Official "Science News" Thread

[LaurV]

Actually, what some guys want to do now, they want to create carbon fiber structures that are filled with helium first, to balance the pressure, then the helium is released slowly as the structure goes up, ending up closer to the top of the atmosphere, and vacuumed inside. These structures are intended to be kind of "permanent" things, you can not replace (so easy) the lost helium. So, once there, they will stay there (the pumps can work solar and maintain the vacuum level) and "never" return down. Another problem would be to shield them against the sun and UV, and of course the Earth's whatever belts they can find there up.

Re: 150 atm inside (crosspost), you can make a sphere of (whatever) and fill it with a high pressure fluid (gas), and it will resist, because the material would need to be teared apart for the fluid to go out. The "tearing apart" force is very high. How about you try to put 150 atm outside, and 1 atm/nothing inside? The material in this case will only need to be "bent", where the force is much lower. See the divers who take empty iron or tin canisters when they dive, and the canisters are squashed by the underwater pressure starting from the first meters. The same canisters will get a rounded form if you put some pressure inside, but they will not break.

[xilman]

Originally Posted by LaurV

Actually, what some guys want to do now, they want to create carbon fiber structures that are filled with helium first, to balance the pressure, then the helium is released slowly as the structure goes up, ending up closer to the top of the atmosphere, and vacuumed inside. These structures are intended to be kind of "permanent" things, you can not replace (so easy) the lost helium.

Why do you need to lose much helium?

Pump it into pressurized containers and drop them (including the pumps) as ballast. Pick up the containers when they reach the surface and re-use. About all that wouldn't be recyclable would be the parachute subsystem.

[LaurV]

Well, pumps you can't drop, you will need them to compensate the lose of vacuum. If you say that you don't need strong pumps for that, then well, you don't need strong pumps for anything, as you raise, the pressure is lower and the helium from the balloon would go out by itself What do you have against me going up there and staying there ? I won't come down to bother you... only maybe pee on you from there above, when you upset me, :p.

[xilman]

Originally Posted by LaurV

Well, pumps you can't drop, you will need them to compensate the lose of vacuum. If you say that you don't need strong pumps for that, then well, you don't need strong pumps for anything, as you raise, the pressure is lower and the helium from the balloon would go out by itself What do you have against me going up there and staying there ? I won't come down to bother you... only maybe pee on you from there above, when you upset me, :p.

By hypothesis, He is a valuable resource. If it is valuable enough it is worth carting up pumps, containers and parachutes so that the He can be re-used, irrespective of whether other pumps are required for other purposes. Re-using where possible kit needed to get the He back to the ground seems to me to make sense.

[only_human]

Exclusive: Secretive fusion company claims reactor breakthrough
Now holds plasma for 5 milliseconds

The upgraded C-2U was back in operation by March. At a symposium today in memory of Rostoker, who died in December, Tri Alpha’s chief technology officer Michl Binderbauer announced that by June the new machine was producing FRCs lasting 5 milliseconds with no sign of decay; they remained the same size throughout.

Binderbauer says that next year they will tear up C-2U again and build an almost entirely new machine, bigger and with even more powerful beams, dubbed C-2W. The aim is to achieve longer FRCs and, more crucially, higher temperature. A 10-fold increase in temperature would bring them into the realm of sparking reactions in conventional fusion fuel, a mixture of the hydrogen isotopes deuterium and tritium, known as D-T. But that is not their goal; instead, they’re working toward the much higher bar of hydrogen-boron fusion, which will require ion temperatures above 3 billion degrees Celsius.

Researchers have several reasons for wanting to go that extra mile. First, tritium doesn’t occur naturally on Earth, so it has to be made by bombarding lithium with neutrons. Physicists plan to do this in the fusion reactors that will one day consume the tritium, but no one has shown that such a process is practical. Because D-T reactions also produce large quantities of high-energy neutrons, the reactors need thick shielding. But the neutrons still degrade the structure of the reactor and make it radioactive. Researchers don’t yet know if it will be possible to find radiation-hard materials capable of surviving the onslaught. Many think these make D-T fusion impractical for a commercial reactor. “I wouldn’t have spent 10 years on [Tri Alpha’s advisory] committee if it was working on a D-T system,” Richter says.

