Bird flight, new research


This video says about itself:

5 December 2016

Using a high-speed camera, scientists captured the swirling vortices produced by a slowly flying bird. Surprisingly, they found that the vortices rapidly dissipated. The unexpected effect suggests that scientists need to rethink methods for calculating the lift produced under such conditions.

From Science News:

Bird plus goggles equals new insight into flight physics

Unexpected vortices form in parrotlet’s wing wake

By Emily Conover

6:21pm, December 5, 2016

A bird in laser goggles has helped scientists discover a new phenomenon in the physics of flight.

Swirling vortices appear in the flow of air that follows a bird’s wingbeat. But for slowly flying birds, these vortices were unexpectedly short-lived, researchers from Stanford University report December 6 in Bioinspiration and Biomimetics. The results could help scientists better understand how animals fly, and could be important for designing flying robots (SN: 2/7/15, p. 18).

To study the complex air currents produced by birds’ flapping wings, the researchers trained a Pacific parrotlet, a small species of parrot, to fly through laser light — with the appropriate eye protection, of course. Study coauthor Eric Gutierrez, who recently graduated from Stanford, built tiny, 3-D‒printed laser goggles for the bird, named Obi.

Gutierrez and colleagues tracked the air currents left in Obi’s wake by spraying a fine liquid mist in the air, and illuminating it with a laser spread out into a two-dimensional sheet. High-speed cameras recorded the action at 1,000 frames per second.

The vortex produced by the bird “explosively breaks up,” says mechanical engineer David Lentink, a coauthor of the study. “The flow becomes very complex, much more turbulent.” Comparing three standard methods for calculating the lift produced by flapping wings showed that predictions didn’t match reality, thanks to the unexpected vortex breakup.

No new blog posts, will re-start soon!


This video says about itself:

Physics of Bird Migration

It is spring and we went to check out the migratory birds returning from their winter grounds. It is pretty incredible to think that some of them have crossed deserts and oceans on their journeys, and they still manage to find their way back to the same locations every year.

For example, did you know that the Arctic Tern is the World Record holder when it comes to migration amongst birds? It spends Northern Hemisphere summers in the Arctic and then for winter it flies all the way to the Antarctic!

Absolutely crazy to think that in one year it has seen more of the world than most of us will in a lifetime. In this week’s video we take a look at the physics behind a few of the adaptations that the birds have evolved to be able to perform these annual migrations. Enjoy!

Produced by: Jonas Stenstrom

Filming help by: Louise Fornander & John-Mehdi Ghaddas

For about a week, there will no new blog posts on Dear Kitty. Some blog.

Then, the blog will re-start with lots of inspiration about, eg, the migratory season for birds (autumn migration in this case); and many other subjects, as usually.

So, see you all again soon!

American religious fundamentalist threatened to murder scientist Stephen Hawking


This video says about itself:

24 September 2014

The renowned physicist Stephen Hawking has labeled himself as an atheist, clearly stating that he doesn’t believe God exists at all.

Hawking reportedly made the announcement in an interview at the start of the Starmus Festival taking place at Tenerife in the Canary Islands.

El Mundo, a Spanish newspaper, was able to get an exclusive interview with Hawking and headlined the story with the scientist’s statement about his beliefs.

Hawking is quoted in the interview saying: “What I meant by ‘we would know the mind of God’ is, we would know everything that God would know, if there were a God, which there isn’t. I’m an atheist.”

But this isn’t the first time that Hawking has mentioned his lack of faith in a divine higher power.

In his book entitled The Grand Design, he says that the laws of science are in place and do not require a creator to have started everything.

Hawking has also previously said he doesn’t believe in heaven or an afterlife.

When asked in the interview if he thought space exploration was a good thing to invest billions of dollars in, he said that colonizing other planets might be humanity’s only hope for insurance of our long-term survival.

From daily El Pais in Spain:

US woman held in Tenerife for death threats against Stephen Hawking

“I am right next to you and I can kill you,” read one of the messages sent by the suspect, who traveled to the Spanish island to be near her target

Santa Cruz de Tenerife, 1 JULY 2016 – 16:55 CEST

Spanish police have arrested an American woman for issuing death threats against the astrophysicist Stephen Hawking at a science event on the island of Tenerife.

