Wikipedia:Reference desk/Archives/Science/2013 February 20

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February 20

Recurring smell

we can't give diagnoses or medical advice
The following discussion has been closed. Please do not modify it.
Hello all, there's something I'm wondering about. Just today, there was an incident at the refinery: a flange joint in one of the petrochemical units let go and caused quite a large spill of acetic anhydride. Thank God we contained it quickly and nobody got hurt, but the vapors entered the control room through the HVAC system and stank up the place pretty bad. I, in particular, inhaled a rather large amount of the vapor -- I didn't evacuate because I was too busy shutting down the unit, and I had tossed my gas mask to a young white lady who had lost hers, and who also had to stay at her post. To make a long story short, I had one of the highest exposures to the chemical, but I was fine (except for developing a runny nose and a slight cough). My question, though, is about a unique experience I had some hours after the incident: I had smelled the distinctive stench of the anhydride at the time of the incident, but it went away after the vapor dissipated -- however, and that's the unusual part, when I ate a tomato for dinner a few hours later, I instantly smelled acetic anhydride once again! Why is that? Did I have some of that stuff stuck to the back of my throat all that time between breathing it in and eating a tomato? Or was there something else at work? Thanks! 24.23.196.85 (talk) 07:10, 20 February 2013 (UTC) Oops, forgot to sign my comment. Fixed now. 24.23.196.85 (talk) 07:11, 20 February 2013 (UTC) Possibly related to Olfactory fatigue but consider seeing a doctor. Rmhermen (talk) 07:35, 20 February 2013 (UTC) Could also be some of the vapour was still in the bottom of your lungs, and you took a slightly deeper breath than usual when eating the tomato. 124.191.176.222 (talk) 07:44, 20 February 2013 (UTC) I didn't think that was produced from oil, does petrochemical works here just mean general chemical works including oil products or does it really use oil originally? That was dangerous not having proper safety equipment easily available for all staff who might be present whatever about them not individually following regulations. Dmcq (talk) 09:27, 20 February 2013 (UTC) One should not exclude the possibility that this story is made up. This IP asks a lot of weird questions. Looie496 (talk) 16:44, 20 February 2013 (UTC) I can't speculate with any certainty, but what we do know is that acetic anhydride is not stable in the presence of water, so it didn't "adsorb" and hang on unnoticed. I wonder if there is just maybe a chance that some fairly dry mucosa in the throat could react with it in the gas phase (to become <something> acetate) and then release the acetate by acid hydrolysis. I should echo other sentiments that I'm answering this solely as a gee-whiz question - if you have any reason to feel that this symptom is somehow unpleasant or harmful, or if you are concerned about your health, this isn't an answer worth consulting and you know where to get one. Wnt (talk) 17:24, 20 February 2013 (UTC) we can't give diagnoses or medical advice μηδείς (talk) 23:34, 20 February 2013 (UTC)

Not medical advice, just wondering. For the record, I did see a doctor that same day and he told me I should recover completely in a few days. And yes, the plant does make acetic anhydride (among many other things) from the ethylene produced by the FCC unit. 24.23.196.85 (talk) 06:40, 21 February 2013 (UTC)

Good to hear that. And thanks very much, I should really have checked with Google as it knows a lot more than me and is more up to date ;-) Dmcq (talk) 17:13, 21 February 2013 (UTC)

Rubbing two stones

When we rub two stones a spark is produced. How is this spark produced? I think this is due to electric discharge. 106.218.237.192 (talk) 08:30, 20 February 2013 (UTC)

It depends on the stones and on the type of spark. There are at least three possible processes. Triboelectricity, which is produced by rubbing any two materials together, and piezoelectricity, produced by distortion of certain crystalline materials (and used in some barbecue igniters) both produce purely electric sparks. The sparks seen with flint and steel (or flint and iron pyrite) are actually tiny particles of iron being shredded off and burning rapidly in air. TenOfAllTrades(talk) 14:34, 20 February 2013 (UTC)

Note, though, that most "flints" these days are actually man-made ferrocerium, where the steel scrapes off small shavings of ferrocerium, which then ignite. This is backwards from traditional flints, which, as you mention, make sparks by scraping off and igniting pieces of the steel. -- 205.175.124.30 (talk) 19:52, 20 February 2013 (UTC)

