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rynner2Offline
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PostPosted: 07-05-2014 20:56    Post subject: Reply with quote

Universe evolution recreated in lab
By Pallab Ghosh, Science correspondent, BBC News
[Video: Pallab Ghosh explains the significance of the visual simulation]

An international team of researchers has created the most complete visual simulation of how the Universe evolved.
The computer model shows how the first galaxies formed around clumps of a mysterious, invisible substance called dark matter.
It is the first time that the Universe has been modelled so extensively and to such great resolution.
The research has been published in the journal Nature.

The simulation will provide a test bed for emerging theories of what the Universe is made of and what makes it tick.

One of the world's leading authorities on galaxy formation, Professor Richard Ellis of the California Institute of Technology (Caltech) in Pasadena, described the simulation as "fabulous".
"Now we can get to grips with how stars and galaxies form and relate it to dark matter," he told BBC News.

The computer model draws on the theories of Professor Carlos Frenk of Durham University, UK, who said he was "pleased" that a computer model should come up with such a good result assuming that it began with dark matter.
"You can make stars and galaxies that look like the real thing. But it is the dark matter that is calling the shots".

Cosmologists have been creating computer models of how the Universe evolved for more than 20 years. It involves entering details of what the Universe was like shortly after the Big Bang, developing a computer program which encapsulates the main theories of cosmology and then letting the programme run.
The simulated Universe that comes out at the other end is usually a very rough approximation of what astronomers really see.
The latest simulation, however, comes up with the Universe that is strikingly like the real one.

Immense computing power has been used to recreate this virtual Universe. It would take a normal laptop nearly 2,000 years to run the simulation. Shocked However, using state-of-the-art supercomputers and clever software called Arepo, researchers were able to crunch the numbers in three months.

In the beginning, it shows strands of mysterious material which cosmologists call "dark matter" sprawling across the emptiness of space like branches of a cosmic tree. As millions of years pass by, the dark matter clumps and concentrates to form seeds for the first galaxies.
Then emerges the non-dark matter, the stuff that will in time go on to make stars, planets and life emerge.

But early on there are a series of cataclysmic explosions when it gets sucked into black holes and then spat out: a chaotic period which was regulating the formation of stars and galaxies. Eventually, the simulation settles into a Universe that is similar to the one we see around us.

According to Dr Mark Vogelsberger of Massachusetts Institute of Technology (MIT), who led the research, the simulations back many of the current theories of cosmology.
"Many of the simulated galaxies agree very well with the galaxies in the real Universe. It tells us that the basic understanding of how the Universe works must be correct and complete," he said.
In particular, it backs the theory that dark matter is the scaffold on which the visible Universe is hanging.
"If you don't include dark matter (in the simulation) it will not look like the real Universe," Dr Vogelsberger told BBC News.

The simulation is the first to show visible matter emerging from dark matter. It will also help cosmologists learn more about another mysterious force called dark energy that is powering the continued acceleration of the Universe.
The European Space Agency (Esa) is planning to launch a spacecraft called Euclid in 2020 to measure the acceleration of the Universe. Accurate simulations, such as the one published today, will help in that search, according to Dr Joanna Dunkley, of Oxford University.
"In order to use the data from Euclid we will need to simulate what we expect to see for dark energy and compare it with what we see," she said.

Cosmologist Dr Robin Catchpole of the Institute of Astronomy in Cambridge, added a note of caution, however.
Although he hailed the simulation as "spectacular", he added, "one must not be taken in by the sheer visual beauty of the thing. You get things that look like galaxies without them being much to do with the physics of how galaxies emerged".

http://www.bbc.co.uk/news/science-environment-27299017

(FWIW, I've actually met Dr. Joanna Dunkley! Astrophysicists and policemen all look so young to me now... Sad )
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SameOldVardoger
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PostPosted: 08-05-2014 12:28    Post subject: Reply with quote

What if life occured on the planets of the stars in those simulated galaxies. Would it be ethical to turn off the simulation?

gaga
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rynner2Offline
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PostPosted: 08-05-2014 13:01    Post subject: Reply with quote

SameOldVardoger wrote:
What if life occured on the planets of the stars in those simulated galaxies. Would it be ethical to turn off the simulation?

I doubt if the simulation went down to the scale of planets, let alone their near-surface chemical properties! Too much detail to handle - you wouldn't see the wood for the trees. I don't think we're into Matrix territory yet!

