Wikipedia:Reference desk/Archives/Science/2016 July 17

= July 17 =

Physics curiosity
Suppose, I can move at the speed of sound. When a speaker speaks then simultaneously I also start to move at the direction of sound at the speed of the sound then what sound will I hear if the speaker has said "Hello"? and if I myself speak any word then will I be able to hear my own voice incase i move faster than sound? — Preceding unsigned comment added by Sahil shrestha (talk • contribs) 02:15, 17 July 2016 (UTC)


 * You won't hear the speaker, since you and the speaker's sound waves will be moving at the same speed. The sound waves need to hit your eardrums for you to hear them. Assuming you're inside a craft, you will be able to hear yourself just fine. There are myriad videos of people speaking just fine inside aircraft traveling at supersonic speeds. The thing to remember here is that speeds in general are relative to a frame of reference. If you run around inside an aircraft in flight, we don't consider you to be running at 100+ kilometers per hour, because we measure your speed relative to the body of the aircraft. The air inside the craft is being carried along with you, and it's at rest relative to you. (If we posit that you have superpowers and aren't flying in a craft, you might have trouble speaking due to the air barreling down your airway, though you'd need some secondary superpowers anyway to be able to breathe and not have your lungs explode, or to not require breathing.) --71.110.8.102 (talk) 06:23, 17 July 2016 (UTC)


 * Note that I interpreted the questioner's statement as "you move in the same direction as the speaker's sound waves", in other words, away from the speaker. Re-reading it, it seems unclear. --71.110.8.102 (talk) 06:28, 17 July 2016 (UTC)

You might be interested in the doppler effect. As you are moving away from the speaker, the apparent frequency of the sound he makes will get lower the faster you move away from him. When you reach the speed of sound, all aspects of the speaker's voice drop to a frequency of 0, and you can no longer hear anything at all from him. As for your own voice, well, that depends on what factors you want to include. As 71.110 mentioned, your exposed body were simply flung through the air at the speed of sound, you would be dead. If we ignore that, you'll just hear your voice normally through the vibrations in your skull, though that may be drowned out by the rushing air. If we ignore all of these factors, that depends on where the sound is generated relative to your ears. Sound moves at the speed of sound relative to the air itself, not the speed of the sound-maker. A super sonic jet, for instance, does not project any sound ahead of itself. It does project sound in the forward direction, but at the speed of sound relative to air, which it is outrunning. So if your sound is being made ahead of your ears, you will hear it doppler shifted to a very high frequency. If your sound is being made behind your ears, you will not hear a thing. Again, ignoring all these other little factors. Someguy1221 (talk) 06:35, 17 July 2016 (UTC)
 * @Sahil, the Good News is that you can move at the SoS (Speed of Sound) which is 343.2 m/s. Just stand at the Equator where you and everything around you are moving eastwards at 465.1 m/s. That's faster than you want, but knowing that the surface rotational speed is proportional to the cosine of the latitude you can reposition yourself north (or south) to latitude 44.45° (or minus 44.45°) to adjust your speed to the SoS. At least you could have done, had not astronomers discarded the geocentric in favour of the heliocentric system in which everything at the equator is moving at about 79000 m/s due to Earth's orbit around the Sun. So the Bad News is that makes it very difficult, short of a major investment in rocketry, to move as you suppose. See Orbital speed, Geocentric model and Heliocentrism. AllBestFaith (talk) 17:34, 17 July 2016 (UTC)
 * That doesn't really figure into it, as per the frame-of-reference cited earlier. If you are standing next to someone, your speed relative to the center of the earth, the solar system, the galaxy, etc. don't matter. Compared to each other, you're standing still. ←Baseball Bugs What's up, Doc? carrots→ 17:57, 17 July 2016 (UTC)

