Big Bang: unexpected discovery

An unexpected discovery may see physicists heading back to the drawing board in order to update models representing the Universe immediately after the Big Bang. In an experiment not previously possible, physicists have created the state of matter thought to have filled the Universe just a few microseconds after the Big Bang. To their astonishment, physicists found that instead of a gas, the substance was more like a liquid. Understanding why it is a liquid should take physicists a step closer to explaining the earliest moments of our Universe.

The liquid is said to exhibit characteristics like nothing else physicists have observed before, and its collective movement is rather like the way a school of fish swims "as one". In fact, physicists' tentative calculations suggest that its extraordinarily low viscosity makes it the most perfect fluid ever created.

The new state of matter was forged in the Relativistic Heavy Ion Collider, situated at the Brookhaven National Laboratory. Colliding the central cores of gold atoms together, head-on at almost the speed of light, the researchers created a fleeting, microscopic version of the Universe a few microseconds after the Big Bang. This included achieving a temperature of several million million degrees (about 150,000 times the temperature at the center of the Sun). They then detected and analyzed the explosive rush of particles that this miniature Big Bang created. Researchers had confidently believed that they would observe something like "steam", made up of free quarks and gluons, but instead the researchers saw evidence of collective movement as the hot matter flowed out of the collision site. This indicated stronger interactions between the particles than expected, leading to the belief that the quark-gluon plasma is similar to a liquid.

This latest development is much more unusual than anyone expected. "No one predicted that it would be a liquid," said Professor John Nelson from the University of Birmingham, who heads the British involvement in the multinational experiment.

"This aspect was totally unexpected and will lead to new scientific research regarding the properties of matter at extremes of temperature and density, previously inaccessible in a laboratory."

The liquid defies physicists' current understanding of how matter in the universe behaved microseconds after the Big Bang. According to previous models there should be no evidence of matter - as we know it - in existence mere microseconds after the big bang, because the extreme temperatures generated would have been far to high for any matter to exist. There is a suggestion that certain versions of string theory may be able to explain the liquid behavior of the quark-gluon plasma. "Although these findings did not fit with expectations, the theories are slowly coming into line," said Nelson.

[Based on scienceagogo]

[Picture from Brookhaven National Laboratory]

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MythBusters Spoof - Time Travel

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Hidden variables of reality

Returning to Einstein's nagging doubts about quantum mechanics, Nobel laureate Gerard 't Hooft of Utrecht University has begun to outline a way in which its apparent play of chance might be underpinned by precise physical laws that describe the way the world works.

Despite being physicists' most fundamental theory of the properties of matter and energy, quantum mechanics holds that there are things we just cannot know. For example, it forbids us from knowing everything about a subatomic particle: its exact speed, position, mass and energy. We can only put limits on the probable values of all these things at any instant.

Albert Einstein did not like this idea, and suspected that another theory - another layer of reality - might underlie quantum mechanics, in which everything is spelled out precisely. These deeper properties of objects became known as 'hidden variables'. According to this view, our ignorance about the nature of a quantum object is illusory; we just haven't found the right theory to describe it yet.

Today, most physicists adhere to a different reading of quantum theory, called the Copenhagen Interpretation, as advocated by the Danish nuclear physicist of the 1940s, Niels Bohr. This says that there is no deeper reality, that hidden variables don't exist and that the world is simply probabilistic. It holds that we are not ignorant about quantum objects, it's just that there is nothing further to be known.

Indeed, in the 1980s, the Copenhagen Interpretation was put to an experimental test based on a theorem devised by the Irish physicist John Bell - and it stood up. Hidden variables had to go.

't Hooft is not about to resurrect hidden variables. But neither is he convinced that quantum uncertainty has to be the final word. "Contrary to common belief," he says, "it is not difficult to construct deterministic models where quantum mechanics correctly describes stochastic behaviour, in precise accordance with the Copenhagen doctrine."

Here, stochastic means that things seem governed by fuzzy, rather than precise, probabilities. And deterministic means that one thing leads definitely to another, not simply to a range of other things with various probabilities.

"The key, " says 't Hooft, "is information loss. At the smallest conceivable size scale - the Planck Scale, many trillions of times smaller than the nucleus of an atom - there exists complete information about the world. This information gets lost very quickly. By the time we start trying to probe and measure a system, we are like archaeologists trying to make sense of ancient Babylonia: we have only the scantiest of information to go on. We can say only what the system was probably like."

This might sound like sleight of hand to introduce quantum uncertainty, but 't Hooft has outlined a way to turn it into a predictive mathematical theory. But because the Planck Scale is so far below the resolution limit of any conceivable experiment using current technology, it will be very difficult to put his ideas to the test. Richard Gill, who is also based at Universty of Utrecht suspects that the real answer may turn out to be eternally elusive.

"Perhaps, " he speculates, "the world was built according to quantum mechanics but quantum mechanics itself prevents us from ever being sure."

[Based on Nature, picture from Membrana]

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