The 37-year-old suspect was detained in the municipality of Arona, on the most populous of the Canary Islands, on Wednesday – the same day that Hawking delivered his first lecture at the Starmus International Festival.

The woman, who has no prior record and had traveled to Tenerife by herself, could be facing a six-month prison sentence and immediate deportation for harassment and issuing serious threats against the famous scientist, legal sources told the Efe news agency.

The same sources said that one of the cosmologist’s children alerted authorities after detecting over 100 threatening messages on Twitter and in e-mails on Tuesday. The messages contained sentences such as “I am going to kill him.” …

Police investigators who searched her hotel room found a collection of esoteric items linked to religious extremism and contrary to Hawking’s theories denying the existence of God. They also found notes and documents detailing the scientist’s residence and workplace, and notebooks outlining precise plans on how to approach her target.

Hawking’s Wednesday address had attracted long lines of people at the science and arts festival. The astrophysicist arrived on stage flanked by two members of the Spanish National Police, an unusual sight that caused some alarm among members of the audience. Outside the venue, other officers checked visitors’ bags.

That same day, the police arrested the alleged stalker at a hotel located very near the festival venue, the Pirámide de Arona, which contains one of the biggest auditoriums in Europe.

The woman had apparently been issuing threats against Hawking for years, but the situation got out of hand in recent days, when the threats proliferated over e-mail an in the social media.

“I am going to kill you.” read one of the messages. “I am right next to you and I can kill you,” said another.

The e-mails included specific plans to end the scientist’s life, the police said.

According to this source, the suspect is 41 years old.

According to La Opinión de Tenerife, the suspect is Jenny Theresa C. These names sound Christian to me. If the suspect would have had a Muslim name like Fatima, then probably she would have been all over the Murdoch and other corporate merdia, not just in this Canary Islands local paper.

Black holes colliding, video


This video says about itself:

11 February 2016

The Sound of Two Black Holes Colliding (Edited Longer Version). By LIGO

In Milestone, Scientists Detect Gravitational Waves As Black Holes Collide: here.

Astronomers from the Laser Interferometer Gravitational-wave Observatory (LIGO) Collaboration have published the first detection of gravitational waves, ripples in the fabric of space and time. The announcement comes almost exactly a century after Albert Einstein, in mid-1916, predicted the existence of the waves on the basis of his Theory of General Relativity: here.

Gravitational waves, new discovery


This video says about itself:

LIGO‘s First Detection of Gravitational Waves! | Space Time | PBS Digital Studios

11 February 2016

Today, over 100 years after Einstein proposed his theory of general relativity, we are proud to announce that his final major prediction has been verified! Gravitational waves have officially been detected by LIGO! We are still getting details as the teams of physicists go over the data, but this is a huge deal, and is an exciting new step in understanding our universe.

See also here.

Publication about this in Physical Review Letters: here.

Einstein’s General Relativity theory, 1915-2015


Albert Einstein

By Don Barrett in the USA:

100 years of General Relativity

“Thus, the general theory of relativity as a logical edifice has finally been completed”—Albert Einstein, November 25, 1915

These words were spoken by Albert Einstein one hundred years ago, concluding a series of four lectures at the Prussian Academy of Sciences in Berlin on a new theory of universal gravitation, extending and amending the work Isaac Newton published 228 years earlier. In the accompanying paper, Die Feldgleichungen der Gravitation (The Field Equations of Gravitation), Einstein published for the first time the final and correct equations for what would come to be known as the general theory of relativity. This work, an elaboration on the special theory of relativity worked out ten years previously, remains one of the two central pillars of modern physics.

While the scientific community pursued and studied this work, the Great War raged in its second year. Rationing, hunger and international isolation were features of everyday life. Physicists such as Karl Schwarzschild were deployed on the various fronts. Two years later would see the conquest of political power by the masses under the leadership of the Bolshevik Party in Russia, redefining the political landscape for the rest of the century.