I'd guess they worked with a minimum mass limit they'd handle, perhaps that of dwarf stars or giant planets.
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PeteByrdieOffline
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PostPosted: 08-05-2014 17:07    Post subject: Reply with quote

SameOldVardoger wrote:
What if life occured on the planets of the stars in those simulated galaxies. Would it be ethical to turn off the simulation?

gaga


Yes! After tinkering with their worlds for our own twisted amusement. Muahahaha!

But I suspect we'll far sooner face the same question about self-conscious machines. We even debate at length the ethics of animal welfare. How long will it be before a machine can be shown to be as conscious and feeling as a crow, cat or Daily Mail reader?Shocked Surely, it's no more than a decade away.
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Stu73Offline
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PostPosted: 09-05-2014 09:40    Post subject: Reply with quote

Quote:
How long will it be before a machine can be shown to be as conscious and feeling as a crow, cat or Daily Mail reader?


Crows and Cats can be said to be intelligent creatures with the ability to learn from their experiences and environment?? Daily Mail readers on the other hand.........................
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rynner2Offline
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PostPosted: 20-06-2014 07:45    Post subject: Reply with quote

rynner2 wrote:
Cosmic inflation: 'Spectacular' discovery hailed
By Jonathan Amos, Science correspondent, BBC News

Scientists say they have extraordinary new evidence to support a Big Bang Theory for the origin of the Universe.
Researchers believe they have found the signal left in the sky by the super-rapid expansion of space that must have occurred just fractions of a second after everything came into being.
It takes the form of a distinctive twist in the oldest light detectable with telescopes.
The work will be scrutinised carefully, but already there is talk of a Nobel.

http://www.bbc.co.uk/news/science-environment-26605974

That was in March. Now they're not so sure...

Cosmic inflation: Confidence lowered for Big Bang signal
By Jonathan Amos, Science correspondent, BBC News

Scientists who claimed to have found a pattern in the sky left by the super-rapid expansion of space just fractions of a second after the Big Bang say they are now less confident of their result.
The BICEP2 Collaboration used a telescope at the South Pole to detect the signal in the oldest light it is possible to observe.
At the time of the group's announcement in March, the discovery was hailed as a near-certain Nobel Prize.

But the criticism since has been sharp.
Rival groups have picked holes in the team's methods and analysis.

On Thursday, the BICEP2 collaboration formally published its research in a peer reviewed journal - Physical Research Letters (PRL).
In the paper, the US-led group stands by its work but accepts some big questions remain outstanding.

And addressing a public lecture in London, one of BICEP2's principal investigators acknowledged that circumstances had changed.
"Has my confidence gone down? Yes," Prof Clem Pryke, from the University of Minnesota, told his audience.

What the team announced at its 17 March press conference was the long sought evidence for "cosmic inflation".
Developed in the 1980s, this is the idea that the Universe experienced an exponential growth spurt in its first trillionth of a trillionth of a trillionth of a second.
It helps explain why deep space looks the same on all sides of the sky - the contention being that a very rapid expansion early on could have smoothed out any unevenness.

Inflation theory makes a very specific prediction - that it would have been accompanied by waves of gravitational energy, and that these ripples in the fabric of space-time would leave an indelible mark on the oldest light in the sky - the famous Cosmic Microwave Background.
The BICEP team claimed to have detected this signal. It is called B-mode polarisation and takes the form of a characteristic swirl in the directional properties of the CMB light.

It is, though, an extremely delicate pattern and must not be confused with the same polarisation effects that can be generated by nearby dust in our galaxy.
The critiques that have appeared since March have largely focused on this issue. And they intensified significantly when some new information describing dust polarisation in the Milky Way was released by scientists working on the European Space Agency's orbiting Planck telescope.

Planck, which everyone agrees is extremely powerful at characterising dust, will release further data before the end of the year. And, very significantly, this will include observations made in the same part of the sky as BICEP2's telescope.

Until then, or until new data emerges from other sources, the BICEP2 collaboration recognises that its inflation detection has greater uncertainty attached to it.
"[Our] models are not sufficiently constrained by external public data to exclude the possibility of dust emission bright enough to explain the entire excess signal," it writes in the PRL paper.

At his lecture at University College London, Prof Pryke explained his team's lowered confidence: "Real data from Planck are indicating that our dust models are underestimates. So the prior knowledge on the level of dust at these latitudes, in our field, has gone up; and so the confidence that there is a gravitational wave component has gone down. Quantifying that is a very hard thing to do. But data trumps models."

