One of the weirdest bits of physics is proved beyond doubt (almost)

IN THE 1930s Albert Einstein was greatly troubled by a phenomenon that came from quantum theory. Entanglement, as it is called, forever intertwines the fates of objects such as subatomic particles, regardless of their separation. If you measure, say, “up” for the spin of one photon from an entangled pair, the theory suggests that the spin of the other, measured an instant later, will surely be “down”—even if the two are on opposite sides of the galaxy. This was anathema to Einstein and others: it looked as if information was travelling faster than light, a no-no in the special theory of relativity. Einstein was quotably derisive, calling the idea “spooky action at a distance”. But after 80 years of physicists’ fretting, a cunning experiment reported this week proves that such action is in fact how the world works.

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If you want to describe the Universe we live in today, from a physical point of view, there are only three things you need to understand:

• What different types of particles are allowed to be present within it,
• What the laws are that govern the interactions between all those different particles, and
• What initial conditions the Universe starts off with.

If you give a scientist all of those things and an arbitrary amount of calculational power, they can reproduce the entirety of the Universe we experience today, limited only by the quantum uncertainty inherent to our experience.

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08 October 2015
LISA Pathfinder, ESA's demonstrator for space-based observations of gravitational waves, has arrived at Europe's spaceport in Kourou, French Guiana, ahead of a launch currently foreseen for 2 December.

Once operating in space, LISA Pathfinder will pave the way for future missions by testing critical concepts and technologies related to the detection of gravitational waves, ripples in spacetime, the very fabric of the Universe. To do so, it will put two small gold-platinum cubes in a near-perfect gravitational free-fall through space, and control and measure their motions with unprecedented accuracy.
LISA Pathfinder consists of a science module, containing the core elements of the science experiment, that will be transferred by a separable propulsion module to its operational Lissajous orbit around the Lagrange point L1, 1.5 million kilometres away from Earth in the direction of the Sun.

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Relativity is one of the most successful theories that Albert Einstein ever came up with. It shook the world by altering the way that we think of space and time.

One of the effects that come out of the theory of relativity is that different observers, traveling at different speeds, may take completely different measurements of the same event. However, all the measurements are technically correct. It's all relative. For example, a period of time for someone on Earth that lasts for hundreds of years may only be a couple of hours for someone zooming around in a rocket at close to the speed of light. One person may measure a stationary car to be one length, but when that same car starts racing along a track, its length appears shorter to a stationary person. These two effects are known as time dilation and length contraction.

You may be aware of the effects of relativity at insanely fast speeds: near the speed of light. It may surprise you to hear, then, that relativity is something that we experience every day. It's found in the most technical of places, and some places that may never even have occurred to you as being out of the ordinary. Since it's 100 years since Einstein published his paper on general relativity, it seems like the perfect occasion to find out how relativity affects us day-to-day.

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An image of the Vela pulsar (which lies at the heart of the Vela supernova remnant) in which glitching has been observed. The pulsar itself is the bright white spot at the centre of the hot gas, and a jet powered by its rotational pole is also observed in this Chandra X-ray Observatory image. (Courtesy: NASA/CXC/PSU/G Pavlov et al.)

Pulsars are known to be the most precise cosmic timekeepers, but occasional "glitches" or a sudden increase in their spin rate disrupts the stars' otherwise regular behaviour. A new study of the glitching process by an international team of researchers suggests that superfluid matter in the core of a pulsar may cause the poorly understood effect. The work combines radio and X-ray data to determine pulsar masses, and successfully explains glitches that are documented in 45 years' worth of observational data.

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An improbable rumour has started that the observatory has already made a discovery — but even if true, the signal could be a drill.

Davide Castelvecchi
30 September 2015

On 25 September, a sensational rumour appeared on Twitter: Lawrence Krauss, a cosmologist, reported hearing that the world’s largest gravitational-wave observatory had seen a signal, barely a week after its official re-opening.

