Wikipedia:Reference desk/Archives/Science/2012 July 13

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July 13

Gravitational potential energy

Hi, Potential energy#General formula gives a formula for the the gravitational potential energy of a system of two masses. What is the generalised formula for a system containing an arbitrary number of masses? 86.179.115.69 (talk) 02:16, 13 July 2012 (UTC)

The link you provided tells you how to do it; "Given this formula for U, the total potential energy of a system of n bodies is found by summing, for all ${\frac {n(n-1)}{2}}$ pairs of two bodies, the potential energy of the system of those two bodies." 203.27.72.5 (talk) 02:34, 13 July 2012 (UTC)

Oh thanks, I do apologise, I did not read far enough. 02:40, 13 July 2012 (UTC) — Preceding unsigned comment added by 86.179.115.69 (talk)

term meaning

what is the meaning of the term-'dextrocardia' ? — Preceding unsigned comment added by Akshay15628 (talk • contribs) 03:21, 13 July 2012 (UTC)

Dextrocardia might be somewhat relevant. StuRat (talk) 03:34, 13 July 2012 (UTC)

Testing for an Alzheimer's gene

This article says this: "The catch is that a genetic test for the protective mutation is illogical, since it's so rare, experts said. In order to determine if an individual has the gene, doctors wouldn't be able to detect it."

Can someone explain this to me? It seems self-contradictory. Dismas|^(talk) 04:13, 13 July 2012 (UTC)

It seems like they really messed up their writing. I suspect they meant to say something like this:

"The catch is that performing a genetic test for the protective mutation is a poor use of resources, since it's so rare." StuRat (talk) 04:21, 13 July 2012 (UTC)

The article is full of apparent typos that change the meaning of what's written e.g. "Genetic test for the gene would(n't?) make sense on account of its scarcity", "The mutation appears to slow the production of the beta-amyloid protein, which has long (been?) considered a cause of Alzheimer's.". 203.27.72.5 (talk) 04:30, 13 July 2012 (UTC)

I submitted a post telling them how bad this article is. I suggest anyone who agrees do the same, so they will clean up their act. StuRat (talk) 05:00, 13 July 2012 (UTC)

Great idea for scientists to email religious websites to ask them to clean up their act. Could take a while though. Meanwhile I would tend to avoid religious websites if I wanted reliable medical information.--Shantavira|^{feed me} 08:33, 13 July 2012 (UTC)

I've found that even web pages with a systemic bias (religious sites, politcal sites, sites trying to sell you something) tend not to be biased when talking about subjects not relevant to their bias. In this case, the existence of a particular testing method for a disease says nothing about the existence or non-existence of God, so they have no reason to intentionally use bad logic, let alone bad English. On the contrary, if they can provide excellent, unbiased articles on subject not related to their bias, this may give them more credibility on those subjects they care about most. So, I believe they will make an effort to improve their articles, if we point out the problems to them. StuRat (talk) 18:22, 13 July 2012 (UTC)

One situation where this sort of thing might make sense is when the condition is so rare that the false positive rate for the test exceeds the actual positive rate for the condition. I think there's a name for the statistical conundrum that results... Staecker (talk) 11:42, 13 July 2012 (UTC)

It's an example of a base rate fallacy, and more specifically it's the false positive paradox. Equisetum (talk | contributions) 17:14, 13 July 2012 (UTC)

To clarify, it is of course only a base rate fallacy if you fail to factor in the base rate (incidence of the mutation in this case) into the false positive rate of the test, if you do factor it in and conclude that the test isn't worth doing because of it that's the false positive paradox. The sentence of the article seems to me that it may have been written by someone who has had these concepts explained to them, but hasn't understood them. Equisetum (talk | contributions) 17:31, 13 July 2012 (UTC)

I think the main reason a test wouldn't make sense would be that the test could only predict the absence of Alzheimer's disease, so a positive result would not call for any different action than a negative result. The only value of a test would be to give some reassurance to 1% of the population. Looie496 (talk) 18:53, 13 July 2012 (UTC)

Thanks all! Dismas|^(talk) 07:24, 14 July 2012 (UTC)

Does gravity remove space?

