FreThink

From ScienceNewsOnline:

Call it Murphy’s Law of knots: If something can get tangled up, it will. “Anything that’s long and flexible seems to somehow end up knotted,” says Andrew Belmonte, an applied mathematician at Pennsylvania State University in University Park. Belmonte has plenty of alarming anecdotal evidence. “It certainly happens in my house, with the cords of the venetian blind.” But the knot scourge is a global one, as anyone who owns a desktop computer can confirm after peeking at the mess of connection cables and power cords behind the desk.

Now, scientists think they may have found out how and why things find their way into knotty arrangements. By tumbling a string of rope inside a box, biophysicists Dorian Raymer and Douglas Smith have discovered that knots—even complex knots—form surprisingly fast and often. The string first coils up, and then its free ends swivel around the other coils, tracing a random path among them. That essentially makes the coils into a braid, producing knots, the scientists say.

The results’ relevance may go well beyond explaining the epidemic of tangled venetian blind cords. That’s because spontaneous knots seem to be prevalent in nature, especially in biological molecules. For example, knottiness may be crucial to the workings of certain proteins (see “Knots in Proteins”). And knots can randomly form in DNA, hampering duplication or gene expression—so much so that living cells deploy special knot-chopping enzymes.

But even if Raymer and Smith’s results don’t prove to be directly relevant to the molecules of life, they are “a very good beginning” for a general study of physical knots, according to Belmonte. “Now we can at least ask these questions: Are there universal laws of knots?”

I find knots fascinating.  Chaotic systems tend to boggle the mind, and having your mind boggled now and then keeps it well exercised.  Another chaotic state that often frustrates scientists is turbulence.

A report from USA Today:

Turbulence does more than toss around luggage on airplanes and spill coffee on traveler’s laps — it confuses the heck out of scientists. A new experiment may suggest why — fluid dynamicists may have been missing something fundamental about turbulence for a good long time.

Renowned physicist Richard Feynman called turbulence the most important unsolved problem of classical physics, the body of engineering knowledge stretching roughly from Archimedes to Einstein. No one really understands precisely how the flow of gas or liquids transitions from smooth flow to choppy turbulence (not even something as simple as the point at which water from your tap goes from a smooth, or laminar, translucence to burbling foam.)

This drives engineers nuts (I can attest to this as a former engineer) because turbulence disrupts and drags air, gas and liquids that flow in and on everything from pipelines to airplane wings to artificial heart valves — all the apparatus of an industrial society — in ways both costly and unpredictable. To take just one example, turbulence costs U.S. airlines an annual $100 million due to injuries and delays, according to the National Center for Atmospheric Research’s estimates.

Naturally, we do know some things about turbulence, observations that pertain to air, gas and liquids alike. “Generally, the motion of fluids is smooth and laminar at low speeds but becomes highly disordered and turbulent as the velocity increases,” notes a paper by a physics team led by Bjorn Hof of the United Kingdom’s University of Manchester in the current Nature. After making the full-fledged transition from smooth to turbulent flow, the paper adds, “it is generally assumed that, under steady conditions, the turbulent state will persist indefinitely.”

Whoops, maybe not. Experiments described by Hof’s team suggests that assumption may be wrong. The finding in fact suggests that turbulence may be reversible, contradicting decades of engineering dogma, and offering unexpected insight into how turbulence works.

The team looked at turbulence in an pipe nearly 100 feet long with an internal diameter of about 0.16 inches, allowing for turbulence observation times about 10 times longer than those undertaken by any other lab facility, the team contends. By injecting water into water flowing down the pipe to create “turbulent puffs,” the team attempted to measure whether turbulence persisted under different flow conditions. Turbulence cuts the speed of the water flowing out of the center of the pipe about 30% while increasing flow speed on the pipe’s walls, so that water flowing smoothly out of the pipe emerges with a differently-shaped jet than turbulent flow, making the measurements easy.

“In contrast to previous findings,” the team found that turbulence in the pipe always returned to smooth flows, if one waited long enough. The finding suggests that rather than turbulence obliterating smooth flow, fluids somehow retain the ability to reorganize themselves back into a regular pattern.

“This is a conceptual shift and a very intriguing one,” says mechanical engineer Charles Meneveau of the Turbulence Research Group at Johns Hopkins University in Baltimore. “There are big implications for control of pipe flow,” he says, cautioning that the results must now be confirmed by other researchers.

Let’s focus on that last sentence for a moment.  This is what separates scientific inquiry from religious belief; postulations in science are either confirmed or dismissed by other scientists conducting their own experiments, and those findings are tested, as are those findings.  Contrary evidence can derail a promising hypothesis.  In religion, evidence is “faith” based and purely personal.  Lack of evidence is dismissed, and nothing is presented that can be verified empirically.

I hope these articles get your new year started with an exercised brain.