Feb
27
Posted by jns on
February 27, 2009
Conservation of Energy and the Second Law of Thermodynamics are probably the two most important concepts in physics that have thwarted the aspirations and claims of inventors and charlatans for decades. Someday we hope that the public will understand this.
WEIGHT-LOSS: SCIENCE CONFIRMS THE “PHYSICS PLAN“.
Atkins, Pritikin, Jennie Craig, South Beach, NutriSystem . . . all had one thing in common: they made their inventors very rich. But how could it be that every diet plan seems to work? It’s nothing but consciousness-raising; any plan will make people aware of how much they’re shoveling in. Nine years ago, however, WN came out with the “physics plan.” The plan is based on the Conservation of Energy: “burn more calories than you consume” http://www.bobpark.org/WN00/wn022500.html. Don’t be fooled by cheap imitations. On Wednesday, the New England Journal of Medicine published the results of a two year study of 800 overweight adults. Headed by Frank Sacks of the Harvard School of Public Health, the study confirmed that people lose weight if they cut calories; it doesn’t matter if the calories are fat, carbohydrates, or protein. That, of course, is the WN “physics plan.”
[Robert L. Park, What's New, 27 February 2009.]
Feb
16
Posted by jns on
February 16, 2009
SpaceWeather.com (operated by NOAA) reports that people all over the US are seeing meteors and are concerned that it’s space debris from that dramatic orbital collision between Iridium 33 and Kosmos 2251. Apparently there was also a large meteor seen over Italy that led to similar thoughts.
I’ve also seen reports that the FAA has warned pilots to be on the lookout for space debris, although it’s not clear to me what they’re supposed to do if they see some streaking by except get hysterical.
It’s easy to understand why people will have this reaction, so it’s also useful to note that meteoroids and space debris enter the atmosphere in different–and distinguishable–ways.
Anyway, here is what Spaceweather (for 16 February 2009) had to say about those fireballs:
WEEKEND FIREBALLS: A daylight fireball over Texas on Sunday, Feb. 15th, triggered widespread reports that debris from a recent satellite collision was falling to Earth. Those reports were premature. Researchers have studied video of the event and concluded that the object was more likely a natural meteoroid about one meter wide traveling more than 20 km/s–much faster than orbital debris. Meteoroids hit Earth every day, and the Texas fireball was apparently one of them.
There’s more: On Friday, Feb. 13th, people in central Kentucky heard loud booms, felt their houses shake, and saw a fireball streaking through the sky. This occurred scant hours after another fireball at least 10 times brighter than a full Moon lit up the sky over Italy. Although it is tempting to attribute these events to debris from the Feb. 10th collision of the Iridium 33 and Kosmos 2251 satellites, the Kentucky and Italy fireballs also seem to be meteoroids, not manmade objects. Italian scientists are studying the ground track of their fireball, which was recorded by multiple cameras, and they will soon begin to hunt for meteorites.
Videos, eye-witness reports and more information about these events may be found at http://spaceweather.com.
Feb
10
Posted by jns on
February 10, 2009
Still in operation, NASA’s SOHO (Solar and Heliophysical Observatory) spacecraft orbits the sun (not the Earth)
in step with the Earth, by slowly orbiting around the First Lagrangian Point (L1), where the combined gravity of the Earth and Sun keep SOHO in an orbit locked to the Earth-Sun line. The L1 point is approximately 1.5 million kilometers away from Earth (about four times the distance of the Moon), in the direction of the Sun. There, SOHO enjoys an uninterrupted view of our daylight star. (source)
One of the instruments on board is the Coronal Diagnostic Spectrometer (CDS), which was designed to study the atmosphere of the sun spectroscopically,* i.e., to look at characteristic wavelengths in the light put out by the corona, from which one can deduce quite a bit about the physical processes going on there.
On 26 March 2002 the CDS took a “quiet-sun” spectrum of the corona (meaning there were no particular disturbances, solar flares, or coronal discharges going on, just a normal, quiescent (such as it is) solar atmosphere. Below is the spectrum (shown one half above the other). The spectrum was taken in the extreme ultraviolet (EUV), so this red is dramatic false coloring. There are quite a few spectral lines visible, demonstrating the range and resolution of the CDS.
Evidently I am not the only one who thinks this spectrum is quite beautiful. It seems that the designers of this natatorium also thought so.
According to the
SOHO page where I found this photograph, the
mosaic is 20 meters long and constructed out of some 50,000 Italian glass tiles.
I want one.
———-
* Here is the official description of the CDS. It’s like scientific pornography for us experimentalists. Just let the words flow over you:
CDS consists of a Wolter II grazing incidence telescope which has a focus at a slit assembly which lies beyond a scan mirror. Light stops define two telescope apertures which feed, simultaneously into two spectrometers beyond the slit assembly. One portion of the beam hits a grating in grazing incidence and the spectrum is dispersed onto four 1-D detectors placed around the Rowland circle. This is the grazing incidence spectrometer or GIS. The other portion is fed through to a twin grating in normal incidence and the resulting spectrum is viewed by a 2-D detector system. This is the normal incidence spectrometer or NIS.