Let's say there is a small universe that is finite but unbounded (a closed universe), and this universe is filled perfectly evenly with particles. Will gravity pull the particles together, effectively removing space and making the universe smaller, or will gravity tug equally in all directions, keeping the particles where they are and maintaining the universe's size? Goodbye Galaxy (talk) 15:13, 13 July 2012 (UTC)

I would say that it displaces space which is what a gravitational field is: the displacement of space by the massive object. The gravity is the force of the space "trying" to get back to its rightful place in the lattice. They will coalesce in the center unless there is something to keep the outer particles in equillibrium with the central ones, right?165.212.189.187 (talk) 15:19, 13 July 2012 (UTC)

Your question does not provide enough information. What are the initial conditions? Is that universe expanding? What's the density of matter? Dauto (talk) 15:29, 13 July 2012 (UTC)

Right. Let's say no dark energy, no cosmological constant. It begins completely static. Density is very light (no need to take other forces other than gravity into account). Goodbye Galaxy (talk) 15:35, 13 July 2012 (UTC)

Yes, space will get smaller. This is the big crunch scenario. -- BenRG (talk) 15:43, 13 July 2012 (UTC)

OK, in this scenario, what if you took a spaceship and travelled "out" away from the center before the gravity was strong enough to prevent it. Would the spaceship avoid the big crunch?165.212.189.187 (talk) 19:19, 13 July 2012 (UTC)

I wouldn't think so. I'm no physicist here, but I would think several things. 1) In such a universe, a spaceship couldn't exist. 2) If such a spaceship did exist for the sake of the question, I would thing that once the ship reached the terminal boundary, it's engines would no longer be operating within the laws of physics. In fact, once crossing the terminal boundary, it is possible the ship would disintegrate because the forces that construct matter would no longer apply. Just a guess. I would think that you are assisted to the edge by the gravitational pull of the outer matter in equal balance to the pull from the inner matter. As you approach the edge, the draw will become increasingly stronger as you put more cosmic matter behind you that at some point the draw toward the center will overcome any sort of thrust you could generate. So for example, if Earth is the center and the moon is the outer edge, there is a point between them where they will null each other out. As you approach the moon, it will assist you to fight the Earth's pull. But at some point once you pass the moon, it's gravity and Earth's gravity will work against you.--v/r - TP 19:59, 13 July 2012 (UTC)

So you are saying that black holes arent the only cosmic body that can have an escape velocity greater than the speed of light?? Like if you find yourself on the "wrong" side of a giant supercluster.165.212.189.187 (talk) 20:23, 13 July 2012 (UTC)

If you consider that the universe consists of black holes, wouldn't that make sense? Again, I am not at all even educated in this area, I'm just putting a little layman's logic toward the problem. Although, let's consider the possibility that you can escape gravity. Do the forces (gravity, electromagnetic, weak, and strong) exist outside of the universe? My guess is that if particles such as the Higgs Boson cannot escape gravity, then the forces that give matter mass and ultimately the force that holds matter together would not exist beyond the terminal barrier. So you'd essentially disintegrate. If you were to escape that terminal barrier, you'd fall apart atomically and the resultant matter would fall back inside of the terminal barrier. Infact, I'd make a guess that you'd get less than a nanometer outside of the terminal barrier before this happened. Or, you could even theorize that the terminal barrier is exactly where this effect would happen. So upon reaching the barrier is where your atoms would break apart and essentially turn back toward the universe.--v/r - TP 20:41, 13 July 2012 (UTC)

None of it works, 165. If you are assuming the Universe is finite, then it has no center to move away from. The "boundaries" of the universe that have been mentioned here are not things that can be physically crossed by people. To give an awful analogy, it would be like trying to escape the earth by moving far enough along its surface. Someguy1221 (talk) 20:53, 13 July 2012 (UTC)

The OP started by stating that the question was about a unbounded universe (That is one without a boundary) and then he asked if it is possible to scape such universe (That is to reach its boundary). Do you see the contradiction now? Dauto (talk) 21:12, 13 July 2012 (UTC)

I understood it as that space is unbounded but cosmic matter is. The OP is postulating a hypothetical universe here and asking what would exist beyond the expansion of the universe.--v/r - TP 21:15, 13 July 2012 (UTC)

165.* and TParis, I assume the original question was about a universe that's spatially a 3-sphere or some other shape with a finite area but no boundary, so there's nowhere to escape to. The traditional "closed universe" in cosmology is in that category. If instead you have a finite region of stationary noninteracting matter surrounded by an infinite vacuum, the matter will collapse to a black hole, but the surrounding vacuum won't go away, and you can escape to it if you start early enough. -- BenRG (talk) 21:24, 13 July 2012 (UTC)

thanks Ben that is what I meant68.83.98.40 (talk) 22:05, 14 July 2012 (UTC)

Btw. The head question does not match the example it's like two different qs.??68.83.98.40 (talk) 00:42, 15 July 2012 (UTC)

MTT assay in vivo

Important and Urgent

Hi everyone I need to urgently know if MTT assay can be applied to tumor (in vivo) samples. If yes, how? what's the procedure and are there any protocols for it?

Then I need to know what options and methods I have to study angiogenesis in my tumor sections (in vivo).

how about cell viability? how should I check that in in vivo samples?

I would greatly appreciate if you can help me with that ASAP.

