publisher Joseph Serene observed that "public libraries have long played a central role in our country’s intellectual life, and we hope that through this initiative they will become an important avenue for the general public to reach our research journals, which until now have been available only through the subscriptions at research institutions that currently cover the significant costs of peer review and online publication.”

Librarians can obtain access by accepting a simple online site license and providing valid IP addresses of public-use computers in their libraries ( The license requires that public library users must be in the library when they read the APS journals or download articles. Initially the program will be offered to U.S. public libraries, but it may include additional countries in the future.
"The Public Library program is entirely consistent with the APS objective to advance and diffuse the knowledge of physics," said Gene Sprouse, APS Editor in Chief. "Our goal is to provide access to everyone who wants and needs our journals and this shift in policy represents the first of several steps the APS is taking towards that goal."

-Contact: Amy Halsted, Special Assistant to the Editor in Chief,, 631-591-4232

-About the APS: The American Physical Society is the world’s largest professional body of physicists, representing close to 48,000 physicists in academia and industry worldwide. It has offices in Ridge, NY; Washington, DC; and College Park, MD. For more information:

This gives the public, if they so wish to take advantage of it, access to some of the most widely-read and prestigious journals in physics, such as the Physical Review Letters, the Physical Review family of journals, and valuable review articles in Review of Modern Physics.

As a member of the APS, I am proud that the APS is making these journals available to the public via the public libraries. They now have ample access to these journals. Now, the question is, what can they do with such access and such information?


Human "Literacy Package" Should Include Science

This is a well-written essay on why everyone should have a good set of understanding of science as part of his/her education.

Does it matter? No doubt historians complain of a lack of historical knowledge in society and French teachers of a lack of awareness of French literature. However, I think science is different, for two reasons.

First, many challenges facing modern society involve a basic understanding of science. Issues such as the safety of commercial nuclear power, the ethics of embryonic stem-cell research, or action on greenhouse gas emissions all demand a basic knowledge of scientific concepts, and how scientific facts are established. This latter is the more important point – an understanding of the built-in scepticism of the scientific method builds confidence in scientific discovery.

Instead, public discourse on important scientific issues is often dominated by media commentary that has little idea of the methods of science, and that fails to distinguish between informed and uninformed opinion (not to mention vested interests). For example, much of the current “debate” concerning the reality of human-induced global warming occurs not within science, but in the media – a public scepticism that takes little account of the robustness of modern scientific enquiry.

A second, and often overlooked, reason for a public understanding of science is that science is part of the human experience, just as history and music are. Not everyone may want to partake in the actual discovery of the workings of the natural world, but they deserve to know what has been discovered! This science-as-culture argument was first articulated by the physicist C P Snow when he realised that he could engage in literary discussion with friends in the humanities, while they knew nothing of his subject. Indeed, he felt that the general public was being cheated out of a scientific education.

Actually, it goes beyond just having a set of knowledge to be able to comprehend all of the issues in our lives. A science education, one would hope, will give someone the skill to be able to think analytically and systematically. This allows for someone to know and categorize the degree of certainty of something he/she has accepted. Everything that we have accepted has varying degree of certainty. You may let someone buys you lunch, but you may not trust that person enough to look after your kids. You may read your horoscope, but  do you accept it strong enough to be valid as to put your life and the lives of your loved ones on it? Knowing how we arrive at our opinion and how strong of a certainty we can put on that opinion is something very important, and something that one does not hear at all when dealing with complicated social, economic, and political issues. Various people and parties state their point of view with utter certainty. Yet, we always end up with all kinds of mess. If these people believe that they are THAT correct, why are they often wrong? A clear lesson on putting the degree of certainty on any kind of knowledge is something valuable that can be learned from a good science education.


Wednesday, July 28, 2010

"Switching Off" the Heisenberg Uncertainty Principle

A new scheme in quantum information measurement has been proposed that might, under certain situation, defeat the limit imposed by the Heisenberg Uncertainty principle (HUP). Instead of gathering information about the state from a "classical memory", the "... particle is prepared entangled with a quantum memory.. ", which is still a device that we do not have yet.

Heisenberg’s uncertainty principle applies wherever predictions about measured quantum mechanical variables are made on the basis of classical data. It arises due to the fact that, in quantum mechanics, there are no clearly defined 0 and 1 states like those of a bit in a classical computer, and instead several alternative possibilities can exist simultaneously. “If we collect the available information about a particle in a quantum memory, this makes this information more valuable than information gathered in a classical way,” says Renato Renner, Assistant Professor at the Institute for Theoretical Physics of ETH Zurich and co-author of the paper. These quantum data then theoretically allow measured variables to be predicted with any desired precision, and the Heisenberg uncertainty becomes arbitrarily small.
We will just have to see if such a quantum memory can be produced.