The rumour had been spreading around physics circles for at least a week. If it is true, and if the signal seen by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) genuinely represents the signature of a gravitational wave, it would confirm one of the most-elusive and spectacular predictions of the general theory of relativity almost exactly 100 years after Albert Einstein first proposed it.

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Advanced Ligo represents one of the most sensitive measuring systems ever devised

The experiment that should finally detect ripples in the fabric of space-time is up and running.
Labs in the US states of Washington and Louisiana began "listening" on Friday for the gravitational waves that are predicted to flow through the Earth when violent events occur in space.
The Advanced Ligo facilities have just completed a major upgrade.
Scientists believe this will now give them the sensitivity needed to pick up what should be a very subtle signal.
The theoretical physicist Kip Thorne, one of the pioneers behind the experiment, went so far as to say that it would be "quite surprising" if the labs made no detection.
"We are there; we are in the ball park now. It's clear that this is going to be pulled off," he confidently told The Documentary programme on the BBC World Service.

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The Advanced LIGO begins operations this week, after 7 years of enhancement.
The Advanced LIGO Project, a major upgrade of the Laser Interferometer Gravitational-Wave Observatory, is completing its final preparations before the initiation of scientific observations, scheduled to begin in mid-September. Designed to observe gravitational waves—ripples in the fabric of space and time—LIGO, which was designed and is operated by Caltech and MIT with funding from the National Science Foundation (NSF), consists of identical detectors in Livingston, Louisiana, and Hanford, Washington.

- See more at: http://www.caltech.edu/news/advanced-ligo-begin-operations-47898#sthash.a7JhFOit.dpuf

An illustration of two black holes orbiting one another. The black hole in the center of the image is starved of gas by the black hole at the left, making the gas cloud of the black hole on the left brighter.ILLUSTRATION BY ZOLTAN HAIMAN, ADAPTED FROM FARRIS ET AL. 2014

By DENNIS OVERBYE
SEPTEMBER 16, 2015
The apocalypse is still on, apparently — at least in a galaxy about 3.5 billion light-years from here.

Last winter a team of Caltech astronomers reported that a pair of supermassive black holes appeared to be spiraling together toward a cataclysmic collision that could bring down the curtains in that galaxy.

The evidence was a rhythmic flickering from the galaxy’s nucleus, a quasar known as PG 1302-102, which Matthew Graham and his colleagues interpreted as the fatal mating dance of a pair of black holes with a total mass of more than a billion suns. Their merger, the astronomers calculated, could release as much energy as 100 million supernova explosions, mostly in the form of violent ripples in space-time known as gravitational waves that would blow the stars out of that hapless galaxy like leaves off a roof.

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LIGO experiment now has better chance of detecting ripples in space-time.

Davide Castelvecchi

Almost 100 years after Einstein presented the general theory of relativity in a Berlin lecture theatre, the quest to spot the gravitational waves he predicted may be entering its final stages.

This week, the world’s largest gravitational-wave facility is expected to start collecting data again after a 5-year US$200-million overhaul. The Laser Interferometer Gravitational-Wave Observatory (LIGO) searched fruitlessly for these cosmic ripples for almost a decade in the 2000s. But the odds that its improved version — known as Advanced LIGO — will detect any waves in the next three months may be as high as one in three, according to some of the physicists involved in the experiments.

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ABOUT THIS IMAGE:
This artistic illustration is of a binary black hole found in the center of the nearest quasar host galaxy to Earth, Markarian 231. Like a pair of whirling skaters, the black-hole duo generates tremendous amounts of energy that makes the core of the host galaxy outshine the glow of the galaxy's population of billions of stars. Quasars have the most luminous cores of active galaxies and are often fueled by galaxy collisions.

Hubble observations of the ultraviolet light emitted from the nucleus of the galaxy were used to deduce the geometry of the disk, and astronomers were surprised to see light diminishing close to the central black hole. They deduced that a smaller companion black hole has cleared out a donut hole in the accretion disk, and the smaller black hole has its own mini-disk with an ultraviolet glow.

Astronomers using NASA's Hubble Space Telescope have found that Markarian 231 (Mrk 231), the nearest galaxy to Earth that hosts a quasar, is powered by two central black holes furiously whirling about each other.