Hydrogen-boron, at first, doesn’t look much more promising. “It takes 30 times as much energy to cook, and you get half as much energy out per particle,” Binderbauer says. But boron is abundant, and the reaction produces no neutrons, just three alpha particles (helium nuclei)—hence the company’s name. Hydrogen-boron fuel “makes conversion to electricity much easier and simpler,” Richter says.

[LaurV]

Originally Posted by xilman

By hypothesis, He is a valuable resource. If it is valuable enough it is worth carting up pumps, containers and parachutes so that the He can be re-used, irrespective of whether other pumps are required for other purposes. Re-using where possible kit needed to get the He back to the ground seems to me to make sense.

Didn't see this reply, I have talked with few friends, all of them good engineers in different domains (none of them specialist in this problem, however, but we work here with pressure for different industrial machines, like pick-and-place, etc, in fact the production lines are heavily dependent of pressurized air, liquid nitrogen, etc) and they all seem to agree with you that the helium should not be wasted They said that "it would be stupid to release the helium into the atmosphere and lose it in space", and that "all the equipment to compress it in polyethylene bags till they are heavier than the atmosphere would not be heavier than 100 kilos or so. Well...

[only_human]

Why the world is running out of helium

But in 1996, the US passed the Helium Privatisation Act which directed that this reserve should be sold by 2015 at a price that would substantially pay off the federal government's original investment in building up the reserve.

The law stipulated the amount of helium sold off each year should follow a straight line with the same amount being sold each year, irrespective of the global demand for it. This, according to Professor Richardson, who won his Nobel prize for his work on helium-3, was a mistake. "As a result of that Act, helium is far too cheap and is not treated as a precious resource," he said. "It's being squandered."

Professor Richardson co-chaired an inquiry into the impending helium shortage convened by the influential US National Research Council, an arm of the US National Academy of Sciences. This report, which has just been published, recommends that the US Government should revisit and reconsider its policy of selling off the US national helium reserve.

"They couldn't sell it fast enough and the world price for helium gas is ridiculously cheap," Professor Richardson told a summer meeting of Nobel laureates from around the world at Lindau in Germany. "You might at first think it will be peculiarly an American topic because the sources of helium are primarily in the US but I assure you it matters of the rest of the world also," he said.

Professor Richardson believes the price for helium should rise by between 20- and 50-fold to make recycling more worthwhile. Nasa, for instance, makes no attempt to recycle the helium used to clean is rocket fuel tanks, one of the single biggest uses of the gas.

Professor Richardson also believes that party balloons filled with helium are too cheap, and they should really cost about $100 (£75) to reflect the precious nature of the gas they contain.

[ewmayer]

After a week of intense debate, Stephen Hawking and his colleagues are still puzzled by black holes | WaPo

Re. the black hole confab: Speaking of much-neglected 'dusty old' theories, I find the pervasive lack of mention (or perhaps better, misrepresentation) of the second law of thermodynamics in the context of the alleged information paradox exceedingly curious. After all the 2LOT tells us - in stark contrast to the assertions made in the piece like 'Information isn't supposed to disappear' - that information is in fact destroyed (in the sense of being rendered irretrievably nonrecoverable) all the time. The term is 'irreversibility', and in many ways it defines the blurry transition zone from the microscopic world, in which 'all individual transactions are time-reversible' to the macroscopic, in which the resulting collective behavior is not. Boltzmann, anyone?

Equally curious is that Hawking himself in his groundbreaking earlier work in which he achieved the first plausible (albeit piecemeal) unification of quantum field theory with classical (= relativistic but continuum-based) gravitation, came up with a strikingly lovely result regarding blackbody (= diffuse, i.e. entropy-maximized, i.e. all-detailed-information-lost) radiation from black holes and the entropy of same. So the present extreme aversion to the idea of information loss in the process of black hole accretion among the 'thought leaders' in the field -including Hawking himself - strikes me as bizarre. Perhaps it's simply the natural research bias that confirming (in this case by extending to encompass novel phenomena which were unknown when the original theory was being developed) existing theories is inherently 'less sexy' that publishing 'radical paradigm-smashing' new ones.