Why is the UK and US building different trident-armed submarines?
America is building the Ohio Replacement Submarine while Britain is building the Successor-class submarine. Both will cost around 7 billion each and they'll start to enter service in 2028/2031. Can anybody tell me the difference between them in terms of engineering/specs? Also, while not a science question, does anybody know why both countries aren't building the same? It'd be cheaper that way. 2.103.15.147 (talk) 02:30, 17 July 2016 (UTC)
 * Here is a free report available to the public from the RAND Corporation, a very famous American organization that has had very strong historical ties to the nuclear policy decision-makers in the United States government: The British Nuclear Deterrent After the Cold War (1995). It's a good overview that explains why things are the way things are.  There is a lot of politics behind the American/British Trident nuclear missile program, so this report will help give you some background.  And here is a 1984 report, British Nuclear Policy-Making.
 * Directly addressing the "costs" of the submarines: the author Nicolas Witney of the Ministry of Defence eloquently phrases it, in pleasant British English, "...such sums, though by no means trivial, do not weigh heavily when set set against the sunk costs and the importance long ascribed by successive British governments to the strategic deterrent." Or as I say it, in my brasher American idiolect, when we're talking about blowing up the planet, "money" ceases to have any meaningful economic implication.
 * Here is a well-cited article from the Fall 2003 RAND Review: Excessive Force: Why Russian and U.S. Nuclear Postures Perpetuate Cold War Risks.
 * Britain's choice to deploy an American-made nuclear weapon on a British-made nuclear submarine is rooted in their government's perceived need for their nation to have independent control of the nuclear arsenal, while satisfying domestic political concerns that preclude them from independently designing a nuclear weapon.
 * This 2007 book, part of the RAND Monograph series, Sustaining U.S. Nuclear Submarine Design Capabilities, defends the position that it is necessary for a nuclear-weapon-state to design a nuclear submarine fairly frequently to ensure that critical institutional knowledge and skills are preserved, in case that knowledge, skill-set, and engineering infrastructure is ever needed in the future. Surely, the decision-makers in the British government consider the very same issue.
 * Nimur (talk) 03:41, 17 July 2016 (UTC)
 * Here's a great resource from Royal United Services Institute - sort of a British counterpart to RAND: Continuous At-Sea Deterrence: Costs and Alternatives. In this report, there is considerable discussion (based on the theory of nuclear deterrence, which is another topic worth reading about).  On this topic, it is claimed that Britain cannot cease its continuously-available nuclear deterrence unless both the United States and Russia make significant policy-changes.  Ultimately - and this is a sinister conclusion that is very extensively studied - the UK cannot trust the Americans as an ally unless the UK maintains the credible capability to independently annihilate the Americans.  Our article on the so-called security dilemma has some references on the topic of uneasy alliances in nuclear strategy theory.  If you read extensively on the topic of why we even have nuclear submarines - particularly, with respect to the role nuclear submarines play in the theory of second strike capability, you'll find that this theme recurs very frequently.  Nimur (talk) 03:55, 17 July 2016 (UTC)
 * It should not be a matter for surprise that the British do not trust Donald Trump. In a worst-case scenario it might even be a matter of relief to the US public that Britain has something purporting to be an independent weapon that might deter. Unfortunately, by that time, Trump will know that he has an override. Thincat (talk) 13:48, 17 July 2016 (UTC)
 * The difference is that one is a pointless porkbarrel for local jobs in the US, the other is an even more pointless porkbarrel for jobs in the UK. In a part of the UK which might not even be in the UK for much longer. Andy Dingley (talk) 14:38, 17 July 2016 (UTC)
 * Actually very little pork for Scotland, but a lot for Barrow-in-Furness. Assuming you're not envisaging an independent Cumbria. HenryFlower 16:48, 17 July 2016 (UTC)
 * The UK ones are built in England, but based in Scotland - so that does create jobs in both areas. Wymspen (talk) 17:27, 17 July 2016 (UTC)
 * And retaining the actual ability to build submarines is important, if the Vickers Shipbuilding and Engineering yard at Barrow didn't have any submarines to build, those skills would be lost fairly quickly. Similarly, the ability to build nuclear warheads, as those are manufactured at the Atomic Weapons Establishment to a British design, drawing on "inspiration from U.S. warhead designs" according to our Trident nuclear programme article. Only the actual missile is made and designed in the US, since we gave up on the capability of building British ballistic missiles in 1960 with the cancellation of the Blue Streak programme. Alansplodge (talk) 16:09, 19 July 2016 (UTC)