Regards everyone Siq3939 (talk) 16:00, 13 July 2012 (UTC)

If this is genuinely important, you should not be relying on random people on the internet for it. If, on the other hand it is homework, you need to show that you have attempted to do it for yourself before anybody here will help you, other than pointing you to articles such as angiogenesis and MTT assay. --ColinFine (talk) 17:04, 13 July 2012 (UTC)

And if it is genuinely urgent, you should not post a request somewhere where nobody has an obligation to respond immediately. It may be important, but if it's on this page, it isn't urgent. ~Amatulić (talk) 17:55, 13 July 2012 (UTC)

It is unlikely that a color coded reagent can be used in vivo, but if you have surgical access to the tissue, why not biopsy and use the extracted tissue in vitro? 71.212.249.178 (talk) 05:20, 15 July 2012 (UTC)

mole as a fundamental SI unit

The seven SI base units and the interdependency of their definitions

Why is mole considered one of 7 fundamental SI units?Its just a number and no physical significance. — Preceding unsigned comment added by 49.244.157.192 (talk) 17:01, 13 July 2012 (UTC)

You're not the first to ask this. See Mole (unit)#The Mole as a unit. --ColinFine (talk) 17:07, 13 July 2012 (UTC)

While that section says that it is different from "fundamental units" like the meter and the second, that is actualy also up for debate. A case can be made that physics is fundamentally dimensionless and therefore there are no units at all that have any physical significance whatsoever. Count Iblis (talk) 17:53, 13 July 2012 (UTC)

I agree that the mole is not a particularly fundamental unit. And the candela isn't fundamental either. But as Count Iblis said above, A strong case can be made that none of the base units are fundamental. Dauto (talk) 18:43, 13 July 2012 (UTC)

Isn't it a derived unit? I thought it was defined as the number of ¹²C atoms in 12g of pure ¹²C, and as such requires gram to be defined so it can be derived. 203.27.72.5 (talk) 21:24, 13 July 2012 (UTC)

Actually, I think the mistake here is that the SI system includes any such notion as a "fundamental unit". The SI Units are divided into base units and derived units. The mole is considered a base unit. Looking at the definitions of the base units, most of them have other units in their definitions; meters has seconds, second has kelvins, ampere has kilograms, seconds and meters, kelvin has moles, moles has kilograms, and candela has seconds, meters and kilograms. The only one that doesn't need antoher unit in its definition is kilogram, which is defined by a prototype. I'm a bit confused myself now as to why they have to have two groupings, since the kilogram is the only truly base unit. 203.27.72.5 (talk) 21:39, 13 July 2012 (UTC)

I fail to see how seconds have Kelvins in its definition and how Kelvins have moles in its definition. Dauto (talk) 02:55, 14 July 2012 (UTC)

The definition of kelvins refers to "water". It then goes on to define what water is using an isotopic ratio stated in a molar fraction. Similarly, the definition of seconds refers to a caesium atom at 0K (ok, so you could just as easily say "at absolute zero", but apparently they choose not to and take the more confusing route). 203.27.72.5 (talk) 03:13, 14 July 2012 (UTC)

As you pointed out, zero Kelvin is independent of the definition of the Kelvin. Note as well that a mole fraction is independent of the definition of the mole because the unit cancels out from the definition (the same unit shows in both denominator and numerator of the fraction). Dauto (talk) 17:18, 15 July 2012 (UTC)

(ec)By that logic, a meter is a derived unit, as it's the distance traveled by light in 1/299,792,458 of a second, and as such requires the second to be defined. My understanding is that being a derived unit is not so much that the definition depends on other units, but the definition (and dimensionality) is wholly specified by other units. For example, a Watt is entirely equivalent in unit and dimensionality to kg⋅m2⋅s⁻³. However that fails for the mole and the meter, as although other units are involved in their definition, there's a physical reference involved (either carbon or light) which transforms both the size and the kind of the measurement being referenced. -- 205.175.124.30 (talk) 21:51, 13 July 2012 (UTC)

That makes sense, but I still don't see how ampere is then a base unit as I can't see how any physical reference is in that definition. Or is there a reference to the physical nature of current that I'm not seeing? 203.27.72.5 (talk) 22:19, 13 July 2012 (UTC)

For "the constant current that will produce an attractive force of 2 × 10^–7 newton per metre of length between two straight, parallel conductors of infinite length and negligible circular cross section placed one metre apart in a vacuum", the physical reference is the two conductors and the electromotive force between them. Granted, it's not all that realizable of a physical reference, but it's still something more than a pure mathematical manipulation of quantities, as you get with watts or newtons. Anyway, the emphasis is not so much on "physical reference", but rather on the transformation of kind. An ampere measures current, which is substantially different type of quantity than "newton per metre per metre" or any such rearrangement of the units in the definition. In contrast, a newton is a kg⋅m/s² - both in size and in quality. Force is intrinsically nothing more than a mass through an acceleration. - Note this is highly dependent on point of view of "kind". As mentioned above, one could argue that the theory of relativity means that space and time are really the same thing with the speed of light being a conversion factor. With that sort of outlook, the definition of the meter seems superfluous, and the meter is simply a non-decimal rescaling of the (light-)second. However, for most purposes we still draw a distinction between space and time (e.g. make a distinction between seconds and light-seconds), so view a space-unit to be distinct from a time-unit. -- 205.175.124.30 (talk) 23:57, 13 July 2012 (UTC)