Prof Pryke spoke of the pressure he and his colleagues had been under since March. He said he never expected there would be such interest in their work, especially from mainstream media.
"I'm feeling like I'm at the eye of the storm," he told me.
"Look, the scientific debate has come down to this - we need more data. With the existing data that's out there, you can generate a lot of farce, a lot of blog posts, a lot of excitement and controversy, but you can't really answer the question scientifically. So, what you need is more data, and that's coming from Planck and it's coming from us."

Prof Marc Kamionkowski, from Johns Hopkins University, commented that what we were witnessing currently was "science in action".
"If it was not such an exciting result, you would not be hearing so much about it," he said in a phone conversation last week.
"We're going to need confirmation by independent groups. That's the way things work in science. We don't believe things because somebody says they're true; we believe them because different people make the measurements independently and find the same results."

http://www.bbc.co.uk/news/science-environment-27935479
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rynner2Offline
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PostPosted: 01-07-2014 09:52    Post subject: Reply with quote

The Large Hadron Collider will soon be up and running again. This is part of an article about that which discusses an interesting aspect of the Higgs Boson:

-----------------------------------------------------------------------------------

Particle physicists have learnt more about the Higgs boson's behaviour and how well it conforms to predictions. In a paper published last week in the journal Nature Physics, researchers outlined how they have watched the Higgs decay into the particles that make up matter (known as fermions), in addition to those that convey force (bosons), which had already been observed.

This is exactly as the Standard Model predicts. Physicists know that this framework, devised in the 1970s, must be a stepping stone to a deeper understanding of the cosmos. But so far, it's standing up exceptionally well. Searches at the LHC for deviations from this elegant scheme - such as evidence for new, exotic particles - have come to nothing.

At ICHEP [International Conference on High Energy Particles], other scientists are expected to outline details of a refined mass for the fundamental particle, which has been measured at approximately 125 gigaelectronvolts (GeV). For those outside the particle physics community, this might seem like a minor detail. But the mass of the Higgs is more than a mere number.

There's something very curious about its value that could have profound implications for the Universe. Mathematical models allow for the possibility that our cosmos is long-lived yet not entirely stable, and may - at some indeterminate point - be destroyed.
"The overall stability of the Universe depends on the Higgs mass - which is a bit funny," said Prof Jordan Nash, a particle physicist from Imperial College London, who works on the CMS experiment at Cern.
"There's a long theoretical argument which I won't go into, but that value is intriguing in that it sits on the edge between what we think is the long-term stability of the Universe and a Universe that has a finite lifetime."

To use an analogy, imagine the Higgs boson is an object resting at the bottom of a curved slope. If that resting place really is the lowest point on the slope, then the vacuum of space is completely stable - in other words, the Higgs is in the lowest energy state and can go no further.
However, if at some point further along this slope, there's another dip, the potential exists for the Universe to "topple" into this lower energy state, or minimum. If that happens, the vacuum of space collapses, dooming the cosmos. Shocked

"The Higgs mass is in that place where it gets interesting, where it's no longer guaranteed that there are no other minima," Prof Nash, who works on the CMS experiment at Cern, told the BBC. But there's no need to worry, the models suggest such a rare event would not occur for a very, very long time - many times further into the future, in fact, than the current age of the Universe.

This idea of a finite lifetime for the cosmos is dependent on the Standard Model being the ultimate scheme in physics. But there is much in the Universe - gravitation and dark matter, for example - that the Standard Model can't fully explain, so there are reasons to think that's not the case.

The existence of exotic particles, such as those predicted by the theory known as supersymmetry, would shore up the stability of the Universe in those mathematical models.
But as previously mentioned, searches for these particles, called superpartners, have so far drawn a blank, as have attempts to detect dark matter, extra dimensions, and other phenomena beyond the Standard Model. Hopes that the LHC would allow scientists to lift the veil on a whole new realm of physics have proved optimistic, at least during its initial run.

Some versions of supersymmetry have already been all but ruled out by the LHC. But the theory has many forms, depending on how you tweak the mathematical parameters.
"From the theory community's point of view, this is all very interesting because it fleshes out much better what the first run of the LHC has excluded," said Prof Dave Charlton, who leads the Atlas experiment at Cern.
"Therefore, it better establishes where we should be looking for new signals next year."
Assuming the theorists are indeed correct, supersymmetry will have to wait some time longer for its big reveal.

Other hypothesised particles, such as the W prime and Z prime bosons could possibly be detected soon after the LHC returns to particle smashing.
For now, all eyes are on the engineers at Cern....

http://www.bbc.co.uk/news/science-environment-28089987
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PeteByrdieOffline
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PostPosted: 02-07-2014 18:59    Post subject: Reply with quote

Quote:
Fluid Tests Hint at Concrete Quantum Reality

For nearly a century, “reality” has been a murky concept. The laws of quantum physics seem to suggest that particles spend much of their time in a ghostly state, lacking even basic properties such as a definite location and instead existing everywhere and nowhere at once. Only when a particle is measured does it suddenly materialize, appearing to pick its position as if by a roll of the dice.

