Författarbild
40 verk 329 medlemmar 8 recensioner

Verk av Ron Cowen

Queer as Folk: The Complete Third Season (2004) — Creator — 40 exemplar
Summertree (1968) 35 exemplar
The Book of Murder. (1974) 9 exemplar
An Early Frost [1985 film] (2006) — Writer — 7 exemplar
Saturday Adoption (1969) 6 exemplar

Taggad

Allmänna fakta

Kön
male

Medlemmar

Recensioner

Another one of those books that has a huge amount of content. For my own purposes I like to try and summarise but it’s pretty difficult with the range of material in this book. However, I’ve made an attempt with the following extracts to capture the main themes.
In place of Newton’s idea that a massive body pulls objects toward it because it exerts a gravitational force, the general theory says that a massive body distorts or dimples space-time so that objects fall toward it, Gravity equals curvature. ...And because Einstein’s famous formula, E = mc2, says that mass and energy are two different forms of the same entity, both can generate curvature.
With one notable exception, Newton’s law of gravitation works beautifully in the relatively weak field of the solar system. But it fails to describe the motion of stars zipping around a black hole or another extremely dense, massive body. ,,,,For example, although the orbits of all the planets precess, it’s only Mercury’s whose deviation from Newtonian gravity is large enough to be easily detected.

With the General Theory, knowing he was in over his head, Einstein turned to his college classmate Marcel Grossmann with a plea for help. Grossmann, who had become a mathematics professor specializing in geometry at their alma mater, was happy to oblige. While Einstein skipped classes (especially mathematics) that didn’t interest him and developed a reputation as a rebel who resisted instruction and alienated his teachers, Grossmann was organized, well liked, and studious. His carefully annotated notebooks on class lectures proved a lifeline for Einstein, keeping him on the path to graduation.

Knowing all too well his own [Farkas Bolyai’s] exhaustion in trying to prove the theorem, he warned his son that the study would rob him of health, peace of mind, and happiness. “I know this way to the very end,” he wrote his son in 1820. “I have traversed this bottomless night, which extinguished all light and joy in my life. I entreat you, leave the science of parallels alone.… Learn from my example.” When Bolyai contacted Gauss [about his hyperbolic geometry] the venerable mathematician refused to praise him, asserting that he himself had found, though never published, a similar geometry years earlier. Indeed, Gauss often did not publish work he deemed controversial. He would not publicly go against the prevailing thinking
Both Bolyai and Lobachevsky died without knowing their work would have a lasting impact. A discouraged Bolyai became a recluse, leaving behind 20,000 pages of mathematical manuscripts at his death at age fifty-seven in 1860. A few years later, Lobachevsky also died in obscurity, nearly blind and unable to walk.

He [Gauss] also demonstrated that a single number, the Gaussian curvature, could fully describe the curvature of a surface, such as that of a cylinder or sphere.
For his doctoral thesis, supervised by Gauss and completed in 1851, Riemann showed that a set of exotic numbers, those with a component proportional to the imaginary number square root of − 1, could be expressed as a curved surface.
Riemann finally delivered his talk, “On the Hypotheses That Lie at the Foundation of Geometry,” on June 10, 1854. Gauss may have been the only one in the audience to fully comprehend the implications of Riemann’s talk, but experts have since hailed the lecture as one of the most farsighted in the history of mathematics. Riemann was only twenty-seven.

Because a curved surface can vary in a complicated way, Grossmann had to teach Einstein about tensors, mathematical objects that keep track of more than one variable at a time. In particular, Grossmann introduced Einstein to the Riemann tensor, which directly measures the curvature of space.

In October 1914, ninety-three German scientists signed a proclamation giving their unqualified support to the German military. Einstein refused to sign the “Manifesto of the Ninety-Three” and instead was one of just four scientists to endorse a proclamation protesting Germany’s aggression.

He was not the only one working to revise his theory, Sommerfeld wrote. Hilbert also believed the “Entwurf” work was flawed and was formulating his own version.
In one of the most remarkable discoveries of the twentieth century, he finally unveiled the right solution to describe the inviolable link between space-time and gravity / matter-energy. Einstein’s compact equation takes up but a single line: Rμν − 1/ 2R gμν = 8πGN/ c4 Tμν .........It has revealed that the universe is expanding, that spinning objects drag space-time along with them the way the blades of a blender drag pancake batter, and that gravity acts as a zoom lens to reveal some of the first galaxies born in the universe, nearly 14 billion years ago.
So we can symbolically write the equation in a much simpler form, suggests astrophysicist and author Jean-Pierre Luminet: G = T Here, G stands for the geometry of space-time and T stands for matter. Geometry equals matter. That’s what it boils down to. The boldface indicates that G and T are not mere numbers. They are tensors, because they keep track of more than one direction or variable.
Moreover, in general relativity, each tensor has ten independent components, so the single formula represents ten equations.