Yes, physics can in fact be interpreted as not requiring units at all. But even if we decide not to do that, and keep the meter, Kelvin, etc... as the metric system does, there is still the fact, as the OP clearly stated, that a mol is just a number, not a physical quantity at all. Dauto (talk) 02:49, 14 July 2012 (UTC)

A mol is not just a number. Avagadro's number is just a number. A mol is an amount of particles. Just like a kilogram is an amount of mass, a meter is an amount of distance and a second is an amount of time. 203.27.72.5 (talk) 02:56, 14 July 2012 (UTC)

But an amount of particles is just a number as in "one particle", "two particles", "three particles", "one Avogadro's number of particles" (AKA one mole of particles). So yes, a mole of something is just another name for an Avogadro's number of something - not a physical unit. Dauto (talk) 17:22, 15 July 2012 (UTC)

Equivalently, a mole is the conversion-ratio between the molecular property under consideration (like mass, or electric charge), and the quantity of molecules in the sample. If we decided to standardize a unit of mass other than the gram, we would need to standardize a different Avogadro constant to count the number of particles in a sample of unit-mass. And if we decided on a unit of charge other than the coulomb, we would similarly need a different value for the conversion factor between the fundamental charge and the unit-charge. If you study the mole in the context of electrostatics, you'll see it pop up a lot in the mass to charge ratio experiments, where it's again used as a unit-conversion-factor between "bulk" charge and elementary charge; in fact, historically, electric charge measurement was the first context in which an accurate value for N_A was measured. If I recall, it was Michael Faraday who made this connection; and if you read his works, you'll find that he's notorious for using an abundance of strange units. I haven't the slightest idea how he metered out a "grain of water", let alone how he "acidulated" it. His other unit of choice was the Leyden jar. Five-eighths of an inch of zinc converts to about... 800,000 Leyden jars. I bring this up not only because it's humorous, ... but because a genius experimentalist like Faraday was able to extract fundamental physical properties, even when his experimental setup was quantified with totally arbitrarily-selected units. Nimur (talk) 17:50, 14 July 2012 (UTC)

A grain of water is pretty easy. See grain (unit). Grains are still used pretty extensively with small arms ammunition. 203.27.72.5 (talk) 20:44, 14 July 2012 (UTC)

The usefulness of knowledge of Higgs Boson etc.

Physicists have spent countless billions on colliders and other projects to confirm the existence of this boson and other particles and fields comprising the Standard Model. Earlier nuclear research up through the 1940's produced nuclear weapons, atomic power, and nuclear medicine. Has anything useful in everyday life come from this more recent research, as opposed to the earlier findings that atoms can yield energy by fission or fusion? A large body of findings in physics might well be expected to yield improved ways to generate, transmit, convert or store energy, improve transportation or communication, diagnose or treat disease, grow or preserve food, provide fresh water, make rayguns or spaceship drives or other sci-fi staples, defend against various menaces, transmit or store information, do faster computations, or do astronomy. So far, has it amounted to anything more than an interesting challenge and a lucrative career for a great many physicists? By comparison, look how quickly electricity and electromagnetism became useful in everyday life after 1800 when the Voltaic pile was announced, or how quickly we got x-rays and radio following on the work of Bequerel and Hertz in the late 19th century. Have futurists or scientists outlined even in the most general ways how any of this new science might lead to anything useful? How can a "Theory of Everything" be "Useful for Nothing" except prying more research funding from the world's taxpayers. Edison (talk) 22:15, 13 July 2012 (UTC)

A more comprehensive understanding of particle physics could send fusion research in new directions. It would take a few decades or longer before the conclusions are fully realized though. This isn't the first time that there's been a question like this on here. 203.27.72.5 (talk) 22:46, 13 July 2012 (UTC)

"By comparison, look how quickly electricity and electromagnetism became useful in everyday life after 1800 when the Voltaic pile was announced..." About 80-120 years? μηδείς (talk) 22:53, 13 July 2012 (UTC)

Electrical telegraphs were in use much earlier. 203.27.72.5 (talk) 23:01, 13 July 2012 (UTC)

