Wikipedia:Reference desk/Archives/Science/2013 February 21

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February 21

Mercury thermometers

Mercury thermometers become more inaccurate over time. Do they record (overly high) tempatures, or overly low tempatures when they are too old?149.152.23.48 (talk) 00:36, 21 February 2013 (UTC)

I added a title. StuRat (talk) 00:43, 21 February 2013 (UTC)

Note that, if they did drift, all they would need is to be recalibrated (have new numbers painted on). StuRat (talk) 00:45, 21 February 2013 (UTC)

Who says they loose accuracy over time? Accuracy is determined by three things: Random error in taking readings - in the conventional mecury thermometer this is merely a factor of how carefully one looks at the scale and compares it to the mercury height; Systematic error, which is determined by the accuracy of calibration (the position of the glass tube with respect to the scale, accuracy of capilliary diameter), and drift.

In metrology generally, drift is made up of thermal drift, inapplicable to thermometers as it is taken up in calibration, drift over time, and noise. There are no significant time and noise drift mechanisms for normal sealed mercury-in-glass thermometers.

Possibly the OP is referring to sensor thermometers that were once used in photographic processing labs, chemistry labs, and industrial control systems. In these, the mercury is electrically earthed via a wire sealed into the glass at the bulb end, and there is a probe wire fed in via a hole in the glass at the top end. The probe wire is adjusted in position so that at the desired temperature, it just touches the mercury column. When it does, it closes an electrical circuit, which controls the tank heater or whatever is required. These thermometers, when new, are extremely accurate compared to alternatives at the time. However, as the probe wire must move freely in the hole, there is not a perfect seal, and over tens of years some mercury vapour can escape to atmosphere, leaving less in the tube. So, over time, the thermometer reads lower and lower compared to the calibrated temperature. These wire probe type mercuray thermometers have been obsolete for 40 years or more, as solid state electronic thermometers (quartz or platinum sensing) were developed with more than adequate accuracy for the purposes that a mercury thermometer would otherwise be used. But you still sometimes see them. I saw one still in use in a photographic lab only a few years ago.

Ratbone 60.230.238.153 (talk) 03:14, 21 February 2013 (UTC)

In general, mercury thermometers do not drift. However, they may become damaged. Sometimes an old thermometer will have discoloration of the mercury or even bits of oxidized mercury along the capillary. This is caused by improper filling, where moisture or air was sealed inside the instrument. On high temperature thermometers, sometimes a portion of the column evaporates and then condenses in the upper portion of the thermometer. If a thermometer is treated roughly or thermally shocked, it can develop a nearly invisible stress crack, allowing mercury to escape. because of these effects, mercury thermometers need to send out for calibration, but the calibration is not because of any natural drift but because a close visual inspection under a magnifier followed by checking the accuracy is the most reliable way of identifying the above problems. --Guy Macon (talk) 08:27, 21 February 2013 (UTC)

We have several Mercury-in-glass thermometers provided by Environment Canada. Every one of these comes with a correction chart made up by EC. The oldest card and thermometer we have is dated 1978 and is still in use. There are two possibilities that could lead to inaccurate readings. First is if the column of mercury was to separate into two columns. Second, mercury freezes at −38.8 °C (−37.8 °F) and leaving them out at temperatures colder than that may cause problems. I wonder if the OP is thinking of mercury barometers rather than thermometers? It's been a long time since we used one but I seem to recall that the inspectors would check them out every time they were on a site visit. Also the mercury could be drained out for shipping which indicates that, unlike the thermometers, they were not sealed units. CambridgeBayWeather (talk) 01:02, 22 February 2013 (UTC)

Signs of life on Titan and Europa?

Do any of life currently exist on Titan. I thought Titan is way too cold to even support life. Its average surface temperature is -185 C/-300 F. I know Titan currently have water and rains. Some scientist thinks life could exist on Europa's ocean possibly sharks or maritime life. i wonder how is that plausible since Europa's surface is too cold -160 C/-260 F. Does this matter if planet fits under habitable zone to be habitable ? Or most important factor for habitable planets is water and atmosphere?--69.226.39.147 (talk) 01:22, 21 February 2013 (UTC)

