Astronomers discover galaxy with unique black holes


This 5 January 2016 video is about the newly discovered galaxy.

From Associated Press:

Rare galaxy with 2 black holes has 1 starved of stars

By MARCIA DUNN

Jan. 5, 2016 2:11 PM EST

KISSIMMEE, Fla. (AP) — An astrophysicist has discovered something even rarer than a double-black hole galaxy: a skinny black hole.

The University of Colorado at Boulder‘s Julie Comerford reported her findings Tuesday at the American Astronomical Society’s annual meeting in Kissimmee, Florida.

To date, only 12 galaxies are known to exist with two black holes in their midst, Comerford said. Normally galaxies have a single supermassive black hole at the center, equivalent to 1 million to 1 billion times the mass of our sun.

But in this newly identified galaxy about 1 billion light-years away, one of the two black holes is significantly smaller than the other and apparently starved of stars. Black holes typically are surrounded by stars; this one appears “naked.”

Comerford speculates the slim black hole lost mass in the collision of two galaxies that merged into this one —” a crash diet.” Or it’s a rare example of an intermediate-sized black hole that likely will morph over time into a supermassive monster.

Astronomers have yet to confirm an intermediate-size black hole, which makes Comerford’s streamlined target extra tantalizing. Intermediate black holes are 100 to 1 million times the mass of our sun.

Comerford used the Hubble Space Telescope and NASA’s Chandra X-ray Observatory in her study. She discovered this latest two-black hole galaxy — her fourth — last year. Finding a potential intermediate-size black hole inside was “an extra bonus,” she told reporters.

The first double-black hole galaxy was found in 2003 by accident, according to Comerford. She is trying to systematically uncover more. The findings should shed light on the evolution of black holes.

This particular galaxy is catalogued as SDSS J1126+2944.

See also here.

Spectacular Geminid meteor shower in China


This video says about itself:

Chinese Star Gazers Witness Peak of Geminid Meteor Shower

15 December 2015

Star gazers in some parts of China had the opportunity to witness the peak of the Geminid meteor shower on early Monday and Tuesday mornings.

As the most consistent and active annual shower, the Geminids were seen from Monday to Tuesday. As the date of its highest intensity being at dawn on Dec. 15, star gazers can see 120 meteors per hour with interference of moonlight.

Star gazers in Taiyuan, capital of north China’s Shanxi Province, went to the mountains to catch views of the Geminids.

“One student has seen more than 60 meteors….I will count the number. It is very exciting,” said Yang Jun, one star gazer.

As the Geminids are always seen in December, star gazers must keep themselves warm if they want to watch it outdoors. Although it was quite cold, they chose to lie on the ground rather than stay in their cars to enjoy a better view.

“The Geminid meteor shower is hard to witness and there are only three good chances to see them. So we should seize every opportunity. Lying on the ground will give us a wider view of the meteors unlike inside the car where it is much warmer but we can see fewer meteors,” said Yin Jian, another star gazer.

More on this is here.

From timeanddate.com:

In 2016, the Quadrantids [meteor shower] will peak on January 4. A third quarter Moon will make for good viewing conditions. Astronomers suggest that observers try their luck after midnight on January 4.

Star gazing for children on Dutch Texel island, 18 December 2015: here.

Spacecraft’s Jupiter photos expected in 2016


This video says about itself:

Mission Juno – Great documentary on Jupiter and NASA’s Juno probe arriving at the gas giant in 2016

11 October 2013

Explaining the science of Jupiter and the exciting Juno mission. Features interviews with scientists and engineers working on the probe with interesting computer-generated imagery of the mission.

From Astronomy magazine:

NASA returns to Jupiter 20 years after Galileo

The Juno spacecraft meets the gas giant July 4, finally ending the decades-long hiatus of Jupiter missions.

By Eric Betz

Monday, December 07, 2015

When Galileo Galilei turned his telescope to Jupiter in 1610, he uncovered the planet’s four large moons, as well as a new vision of the cosmos. Not everything had to orbit Earth.

NASA’s first dedicated mission to Jupiter, named in honor of the great astronomer, was intended to bring about a similar revolution. And it mostly did. Much of what astronomers know about the gas giant and its satellites still comes from Galileo’s dataset.