This idea that nature is inherently probabilistic — that particles have no hard properties, only likelihoods, until they are observed — is directly implied by the standard equations of quantum mechanics. But now a set of surprising experiments with fluids has revived old skepticism about that worldview. The bizarre results are fueling interest in an almost forgotten version of quantum mechanics, one that never gave up the idea of a single, concrete reality.

The experiments involve an oil droplet that bounces along the surface of a liquid. The droplet gently sloshes the liquid with every bounce. At the same time, ripples from past bounces affect its course. The droplet’s interaction with its own ripples, which form what’s known as a pilot wave, causes it to exhibit behaviors previously thought to be peculiar to elementary particles — including behaviors seen as evidence that these particles are spread through space like waves, without any specific location, until they are measured.

Particles at the quantum scale seem to do things that human-scale objects do not do. They can tunnel through barriers, spontaneously arise or annihilate, and occupy discrete energy levels. This new body of research reveals that oil droplets, when guided by pilot waves, also exhibit these quantum-like features.

To some researchers, the experiments suggest that quantum objects are as definite as droplets, and that they too are guided by pilot waves — in this case, fluid-like undulations in space and time. These arguments have injected new life into a deterministic (as opposed to probabilistic) theory of the microscopic world first proposed, and rejected, at the birth of quantum mechanics.

“This is a classical system that exhibits behavior that people previously thought was exclusive to the quantum realm, and we can say why,” said John Bush, a professor of applied mathematics at the Massachusetts Institute of Technology who has led several recent bouncing-droplet experiments. “The more things we understand and can provide a physical rationale for, the more difficult it will be to defend the ‘quantum mechanics is magic’ perspective.”


There's a vast amount of text on the site, far more than is worth pasting here. There are elements of science politics in there. It's hard for those of us who have got used to a quantum universe to accept all that weirdness can be somehow accounted for by fluid dynamics. Really? A century of quantum uncertainty could be obliterated by what appears to be an analogy to the classical physics? For me, exciting and unconvincing, in equal measure.
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PostPosted: 03-07-2014 11:28    Post subject: Reply with quote

I'm sure they're smarter than I am and have considered it, but what about when the surface is infinite in size and the waves aren't bouncing back from the container walls?
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rynner2Offline
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PostPosted: 03-07-2014 14:30    Post subject: Reply with quote

PeteByrdie wrote:
Quote:
Fluid Tests Hint at Concrete Quantum Reality


There's a vast amount of text on the site, far more than is worth pasting here. There are elements of science politics in there. It's hard for those of us who have got used to a quantum universe to accept all that weirdness can be somehow accounted for by fluid dynamics. Really? A century of quantum uncertainty could be obliterated by what appears to be an analogy to the classical physics? For me, exciting and unconvincing, in equal measure.

Thanks for posting that. A good overview of the history of the subject, and how its problems have been dealt with (or swept under the carpet Wink )

It was good to encounter again Einstein's dictum that God does not play dice!", and Bohr's response: "Stop telling God what to do!" Cool

Good too to hear about Bohm again, and his pilot-wave theory. He was once seen as a big name, but has since dwindled into obscurity.

And I didn't know (or had since forgotten) that "Bell supported pilot-wave theory."

Quote:
There's a vast amount of text on the site, far more than is worth pasting here.

It's all worth posting, though it's length is perhaps beyond the concentration levels of many here. But those interested might like to break it into chunks, read a chunk at a time, and then think about it for a while before tackling the next chunk.

I was always interested in alternative explanations - Copenhagen's "collapse of the wave function" always seemed too undefined and irrational to be satisfactory. I'm glad to hear that people are still exploring alternative views. Very Happy
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PostPosted: 03-07-2014 17:37    Post subject: Reply with quote

I have always been extremely excited by weird quantum wave properties, and will be sad if further research dissipates some of the magic. But it would be satisfying to see quantum theory dragged into the classical physics realm. And I was also pleased to see Bohm's name attached to the pilot-wave idea, rather than it being touted as something new. And also Bohr's much more clever but less often quoted response to Einstein's comment.

As I was typing this, Sheldon Cooper on TV said something like, 'I love quantum physics. It's like looking at the Universe naked.' Just a coincidence, but a fun one.
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