October 15

Is this [1] as silly as it sounds? This is a discussion of a hypothesis that the failures of the super-conducting-super-collider and the large hadron collider to actually function is due to the laws of physics acting backwards through time to retroactively prevent a Higgs boson from being formed! The couple of papers I've read here seems to suggest that the authors are reasonably well-respected and that they are actually quite serious! But isn't there a gigantic loophole in their argument for a test of their theory? They say that if the LHC management were to promise to shut down the machine on a one in a million random chance - then if that unlikely event actually happens, then it's extremely strong evidence that there are influences travelling back in time to shut down the LHC!! But surely the odds are good that if the one-in-a-million chance comes up, then there is a high probability that the governments who paid all of those billions of dollars to build the machine would simply fire the LHC management who make this stoopid agreement - and have their replacements turn on the machine despite the result of the random trial? Hence a negative result of the experiment is proof of nothing - and we have an unfalsifiable proposition. Am I missing something? SteveBaker (talk) 03:31, 15 October 2009 (UTC)[reply]

I'm sure this isn't really an answer to your question, but I don't see how what they are proposing implies anything traveling 'backwards through time'. Instead, if what the collider produced would be destructive to the universe, then the anthropic principle / many worlds interpretation would imply we are only here to witness it because the collider malfunctioned. 149.169.106.83 (talk) 03:55, 15 October 2009 (UTC)[reply]

Reading the article, that seems to be exactly what their argument is, even though the science reporter phrases it as time travel. Basically that if the LHC leads to a paradox, then that can't be part of a consistent timeline that we're experiencing. It seems pretty doubtful to me that the laws of physics could lead to a paradoxical outcome, although I guess I can't think of any reason why not. Quantum mechanics seems like it could grant enough leeway for the universe to be steered away from certain outcomes and we probably wouldn't be able to notice most of the time. Rckrone (talk) 04:29, 15 October 2009 (UTC)[reply]

From a general relativistic point of view, the universe is not evolving form initial conditions, it exists as a solution to a system of equations that appears to its inhabitants as if it were evolving. Solutions where a Higgs boson create a time paradox cannot exist, because they would be self contradictory. Therefore, only the solutions where, for example, the LHC malfunctions, will be observed. Also, if the one-in-a-million chance did come up, I think we would try harder to find the Higgs boson, so it would, according to their theory, actually be less likely. 76.67.73.166 (talk) 05:02, 15 October 2009 (UTC)[reply]

At the very least, the hypothesis is falsifiable in that if the LHC gets started up successfully, and successfully detects a Higgs boson, then the hypothesis was incorrect. Red Act (talk) 04:25, 15 October 2009 (UTC)[reply]

And if we spend 100 years trying to set up this experiment and something always seems to go wrong, then that's pretty strong evidence to confirm the hypothesis. Rckrone (talk) 04:34, 15 October 2009 (UTC)[reply]

Really? That's like saying that you hypothesize a magic purple elephant exists in a particular jungle. Each expedition you set out to explore for the magic purple elephant fails. The conclusion, by analogy, would be that (a) the magic purple elephant exists; and (b) it is directly responsible for staging the interferences with your expeditions. Both (a) and (b) are ridiculous. Nimur (talk) 05:34, 15 October 2009 (UTC)[reply]

The analogy would be that you hypothesize that no expedition to find a purple elephant will ever even be carried out. Suppose then that every time someone plans an expedition, something unexpected happens that prevents it from even getting off the ground. If enough expeditions fail to happen and you can somehow calculate the probability of all those expeditions failing to happen given the null hypothesis, and that probability is sufficiently low, then you have a good reason to reject the null hypothesis, and conclude that something weird is going on whatever that may be. If the only plausible explanation of that phenomenon were that purple elephants were somehow sabotaging the expeditions, then you might conclude that was the cause, but there would certainly be room for other explanations if others were plausible. Rckrone (talk) 06:01, 15 October 2009 (UTC)[reply]

An infinite series of indents to this thread can be generated by remorselessly applying the spell "Absence of proof is not proof of absence". Nature provides one unavoidable reason that this series, as all non-abstract series, must like life be truncated. Sic transit gloria mundi. Cuddlyable3 (talk) 15:04, 15 October 2009 (UTC)[reply]

I think you are misunderstanding what I'm saying. Maybe I'm not saying it clearly. There are two experiments going on, not to be confused with one another. There's an experiment to find or not find the Higgs boson, and there's the meta-experiment to see if all attempts at carrying out the first are doomed. Hypothesis 1 is that the Higgs boson exists. Hypothesis 2 is that experiment 1 can actually be run without something against all odds melting it first.