Tuesday, July 27, 2010

In Defense Of Basic Science

Another good article by Marcelo Gleiser on the need for "basic science" research.

Think, for example, of the development of quantum mechanics, the physics that studies the behavior of atoms and molecules. Early in the 20th century, when scientists such as Planck, Einstein, Bohr, Schrödinger and Heisenberg were trying to understand the behavior of the atom, they couldn’t have imagined that their theories would revolutionize the way we think about reality and, as a bonus, the way we live. Transistors, semiconductors, lasers, the whole digital technology of modern life emerged as a consequence of their musings. And it was from atomic and nuclear physics that new forms of radiation were discovered, such as the X rays that changed the face of medicine and genetics, and the nuclear weapons that changed history. Wherever there is light there is shadow, as said the Buddha.

To think of the inapplicability of basic science in the short term creates the false notion that most theoretical speculations will never turn out to be of practical value, which is clearly not the case.

None of his argument should be new to anyone reading this blog for any considerable period of time. The amount of money that we spend on purely "basic research" is puny compared to everything else. People arguing against such funding is trying to take very little money out of a very little pot that didn't have much in the first place.

Strangely enough, many of the problems that people keep telling scientists to solve are really not scientific problem, but more of the social/economic problems. They tend to ask why we can't provide more food to such-and-such people, when the while issue often isn't the lack of food, but the inability to deliver them, or the inability for those people to farm, due to political/social unrest. Besides, these very same people need to go argue against those who are anti-science and think that science is the cause of all of our problems.


Monday, July 26, 2010

LHC - Coldest Place In The Universe?

This news report covers the recent high energy physics meeting in France. One of the most important outcome of the meeting was the urge to build the ILC as the next generation particle collider to refine the results obtained at the LHC.

That is all fine and dandy. However, my eyes widened when I read this paragraph:

In March, the Large Hadron Collider produced a tiny bang, the most potent force on the tiny atomic level that humans have ever created.

Two beams of protons were sent hurtling in opposite directions toward each other in a 17-mile (27-kilometer) tunnel below the Swiss-French border — the coldest place in the universe at slightly above absolute zero.

Two problems with this last part:

1. LHC uses superconducting magnets to steer and control the proton beams. The beams do not collide under cryogenic temperatures. As far as I know, none of the detectors (ATLAS, CMS, etc.) are "superconducting".

2. While the magnets are cooled using liquid Helium, I can't imagine them being any lower than 1K. This is not "cold" at all, considering that we can get to milli Kelvin temperatures in many experiments already. So even on earth, the LHC is not the coldest place. I would guess that the rest of the Universe will have quite a say in that claim.

I suppose this is another example of a bit of bad reporting.


Experimental Error

A little bit of humor never hurts. Here's one that comes along with a criticism on perpetuating the perception of what a scientist is and what she/she does.

We are distrusted, feared, but most of all, misunderstood. We work, after all, in one of the only two professions that idiomatically follow the word "mad" -- the other such profession being "hatter."

Is it any wonder, though, that people don't understand what scientists actually do? Think of all the demonstrations you watched as a kid, your first introduction to the field. Among the brightly colored liquids bubbling with dry ice, did a physicist show you a diagram of a particle accelerator? Did a microbiologist talk about colony-forming units? Did a geologist explain how to date a core sample?

Or was your liaison to the scientific universe some doofus in a lab coat who showed you how to make your own silly putty? (Two parts glue, one part liquid starch.)

One can clearly see such misconception when children draw us before meeting us. It is also unfortunate that science demonstrations had to have these fantastic explosions etc. just to keep them "interesting". They gave the wrong impression of what we do.

Still, contrary to what was stated at the end of that article on what scientists actually do, many of us continue to actually do science. This is certainly true if one is working in a smaller group where manpower is limited. I know that I continue to do all the dirty work and the data-taking, even when I have students around.


CERN To Idle All Of Its Accelerators In 2012

We knew the LHC shutdown was coming, but no one was prepared for the extent of the shutdown that is widespread throughout the LHC.

CERN management has announced that the scheduled LHC shutdown in 2012 will be extremely widespread and will require extensive manpower that all of its accelerator operations will also be shut down.

Most crucially, the CERN brass say the shutdown will allow them to redo thousands of unreliable solder connections between the accelerator's massive superconducting magnets and make other modifications. Today, Stephen Myers, CERN's director for accelerators and technology, told the 1000 physicists gathered here for the annual International Conference on High Energy Physics that the shutdown will be extended from 12 months to 15 months. Even with the extra time, CERN will need all the workers it can get, which is why they're shutting down all eight of the lab's accelerators. "Our plan is to stop all of the accelerators at CERN and redeploy manpower," Myers says.

