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Old October 21st, 2015, 06:08 PM
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Oxygen discovered on Rosetta comet, stunning scientists

By Michael Casey Published October 28, 2015

Artist impression of ESA's Rosetta approaching comet 67P/Churyumov-Gerasimenko. The comet image was taken on 2 August 2014 by the spacecraft's navigation camera at a distance of about 500 km. The spacecraft and comet are not to scale. (ESA/ATG medialab; Comet image: ESA/Rosetta/NAVCAM)

Scientists have for the first time detected oxygen on a comet, a finding that could upend theories about how the solar system was formed.

Reporting their findings in the journal Nature on Wednesday, an international team said that they detected “a lot” of molecular oxygen in the cloud of gas, or coma, surrounding the nucleus of comet 67P/Churyumov–Gerasimenko.

While molecular oxygen has been found in Jupiter and Saturn, it’s never been found on a comet. The neutral gas comas of most comets are composed largely of water, carbon monoxide and carbon dioxide.

“It is the most surprising discovery we have made so far in 67P because oxygen was not among the molecules suspected in a cometary comas,” Kathrin Altwegg, one of the co-authors on the paper from the University of Bern, told reporters during a press conference Tuesday.

“The first time we saw it I think we all went a little bit into denial because it was not expected to be found in a comet,” she said. “Molecular oxygen is very reactive. There was a lot of hydrogen around when the solar system was formed. Everybody and all models showed that molecular oxygen would react with the hydrogen and would no longer be present as molecular oxygen.”

Once they detected the oxygen, the researchers studied the comet for several months and concluded it was present “ in the whole body,” according to University of Michigan’s André Bieler, another co-author on the study.

“The fact that it’s in the whole body led us to the idea that it was primordial so the O2 must have been present at the formation of the comet,” Bieler said.

But how did it form and manage to stick around for billions of years?

Bieler said the international team considered two theories – either the oxygen was in the gaseous phase and endured a "shock freeze" or the oxygen was built onto the icy grains.

The researchers said the first theory was probably unlikely because “gaseous O2 has only been detected twice outside of our solar system.”

“If you freeze it out very slow in the grains it will react with hydrogen and transform into water ice,” Bieler said. "The other way to build up O2 is on these grains. We came up with the idea that it could happen through radiolysis, a common effect that is known in the solar system on other icy bodies and in the rings of Saturn.”

If the second theory holds up, Bieler said it would indicate that the comet was “a very pristine object.”

Ever since the Philae probe landed on the comet in November, scientists have made several startling discoveries. Through extensive data collected by the Rosetta spacecraft that is orbiting the comet, scientists have concluded that asteroids, not comets, may have provided most of Earth's water in the early years of the solar system. They also suggested the comet may host alien life.

Now, it could force scientists to reconsider how the solar system was formed.

Scientists have long theorized the solar system formed about 4.6 billion years ago when a cloud of stellar dust collapsed – possibly as the result of a star exploding nearby. It fell in on itself, creating a disk of material surrounding it. The pressure of all this material became so great that the hydrogen atoms fused into helium, releasing a tremendous amount of energy and forming our Sun.

"Our study merely suggests that our current models [of the solar system] most probably are not right," Bieler told FoxNews.com in an email.

"One thing that we challenge is the current idea that there is a lot of mixing going on in the protoplanetary disk during formation," he said. "In that case, a lot of material is transported inwards in the disk to regions closer to the (proto) sun. This can not have happened to the ice in 67P that now releases the O2."
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Last edited by Pete; October 29th, 2015 at 07:22 AM.
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Old November 25th, 2015, 09:02 AM
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The hunt for Albert Einstein's missing waves

By Rebecca Morelle Science Correspondent, BBC News

In the Italian countryside, not far from Pisa, a vast experiment is about to be switched on. If it's a success, one of Albert Einstein's greatest predictions will have been directly observed for the first time. If it fails, laws of physics might have to be reconsidered. The experiment is called Advanced Virgo, and it will be hunting for the most elusive of astrophysical phenomena. "Maybe we have the opportunity for the first time to detect gravitational waves on the Earth," explains Dr Franco Frasconi, from the University Pisa, who is part of Virgo's international team. "This would be a clear demonstration that what [Einstein] said 100 years ago is absolutely correct."

On 25 November 1915, Albert Einstein presented the final version of his field equations to the Prussian Academy of Sciences. They underpinned his Theory of General Relativity - a pillar of modern physics that has transformed our understanding of space, time and gravity.

From it, we have been able to understand so much - from the expansion of the Universe, to the motion of the planets and the existence of black holes.
But he also proposed the presence of gravitational waves, essentially ripples of energy that distort the fabric of space-time.
Think of them as a bit like the waves that radiate out when you throw a stone into a pond. Any object with mass should generate them when it's on the move. Even us. But the greater the mass, and more dramatic the motion, the larger the waves.