Produced in a revolutionary epoch, general relativity continues to be regarded as one of the momentous achievements of physics, yet its implications are far from exhausted. Even after the passage of a century, new insights connecting the theory and observed phenomena appear each year in the publications of thousands of physicists across the globe. It was the capstone to a century of intellectual struggle and the catalyst to a deeper understanding of the material world.

Einstein’s work did not emerge in isolation. The growth of 19th and early 20th century science was inseparable from the technical innovation driven by the engine of capitalism during the period of its rise as an economic system. The first high accuracy refracting telescope, built by Joseph Fraunhofer and installed at Tartu in 1824, was a derivative of the surveying theodolite, the essential tool for dividing up land and marking national boundaries. High accuracy clocks and sextants, necessary for quantitative astronomical measurements, were initially treated as strategic secrets of state because of their critical role in navigation. The invention of the telegraph allowed for closer and more immediate collaboration among astronomers both within their respective countries and across national borders. As these new more precise technologies emerged, questions regarding humanity’s understanding of matter could be revisited.

Joseph von Fraunhofer (1787-1826) together with his surveying theodolite and his Tartu refractor of 1824, the first modern telescope

This led to a renewed interest in theories of planetary motion, which are the origins of the study of gravity. Ptolemy begin this work in the second century BCE when he explained the positions of the known planets in the sky by a sort of clockwork motion of planets in concentric and slightly offset circles; this theory survived for 15 centuries. It was overturned by Johannes Kepler on the basis of a slight yet critical discrepancy of its predictions, which led Kepler to a “road to a complete reformation of astronomy.” His new theory not only correctly described the motion of the planets through the sky, but concluded that their paths in space must be ellipses around the Sun. Galileo’s observations of Jupiter’s four largest moons showed that Kepler’s theory was correct not just for planets orbiting the Sun, but for moons orbiting planets.

Newton provided a deeper understanding of the elliptical motion by reducing it to a simple and universal law of force between the Sun, the planets, in fact everything in nature, varying with the masses and distances of the attracting bodies. To elaborate the implications of his theory, Newton, alongside the German mathematician Gottfried Wilhelm Leibniz, developed an entire new branch of mathematics, differential and integral calculus. Newton’s theory, combined with the new precision of 19th century technique, culminated in the discovery in 1846 of Neptune, a planet whose existence was deduced from its slight effect on the motion of Uranus by mathematical analysis. The French scientist and republican François Arago famously remarked that Neptune had been discovered “with the point of [a] pen.”

But contradictions to Newton’s theory began to develop through the 19th century. Urbain Le Verrier, one of the astronomers who predicted Neptune’s orbit, noted that the motion of the Mercury, the innermost and most rapidly orbiting planet, was deviating very slightly from its predicted path. Most of the deviation could be specifically calculated and modeled away as due to tugs from the other planets; the remainder, an effect of only seven percent of the whole, remained unexplained. Searches were made for an undiscovered inner planet adding its own perturbations. None has ever been found.

Other areas of 19th century physics were challenged by discovery after discovery tied to improvements in technique and materials. Hitherto unknown types of radiation were detected, not directly by the human senses, but by their physical effects. Thus 1799 brought the discovery of infrared rays; 1800, ultraviolet rays; 1886, radio waves; 1895, x-rays. The apparent stability of matter itself was shattered with the discovery of radioactivity by Henri Becquerel in 1896.

The high point of this scientific turmoil was the discovery of two new types of universal forces: electricity and magnetism. Alessandro Volta’s pile, the first battery, was assembled in 1800. Flowing electricity was found to create magnetism by Hans Ørsted in 1820. Michael Faraday showed that changing magnetic fields created electricity in 1831, and thus created the basis for modern electrical power generation. Faraday also first described magnetism using the concept of a field of magnetic lines existing in definite physical relations with other forms of matter. Contemporaries viewed this field as merely a mathematical abstraction, but the later work of Maxwell and much of 20th century physics showed that fields do in fact exist as an independent material reality.