• If experiment 1 is conducted and produces the Higgs boson, that's confirms hypothesis 1 and 2.
• If experiment 1 is conducted and doesn't produce the Higgs boson, that's evidence against hypothesis 1, but confirms hypothesis 2.
• If experiment 1 against the odds fails to be conducted, that offers no evidence for or against hypothesis 1 because there was no experiment, but it is evidence against hypothesis 2.

If enough attempts at the experiment produce the second result, without any producing the first result, then we probably have to conclude there's no Higgs boson. If enough attempts at the experiment produce the third result, without any producing the first or second result, then we probably have to conclude that something we didn't expect is dooming these experiments. That seems pretty far fetched, so there would need to be very strong statistical evidence to rule out just bad luck. But as you said, at some point absence of proof that the experiment can be conducted has to suffice as demonstration of absence of the possibility. Rckrone (talk) 18:10, 15 October 2009 (UTC)[reply]

There is a flaw in your logic. If I devise an experiment for detecting a Higgs Boson that involves nothing more than standing on my head and singing "the star spangled banner" (hypothesis 1 says that this will produce a higgs boson) - then if that experiment fails (which, I suspect it will), then it confirms hypothesis 2? Well, yes, it confirms that my stupid experiment can indeed be conducted - but if my experiment is useless in the first place, it doesn't confirm that the universe cannot unexpectedly cause a GOOD experiment to fail. So if the LHC fires up and doesn't produce a Boson - then nothing of any significance really happened and we still don't know whether the universe would have caused it to blow up if it had been sufficiently well designed that it could have produced a Boson. SteveBaker (talk) 20:36, 15 October 2009 (UTC)[reply]

That's not a flaw in the logic, although I think it is an important point. Hypothesis 2 relates to a particular experiment which may or may not be a good experiment for finding the Higgs boson. In fact the Higgs boson really has nothing to do with hypothesis 2 (except in motivating it). It's possible that hypothesis 2 could be confirmed and yet it's still true that the universe is conspiring against us, just in a way we haven't detected. As you say, maybe the universe "lets" the experiment happen because it's crappy, or the universe forces a certain result in a case where it could go either way. That's not something the meta-experiment can test. But if the experiment in question does always fail to happen, then we can say something more definitive. In other words, confirming hypothesis 2 wouldn't prove the universe isn't conspiring, but refuting hypothesis 2 would prove that it is.

If every single time someone stood on their head and began singing the star spangled banner the building collapsed or they had a heart attack and died, that would be quite a result. Rckrone (talk) 21:29, 15 October 2009 (UTC)[reply]

On reading through the few relevant publications at arXiv, I feel like the original authors (who may be respected physicists) are pretending to publish physics in order to make a political statement. I think this is disingenuous; they are protesting political and economic pressure in the wake of recent troubles at the LHC; but rather than address these issues straightforwardly, they are suggesting throwing caution to the wind and flipping a coin to decide the project's fate - they would prefer to see the LHC fail by random chance - preferring that "...LHC is stopped by our proposed game than if it just failed for some technical or political reason."[2]. Nimur (talk) 05:52, 15 October 2009 (UTC)[reply]

Taken as read, that last line is not completely off the wall. If the God Of The Future has to stop the LHC from generating Higgs particles, It would be preferable to do it in a way that doesn't destroy all the equipment or put all the scientists out of work. APL (talk) 13:36, 15 October 2009 (UTC)[reply]

I wish I could remember the name of a short science fiction story I read some time ago that sounds like this. A scientist had discovered a contradiction between two laws of physics, but in fact all physics laws had been generated in response by nature to contradictions been found like for instance between the wave and particle nature of light. He was warned not to do the experiment as other such experiments had bad effects but did so and disappeared in a flash of light. Many details are probably left out or wrong as it has been a while

Dmcq (talk) 12:19, 15 October 2009 (UTC)[reply

]

We need to miniaturize a Higgs Boson generator. My plan is to buy 36 of them. I will let them sit on my work bench for a few weeks. Then, based on the 6-bit binary representation of 6 numbers from 1 to 60 I will turn some of the generators on, and smash the rest with a hammer.