Einstein suggested gravity as a force that acts across space with the idea that gravity is space. Specifically, he said, space and time, instead of being stiff and unchanging, are as jiggly as Jell-O. A massive body warps or curves this wobbly space-time much the way a heavy sleeper sags a mattress.

According to the Cambridge Daily News, the chair of the committee, a Major S. G. Howard, “suggested that Prof. Eddington’s ability be better employed in active prosecution of the war if placed at the disposal of the Government.” In reply, Eddington stood and declared, “I am a conscientious objector.” During the darkest days of World War I, with the German army shelling Paris, Eddington and his team of British astronomers got the official go-ahead to test a strange new theory proposed by a German-born scientist who published his work behind enemy lines. Not only that, but if Einstein was right, it would topple Newton,

But during the analysis, it was decided to exclude all the flawed Sobral images, rather than just giving them lower statistical weight. Historians have accused Eddington of doing so in an attempt to force a solution that would prove Einstein right.

Eddington meant that although he believed the observations confirmed the light bending predicted by Einstein, the study did not prove Einstein’s claimed source for the bending—the curvature of space-time.

Einstein was not the first to suggest that light is bent by gravity. Newton himself raised the possibility. At the end of his 1704 treatise, Opticks, the sixty-one-year-old scientist asked a series of questions that he felt he did not have time to investigate but hoped others might. Query number one read: “Do not Bodies act upon Light at a distance, and by their action bend its Rays; and is not this action … strongest at the least distance?”

In 1783, the English astronomer and clergyman John Michell took Newton’s notion of light bending to an extreme and calculated that some objects have such strong gravity that no light could escape—a black hole, in modern parlance.

Like today’s accusations of fake news, the fake charges against Einstein went viral. They spilled over to the United States when Arvid Reuterdahl, the dean of the engineering school at the College of St. Thomas in Minnesota, repeated Lenard’s claims. His criticisms were published in detail in the Minneapolis Tribune. Ultimately, the furor died down when experiment after experiment confirmed the light bending predicted by Einstein.

For once, Einstein bowed to the observational data gathered by astronomers. He hated to tinker with his perfect, mathematically elegant theory. But to save the universe in his theory from collapsing or expanding, he inserted a fudge factor: a constant that was denoted by the Greek letter lambda (λ) and would come to be called the cosmological constant.

Alexander Friemann [Russian], in 1922, found that, depending on the numerical value of Einstein’s cosmological constant, a static universe was just one of several possible scenarios allowed by Einstein’s theory. The universe could also expand, contract, or oscillate between contraction and expansion.
In 1929, Hubble confirmed Lemaître’s work, using observational data to formally demonstrate the linear relationship between speed (redshift) and distance. The speed at which galaxies were receding from Earth was proportional to their distance. Those that resided twice as far from Earth were speeding away twice as fast, those that were four times more distant were fleeing with four times the speed, and so on.

At that point, Peebles made what might have seemed an outlandish suggestion. He proposed that most of the matter in the universe was invisible and interacted only through its gravity. Since it did not interact with light, this invisible material, or dark matter, would generate smaller lumps in the CMB than ordinary matter; that would explain why no one had yet seen evidence of it.
By the 1970s, Zwicky’s crazy idea didn’t seem so crazy.

But Rubin found that the stars at the outer edge rotated just as rapidly. She concluded that the galaxies had to lie inside a halo of dark matter—and that there had to be ten times as much of it as there was visible material. .....And in 1992, NASA’s Cosmic Background Explorer satellite finally found evidence of the tiny hot and cold spots in the CMB that one would expect if dark matter ruled the universe. ....Observations of the size of the hot and cold spots in the CMB had revealed that the universe was flat on a large scale—that is, the angles of a triangle would always add up to 180 degrees and parallel lines would never meet.

But measurements of the actual amount of mass in the universe—both visible matter and dark matter—had come up drastically short. There simply wasn’t enough matter of any type to keep the universe flat. Where was the missing stuff? ......After some soul-searching, astronomers and cosmologists had to accept the notion that gravity had a flip side. Some kind of invisible, mysterious energy fills the universe, turning gravity’s pull into a cosmic push. ....Cosmologists call this mysterious force dark energy. But it could just as easily be called the cosmological constant. ......If dark energy does have a constant density, spread evenly throughout space, then it would indeed resemble the cosmological constant, that feature that Albert Einstein inserted into his theory of gravitation in 1917. ......After Einstein conceded that the universe was indeed expanding, he disowned the constant, reportedly calling it his greatest blunder. But he may have been right after all.