The full theory of these phenomena was worked out by James Clerk Maxwell, whose equations of 1861 and their refinement in 1865 would unify electricity and magnetism into a new theory of electromagnetism. This theoretical unity for a natural force was matched only by Newton’s work on gravitation, two centuries previously. The great physicist Ludwig Boltzmann gave some voice to the impact Maxwell’s contribution made when he quoted Goethe’s Faust: “Who was the god who wrote these lines?”

Maxwell’s equations, tested by Heinrich Hertz’s deliberate construction of equipment to produce and detect the predicted waves we now call radio, suggested the various other “rays” already discovered composed a common form as electromagnetic waves. What distinguished them was simply the wavelength between crests in an electromagnetic spectrum of radiation.

Into this ferment was born Albert Einstein in 1879, just months before Maxwell’s death. The young Einstein was captivated by Maxwell’s work. In autobiographical notes, he stated, “The most fascinating subject at the time I was a student was Maxwell’s theory.” Inspired by Maxwell’s study of light, a 16-year-old Einstein conducted his first significant gedankenexperiment (thought experiment). He imagined what it would be like to ride along such an electromagnetic wave at the same speed. Would it appear frozen, since the motion would be along its crest, like surfing along an ocean wave? The equations did not admit this possibility. More intriguingly, the theory of electromagnetism posited a fixed velocity—the speed of light—while Newton’s equations implied no such limit, instead describing the force of gravity operating with instantaneous effect.

Why should the form of the physical laws governing two different “fundamental forces” treat velocity so differently? By 1893 Oliver Heaviside would demonstrate that a modified theory of gravity incorporating a Maxwell-like speed limit must exhibit new behavior, including wave-like behavior. And what should the speed of Maxwell’s waves be measured against? These were questions posed to physicists as the end of the 19th century approached.

The speed of light had been measured crudely by Ole Rømer in 1676 by measuring the sixteen-minute difference in the clockwork motions of Jupiter’s moons from when Earth was on the near and far side of its orbit around the Sun. In 1879, Albert Michelson measured the speed of light not by using the natural motions of the solar system, but rather by reflecting pulses of light off a spinning mirror. By tuning the spinning rate, one could measure the speed. The accuracy of this technique was far above previous measurements: it was good to one part in six thousand.

Ten years later, in 1889, Michelson, together with Edward Morley, used a variation of this device to compare the speed of light in two separate directions at the same time. It was assumed there was some stationary luminiferous aether through which the electromagnetic vibrations of Maxwell’s equations (i.e., light) propagated. The refined Michelson-Morley device could compare the speed of light going in different directions, this time to one part in sixty thousand. Since the Earth travels about the Sun at 30 kilometers per second, an enormous effect should have been seen in the speed of light measured along and perpendicular to the presumed aether. But, as Einstein would write in 1916, “the experiment gave a negative result—a fact very perplexing to physicists.”

Several physicists lent their efforts to construct ad-hoc “corrections” to explain the null result of the Michelson-Morley experiment. These would apply to moving bodies and cancel the expected measurements of aether drift. Hendrik Lorentz and George FitzGerald proposed a contraction in the scale of length with speed, such that an exact cancellation would occur against the expected difference in the speed of light as measured from a platform in motion. Such were the efforts to save the laws of electromagnetism from the realities of experimental results at the close of the century.

Einstein’s solution to the problem was both brilliant and profoundly radical. He recognized that there was a fundamental incompatibility between the way Newton and Maxwell expressed time and space in their theories, and he settled this conflict in favor of Maxwell rather than Newton. It would take a decade to fully work out the consequences. Here he was influenced by a physicist who became more famous for his philosophical speculations than his (significant) discoveries in the field of mechanics, Ernst Mach (1838-1916).

Mach explored through thought experiments the contradictions of Newton’s assumption of an absolute frame of reference, an absolute space and time against whose background the motion of objects could be measured. He contended that such an absolute space and time had no real physical meaning: motion was relative to an observer, not absolute. In considering Mach’s arguments, Einstein developed the understanding that observers who were not accelerating in relation to each other should see the same physical laws, and that this must hold for any development of new physics.