The GIS grating is spherical. The system is astigmatic, i.e. there is no spatial focus. Thus, one would use “pinhole” or square slits and build up images by rastering in two directions over the Sun’s surface. The rastering is performed by rotating the scan mirror (E-W rastering; i.e. by presenting different portions of the Sun to the slit) and by scanning the slit (N-S rastering). The four detectors sit at specified, fixed locations around the Rowland circle and thus detect the EUV spectrum in four fixed wavelength ranges.
The NIS gratings are toroidal, resulting in a stigmatic system. Thus, we may use long, thin slits and can image, spatially along the slits. Images of the slit are dispersed on the NIS detector producing an image, effectively, of wavelength against a spatial dimension. As a result, one can produce rastered images very quickly by rastering in only one dimension with the scan mirror. Since the NIS spectrum is dispersed by two gratings, slightly angled with respect to one another, two spectral ranges are viewed on the one 2-D detector.
Feb
09
Posted by jns on
February 9, 2009
This is birthday boy Charles Robert Darwin (1809-1882), born 200 years ago on 12 February 1809. This photograph (which I have cropped) was taken in 1882 by the photographic company of Ernest Edwards, London.*
Many people call Darwin’s great idea, common descent through evolution by means of natural selection, the greatest scientific discovery ever. Maybe. It’s certainly big. My hesitation is merely a reflection of my feeling that it’s really difficult to prioritize the great ideas and discoveries of science and math into a hierarchy that would assign the top position to one idea alone. No doubt it’s the over cautious precision of my inner scientist asserting itself.
Almost since the pages of Origin of Species were first sewn into a book there has been a cottage industry of trying to “disprove Darwin”. So strongly associated is his name with the big idea that “Darwin” and “Darwinism” serve as effigies for those who revile the idea so much that they expend considerable energy looking for anything that might weaken the authority of the idea so that it can be toppled from its scientific pantheon.
Unfortunately for their efforts, they sorely misunderstand how science works and, therefore, how futile their efforts are. Detractors seem to believe they are operating under junior debating-society rules where locating any hint of a logical inconsistency in the “theory”, or any modern deviation from what they think is Darwinian orthodoxy, is certain to be a fatal blow to the hated “theory”. Alas, they hope to disprove Darwin but can only disapprove and look silly and naive.
The biggest impediment to tearing down the edifice of “Darwinism”, of course, is reality. Scientists believe that reality has a separate, objective existence that affords no special place to humans. One corollary to this is that objective reality is what it is regardless of our most fervent desires, regardless of our prayers to a supernatural deity to change it, regardless of the stories we tell ourselves over and over about how we would like it to be. Deny reality for your own psychological benefit as needs must, but you will not alter reality by doing so.†
But, suppose there are chinks in the armor of “Darwinism”–isn’t that fatal? Well, no. Great ideas that flow into the vast river of science stay if they are useful ideas. Depending on utility they may change, grow, even evolve over time, but they’re frequently treated as the same idea. Creators do not have veto power over how their scientific ideas are used, nor how they are changed or updated, although they continue to get the credit for great ideas. The way we understand and describe gravity is nothing recognizable to Newton, but he continues to get credit as the discoverer of “universal gravitation”.
But aren’t wrong theories, those that have been “disproven” by logical errors or deviations from precise descriptions of reality, immediately discarded as useless? Oh no, far from it. See the aforementioned Newtonian theory of gravity for but one ready example.‡
This is the trade-off: a somewhat inaccurate (or “wrong”) but productive theory is of far more use to science than a correct but sterile idea. By “productive” I refer to ideas that lead one to new ideas, new experiments, and new understandings. Compare that notion with what some would have you believe is the undeniable perfection of revealed truth from a divine creator: it is an investigative dead end, it leads to no new ideas whatsoever, it affords no solution beyond the parental disclaimer, “because”.
“Why” is the path science follows, not “because”. I believe that “why” is the more interesting and the more valuable path to follow, at least when it comes to understanding how the universe works. One may feel free to disagree on its value and utility, of course, but denying its reality is futile.
———-
* The photograph is part of the wonderful collection of “Portraits of Scientists and Inventors” from the Smithsonian Institution, which we have sampled here before and undoubtedly will again and again, photographs they have contributed to the Flickr Commons Project. (The Flickr page; the persistent URL)
† This is probably the source of the calm, know-it-all demeanor that atheists tend to exhibit, and that so inflames those who would consign us prematurely to the flames of hell: all the evidence we see about how the world really operates fails to suggest that a creator-deity exists–not to mention a personal-coach-deity–and no amount of wishful thinking can change reality.
‡ Sometime we’ll talk about the contingent nature of scientific “truth” and how uncomfortable that idea is for those with an absolutist predilection.