If NASA had discovered unambiguous signs of life, I'm sure we would know about it. It is possible for life to not exist on the surface, and to only exist deep underground (or underwater). On Earth, we both have bacteria which live deep underground and live off minerals there and whole ecosystems around hydrothermal vents on the ocean floor, which get their energy from places other than sunlight, such as radioactive decay. Tidal forces could provide energy on the moons of the Jovian planets. If the energy sources are quite limited, you might find the plants and animals there have a much slower metabolic rate, and therefore grow and move more slowly. StuRat (talk) 01:38, 21 February 2013 (UTC)

We have an article on life on Titan. The corresponding article for Europa is a subsection only, mostly because there's virtually no hard evidence to go on (we have attempted no landings there). Due to the good chance of Europa having a subsurface liquid water ocean, my understanding is that it's considered to be a stronger case for extraterrestrial life than Titan; we just don't have as much evidence to examine. I note particularly that I find Stu's initial comment a little vague, mostly because of the various ways it can be interpreted. The Cassini-Hyugens mission found data from Titan that could be the result of biological processes, but could also be from other natural processes. Is that a sign of life? Maybe, depending on your definition. Even this tenuous bit should cast doubt on a blanket claim of "if there were, I'm sure we would know". — Lomn 01:50, 21 February 2013 (UTC)

Ok, let me add the word "unambiguous". StuRat (talk) 01:54, 21 February 2013 (UTC)

Even then, there are vagaries regarding just what "signs" of life are, and whether they're actually related to life, or whether "we" is "we the human race" vs "we the ref desk". Mostly I'd suggest sticking to a more straightforward referenceable statement like "Scientists do not currently know of extraterrestrial life on Titan or Europa, though it has not been ruled out" -- particularly for a leading sentence -- but that may just be the pedant in me. — Lomn 02:03, 21 February 2013 (UTC)

Oh come on, we don't need to be so pedantic, especially if it has a chance of confusing the OP. An unambiguous sign of life would be if a probe sampled the ocean on Europa and saw non-terrestrial microbes with its microscope. A even more unambiguous sign would be if a giant squid attacked the probe with its tentacles, and the probe took a picture of it. In any case, for any reasonable definition of "unambiguous", nobody has detected unambiguous signs of past or present life anywhere except Earth. --140.180.243.51 (talk) 03:37, 21 February 2013 (UTC)

For an interesting fictional treatment of life on Europa, see 2010: Odyssey Two. --Jayron32 02:01, 21 February 2013 (UTC)

"I know Titan currently have water and rains."

Titan has lakes and rain, but they're composed of simple hydrocarbons like liquid methane and ethane, not water.

"i wonder how is that plausible since Europa's surface is too cold -160 C/-260 F"

Both Titan (moon) and Europa have global subsurface oceans. Titan is 50% ice, which corresponds to many orders of magnitude more water than exists on Earth. Europa has a more rocky composition, but it still has a layer of liquid water 100 km thick, which corresponds to 2 times the mass of water on Earth. As for why these subsurface oceans can exist, it's mostly due to tidal heating. The moons orbit close enough to their planets that their near side feels significantly more gravitational force than their far side, causing them to be stretched. This stretching releases heat through friction, which melts enough ice to maintain a liquid ocean. As you said, the surface is too cold to support liquid water, but the interior fares better because the outer ice layer serves as insulation to prevent tidal heat from escaping. --140.180.243.51 (talk) 03:37, 21 February 2013 (UTC)

For another Wikipedia article on a plan to put life on Europa see Terraforming of Europa. Graeme Bartlett (talk) 10:22, 22 February 2013 (UTC)

Time running slowly

When the velocity of a body increases, time for that body starts running slowly. Also, when gravitational force increases, time, in this case also, starts running slowly. Here, in both cases time runs slowly. Why don't time run faster when velocity or gravitational force increases? Chi Yang --27.62.106.130 (talk) 01:58, 21 February 2013 (UTC)

See time dilation for an explanation, it isn't a simple as your original assumptions. --Jayron32 02:39, 21 February 2013 (UTC)

It is fundamental property of time. It is described accurately by spacetime which is a mathematical model that combines space and time in single entity. Gravity and velocity bends spacetime which is observed as time dilation. - manya (talk) 03:24, 21 February 2013 (UTC)

The time dilation for a moving object is relative - something not moving at that velocity sees the object's time slowing down, but the object itself (or anything moving the same speed in the same direction) does not see his time slowing down. Bubba73 ^{You talkin' to me?} 03:40, 21 February 2013 (UTC)

Calculating the electric potential between two point charges

When given the coordinates and the charges of two points, how do I calculate the voltage/electric potential present at some other coordinate? — Melab±1 ☎ 03:09, 21 February 2013 (UTC)