That will most likely come as hard news to hundreds of physicists working on smaller experiments fed by those other accelerators, such as the 200 working on the OPERA neutrino experiment in the underground Gran Sasso National Laboratory in Italy. For a year, CERN will stop sending a beam of neutrinos to Gran Sasso, turn off the flow of antiprotons for antihydrogen experiments, and cease the production of radioactive isotopes for nuclear science experiments. But that's a price CERN is willing to pay to get the LHC running at full energy and intensity, Myers says: "Our priority is the LHC." He notes that CERN also stopped all of its accelerators in 2005 to focus on problems in the LHC's construction.

Again, it is understandable that, for the LHC to run at the energy that it was designed, all of the suspected electrical problems must be resolved or they'll have another disaster like the last one. So one can certainly see them putting all of their resources into making sure the main experiment, the LHC, is running the way it should, or else the whole point of building the facility in the first place is gone.

Still, all of those experiments will go for a year or more with no data, and it gives a glimmer of hope to the Tevatron that its life will be extended for a couple more years.


Friday, July 23, 2010

Fermilab Seeks To Extend Tevatron's Life

In the race to be the first to find the Higgs, Fermilab is being reported to request an extension to the Tevatron's life into 2014 to continue seeking the Higgs.

“We have made big progress at the Tevatron… we have collected lots of data over the last couple of years and this will help us to exclude a significant range of possible Higgs masses,” Stefan Soldner-Rembold, spokesman for the DZero experiment at the Tevatron, told BBC News.

“This will make the region where the Higgs boson can hide smaller and smaller,” he added.

Experts and physicists expect the Tevatron to be delivering more data per experiment by the end of 2011. Improved analysis techniques could further boost the chances of detecting the Higgs signal.

A decision on the extension could come by the end of the year. As of yet, financing and staffing has not been worked out.

Good luck to them! It certainly will make this race very interesting if the Tevatron continues to run while the LHC is powering up.


Thursday, July 22, 2010

Quantum Mechanics Wins Again!

Looks like the more they test it, the more convincing it becomes.

The latest test in the validity of one of the fundamental postulates of quantum mechanics has been done, and QM wins once again!

"In principle, this experiment is very simple," says Gregor Weihs “and we were quite surprised to find that nobody hadn’t performed this experiment before." However, the physicists were struggling with measurement errors, which they were eventually able to overcome during their two year long Sisyphean task. "Our measurements show that we can rule out the existence of third-order interference up to a certain bound," says a happy experimental physicist Weihs. His next step will be to considerably lower the bound with an improved experiment.

U.Sinha, et al., Science v.329, p.418 (2010).

More review of this work at Nature (link open for free only for a limited time) and at PhysicsWorld.


Wednesday, July 21, 2010

Albert Einstein - The Musician

The IoP has produced a couple of videos titled "Einstein's Universe: the scientist, the man, the musician". This is the brief synopsis of the videos:

Particle physicist Brian Foster of the University of Oxford, UK, has teamed up with the British classical musician Jack Liebeck to create a special lecture and performance about Einstein's legacy to physics and the role music played in his life. The show, called "Einstein's Universe", is currently touring the UK. In this exclusive report for, James Dacey talked to the pair before a recent performance at St George's concert hall in Bristol. In [the second] video for, the pair also perform an arrangement of a violin sonata by Mozart in C Major k.296.

Here are the two videos:


Mean Free Path In Soccer And Gasses

An interesting title on a familiar topic. This paper presents an intro to students on the concept of kinetic theory of ideal gas, and explains the concept of mean free path in gasses using an analogous approach to the "mean free path" of a soccer ball during a soccer match.

J. Luzuriaga, Eur. J. Phys. v.31, p.1071 (2010).

The trajectories of the molecules in an ideal gas and of the ball in a soccer game are compared. The great difference between these motions and some similarities are discussed. This example could be suitable for discussing many concepts in kinetic theory in a way that can be pictured by students for getting a more intuitive understanding. It could be suitable for an introductory course in vacuum techniques or undergraduate courses in kinetic theory of gases. Without going into the slightly harder quantitative results, the analysis presented might be used for introducing some ideas of kinetic theory qualitatively to high school students.

Published 21 July 2010

Note that you could get a free copy of the paper within 30 days of online publication.


Tuesday, July 20, 2010

God In The Classroom

This is a very fascinating and provocative (?) opinion piece in The Guardian. A physics school teacher started with the situation where he was asked if he believed in God. He then proceeded what he hoped a science education will impart to the students, especially if the students already came in with a religious belief.

