Hundreds of scientists and engineers are waiting with eager anticipation for SOI: Saturn Orbit Insertion, as the schoolbus-sized Cassini spacecraft races for its closest approach to the ringed planet tonight. Just before closest approach, Cassini will fire its main engine for 96 minutes to slow down the spacecraft and allow Saturn to capture it in orbit (see guide to SOI and diagram on the Cassini website). Right after the burn, for about 75 minutes, Cassini will be flying high over the rings at close range. The instruments will gather as many measurements and pictures as it can, because it will never again be this close to the rings or to Saturn. Scientists do not predict that the high-resolution cameras will be able to resolve individual ring particles from this range – the best resolution will be about 50 meters per pixel, and most particles are much smaller than 10 – but it may detect wakes, waves and streams that will provide clues to the dynamic evolution of ring particles over time. There should be good sample images of all three main rings, C, B, and A, as well as the narrow F ring. After downloading its data during the night, Cassini will point to Titan for its first of 45 encounters. Saturn has already provided Cassini’s instruments with a puzzle: the rotation rate appears to be slowing down. According to Cassini’s radio and plasma wave detectors, Saturn is rotating about 1% slower than when Voyager made measurements in 1981. (This is determined by timing radio pulses in the planet’s magnetic field, which is presumed to originate from deep within the fluid planet’s interior.) Jupiter’s rotation rate has been rock solid for 50 years of measurements, so why Saturn should show this change is without explanation at this time. The principal investigator for the radio and plasma wave instrument suspects it has something to do with the fact that Saturn’s polar and magnetic field axes are almost perfectly aligned, to within 0.2 degree – a characteristic unique to Saturn. All other planets with magnetic fields show an offset of 10 degrees or more. It is that offset that generates the magnetic dynamo, according to favored models; these models, however, cannot account for a field on an axisymmetric body. How Saturn can have a magnetic field with a negligible offset is a major puzzle Cassini scientists hope to solve.Update Stupendous success! The orbit insertion burn occurred flawlessly. Cassini followed its trajectory exactly as predicted, and then turned to capture the data and images. Relieved scientists and engineers expressed their enthusiasm at the performance of the spacecraft. Now the four-year adventure begins. Some of the first science results will be posted in the July issue as soon as available.We hope to be able to bring you findings and analyses that the media will miss or misinterpret. For instance, the media will always interpret phenomena in terms of the Sacred Parameter A, the “age of the solar system” (4.5 billion years), a figure invariably assumed without question, even when apparently young phenomena are being observed. Of special interest will be the rings, not only because of their beauty, but because of their apparent youth. Most ring scientists believe that the rings had to form relatively recently. Even if 100 million years were allowed, that would only be 1/50 of the Sacred Parameter. To hold onto A, they have to invoke ad hoc theories of a comet wandering into the Roche Limit of Saturn and disrupting. Even so, the forces of plasma drag, sputtering, micrometeorite bombardment, light pressure and collisions would dissipate the rings in short order. Will embedded moons be found to feed new material into the rings? Stay tuned. Also, we will provide balance to the claims about Titan having “prebiotic chemistry” that might be like the “building blocks of life” or like the “early earth in deep freeze.” One scientist was even heard suggesting that Titan’s atmosphere may be a natural laboratory for the Miller Experiment (see 05/02/2003 headline). Such statements assume evolution in spite of the evidence. Also, it will be interesting to see if long-age believers can rescue Titan’s atmosphere from the evidence it is depleting rapidly (see 10/16/2003 headline). Cassini is poised to make major contributions to our understanding of the solar system and its age. For now, enjoy the ride; it will be high adventure tonight at Saturn!(Visited 11 times, 1 visits today)FacebookTwitterPinterestSave分享0
Light-emitting diodes (LEDs) were a prized invention of physicists, improved greatly in 2001, but now we find butterflies invented them first. We already knew that butterfly wings achieve their shimmering iridescence by means of photonic crystals (01/29/2003), as do some birds (10/13/2003), but now it appears that the butterflies have even more exotic tricks up their sleeves: they have true LEDs. Pete Vukusic of Exeter and Ian Hooper of MIT were startled to see the wings of African swallowtails shine super-bright under ultraviolet light. They reported in Science this week that the photonic crystals absorb UV and re-radiate it in a blue-green portion of the visible spectrum where the butterfly’s eye is particularly sensitive. Not only that, the photonic crystals are shaped in a cylindrical way to prevent side-scattering, are spaced for maximum effect, and contain reflective surfaces to focus the light straight out of the tubular shafts. This makes them “all but identical in design to the LED,” said Vukusic. Being able to emit powerful light without a semiconductor or power source makes the feat “doubly efficient in a way,” he said. It’s not just an analogy calling this structure an LED, he explained – that is really how it works. The researchers feel that their results will help engineers improve manmade devices. “When you study these things and get a feel for the photonic architecture available, you really start to appreciate the elegance with which nature put