This is one of Maxwell's equations, specifically Gauss's law IIRC. --Jayron32 03:23, 21 February 2013 (UTC)

Gauss' law doesn't tell you the potential. See electric potential instead, specifically "electric potential due to a point charge". Potential is an additive scalar, so if you have the potential due to 1 charge, you can just add the potential due to the other. --140.180.243.51 (talk) 03:39, 21 February 2013 (UTC)

Palladium Hydride

So I am trying to figure out at what temperature Palladium Hydride releases Hydrogen? And at what temperature it adsorbs Hydrogen? How much Hydrogen can it release? Ender Wiggin (talk) 03:58, 21 February 2013 (UTC)

Did you read Palladium hydride? This suggests that you can get 7 hydrogen atoms for each 10 palladium atoms at normal pressure. About 6.6 grams of hydrogen per kilogram of palladium. At 300 degrees hydrogen will diffuse through. So I think that it will absorb and release at lower temperatures dependent on hydrogen pressure. It sounds like we need a graph. Graphs are available at https://notendur.hi.is/egillsk/stuff/annad/PdHyd_paper.pdf and http://www.platinummetalsreview.com/pdf/pmr-v4-i4-132-137.pdf These show that at 70° it can absorb hydrogen at 0.1 atmospheres pressure and then give it back at about 1 atmosphere at 145°. Graeme Bartlett (talk) 09:45, 22 February 2013 (UTC)

Pluto to have a watery surface

This is true in 7.5 billion years scientists eventually Pluto and Kuiper belt object will eventually reach habitable surface temperature [1] it shows that icy moons of outer planets can actually become a ball watery beach and it even said in 7.5 billion years as sun's giant Pluto and Charon will become a liquid beach. However most people will think when they hit habitable surface temperatures they will have technical problems is atmosphere driven off into space. (I was forced to learn when Titan and Europa hit habitable surface temperatures they will hit technical problems:Atmosphere driven off into space) Actually [2] artist's conception's image shows when Pluto warms up slightly, it can create a more substantial atmosphere, but the question will be how warm can the atmosphere survive on Pluto. Can Pluto's atmosphere survive when it gets warmer than the conditions Jupiter and Saturn's moon is now? Alot of artist conception shows when Europa gets warmer, I've watched it on Youtube video, Europa's ice can actually melt into ocean beach, but I am not quite sure on how long will the atmosphere survive there? --69.226.39.147 (talk) 05:17, 21 February 2013 (UTC)

Determining asteroid's orbits

I'm looking for a description of how Asteroid's orbits are measured/determined, and trying to get some idea of the accuracy that can be obtained. It seems pretty surprising to me that the approach distance to Earth can be worked out so far in advance, when surely there must be some close encounters with other bodies that can't be predicted, apart from the questional accuracy of the initial sightings. Thanks in advance. 124.191.176.222 (talk) 07:19, 21 February 2013 (UTC)

Orbit determination may help. Duoduoduo (talk) 20:10, 21 February 2013 (UTC)

Thanks, that was a help, but still no mention of how accurate the determinations are.124.191.176.164 (talk) 07:01, 22 February 2013 (UTC)

Close encounters with large bodies are very rare and predictable since we know where the large bodies are. Close encounter's with smaller bodies are still rare enough and have negligible effect in the short run. In short, you have a valid point but the time scale it takes for the unpredictability of the orbit to become a problem is much larger than what you imagined. Dauto (talk) 00:39, 25 February 2013 (UTC)

If Einstein hadn't invented the theory of relativity, would someone else have?

if einstein hadn't invented the theory of relativity, would someone else have? or might we still not know it today (even though we would know about quantum mechanics, for example). for example simply due to lack of interest or attention. (since we were focused on other aspects of physics for example). 178.48.114.143 (talk) 07:48, 21 February 2013 (UTC)

You never know. I could be the one, if not Einstein. ;) ☯ Bonkers The Clown \(^_^)/ Nonsensical Babble ☯ 07:55, 21 February 2013 (UTC)

No, this could never be. Long before peak oil and peak copper, peak intelligence already happened around 1900. Intelligence is steadily declining since. 95.112.148.69 (talk) 12:26, 21 February 2013 (UTC)

To be pedantic Einstien did not invent the theory of relativity. He postulated it. -- Alan Liefting (talk - contribs) 08:16, 21 February 2013 (UTC)