Yes, there were useful electrical and electronic devices around before 1920. By 1811 Davy demonstrated the arc light. He and Faraday used electricity to isolate severl newly discovered elements. Water was decomposed in the first year. There were extremely powerful electromagnets, magnetic telegraphs, motors and generators within 40 years, with new and useful devices every decade. Is the "PET scan" and particle beam used in hospitals actually a result of the particle physics research program, as some articles touting the benefits of the LHC imply? Our article does not say it came from modern particle physics research. The positron was demonstrated in the 1930s and the cyclotron used to make the tagging chemical radioactive also dates to the 1930's. Other claims are that we will get all this spinoff from the tools they perfect to make the LHC work, like better magnets and computers. This is like "The Apollo Program gave us Tang," not a convincing argument, since a food lab could also give us Tang, a magnet lab could engineer magnets without a LHC, and IBM or equivalent are always working on faster computers for competitive purposes. "Getting us from 21st to 23rd century science" is one valid reason, but some sizzle would be nice. (Ways in with clearly understood particle physics could lead to a quantum computer the size of a candy bar, more powerful than a university supercomputer of today, costing less than an Ipod, or an electric car battery with a 500 mile range and a 10 minute recharge time, or the ability to beam power to a spacecraft engine.) Edison (talk) 23:31, 13 July 2012 (UTC)

Telegraphs were hardly "everyday" use, and that the arc light was demonstrated was of no use before electrification. Not that I expect higgsbosoning people will happen any time soon. μηδείς (talk) 00:17, 14 July 2012 (UTC)

Just because they weren't used by everyone everyday doesn't mean they didn't effect everyday life, like for example the newspapers getting information much faster and publishing it for you to read. 203.27.72.5 (talk) 00:28, 14 July 2012 (UTC)

Yes, which people on the frontier downloaded and read every morning while brewing their mail-order espresso. See the relevant articles, gotcha, and yeah, whatever. Fully half the US was electrified by...1925. Even the first transatlantic telegraph cable took til 1858. We can continue this debate in five decades. μηδείς (talk) 03:14, 14 July 2012 (UTC)

No Edison, there are no known real world applications yet for the Higgs boson. Particle physics has had a fundamental role for our understanding of the world including Cosmology, Astrophysics, Astronomy and such, but these areas of knowledge don't have many practical applications either. Nor has space exploration. Sad will be the day when we start questioning those areas of knowledge foe their lack of practical applications. Dauto (talk) 03:20, 14 July 2012 (UTC)

I hate to break it to you Dauto, but that day came the very first time a theoretical physicist asked for funding. If you want money to do something, you can't be surprised when someone asks why that thing is worth doing. 203.27.72.5 (talk) 03:34, 14 July 2012 (UTC)

"No applications yet" ignores the actual question,which dealt with identified possible benefits from all this expensive knowledge(aside from "There will be spinoff") with 10,000 bright scientists sucking up a billion dollars a year for the past and future many years. In the 1700's electrical experimenters noted that static electricity could create light, by causing a glow in an evacuated tube containing mercury vapor, and that the discharge of a Leyden jar could make a small wire incandescent before it melted (thus cueing the thoughtful reader to a future ability of electricity to provide fluorescent and incandescent light, respectively). Eighteenth century electrical researchers also noted that an insulated wire could carry information swiftly to a remote location, even though they only had static electricity's ability to attract or repel a pith ball at the remote end of the wire as a demonstration. Someone's curiosity about "Areas of knowledge" does not automatically justify billions of tax dollars, when they might be as justifiably spent on astronomy, space probes to other planets, archeology, genomics, oceanography, entomology, paleontology, , cognitive psychologyand myriad other areas of research with their own hungry scholars seeking funding. Just as Meitner's work led to the atom bombing of Japan, governments possibly envision exotic new weapons to be derived from a better understanding of particle physics ("Screw with us and we'll pop a black hole on you" or whatever) Surely somehow this expensive and hard-won knowledge might be envisioned as having some application in a few decades, by scientisis working in the field, by science writers, or by futurists. The areas of energy production, transmission, and storage as well as information storage and transformation, and computation seem like possibilities, with possible use in medical diagnosis and treatment, besides the whole sci-fi panoply of spaceship propulsion, deathrays. wormholes, etc. If one had asked a thoughtful researcher such as Faraday or Henry in the 1820's what a complete understanding of electromagnetism might produce, they might have forecast radios, motors, telegraphs, generators , and electric propulsion, rather than sputtering pompously and indignantly "HOW DARE YOU inquire as to the practical implications of research which I find interesting!" Edison (talk) 04:10, 14 July 2012 (UTC)

Did you ever play the real time strategy game Rise of Nations? In the game you can build various big structures called Wonders (just like in Age of Empires). The wonders all come with specific advantages. The Kremlin makes spies, the Statue of Liberty has economic advantages and the space program lets you see the entire map (i.e. spy satellites). But the supercollider costs a shit load and both fixes the price of goods at the market to a lowish level makes other research instantaneous. That makes no sense and I think it just reflects the fact that there are no tangible benefits to having one so they just made something up. 203.27.72.5 (talk) 04:35, 14 July 2012 (UTC)

