Wikipedia:Reference desk/Archives/Science/2017 April 6

= April 6 =

Extraterrestrial government and economy
Has anyone ever speculated what types of governments and economies extraterrestrials might have?Uncle dan is home (talk) 00:30, 6 April 2017 (UTC)


 * If you count sci-fiction, then definitely, lots of authors. --Hofhof (talk) 01:08, 6 April 2017 (UTC)


 * Yes in 1000s and 1000s of Science Fiction books, short stories, films and various other media. This is still one of my favorites. MarnetteD&#124;Talk 01:10, 6 April 2017 (UTC)


 * Foundation (Isaac Asimov novel) is a classic. Blooteuth (talk) 12:55, 6 April 2017 (UTC)


 * Asimov also wrote several non-fiction works speculating about alien civilizations; although these were more heavily concerned with planetary science, physics in general, and speculative engineering, there is some intermitent discussion of how the societies themselves might be organized.  S n o w  let's rap 09:06, 7 April 2017 (UTC)


 * Ursula LeGuin is a good one, e.g. The Dispossessed I think. Utopian fiction (and dystopian fiction) in general should give a lot of ideas; for example it mentions the "ecotopian" Mars Trilogy.  There are a lot of Golden Age classic short stories like With Folded Hands to look over, though this one isn't properly extraterrestrials even if off Earth.  But it's broad - I mean, even Star Wars is basically about an extraterrestrial government; it's just that most such stories don't totally qualify (even LeGuin's really) because they seem too closely modelled on something here.  The world hopes government is a unique error of Earth. Wnt (talk) 20:27, 11 April 2017 (UTC)

Could a natural breast look like fake?
In the same way that fake boobs sometimes look natural, could the contrary happen, and perfectly natural boobs look as if they were fake? Like being too round?--Dikipewia (talk) 03:06, 6 April 2017 (UTC)
 * Are you the one that asked about unwanted touching? ←Baseball Bugs What's up, Doc? carrots→ 05:39, 6 April 2017 (UTC)
 * Please refer to the page header: "We don't answer requests for opinions, predictions or debate." --47.138.161.183 (talk) 07:20, 6 April 2017 (UTC)
 * Unless there's some health issue behind it (like tumors making it look swollen, or a hormone unbalance), no. Why would they? But there are thousand different forms that a breast can have. Natural breasts will always be fuller on the bottom, contrary to implants which are basically a filled bag (or silicone or saline). --Hofhof (talk) 11:47, 6 April 2017 (UTC)


 * We definitely should upgrade our resources on fake breast detection. My suspicion is that seismology is a main discipline of relevance here, though of course a hands-on measurement of the deformation (engineering) is the gold standard.  I'm prone to suspect that when you see a very slight wave jiggle up through a breast each time a woman's foot clacks against the floor, that this is evidence of a natural breast, while interference with these waves might indicate the potential presence of a heterogeneous core.  But I'm not sure this is actually valid (never took my proposal to go asking significant numbers of women whether those boobs are real before the institutional review board) let alone whether something like fibrocystic breast changes would foul up the measurement.  (On the other side we should check whether canny implant manufacturers do effective impedance matching)  Of course, even fake breasts tend to occur with real women attached, and so this may not be a factor of overriding importance. ;) Wnt (talk) 16:31, 6 April 2017 (UTC)


 * This is getting offensive. WP:DENY. The IP had this right; we don't get into discussions predicated on opinion here--not any topic and certainly not regarding the "natural" or "fake" contours of a woman's breasts. Even giving the OP the largest possible benefit of the doubt as to sincerity of their interests (vs. trolling/juvenile attempts at titillation), this discussion still (predictably) took zero time to reach unacceptable comments.  On that topic, I would like to say--for the benefit of any contributor, but one in particular--that if you ever find yourself on the verge of writing the words "breast" and "jiggle" in the same sentence anywhere on this project, stop and take stock of where you are and what you are doing. I don't care if you are genuine about your speculation or, alternatively, how tongue-in-cheek clever you think you are being in responding as you are--stop and think about whether that particular sentence can ever be seen as useful to the building of an encyclopedia, and the kind of uncomfortable atmosphere it creates for female contributors.  Seriously, I very nearly took this to an admin, and won't hesitate next time. Just not appropriate for this project.  S n o w  let's rap 10:05, 7 April 2017 (UTC) }}

