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Comment Re:Confirming the obvious (Score 1) 27

High energy neutrinos like the ones under discussion should be being produced by the sun unless we are very wrong about how the stellar core acts. In that regard, ruling that out is important, just as ruling out these as being produced by high energy events in our galaxy.

Comment Re:Confirming the obvious (Score 1) 27

Well yes, but keep in mind that we detect a much larger fraction of the neutrinos from the sun. So if the sun was producing a lot more high energy neutrinos than we expect, some of it could show up here. (Although really that would be ruled out by other considerations- IceCube has directional data for where it detects the neutrinos and that would show up very soon, and in fact, for various reasons related to the shape of the detector, it can only detect a small set of solar neutrinos anyways.)

Comment Re:Confirming the obvious (Score 2) 27

Well, it wasn't obvious that they weren't coming from a combination of the sun and the galactic center. The sun might be producing a few much higher energy neutrinos than we expect which would indicate a deep misunderstanding in our models of the core but it was definitely a possibility. The galactic center is very poorly understood, and there's a lot of dust in the way, so some neutrino production method there would have been very plausible.

Comment The current status (Score 5, Informative) 27

As of right now, the only confirmed neutrino sources we have that aren't artificial are the sun and SN 1987A https://en.wikipedia.org/wiki/SN_1987A. SN 1987A was a supernova in 1987 (the first one discovered that year, hence the A). The supernova was in the Large Magellanic Cloud, a very nearby galaxy (which is close enough and small enough that there's been some question whether we should really call it a separate galaxy). The supernova was one of the every few that was close enough that it was visible to earth by the naked eye. While every supernova is believed to create many neutrinos (and in fact this flood is an important part of the process) most supernovas are too far away for us to detect the neutrinos from the supernova because neutrinos are so hard to detect.

As of right now, we don't have any way of making any neutrino detector that is more sophisticated than putting a big bunch of mass in the way and hoping to notice when neutrinos happen to hit it by sheer chance (which is extremely rarely). IceCube is one of a next-generation detector where we have used pre-existing mass, in this case, ice as the South Pole for the bulk of the detector. It turns out that the ice very deep down under high pressure (from the ice above it) is nearly perfectly transparent at the light frequencies need, while the bulk of ice on top blocks out stray light and a lot of stray particles that would swamp the signal.

Detectors like IceCube can be used to actually detect the neutrinos from a supernova before the supernova's light reaches Earth. This isn't due to the erroneous claim from a few years ago that neutrinos travel faster than light, but rather because when a supernova occurs, the light from the core of the star takes multiple hours to get out of the core because of all the mass in the way, while the neutrinos aren't slowed down by this almost at all. This means that the neutrinos effectively get a few hours head start on the light- since they are traveling so close to the speed of light, they get to keep almost all this head start by the time they reach Earth. In the case of SN 1987A the neutrinos did as predicted arrive a few hours before the light. This means we can if we detect a neutrino burst and can get its directional data (which IceCube can approximately do) then we can point our telescopes at a supernova *before the light arrives at Earth* which means we'll get to see the very beginning of the supernova and hopefully get a much better understanding.

Right now, to assist in this there is a Supernova Early Warning System http://snews.bnl.gov/ which is tied in to the various big detectors so it can let astronomers know that a neutrino surge has been detected- this could of course be a supernova, but there's also the even more exciting possibility of an as yet unrecognized event that produces a lot of neutrinos. It will be very important in either case that a lot astronomers get a good early look at it, both professional and amateur, so the system is designed so that anyone can sign up for alerts from it. So if you are an amateur astronomer you should probably sign up- they send out about once test alert a year.

Comment Based in parts on "Mars Direct" (Score 4, Informative) 59

The basic plan in the book is a variant of Mars Direct https://en.wikipedia.org/wiki/Mars_Direct, which was a proposal for a much cheaper way of getting to Mars than previous proposals. The primary cost savings are in making some resources on site (especially fuel for the return). If you haven't read The Martian you should. The book was excellent. Also, relevant XKCD https://xkcd.com/1536/.

Comment Re:ansible (Score 1) 43

No. I'm attempting to explain that people have thought about this a lot, and we understand why it won't work. I also gave you references on what to read that will explain it in detail. I strongly recommend Scott's book I mentioned earlier. If you do think that your idea has any chance of working, the best thing to do is to try and actually go read a bit on the subject and see if you can make it work. But in general, it is worth keeping in mind that the vast majority of ideas *don't work* and understanding why they won't work is important. I'm curious, would you have a similar reaction if I were having a discussion with someone who had an idea about using a dynamo powered by a generator to generate an infinite amount of electric power?

Comment Re:ansible (Score 1) 43

No. You get one such flip. It won't actually matter if you flip them at the same time or not. As long as you keep your coin carefully in a little box (where keeping it carefully in a little box is essentially a metaphor for keeping it in a little box that doesn't let any stray photons in), you can do your flip whenever you want. But let's say we had a billions coins so we could each get a billion flips. We still can't use that to send information faster than the speed of light because we have no way to control how the coins flip. All we'll know is that for my nth coin, it flipped the same way as your nth coin, and that that was true for every n. But if I tried to manipulate how my coin will flip then the entanglement goes away.

Comment Re:ansible (Score 3, Informative) 43

No. That's not how entanglement works. A better way of thinking about entanglement is imagining two fair coins that can be any distance apart and the first time you flip them, you are guaranteed that they'll either both be heads or both be tails. This isn't a perfect description, but this is close enough. If one wants to be mathematically rigorous then we'd say that two particles are entangled if we cannot describe their combined state simply as the tensor product of the state of each one https://en.wikipedia.org/wiki/Quantum_entanglement#Quantum_mechanical_framework. If you want to read a good introduction to a lot of these issues, I recommend Scott Aaronson's "Quantum Computing Since Democritus" which is essentially aimed as an introduction to quantum computing for non-experts with a some math background (essentially assumes is ok with basic linear algebra and basic calculus). Scott is an absolutely fantastic writer.

Comment Re:ansible (Score 1) 43

Unfortunately, it doesn't work that way. There's no known way to get faster than light communication using entanglement and if we're correct in our understanding of physics then it is entirely impossible. One can take two particles that are entangled but if one changes the state of one of them, it doesn't alter the other's state, it simply breaks the entanglement.

Comment Big news also in boson sampling (Score 3, Interesting) 43

In related news on quantum computing 6-photon boson sampling has also been performed (incidentally also by researchers at Bristol with some overap between the two groups). See http://www.scottaaronson.com/blog/?p=2435 for details and discussion. Boson sampling is an important idea which involves estimating the probability distribution of non-intersecting photons. Crucially, boson sampling may be substantially easier to construct since they don't require nearly as much in the way of complicated machinery and error correction as full-power quantum computers, but there are also strong reasons to believe that boson sampling cannot be done efficiently on a conventional computer. That paper is http://arxiv.org/abs/1505.01182 (which also has some other very cool results - they've made essentially reconfigurable chips for this rather than having to make new ones for any specific photon sampling procedure). The original paper which proposed boson sampling is http://www.scottaaronson.com/papers/optics.pdf.

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