Edison, as far as I can tell you created this thread as an excuse to soapbox, so I don't think you should sputter indignantly about other people getting on the soapbox and saying things you don't like. -- BenRG (talk) 06:03, 14 July 2012 (UTC)

Please assume good faith. It amazes me that no one has responded with any links to discussions of how a thorough knowledge of particle physics could lead to useful devices down the road. All I've seen is vilification and ridicule for daring to ask the question. Edison (talk) 20:28, 14 July 2012 (UTC)

Here's a link that might interest you. It's Peter Higgs saying that he can't think of any practical significance for the discovery of the particle that bears his name. Here are my favourite quotes; "It’s around for a very short time. It’s probably about a millionth of a millionth of a millionth of a millionth of a second. I don’t know how you apply that to anything useful," "It’s hard enough with particles which have longer life times for decay to make them useful. Some of the ones which have life times of only maybe a millionth of a second or so are used in medical applications," "How you could have an application of this thing which is very short lived, I have no idea." And yet at the same press release he apparently still said that the government is not "investing" enough money. 203.27.72.5 (talk) 23:56, 14 July 2012 (UTC)

Here is another link to an article from the University of Warwick's Knowledge Centre that says, "The investment in CERN has paid off tremendously, as developments in superconducting magnets in the LHC have led to medical applications, detector technologies have been applied to, for example, homeland security, and advances in computing and networking have become something that we all rely on in our daily lives." 203.27.72.5 (talk) 00:13, 15 July 2012 (UTC)

The basic fact is true that the high investments in particle physics have not made commensurate direct technological returns in the area of particle physics, either militarily or civilian.

But this spending was never intended to do so. The physicists like to pretend that the governments of the world spent on this money on particle physics because they discovered that knowledge was inherently valuable. (Robert R. Wilson justified Fermilab along these lines.) But this is not why the government funded this science. The US government in particular was interested in creating a "reserve labor force" of highly-trained technical people in this country — the idea was that if you train a million Ph.D.s in physics, then some large fraction of those people will be siphoned off into practical applications (nuclear reactor engineering, nuclear weapons development, rocketry, lasers, microchips, etc.) that actually are of interest. Funding big particle accelerators was a way to keep the big physicists happy and to get them to start training up large numbers of students. And the more scientists and engineers you have, the more likely that your nation is going to be the one who discovers the Next Big Thing. (We tend to see scientific discoveries as the random Einstein or Newton born into our generation, which isn't something you can really plan for, but the truth is that nearly all the normal, non-revolutionary progress in science and technology are done by just very smart people who, for whatever reason, decided not to become lawyers or bankers or doctors. The progress of science is better seen as a product of the size and funding of the scientific community rather than the number or quality of geniuses.)

It was not just about wonder weapons, of course, though those were the spur for the post-WWII and (especially) post-Sputnik boom in American physics. There are plenty of "mundane" physics advances in the Cold War period — transistors, microchips, lasers, etc. — which played an incredible role in the American war machine. (And have had side-effects for the civilian side as well. I recall seeing somewhere a graphic which traced how many of the technologies behind the iPod originated from labs doing government-funded research.) It's also much larger than the field of physics — the same pattern was applied to oceanography, for example, which is one of the great Cold War sciences that most people don't realize got almost all of its funding from defense sources and created a bank of knowledge primarily interested in topics that would be of interest to people who develop nuclear submarines.

This, anyway, is one thread of argument in the history of science (see, e.g. Chandra Mukerji, A Fragile Power: Scientists and the State, Princeton UP, 1990). The notion of the reserve labor force was at times quite explicit in US science planning. Non-coincidentally, the minute the Cold War ended, the US started to drastically reduce its support of fundamental physics, famously with the cancellation of the Superconducting Super Collider. But if you're asking, is there a wonder-weapon-style payoff to funding particle physics? Not really, not since the early Cold War/late-WWII. (Even the H-bomb, which might be a plausible candidate, owes its development less to funding of particle physics than it does computing.) But I think you're incorrect in assuming that was the goal. --Mr.98 (talk) 14:42, 14 July 2012 (UTC)

A very good answer. It keeps thousands of smart folks doing physics research, as opposed to selling insurance, or being parasites living in their parents' basements. Even if the Standard Model is as lacking in practical applications as a thorough history of 17th century snuff boxes or a debate over how many angels could dance on the head of a pin, some of the 10,000 physicists might have a serendipitous moment and come up with the device, theory, or discovery which saves the human race from disaster. Years ago, when I was interviewing for jobs, the word was that IBM wanted to hire every promising computer scientist or engineer

they could and put them to work on some harmless or promising project, because they might come up with something which would yield profits, but at least they wouldn't develop something good for a competitor. Edison (talk) 01:41, 15 July 2012 (UTC)