conical pendulum -Referencedesk Archives/Science2016May31
If we disregard the force to start and maintain constant movement of a conical pendulum, are there any practical(scientific/commercial) purposes to which the force generated /the movement created can be utilised. Eg electrical generation in remote areas. Assume a small pendulum length of say 600mm.139.216.164.174 (talk) 21:03, 17 July 2016 (UTC)


 * Any attempt to extract work from the pendulum will quickly cause it to stop swinging. As you were told back in May, there is no such thing as a perpetual motion machine, and you can't get energy for free.  Rojomoke (talk) 21:32, 17 July 2016 (UTC)

Dogs protecting humans
There are many stories about dogs protecting humans, sometimes sacrificing themselves. This is very unusual; few animals will die for non-relatives. How much has this behavior been studied? 69.22.242.15 (talk) 22:03, 17 July 2016 (UTC)


 * Well, while the origin of the domestic dog is complex, they are definitely related to wolves, and some of those have an alpha pair that mate and produce offspring, while the rest of the pack does not breed. The rest of the pack are related to the alpha pair, though, so the best chance to pass on their genes may be to protect the alpha pair, even if they themselves die.  Since humans often take on the role of "alphas" in their relationship with dogs, this instinct may continue, even if it no longer is biologically "logical". StuRat (talk) 22:34, 17 July 2016 (UTC)


 * Even with children: In separate rattlesnake attacks, dog saves child and child saves dog. μηδείς (talk) 23:19, 17 July 2016 (UTC)

Cats protecting humans?
Inspired by the thread above. Why would a cat protect a human child from a dog attack? I thought that cats generally didn't care about anyone other than themselves?

Vid:

https://www.youtube.com/watch?v=aBW5dfRoG7Q

--146.90.107.28 (talk) 23:28, 17 July 2016 (UTC)
 * Cats care about their kittens and that mechanism is easily displaced (for lack of a better term) toward human family. Most interactions between humans and domestic cats can be explained in terms of parent-child relationships.  Ian.thomson (talk) 23:31, 17 July 2016 (UTC)


 * Yes, I've heard that the behavior of bringing live (but wounded) mice/birds/frogs to humans to finish off can be a manifestation of that. --146.90.107.28 (talk) 23:42, 17 July 2016 (UTC)


 * Hey Displacement_(psychology) is a similar concept, but I think Transference is the safer/more accurate word to use these days. SemanticMantis (talk) 16:35, 20 July 2016 (UTC)


 * I'm a little dubious about the video, which is shot from two different viewpoints which just happen to be perfect to capture all the action. Staged? {The poster formerly known as 87.81.230.195} 2.123.26.60 (talk) 00:51, 18 July 2016 (UTC)


 * The stationary, elevated cameras with timestamps feel like security cameras to me. It is plausible that one would arrange such cameras to cover a wide range of angles, though of course having multiple security cameras would be quite unusual for a private home.  Dragons flight (talk) 09:27, 18 July 2016 (UTC)
 * I don't know if it's really that uncommon for homes to have multiple cameras, particularly not in the modern digital and wireless world, as it's easy even for a fisheye lens camera (which this isn't anyway) to miss likely points of entry for even an unaware thief. Cameras are generally mostly as a deterrence, still even for home they are use as evidence and for monitoring. Nil Einne (talk) 19:05, 18 July 2016 (UTC)