From another phys.org perspective on the issue:

[The idea of black hole information loss] posed a huge problem for the field of physics because it meant that information inside a black hole could be permanently lost when the black hole disappeared — a violation of quantum mechanics, which states that information must be conserved.

Uh, QM may say this for individual microscopic events, but again, what about large-scale statistics of collective behavior? Even though QM is now accepted as underpinning all macroscopic physics, I've never heard of any luminary claiming that the second law of thermo is thus a dead letter in the macroscopic realm where, last time I checked, information continues to be merrily and profligately destroyed and entropy thus keeps increasing. Why should matter (i.e. mass/energy) falling into a black hole be an exception? Sure, there may be some wacky stuff happening to spacetime near (and inside) the event horizon, but there is no reason to believe that the infalling stuff suddenly stops being subject to the rules of statistical thermodynamics.

Similarly, here: The entropy of black holes:

Yesterday I talked about black hole thermodynamics, specifically how you can write the laws of thermodynamics as laws about black holes. Central to the idea of thermodynamics is the property of entropy, which can be related to the amount of physical information a system has.

For classical black holes, this is a problem, because if you toss an object into such a black hole, the object (and all its physical information) is lost forever. It is as if the information of the object was erased, which would violate the basic principle that information cannot be destroyed. Now you might argue that being trapped is not the same thing as being destroyed, but for information it is. If you cannot recover the information, then it has been destroyed.

So it would seem that black holes "eat" information, even though the laws of thermodynamics say that shouldn't be possible. This is known as the black hole information paradox.

Could someone point out to me which law of thermodynamics says that information cannot be lost? Because for the life of me, I never heard of that one.

Paul, am I overlooking something blatantly obvious in my take here?

[only_human]

Three years ago someone on Physics Stack Exchange asked: Why is information indestructible?

I really can't understand what Leonard Susskind means when he says that information is indestructible.

Is that information that is lost, through the increase of entropy really recoverable?

He himself said that entropy is hidden information. Then, although the information hidden has measurable effects, I think information lost in an irreversible process cannot be retrieved. However Susskind's claim is quite the opposite. How does one understand the loss of information by an entropy increasing process, and its connection to the statement "information is indestructible".

Black hole physics can be used in answers, but, as he proposes a general law of physics, I would prefer an answer not involving black holes.

I didn't bother reading the answers because I don't think it's on the test and these days are too damn hot for deep thinking.

[xilman]

Originally Posted by ewmayer

Could someone point out to me which law of thermodynamics says that information cannot be lost? Because for the life of me, I never heard of that one.

Paul, am I overlooking something blatantly obvious in my take here?

I am very far from being an expert and I've no idea how to resolve the BH information loss issue, but here is my take.

AIUI (meaning imperfectly) information is "lost" in classical thermodynamics when you cease to pay attention to individual particles but instead decide to work with ensemble averages. The particles themselves continue to preserve information in terms of their momenta, etc, and if you were prepared to re-record their properties all the original information will still be there. A particular "random" state taken from the large number of random states which are a close enough approximation to a distribution in thermal equilibrium is unique --- it differs from all other states taken from any distribution and requires exactly the same amount of information to specify it as any other state whether taken from a distribution near or far from equilibrium.

The problem with GR and QM, again AIUI, is that the former doesn't know how to treat what happens at a singularity. On the face of it, nothing can happen at a singularity because by definition almost everything is either infinite or zero in size. GR allows a black hole to posess abitrary values only for its mass, angular momentum and electric charge. Everything else is either uniquely determined by those quantities or can not be determined at all. Information appears to fall into the latter class.

[Xyzzy]

http://www.washingtonpost.com/news/e...s-loss-of-ice/