Archive for January, 2010

Keep it Simple, Stupid

The KISS principle was something I was introduced to when I was training to be an instructor for the navy. Someone asks a question, and you shouldn’t get bogged down in unnecessary detail in answering it, or in explaining a concept.

A couple of Chad’s recent posts touch on the theme of explaining physics to the non-physicist. The first is The Popular Science Writing Process, in which he discusses the interaction with the editor:

Get back an edit letter saying “AAAAAAAHHHH!!! Much too difficult! Make it simpler!”

and in Continuity, Discretion, and the Perils of Popularization there is a lengthy discussion of a previous post on QM basics concepts

Last week’s Seven Essential Elements of Quantum Physics post sparked a fair bit of discussion, though most of it was at the expert level, well above the level of the intended audience. such is life in the physics blogosphere.

And this isn’t the first time this has happened; I recall an earlier exchange about the photon that went many layers deep in the discussion as well. The underlying theme here is that one needs to know the audience to whom you are speaking — the advantage of the editor saying “Ensimplify!” is that if s/he is not an expert in the field, and if the book is targeted at the general reader, the editor is probably a decent proxy for that audience. It would not do as much good to hand the book to a fellow physicist for the same kind of critique, because you’re likely to get the kind of objection that shows up in the Perils post. Some scientists have difficulty connecting with an audience that isn’t up to the same level of expertise; they won’t simplify their discussions. But here’s the thing:

All explanations are incomplete.

Incomplete is not necessarily the same as wrong.

We always assume some level of knowledge on the part of our listeners. It helps to know what that is, because you can miss and either go way over their heads or sound patronizing. But the goal in such situations is not to disseminate some complete set of information. To do that you might have to be explaining vector calculus and field theory, so that’s just not going to happen. It’s more important that whatever information you communicate, that it not be wrong. I think it’s very important to decouple the two concepts of completeness and correctness.

And it shouldn’t be that hard to do. If you think they are entwined, then you have to admit that teachers lie to their students all the time. We teach first-semester physics and tell our students that kinetic energy is 1/2 mv^2, and anyone who has taken relativity knows that that is just an approximation. But is it useful to throw relativity at first-semester physics students? No. The basic concepts are difficult enough. And everybody uses 1/2 mv^2, and other approximations, when circumstances say it’s OK to do so. Expanding some expression in a Taylor series to get an answer is a major part of physics, and we don’t consider it wrong as long as x << a. We use Newtonian gravity in many instances, because General Relativity need not be invoked. (Both of these being incomplete, but not wrong, if properly applied) We can explain that an atom won’t absorb a photon unless it matches the energy of an allowed transition without worrying about energy level linewidths, if that part of the discussion isn’t important to the conversation.

So I think that thinking has to be applied to explaining science to nonscientists, or to less-experienced scientists. If all they can handle is the first term in the expansion, then give that to them, and explain things at that level. I think not propagating falsehoods is more important than being precisely right.

I see this at work; we show off our handiwork on occasion, and to people who don’t have the background we do. A full quantum-mechanical discussion of atomic clocks just isn’t very pragmatic unless you actually want to bore or disillusion your audience. (if they represent possible funding, that’s usually a “No, let’s not do that.”) So you have to give the talk that’s technically correct but doesn’t go into graduate-level detail or beyond, unless your target actually invites that level of detail. And my immediate colleagues and I aren’t the only ones who like to brag about our work or hint loudly about the work we’d like to be doing in the future. But the other people who “sell” our accomplishments aren’t atomic physicists either, so there’s the same issue: give them bullet points that aren’t wrong, and don’t get bogged down in extraneous scientific detail.

See also Skulls in the Stars: To describe, or not to describe…

Nothing to do with MiB

The Kaye Effect

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Present in shear-thinning fluids — when pouring it into a reservoir, a jet of fluid will occasionally emerge.

There’s an especially neat part at the end where the fluid is used as a light guide.


‘Superman’ vision penetrates opaque glass

It’s not quite X-ray vision, but a way has been found to transmit simple images through opaque objects using ordinary light – and physicists have used the method to project an image through glass covered in thick paint.

By reverse engineering the scattering process, the team were able to reconstruct an image from the light that had passed through the opaque paint layer. That scattering is complex, but it’s also predictable: the same light wave will always be scattered in the same way.