But that’s poised to change July 4, 2016. NASA’s Juno spacecraft will beam breathtaking views of the gas giant and its atmosphere back to Earth. Every two weeks, the solar-powered spacecraft will plunge past Jupiter at a distance as close as 3,100 miles (5,000 kilometers) above the cloudtops. An array of scientific instruments will also help Juno peer into the heart of the largest planet in the solar system, uncovering the planet’s structure, atmosphere, and magnetosphere. Another visit to the system, the Europa Multiple Flyby Mission, is also in the works.

But part of the need for such follow up missions stems from trouble with the Galileo spacecraft. Launched in 1989 after years of delay due to the Space Shuttle Challenger disaster, Galileo rewrote planetary science textbooks when it arrived December 7, 1995, but it was plagued by one severe problem.

The spacecraft’s 16-foot-wide umbrella-shaped high-gain antenna was supposed to unfurl itself after traveling far enough from the Sun. This would allow large images to be sent back every minute for years. Instead, the motor got stuck and the antenna never deployed. Galileo’s inadequate connection turned a data deluge into a trickle. Observations were compressed and forced through a secondary dish using a signal 10,000 times weaker.

This trickle also frustrated scientists wanting to know more about one of the most tantalizing targets in the solar system — Europa. Galileo made only about a dozen close flybys of the ice moon. And during two of those, the spacecraft went into safe mode and couldn’t collect any data.

So the single highest-resolution Europa image Galileo snapped has just 6 meters per pixel resolution and isn’t even in color. Still, Europa’s first photo album was startling.

Galileo imagery seemed to confirm what astronomers suspected –– Europa was best explained as a spinning shell of ice atop a large liquid water ocean. The surface also gave clues to Europa’s history. Its fractured and icy terrain crawls around, breaking up and pushing together in a process akin to plate tectonics –– the only known world other than Earth with such geology.

Galileo’s magnetometer also detected an induced magnetic field between Jupiter and Europa. And the easiest way to interpret that is with a salty, global subsurface ocean. Ice simply isn’t conductive enough.

The team only managed to gather enough data for a frustratingly low-resolution map of the moon, but the few high-resolution images were enough to whet scientists’ appetites.

Earlier this year, NASA formalized plans to fill in those blank spots with the Europa Multiple Flyby Mission spacecraft that should launch sometime in the 2020s.

By the time it reaches Jupiter, we should be approaching the 40th anniversary of Galileo’s launch. Clearly outer solar system exploration isn’t for the faint of heart.

Japanese spacecraft circles Venus at last


This video says about itself:

Japan’s Akatsuki Probe Finally Reaches Venus

7 December 2015

After spending the last five years essentially lost in space, the Japanese probe Akatsuki fired up its engines this last weekend in hopes of finally entering the orbit of Venus.

There is often bad news about science in Japan. The present right-wing government is banning social sciences. And there is pseudo-scientific Japanese whaling.

Now, some good news for a change.

From Nature journal:

Japan’s Venus orbiter makes comeback

Five years after a failed insertion into the planet’s orbit, Akatsuki finally reaches its target.

Alexandra Witze

07 December 2015

Japan’s Akatsuki spacecraft has entered orbit around Venus, five years after its first attempt failed. On 7 December, at 8:51 a.m. Japan time, Akatsuki ignited four small thruster engines for roughly 20 minutes. The tiny push was enough to nudge the probe into the pull of Venus’s gravity.

As Nature went to press, exactly what that orbit looks like remained unclear. But mission scientists are confident that the spacecraft has at least partly redeemed itself, after a 2010 attempt to reach Venus left Akatsuki spiralling around the Sun.

“It’s in orbit!” said Sanjay Limaye, a planetary researcher at the University of Wisconsin–Madison, and a participating scientist on the mission. “Everyone is very happy.”

The Japan Aerospace Exploration Agency (JAXA) plans to announce the exact details of the orbit at 6 p.m. Japan time (9 a.m. London time) on 9 December. Even the best-case scenario would see Akatsuki travel a much more stretched-out orbit around Venus than originally planned. The spacecraft could range about 500,000 kilometres from the planet at its farthest point, taking perhaps 14 or 15 days to make each orbit. Eventually, mission controllers plan to fire the thrusters again to shrink the orbit further — to about 330,000 kilometres at its farthest point. That would see it completing a circuit around Venus about every 8 days.

“It’s been quite a long period of waiting,” says Masato Nakamura, JAXA project manager at the Institute of Space and Astronautical Science in Sagamihara.

Akatsuki was launched in May 2010 on a mission to study Venus’s ever-changing atmosphere, which rotates at up to 100 metres per second — much faster than the planetary surface below it. The spacecraft carries five cameras, ranging from infrared to ultraviolet wavelengths, to study different atmospheric features, including the lightning that is thought to flash through Venus’s acidic clouds.