When stones hit each other they do so at point, which concentrates a lot of energy into that point. Because stones are made from hard minerals that do not deform much, that energy is not spread around so much, but instead heats and breaks off that point to make a hot flying fragment of mineral, a spark. Graeme Bartlett (talk) 20:32, 20 February 2013 (UTC)

Do the two stones become charged when they produce spark? Is this spark produced due to electrons or due to huge energy? 106.218.108.227 (talk) 02:14, 21 February 2013 (UTC)

Mostly just due to the intense energy concentration. Selected minerals may have the piezoelectric effect, but they are not likely to be the ones commonly found in rock. The Spark (fire) article also indicates that low thermal conductivity is conducive to spark formation. Graeme Bartlett (talk) 10:39, 22 February 2013 (UTC)

Space-time

We know our sun has created a huge depression in space-time and the earth revolves around the sun in that curvature. Anything revolving around a curved surface roll down below the base of the surface. Why don't earth roll down below the center of that depression made by sun? 106.209.197.10 (talk) 10:05, 20 February 2013 (UTC)

Because the depression is not two-dimensional, as is commonly shown in poorly-diagrammed science shows. The depression is three-dimensional, and the Earth accelerates toward the sun's center of mass, not toward an imaginary point beneath it. Evanh2008 ^{(talk|contribs)} 11:02, 20 February 2013 (UTC)

Because the earth has velocity perpendicular to the direction of the sun. Even in the oversimplified 2D model with depression in the third dimension a ball with initial velocity would not fall in straight but spiral in. And this only because it looses kinetic energy due to friction. Without friction, it would circle around the depression endlessly. 95.112.187.252 (talk) 12:03, 20 February 2013 (UTC)

It should be noted that there really is no depression at all, that's just an aid to visualizing the scenario. In relativity, objects move along geodesics in curved space -- in other words, gravity causes a curvature of space, and objects move through that curved space as if no force was acting on them. But when you have a ball rolling near a depression, you need an external downward force to get anything that resembles gravity. Looie496 (talk) 16:40, 20 February 2013 (UTC)

Newtonian gravitational potential

General relativistic spacetime curvature

If you see a picture like the first one on the right, it's a graph of the Newtonian gravitational potential, and you can think of objects moving in that potential as rolling along it under the action of a constant downward vertical force. If you turned the graph upside down the direction of the apparent central force would switch from attractive to repulsive. This has nothing to do with general relativity, despite what you'll read in a lot of books.

If you see a picture like the second one, that's a genuine embedding of general relativistic spacetime curvature. It's a surface in 3D space, not a graph. Because only the curvature matters, turning it upside down (or sideways) makes no difference; the effective force is always attractive. To see why, you can cut out a circular piece of paper, draw a straight line (chord) on it, cut out a narrow pie slice that doesn't intersect the line, tape the two edges of the slice together so you have a cone, tape it to a flat sheet of paper, and temporarily flatten the cone near the ends of your chord so that you can continue it to a straight line on the flat sheet of paper. You will find that the line as a whole curves toward the central point, even though it's locally straight everywhere. Of course it would be the same if you had taped the cone underneath the paper instead.

All that said, the earth doesn't fall directly into the sun because it's in orbit, and it doesn't spiral into the sun (on any realistic time scale) because there's very little friction. Incidentally, I seem to recall that if gravitation were a vector force like electromagnetism, the earth would have spiraled into the sun by now. Gravitational friction is much lower because there is no gravitational dipole radiation, only quadrupole radiation and above. -- BenRG (talk) 18:33, 20 February 2013 (UTC)

Even in that Newtonian scenario the picture is only a visualization aid. If you think of the height as the potential energy, then a vertical slope would correspond to an infinitely large force. But an object falling into a hole does not experience an infinite force when the walls of the hole are vertical. It's still just a metaphor, not to be taken too literally. Looie496 (talk) 19:38, 20 February 2013 (UTC)

It's more than just a visualization aid. In a constant vertical gravitational field the height is proportional to potential energy, so a small object resting on a properly scaled potential energy graph will actually have the correct potential energy. When it's moving, though, it has too much kinetic energy because of vertical motion and rotation. You could minimize friction and solve the rotation problem by using a sliding puck on a curved air hockey table. I don't see how to solve the vertical motion problem, though. -- BenRG (talk) 22:37, 21 February 2013 (UTC)

The mass of the solar system is slightly less than the masses of sun and planets individually