I'm being silly, of course, but the papers in question [3] do seem to be seriously proposing reverse causality. However, scientific humor is often so dry that outsiders don't spot it, so it's difficult to guess whether this is intended seriously or as some sort of satire. APL (talk) 13:36, 15 October 2009 (UTC)[reply]

Oh wait, My plan is too complicated. I'll just buy a lotto ticket and turn a single generator on if I don't win. Through this means I can take the universe hostage and make it do my bidding. APL (talk) 13:38, 15 October 2009 (UTC)[reply]

That's a good idea, I think I'll do it too ;-)

Dmcq (talk) 14:05, 15 October 2009 (UTC)[reply

]

Be wery wery careful. Larry Niven wrote a story called Rotating Cylinders and the Possibility of Global Causality Violation in which a mathematician tried just such a scheme to twist the universe's self-protection to his personal benefit and that of his species. For his trouble, he wound up getting himself and his race fried in a nova. --Trovatore (talk) 22:14, 15 October 2009 (UTC)[reply]

This is why we need to miniaturize our high energy reseach facilities. Sixty years ago, the common knowledge was that "nobody needed computers except the Government, the military, and a few nutcase physicists." Today, every desktop in the developed world (and a surprisingly large number in the un-developed world) is home to a miniature, personal, network-attached computer. We have found ways to make the computer usable and useful to everyday people. Meanwhile, the common knowledge has transitioned to "nobody needs high energy large hadron colliders except the Government, the military, and a few nutcase physicists." Imagine the possibilities when every man, woman, and child has access to a hadron collider! Nimur (talk) 14:10, 15 October 2009 (UTC)[reply]

Well, we don't really need to miniaturize the LHC. If the universe would care to make a few trillion dollars materialize in my bank account - I promise to use half the money to buy the actual LHC (I'm sure they'd sell it if I offered enough!) and then I'll smash it with a hammer. Hmmmm...nope...no money yet...any time now, I'm sure. SteveBaker (talk) 20:36, 15 October 2009 (UTC)[reply]

A hammer might be ineffective at destroying such a large piece of equipment. If the universe conspires to give me super-powers I will use them to destroy the LHC once and for all. APL (talk) 20:47, 15 October 2009 (UTC)[reply]

This whole business reminds me of

quantum suicide. --Sean 14:21, 15 October 2009 (UTC)[reply

]

It also reminds me of the Transactional interpretation of quantum mechanics and the Wheeler–Feynman absorber theory of electrodynamics, which require time travel in the form of electromagnetic radiation moving backwards through time. --Carnildo (talk) 21:53, 15 October 2009 (UTC)[reply]

I read the paper (the first one). It's... pretty stupid. They start with what I think is supposed to be the Feynman path integral, ${\displaystyle \int _{\gamma }e^{i\,S(\gamma )/\hbar }D\gamma }$. Here ${\displaystyle \int _{\gamma }\,D\gamma }$ is an integral (i.e. a sum) over all "paths" (i.e. histories of the system) and S(γ) is the

principle of least action

comes from.

So, these authors say, what if S is complex rather than real? Then after multiplying by i you still have a real part, so the arrows are no longer all of unit length; they may be smaller or larger. Paths where they're smaller don't count for much, and they think paths with Higgs bosons in them might yield very short arrows. The first problem with this is that if S isn't real then you lose unitarity, and quantum mechanics pretty much falls apart completely without unitarity. The total collapse of the quantum formalism isn't necessarily fatal, but you'd think they'd have something to say about it. It's not apparent that they even know there's a problem. Secondly, they seem to think this modification of the path integral leads to retrocausality somehow, and I can't figure out why. Their whole reason for this seems to be the idea that the path integral is holistic since it treats the whole history at once and any unlikely event in any part of the history makes the whole thing not count. Okay, but that's true in standard quantum theory too, and it (provably) doesn't lead to retrocausality there. Consider proton decay. Proton decay is exceedingly uncommon if it happens at all. To put it another way, "the universe likes to avoid histories where proton decay happens". So, we build a machine to look for proton decay and we don't find any. The machine isn't plagued by technical problems, it just doesn't see what it's looking for; histories where it sees proton decay don't happen. That's not retrocausality, it's life as usual.