The equation Einstein presented to the Prussian Academy of Sciences on November 25, 1915, was elegant, but it symbolized ten coupled, nonlinear equations. Each equation dealt with all four dimensions (three of space and one of time). Einstein himself had only found approximate solutions to his suite of equations.

Chandrasekhar found that for a white dwarf greater than about 1.4 times the mass of the Sun (corresponding to a star that began its life at least 8 times heavier than the Sun), electron pressure would be no match for gravity. The star would continue to collapse until its radius was no bigger than the size of a city, about 10 kilometers. Gravity would squeeze nuclei so tightly that electrons and protons would fuse to form neutrons.

black holes. The objects remained a mathematical curiosity until the early 1960s, when astronomers discovered quasars, compact objects whose blazing light was believed to be fueled by monster black holes.

Observations suggest that a giant black hole lurks at the core of every large galaxy, where it governs the galaxy’s formation and growth.

The Gaia satellite, launched in 2013 by the European Space Agency, is poised to record the positions of billions of stars to an even higher degree of accuracy—about 20 millionths of an arcsecond—and is expected to see the effect of light bending by the Sun in every single one of its measurements.

But the most spectacular aspect of light bending emerged from a calculation Einstein did in 1912, three years before he completed the general theory of relativity. He showed that the most powerful magnifying lenses aren’t on Earth but in the sky. Einstein described the properties of a gravitational lens........Astronomers observed the first gravitational lens, a double image of a distant quasar, in 1979. Six years later, another team found four images of a different quasar, arranged in a cloverleaf pattern. In the years since, astronomers have found about 1,000 examples of gravitational lenses that produce multiple images of a celestial body.

Dark matter, the mysterious material now believed to outnumber the amount of visible matter in the cosmos by nine to one, can’t be seen. But this ghostly material betrays its presence through its gravity—how much it bends light from a distant body. ....Dark energy and dark matter, the primary sources of gravity, are essentially in a tug-of-war: dark matter pulls material together, while dark energy tries to pry it apart. The amount of clumping in the universe is the direct result of that epic battle.

Quantum theory describes the material universe in terms of probabilities and uncertainties, while relativity assumes that space and time can be well defined down to the tiniest levels. ......The clash between relativity and quantum theory hints that something is deeply wrong at the heart of physics. That’s exciting because it suggests there may be something brand-new, waiting to be discovered. A breakdown of relativity could even reveal that a previously unknown force is at play in the universe.

But measurements of the pair’s motion [a white dwarf and a pulsar] reveal that despite differences in their mass and composition, the neutron star and the white dwarf fall at the same rate, to within 0.16 thousandths of a percent of each other. The finding confirms the equivalence principle in the extremely strong gravitational environment of a neutron star, where the full theory of general relativity is required.

The other fundamental forces in nature—the electromagnetic force between electrically charged particles and the strong and weak nuclear forces that affect particles inside the atomic nucleus—all have a successful quantum theory. But even Einstein, who spent years trying to unify gravity and quantum theory, failed to do so.

But in [2010] Van Raamsdonk, had entered a shorter version of his paper [about marrying the General theory of relativity with quantum mechanics] in the Gravity Research Foundation’s annual essay contest, a prestigious competition Not only did Van Raamsdonk win first prize, but the award came with a delicious irony: guaranteed publication in one of the journals that had rejected him. General Relativity and Gravitation printed the shorter essay in June 2010. .....Einstein’s theory of gravity predicts that space-time is as malleable as Jell-O but does not dabble in quantum uncertainties. An electron may go through two slits at once, but relativity allows for no corresponding splitting of the electron’s gravitational field. ....But Van Raamsdonk and a cadre of other scientists approached the problem from the other direction: they started with the statistical nature of quantum theory. What they found, to their surprise, is that they could stop right there. Quantum theory, their calculations revealed, already encodes the essence of geometry, and by extension Einstein’s space-time theory of gravity. ......More precisely, Van Raamsdonk and his colleagues propose that space-time as we know it—smooth, connected, continuous—emerges from the very quality of quantum mechanics that Einstein believed would ultimately discredit the theory. That property, known as quantum entanglement, is one of the weirdest concepts in physics. ....It states that the measurement of one subatomic particle instantaneously determines the state of a partner particle—even if the two reside on opposite sides of the Milky Way. For Van Raamsdonk, the hologram idea was similar to a three-dimensional video game operated by a two-dimensional memory chip. All the three-dimensional information could be read off the two-dimensional chip. The chip and the video game each provide a complete description of the action.