Despite appearances to the contrary, science in schools is not just about teaching facts and figures, it is about teaching the way in which humans have arrived at answers to questions ranging from how life reproduces itself to how the stars shine. Science lessons should equip students with critical thinking skills, the most important of which is to ask for evidence for claims about "truth". If we've succeeded in teaching these skills, it's inevitable that some of our religious students will ask "what is the proof for the existence of a god?" and it's inevitable that some of these students will not be happy with the stock religious answers to this question.

One of the things I've always tried to impress upon people on why they should be in a physics class, or learn about physics, isn't that they become experts in a particular area of physics. Rather, it is actually understanding how, and acquiring the skill of how, we arrive at a particular knowledge. The process of inquiry, and how we analyze if something is valid or not, is such an important but undervalued skill. We make decisions based on what we think are valid, yet many people do not realize that what they accept to be valid has not been clearly shown to be valid. In science classes, and especially in physics classes, these analytical sequence of investigation should be taught and shown explicitly, so that students can see how we arrive at a knowledge. It needs to be shown that if it cannot be done this way, then the conclusion that one draws is (i) may be faulty and (ii) not unique, i.e. there could be other conclusions to explain the same thing. The latter is clearly the case where religion is concerned since we have multiple religions in this world all vying to explain the same thing, and all claiming to be the 'truth'.

The greatest contribution to society out of science classes is to produce students that have the skill for analytical thinking. We need not have them become scientists. We only need to give them the ability to think logically and analyze "data" systematically.

Are you a science teacher? Have you been asked the same question?


Sunday, July 18, 2010

Physicists In Drag

A rather humorous blog at PhysicsCentral that did a take off on RuPaul's Drag Race. This time, the twist here is that the people that are dressed in drag are a few physicists that you might know - DOE Energy Secretary Steve Chu, living legend and theorist Steven Hawking, your physicist-next-door Albert Einstein, and the come-as-you-are extraordinaire, Isaac Newton.

I don't think Einstein ever looked that svelte!


Saturday, July 17, 2010

Physics Bachelor's Initial Employment

A while back I commented on the missed opportunity of an interview article of educating people on what one can do with an undergraduate physics degree. We can certainly provide a lot more detailed information than what was contained in that news article. And example came this week. The AIP has released the latest data on the initial employment of physics Bachelor degree holder based on a 2006/2007 survey. 39% were employed, 4% were still seeking employment, while the rest pursued graduate degrees.

The survey than broke down those who were employed into the various areas of employment. The largest were in the private sector (59%).

Physics bachelor’s working in the private sector accepted positions with a diverse set of employers doing a wide range of activities (see Figure 3). Over 70% of the physics bachelor’s who accepted employment in the private sector work in a STEM field. As has been true in the past, employment in the field of engineering represents the largest proportion of these private sector positions, followed by computer science and information technology positions. Non-STEM positions accounted for 29% of the new bachelor’s employed in the private sector. The types of positions in this category are very diverse, with "finance" and "marketing and sales" being most frequently cited.

This new statistics should give a lot more information on the various profession that a physics Bachelor degree holder has the potential of going into.


Friday, July 16, 2010

Much Ado About Topological Insulators

Topological Insulators are HOT. They are the hottest thing in condensed matter physics right now. This news summary from Nature describes what they are, and why they are the 'star' material at this moment (link open only for a limited time).

Those effects go beyond the way electrons move on the surface. For example, all electrons are spinning in a quantum mechanical way. Usually, the spins are constantly knocked about by random collisions and stray magnetic fields. But spinning electrons on the surface of a topological insulator are protected from disruption by quantum effects. This could make the materials beneficial for spin-related electronics, which would use the orientation of the electron spin to encode information, thereby opening up a whole new realm of computer technology.
Researchers also believe that the collective motions of electrons inside topological insulators will mimic several of the never-before-seen particles predicted by high-energy physicists. Among them are axions, hypothetical particles predicted in the 1970s; magnetic monopoles, single points of north and south magnetism; and Majorana particles — massless, chargeless entities that can serve as their own antiparticles.

This mimicry is not entirely surprising. Almost by definition, collective electron motions can be described by just a handful of variables obeying simple equations, says Frank Wilczek, a Nobel-prizewinning particle physicist at the Massachusetts Institute of Technology in Cambridge. "There are only a few kinds of equations that you can write down that are really simple," he says. So topological-insulator theorists and particle physicists have almost inevitably ended up in the same place.

In other words, once again, the physics that governs things in condensed matter now have implications into other areas that may be fundamental in nature! How many times have I indicated this already?

And since we're talking about topological insulators, don't miss the latest STM study on something similar that has produced quite an interesting result.


Thursday, July 15, 2010

Accelerators for America's Future

A new report coming out of the US Dept. of Energy reveals the importance of research in particle accelerators that is the engine that drives many advances. This report comes out of the DOE sponsored workshop on the very topic that was held last year.

