Successful commissioning of GRAVITY at the VLTI
13 January 2016

Zooming in on black holes is the main mission for the newly installed instrument GRAVITY at ESO’s Very Large Telescope in Chile. During its first observations, GRAVITY successfully combined starlight using all four Auxiliary Telescopes. The large team of European astronomers and engineers, led by the Max Planck Institute for Extraterrestrial Physics in Garching, who designed and built GRAVITY, are thrilled with the performance. During these initial tests, the instrument has already achieved a number of notable firsts. This is the most powerful VLT Interferometer instrument yet installed.

The GRAVITY instrument combines the light from multiple telescopes to form a virtual telescope up to 200 metres across, using a technique called interferometry. This enables the astronomers to detect much finer detail in astronomical objects than is possible with a single telescope.

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The Crafoord Prize in Astronomy and Mathematics 2016
ON, JAN 13, 2016 19:00 EST

The Royal Swedish Academy of Sciences has decided to award

the 2016 Crafoord Prize in Mathematics to

Yakov Eliashberg, Stanford University, Stanford, California, USA

“for the development of contact and symplectic topology and groundbreaking discoveries of rigidity and flexibility phenomena.”

and the 2016 Crafoord Prize in Astronomy to

Roy Kerr, University of Canterbury, Christchurch, New Zealand

Roger Blandford, Stanford University, Stanford, California, USA

“ for fundamental work on rotating black holes and their astrophysical consequences”

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Rumor of gravitational wave discovery is just that, source says

By Adrian Cho  Jan. 12, 2016

Science Magazine

If you follow physics, you have likely heard the rumor by now: Physicists working with a pair of gigantic detectors have finally discovered gravitational waves—ripples in space and time set off when, say, two massive neutrons stars spiral into each other—and have only to announce it. It would be a sure-fire Nobel Prize–winning discovery and the rumor sounds plausible. Sensing those waves is exactly what a $500 million project called the Laser Interferometer Gravitational-Wave Observatory (LIGO) was built to do. Numerous news outlets have reported the rumor, prompted by Twitter posts by Lawrence Krauss, a theoretical physicist and author at Arizona State University, Tempe.

There's a qualification, however: By his own account, Krauss has spoken to nobody in the 900-member LIGO Scientific Collaboration.

"I never said I've talked to anybody in the collaboration," he tells ScienceInsider. "That's why I used the word rumor. I don't know how to be clearer."

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IF TRUE, THE DISCOVERY WOULD SUPPORT ONE OF EINSTEIN'S MAJOR PREDICTIONS.
By Sarah Fecht Posted Yesterday at 11:10pm

In September, the Caltech theoretical physicist Lawrence Krauss tweeted:

@LKrauss1 amazing if true, but as scientists shouldn't we avoid spreading rumors, especially in a public space, and wait to know the facts?
1:31 PM - 26 Sep 2015

The folks on the LIGO experiment neither confirmed nor denied the rumor, and in Krauss's rumor-mongering raised hackles in the astrophysics community.

But now he's back at it again:

My earlier rumor about LIGO has been confirmed by independent sources. Stay tuned! Gravitational waves may have been discovered!! Exciting.
4:46 PM - 11 Jan 2016

There's plenty of reason to remain skeptical--we won't know for sure whether the rumor is true until we hear from the researchers on the experiment. If it does turn out to be true, it would be a very exciting finding.

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December 30, 2015

Limits on the differences of the γ values for three FRB observations. Credit: Phys. Rev. Lett. 115, 261101 – Published 23 December 2015. DOI: 10.1103/PhysRevLett.115.261101

dx.doi.org/10.1103/PhysRevLett.115.261101

A new way to test one of the basic principles underlying Einstein's theory of General Relativity using brief blasts of rare radio signals from space called Fast Radio Bursts is ten times, to one-hundred times better than previous testing methods that used gamma-ray bursts, according to a paper just published in the journal Physical Review Letters. The paper received additional highlighting as an "Editor's Suggestion" due to "its particular importance, innovation, and broad appeal," according to the journal's editors.

The new method is considered to be a significant tribute to Einstein on the 100th anniversary of his first formulation of the Equivalence Principle, which is a key component of Einstein's theory of General Relativity. More broadly, it also is a key component of the concept that the geometry of spacetime is curved by the mass density of individual galaxies, stars, planets, and other objects.

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Physicists typically think they “need philosophers and historians of science like birds need ornithologists,” the Nobel laureate David Gross told a roomful of philosophers, historians, and physicists in Munich, Germany, paraphrasing Richard Feynman.