Also other spin offs that wouldn't(unlikely) to of been discovered without particle physics is proton therapy in the cure for cancer, as why would any think that firing high energy subatomic particles into the body would be better at killing cancer cells, and leaving healthy cells alone, would be better than medicines. If you know what you want to discover, you will only discover what you set out to discover. You will never get a paradigm shift.Dja1979 (talk) 16:09, 14 July 2012 (UTC)

Proton beam therapy sounds like a very useful technology for treating some cancers, proposed by Wilson in 1946, using the cyclotron, invented in the early 1930's. I can't see how it is a product of the billions spent since the early 1950s to find the various particles in the Standard Model. Spinoffs as the benefit sounds like the "NASA gave us Tang" pseudo-justification. Edison (talk) 01:26, 15 July 2012 (UTC)

Since the invention of agriculture, most people are free to do useless things. However, people engaging in these useless activities have to pretend that what they do is useful to get a share of the food they need to survive. Count Iblis (talk) 16:38, 14 July 2012 (UTC)

And sometimes critical scientific discoveries were made by people intending to do nothing of the sort. Transposons were discovered because Barbara McClintock wanted to know why corn sometimes had spotted kernels. RNA interference was independently discovered in plants and animals because researchers wanted to know, in the first case, if they could make prettier flowers; and in the second case why this one particular gene, lin-4, could function wh clamile being so darn tiny. Someguy1221 (talk) 02:22, 15 July 2012 (UTC)

"Keep this generation's Feynmans and Henrys in the lab, and they might happen upon something interesting and useful" is not at all a silly reason to do this basic research, along with moving us toward 23rd century science, Startrek, and all that. But I was hoping for something like "When we learn how gravity is modulated by the Higgs boson, it might be possible to build a shield against gravity." An article last year claimed that confirmation of the Higgs would "literally shake the very foundation of our understanding of the Universe we live in." How can that not have any implications whatsoever for our technology, near or far term? Quantum physics, by comparison, led to the Tunnel diode, a useful device which would not work per classical physics, and quantum physics is claimed to have promise for future powerful quantum computers. Michio Kaku has claimed that this research could shed light on antimatter engines, teleportation, and invisibility. Is this credible? How might it work? Edison (talk) 02:48, 15 July 2012 (UTC)

If in the past scientists had only studied matters where practical "payoffs" were noticeably likely before the study began, I suspect that a lot of useful discoveries would either not yet have been made or would have occurred much later than they did.

Some people and organizations in the world have enormous amounts of discretionary funds. (See for example our list of most expensive paintings which shows the fortunes that have been spent on some famous paintings). If you were one of those incredibly fortunate individuals or organizations with more money than you could spend on projects that seemed likely to have "payoffs", it might well make sense to invest some of that fortune into research which had no apparent payoff on the grounds that, given your enormous resources, the cost is negligible and, secondly, that although the potential for a "payoff" was miniscule, the possibility that a payoff if one occurred might be enormous. CBHA (talk) 03:08, 15 July 2012 (UTC)

PS I don't mean to suggest that spending huge amounts of money on art is unwise. CBHA (talk) 03:08, 15 July 2012 (UTC)

I will. Someguy1221 (talk) 03:31, 15 July 2012 (UTC)

Fair enough Someguy. For the record, I don't think it is "wise". I just did not want to get into a fruitless discussion of the point, the value of research with no apparent payoffs being a far more interesting topic to me.

To return to Edison's point, I suspect the initial explorations that became "quantum physics" were carried out without consideration of the value of devices such as tunnel diodes. Is that true? I may be hopelessly naive about this. CBHA (talk) 04:22, 16 July 2012 (UTC)

Deflecting photons with electricity or magnetism

Is it possible to change the path of electromagnetic radiation with either an electric firld or a magnetic field? i read that when a white laser passes through air that ionizes the atoms which then keep the white light from disintegrating into its composite rays. --Melab±1 ☎ 22:51, 13 July 2012 (UTC)

That's how the Large_Hadron_Collider works. It uses magnets to control the direction of photons.--v/r - TP 22:59, 13 July 2012 (UTC)

No it doesn't. It controls the path of charged particles though. 203.27.72.5 (talk) 23:02, 13 July 2012 (UTC)

Photons have no charge, so basically no it's not possible. But light does behave very strangely in the presence of a very powerful magnet. 203.27.72.5 (talk) 23:04, 13 July 2012 (UTC)

My bad, I've been reading "proton" as "photon" all over that article by mistake. Big "uh duh" moment for me right now.--v/r - TP 23:07, 13 July 2012 (UTC)

I found a previous question about the same thing and it gave this relevant reference. 203.27.72.5 (talk) 23:17, 13 July 2012 (UTC)