To be pedantic, it's Einstein, not Einstien. -- Jack of Oz ^[Talk] 19:32, 21 February 2013 (UTC)

(edit conflict) As for the question, we could compare it to the classic case of two separate people putting forward the theory of evolution, namely Charles Darwin and Alfred Russell Wallace. Einstein did have an amazing insight but there is nothing to suggest that at some stage (maybe decades later) someone else would came up with the same theory. Scientific discoveries and technological developments that after Einstein postulated his theories would mean that it would be easier for other scientists to arrive at the same conclusions. -- Alan Liefting (talk - contribs) 08:24, 21 February 2013 (UTC)

• I believe that most physicists think that Special relativity would soon have been invented if Einstein hadn't -- other people were very close to it. The story may be different for General relativity -- that was a huge leap beyond anything that anybody else was doing, and even now there are only a small minority of physicists who really understand it. Looie496 (talk) 08:20, 21 February 2013 (UTC)

  All basic ingredient of special relativity had been known from works of Hendrik Lorentz and Henri Poincaré before Einstein. So, Einstein only made the last step. General relativity would have likely been discovered without Einstein as well—David Hilbert obtained Einstein equations almost in the same time and independently of Einstein. Ruslik_Zero 12:17, 21 February 2013 (UTC)

  Don't forget Hermann Minkowski who also provided much of the mathematical underpinning for both relativity theories. Minkowski basically worked out all of the geometries of spacetime prior to Einstein applying it to light (special) and gravity (general) relativity theories. Einstein did not work in a vacuum, and it is possible, even quite likely, that with all of the ingredients someone would have put it all together eventually. Unprovable, but also not out of the realm of possibility. As Isaac Newton once famously noted "If I have seen further it is by standing on the shoulders of giants." Such a sentiment applies just as well to Einstein as anyone in the sciences. --Jayron32 15:06, 21 February 2013 (UTC)

  I'm not aware that Minkowski did any work on curved spaces. Regarding Hilbert, that's true, but it raises an interesting sociological question: he was considered a pure mathematician, and it's unlikely that any physicist would have paid serious attention to his ideas (since none of them could understand the mathematics). Einstein, in contrast, was already the most famous living physicist when he presented General Relativity, due to his incredible 1906 papers. Looie496 (talk) 17:01, 21 February 2013 (UTC)

  See Minkowski space, Minkowski diagram, etc. --Jayron32 18:45, 21 February 2013 (UTC)

1905. -- BenRG (talk) 19:25, 21 February 2013 (UTC)

I tend to agree that Minkowski's discovery of spacetime was a more important breakthrough than Einstein's original paper, but Minkowski's famous talk was in 1908 and I'm pretty sure it was Einstein's paper that inspired him to work on the problem. Minkowski died in 1909 and didn't do any work on general relativity as far as I know. Einstein initially didn't like the idea of spacetime but later said that he couldn't have discovered general relativity without it. -- BenRG (talk) 19:25, 21 February 2013 (UTC)

Indeed. Minkowski was Einstein's professor in Switzerland, and the two remained life-long collaborators, frequently critiquing and adding to each other's work. Minkowski provides the intermediary link between the special and general relativity theories: he developed his spacetime geometry as a way to simplify the mathematics behind special relativity; Einstein in turn used his unique four-dimensional geometry as a launching-off point to come up with his geometric description of gravity which forms the core of General relativity. These discussions are not to discount the singular genius of Einstein. It may have taken a dozen different people another dozen years to come up with what he did in the course of a much shorter time. But to say that doesn't mean that, had he not existed, all of those principles would simply never have been discovered or elucidated at all. He did not work in a vacuum, and had he not existed, others would have filled that void. Science works by answering the as-yet-unanswered questions (and also, it should be said, by asking the as-yet-unasked questions) and had Einstein not answered them, it seems impossible that no one else would have in the intervening years. --Jayron32 20:26, 21 February 2013 (UTC)

So far, the responses have focused on "how close" others were to Einstein's general theory. It sounds like the person who was closest, Hilbert, was doing pure math. That leaves the question of whether - even if someone had equations close to Einstein's - anyone would have given the specific thing great attention. (For a moment, let us say that Hilbert moved on to other things or whatever, like leaving equations in a notebook). Is it "natural" to develop the general theory of relativity, from the things that everyone was already looking at, such as the speed of light? Was there any particular reason to look deeply into that direction? What I mean to say, is that it is easy for me to imagine that, as quantum mechanics developed as something that physicsists could experiment with, and as in a practical sense everyone uses QM every day in electronics, etc, it is easy for me to imagine that we have QM today but nobody has invented general relativity. That would only be possible if it were possible for physicists not to really focus on the space that General Relativity is in . Could that have happened? How obviously was it in need of physicists' attention? 178.48.114.143 (talk) 18:39, 21 February 2013 (UTC)