Equilibrium question - Physics
A point body in static equilibrium will remain at rest or continue moving with a constant velocity. This means net force on a point mass is zero if moving with constant velocity in space. Thus does the equilibrium status of a point mass moving with constant velocity alter if brought to rest with the help of external force? Unbalanced force(s) change the equilibrium status of a body, therefore, is the aforementioned external force on a point mass, which changes its position to stationary unbalance?2001:56A:7399:1200:7436:C9CB:D58F:2D2A (talk) 05:01, 6 April 2017 (UTC)eek


 * Yes. While the object is moving with constant velocity it is in equilibrium. While it is slowing down it is not in equilibrium, therefore there must be some net unbalanced force acting on it. Once it is at rest (which is a special case of constant velocity) then it is in equilibrium again. Gandalf61 (talk) 07:44, 6 April 2017 (UTC)


 * Yes. While the body is slowing down, Newton's 2nd Law explains that the force $F$ on the body is equal to the mass $m$ of the body multiplied by the deceleration i.e. "negative acceleration" $a$ of the body: $F = ma$. If the decelerating force is applied by contact with a second body, Newton's 3rd Law indicates another balance of forces thus: "When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body". Blooteuth (talk) 12:51, 6 April 2017 (UTC)

It's still not clear to me – if the forces are already balanced on an object moving with constant velocity then why would it require an external force to make forces balanced again. Does this mean forces were not balanced when the object was moving constant velocity? isn't aforesaid external force balancing opposing force which is in the form of constant velocity and mass? Just ask another question (may be nonsense) - would the said mass carry on again with its previous constant velocity (in the form of conserved force) from rest position If the resistive external force is removed — Preceding unsigned comment added by 2001:56A:7399:1200:504C:D5D1:AC3C:2E62 (talk) 04:47, 7 April 2017 (UTC)
 * If the forces are balanced, the object moves with constant velocity (assuming an inertial reference frame). "Constant velocity and mass" are not forces.
 * What could happen though is that as the object moves the forces change. I suspect you might be mixing up two meanings of equilibrium: "forces are at equilibrium" meaning the forces cancel each one out, and "equilibrium point" = a location where the potential energy curve as a function of position is flat. Tigraan Click here to contact me 10:55, 7 April 2017 (UTC)

At rest, forces on an object are balanced in all direction in space. An object starts moving in the direction of net greater force when an external force is applied. It is said an object attains its constant velocity when an external force is removed. Although the external force is removed but it already made the forces on object unbalanced resulting in the constant velocity of an object in the opposite direction of the weaker force on an object. However, if this is not true then IMPOV – An object would attain its rest position again instead of moving with constant velocity when an unbalanced external force is removed. Since all forces balanced again on the object when an unbalanced external force is removed therefore it can’t move in any direction, as movement requires unbalance force.

This is my personal thinking (freedom of expression), however, I appreciate all replies. Thank you all. — Preceding unsigned comment added by 2001:56A:7399:1200:A5F2:D507:5BDD:E264 (talk) 05:19, 8 April 2017 (UTC)


 * You do not seem to have understood that Newton's Laws describe a single point mass and a single external force. That force may an isolated force or it may be the resultant (or nett force) of several forces, but that makes no difference to the object. At rest the force is simply zero i.e. absent. While a force is being applied, the object accelerates. When that force is removed, the object continues moving at the velocity imparted to it, and that is the only trace of what was done. That goes on notionally forever, there is no other "memory" of "unbalanced forces", nor does its movement now require any force to maintain it. This is elementary Classical mechanics that indicates your view that "An object would attain its rest position again...when an unbalanced external force is removed" is wrong, regardless of any claimed "freedom of expression". Blooteuth (talk) 23:38, 8 April 2017 (UTC)

I have the understanding of Newton's laws of motion. Force of gravity always acts on thrown object on earth but the notion of gaining constant velocity of an object in space forever seems wrong to me, as net force on an object is zero again after removing the external force. I may be wrong but motion always requires effort. Even if the aforesaid standard notion is true then still I don’t think an object or a person can feel himself in static equilibrium if not standstill in an inertial frame of reference, however, my judgment may be incorrect. — Preceding unsigned comment added by 2001:56A:7399:1200:B1D8:65D5:373A:1222 (talk) 17:17, 10 April 2017 (UTC)
 * During just 25 seconds (the achievable zero-g period) aboard the vomit comet you might verify for yourself Newton's First Law, since apparently what you "think you can feel" overrides his physical science and anything Wikipedia can teach you. Blooteuth (talk) 15:06, 11 April 2017 (UTC)

im not "chesty as a peacock". Thank you all.