Well, we all know the reason why the mass of atomic nucleus is slightly less than the masses of neutrons and protons individually. The mass of the solar system is slightly less than the masses of sun and planets individually. What is the reason behind the second statement ? Technologous (talk) 11:53, 20 February 2013 (UTC)

Where did you see the second statement? If the sum of a list of masses is different from that shown for the complete system, it could just be due to rounding. Rojomoke (talk) 13:30, 20 February 2013 (UTC)

In this section of article "mass-energy equivalence" Technologous (talk) 13:43, 20 February 2013 (UTC)

It's nonsense. The Solar System consists of far more than the sun and planets.--Shantavira|^{feed me} 14:07, 20 February 2013 (UTC)

Whoa, let's not get carried away with the 'n-word'. If we take "the sun and planets" as shorthand for "all the mass in the solar system" (or, alternatively, the "the solar system" to mean just the Sun and its planets, and ignore the gas, dust, comets, asteroids, and all the other minor planetary detritus) then the statement actually does make some sense—if one is very careful in the way one chooses to define "mass". It is a restatement of the principle that any gravitationally bound system will have an apparent mass that is less than the sum of the masses of its constituent parts, if those parts were separated. The energy of any gravitationally-bound system is lower than the energy of free particles (or planets) by the amount of their gravitational binding energy; by mass-energy equivalence, the apparent mass of the gravitationally-bound system is lower as well.

That said, I haven't run the numbers through but I would be very surprised if the difference in apparent mass actually came out to be more than rounding-error-sized for any body in our solar system. More interesting results might be obtained for bodies in close orbit of neutron stars or black holes. TenOfAllTrades(talk) 14:28, 20 February 2013 (UTC)

It is in the noise, but perhaps not as far in the noise as one might guess. The gravitational binding energy of the Sun is slightly more than the mass-energy of the entire Earth. Dragons flight (talk) 18:45, 20 February 2013 (UTC)

Question about a strange polymer

I had a strange dream about a polymer yes I know this is kind of perverted. Now I wonder if there is any chance of knowing the properties of this polymer.

The base molecule was pentane modified to have 2 adjacent ketone on one end and a double bound on the other, H(CO)-(CO)-(CH2)-(CH)=(CH2) (I know the first group really is an aldehyde as long as not polymerized, and polymerization would probably destroy the O-double-bound rather than remove the H). On the completed polymer there were also side-chains one on each base molecule. The dream was not clear on how they were attached, but it was -(CH2)10-(C6H4)-Cl, whit the chlorine in para position.

Thanks for any clue about that. 95.112.187.252 (talk) 12:23, 20 February 2013 (UTC)

There seem to be two steps to the question here. The first, of general interest, is "what properties does an unknown polymer have?" for us to measure. I'd like to hear that. The second involves guessing out the answers to those, and is more problematic.

Nonetheless, I assume anything with those long saturated carbon chains would be very oily, and with so much of the polymer made up of dead-end chains, I assume it wouldn't be very strong. I kind of wonder if the Cl's could make it possible for it to work like phospholipids or a soap, forming micelles and vesicles and such, but I suspect there isn't really enough polarity there to make it work very well. Wnt (talk) 17:43, 20 February 2013 (UTC)

Well, I didn't have the hope that this polymer was known by some name or had a wiki page of it's own. In the dream it was indeed oily, milky in appearance with a yellowish hue, building sharp droplets as if from a high surface tension. The two adjacent ketone groups featured really prominent, and I wondered (even inside the dream) if such thing could be stable at all. Another thing was that it was a conductor for electricity. Is there any chance of that, or can that be excluded by the structure? Another curious thing was that, as a kind of secondary structure, four of those chains would be entwisted into one, somehow in the way two DNA strains are twisted into one, but with the side-chains still pointing outward. Is anything like that known to happen in real live? 95.112.187.252 (talk) 20:46, 20 February 2013 (UTC)

Well, vicinal diketones like diacetyl and pentanedione do exist. I wish I were more qualified to say what properties they have... Wnt (talk) 00:32, 21 February 2013 (UTC)

For a polymer to conduct electricity, it must have conjugated pi-bonds (as in the case of polyacetylene, for example). 24.23.196.85 (talk) 06:43, 21 February 2013 (UTC)

Agreed - sorry, forgot about that part. I came up with a search result that acetone has conductivity 0.02 uS/cm (18 C) to 0.06 uS/cm (25 C). I'm having an amazing amount of difficulty deciding whether that is really equal to 2 uS/m as the math suggests, but in any case it is somewhere well under that of water. But I didn't find a figure for diacetyl to compare. Wnt (talk) 17:34, 21 February 2013 (UTC)