And Einstein predicted that the Universe was awash with them.

  • The waves are an inevitable consequence of the Theory of General Relativity
  • Their existence has been inferred by science but not yet directly detected
  • They are ripples in the fabric of space and time produced by violent events
  • Accelerating masses will produce waves that propagate at the speed of light
  • Detectable sources ought to include merging black holes and exploding stars
  • Virgo bounces laser beams down tunnels; the waves should disturb the light
  • Detecting the waves opens up the Universe to completely new investigations

But while astronomers have indirect evidence for their existence, getting a glimpse of these cosmic curiosities has not yet been possible.
Physicist Dr Toby Wiseman, from Imperial College London, UK, explained: "I'm not surprised we haven't directly seen gravity waves yet.
"Gravity is actually the most feeble of the forces and even dramatic astrophysical sources only emit weak gravity waves."
Now, in Italy, scientists hope to find them. But it won't be easy. The first incarnation of the Virgo experiment ran from 2007 - and didn't see anything. Neither did its US-counterpart, the Laser Interferometer Gravitational-Wave Observatory (Ligo). But both machines - called interferometers - are now undergoing expensive upgrades, and the teams hope major improvements in sensitivity could hold the key to success.

Dr Frasconi explained: "The technology available to detect gravitational waves is available just today. "During the last 10 years, we have developed very sophisticated technology to construct this kind of interferometer." The scientists are attempting to spot the tiny distortions created when gravitational waves pass through the Earth. They are hoping to see those emanating from violent cosmic events, such as exploding stars or colliding black holes.

The Virgo detector is formed of two identical 3km-tunnels, in a giant L-shape formation. A laser beam is generated, then split into two - with one half being fired along one tunnel, and the other half surging through the second tunnel. Mirrors at either end send the lasers travelling back and forth many times, before they are recombined. This might seem elaborate, but it takes advantage of a handy property of lasers - the fact that they are intense beams of light, and light is a wave. Imagine if two waves in the ocean crashed into each other, while one was at a peak, and one was at a trough - the waves would cancel each other out. The same is true inside the experiment. And if the waves have travelled exactly the same distance along the two tunnels, then they cancel each other out, producing no signal.

However, if a gravitational wave has travelled through the tunnel, it will very subtly distort its surroundings, changing the length of the tunnels by a minute amount - just a fraction of the width of an atom. And the way the waves move through space and time means that one tunnel would be stretched and one squeezed, which would result in one laser travelling a slightly longer distance while the other would have a shorter journey. As a result, the split beams will re-combine in a different way: the waves of light will interfere with each other, rather than cancelling out - and scientists will detect a signal.
Great efforts have been made to insulate the experiments from the general rumbles that pervade the Earth, from traffic noise to earthquakes.
"You are trying to a build a machine to avoid potential noise," says Dr Frasconi. "This machine is anchored directly on the ground floor - and the ground floor typically vibrates. The most important challenge is to isolate the mirrors. "For Virgo, this is the most important challenge. From the beginning we have spent a lot of time to develop the multistage pendulum to isolate the mirrors from seismic noise."

But even then, a signal in Italy will not be enough. If a gravitational wave is spotted there, the upgraded Advanced Ligo in America, which has the same set-up as Virgo, but is made up of two detectors with 4km-long arms, should also see the signal. So potentially should another, smaller experiment in Germany. Advanced Ligo is now up and running, and scientists hope Virgo will be ready to be switched on by the end of the year. The collaborating teams are so confident of success that they're forecasting that 1 January 2017 will be the day the breakthrough is made. This prediction may be a little tongue in cheek, but Dr Frasconi, who has been working in this field for two decades, is confident that the end of the search is near.
"Right now, it is extremely important to detect for the first time on Earth gravitational waves. Otherwise we do not have the right information, the right knowledge of the rest of the Universe."

  • A laser is fed into the machine and its light is split along two paths
  • The separate beams bounce back and forth between damped mirrors
  • Eventually, the two light paths are recombined and sent to a detector
  • Gravitational waves passing through the lab should disturb the set-up
  • Theory holds they should very subtly stretch and squeeze its space
  • This ought to show itself as a change in the lengths of the light arms
  • The photodetector hopes to capture this signal in the recombined beam

If the waves do not show up now it will mean that the experiments may need to be redesigned. And in the most extreme case, perhaps physicists might have to rethink the way that the Universe works. But a direct glimpse will open a new window on the cosmos - one that wouldn't have been possible without Einstein. Dr Wiseman, from Imperial College London, explains: "Seeing gravity waves would be fantastic confirmation of our understanding of general relativity. "We have good reason to think they exist, but we can't be sure we have understood general relativity correctly until we see these ripples in space and time directly. "Observing them would allow us new ways to test general relativity, but also give us an entirely new tool for observing some of the most fascinating objects in our Universe."