What is the difference between the cells of the electrical conduction system to the rest heart muscle cells?
According to the article here "The conduction system consists of specialised heart muscle cells, and is situated within the myocardium. There is a skeleton of fibrous tissue that surrounds the conduction system which can be seen on an ECG. Dysfunction of the conduction system can cause irregular, fast, or slow heart rhythms.". In what they unique compared to the rest muscle cells? according to other articles here the muscle cells of the heart (no differentiation) has the feature of automatically. 93.126.88.30 (talk) 06:16, 6 April 2017 (UTC)
 * The article referred is Electrical conduction system of the heart. Another article describes the heart muscle which differs from skeletal and smooth muscle. An automatic (spontaneous natural pacemaker) pulse arises from the Sinoatrial node and is conducted via Bachmann's bundle from right to left atrium. The AV node introduces a delay of about 0.12s which ensures that the atria have ejected their blood into the ventricles first before the ventricles contract; this delay is seen as the PR segment on the EEG. Blooteuth (talk) 12:34, 6 April 2017 (UTC)
 * Thank you for your comment. But I'm sorry I didn't understand the answer to my question. It's used to be said that there is electrical conduction system of the heart which conducts the electricity to the muscle, and from that I understand that these cells are not muscles by themselves they just conduct the electricity. Isn't it? 93.126.88.30 (talk) 15:03, 6 April 2017 (UTC)
 * The cells in question are Purkinje fibers. They are usually considered to be a special type of muscle cell.  Their signal-conducting role arises ultimately from the fact that, although all heart muscle cells are spontaneously rhythmic, the cells of the sino-atrial node beat a little bit faster than cells in other parts of the heart.  Consequently on each heartbeat they are the first cells to start firing.  The Purkinje fiber system conducts their activity rapidly to other parts of the heart, ensuring that each part fires as a synchronized whole at the proper time. Looie496 (talk) 15:34, 6 April 2017 (UTC)

Tetrapod Clades that Survived the K/T Boundary?
Is there any source that describes which tetrapod clades survived the KT event? For example, was there only one turtle that was the ancestor of all turtles alive today? Or are the sideneck turtles a separate branch since before the KT event? As for the birds, my understanding is that Presbyornis, a galloanser, shows that clade predated and survived Chicxulub. Thanks! μηδείς (talk) 17:43, 6 April 2017 (UTC)


 * There is a lot of information in the article Cretaceous–Paleogene extinction event - and also a lot of references. Just checking turtles it actually says "Over 80% of Cretaceous turtle species passed through the K–Pg boundary. Additionally, all six turtle families in existence at the end of the Cretaceous survived into the Paleogene and are represented by living species." Read the article for information about other groups of animals. Wymspen (talk) 18:11, 6 April 2017 (UTC)


 * Thanks, the six still-extant turtle families is exactly what I was looking for.  Thanks for the link.  I am most interested in mammals and birds.  For example, are the Afrotheres pre- or post-K? μηδείς (talk) 21:45, 6 April 2017 (UTC)


 * You just need to keep reading and follow the links. The Afrothere article includes a line saying that the oldest know fossil is Ocepeia and that article says it dates to about 60 million years ago. As the Cretaceous–Paleogene extinction event is dates at 66 million, that makes it more recent. Inevitably, you have to accept that there may be older species for which there is (as yet) no fossil record. Wymspen (talk) 22:19, 6 April 2017 (UTC)


 * These are largely unsettled questions. Geographic distributions suggest that the splits between afrotheria, xenarthra, laurasiatheria and euarchontoglires resulted from the breakup of Pangaea, which happened many millions of years before the KT event. Looie496 (talk) 01:21, 7 April 2017 (UTC)

