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Profile tullio
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Message 1735150 - Posted: 18 Oct 2015, 10:10:43 UTC - in response to Message 1735132.  

The only advice I give to you is to read the book by Carlo Rovelli,a theoretical physicst working at Marseille on quantum loop gravity. He has a written a book "Seven short lessons in physics", which has had an English edition published by Penguin in the UK and shall be published soon also in the USA. He is better at explaining modern physics than I am.
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Message 1735165 - Posted: 18 Oct 2015, 13:29:17 UTC - in response to Message 1735150.  

The only advice I give to you is to read the book by Carlo Rovelli,a theoretical physicst working at Marseille on quantum loop gravity. He has a written a book "Seven short lessons in physics", which has had an English edition published by Penguin in the UK and shall be published soon also in the USA. He is better at explaining modern physics than I am.
Tullio

A tiny, 83-page book about some of the basic principles of physics has been a surprise hit in Italy – becoming the single bestselling book of any kind to be published in the country this year.
Here is some extracts.
http://www.sevenbrieflessons.com/
Carlo Rovelli discusses his ‘Seven Brief Lessons on Physics’
http://blog.physicsworld.com/2015/09/29/carlo-rovelli-discusses-his-seven-brief-lessons-on-physics/
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Message 1735169 - Posted: 18 Oct 2015, 13:46:45 UTC

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Message 1735363 - Posted: 19 Oct 2015, 6:51:13 UTC

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Message 1736119 - Posted: 22 Oct 2015, 3:53:51 UTC
Last modified: 22 Oct 2015, 3:54:32 UTC

"Nature" magazine says that USA nuclear physics is focussing on neutrino physics by designing a large detector capable of observing the neutrinoless double Beta decay. This to check if neutrinos are their own antiparticles. The idea goes back to Ettore Majorana, the physicist of the Fermi team who disappeared in 1938.
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Message 1736131 - Posted: 22 Oct 2015, 4:22:38 UTC

Reuters - Einstein wouldn't like it: New test proves universe is "spooky"

Writing in the journal Nature, researchers detailed an experiment showing how two electrons at separate locations 1.3 km (0.8 mile) apart on the Delft University of Technology campus demonstrated a clear, invisible and instantaneous connection.
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Message 1736163 - Posted: 22 Oct 2015, 8:23:39 UTC - in response to Message 1736131.  

How did they sync their clocks and get around the uncertainty principle ?
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Message 1736182 - Posted: 22 Oct 2015, 10:29:32 UTC - in response to Message 1736131.  
Last modified: 22 Oct 2015, 10:40:20 UTC

Reuters - Einstein wouldn't like it: New test proves universe is "spooky"
Writing in the journal Nature, researchers detailed an experiment showing how two electrons at separate locations 1.3 km (0.8 mile) apart on the Delft University of Technology campus demonstrated a clear, invisible and instantaneous connection.

Actually the test was about confirming older tests and close loopholes.
http://www.forbes.com/sites/chadorzel/2015/08/27/new-experiment-closes-quantum-loopholes-confirms-spookiness/
Experimental loophole-free violation of a Bell inequality using entangled electron spins separated by 1.3 km
For more than 80 years, the counterintuitive predictions of quantum theory have stimulated debate about the nature of reality. In his seminal work, John Bell proved that no theory of nature that obeys locality and realism can reproduce all the predictions of quantum theory. Bell showed that in any local realist theory the correlations between distant measurements satisfy an inequality and, moreover, that this inequality can be violated according to quantum theory. This provided a recipe for experimental tests of the fundamental principles underlying the laws of nature. In the past decades, numerous ingenious Bell inequality tests have been reported. However, because of experimental limitations, all experiments to date required additional assumptions to obtain a contradiction with local realism, resulting in loopholes. Here we report on a Bell experiment that is free of any such additional assumption and thus directly tests the principles underlying Bell's inequality. We employ an event-ready scheme that enables the generation of high-fidelity entanglement between distant electron spins. Efficient spin readout avoids the fair sampling assumption (detection loophole), while the use of fast random basis selection and readout combined with a spatial separation of 1.3 km ensure the required locality conditions. We perform 245 trials testing the CHSH-Bell inequality S≤2 and find S=2.42±0.20. A null hypothesis test yields a probability of p=0.039 that a local-realist model for space-like separated sites produces data with a violation at least as large as observed, even when allowing for memory in the devices. This result rules out large classes of local realist theories, and paves the way for implementing device-independent quantum-secure communication and randomness certification.


Six Things Everyone Should Know About Quantum Physics
http://www.forbes.com/sites/chadorzel/2015/07/08/six-things-everyone-should-know-about-quantum-physics/
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Message 1736197 - Posted: 22 Oct 2015, 13:04:34 UTC - in response to Message 1736163.  
Last modified: 22 Oct 2015, 13:05:36 UTC

How did they sync their clocks and get around the uncertainty principle ?

You don't measure time and position in these experiments.
You observe how entangled photons scatters.
Each individual photon scatters in a random direction, yet the random direction one photon takes is related to the random direction its partner does. The gammas act in synchrony. How can they do that, if they're truly random?