 * We're interpreting the video as the cat saving the child. It might be doing so, but it might also simply be protecting its territory from an invader. Back when I had an outdoor cat, I observed it defending its turf from even large dogs when the humans were in no danger whatever. By that same token, our presence also seemed to galvanize the cat, who perhaps assumed that we would take up the fight against the foreign aggressors alongside it. As for this particular video, I don't see anything particularly suspect about it; they're fairly clearly security camera shots. Matt Deres (talk) 16:12, 18 July 2016 (UTC)
 * I agree totally with Matt. Modern ethologists have worked diligently to make their subject a "hard" science.  Interpretations such as "the cat saved my son" are simply unacceptable without further investigation.  Possibly, it was a highly defensive cat and it attacked this dog every time it encroached on the cat's territory (not notable), but on this day there was a child involved (notable). Possibly it was a female cat with kittens and she was protecting her offspring.  Two of the main principles of modern ethology are Morgan's Canon and Occam's razor - I urge editors interested in animal behaviour to read these.  Whilst anthropomorphism or anthropocentrism are less frowned upon these days, it should still be used in moderation. DrChrissy (talk) 21:51, 18 July 2016 (UTC)

SAS snipers training to shoot the engine blocks of speeding trucks?
Just been talking to my father about this story in the paper today concerning SAS snipers training to stop a potential terrorist truck attack in the UK, similar to the Nice atrocity.

What manner of weapon/ammunition would they use for this, do you think? The Barret M82 firing tungsten-tipped rounds? I know there's a lot of myths about 'shooting through the engine block' (I know that a .44 magnum pistol can't actually do this, despite the pop culture thing). --146.90.107.28 (talk) 23:40, 17 July 2016 (UTC)


 * I have not been able to find any military sources detailing what they expect their .50 armor piercing rounds to actual do, and what soldiers are trained to do. But you can easily find a ton of videos on youtube of people shooting engine blocks with .50 rounds of various types to see what happens. One video does show a running truck engine stop after being hit by a .50 armor piercing round . Someguy1221 (talk) 01:05, 18 July 2016 (UTC)


 * It's worth noting that the Daily Hate story is, for the most part, confected bullshit, even down to their reuse of a 2013 photo of a sniper completely unrelated to the SAS. --Tagishsimon (talk) 01:11, 18 July 2016 (UTC)
 * And WHICH parts of the story, exactly, ARE fabricated??? 2601:646:8E01:7E0B:258A:F94:7EFA:6739 (talk) 02:01, 18 July 2016 (UTC)
 * As poor as The Daily Mail normally is, I would be reluctant to blame them for the general tone of the story. The explicitly quote the (IMO) better Sunday Times as the originators of the story including quoting people quoted in The Sunday Times. And while I can't read the whole story, the gist of the Daily Mail story appears to be supported by the part I did read on the Sunday Times. Actually if you read the Daily Mail story carefully, other than the second paragraph, there seems to be almost no original reporting by the Daily Mail of particular relevance. Any relevant parts seem to come from the Sunday Times and the other stuff is just fluff about the attack in Nice that doesn't relate to the claims. Not that this explains any misleading imagery, wording etc that does originate in the Daily Mail; simply that whatever alleged bullshit about what the SAS is or isn't doing and why would seem to come from the Sunday Times. It would undoubtedly be better to read the original story (except maybe not easy if you don't have a subscription), not the Daily Mail's reporting of it if you want more reliable info. Nil Einne (talk) 10:03, 18 July 2016 (UTC)
 * FWIW, I've now obtained access to the Sunday Times story and virtually the whole Daily Mail story is copied. The only parts in the Daily Mail story that I'm not seeing in the Sunday Times are:
 * "The training comes after truck terrorist Mohamed Lahouaiej Bouhlel, 31, rented a 19-tonne lorry before driving into a crowded promenade - killing at least 84 people, including 10 children. French police have arrested two more people, a man and a woman, in connection with the horrific incident - bringing the total number of those held to six after his estranged wife was released. ...... It comes as the French health minister confirmed that 85 people are still in hospital following the attack, with 18 - including one child - in a life-threatening condition."