A lot of other crazy stuff in the paper. For example, they suggest that one of the options in their card game be to turn off the LHC after seeing 10 Higgs particles. That makes no sense. You don't turn on a particle accelerator and watch exotic particles fly out one by one. The LHC's solid-state detectors produce on the order of a petabyte of raw data per second. The overwhelming majority of that is thrown away almost immediately on the basis of simple heuristics, and the remainder, around a gigabyte per second, is stored in CERN's datacenter and subjected to subtle statistical tests over a period of months or years to tease out a signal. Even if you find a Higgs signal you don't know how many Higgs events there were or which ones they were, you only know that there were enough events of a certain type that it's statistically unlikely that none of them involved the Higgs. It's bizarre that two professional physicists would think that you could just count Higgs particles in real time at the LHC.

In short, they're crackpots or it's an elaborate joke, I'm not sure which. -- BenRG (talk) 21:54, 15 October 2009 (UTC)[reply]

Alternatively, it could be their effort to erode the credibility of arXiv, which has become notorious for releasing a variety of un-reviewed literature unto the masses (who seem unable to differentiate between "draft" and "publication" - let alone "peer reviewed"). As I noted above, I feel like the authors are attempting to make a point, but in a very roundabout way. Whether they have a prior history of research prestige is irrelevant - this publication series looks nonsensical. Nimur (talk) 23:43, 15 October 2009 (UTC)[reply]

I created some Higgs bosons in my backyard, but Schrodinger's cat ate them all. Matt Deres (talk) 17:11, 16 October 2009 (UTC)[reply]

It is not as crazy as it looks. They also mention superdeterminism in their paper. If Nature really is deterministic then you cannot rule out conspirationally looking events leading to some outcome. This can look the same as backward causation in some cases. Count Iblis (talk) 21:26, 20 October 2009 (UTC)[reply]

My mom is doing the experiment of extracting DNA from cheek cells (I'm not sure of the exact details, but whatever the usual way for a highschool biology class do it would be), and she only has isopropyl alcohol, not ethanol. Will this give comparable results? 149.169.106.83 (talk) 03:49, 15 October 2009 (UTC)[reply]

I'm terrible at Orgo; but, even if I can't answer your question, I'll state some facts facts from the article we have on it. The relevant subsection on our article Isopropyl alcohol says here that it dissolves a wide range of nonpolar compounds, and says it's safe and relatively non-toxic. If your mother is a teacher, can she just run the experiment one time and check to see if it gives comparable results? I don't know the answer, but I would assume the answer is yes. 윤리윤리윤리 (talk) 06:05, 15 October 2009 (UTC)[reply]

Using isopropanol throughout will result in a lower quality final product (more salt), although it may still be usable. For the purpose of washing a pellet of DNA (but not precipitating the DNA from solution into a pellet), 70% ethanol is the norm, which you can find in most drug stores (and if she's performing this experiment through a school, she may be able to acquire the higher quality ethanol from biochem providers). Someguy1221 (talk) 06:08, 15 October 2009 (UTC)[reply]

couldn't you use Bacardi 151 in a pinch? Gzuckier (talk) 20:22, 18 October 2009 (UTC)[reply]

what is the calibration,uses,advantages,disadvantages and applications of quartz thermometer —Preceding unsigned comment added by Derrickinlove (talk • contribs) 04:47, 15 October 2009 (UTC)[reply]

The resonant frequency of a quartz crystal depends on temperature, thus a quartz crystal oscillator plus a frequency counter can serve as a thermometer. Some advantages of this arrangement are small size, ruggedness, the display can be remote from the sensor, small thermal inertia gives fast response and the calibration is completed when the crystal is cut (cutting angle defines its frequency/temperature coefficient) and ground (for center frequency). An example application is an ingestible thermometer. A disadvantage is the electrical power needed for the oscillator and counter. Cuddlyable3 (talk) 13:42, 15 October 2009 (UTC)[reply]

Doesn't a nonzero cosmological constant violate (or at least spontaneously break) time-translational symmetry? 76.67.73.166 (talk) 05:06, 15 October 2009 (UTC)[reply]

There are at least one or two sci ref desk regulars who are more knowledgeable about GR than I am, so they may (hopefully) come along and provide a more complete and unequivocal answer to this than I am able to. However, I'm fairly certain that the answer to the question is "yes". This of course implies via

cosmic inflation. Red Act (talk) 06:25, 15 October 2009 (UTC)[reply

]