Are longer focal distance magnifiers more expensive to manufacture?
There are worn magnifiers (in the form of loupes or similar) quite cheaply available for people to use when working with electronics or sewing or painting figurines etc but for some reason they all have a very short focal length so you have to be very close to the workpiece which is sometimes very impractical, especially with soldering. If you look at reviews there are often many complaints about this problem. There are some magnifying loupes available with focal distances of around 300-400 mm which is more practical but they're all extremely expensive. Is it more difficult to make lenses with a longer focal distance or what?
 * It would be easy to make such lenses in a simple form, but a big problem could be that the combination of their magnification and the longer distance to the objects would likely lead to (a) rather restricted fields of view and (b) the restricted image dancing around annoyingly. It might be possible to overcome this with more elaborate compound lenses, but these would be more expensive than a simple lens, and would also be heavier and more cumbersome to wear. An alternative might be to use a lens (or lens combination) held on a fixed (though adjustable) stand between the eye and the work material, rather than wearing it. I'm not sure of the term of art for such a setup, but I have seen it in use. {The poster formerly known as 87.81.230.195} 90.217.249.244 (talk) 12:29, 7 April 2017 (UTC)


 * The OP is right in part. But it is the depth of field that matters too. For fine soldering I found that OptiVisor Headband Magnifiers makes life easy. Just google.--Aspro (talk) 13:16, 7 April 2017 (UTC)


 * View: How to Choose the Right Optivisor Headband Magnifier. There are many other cheaper copies available but one gets what one pays for. The plastic becomes brittle and brakes and the adjustment clamps fail with little use, etc. --Aspro (talk) 14:09, 7 April 2017 (UTC)


 * The OptiVisor's 3.5x focal distance is only four lousy inches (12 cm). Other more expensive lenses are like 32-40 cm. Seans Potato Business 23:55, 7 April 2017 (UTC)

Is there any danger of the world running out of oil or does other energy advancements make that unlikely?
2.102.184.154 (talk) 21:50, 6 April 2017 (UTC)

Our article is Peak oil. However, since 2014 the world has an excess of oil production, due in large part to fracking in the US. This has driven the price of crude oil down from >$100/bbl to <$50/bbl. In addition, the costs of solar and wind are rapidly decreasing, which is apparently reducing oil demand. As with most commodities, we don't "run out". instead, as the cost increases, the commodity quits being used for those uses that have cheaper alternatives. In this sense, we will never run out of oil, we will just quit using it to make gasoline for cars. -Arch dude (talk) 22:05, 6 April 2017 (UTC)


 * One reason for not running out of oil is that people change the definition. Once oil was whale oil and petroleum was just a contaminant in salt wells.  Later on, shale oil wasn't really "oil".  Biodiesel isn't quite "oil" in modern speech, but it might soon become such.  Even among petroleum there are various types and grades, not all of which were all that usable in the past.  There is, of course, only a limited amount of hydrocarbon in the Earth's crust, and an even more limited tolerance of the atmosphere and ocean for absorbing CO2, but it's fair to suppose that people will try to make do; modern energy technology gives a fair range of options. Wnt (talk) 01:46, 7 April 2017 (UTC)


 * Known oil reserves have increased constantly throughout the industrial age. If hydrocarbons become scarce enough, we will mine dumps and distill CO2.  Some believe that many reserves replenish themselves over time, with oil from surrounding rocks slowly leaking in to refill deplenished reserves, but I don't have a source on hand for that. μηδείς (talk) 15:05, 7 April 2017 (UTC)
 * The definition of Oil reserves is tricky. Specifically, a "proven oil reserve" (which is what is usually meant by the term) is a reserve that is technically profitably exploitable at the current market price of oil. That is, some company has drilled and demonstrated that the oil is actually there, and that it is not too expensive to extract that oil at today's price. Recently, some large oil companies were required by US SEC rules to remove billions of dollars of "proven oil reserves" from their balance sheets. Those reserves were booked when oil was at $100/bbl in 2014, but they are not economically recoverable when oil is at $50/bbl. This goes back to the OP's question: "running out" of oil is a complicated concept. -Arch dude (talk) 17:13, 7 April 2017 (UTC)


 * Thanks, an interesting comment, and one that shows the effect of supply and demand. The pdf downloadable at the link on the left of http://www.capitalism.net/ covers this at length.  Basically, no commodities market has been cornered, unless you think of the extinction of certain organisms. μηδείς (talk) 19:49, 7 April 2017 (UTC)