From a modern perspective general relativity is the only relativistic field theory satisfying some pretty simple constraints (spin 2, no derivatives higher than the second... that may be all), so I'm sure it would have been discovered at some point. I'm actually kind of surprised it took Einstein 11 years. He had to discover almost everything from scratch, but still, it's not that hard. Part of the reason is that he lost several years to the hole argument.

It's sort of off topic, but one area where Einstein's influence seems to persist is in the typical presentation of the ideas he originated. Look at the lede of our article on general relativity: "General relativity [...] is [a] geometric theory of gravitation [...] the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present", etc. Now look at the lede of the article on gauge theory: "[A] gauge theory is a type of field theory in which the Lagrangian is invariant under a continuous group of local transformations. [...] The transformations between possible gauges [...] form a Lie group which is referred to as the symmetry group or the gauge group of the theory. Associated with any Lie group is the Lie algebra of group generators", etc. This despite the fact that gauge theory has a geometric character very similar to general relativity, and you can just as well describe general relativity in this relatively impenetrable way. You even frequently hear people saying explicitly that gravity is not like the other forces. So the answer to "how long would it have taken the general public to figure out that relativistic gravitation is about the geometry of spacetime, if not for Einstein?" may be "at least 108 years, if not forever".

Likewise I'm sure no one would ever say that special relativity is based on two postulates if not for Einstein, I doubt anyone would ever introduce it using trains, and the awful word "observer" might never have entered physics (though that's not really Einstein's fault—he used it in its ordinary vernacular sense, not the weird technical meaning that it somehow acquired later). On the other hand you don't hear much about his "general principle of relativity" these days. -- BenRG (talk) 19:25, 21 February 2013 (UTC)

Wow, Ben, you grade hard. Remember that Einstein, with (in his own estimation) limited mathematical talent, had to learn differential geometry from scratch — a challenging course for mathematics doctoral students, and at the time, far less neat and polished (and influenced by GR specifically) than it is today. --Trovatore (talk) 08:52, 22 February 2013 (UTC)

But he had the right idea from the beginning with the equivalence principle and I think he was working like a dog that whole time. And he was Einstein. Oh well, history proves you right.

It's actually fairly surprising that real mathematicians didn't work all of this out a half century earlier. Sylvester understood the geometric meaning of positive-definite quadratic forms and proved his law of inertia in 1852, but it doesn't seem to have occurred to him (or anyone else) that there might be a more general kind of geometry corresponding to general quadratic forms. If it had been discovered, it's plausible that someone would have thought of applying it to physics, especially after Maxwell invented relativistic field theory in 1861. And Riemann, who died in 1866, actually tried to construct a geometric theory of gravity at the end of his life, and surely would have succeeded if he'd had the spacetime concept.

Quantum mechanics, on the other hand, I don't see how anyone could have anticipated. -- BenRG (talk) 04:13, 23 February 2013 (UTC)

Quantum mechanics certainly filled a HUGE hole in the existing theory, though. Someone had to solve the problems where experimental data didn't fit classical explanations, the Ultraviolet catastrophe established the clear need for a new theory. --Jayron32 04:20, 23 February 2013 (UTC)

This kind of thing is hard to prove conclusively - but if we look back to an era when new theories were not spread across the scientific community in a matter of days, there are many cases of similar breakthroughs being made completely independently. Calculus is a great example of that. Evolution is another. It seems that some level of 'background' math/science/data has to happen before it's possible for the next great thing to pop into someone's head - but once it does, someone will pick up on it in a matter of a few years. SteveBaker (talk) 20:14, 21 February 2013 (UTC)

Maxwell should have invented it. 23:04, 21 February 2013 (UTC) — Preceding unsigned comment added by Count Iblis (talk • contribs)

And had Faraday been a more accomplished mathematician, he should have beat Maxwell to explaining electromagnetism. So...Faraday should have invented it? Someguy1221 (talk) 09:22, 22 February 2013 (UTC)