Mach took his denial of absolute space and time to an idealist conclusion philosophically, claiming that matter itself could not be considered an absolute, i.e., existing independently of the observer. The world, he claimed, consisted entirely of sensations and complexes of sensations. Lenin made Mach, and idealist philosopher Avenarius, the principal targets of his polemic in defense of dialectical materialism, Materialism and Empirio-Criticism.

Einstein did not follow Mach on his erroneous philosophical path. On the hundredth anniversary of Maxwell’s birth in 1931, Einstein opened his comments with following: “The belief in an external world independent of the perceiving subject is the basis of all natural science.”

Even as the philosophical debates carried on, the paradox of the Michelson-Morley “null result,” showing the same speed of light in all directions, and the deeper contradiction was resolved by Einstein’s special theory of relativity, published in 1905. (See: One hundred years since Albert Einstein’s annus mirabilis) Einstein’s boldest stroke was to assume as a basic postulate that observers in uniform motion would all see the same laws of physics from their individual perspectives, including the same speed of light. The germ of this project was found in Maxwell’s equations, with the speed of light serving as a critical natural constant.

One of the consequences of Einstein’s theory is that mass and energy, rather than subject to separate and independent conservation laws, are conserved together and are therefore at some fundamental level equivalent. This famous equivalence of mass and energy is expressed in the equation known across the world: E=mc2. The speed of light links small amounts of mass to enormous amounts of potential energy. Originally thought to be only of academic interest, this conversion was later carried out through the mechanism of the nuclear fission chain reaction. The energy released by the two atomic bombs dropped by the United States at the end of World War II, which each incinerated a city, was the equivalent of less than one gram of mass.

There was, however, a more daunting task. Einstein and his contemporaries had managed to recast the equations of electromagnetic physics so that different uniformly moving observers saw the same laws. The same approach would not work for gravitational physics. Newton’s equations still differed from Maxwell’s equations in that they implied instantaneous action, that is, infinite velocities. Special relativity had decisively shown that the fastest velocity was that of light, thus limited the speed at which even gravity could influence matter. Integrating these concepts into Newton’s work would occupy Einstein and the broader physics community from 1907-1915, even as the world political situation tobogganed towards catastrophe.

To be continued

Part II of this is here. Part III is here.

Bird migration, new research


This video says about itself:

Physics of Bird Migration

29 April 2013

It is spring and we went to check out the migratory birds returning from their winter grounds. It is pretty incredible to think that some of them have crossed deserts and oceans on their journeys, and they still manage to find their way back to the same locations every year.

For example, did you know that the Arctic Tern is the World Record holder when it comes to migration amongst birds? It spends Northern Hemisphere summers in the Arctic and then for winter it flies all the way to the Antarctic! Absolutely crazy to think that in one year it has seen more of the world than most of us will in a lifetime. In this week’s video we take a look at the physics behind a few of the adaptations that the birds have evolved to be able to perform these annual migrations. Enjoy!

Produced by: Jonas Stenstrom

Filming help by: Louise Fornander & John-Mehdi Ghaddas

From the Annual Review of Physiology (2015):

The Neural Basis of Long-Distance Navigation in Birds

Abstract

Migratory birds can navigate over tens of thousands of kilometers with an accuracy unobtainable for human navigators. To do so, they use their brains. In this review, we address how birds sense navigation- and orientation-relevant cues and where in their brains each individual cue is processed. When little is currently known, we make educated predictions as to which brain regions could be involved.

We ask where and how multisensory navigational information is integrated and suggest that the hippocampus could interact with structures that represent maps and compass information to compute and constantly control navigational goals and directions. We also suggest that the caudolateral nidopallium could be involved in weighing conflicting pieces of information against each other, making decisions, and helping the animal respond to unexpected situations. Considering the gaps in current knowledge, some of our suggestions may be wrong. However, our main aim is to stimulate further research in this fascinating field. Expected final online publication date for the Annual Review of Physiology Volume 78 is February 10, 2016. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.