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Submission + - Quantum Mechanics Forbids the Expansion of Spacetime at Scales Smaller than 60m (

KentuckyFC writes: In the late 1990s, astronomers discovered that not only is the universe expanding but the rate of expansion is increasing. In other words, every galaxy in the cosmos is accelerating away from us. Since then, cosmologists have been intensely interested in studying the effect in more detail. Now one astrophysicist has calculated that quantum mechanics places important limits on how the expansion can be observed. The conclusion comes from a simple thought experiment. Imagine two quantum particles in an accelerating universe like the one we live in. As the universe expands, the separation between these particles increases, an effect that is measurable by their redshift (which is how astronomers measure the movement of distant galaxies). However, quantum mechanics naturally introduces some uncertainty into the position of both particles which can swamp any distance changes caused by cosmic acceleration. And the critical distance at which this uncertainty becomes important is 60 metres. That means there is no measurement, even in principle, that could unambiguously reveal cosmic expansion on scales smaller than 60 metres or so. And there is no sense in which a region of space can be said to expand on these smaller scales. That's interesting because it is the first theory to predict a natural boundary between the quantum and cosmic scales and also predict the scale at which this happens.

Submission + - Ask Slashdot: Best Book Or Game To Introduce Kids To Programming? 1

connorblack writes: My very gifted nephew is about to turn 9 this month and I would love to get him some sort of fun, engaging book or game to introduce him to the basic concepts of programming. I have a feeling if approached correctly he would absolutely devour the subject (he is already working through mathematics at an 8th grade level). What I first was looking at were the Lego Mindstorm programmable robots- which would have been perfect, if only they weren't around 300 dollars... So if there's anything similar (or completely new!) you've either heard praise about or used yourself with your kids, it would be great to get a recommendation. Also if possible I would want to stick to an under 100 dollar budget.

Submission + - Quantum Cryptography Theory Has A Security Defect (

An anonymous reader writes: Researchers at Tamagawa University, Quantum ICT Research Institute, announced today that they had proved the incompleteness and limit of the security theory in quantum key distribution. They showed that the present theory cannot guarantee unconditional security. Until now, the majority of researchers in quantum information science have believed that quantum cryptography (quantum key distribution) can provide unconditional security. The guarantee of its unconditional security is given by the trace distance, which is a quantum version of the evaluation of a mathematical cipher. However, since 2006, new developments in the field have cast criticism over the meaningful security of cryptography ensured only by the trace distance. Despite these criticisms, many papers have continued to claim that the trace distance guarantees unconditional security in quantum key distribution.

Submission + - How Apple and Amazon Security Flaws Led to Mat Honan's Epic Hacking ( 1

An anonymous reader writes: The story behind the hacking of Mat Honan's multiple accounts has been revealed and points to massive failures in how Amazon and Apple handle password recovery. Accounts for both sites can be easily accessed with simple to find publically available information. If you ask me, both companies should be liable for violating privacy laws.

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