How to Build Your Own Quantum Entanglement Experiment
http://blogs.scientificamerican.com/critical-opalescence/how-to-build-your-own-quantum-entanglement-experiment-part-1-of-2/
http://blogs.scientificamerican.com/critical-opalescence/how-to-build-your-own-quantum-entanglement-experiment-part-2-of-2/
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Message 1736200 - Posted: 22 Oct 2015, 13:13:21 UTC

I had read in "Nature" about this experiment. Let me try to remember. Two electrons in two crystals at a distance of 1.3 km emit a photon. If the two photons arrive at the same time to a detector placed about half way, they become entangled. But this entangles also the electrons, and the value of their spin,up or down.
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Message 1736213 - Posted: 22 Oct 2015, 13:59:26 UTC - in response to Message 1736200.  
Last modified: 22 Oct 2015, 14:09:51 UTC

I had read in "Nature" about this experiment. Let me try to remember. Two electrons in two crystals at a distance of 1.3 km emit a photon. If the two photons arrive at the same time to a detector placed about half way, they become entangled. But this entangles also the electrons, and the value of their spin,up or down.
Tullio

I think it's the other way around.
The photon source in the middle and the detectors in the ends.

Schematic of the third Aspect experiment testing quantum non-locality. Entangled photons from the source are sent to two fast switches, that direct them to polarizing detectors. The switches change settings very rapidly, effectively changing the detector settings for the experiment while the photons are in flight. (Figure by Chad Orzel)

The new experiment solve the detection efficiency problem by clever choice of the entangled system, using electron spins in diamond, which can be read out with very high efficiency. And they close the signalling loophole by putting their two detectors very far apart, and providing each detector with its own independent random number generator.
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Message 1736217 - Posted: 22 Oct 2015, 14:10:20 UTC - in response to Message 1736213.  
Last modified: 22 Oct 2015, 14:35:05 UTC

But this is the Aspect experiment, not the Hanson experiment.
Tullio
So says also the caption. This is the third Aspect experiment.
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Message 1736227 - Posted: 22 Oct 2015, 14:51:52 UTC - in response to Message 1736217.  

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Message 1736228 - Posted: 22 Oct 2015, 14:53:34 UTC - in response to Message 1736227.  

One must be careful with what journalists write. My source is "Nature" but I cannot link it.
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Message 1736233 - Posted: 22 Oct 2015, 15:06:32 UTC - in response to Message 1736228.  

One must be careful with what journalists write. My source is "Nature" but I cannot link it.
Tullio

Indeed.
And Nature wants money to read their articles.
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Message 1739415 - Posted: 3 Nov 2015, 22:25:25 UTC

Spin is time.
http://physics.aps.org/articles/v8/106
Viewpoint: Nuclear Spin Points out Arrow of Time

Entropy production, a quantity associated with the emergence of the arrow of time, has been successfully measured in a microscopic quantum system.

Compared to many weird-sounding concepts in physics, the idea that time has a preferred dirction seems downright obvious. After all, a broken glass won’t reassemble into one piece. But the origin of the arrow of time isn’t at all obvious to physicists. This is because the physical laws that describe microscopic systems are reversible: rewind the clock and two colliding particles will go back from where they came. Where then does irreversibility come from? Is there some undiscovered source of irreversibility at the microscopic scale? Or does it emerge when crossing some microscopic-macroscopic boundary? A new contribution to this already active dialogue [1–3] comes from Roberto Serra at the Federal University of ABC, Brazil, and colleagues [4]. They have, for the first time, experimentally measured the entropy production in a microscopic, quantum system: a nuclear spin (Fig. 1). A positive entropy production is a proxy for the arrow of time, and having measured it, the authors open the door to studying time’s arrow on the quantum scale.

What does it mean to measure time’s arrow? Formally, the existence of an arrow of time is dictated by the second law of thermodynamics, which says the entropy of a closed system can only increase [1]. And although experimentalists cannot rewind the movie of a thermodynamic transformation, they can measure by how much this rewinding is impossible. This is quantified by the entropy production, which is zero if the movie can be rewound and positive if—as is most often the case—it cannot.

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Message 1739441 - Posted: 4 Nov 2015, 0:17:56 UTC

What is a positive entropy production?
You cannot measure entropy, nor entalpy.
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Message 1739464 - Posted: 4 Nov 2015, 1:56:20 UTC - in response to Message 1739441.  

S=klnW (on Boltzmann's tomb in Vienna)
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Message 1739472 - Posted: 4 Nov 2015, 2:59:31 UTC - in response to Message 1739464.  

S=klnW (on Boltzmann's tomb in Vienna)
Tullio

I stand corrected:)
To quote Planck, "the logarithmic connection between entropy and probability was first stated by L. Boltzmann in his kinetic theory of gases".
Probability in science is real but very difficult to comprehend.
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Message 1739516 - Posted: 4 Nov 2015, 7:45:41 UTC - in response to Message 1739472.  
Last modified: 4 Nov 2015, 8:34:21 UTC

You are not the only one. From Ernst Mach to Albert Einstein many scientists did not understand probability and this is probably what brought Boltzmann to suicide.
Tullio
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