Albert Einstein ... a voice for the oppressed. Photograph: Corbis
From his radical thinking to his radical politics, his disavowal of celebrity to his wild hairstyle, the great physicist’s significance endures, argues his biographer
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Being in two places at the same time isn't easy for mere humans (Image: Chen Liu/EyeEm/Getty)
The same quirk of general relativity that means your head ages faster than your feet may mean we have to go to space to see large-scale quantum mechanics in action
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Aiming to make the first portrait of the hungry monster at the center of our galaxy, astronomers built “a telescope as big as the world.”
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The supermassive black hole in NGC 5813 has erupted at least three times, with the latest still occurring.
Chandra data show the supermassive black hole at the center of NGC 5813 has erupted multiple times over 50 million years. NGC 5813 is the central component of a group of galaxies called the NGC 5813 Group that is immersed in an enormous reservoir of hot gas.
Scientists discovered this history of black hole eruptions by studying the NGC 5813 Group, a group of galaxies about 105 million light-years from Earth. These Chandra observations are the longest ever obtained of a galaxy group, lasting for just over a week. The Chandra data are shown in this new composite image where the X-rays from Chandra (purple) have been combined with visible-light data (red, green, and blue).
Galaxy groups are like their larger cousins, galaxy clusters, but instead of containing hundreds or even thousands of galaxies like clusters do, galaxy groups are typically composed of 50 or fewer galaxies. Like galaxy clusters, groups of galaxies are enveloped by giant amounts of hot gas that emit X-rays.
The erupting supermassive black hole is located in the central galaxy of the NGC 5813 Group. The black hole’s spin, coupled with gas spiraling toward the black hole, can produce a rotating, tightly wound vertical tower of magnetic field that flings a large fraction of the inflowing gas away from the vicinity of the black hole in an energetic high-speed jet.
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An interview with theoretical physicist Lee Smolin.
In this book, Lee — always the optimist — made the prediction that
“We shall have the basic framework of the quantum theory of gravity by 2010, 2015 at the outside.”
When I visited Perimeter Institute some weeks ago I figured time had come to revisit this prediction.
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Sharpest View Ever of Star Formation in the Distant Universe
ALMA’s Long Baseline Campaign has produced a spectacular image of a distant galaxy being gravitationally lensed. The image shows a magnified view of the galaxy’s star-forming regions, the likes of which have never been seen before at this level of detail in a galaxy so remote. The new observations are far sharper than those made using the NASA/ESA Hubble Space Telescope, and reveal star-forming clumps in the galaxy equivalent to giant versions of the Orion Nebula in the Milky Way.
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Some physicists think they can explain why the universe first formed. If they are right, our entire cosmos may have sprung out of nothing at all.
People have wrestled with the mystery of why the universe exists for thousands of years. Pretty much every ancient culture came up with its own creation story - most of them leaving the matter in the hands of the gods - and philosophers have written reams on the subject. But science has had little to say about this ultimate question.
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Why is it you can break an egg, but not make the pieces spring back together again? To find out, we have to go back to the birth of the universe
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Physicists want to find a single theory that describes the entire universe, but to do so they must solve some of the hardest problems in science
The recent film The Theory of Everything tells the story of Stephen Hawking, who managed to become a world-famous physicist despite being confined to a wheelchair by a degenerative disease. It's mostly about his relationship with his ex-wife Jane, but it does find a bit of time to explain what Hawking has spent his career doing.
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An aerial view shows the LIGO Hanford facility near Richland, Washington.
After seven years of upgrades, the Advanced Laser Interferometer Gravitational Wave Observatories were dedicated on Tuesday at the LIGO Hanford facility near Richland, Washington.
The facilities are located amid the tumbleweeds of southeastern Washington and the pines of southeastern Louisiana. They're designed to detect the faint signature of gravitational waves given off by supernovas, black hole collisions and other cosmic crashes.
Albert Einstein's general theory of relativity predicts that such waves should exist, but they have never been detected directly. The Advanced LIGO experiment, funded by the National Science Foundation and operated by Caltech and MIT, is expected to change that. It could do for gravitational waves what Europe's Large Hadron Collider did for the equally elusive Higgs boson.
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photo credit: An artist's conception of a black hole binary in a heart of a quasar, with the data showing the periodic variability superposed / Santiago Lombeyda/Caltech Center for Data-Driven Discovery
An unusual, repeating light signal in the distance may be coming from the final stages of a merger between two supermassive black holes. At just a few hundredths of a light-year apart, they could be merging in a mere one million years. An event like this has been predicted based on theory, but has never been observed before, according to a new study published in Nature this week.