Its purpose was to elicit the views and opinions of a wide range of accelerator users on the challenges and opportunities for developing and deploying accelerators to meet national needs. Some 300 of them attended the one-day symposium and poster session. In the two-day workshop that followed, 120 users of accelerator technology, from small business owners to well-known researchers, formed five working groups in Energy and Environment, Industry, Medicine, National Security and Discovery Science. Their charge was to give us their perspective on needs, challenges and areas of greatest promise; and to provide guidance on bridging the gap between accelerator research and technology deployment.

This report should clearly show the applications of a particle accelerator beyond just high energy physics. This is in addition to the very informative brochure produced by the APS-Physics a while back.


Wednesday, July 14, 2010

No Higgs.... YET!

I originally refused to report on this. Tommaso Dorigo "reported" another unconfirmed rumor (no, in this case, that is not redundant) that one of the light Higgs was detected either at CDF or D0 at the Tevatron. Of course, the various blogs and news agencies decided to report such speculative ramblings off someone's blog, and the whole internet was a buzz with this rumor. I refused to be suckered into reporting such a thing, considering that Dorigo has cried "wolf" before!

Word from Fermilab is that there is no such detection. So now all those various news agencies will print the official statement that there is no such discovery after all. What a waste of time, effort, and bandwidth!

When I read this, my jaw dropped wide open:

Dorigo has somewhat of a "boy who cried wolf" reputation among physicists, a reputation he embraces as healthy for science.

"Keeping particle physics in the press with hints of possible discoveries that later die out is more important than speaking loud and clear once in 10 years," he wrote in his blog.

This makes him the Paris Hilton of physics, because it appears that he cares more about being in the news than actually having anything of substance to say. And it is NOT true that keeping something in the news is better or more important than speaking loud and clear once in 10 years. If you continue to cry wolf often enough, the public will not only lose interest, but you lose CREDIBILITY. The health food industry is suffering from the same debacle, where almost every week or months, we get new reports on what's healthy and what's not. When people are bombarded with a constantly changing picture, they TUNE OUT. Is this not a possibility that Dorigo has ever considered? Of course not!

This is an irresponsible behavior. If it only reflects badly on him, I would have cared less. He could continue to ruin his credibility as much as he want. But this reflects badly on not only particle physics, but also physicists in general. Science, and definitely physics, cannot be done via speculation and rumors like this, especially when it gets into the public domain. Honest reporting of results, even if it is new, is one thing. Reporting 2nd or 3rd hand rumors is another. They are not the same thing, and doing the latter is utterly irresponsible.

But the problem here isn't just him. These various news agencies that do not seem to care that they are reporting a rumor that was reported on someone's personal blog, no less! The fact that they are using a source that had done this before AND shown to be unreliable is incredibly amazing. Have they lost all standards on having credible sources? Even if this turns out to be all true, that the Tevatron actually did produced Higgs, someone's blog would be the LAST place that a credible news agency should go to to get the news and confirmation. Am I being unreasonable here?

In the race to be the "first" to report things, we have lowered the quality of reporting and dismissed accuracy and replaced it for being fast. We don't care if something is accurate or not, let's just put it out there as soon as we can. This is a stupid and silly scenario.


Tuesday, July 13, 2010

Gravity Doesn't Exist - The Earth Really Sucks

I get tired of reading things like this, but hey, since it has gotten the attention of the NY Times, no less, it is fair game to report here.

Eric Verlinde's latest bombshell is now making the news in popular media. In it, he is claiming that gravity is merely an "illusion" (I hate that word).

But what if it’s all an illusion, a sort of cosmic frill, or a side effect of something else going on at deeper levels of reality?

So says Erik Verlinde, 48, a respected string theorist and professor of physics at the University of Amsterdam, whose contention that gravity is indeed an illusion has caused a continuing ruckus among physicists, or at least among those who profess to understand it. Reversing the logic of 300 years of science, he argued in a recent paper, titled “On the Origin of Gravity and the Laws of Newton,” that gravity is a consequence of the venerable laws of thermodynamics, which describe the behavior of heat and gases.

String theorists have abandoned publishing in peer-reviewed journals? Well, why not? They can make huge waves simply by putting their speculations on ArXiv and get in the news.

Edit: interestingly enough, there are already counter argument against Verlinde's proposal.


Monday, July 12, 2010

The Wonders of Physics

I mentioned this "show" before called "The Wonders of Physics" that had its beginnings in the Physics Dept. of the University of Wisconsin-Madison where I went to school (I won't say when!). This is a wonderful profile on Clint Sprott, the professor who had tirelessly started and continued to give presentation on this educational and entertaining show.

Clad in his signature tuxedo, J. Clint Sprott has a full house wowed with catchy visual demonstrations of waves, friction and Newton’s laws. In his show “The Wonders of Physics,” the University of Wisconsin–Madison professor emeritus of physics combines science and theatrics to show people how physics permeates everyday life.