All seemed well until 7 December 2010, when the spacecraft fired its main engine to enter Venus’s orbit. Unknown to mission controllers, salt had built up on a valve between a helium tank and a fuel tank, and the blockage caused a ceramic nozzle in the propulsion system to break. Akatsuki went sailing towards the Sun, rather than into orbit around Venus.

JAXA engineers spent years studying whether they could recover the mission (M. Nakamura et al. Acta Astronaut. 93, 384–389; 2014). With the main engine dead, the oxidizer fuel was also useless, so mission controllers dumped 65 kilograms of fuel into space in October 2011. This made the spacecraft lighter and easier to manoeuvre, which enabled it to reach orbit with less thrusting.

The crucial engine burn involved four of the spacecraft’s eight thrusters. These smaller engines are normally used to make minor adjustments to the probe’s orientation, rather than major changes to its trajectory. Because the thrusters are lower power than the main engine, they needed to burn for longer than usual.

Twilight zone

Despite the rescue’s apparent success, the spacecraft’s unexpected detour might still cause problems. Because it has spent more time closer to the Sun than originally designed, Akatsuki is warmer than expected, which may have harmed some of its equipment; this could limit operations at Venus.

During its five years in deep-space wilderness, Akatsuki conducted a little science, such as transmitting radio signals to Earth through the solar corona to measure how the Sun’s turbulence scatters radio waves (T. Imamura et al. Astrophys. J. 788, 117; 2014). “The past five years have been a tough period for us,” says team member Takeshi Imamura.

Akatsuki is scientists’ only chance at seeing the planet up close for the foreseeable future. The European Space Agency’s Venus Express spacecraft stopped working a year ago, after eight years of circling the planet. “The new observations from Akatsuki will both extend and complement the data we have from Venus Express, so the scientific result of the two together will be more than the sum of the two individual missions,” says Håkan Svedhem, project scientist for Venus Express. NASA has put two Venus probes on its shortlist of five candidates for the next Discovery-class mission, which would launch no earlier than 2020.

JAXA has a history of nail-biting second chances. Its Hayabusa spacecraft survived a number of near-fatal incidents on the way to and from the asteroid Itokawa. But in 2003, after an extended effort to make the mission work, JAXA lost its Mars-bound Nozomi spacecraft, first to a problem with a fuel valve, and then to a solar flare that fried its electronics.

Akatsuki’s move is only the second such deep-space recovery. In 2000, NASA’s Near Earth Asteroid Rendezvous spacecraft made it into orbit around the asteroid Eros after a first missed attempt in 1998.

After the first try ended in failure five years ago, Japan’s first Venus Climate Orbiter, Akatsuki, successfully entered orbit above the planet Venus on Monday, Dec. 7. Japan is only the fourth entity, behind Russia, the United States and the European Space Agency (ESA), to place a spacecraft around Earth’s nearest planetary neighbor: here.

Japanese scientists rescue lost Venus space probe with daring maneuvers: here.

Vampire stars, new Hubble telescope discoveries


This video says about itself:

Variable Star Seen Pulsating By Hubble | Time-Lapse Video

17 December 2013

Variable star RS Puppis was observed by the Space Telescope over a period of 5 weeks. These types of stars are unstable because they have consumed most of the hydrogen fuel. The pulsations seen are not moving gas, but light echoes.

From Space.com in the USA:

Secrets of Vampire Stars Revealed in Hubble Telescope Data

by Sarah Lewin, Staff Writer

December 08, 2015 05:19pm ET

New observations from the Hubble Space Telescope have revealed the hidden hosts feeding vampirelike blue straggler stars, strange objects that appear to stay uncannily young-looking instead of growing into old red giant stars.

When an aging star exhausts most of its fuel, it balloons outward into a huge red giant. But in a cluster of stars that formed at the same time, some will look eerily young: While the stars’ contemporaries are bulky and cooler, they remain trim with a hotter, bluer light as if they’re getting infusions of new fuel. So blue straggler stars get their name because they “straggle” behind the typical star life cycle.

A group of astronomers surveyed 21 blue straggler stars in a cluster about 5,000 light-years away to determine their youthful secrets. The Hubble Space Telescope was able to spot evidence of orbiting white dwarf stars that contributed mass to many of the stragglers.  [Amazing Hubble Space Telescope Photos: Latest Views]

Scientists have known about these blue stragglers since 1953, but the source of their extra fuel has remained a mystery. Researchers suspected they might be in a binary system — two stars which orbit each other closely — where one star siphons material off its partner star. But the mechanism wasn’t certain. They could also have merged with other stars or collided with unlucky victims.