 * And perhaps the part of first sentence where the number of dead is mentioned. I'm not seeing anything else that's particularly useful in the Sunday Times article of relevance to this discussion. Notably it's not clear to me that anyone believes this skill is that likely to be call upon in the UK, in particularly in a similar circumstances. I guess there is
 * "The soldiers, part of the SAS's anti-terrorist force, have been put on "immediate notice to move" after last Thursday's atrocity on the French Riviera that killed 84 people, including 10 children."


 * But it doesn't IMO add much. Perhaps the only thing is that this further clarifies (when read together with the previous paragraph which is visible in the Sunday Times previews of the story) that it's fairly unlikely this training is new as the Daily Mail's story seem to suggest. The other thing is the Sunday Times mentions "There is no evidence yet to suggest that Lahouaiej Bouhlel, 31, was directly in contact with Isis, and he is thought to have been working as a "lone wolf" operative" which the Daily Mail neglected to.
 * Nil Einne (talk) 16:41, 20 July 2016 (UTC)


 * If you have that kind of firepower, I should think killing the driver would be the more effective way to stop a truck. StuRat (talk) 01:15, 18 July 2016 (UTC)


 * I wasn't aware that SAS had branched out into weaponry. ←Baseball Bugs What's up, Doc? carrots→ 01:44, 18 July 2016 (UTC)


 * great joke, my sides! lol! 90.63.167.63 (talk) 02:19, 18 July 2016 (UTC)


 * You'll get over it. The OP assumes everyone knows what he means by "SAS", and the SAS Institute is the only one I know anything about. ←Baseball Bugs What's up, Doc? carrots→ 12:17, 18 July 2016 (UTC)
 * If only there was somewhere on the internet you could type "SAS" into to educate yourself before spouting meaningless and unhelpful nonsense. Like, some kind of big online encyclopedia. Nah, that's just silly. 90.63.167.63 (talk) 18:08, 18 July 2016 (UTC) — 90.63.167.63 (talk) has made few or no other edits outside this topic.
 * Americans are routinely berated for assuming that other editors know what they're talking about, even when it's something that can easily be looked up. If that's the standard, I don't see why Britons should get a pass.  But yes, it would be better if everyone would accept that sometimes they're not going to know the background to every question, and be willing to spend ten seconds Googling before complaining about it. --Trovatore (talk) 18:27, 18 July 2016 (UTC)


 * I always assumed that SAS meant their "Special Armored Sheep" division. StuRat (talk) 13:29, 18 July 2016 (UTC)


 * what SAS means to me —Tamfang (talk) 06:16, 20 July 2016 (UTC)
 * Careful, or the drive-bys will take shots at you, too. ←Baseball Bugs What's up, Doc? carrots→ 10:35, 20 July 2016 (UTC)


 * The photo in the Mail link shows what looks like a AW50F snipers rifle. The kinetic energy is far higher than that from a 45 Magnum hand gun (upwards of 10,000 foot-pounds). A saboted light armor penetrator discharged from that rifle and hitting an engine block will instantly invalidated that trucks 100,000 mile warranty.--Aspro (talk) 13:09, 18 July 2016 (UTC)


 * Post script. Looking up the rifle (not literally but metaphorically on google) just found this: SAS stops Islamic State convoy with just TWO bullets as British Army troops return to Iraq Likewise, I didn't know SAS had branched out in to software – strange world. --Aspro (talk) 13:21, 18 July 2016 (UTC)
 * I should point out that the Daily Express's reputation isn't significantly higher than that of the Mail. Tevildo (talk) 19:28, 18 July 2016 (UTC)

Be aware that propaganda does not necessitate truth, merely stories. --Dweller (talk) Become old fashioned! 13:30, 18 July 2016 (UTC)


