Wikipedia:Reference desk/Archives/Science/2015 December 14

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December 14

Were coalition troops prepared for/expecting an attack with chemical/biological weapons?

The question above made me curious about what the governments knew in 2003. Officially, the governments claimed there were MD weapons, but did they act coherently to this official position? During the invasion, were coalition troops provided with materiel to protect themselves against a chemical/biological attack? --Denidi (talk) 13:25, 14 December 2015 (UTC)

Yes: "Allied troops then invaded Iraq, taking great precautions in case chemical weapons were used against them." From Medical Aspects of Chemical Warfare, The Surgeon General Department of the Army, United States of America (p. 66). Alansplodge (talk) 14:06, 14 December 2015 (UTC)

In this particular case we can work out which you're talking about because you mentioned the year, but you do really need to give more details. Which government are you talking about? There were four countries involved in the initial invasion, and there was the Iraqi government on the other side. The poster above assumed you are talking about the US government, is this the case? Fgf10 (talk) 14:23, 14 December 2015 (UTC)

UK troops would also be of interest. The other two countries, Australia and Poland, sent only token troops.

The Australian contribution was small, but I wouldn't say it was only token. According to Australian contribution to the 2003 invasion of Iraq#The scale of the Australian force commitment, their contribution was 2.42% of (I think active duty) military personnel compared to 4.85% for the US. This is only slightly under half of the US, and it's difficult to argue the US contribution was close to token. Or to put it a different way, even if the US had only contributed 73,000, it would still be difficult to argue it was token. The relative size of the contribution by Australia was tiny but that's because Australia has a much smaller military, partially because they have a much smaller population. Post invasion, the Australian contribution was somewhat minor compared to the contribution from the US and others so could probably be called token, but your comments seem to be referring to the invasion only. Nil Einne (talk) 19:53, 14 December 2015 (UTC)

The United States military very much operated as if the threat from chemical or other unconventional weapons was real. This included provision of training and materiel, as well as operational, organizational, and doctrinal changes.

From the collection at United States Army's Combined Arms Research Library at Fort Leavenworth:

On Point : the United States Army in Operation Iraqi Freedom, by Col. Greg Fontenot et al., has extensive discussion of NBC preparations during the invasion. For example, Countering Iraqi WMD And Ballistic Missile Strikes (pg. 171) discusses plans and operations. In addition to lots of doctrine and organizational information, there are also anecdotes so you can see what "preparation" meant to ordinary front-line soldiers:

"On 28 March 2003, the platoon was in a blocking position near the “Airfield.” Both Horner and Jackson had just awakened and were eating MREs in the back of the company’s cargo truck. The unit received artillery fire, and an adjacent chemical unit’s alarms went off. It also received warning to don protective overgarments and masks immediately. As their masks had been destroyed [in the vehicle fire], their squad leader (Staff Sergeant Carver) had them run to the back of one of the M2s to have some protection. He also had them pull the hoods of the NBC suit as tightly as possible over their heads. By this time the entire company, as well as the chemical unit, was in MOPP 4."

On Point II : transition to the new campaign : the United States Army in Operation Iraqi Freedom, May 2003-January 2005, by Donald Wright and Col. Timothy Reese:

"Reorganization to meet the campaign’s requirements often meant huge growth in the number of commands under divisional authority. At one point, 1st AD added the 937th Engineer Group and the 18th Military Police Brigade, giving it the equivalent of 9 maneuver brigades and almost 39,000 Soldiers. The division accepted further reinforcements, such as a CA brigade, a chemical company, PSYOP companies, and an aeromedical evacuation detachment. Every division in theater underwent its own version of organizational transition as they rapidly adapted to the requirements of the new campaign in Iraq."

Prior to Operation Iraqi Freedom, an ordinary Army division would not normally include a chemical warfare company. This book also contains a photograph of U.S. Army chemical warfare soldiers preparing and reconditioning their equipment in Iraq, to keep it battle-ready.

Even outside of chemical warfare companies, ordinary troops were issued NBC suits. I am not sure if these were universally issued to all American soldiers.

Nimur (talk) 15:28, 14 December 2015 (UTC)

There was a bit of a rumpus when it was discovered that the British Army didn't have enough NBC equipment for everybody; see BBC News - UK troops 'left without key kit' (2003). I'm certain that the intention was for everybody to be protected, but as usual, it didn't go to plan. Alansplodge (talk) 16:32, 14 December 2015 (UTC)

Measuring the mass of non-detected dark matter

This source and our article Large Underground Xenon experiment both give the impression that, by failing to detect even a single dark matter collision, the experiment can place constraints on the mass that dark matter WIMPs must have. But how can anyone predict the likelihood that a WIMP with a given mass will interact with a xenon atom, never having seen one? Wnt (talk) 18:16, 14 December 2015 (UTC)

The weak interaction is fairly well understood, and predictions can be made about the statistical probability of a particle with specific properties (like the Lightest Supersymmetric Particle) interacting with bulk matter. Although absence of evidence is not evidence of absence, the lack of a single observed collision provides strong evidence that the particular predicted particle is not common (and hence that the whole theory might need re-thinking). Dbfirs 18:44, 14 December 2015 (UTC)