But scientists found that the amount of entropy stored within a black hole is revealed not by its volume but by its surface area—in particular, the area of its event horizon, the spherical boundary inside which particles remain forever gravitationally trapped. The larger the event horizon, or area, of a black hole, the larger its entropy. ...... In this view, the area of an event horizon isn’t merely proportional to a black hole’s entropy; it is the entropy.

Specifically, Maldacena calculated a mathematical equivalence—what physicists call a duality—between a quantum field theory that resides on the surface, or “boundary,” of the universe and does not contain gravity, and a quantum field theory that describes the volume of the universe, or “bulk,” and does include gravity. .....In the absence of entanglement, space time consists of little chunks but Brian Swingle’s view is that entanglement knits the chunks together into smooth space time......It was the ultimate plot twist, Van Raamsdonk thought. Scientists had labored for years trying to figure out how to incorporate quantum mechanics into the study of space-time and gravity. Yet all along, quantum mechanics had contained the ingredients from which emerged space-time—and, by extension, Einstein’s geometric theory of gravity. [The idea remains a conjecture]

Maldacena and Susskind conjectured that anytime two subatomic particles are entangles, they may be connected by a tiny quantum version of a wormhole.....So if entanglement gives birth to wormholes, it may give birth to Einstein’s geometric theory of gravity as well. .....Knowing the connection between entanglement and space-time lends insight but still does not provide a complete theory of quantum gravity. ....The goal is to understand quantum gravity by reformulating interesting gravitational questions in the language of field theory, which physicists understand well. But it isn’t always clear how to do the translation.

In the quantum world, information is encoded by qubits, pairs of quantum states that can have the value of 1, 0, or a superposition of the two. In principle, that rainbow of possible states—if properly entangled with other qubits—is what would enable a quantum computer to perform calculations an ordinary computer could never finish.......But that ability depends on preserving the fragile entanglement among the qubits. Once these correlations between qubits are destroyed—and even a slight disturbance from the outside world can inadvertently do so—the qubits “collapse” to either 1s or 0s, and quantum computations are no longer possible.

Yet as enamored as many theoretical physicists have become of entanglement as a route to developing a theory of quantum gravity, it can’t be the whole story—a sentiment Susskind succinctly captured in the title of a 2016 paper: “Entanglement Is Not Enough.” ....... Susskind, says the role of complexity is a sign that physicists will have to reach beyond entanglement and the holographic principle in order to develop that theory.

In effect, Einstein’s theory of general relativity carries a “no-drama” clause: nothing special should happen as someone crosses the event horizon. [but that’s not obvious with a black hole]. In 2013, Susskind and Maldacena posited that the firewall was entirely unnecessary. Their theoretical work suggested that the entanglement between particles creates wormholes, or tunnels, between widely separated regions of space. The tunnel would directly link particles trapped inside the black hole to those that had long ago left the black hole. .....And, in 2017, building upon earlier work by Maldacena, three researchers found that if two black holes connected by a wormhole are quantum mechanically linked in precisely the right way, the throat of the wormhole stays open and information travels through it. Though physicists have just begun exploring this possibility, it could be a way to recover information from the scrambled Hawking radiation.

Shaking a chunk of matter would generate undulations in the fabric of space-time. These undulations, known as gravitational waves, would spread out across the universe like ripples in a cosmic pond. As a wave passes, it distorts the distance between two freely suspended masses in a particular pattern. Along the direction the wave is traveling, it has no effect on the distance. But perpendicular to that direction, the wave stretches the distance along one dimension while shrinking it along the other.

Although they can’t be heard, gravitational waves have several properties in common with sound. Sound waves generate acoustic signals—a bang, a shout, or a Mozart concerto—by alternately stretching and compressing the medium, such as air or water, through which they travel. Gravitational waves generate vibrations by alternately stretching and compressing a material—the fabric of space-time.

Over thousands to millions of years, as the black holes inched ever closer, their slow dance became a furious death spiral. Only during the final two-tenths of a second before the black holes collided, as the space-time ripples grew stronger and rose higher in frequency, could LIGO hear them. Translated into audio, the waves resembled the chirp of a bird gliding up the musical scale.