 * Perhaps the OP would like to read about anti-materiel rifles? However, even with the heightened state of security in France and in other places, most soldiers deployed for urban defense will not be carrying around such a weapon-system; in France, soldiers typically carry the distinctively-shaped FAMAS service rifle.  This rifle fires a round that would probably not penetrate a truck's engine block.  In the specific case of the recent truck attack, the responding agency was the Gendarmerie, and the first rounds fired were from handguns; national police and national Army soldiers arrived from nearby positions very promptly afterward.  Law enforcement in France is complicated, and operations sometimes involve actual deployment of the army - especially in the present state-of-emergency.
 * In the United States, I do not believe any law enforcement agencies deploy an anti-materiel rifle like the Barrett M82. There has been much concern recently about militarization of the police, but even amidst these concerns, there are some weapons that civil law enforcement simply does not bring to the proverbial gunfight.  I am not sure what standards exist in the UK; but they tend to use fewer firearms than American or French police.  I doubt anti-materiel rifles are in the standard civil police arsenal in the UK.
 * Regarding training: I'm pretty certain that the standard doctrine in American counter-truck operations is to train soldiers for aimed shots and to aim for the driver - not to aim for the engine block. A statistical review of Army combat in Viet Nam found that single, well-placed, aimed shots were more effective than un-aimed automatic fire, and therefore "aim" is a heavily-emphasized primary element of modern training.  A lot of emphasis is preventative: use of concrete blockades, for example, is a great way to keep the truck far away from the soft targets.  The American military has a lot of doctrine developed in response to trucks, because we have a bad history, e.g., the 1983 Beirut barracks bombings (in which a truck crashed through a gate); and the Oklahoma City Bombing (in which a stationary truck-bomb was allowed to get closer to the building than desired); and to the perennial threat of the VBIED encountered during the last decades of combat.  From FM 3-21, Urban Operations, there is much discussion about the threat from vehicles including trucks.  From FM 3-24, Counter-Insurgency Operations - there's no mention of shooting engine blocks.  This probably means it is an ineffective tactic - especially if your defender doesn't employ a weapon system that is specifically engineered to destroy the vehicle.
 * All this theory still won't harden every soft target, but it might help reduce fatalities if more people - civil and military defenders, as well as all the members of the crowd - learn how best to react to a terrible occurrence.
 * Nimur (talk) 14:55, 18 July 2016 (UTC)
 * Well I hope such weapons aren't for sale to 16 year olds in the US. Even if they do need them to protect themselves like the gun lobby keep saying. Anyway isn't the most effective defense against such attacks to simply park a large lorry at right angles across the approach roads to stop any traffic when there is a big celebration? Dmcq (talk) 17:22, 18 July 2016 (UTC)
 * They're for sale to 18 year olds willing to spend thousands of dollars on things with no practical purpose. Well the semiautomatic and single-shot ones. Come to think of it large trucks blocking the exits might be a crowd "crush" hazard, but no vehicles blocking the entrances is also a safety hazard so who knows which is better. A protected area much larger than the crowd would be better, but close many streets to traffic. The checkpoints could let vehicles in after vetting all, possibly at the risk of not checking hard enough and letting a terrorist through. Sagittarian Milky Way (talk) 22:14, 18 July 2016 (UTC)
 * They wouldn't block the street for people! People are smaller than lorries. You just need a passage a few feet wide at each end. Such lorries could also be used to carry equipment for any extra security that may be required like checkpoints. Dmcq (talk) 22:29, 18 July 2016 (UTC)
 * That's not how crowd "crushes" work. Sagittarian Milky Way (talk) 07:05, 19 July 2016 (UTC)
 * I don't understand what you are trying to say. They had a crush at Mecca where they have enormous crowds all stuck together in a small space and are moved along and a road was unexpectedly blocked and people went in the wrong direction - and therefore lorries should not be used to block roads against lorries careering down them. Is that your point? Well if you look at that article it was two crowds coming towards each other that caused the crush,they weren't crushed against the obstruction. Anyway I'm talking about the hundreds of events around the place where you have lots of people, summer fairs, parades, New Year celebrations, all that sort of stuff where you want good security in as straightforward and unobtrusive a manner as possible. Such lorries can be decorated and have directions on them for people coming along. Dmcq (talk) 11:10, 19 July 2016 (UTC)