The supermassive black holes at the center of most large galaxies (including ours) appear to co-evolve with their host galaxies: As galaxies merge, their black holes grow more massive too. Since we can’t actually see black holes, researchers look for their surrounding bands of material called accretion disks, which are produced by the intense pull of the black hole’s gravity. The disks of supermassive black holes can release vast amounts of heat, X-rays, and gamma rays that result in a quasar—one of the most luminous objects in the universe.
Caltech’s Matthew Graham and colleagues noticed the light signal coming from quasar PG 1302-102 while studying variability in quasar brightness using data from the Catalina Real-Time Transient Survey, which continuously monitored 500 million celestial light sources across 80 percent of the sky with three ground telescopes.
Ancient ripples in the fabric of the space square off against soot in the galaxy
NOT-SO-CLEAR SKIES The signal that BICEP2 researchers interpreted as gravitational waves may be due to interstellar dust. The Planck satellite mapped dust in the entire sky. The map shows the sky above the plane of the Milky Way (left) and below the galaxy’s plane (right). Planck found areas heavily contaminated by dust (red) and regions that are relatively clean (blue). The black box shows where BICEP2 searched for gravitational waves.
Gravitational waves from the Big Bang captured worldwide attention in 2014. But then interstellar dust clouds stole
the show.
Detection of such waves — ripples in the fabric of space — would be direct evidence for the theory of cosmological inflation, a brief epoch immediately after the Big Bang when the visible universe abruptly swelled to at least 1075 times its initial volume.
In March, astrophysicists thought they had captured their elusive gravitational wave quarry. Researchers with the BICEP2 project reported swirling patterns in the alignment of electromagnetic waves in the cosmic microwave background, or CMB, the primordial light released into the universe about 380,000 years after the Big Bang (SN: 4/5/14, p. 6). Those patterns supposedly reflected the influence of gravitational waves launched during the epoch of inflation.
(a) Scheme of the experiment. (b) Gravitational acceleration along the symmetry axis (az) produced by the source masses and the Earth’s gravity gradient. Credit: Phys. Rev. Lett. 114, 013001
A team of researchers working in Italy has successfully conducted an experiment to directly measure gravity's curvature for the first time. In their paper published in the journal Physical Review Letters, the team describes their work and note that what they have accomplished could lead to an improvement in G, the Newtonian constant of gravity.
Over many years, scientists have developed more sophisticated ways to measure gravity, one of the latest is to use atom interferometry—it enables distance measurement with very high precision and works by exploiting the quantum-mechanical wavelike nature of atoms. Up till now researchers have been able to measure the changes in gravity as altitude increases, for heights as little as a few feet, creating a gradient. In this new research the team has found a way to measure the change in gravity that is produced by a large mass. This change in the gradient is known as gravity's curvature.
ONE of the defining anniversaries in 2015 will be the centenary of general relativity. In 1915, Einstein published a set of equations that changed our understanding of the universe. Out went the Newtonian notion of gravity as a force between massive objects; in came the counter-intuitive idea that gravity is a property of the universe, with massive objects curving space-time.
A century on, gravity continues to challenge us. The equations predict that cataclysmic cosmic events should send ripples through space-time, but we have yet to observe any. This year will see two projects aimed at sorting this out: the resumption of a gravitational-wave experiment called LIGOMovie Camera and the launch of a spacecraft called LISA Pathfinder that will test technology for catching the waves in space.
We may even see progress on the biggest unresolved issue of all – the incompatibility of relativity and quantum theory. At the atomic scale, gravity is so weak we routinely ignore it. Now it seems we are wrong to do so (see "Gravity's secret: How relativity meets quantum physicsMovie Camera"). Gravity might play a crucial role in the quantum world. It might be the secret ingredient of reality. We won't get full answers this year, but relativity's greatest remaining puzzle looks to be on its way to being solved, at last.
Artist's impression of a pulsar, including the extreme magnetic field surrounding the dense stellar object. Credit: NASA
For the first time, the mass of a binary pulsar pair has been precisely measured, but it was a race against time before the extreme gravitational warping of spacetime caused one of the dense objects to blip out of view.
Pulsars are rapidly-spinning neutron stars that generate powerful beams of radiation from their poles. Neutron stars are the stellar husks of long-dead stars that ran out of hydrogen fuel and collapsed under gravity to create a mass of degenerate matter.