The big bang violates time-translational symmetry, so the cosmological constant is neither here nor there. --Tango (talk) 08:57, 15 October 2009 (UTC)[reply]

A cosmological constant by itself doesn't break time translation or time reversal symmetry. Roughly speaking a cosmological constant behaves like a repulsive acceleration that's proportional to distance, d²x/dt² = (Λ/3)x. This is time translation invariant since there's no explicit dependence on t, and it's time reversal invariant since acceleration doesn't flip sign when you reverse the direction of time. Of course, there are no nontrivial time-independent solutions to that differential equation. The solutions look like combinations of ${\displaystyle e^{\pm t{\sqrt {\Lambda /3}}}}$, and that's why the cosmological constant is said to cause "exponential expansion". But that kind of violation exists even without a cosmological constant, because the matter will gravitate together. In fact to avoid time dependence in a universe with matter you need a nonzero cosmological constant to counter the gravitational attraction, which was the idea behind Einstein's static universe. -- BenRG (talk) 12:42, 15 October 2009 (UTC)[reply]

Can anyone explain the following phrase to me, please?

"This first leg takes about 2 years if the acceleration's magnitude is about 1-gee."

I've read it in the proper acceleration article (Select, show for the Animation: high speed trip up then down), and couldn't understand the meaning of "1-gee".--Email4mobile (talk) 08:19, 15 October 2009 (UTC)[reply]

"1-gee" is another way of writing "1 g", which means 1 times g, where g is the acceleration of gravity at the Earth's surface. See g-force. Red Act (talk) 08:32, 15 October 2009 (UTC)[reply]

Thank you very much, Red Act! I will have to add it in my dictionary :). —Preceding unsigned comment added by Email4mobile (talk • contribs) 08:44, 15 October 2009 (UTC)[reply]

I presume this is in the context of some kind of space travel. If you could devise some kind of rocket that would keep you accelerating at 1 g for two years, you'd be moving pretty fast! 9.8 meters per second of speed increase for every second is 9.8 x 2 x 365 x 24 x 60 x 60 meters per second which would be 620,000,000 meter per second...but that's twice the speed of light - so long before you get to that speed, relativity is gonna get in your way and limit you to some significant fraction of the speed of light. Since relativity is involved, your perception of time and space will be distorted and your two year-long "leg" of this epic journey will take you a very long distance indeed! I'm sure someone with more time than me will be able to calculate just how far - but it's a long way. If you are thinking of hypothetical rocket engine designs, choosing an acceleration of 1 g is convenient because your crew would be able to experience earth-normal gravity for the entire ride. SteveBaker (talk) 20:05, 15 October 2009 (UTC)[reply]

Perhaps the OP is describing a theoretical acceleration of a massless particle to the speed of light followed by deceleration back to stationary. Cuddlyable3 (talk) 22:39, 15 October 2009 (UTC)[reply]

Massless particles can only travel at the speed of light. At any other speed they would have zero energy, which is pretty much the same, as far as we know, as not existing physically at all. (Abstract objects, like the number 2, can exist without having energy, but they don't exist physically.) --Trovatore (talk) 22:49, 15 October 2009 (UTC)[reply]

The whole question is about proper acceleration, not coordinate acceleration. So there's no problem with a rocket or other massive object maintaining a constant proper acceleration for arbitrarily long, without ever reaching the speed of light. Red Act (talk) 23:58, 15 October 2009 (UTC)[reply]

Is there a future probability that scientist might also discover Energy will be also relativistic like mass? I mean if they encounter a similar phenomenon to light someday that will account for the start and end of this universe?--Email4mobile (talk) 09:43, 15 October 2009 (UTC)[reply]

I'm not sure what you mean; it's already known that all energy is relativistic. Two different observers that are moving relative to each other will in general disagree about how much energy a given

blue shift

depending on the velocity of the observer, and the energy of a photon is proportional to its frequency.