 * "I do not believe any law enforcement agencies deploy an anti-materiel rifle". If only.  The NYPD has a small collection of anti-material rifles which they have proudly shown off and discussed.  Saying things like "we can stop a truck by shooting its engine" or "bring down a small plane", I think they use the guns more for public relations value than any actual utility.  Dragons flight (talk) 22:49, 18 July 2016 (UTC)
 * While researching what DF said, I found which mentions the plane story. I also found this gun owner advocacy site discussion of a reject purchase attempt (as the gun couldn't be sold to private citizens)  which mentions a few things like this  purchase in Maryland where it's mentioned
 * "The problem, Plitt explained, was that the department had few options if a terrorist tried to drive a truck bomb into a local building. County snipers - there are about a dozen - routinely carry .308-caliber rifles. The guns are powerful and accurate, but not great at stopping a runaway truck. One shot from a .50-caliber rifle, however, can take out a vehicle's engine, according to Sgt. Jim Phillips, a leader of one of the county's Quick Response Teams"


 * It was also suggested that the Marvin Heemeyer case could have been used as justification. (Admittedly I'm not certain if it would have worked although suggests it may have with sustained fire.) I guess a .50-caliber would have been safer than "AH-64 Apache attack helicopter equipped with a AGM-114 Hellfire missile or a two man fire team equipped with a FGM-148 Javelin". However I believe even a .50-caliber would be found wanting against a Shawn Nelson (plumber) style attack. There's also this case where thankfully the LAPD doesn't seem to have been successfully in killing the occupants of a Tacoma truck despite 102 rounds  although I have no idea if they did enough to stop a dedicated attacker.
 * BTW a bit more research into the NYPD and I found this older story where it was said
 * "Police snipers flying overhead could use the weapon to pierce the glass of an airliner during a hostage situation. They could destroy a concrete barrier standing in the way of a target. They could puncture the engine of a barreling 18-wheeler loaded with chemical weapons, at a distance of more than a mile."


 * One point I was thinking and perhaps the barreling is intended to touch on is that while shooting the driver may seem better solution, if the truck could go in a straight line and didn't need to weave to run over people, the driver could potentially put a brick on the accelerator (or whatever) to try and keep it going even if they are killed, so taking out the engine may be needed in some cases.
 * The likelihood the police could deploy the weapon in time and accurately hit engine from a helicopter (or whatever) or at least avoid set off the explosives or chemical weapons is another matter altogether. This sounds like the plot line of a tropey police procedural or action show. The kind where the hero runs away from the explosion as the flames lick their body and then jumps when they somehow magically know they're at a safe distance, and then gets up and talks calmly to the waiting people who were a few metres away from the outer limit of the explosion.
 * Nil Einne (talk) 23:26, 19 July 2016 (UTC)

See [ https://www.youtube.com/watch?v=EwnVF1UoNEE ]. A couple of full metal jacket 50 caliber rounds into an engine block, then (Starting at 2:10) an armor piercing incendiary round. On of the standard bullets cracked the block and badly bent a piston rod, but the armor piercing bullet went through multiple layers of metal, filling one of the cylinders with chunks of cast iron. --Guy Macon (talk) 22:57, 18 July 2016 (UTC)
 * That's very encouraging. Would they be powerful enough to stop a driver reaching for their driver's license? Thincat (talk) 07:18, 19 July 2016 (UTC)
 * Just to be safe, better to use an RPG. Dragons flight (talk) 07:42, 19 July 2016 (UTC)