But desperate times call for desperate measures.

Fundamental physics faces a problem, Gross explained—one dire enough to call for outsiders’ perspectives. “I’m not sure that we don’t need each other at this point in time,” he said.

It was the opening session of a three-day workshop, held on December 7 in a Romanesque-style lecture hall at Ludwig Maximilian University (LMU Munich) one year after George Ellis and Joe Silk, two white-haired physicists now sitting in the front row, called for such a conference in an incendiary opinion piece in Nature. One hundred attendees had descended on a land with a celebrated tradition in both physics and the philosophy of science to wage what Ellis and Silk declared a “battle for the heart and soul of physics.”

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Image credit: flickr user Trailfan, via https://www.flickr.com/photos/7725050@N06/631503428.

Ethan Siegel, CONTRIBUTOR

There are a lot of different ways to define science, but perhaps one that everyone can agree on is that it’s a process by which:

knowledge about the natural world or a particular phenomenon is gathered,
a testable hypothesis is put forth concerning a natural, physical explanation for that phenomenon,
that hypothesis is then tested and either validated or falsified,
and an overarching framework — or scientific theory — is constructed to explain the hypothesis and that makes predictions about other phenomena,
which is then tested further, and either validated, in which case new phenomena to test are sought (back to step 3), or falsified, in which case a new testable hypothesis is put forth (back to step 2)…

and so on. This scientific process always involves the continued gathering of more data, the continued refining or outright replacing of hypotheses when the realm of validity of the theory is exceeded, and testing that subjects that theory to either further validation or potential falsification.

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The idea that our Universe is part of a multiverse poses a challenge to philosophers of science.
Credit: R. Windhorst, Arizona State Univ./H. Yan, Spitzer Science Center, Caltech/ESA/NASA

A debate between physicists and philosophers could redefine the scientific method and our understanding of the universe
By Davide Castelvecchi, Nature magazine on December 23, 2015

Is string theory science? Physicists and cosmologists have been debating the question for the past decade. Now the community is looking to philosophy for help.
Earlier this month, some of the feuding physicists met with philosophers of science at an unusual workshop aimed at addressing the accusation that branches of theoretical physics have become detached from the realities of experimental science. At stake is the integrity of the scientific method, as well as the reputation of science among the general public, say the workshop’s organizers.
Held at the Ludwig Maximilian University of Munich in Germany on December 7-9, the workshop came about as a result of an article in Nature a year ago, in which cosmologist George Ellis, of the University of Cape Town in South Africa, and astronomer Joseph Silk, of Johns Hopkins University in Baltimore, Maryland, lamented a “worrying turn” in theoretical physics (G. Ellis and J. Silk Nature 516, 321–323; 2014).

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Image credit: CPEP (Contemporary Physics Education Project), NSF/DOE/LBNL.

The Universe we know and love — with Einstein’s General Relativity as our theory of gravity and quantum field theories of the other three forces — has a problem that we don’t often talk about: it’s incomplete, and we know it. Einstein’s theory on its own is just fine, describing how matter-and-energy relate to the curvature of space-and-time. Quantum field theories on their own are fine as well, describing how particles interact and experience forces. Normally, the quantum field theory calculations are done in flat space, where spacetime isn’t curved. We can do them in the curved space described by Einstein’s theory of gravity as well (although they’re harder — but not impossible — to do), which is known as semi-classical gravity. This is how we calculate things like Hawking radiation and black hole decay.

But even that semi-classical treatment is only valid near and outside the black hole’s event horizon, not at the location where gravity is truly at its strongest: at the singularities (or the mathematically nonsensical predictions) theorized to be at the center. There are multiple physical instances where we need a quantum theory of gravity, all having to do with strong gravitational physics on the smallest of scales: at tiny, quantum distances. Important questions, such as:

What happens to the gravitational field of an electron when it passes through a double slit?
What happens to the information of the particles that form a black hole, if the black hole’s eventual state is thermal radiation?
And what is the behavior of a gravitational field/force at and around a singularity?

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These particle tracks from the CMS experiment at the LHC show two photons arising from a roughly 750-GeV particle created in a proton-proton collision. The event may represent a new particle beyond the Standard Model of physics.
Credit: CERN

The gigantic accelerator in Europe has produced hints of an exotic particle that defies the known laws of physics
By Clara Moskowitz on December 16, 2015

A little wiggle on a graph, representing just a handful of particles, has set the world of physics abuzz. Scientists at the Large Hadron Collider (LHC) in Switzerland, the largest particle accelerator on Earth, reported yesterday that their machine might have produced a brand new particle not included in the established laws of particle physics known as the Standard Model. Their results, based on the data collected from April to November after the LHC began colliding protons at nearly twice the energy of its previous runs, are too inconclusive to be sure—many physicists warned that the wiggle could just as easily represent a statistical fluke. Nevertheless, the finding has already spawned at least 10 new papers in less than a day proposing a theoretical explanation for the particle, and has the halls and blackboards of physics departments around the world churning.