The finding suggests that quasars — the brilliant cores of active galaxies — may commonly host two central supermassive black holes that fall into orbit about one another as a result of the merger between two galaxies. Like a pair of whirling skaters, the black-hole duo generates tremendous amounts of energy that makes the core of the host galaxy outshine the glow of the galaxy's population of billions of stars, which scientists then identify as quasars.

Scientists looked at Hubble archival observations of ultraviolet radiation emitted from the center of Mrk 231 to discover what they describe as "extreme and surprising properties."

If only one black hole were present in the center of the quasar, the whole accretion disk made of surrounding hot gas would glow in ultraviolet rays. Instead, the ultraviolet glow of the dusty disk abruptly drops off towards the center. This provides observational evidence that the disk has a big donut hole encircling the central black hole. The best explanation for the observational data, based on dynamical models, is that the center of the disk is carved out by the action of two black holes orbiting each other. The second, smaller black hole orbits in the inner edge of the accretion disk, and has its own mini-disk with an ultraviolet glow.

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RECORDED IN LIGHT A ring of light surrounds the boundary of a black hole in this artist illustration. Stephen Hawking theorizes that light on this boundary encodes information about everything that falls into the black hole.

Light sliding along the outside of a black hole is the key to understanding what’s inside, Stephen Hawking says.

The proposal from the world’s most famous living physicist, presented August 25 at a conference in Stockholm, is the latest attempt to explain what happens to information that falls into the abyss of a black hole. Losing that information would violate a key principle of quantum mechanics, leading to what’s known as the information paradox.

Hawking and two collaborators claim that the contents of a black hole are inventoried on a hologram on its boundary, the event horizon. Unlike previous descriptions of this hologram, the researchers say, their proposal lays out a specific mechanism for storing information that applies to every black hole in the universe. “This resolves the information paradox,” Hawking said in his presentation at the Hawking Radiation conference at the KTH Royal Institute of Technology.

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So I’m at this black hole conference in Stockholm, and at his public lecture yesterday evening, Stephen Hawking announced that he has figured out how information escapes from black holes, and he will tell us today at the conference at 11am.

As your blogger at location I feel a certain duty to leak information ;)

Extrapolating from the previous paper and some rumors, it’s something with AdS/CFT and work with Andrew Strominger, so likely to have some strings attached.

30 minutes to 11, and the press has arrived. They're clustering in my back, so they're going to watch me type away, fun.

10 minutes to 11, some more information emerges. There's a third person involved in this work, besides Andrew Strominger also Malcom Perry who is sitting in the row in front of me. They started their collaboration at a workshop in Hereforshire Easter 2015.

10 past 11. The Awaited is late. We're told it will be another 10 minutes.

11 past 11. Here he comes.

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Inspired by Scientific American’s terrific September issue, which celebrates the 100th anniversary of Einstein’s theory of general relativity [see Addendum], I’ve dusted off an essay I wrote for The New York Times a decade ago. Here is an edited, updated version. —John Horgan

When Stevens Institute of Technology hired me a decade ago, it installed me for several months in the department of physics, which had a spare office. Down the hall from me, Albert Einstein's electric-haired visage beamed from a poster for the "World Year of Physics 2005." The poster celebrated the centennial of the "miraculous year" when a young patent clerk in Bern, Switzerland, revolutionized physics with five papers on relativity, quantum mechanics and thermodynamics. "Help make 2005 another Miraculous Year!" the poster exclaimed.

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Fermi-LAT sky map with the celestial neighborhood of the newly discovered pulsar PSR J1906+0722. The color scale shows the gamma-ray intensity. [Knispel/AEI/NASA/DOE/Fermi LAT Collaboration]

Since the release of the second Fermi-LAT catalog in 2012, astronomers have been hunting for 3FGL J1906.6+0720, a gamma-ray source whose association couldn’t be identified. Now, personal-computer time volunteered through the Einstein@Home project has resulted in the discovery of a pulsar that has been hiding from observers for years.

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