 * More about the AW50F (L121A1), which "Royal Marines Maritime Sniper teams use... in the counter-smuggling role, where it's used to shoot and disable the engines on smugglers' speed boats". Alansplodge (talk) 15:42, 19 July 2016 (UTC)


 * All I can say is that if all those people who were run over with a large truck in Nice, France had each had a large truck of their own, there would have been a completely different result. Some say that this demonstrates the need for common sense lorry control, but I say that if you outlaw lorries then only outlaws will have lorries. They can take my lorry when they pry my cold, dead hands from the steering wheel. (Maybe I should have taken all of those drugs after editing Wikipedia...) --Guy Macon (talk) 20:32, 19 July 2016 (UTC)
 * Be leery of the lorry. ←Baseball Bugs What's up, Doc? carrots→ 21:45, 19 July 2016 (UTC)
 * Lucky for you lagomorph, I'm a lover of lorry lore. Shock Brigade Harvester Boris (talk) 23:57, 19 July 2016 (UTC)
 * Tour a lore o' lorry... that's an Irish lullaby (slightly twisted). ←Baseball Bugs What's up, Doc? carrots→ 01:42, 20 July 2016 (UTC)


 * Is there an actual Wikipedia article about whatever this "SAS" is supposed to refer to? ←Baseball Bugs What's up, Doc? carrots→ 10:38, 20 July 2016 (UTC)


 * Enter "SAS" in Google - it's the second hit.--Phil Holmes (talk) 11:38, 20 July 2016 (UTC)
 * In Britain, SAS stands for the Special Air Service. It is a world-famous military unit that has historically been deployed for special security and military missions, perhaps most notably the Iranian Embassy siege in London in 1980.  The modern unit has similar capabilities and cultural connotations of, say, the United States Navy SEALs or the original Commandos, although there isn't an exactly equivalent counterpart in the USA.
 * To be honest, it strains my ability to assume this misunderstanding is attributable purely to your naïveté, User:Baseball Bugs - especially when you have access to free information via the internet. In almost all parts of the English-speaking world, the acronym "SAS" is widely-known; and in this context, it ought to be self-evident to a well-informed American reader that the acronym SAS refers to this organization..., much the same as we do not usually need to spell out the United States Federal Bureau of Investigation every time somebody mentions the FBI.  I'm fairly certain that our British and other English-speaking readers world-wide recognize these acronyms.
 * Nimur (talk) 12:24, 20 July 2016 (UTC)
 * Thank you for finally providing a link. And I never heard of it until the OP asked the question. And furthermore, if someone asked me what FBI stands for, I would link to it rather than kvetching about it. ←Baseball Bugs What's up, Doc? carrots→ 12:58, 20 July 2016 (UTC)
 * Indeed. When I see "SAS" I assume it's the folks who cancelled my most recent flight. Note SAS is a disambiguation page, suggesting there's no meaning that dominates. As Walter Shakespeare put it, "much ado about nothing." Shock Brigade Harvester Boris (talk) 13:10, 20 July 2016 (UTC)
 * I thought of the SAS as notable mostly for the shoot-to-kill policy in Northern Ireland, though what used to be a noteworthy atrocity is now an international standard of behavior. Wnt (talk) 15:52, 20 July 2016 (UTC)
 * Maybe they called themselves SAS so as to distinguish themselves from the SS. ←Baseball Bugs What's up, Doc? carrots→ 16:00, 20 July 2016 (UTC)


 * Seriously, though, different people are familiar with different things. Before reading this thread, I only knew about SAS (software), SAS language, Secure Attention Sequence, Serial attached SCSI, Synthetic aperture sonar, and Stability Augmentation System. I had never heard the term used to refer to any sort of military or police organization. --Guy Macon (talk) 16:19, 20 July 2016 (UTC)
 * It's worth watching them in action on this 1980 news footage if you're not familiar with what they do. Alansplodge (talk) 19:20, 20 July 2016 (UTC)