ArXiv paper.

Friend Me

The Oatmeal: How to Suck at Facebook

I joined facebook about a year ago. After the initial rush was over, I find I visit ~monthly.

The last panel is one reason why I fear twitter. I imagine feeds like

need more fiber in my diet

scratching my butt. feelin’ good.

Some things just don’t need to be shared

Is it Getting Crowded in Here?

Initial NIF experiments meet requirements for fusion ignition

The experiments, described in an article in today’s edition of Science Express, the online version of the journal Science, resulted in highly symmetrical compression of simulated fuel capsules – a requirement for NIF to achieve its goal of fusion ignition and energy gain when ignition experiments begin later this year.

The test shots proved NIF’s ability to deliver sufficient energy to the hohlraum to reach the radiation temperatures – more than 3 million degrees Centigrade – needed to create the intense bath of X-rays that compress the fuel capsule. When NIF scientists extrapolate the results of the initial experiments to higher-energy shots on full-sized hohlraums, “we feel we will be able to create the necessary hohlraum conditions to drive an implosion to ignition,” said Jeff Atherton, director of NIF experiments.

Don't Send Me a Postcard

More virtual vacation visits. 360º Panoramic view from Mt. Everest

The Great Wall


Machu Picchu – Peru

Of Cranks and Crackpots and Sealing Wax

How I found glaring errors in Einstein’s calculations

Or rather, I have not, but I know lots of people who have. For some time now, I have been an avid reader and collector of webpages created by crackpot physicists, those marginal self-styled scientists whose foundational, generally revolutionary work is sadly ignored by most established scientists. These are the great heroes, at least in their own eyes, of alternative science. In pre-Internet ages, these people routinely sent sheaves of notes and articles to established physicists and mathematicians, warning them that the papers contained proofs of Goldbach’s conjecture or Fermat’s theorem, or revolutionary models of gravitation and the atom. Scientists would just as routinely consign all this brilliant stuff to the wastepaper basket.

But then a miracle happened – CERN and DARPA created the Internet… and crackpots now all have their webpages! The whole world can benefit from exposure to alternative science.

Some interesting observations, including “The crackpot theory is based on textbooks,” i.e. crackpots tend to focus only on the “big examples” given in textbooks (e.g. Michelson-Morley for relativity)

As I said, crackpots are all committed to the principles of sound science – and they have done their homework. So where did it all go wrong? The textbook problem is in my view the crucial clue. Crackpots devote entire sites to discussing the Michelson-Morley experiment. To most physicists, such discussions are largely irrelevant, as these classic experiments were only the first ones in a long series of tests that showed the complete agreement between observations and predictions from special relativity. Also, the crackpots are generally not aware that every day, in thousands of labs all over the world, people are performing experiments that require special relativity, and that these experiments turn out all right because relativistic principles are included in people’s computations.

One thing this treatise ignores is the slice of psychoceramics that have no math skillz whatsoever. These are invariably in the “my theory is intuitive” crowd, and they post lots of pretty pictures about their helical, or möbius, or toroidal electrons, and how everything is really one particle — all you have to do is put another “twist” in the loop, or take it away, and you’ve got a proton or a photon. These are often folks who want to explain what energy is, or mass is, or some other metaphysical theme, rather than how things behave in nature, which is what scientists are after.

Update: in addition to Ian’s link in the comments, Bee just wrote something up on Backreaction. Division by Zero

Smoke but no Mirrors

Optical Trapping and the Momentum of Light

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The explanation talks about the wave-particle duality, but I think that’s a distraction. This is a dipole force phenomenon; the beam’s intensity is greatest at the center, and where the focal point occurs, as shown in the drawing at the end of the post. This gives rise to a gradient in the electric field. If you put a dielectric particle in this region, it will feel a force in the direction of the field maximum, or toward the highest intensity of light.

Sometimes Mundane is Interesting

Mundane examples of energy at the Hamiltonian Function.

The energy of walking up a hill.

Say Hello to my Little Friend

My new sofa with recliner capability. It was delivered last week, in time for the playoff games this past weekend.


I did love my old sofa, but after 20 years of putting up with me the springs and frame were shot.

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