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5 March 2015

Astronomers using the NASA/ESA Hubble Space Telescope have, for the first time, spotted four images of a distant exploding star. The images are arranged in a cross-shaped pattern by the powerful gravity of a foreground galaxy embedded in a massive cluster of galaxies. The supernova discovery paper will appear on 6 March 2015 in a special issue of Science celebrating the centenary of Albert Einstein’s theory of general relativity.

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03 December 2015

ESA's LISA Pathfinder lifted off earlier today on a Vega rocket from Europe's spaceport in Kourou, French Guiana, on its way to demonstrate technology for observing gravitational waves from space.

Gravitational waves are ripples in the fabric of spacetime, predicted a century ago by Albert Einstein's General Theory of Relativity, published on 2 December 1915.
Einstein's theory predicts that these fluctuations should be universal, generated by accelerating massive objects. However, they have not been directly detected to date because they are so tiny. For example, the ripples emitted by a pair of orbiting black holes would stretch a million kilometre-long ruler by less than the size of an atom.

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Black holes such as the one depicted in Interstellar (2014) can be connected by wormholes, which might have quantum origins.

Many physicists believe that entanglement is the essence of quantum weirdness — and some now suspect that it may also be the essence of space-time geometry.

Ron Cowen

16 November 2015

In early 2009, determined to make the most of his first sabbatical from teaching, Mark Van Raamsdonk decided to tackle one of the deepest mysteries in physics: the relationship between quantum mechanics and gravity. After a year of work and consultation with colleagues, he submitted a paper on the topic to the Journal of High Energy Physics.

In April 2010, the journal sent him a rejection — with a referee’s report implying that Van Raamsdonk, a physicist at the University of British Columbia in Vancouver, was a crackpot.

His next submission, to General Relativity and Gravitation, fared little better: the referee’s report was scathing, and the journal’s editor asked for a complete rewrite.

But by then, Van Raamsdonk had entered a shorter version of the paper into a prestigious annual essay contest run by the Gravity Research Foundation in Wellesley, Massachusetts. Not only did he win first prize, but he also got to savour a particularly satisfying irony: the honour included guaranteed publication in General Relativity and Gravitation. The journal published the shorter essay1 in June 2010.

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15. November 2015 von Markus Pössel in Astronomie, Kosmologie

Dieser Tage befinden wir uns mitten im 100jährigen Jubiläum von Albert Einsteins Allgemeiner Relativitätstheorie, also von Einsteins Theorie von Raum, Zeit und Gravitation. Wer meinen Jubiläumsvortrag dazu noch mitbekommen möchte, hat am 25. November in Berlin im Planetarium am Insulaner dazu Gelegenheit; in Heidelberg habe ich ihn letzte Woche bereits zweimal gehalten, und eine Hauptbotschaft bei meinem Überblick über die letzten hundert relativistischen Jahre lautet: Wo sich die Beobachter und Experimentatoren anfangs sehr abmühen mussten, um die von Einstein vorhergesagten Effekte wie Lichtablenkung im Schwerefeld oder Gravitations-Rotverschiebung nachzuweisen, sind dieselben Effekte heutzutage längst entweder Störeffekte bei anderen Messungen oder aber Werkzeuge, die sich beispielsweise für astronomische Messungen nutzen lassen.

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Abhay Ashtekar is a theoretical physicist and the founder of loop quantum gravity, an increasingly popular branch of physics that attempts to unify quantum mechanics with Albert Einstein’s theory of general relativity (which celebrates its centenary this year). Currently the Director of the Institute for Gravitational Physics and Geometry at Pennsylvania State University, Ashtekar spoke to Nithyanand Rao and Swetamber Das at IIT Madras on October 7, 2015 about his inspirations, his encounters with Subrahmanyan Chandrasekhar and Roger Penrose, work on gravity and cosmology, and his criticisms of string theory.

The freewheeling interview has been edited for clarity and divided into four parts:

Getting started on gravity and cosmology
Learning from Chandra
Challenges in loop quantum gravity
Arrogance in string theory

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