A 2011 study surveyed the star cluster NGC 188 to investigate its blue straggler population, and now follow-up observations from the Hubble Space Telescope have revealed the ultraviolet signatures of white dwarf stars locked into orbit with seven of the blue stragglers. An additional seven show other evidence of mass transferring from another star, although white dwarfs haven’t been spotted.

“Until now there was no concrete observational proof, only suggestive results,” Natalie Gosnell, an astronomer at the University of Texas, Austin, and lead author of the new work, said in a statement. “It’s the first time we can place limits on the fraction of blue stragglers formed through mass transfer.”

For about two-thirds of the blue stragglers surveyed, this research confirms this mass transfer process. The more massive star in a binary system swells into a red giant, overshadowing its companion — but then, its mass is siphoned away by the companion star. The balance shifts as the companion star glows hotter and brighter with the extra mass until only the small, dense stellar core remains of the first star — it collapses into a white dwarf. Viewers from Earth see only the blue straggler as a single, unusually bright and hot star.

The researchers sniffed out the white dwarfs’ presence by detecting the stragglers’ movement back and forth, caused by orbiting with another star, and verified it by identifying a bright ultraviolet signal with Hubble. Only signatures from the youngest, hottest white dwarfs can be detected that way, but the binary systems found will add to researchers’ understanding of how stars grow and change in such systems.

It’s extraordinary how much we know about how single stars evolve, but our knowledge of how binary star systems work is incomplete, Robert Mathieu, an astronomer at University of Wisconsin-Madison and study co-author, said in another statement. (Mathieu also worked on the previous survey of this star cluster.) Blue stragglers are only one of the mysterious characters researchers need to scrutinize.

“For the evolution of single stars like our sun, by and large, we got it right, from birth to death,” Mathieu said. “Now we’re starting to do the same thing for the one-quarter of stars that are close-orbiting binaries. This work allows us to talk not about points of light, but about the evolution of galaxies, including our own Milky Way. That’s a big deal, and getting it right is an even bigger deal.”

The new work was detailed Dec. 1 in The Astrophysical Journal.

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.

Leonid meteor shower tonight


This video says about itself:

Top Night Sky Events November 2015 – Eyes on the Skies

15 November 2015

November is the month of the Pleiades star cluster. On these November nights, the Pleiades cluster shines from nightfall until dawn. It’s low in the east at nightfall, high overhead around midnight and low in the west before dawn.

The 2015 Leonid meteor shower is expected to be at its best on the night of November 17-18. The predawn hours on November 18 are the optimum time, no matter where you live on the globe. Usually the most meteors fall in the dark hours before dawn.

Moon near Neptune on November 19: here.

ORION

Orion the Mighty Hunter – perhaps the easiest-to-identify of all constellations – rises at mid-evening in late November and early December. Orion will climb over your eastern horizon by around 9 p.m. tonight. You can find this constellation easily!

Full moon on November 25

Full moon is November 25, 2015. Although moon can be seen from anywhere worldwide on this night – except southern Antarctica – its path in the sky varies, depending on where you live. Enjoy the all-night appearance of the full moon tonight, as it mimics the path of the May sun across your sky!

Clips credit: ESA/NASA and ESO

From USA Today:

Sky spectacle: The Leonid meteor shower is coming

Doyle Rice and Elizabeth Weise

11:53 p.m. EST November 16, 2015

Be sure to keep an eye to the sky this week: The Leonid meteor shower, an annual mid-November treat, will soar across the night sky Tuesday and Wednesday.

The Leonids appear to be coming from the constellation Leo the Lion (hence their name) in the east, but they should be visible all the way across the sky.

Estimates range from seeing a few meteors up to dozens per hour at the peak, Astronomy magazine reports. Leonids are rather speedy, striking Earth’s atmosphere at a whopping 158,000 mph, the fastest of any meteor shower.

As with most meteor showers, the best time to watch the Leonids is usually between the hours of midnight and dawn, according to earthsky.org. Some good news from NASA: The waning crescent moon should leave skies dark enough for a decent show.

The expected peak mornings are Nov. 17 and 18. (That’s the mornings — not the evenings — of the 17th and 18th.)

Take a peek at the most distant object in our solar system.