Momentum gained by body = Force x Time during which force acts

How can we proof that Momentum gained by body = Force x Time during which force acts ? Not homework. — Preceding unsigned comment added by 106.209.218.22 (talk) 13:21, 20 February 2013 (UTC)

There is useful information in momentum. -- SGBailey (talk) 16:20, 20 February 2013 (UTC)

If we define force as the rate of change of momentum with respect to time then change in momentum is the integral of force with respect to time. If a constant force is applied for a given time interval then this simplifies to give us change in momentum = force x time interval. Note that in the general case both force and momentum are vectors. Gandalf61 (talk) 07:23, 21 February 2013 (UTC)

Tonsillar cancer

Do we have an article dedicated to cancer of the tonsils, and if so, what is it? Tonsil and Oral cancer mention it somewhat, but only in passing, while Palatine tonsil doesn't mention cancer at all. Tonsil cancer and Tonsillar cancer could stand to be created as redirects, but I'm not sure what their targets should be. Nyttend (talk) 19:30, 20 February 2013 (UTC)

Tonsils are lymphatic tissue, so I would guess that tonsil cancer would fit under Lymphomas. Not sure, but that'd be my best guess. --Jayron32 20:14, 20 February 2013 (UTC)

No, lymphomas are blood cancers. It's the lymphocytes themselves that proliferate, not the solid tissues they're associated with. --Trovatore (talk) 20:19, 20 February 2013 (UTC)

See Oropharyngeal cancer. Duoduoduo (talk) 20:27, 20 February 2013 (UTC)

Liquid with highest boiling point

Resolved

Of all reasonably non-flammable substances that are liquid at room temperature, which has the highest boiling point? Horselover Frost (talk · edits) 23:20, 20 February 2013 (UTC)

Well mercury has a reasonably high boiling point of 356.7 °C (note that mercury vapor is toxic). And gallium has a melting point just above room temp, at 29.78 °C, but a boiling temp way up at 2403.0 °C. Alloys of gallium, such as galinstan, are liquid at room temperature, but also have a bit lower boiling temperature, although still > 1300 °C. StuRat (talk) 23:31, 20 February 2013 (UTC)

A quick look shows that not only is gallium perfect for what I had in mind, it's already used in similar applications. Thanks! Horselover Frost (talk · edits) 21:51, 21 February 2013 (UTC)

You're quite welcome. I'll mark this Q resolved. If you disagree, please remove the resolved tag. StuRat (talk) 04:59, 22 February 2013 (UTC)

What about some of the high melting point glass types? Glass is chemically liquid at room temperature isn't it? Or do you mean runny liquid? --BozMo talk 23:39, 20 February 2013 (UTC)

Glass is a brittle solid at room temperature, per the article, not a liquid. Glass lenses hundreds of years old and Roman glass a couple of thousand years old have retained their shape. Edison (talk) 23:47, 20 February 2013 (UTC)

I've heard glass referred to as a "supercooled liquid", as per window glass which can shrink from the top over the course of many decades. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:51, 20 February 2013 (UTC)

That's just an urban legend[1][2][3]. Some builders took the time to install the thinner side of the glass up, some didn't.Dncsky (talk) 23:55, 20 February 2013 (UTC)

Glass is properly an amorphous solid which is a phase of matter that lies somewhere between a solid and a liquid. It is liquid-like in the arrangement of the molecules: they are not arranged in an organized crystal lattice like other solids, instead they are arranged in a liquid-like organization. However (and this is a big however), the molecules themselves don't have any translational motion: that is, individual molecules remain "locked in" to their location in the glass, which is the basic definition of a solid. The main component of glass, silicon dioxide has crystalline solid forms (quartz), glass being the non-crystalline solid form of silicon dioxide. However, glass is still unambiguously a solid. Just one with a liquid-like organization. --Jayron32 02:44, 21 February 2013 (UTC)

What it doesn't have, though, is any well-defined melting point. --Trovatore (talk) 03:38, 21 February 2013 (UTC)

That's tautologically the definition of a "glass". See glass transition. --Jayron32 04:26, 21 February 2013 (UTC)

Perhaps, but it seems like thermoplastics are similar, in this respect. For that matter, so are oils and gels. StuRat (talk) 05:26, 21 February 2013 (UTC)