As far as predicting what may happen in the future, we don't do that here. See the top of this page. Red Act (talk) 10:17, 15 October 2009 (UTC)[reply]

how the crystal field theory help us to understanding coordinating bonding and how it link with Jahn-Tller theorem ?Supriyochowdhury (talk) 10:32, 15 October 2009 (UTC)[reply]

The question is outside of my areas of expertise, but do the following articles help you?: Jahn–Teller effect, Crystal field theory, Coordination complex Red Act (talk) 11:02, 15 October 2009 (UTC)[reply]

what is energy crisis?and how energy crisis is related to environment —Preceding unsigned comment added by 203.196.249.171 (talk) 11:31, 15 October 2009 (UTC)[reply]

"Energy crisis" usually refers to an anticipated problem where energy demand is greater than supply. This can cause environmental problems because the energy gap may well be filled by using fossil fuels, pumping lots of CO₂ into the atmosphere. --Tango (talk) 11:41, 15 October 2009 (UTC)[reply]

Wouldn't they just increase the price until the supply and demand are equal? — DanielLC 13:47, 15 October 2009 (UTC)[reply]

Yes, but that's not always tenable. If it costs $300 to drive a car to the store, and you have a society based primarily around automobile transportation, it has very real effects. If the cost of food becomes unaffordable, then people starve. Yes, the economy stabilizes out eventually, but that can have horrific consequences, especially since affecting the price of fuel, energy, heat, etc., affects the prices of so many other commodities (increased transportation costs = increases goods costs, etc.). "The economy will correct itself" works to a certain degree, but "correcting itself" can mean "crashing". --Mr.98 (talk) 16:40, 15 October 2009 (UTC)[reply]

That's not enough to avoid a crisis. Suppose the supply of oil plummets, and as a result gasoline goes to $20 / gallon. Many economic activities that exist today would be totally untenable under those conditions, leading to drastic changes in the economy. Dragons flight (talk) 16:42, 15 October 2009 (UTC)[reply]

I think at $20 / gallon we would just adapt without many changes in activities (the price is not that far off in the UK!), but at $200 / gallon there would be drastic changes. Dbfirs 17:55, 15 October 2009 (UTC)[reply]

I don't think petrol in the UK has ever gone over $10/gal (I'm not sure how fuel price variations have corresponded with exchange rate variations, so I can't be sure). At double that, it would make a difference. People would use public transport more, travel less, etc. --Tango (talk) 18:14, 15 October 2009 (UTC)[reply]

Not to mention, USA is bigger than UK. Far more goods and services need to be trucked across country, and they need to be trucked longer distances. The cost of gas effects the cost of a lot of other things, not just your price at the pump. Groceries are a big one. APL (talk) 18:40, 15 October 2009 (UTC)[reply]

Also, the UK has significantly more infrastructure that does not depend on an individual automobile then in the US. Especially outside of major metropolitan areas. Googlemeister (talk) 20:53, 15 October 2009 (UTC)[reply]

And our cars are about a third the size of American cars. --Tango (talk) 21:00, 15 October 2009 (UTC)[reply]

Have a look at Energy crisis for an overview and Category:Energy crises for a list of specific crises. Regarding the environment, it could be argued that energy crises force people to use less energy or develop innovative ways of conserving energy which may benefit the environment in the long run. This search might help. Zain Ebrahim (talk) 11:54, 15 October 2009 (UTC)[reply]

Of course, if the energy crisis was caused by the sun becoming 10% dimmer, that would be very bad for the ecosystem. Googlemeister (talk) 15:34, 19 October 2009 (UTC)[reply]

The fusion of two hydrogen atoms produces a helium atom. But where do the two required neutrons come from? --Leptictidium (mt) 17:49, 15 October 2009 (UTC)[reply]

See the

proton–proton chain reaction. In short, ¹H + ¹H ≠ ⁴He — Lomn 17:52, 15 October 2009 (UTC)[reply

]

And note that saying "two hydrogen atoms" does not necessarily mean ¹H₁... it can mean, for example, ²H₁ or ³H₁. --Mr.98 (talk) 18:16, 15 October 2009 (UTC)[reply]

And the helium produced doesn't need to be ⁴He₂, it can be ³He₂. --Tango (talk) 18:23, 15 October 2009 (UTC)[reply]

Given the "but where do the two neutrons come from", it seems clear that the original question meant standard hydrogen and helium. If deuterium or tritium were involved, then there are your neutrons. If helium-3 was involved, then you don't need two neutrons. On a tangential note, though, why are you guys (and the pp article) specifying the atomic number of hydrogen and helium? Isn't that utterly redundant? — Lomn 19:11, 15 October 2009 (UTC)[reply]