Perhaps, but I think this was more about having the mind of a physicist than being extremely talented in math. So, I don't think David Hilbert or Poincare had the right stuff do develop even special relativity, despite Hilbert being able to look at a mathematical problem Einstein was struggeling with while working on general relativity and instantly finding the solution in his head (he didn't tell Einstein), while Einstein needed many more months of hard work to find it. Had someone like Einstein, Newton or Dirac lived in the early 1800s then I think special and general relativity would have been developed almost a century earlier. But you may not have gotten that result with some exceptional mathematician in that position (e.g. Euler, Gauss, von Neumann, Hilbert, Godel, etc. etc.). Count Iblis (talk) 12:23, 22 February 2013 (UTC)

I'm surprised no one has linked to these two articles: Multiple discovery and List of multiple discoveries. Ariel. (talk) 20:12, 22 February 2013 (UTC)

Average energy obtained for hydrolysis of a glycosidic bond and for a peptide bond

Anyone have a book or table which tells them what is the average energy obtained from hydrolysis of a glycosidic bond and also of a peptide bond? Many thanks, Kinkreet^{~♥moshi moshi♥~} 09:22, 21 February 2013 (UTC)

The change in enthalpy is often close to zero; entropic considerations will vary widely depending on the amount of water (free solution or crowded gel-like cell cytoplasm?), amount of product/starting material and steric considerations. 70.33.147.106 (talk) 02:28, 22 February 2013 (UTC)

pupae

Pupae found in Johannesburg Feb 2013

In Johannesburg, South Africa where i am currently on a holiday, the following pictures show what has been found on numerous walls. The pupae measure from 0.5 cm to 1 cm in length. I have been advised that a small black worm emerges from these and then will proceed to crawl up the wall pulling the shell or the pupae case with it. These are found usually at about head height or between 1.5 to 2 meters above the floor. I would please like your help in determining what this is. Thank you — Preceding unsigned comment added by Antonce (talk • contribs) 09:35, 21 February 2013 (UTC)

You will first need to upload the picture onto Wikipedia, or more preferably upload it somewhere else and provide a link to it. Simplying giving the pathway to the file on your computer does not actually allow us to see the picture. Kinkreet^{~♥moshi moshi♥~} 09:38, 21 February 2013 (UTC)

If what emerges is a larva, then this is an egg, not technically a pupa. See this similar thread on a South American bug. μηδείς (talk) 15:46, 21 February 2013 (UTC)

If what emerges is a larva then it is inside a larval case, as found commonly with the large number of bagworm moths and caddisflys among others. There are many species of bagworm moths in South Africa, see here and I suggest it is one of those possibly seeking a site to pupate. Richard Avery (talk) 08:16, 22 February 2013 (UTC)

Materials that are compatible with the use and storage of chlorine pentafluoride, perchloryl fluoride, monomethylhydrazine, and diethylenetriamine?

Materials that are compatible with the use and storage of chlorine pentafluoride, perchloryl fluoride, monomethylhydrazine, and diethylenetriamine? — Preceding unsigned comment added by 192.248.248.55 (talk) 21:27, 21 February 2013 (UTC)

Building a rocket are we? Those are without exception very nasty chemicals without many uses, I don't think this is one the RefDesk should field. Fgf10 (talk) 22:00, 21 February 2013 (UTC)

Sorry, but Wikipedia is not censored. We do have a policy of not answering questions that require medical diagnosis or legal advice, but questions about nasty chemicals are allowed. (It may very well be that they shouldn't be allowed, but the way to do that is to change the policy).

Wikipedia isn't censored, but please note that this is information not advice. In other words, if someone tells you that a substance is compatible with them, that does not mean that when you actually order something made of it off the Internet it won't have a contaminant, grease coating, etc. that would react 'vigorously' and cause a bad day. To quote Willy Wonka where our co-contributors are concerned, "No, no. I won't hold you responsible..." Wnt (talk) 00:29, 23 February 2013 (UTC)

192.248.248.55, start with reading the following articles (be sure to read the articles they link to as well): chlorine pentafluoride, perchloryl fluoride, monomethylhydrazine, and diethylenetriamine.

Then read Explosive material, Chemical explosive, Explosives safety, and Blast wave. Twice. Then decide on a safer propellant. One of the chemicals you list is a toxic gas, and one small leak will burn your skin and completely destroy your lungs. Not a nice way to die. --Guy Macon (talk) 04:17, 22 February 2013 (UTC)

According to John D. Clark, a good pair of running shoes should be compatible with all of them. --Carnildo (talk) 03:36, 23 February 2013 (UTC)