Observations with the Gemini South Telescope and the European Southern Observatory’s Very Large Telescope, both in Chile, and the Hubble Space Telescope confirmed the fingerprints of precious metals in the debris cloud. The discovery fills in a missing link in the history of cosmic alchemy, explaining how the early universe of hydrogen and helium transformed into a cosmos of planets, stars, and galaxies that contain a plethora of heavy elements.

In the absence of gravitational waves, astronomers relied on “standard candles”—stars or stellar explosions believed to have a known intrinsic brightness. Scientists then compared the known brightness to how bright the objects appeared when observed from Earth. The dimmer the body appears in the sky, the greater its distance. However, stars can vary their brightness for all sorts of reasons, and estimates of the intrinsic brightness are prone to errors. ...And, as with the standard candle method, by comparing the intrinsic strength of the waves with the much weaker strength recorded by detectors on Earth, scientists could precisely determine the distance to the merger. ...As the gravitational wave detectors record more sirens, astronomers may be able to pinpoint the expansion rate with an accuracy of better than 1 percent, helping settle an ongoing debate about the rate of expansion using the standard candle method.

In 1974, the search for gravitational waves got an unexpected boost. Russell A. Hulse and Joseph H. Taylor discovered a binary pulsar—two ultra-compact, rapidly spinning stars, orbiting each other at a furious rate. ....But by the end of 1978, with four years of observations under their belt, Hulse and Taylor found an almost perfect match with Einstein’s theory. The findings earned Hulse and Taylor the Nobel Prize in Physics in 1993 and were the first to give convincing evidence of gravitational waves. However, it would require a new and more sensitive type of gravitational wave detector, using the laser interferometer, to directly detect gravitational waves in 2015.

Luckily for black hole hunters like Doeleman, the region just outside the event horizon blazes with light. This radiation comes from two sources. One is the accretion disk, a swirling, doughnut-shaped shell of matter believed to orbit every black hole. As material from the disk spirals into the black hole at nearly the speed of light, it heats up to billions of degrees, prompting the matter to emit copious amounts of radiation. The other source is high-speed jets of glowing material expelled by black holes even as they draw material into their maw. .....The shadows are big enough thanks to the gravitational distortion of each black hole on its own event horizon, which acts as a magnifying lens. The distortion enlarges the shadow by a factor of five, Falcke and his colleagues calculated.

The first images of the event horizon of a black hole were obtained in 2019. Exactly a century earlier, astronomers had struggled to record the bending of starlight from the Sun. Now they had recorded the bending of light within spitting distance of a black hole’s event horizon—an observation that marked the beginning of a new century of discovery, one in which ghostly images will not only allow scientists to probe the nature of space-time around the strangest objects in the cosmos, but will continue to reveal precisely how well Einstein’s theory of gravity describes the workings of the universe.
I really liked this book especially the explanations of a holographic universe. Hopefully this might be a more fruitful line of research than string theory. Happy to give book five stars.
… (mer)
 
Flaggad
booktsunami | Jan 13, 2024 |
A fairly brief history of general relativity and its ramifications all the way through the detection of gravitational waves to the Event Horizon Telescope. (Publication seems to have been a bit too early for inclusion of the latter project's M87* image.) While most of the earlier chapters tell very familiar stories, the one on quantum gravity stands out for its (popular-level, to be sure) coverage of such recent/advanced ideas as the holographic principle and the possible connection between spacetime wormholes and quantum entanglement.… (mer)
 
Flaggad
fpagan | Jun 10, 2019 |
 
Flaggad
lgbtrcUCR | 1 annan recension | Jun 22, 2015 |
Based on the British series of the same name, Showtime's 'Queer as Folk' presents the American version. Following the lives of five gay men in Pittsburgh, 'Queer as Folk' is a riveting drama full of sex, drugs, adventure, friendship and love. Although the creators of 'Queer as Folk' wanted to present an honest depiction of gay life, it is by no means a comprehensive depiction. In addition to the usual sexual escapades and relationships of the five friends, the show explores critical gay political and health issues.

Directors: Michael DeCarlo, John Fawcett, and 6 more
Writers: Doug Guinan, Richard Kramer, and 3 more
Stars: Gale Harold, Hal Sparks and Randy Harrison
… (mer)
 
Flaggad
UT_WCC | Jan 27, 2011 |

Du skulle kanske också gilla

Associerade författare

Statistik

Verk
40
Medlemmar
329
Popularitet
#72,116
Betyg
4.1
Recensioner
8
ISBN
36

Tabeller & diagram