some of these things together,” he said. Sources: BBC News, MSNBC, LiveScience and [email protected] was little mention of evolution in any of the papers, except that the BBC article stated that the butterflies “had been using this method for 30 million years,” and [email protected] mentioned in passing that the system had “evolved to direct the emitted light outwards” without venturing to say how. All the evolutionists seemed so amazed that a butterfly figured this out. Even Ker Than, Mr. Dogmatic Darwinist and ID-Basher, didn’t dare speculate about how this precision optical system evolved. To top that, Nature, that Darwinese foghorn, actually subtitled their piece, “Butterflies shine brighter by design.” Cowabunga! Are they beginning to see the light? Think about the fact that a butterfly goes through an egg, caterpillar, and chrysalis stage. In that last stage, all its guts are transformed into precision LEDs, flight software and hardware, vision, incredibly-sensitive olfactory systems and much, much more. Kids should get out with their butterfly nets and learn some creation science like they always have. Only now, they should learn some physics and optical electronics, too. Sounds like some good Science Fair material here.(Visited 15 times, 1 visits today)FacebookTwitterPinterestSave分享0
Drinking water systems serving 19 million Americans are contaminated with highly toxic chemical compounds called PFAS as the number of locations where pollution has been found continues to grow, according to a new report from the Environmental Working Group. As of March, at least 610 locations in 43 states were known to be affected, including water systems, military bases, airports, and firefighting training sites. When last updated in July 2018, the list included 172 sites in 40 states, less than one-third the total of the most recent total. Linked to a variety of health issues, the chemicals are perfluoroalkyl and polyfluoroalkyl, manufactured since the 1940s and used in a variety of consumer products including non-stick pots and pans, food packaging, firefighting foam, and waterproof clothing.RELATED ARTICLESCoal-Fired Power Plants Are Polluting Groundwater: AnalysisIs Your Drinking Water Safe?Should You Worry About PFOA in Your Water?Nitrate Taints Drinking Water of Millions, Study FindsThe Takeover of the EPA The information has been compiled on an interactive map by EWG, a nonprofit environmental advocacy group headquartered in Washington, D.C., and the Social Science Environmental Health Research Institute at Northwestern University. EWG said the new list draws on data from the federal Safe Drinking Water Information System, the Department of Defense, and from news reports collected by Northwestern. The U.S. Environmental Protection Agency phased out some types of PFAS once used in products like Scotchgard and Teflon, called PFOA and PFOS, when they were linked to cancer, thyroid disease, and other health issues, EWG said. Those compounds were replaced by PFAS with slightly different chemical makeups that were not adequately tested for safety before they went on the market, the group said, and they now can be found in the blood of virtually all Americans. Michigan appears to be the unlucky winner with the most known pollution sites, 192 in all. California is next with 47, and then New Jersey with 43. Impact on drinking water is only a guess EWG’s report estimates that the drinking water of 19 million people might be compromised but acknowledges that’s only a guess. Although public water systems know how many homes and businesses they serve, they don’t necessarily know how many people live or work there. The total, however, could be much higher. “An EWG analysis of unreleased EPA test data estimated that more than 1,500 drinking water systems, serving up to 110 million Americans, may be contaminated with PFAS chemicals,” the report says. According to the EPA, the chemicals are found just about everywhere — in food packaged with materials that contain PFAS, in stain-resistant and water-resistant fabrics, waxes, paints, in the workplace, and in living organisms. PFOA and PFOS are both “very persistent” in the environment and in the human body, the EPA says, and because they don’t break down they can accumulate over time. In February, the EPA announced an action plan for dealing with PFAS. Among the steps the agency said it would take were developing a “maximum contaminant level” for PFOA and PFOS, making interim groundwater cleanup recommendations, and expanding scientific research. EWG said that the EPA’s approach would only make the problem worse because it did not stop the introduction of new PFAS chemicals, end the use of PFAS in products that many Americans use, or clean up contaminated water supplies. Scott Faber, the senior vice president for government affairs at EWG, said, “Once again, Donald Trump has demonstrated that he is the nation’s first pro-cancer president.” EPA says that the new map could be misleading After reporting on EWG’s new survey, the Huffington Post received a statement from the EPA saying the map showing PFAS pollution sites could be misleading. “Because EPA has not fully reviewed the quality of the underlying data, and based on the agency’s commitment to good risk communication with the public, EPA cannot recommend the map be used to determine where public health risks associated with PFAS chemicals may or may not exist,” the statement said. The agency pointed to a health advisory for PFOA and PFOS of 70 parts per trillion that it issued in 2016 and said its “robust efforts” were reflected in its action plan. Legislation introduced in the U.S. House of Representatives last month would force the EPA to set legal limits on PFAS in drinking water within two years, a step the EPA’s action plan did not include.
The sales process is not linear. It is dynamic. We need to rethink the sales proccess to account for the dynmaic nature of human interactions.