If you get to see one of his shows, or catch the "road show", don't miss it. It will be thoroughly entertaining for the whole family.


Does Uniformly Accelerating Charge Radiate?

One would think that the simple answer to this is yes. However, a lot have been said and discussed (not to mention, published) on this problem. What appears to be a standard problem and treatment in Jackson's "Classical Electrodynamics" turns out to have a lot more to it than first meets the eye.

The latest discussion on this was published just a few days ago.

D.R. Rowland, Eur. J. Phys. v.31, p.1037.

Abstract: A core topic in graduate courses in electrodynamics is the description of radiation from an accelerated charge and the associated radiation reaction. However, contemporary papers still express a diversity of views on the question of whether or not a uniformly accelerating charge radiates suggesting that a complete physical understanding of the energy content of the fields surrounding an accelerating charge is still missing. It is argued in this paper that the missing insight is the precise physical meaning of the somewhat mysterious 'Schott energy' which is shown to be simply the difference between the energy in the bound electromagnetic fields of the accelerating charge and the amount of energy in the bound fields of a uniformly moving charge which has the same instantaneous velocity. This difference arises because the bound fields of a charge cannot respond 'rigidly' when the state of motion of a charge is changed by an external force. During uniform acceleration, the rate of change of this difference is just the negative of the rate at which radiation energy is created, and hence the power needed to accelerate a charged particle uniformly is just that which is required to accelerate a neutral particle with the same rest mass even though the charge is radiating. The errors in other analyses are also identified.

Published 9 July 2010

Note that you can get free access to the online paper within the first 30 days of online publication.


Saturday, July 10, 2010

The Physics of Smooth Balls

One could go in so many different directions with a title like that, but I'll play dumb right right now. :)

There have been many reports on the physics of soccer with the World Cup about to reach its climax (!) today (read this and this). So why not another one? This report discusses the differences between a smooth soccer ball versus one that is not.

“You might think if you make a ball very, very smooth, it will fly through the air better than a ball that is rough,” says John Eric Goff, chair of the physics department at Lynchburg College and author of Gold Medal Physics: The Science of Sports.

You might think that, but you’d be wrong.

“As the air goes around a sphere, or one of these sports balls, it forms a little layer near the surface of the sphere called the boundary layer,” says Goff. A rough surface makes that boundary layer break down at lower speeds.

“And what that means is the drag force on the ball, the air resistance, goes down slightly,” he says.

Now you know why a soccer ball has those "panels". Now, the issues with the Jabulani balls are a completely different matter.


Friday, July 09, 2010

Becoming A Successful PI

Er.. no, I don't mean "Private Investigator", but rather "Principal Investigator".

Saw this in the Physics Today blog, and it is a very good article. It is something every budding scientist/researcher should read on how to become a successful PI.


Thursday, July 08, 2010

New Measurement Shrinks The Size of Proton

The big news this week is the recently published paper in Nature[1] of the new size of the proton. Using a muonic hydrogen atom (a hydrogen atom where the electron has been replaced by a muon), a new Lamb shift measurement has produced a result of the size of a proton from 0.877 fm to 0.8418 fm.

Big deal, you say. But the implication of this can be quite astounding. The previous measurement was done based on the Lamb shift of a regular hydrogen atom. So the discrepancy (taking into account that the muon is heavier than the electron, etc.) may have a more profound effect, such as either the calculation is at fault, or that there may be a problem with QED itself.

There certainly could be hints of new physics here.


[1] R. Pohl et al., Nature v.466, p.213 (2010)

Wednesday, July 07, 2010

The Dark Matter of Gravitational Lensing

This is a good review article on the detection of dark matter via gravitational lensing.

R. Massey, T. Kitching, and J. Richard, Rep. Prog. Phys. v.73, p.086901 (2010).

Abstract: We review progress in understanding dark matter by astrophysics, and particularly via the effect of gravitational lensing. Evidences from many different directions now all imply that five sixths of the material content of the Universe is in this mysterious form, separate from and beyond the ordinary 'baryonic' particles in the standard model of particle physics. Dark matter appears not to interact via the electromagnetic force, and therefore neither emits nor reflects light. However, it definitely does interact via gravity, and has played the most important role in shaping the Universe on large scales. The most successful technique with which to investigate it has so far been the effect of gravitational lensing. The curvature of space–time near any gravitating mass (including dark matter) deflects passing rays of light—observably shifting, distorting and magnifying the images of background galaxies. Measurements of such effects currently provide constraints on the mean density of dark matter, and its density relative to baryonic matter; the size and mass of individual dark matter particles and its cross-section under various fundamental forces.