The fusion of two ¹H ₁ atoms does not produce helium (standard or otherwise), though (not directly, anyway). D and T are both "hydrogen"; I think that's worth pointing out for someone confused. (And the proton-proton reaction explains how you get D from regular H). As for the notation—yes, technically it is redundant, but I've found personally that keeping track of protons helps students when thinking about nuclear reactions, especially when we are talking about isotopes. --Mr.98 (talk) 19:35, 15 October 2009 (UTC)[reply]

If you have heard about the kid in Colorado who allegedly went for an unauthorized balloon ride, What volume of helium would be required to lift him off the ground if we assume that he weighs 50 lbs? I suppose we would need to know the pressure and temperature of the helium as well, but do not have a good estimate other then the altitude was something like 6500 ft above sea level and the temperature in the 60s F. Googlemeister (talk) 20:51, 15 October 2009 (UTC)[reply]

Helium has a density of .18 g/L at 1 atm, air a density of 1.2 g/L at 1 atm (and reasonably standard temperatures). The lifting capacity of helium is (roughly modeled) the density of air minus the density of helium, times the volume of helium. At altitude, the density of air drops -- it's ballpark 1 g/L at 6500 feet. Additionally, you have to put enough helium to create more than ambient pressure to inflate the balloon (but the sea level density is probably enough to suffice here). So, you get about .8 g/L of lift in the given conditions. To lift 30 kg (a low estimate of kid plus balloon materials), you'd need nearly 37500 L of helium, or a spherical balloon about 13 feet in diameter. The news photos I see don't show a spherical balloon, but it looks like a reasonably close estimate. Incidentally, the lifting power of helium has been discussed here repeatedly; there should be lots more in the RD archives. — Lomn 21:40, 15 October 2009 (UTC)[reply]

Turns out that the kid was hiding above his garage, and never flew, so I guess that while it may have been possible, it didn't happen. 152.7.20.66 (talk) 22:54, 15 October 2009 (UTC)[reply]

If I'm not mistaken, the balloon had absolutely no room for any children, unless he could breath helium. Vranak (talk) 01:14, 16 October 2009 (UTC)[reply]

Wonder what the density (lifting power) of Trimix is? DMacks (talk) 05:17, 16 October 2009 (UTC)[reply]

See also cluster ballooning.--Shantavira|^{feed me} 07:14, 16 October 2009 (UTC)[reply]

For Trimix you can work out the average molecular weight using the proportions given. The oxygen and nitrogen will dominate the mass since their molecules are so much more massive than helium. Using lighter gasses than Helium will not make much difference in lift either. eg Helium-3 would be more pricey. Graeme Bartlett (talk) 11:52, 16 October 2009 (UTC)[reply]

The New York Times reported that in a Wolf Blitzer interview on CNN, the kid said the reason he did not answer when he heard people calling his name was “You guys said… that, um, we did this for the show.” Mr. Heene denied that this meant it was all a publicity stunt. Local law enforcement has indicated they do not believe it was a hoax. Has there been any indication that the balloon ever had a gondola which could have carried the boy, or that the boy could have been inside the silver mushroom or the little stub below it? How long after the family called a TV station to report the balloon was away did they call 911? Edison (talk) 14:12, 16 October 2009 (UTC)[reply]

In a press conference that evening, Mr. Heene said the balloon was an experimental vehicle which was supposed to rise and descend via helium, but that it was supposed to move laterally via million volt pulses of electricity it would emit. Heene said that an egg timer on board was supposed to regulate the million volt emissions while it was tethered, before it escaped. Where was the electricity supposed to come from? Various accounts have mentioned a video of the actual launch, but I can only find coverage of the flight, pursuit and landing. Are there any images of the intact balloon and gondola prelaunch or of the liftoff? Edison (talk) 14:39, 16 October 2009 (UTC)[reply]

Found the launch video at CNN.com.[4] No sign of any basket or gondola other than the apparently sealed silver nub below the gasbag. Edison (talk) 14:53, 16 October 2009 (UTC)[reply]

I believe that's the wrong link and/or it changed. [5] gives the launch video for me called "'Balloon boy' story unfolds" (it's near the end) Nil Einne (talk) 20:00, 16 October 2009 (UTC)[reply]

given that the dad was a "scientist" who was building the "saucer" as part of his research into extraterrestrials..... Gzuckier (talk) 20:20, 18 October 2009 (UTC)[reply]