The article glosses over what exactly it is they are able to rule out. It's not really a range of masses, but a region in the 2D plane of mass and scattering cross-section. Other experiments had seen events that could be interpreted as a possible detection at low mass and a particular range of cross-sections. LUX was able to exclude those detection regions. You can see the exclusion region in Fig. 3 of the new paper. A different view, zoomed in on a low-mass region, including some other experiments' possible detection regions, and using older limits, is in the third figure here. --Amble (talk) 21:41, 14 December 2015 (UTC)

Bowel Movements

Do individuals hooked up to nutritional IV long term still have bowel movements. Additionally, if a person had their entire digestive system removed including colon, and they were kept alive with the nutritional IV would they still need to excrete, some how? — Preceding unsigned comment added by 24.215.64.134 (talk) 18:53, 14 December 2015 (UTC)

Despite lacking food, the body still produces matter to excrete as it breaks down red blood cells. In cases where the intestine is either removed or bypassed, the gut is attached to the skin and an opening is produced called a stoma, through which the matter is excreted. See for example ileostomy. --TammyMoet (talk) 19:39, 14 December 2015 (UTC)

[ec] See Parenteral nutrition and this factsheet from the NHS. According to the latter, "[t]he bowel will still produce mucus, cells and bacteria even though food is not being eaten and so you are likely to still have a bowel movement". I don't know of any surgical procedure that involves removing the _entire_ digestive system (from the oesophagus to the anus) which the patient is expected to survive; any remaining part of the digestive tract (after, for example, colectomy) will still produce some mucus which will need to go somewhere. Tevildo (talk) 19:45, 14 December 2015 (UTC)

I should add that, as if biology were determined to defeat our pretensions of simple causal logic, babies produce meconium before they ever eat. Wnt (talk) 16:18, 15 December 2015 (UTC)

It's not really the case that they don't eat...they swallow amniotic fluid in the womb. You try floating in something for nine months and not swallowing any of it. Of course, there isn't much nutrition to be had from it. --71.119.131.184 (talk) 23:48, 15 December 2015 (UTC)

Poorly designed battery: fire by discharging?

Can a poorly designed Li-ion battery catch fire by discharging too fast? Or, could another problem arise, like smoke or leaks?--3dcaddy (talk) 23:25, 14 December 2015 (UTC)

Yes. It can overheat, damage the separator between anode and cathode, cause a short-circuit, and explode. This is a situation known as thermal runaway.--Denidi (talk) 02:20, 15 December 2015 (UTC)

I'm actually not sure that "poor design" has anything to do with it. If you include "shorting them out" within the definition of "discharging too fast" then almost certainly you will see smoke and possibly fire. I've "disposed" of several such batteries by shorting them out, after they've out lived their useful life, and they've all been varying degrees of spectacular. Vespine (talk) 04:48, 15 December 2015 (UTC)

Indeed, for short-circuiting it, you won't need to be discharging, nor it is related to discharging. That's also why the FAA regulates how batteries can be carried by passengers. But I meant it as a process. When you are discharging the battery it can overheat > damage the membrane > short-circuit internally (=>more heat) > fire/explode. --Denidi (talk) 15:20, 15 December 2015 (UTC)

Gravity trains and the rotation of the earth

I was thinking about Gravity trains and realized that when you enter the train you are rotating one way, but when you exit you are rotating the opposite direction. That means that the entire trip would be spent with the train pressed first against one side of the hole and then the other, with an acceleration of about .04g, rather than, as said in the article: "During this entire trip, the train (and all passengers) would be practically weightless.". Am I correct? The article makes no mention of this at all. Ariel. (talk) 23:27, 14 December 2015 (UTC)

Indeed, you need to consider two factors: the coriolis force and the conservation of angular momentum, both of which considerably complicate the mathematical treatment of the trajectory. Although the first simplistic approximation you learn (by application of Gauss's law for gravity) is that the object in the hole is a "simple harmonic oscillator," the trajectory is in actual fact that an orbit through a non-uniform gravitational field.

I think there is a homework problem on this issue in Marion and Thornton, but I don't recall if they work the solution. I can check later today.

Nimur (talk) 23:47, 14 December 2015 (UTC)

The "tunnel through the Earth" oscillator was in fact Homework Problem 5-15, in the fifth edition, but it does not actually ask about the rotational effects. However, several problems in Chapter 10 (on rotating reference-frames) ask for re-calculation of earlier chapters' homeworks assuming a rotating Earth. If you can follow the math in these two chapters, you can correctly answer your question about the gravity-train. The calculus is non-trivial - there are a lot of vector cross-products in the equations - but as you intuitively guessed, there will be a non-vertical force that should not be neglected. Nimur (talk) 03:45, 15 December 2015 (UTC)

The tunnel could be dug with the curved path taken into account, allowing zero gee - specifically, you could emerge 42.2 minutes of rotation west of the antipodal point, which is to say 42 / (60*24) * 360 = 10.5 degrees. However, of course, that means that a reverse trip would either have double the acceleration, or have to use a whole different tunnel that ends up 21 degrees west of the original... Wnt (talk) 04:03, 15 December 2015 (UTC)