The effect arises due to virtual electrons, it causes non-linear corrections to Maxwell equations, see here. The effective electric permittivity tensor and magnetic permeability tensor and the index of refraction for a region of a constant magnetic field,are given here. Count Iblis (talk) 23:53, 13 July 2012 (UTC)

Does the bending of light produced by refraction have anything to do with electrcity? --Melab±1 ☎ 00:14, 14 July 2012 (UTC)

See Refractive_index#Microscopic_explanation. 203.27.72.5 (talk) 00:59, 14 July 2012 (UTC)

You can always desribe a bending effect by an effective refractive index. Light passing through a magnetic field in vacuum will bend slightly, as I pointed out above (because Maxwell's equations are not exact, there are nonlinear corrections), this can be described as if vacuum with a magnetic field is a medium with a refractive index. The formulas are given in the last link I gave above. Count Iblis (talk) 15:22, 14 July 2012 (UTC)

Why does the linearity of electromagnetism mean light cannot be bent by electric or magnetic fields, if electromagnetism was not linear what else could it be (more specific than non-linear), and if electromagnetism were non-linear how would electric or magnetic fields bend light? --Melab±1 ☎ 04:01, 14 July 2012 (UTC)

One effect of linearity is that you can just add two things and the result will be consistent eg f(a+b)=f(a)+f(b). This means that with the Maxwell's equations that if you have light doing one thing, and light doing something else, then it can also do both at once. So a light beam going left through a strong magnetic field going up, will still be a light beam going left and unaffected. However there are materials that you can introduce that can give non linear effects, eg Pockels effect, Kerr effect, and Magneto-optic Kerr effect. Graeme Bartlett (talk) 04:33, 14 July 2012 (UTC)

I know what linearity is but I do not understand how it relates to electricity or magnetism interacting with light. If light was non-linear what specfic terms exist that fall under the category of non-linearity? Quadratic? Sinusoidal? --Melab±1 ☎ 23:05, 14 July 2012 (UTC)

The early and mid 19th century researcher Michael Faraday, after documenting the conversion of electricity to magnetism and vice versa, sought a "unified field theory" tieing in light with magnetism. He found that a powerful magnetic field caused a rotation of the plane of polarization of light. Edison (talk) 04:52, 14 July 2012 (UTC)

Order of treatment in cancer

According to what order are the elements for treating cancer (amputate/operate, chemotherapy, radiotherapy) applied? I have the impression that it's normally in the order that I cite above, but don't have any source for that. OsmanRF34 (talk) 23:22, 13 July 2012 (UTC)

Completely depends on the individual case and type of cancer in question. Assuming we're only talking about solid tumors, the position of the cancer will strongly determine whether or not an operation has a high likelyhood of success. Radiation also has risks that are specific to different areas of the body. The brain is not readily damaged by radiation but is pretty difficult to operate on. In many cases all three are used to treat one cancer. Non-solid tumor cancers (like leukemia) are obviously totally different again. 203.27.72.5 (talk) 23:31, 13 July 2012 (UTC)

I know somebody who is currently in radiotherapy and is expecting surgery after the radiotherapy is over. They refused chemotherapy, but that would also have been before the surgery. --ColinFine (talk) 23:54, 13 July 2012 (UTC)

Chemo would normally come after the op too, to clear up any cells that the operation might have missed. 203.27.72.5 (talk) 23:59, 13 July 2012 (UTC)

The order in which chemo, radiation, surgery, and adjunct treatment is as much dependent on the limitations imposed by the ethics of medical trials as anything. For instance, the order in most breast cancer is: sugery, then chemo, then radition, and then adjuct hormone treatment for the following 5 years. When my wife got breast cancer in 1997, we read up on it - that was the order of treatment then, but leading researchers suspected that it would be better to do chemo first. The trouble is, surgery was in the early days the only option. Then in the 1920's they introduced radiotherapy. Trials showed that radiotherapy after surgery improved survival rates. Nobody was game to do trials before surgury, as this would put patients at risk. The same happened when chemo was invented in the late 1940's. Today, the norm for breast cancer is still operate-chemo-radiotherapy-hormone therapy. However, with bowel cancer, the operation is very complex and difficult, and up until the invention of TME & J-pouch techniques in teh 1990's very uncertain in outcome. So ethics of testing chemo first was acceptable - sure enough, it turns out that chemo and radiation given concurrently before operating is far batter. So, until recently, the norm for bowel cancer was chemo+radiation, then operate, then follow up chemo. There is no hormone treatment applicable for bowel cancer. With the development of TME operating technique, the chances in earley cancer of cancer cells remaining is very low, so it is normal to omit follow-up chemo. Whether or not operate first is also influenced by whether tumours can ve detected before they become metastatic (spreading to other parts of the body). Wickwack120.145.53.163 (talk) 04:57, 14 July 2012 (UTC)