According to [6] they did check with someone to see if it was plausible it would lift the boy, and he suggested based on the dimensions given it was. However based on the real dimensions now available it was not possible for it to lift the boy. It's worth remembering that they had little choice but to err on the side of caution. Also accurately estimating the size of the balloon in the air is probably not so easy. In other words, even though it may be easy to say now, they should have realised at the time it couldn't lift the boy it probably wasn't so easy at the time, particularly since they apparently didn't have initial reason to suspect the father/family may have been fibbing on the dimensions which given it was apparently a hoax, he may have been. Also the weight for the kid was 17 kg (I was expecting it to be something like that). No info on the weight of the balloon but 7 kg seems a reasonable estimate to me. So 25 kg not 30 kg. And when you're just estimating (say 15kg for the child, 5kg for the balloon), 20 kg seems reasonable to me to err on the side of caution. Remember no one ever claimed the balloon was a supersturdy thing designed to carry a child. Nil Einne (talk) 19:29, 18 October 2009 (UTC)[reply]

more proof that the media is irresistably mesmerized by shiny objects. Gzuckier (talk) 20:20, 18 October 2009 (UTC)[reply]

Upon visiting certain developing countries, it is immediately noticeable that the bases of many tree trunks have been painted white, or with some form of whitewash. This usually occurs with cultivated trees or those at the edge of a forest area, and in some areas this is a very common practice. Regarding this subject, I have some doubts.

First, what purpose does this practice serve? In what way is this beneficial to the tree or to the ones who planted it? Is it done for biological protection, or merely for aesthetic purposes (despite the fact that I find it a bit of an eye-sore)? If effective in any way, to what degree is it recommendable?

Second, how prevalent is this practice? Upon mere observation, and from the experiences I can immediately recall, I cannot remember having observed this practice in developed countries, namely those with Western civilizations. However, upon visiting developing countries such as Brazil, Colombia, Mexico, and Kazakhstan, I have noticed that this practice is prevalent in varying degrees. Unfortunately, my inquiries into this subject with the natives have turned up fruitless.

Third, has this practice ever been used in developed countries in the past? —Preceding unsigned comment added by 201.21.180.57 (talk) 21:34, 15 October 2009 (UTC)[reply]

Not sure about Brazil etc., but when I've seen tree trunks painted white in temperate climates, it's been to prevent

Sun scald (see section "Painting"). It's a form of sunscreen for trees. -- 128.104.112.179 (talk) 22:11, 15 October 2009 (UTC)[reply

]

Trees along a road side sometimes have painted white stripes to guide traffic, e.g. in France. Cuddlyable3 (talk) 22:32, 15 October 2009 (UTC)[reply]

In some circumstances, might it be a way of marking trees selected for felling? 87.81.230.195 (talk) 23:31, 15 October 2009 (UTC)[reply]

If I remember correctly (I never paid attention to these things while I used to live in Mexico), it is to prevent sun scald, like 128.104.112.179 said.

cool stuff) 23:39, 15 October 2009 (UTC)[reply

]

In the U.S. I have seen foresters use "safety yellow" paint to mark trees to be felled for timber production. Some on the very base of the tree and some higher on the trunk. This way the harvesters know which trees they are to cut. Could the white paint be intended to provide the tree some protection against dog urine, when in parks or next to sidewalks? Edison (talk) 23:47, 15 October 2009 (UTC)[reply]

Second, how prevalent is this practice? China does it. 218.25.32.210 (talk) 00:52, 16 October 2009 (UTC)[reply]

When I used to live in downtown Manhattan as a kid, tree trunks were painted white -- and included those in the backyard parks with no access by car. Explanation for the white paint was that it was some form of protection against infestation of some sort. DRosenbach ^{(Talk | Contribs)} 02:34, 16 October 2009 (UTC)[reply]

In Spain, especially Andalucia, tree trunks in patios and to some extent street tree trunks are whitewashed partly for decoration and partly to discouraged ant and thus aphid infestation. The practice seems to be confined largely to citrus trees. It doesn't prevent infestation. Caesar's Daddy (talk) 06:22, 16 October 2009 (UTC)[reply]

My next door neighbor here in rural California paints her young fruit trees' trunks white. See tree paint. --jpgordon^{::==( o )} 18:48, 16 October 2009 (UTC)[reply]

Used to be quite common in former USSR for apple trees etc. Apart from sunburn protection already outlined above, another benefit is that it somewhat delays development of flower buds, relieving the risk of frostbite in case of spring

NVO (talk) 20:23, 17 October 2009 (UTC)[reply

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