Online publication date: 8 July 2010

Remember that you can get access to the paper within 30 days after it appears online.


New Videos of Stimulating Physics Network

A couple of videos from the IoP on workshops held for teachers as part of the Stimulating Physics Network program. There are very simple demonstrations being taught for teachers to do to assist them in their physics teaching duties.


Tuesday, July 06, 2010

The Transformation of SLAC

The NY Times takes a closer look at the transformation of SLAC from a preeminent particle physics facility into a light source facility.

Four decades ago, the laboratory was arguably the preeminent particle physics laboratory in the world. In a straight tube two miles long, SLAC’s linear accelerator sped electrons to near the speed of light and slammed them together, generating insights into the smallest bits of matter.

In 1974, particles created at the accelerator confirmed the existence of the charm quark, an achievement that earned the team’s leader, Burton Richter, a Nobel Prize in Physics two years later. (Dr. Richter shared the honor with Samuel Ting of Brookhaven National Laboratory, which independently discovered the charm-containing particles at the same time.)

But higher energy accelerators were built elsewhere, and particle physics preeminence passed on, first to the Fermi National Accelerator Laboratory outside Chicago and now to CERN in Switzerland.

“We still are very strong in particle physics,” said Persis S. Drell, SLAC’s director, “but not like we were. We aren’t the center of the universe any more.”
The linear accelerator — the same one that discovered the charm quarks, now more than 40 years old — still accelerates electrons, but now as part of the X-ray laser. Instead of the electrons being directed onto a collision course at near-light speeds, they slalom through sinuous magnetic fields. As the electrons wiggle, they emit X-rays, and with precise wiggling, the X-rays coalesce into a laser beam.

It certainly is a drastic makeover of a very prestigious laboratory. The same type of fate, although not as drastic, may be faced by Fermilab with the Tevatron scheduled to reach its end in a year or two. While Project X may allow it to continue almost the way it is, the lab is also slowly transforming itself more into a neutrino source and research facility, which might be a brilliant move. With the ILC undergoing a slow death and almost on its last breath, the future of high energy physics experiment in the US faces a very uncertain future.


More on the LHC

CNET takes a look at the LHC. It does a respectable job at covering the complex experiment and facility aimed at a general audience. However, does it really have to start with this fallacy?

The theoretical physicists have had the upper hand for years, but something new has begun tilting the balance toward the experimentalists: the Large Hadron Collider.

It's as if physics is nothing more than particle/high energy physics! I don't recall theorists having the "upper hand for years" in condensed matter physics, accelerator physics, atomic/molecular physics, etc.. etc.


Monday, July 05, 2010

Another Sokal Hoax?

This is a rather fun (or frustrating) op-ed piece. The writer gave a good brief introduction to the infamous Sokal Hoax. This was done in context to a letter-to-the-editor that he came across which he humorously imagine as being Alan Sokal writing another of his hoax, but this time, as a letter to the editor.

All this came back to me the other day on reading the letters column of the simple daily newspaper I write for, the Arkansas Democrat Gazette, which is much too workaday to be confused with a highfalutin academic journal. This letter, too, seemed to view reality, facts, and all that objective folderol as a mere historical construct that needs to be brushed away so the young can be properly educated/indoctrinated. Or as the writer explained:

"Indeed, science is not an objective enterprise. It is greatly influenced by power, culture, race, gender and ethnicity. Biologist Ruth Hubbard says that facts are invented, not discovered; facts are not necessarily facts forever, as shown by the constant change in dogma in biology as new data are obtained."

Beautiful. This guff is still widespread, apparently, having spread far beyond the ivory tower, like so much smog. Two plus two equals four only because we’re told so. The germ theory of disease is but a philosophical construct. It all depends on what we’re taught, and since there are fashions in science as in all human endeavors, then science itself is only fashion — a culturally agreed-upon illusion, a bourgeois plot, as ever changeable as mere fact.


Of course, on the serious side of it, it is sad that there are now part of the general public that somehow holds that silly view. I often wonder if these people have ever done a proper science experiment. They don't realize that a subjective idea cannot make reproducible results consistently. This is one reason why many do not think that economics is a science. I often want to ask them to cite an example the last time they put their lives on something that is based on a subjective, social construct. After all, that's what they do everyday with science.


Sunday, July 04, 2010

The World Is Flat And the Answers Make It Flatter

I don't know what to make of this news article. It is also early in the morning on a Sunday after a late night, so my brain may not be functioning just yet. So I'll let you figure this out for yourself.

The news article describes the effort to educate middle-school teachers in trying to correct misconception that students have on a few issues with our physical world. This is a very good effort because what better way to discuss physics than to talk about things we understood either incorrectly, or for the wrong reasons.

Middle school students in Springfield and elsewhere are not receiving an adequate science education, says Robert A. Barkman, a Springfield College professor of biology and education.