Developing general relativity

Bending Light

Eddington's photograph of a solar eclipse, which confirmed Einstein's theory that light "bends".

Sir Arthur Eddington

In the early years after Einstein's theory was published, Sir Arthur Eddington lent his considerable prestige in the British scientific establishment in an effort to champion the work of this German scientist. Because the theory was so complex and abstruse (even today it is popularly considered the pinnacle of scientific thinking; in the early years it was even more so), it was rumored that only three people in the world understood it. There was an illuminating, though probably apocryphal, anecdote about this. As related by Ludwik Silberstein, during one of Eddington's lectures he asked "Professor Eddington, you must be one of three persons in the world who understands general relativity." Eddington paused, unable to answer. Silberstein continued "Don't be modest, Eddington!" Finally, Eddington replied "On the contrary, I'm trying to think who the third person is."

In 1912, Einstein returned to Switzerland to accept a professorship at his alma mater, the ETH. Once back in Zurich, he immediately visited his old ETH classmate Marcel Grossmann, now a professor of mathematics, who introduced him to Riemannian geometry and, more generally, to differential geometry. On the recommendation of Italian mathematician Tullio Levi-Civita, Einstein began exploring the usefulness of general covariance (essentially the use of tensors) for his gravitational theory. For a while Einstein thought that there were problems with the approach, but he later returned to it and, by late 1915, had published his general theory of relativity in the form in which it is used today. This theory explains gravitation as distortion of the structure of spacetime by matter, affecting the inertial motion of other matter.

During World War I, the work of Central Powers scientists was available only to Central Powers academics, for national security reasons. Some of Einstein's work did reach the United Kingdom and the United States through the efforts of the Austrian Paul Ehrenfest and physicists in the Netherlands, especially 1902 Nobel Prize-winner Hendrik Lorentz and Willem de Sitter of Leiden University. After the war ended, Einstein maintained his relationship with Leiden University, accepting a contract as an Extraordinary Professor; for ten years, from 1920 to 1930, he travelled to Holland regularly to lecture.

In 1917, several astronomers accepted Einstein's 1911 challenge from Prague. The Mount Wilson Observatory in California, U.S., published a solar spectroscopic analysis that showed no gravitational redshift. In 1918, the Lick Observatory, also in California, announced that it too had disproved Einstein's prediction, although its findings were not published.

However, in May 1919, a team led by the British astronomer Arthur Stanley Eddington claimed to have confirmed Einstein's prediction of gravitational deflection of starlight by the Sun while photographing a solar eclipse with dual expeditions in Sobral, northern Brazil, and Príncipe, a west African island. Nobel laureate Max Born praised general relativity as the "greatest feat of human thinking about nature"; fellow laureate Paul Dirac was quoted saying it was "probably the greatest scientific discovery ever made". The international media guaranteed Einstein's global renown.

There have been claims that scrutiny of the specific photographs taken on the Eddington expedition showed the experimental uncertainty to be comparable to the same magnitude as the effect Eddington claimed to have demonstrated, and that a 1962 British expedition concluded that the method was inherently unreliable. The deflection of light during a solar eclipse was confirmed by later, more accurate observations. Some resented the newcomer's fame, notably among some German physicists, who later started the Deutsche Physik (German Physics) movement.

Last edited by Pete; November 28th, 2015 at 04:51 PM.
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Old March 14th, 2018, 03:17 AM
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World renowned physicist Stephen Hawking has died at the age of 76

World renowned physicist Stephen Hawking has died at the age of 76.

He died peacefully at his home in Cambridge in the early hours of Wednesday, his family said.

The Briton was known for his work with black holes and relativity, and wrote several popular science books including A Brief History of Time.

At the age of 22 Prof Hawking was given only a few years to live after being diagnosed with a rare form of motor neurone disease.

The illness left him in a wheelchair and largely unable to speak except through a voice synthesiser.

In a statement his children, Lucy, Robert and Tim, said: "We are deeply saddened that our beloved father passed away today.

"He was a great scientist and an extraordinary man whose work and legacy will live on for many years."

They praised his "courage and persistence" and said his "brilliance and humour" inspired people across the world.

"He once said, 'It would not be much of a universe if it wasn't home to the people you love.' We will miss him forever."

A book of condolence is due to be opened at Conville and Caius College in Cambridge, where Prof Hawking was a fellow.

Prof Hawking was the first to set out a theory of cosmology as a union of relativity and quantum mechanics.

He also discovered that black holes leak energy and fade to nothing - a phenomenon that would later become known as Hawking radiation.

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Old March 14th, 2018, 10:54 AM
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Rest in Peace Stephen Hawking
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