Barkman has developed a program called “The World is Flat” to help middle school teachers learn how to identify students’ misconceptions about the physical sciences and then give them the tools to correct them.

But what caused me to wake up and rubbed my eyes were the answers given to some of the questions that were used to test people's understanding. The answers are not outright wrong, but they do raise some eyebrows. I'll tackle each one of them individually and see if you agree or disagree with me, or if I'm just being picky.

Many middle school students fail to answer these questions correctly.

Q. You drop two weights from the same height. Weight A weighs 10 lbs and weight B weighs 50 lbs, but they are identical in size and shape. Which will hit the ground first?

A. They both will fall at the same speed – the speed of gravity. Weight does not affect terminal velocity.

First of all, any physics student can tell you that the "speed of gravity" is either c, or not yet verified but theorized to be c.

Secondly, we kinda know what the answer is trying to convey, but really, does it have to be put in this manner? What it can and should say is that both objects (neglecting air resistance), will fall at the same ACCELERATION and will hit the ground at the same time. That is correct and accurate enough at this level.

Thirdly, since when is the terminal velocity not affected by the weight? Why is this even mentioned here since the original premise is that air resistance is negligible here? Very puzzling.

Q. You are at a playground in winter. You touch the ladder, which has wooden supports and metal rungs. Which material has a lower temperature?

A. They both have the same temperature. The metal rungs may feel colder, because they conduct heat better. They draw the heat from your hand away faster, so it feels colder, but if you measured them with a calorimeter, they would have the same temperature.

Er... the answer is correct, but how does one measure "temperature" with the simple calorimeter that are used in most schools? A calorimeter measures the amount of heat exchange, which involves the specific heat capacity of the object. So if you put the same volume of object (wooden and metal rungs) into a container of water, even if you have perfect insulation, the equilibrium temperature of the water at the end will be different for both. This is because the wood and the metal have different heat capacity.

Q. On planet Earth, an objects weighs 150 lbs and has a mass of 400 kg. On the moon, it weighs 140 lbs. What is its mass on the moon?

A. The same as it is on Earth. Weight is affected by gravity, but mass remains constant.

No problem here.

I'm not sure if the answers offered in the news article are the ones that were given to the teachers. I hope not, since, from the news article, it appears that the courses being given have more to do with self-discovery than being told what the answers are. So one would hope that the teachers discover the answers for themselves.


Friday, July 02, 2010

Power and Spin In Soccer

The soccer World Cup is drawing to its climax, so it is not too late to have another article on the physics of soccer. This is a nice, short, and concise article on such a subject.



Using Muons To Detect Hidden Nuclear Contraband

It is good timing that I had just mentioned about an unanticipated application of basic science, using the example of quantum spin leading to MRI. Chalk this one up to another such application. This time, it is the unanticipated application of elementary particle physics and its use in national security.

Here, muons are used to detect hidden material, such as metals that are denser and can typically be used to for nuclear equipment.

The device takes advantage of charged particles called muons, which are created in the atmosphere and zip through every square centimeter of material on Earth — human bodies and armored trucks alike — at a rate of one per minute.

“They sort of rain upon us like a light drizzle all the time,” Hohlmann said.

Despite their high energies, muons don’t interact very strongly with matter. “They can go through 6 to 8 feet of steel without being stopped,” Hohlmann said. “That’s nice for our application, because what we’re trying to do is look into things that are shielded.”

But though matter typically doesn’t stop muons in their tracks, heavy elements like uranium and metals like lead can deflect the charged particles. By tracking the muons’ paths, scientists can construct a 3-D image of whatever material got in their way.

So here's another example when someone asks you if research in high energy physics is a waste of time and money.

Edit: I found the link to the conference proceeding paper by the author mentioned in the Wired article. Not sure if it is open access, though.


Thursday, July 01, 2010

Fundamental Science and Improvement of the Quality of Life---Space Quantization to MRI

This is more of a presentation rather than an essay, but still, I think everyone can clearly get the message. It presents a compelling argument on why basic, pure science research is important, and in fact, is the "goose" that will lay the golden egg. It illustrates this by using the timeline in the development of the MRI technique that is so prevalent in medical sciences. It started with "... the quantum mechanical concept of space quantization and intrinsic spin... " that led to "... totally unanticipated practical improvements to the Quality of Life".

In fact, one can pluck the whole of QM and the whole of Special Relativity to show that back then, no one could anticipate what these two areas of study would bring. To me, the most effective means of countering these people who argue about the "waste of money" invested in basic sciences is to simply show several different chains of discoveries that started off with something rather innocuous and ended with an important practical application. Nothing falsifies a claim more definitively than showing a clear example like that. This is one this article has tried to do.