Wikipedia:Reference desk/Archives/Science/2018 November 27

= November 27 =

What are the properties of an ion engine exhaust? Is it warm? Is the engine loud? What would happen to stuff that gets in the way of the exhaust?
What are the properties of an ion engine exhaust? Is it warm? Is the engine loud? What would happen to stuff that gets in the way of the exhaust? 95.31.245.50 (talk) 02:15, 27 November 2018 (UTC)
 * see Ion thruster. The exhaust is hot as it travels at over 20km/s. They cannot work in air, it looks like the air pressure is greater than that of the plasma coming out and so nothing would come out in air. For other solid things in exhaust's way, you could expect that it could get bathed in a stream of xenon ions, so it could get charged and heated. The energy of the ions is not that high, so that the effects could not be like that of radiation, and the xenon should not become embedded in the obstacle. Since there is no air, you would not hear the ion engine. And the exhaust should be quite smooth, so there should not be much noise on the vehicle either. See also https://www.youtube.com/watch?v=xHnJeDDF06M for imagined noise. Graeme Bartlett (talk) 06:25, 27 November 2018 (UTC)
 * Except see Ionocraft and one traveled under its own power 600 meters only very recently at MIT. Dmcq (talk) 09:18, 27 November 2018 (UTC)


 * Another Reddit copyvio.  Dbfirs  19:09, 28 November 2018 (UTC)

== Why are all the planets of the Solar System revolving on the same horizontal axis but not necessarily every objet of the Solar System. Why arent all the celestial bodies of the universe on the same plane? ==

Why are all the planets of the Solar System revolving on the same horizontal axis but not necessarily every objet of the Solar System. Why arent all the celestial bodies of the universe on the same plane? 31.202.17.35 (talk) 04:14, 27 November 2018 (UTC)
 * Another copyvio from Reddit complete with spelling mistake. Who is the joker?   Db<i style="color: #4fc;">f</i><i style="color: #6f6;">i</i><i style="color: #4e4;">r</i><i style="color: #4a4">s</i>  18:54, 28 November 2018 (UTC)
 * We can turn the question around and ask why should any of them be in the same plane. Anything other than a random relationship suggests there is some fundamental relationship to either their ongoing motion or their initial formation. Our Orbital inclination article discusses some ideas relating to the distances of the bodies from each other and whether they were formed from accretion disks vs ejected from existing bodies vs some other mechanism. DMacks (talk) 05:09, 27 November 2018 (UTC)
 * This reminds me of how fond I was of the years when Pluto was a planet. MarnetteD&#124;Talk 05:31, 27 November 2018 (UTC)
 * It still is a planet, dammit! Just those "scientists" with their "data" and "logic" and other no-longer-fashionable bullshit haven't re-realized it. DMacks (talk) 06:06, 27 November 2018 (UTC)
 * Less a case of "scientists" with their "data" and "logic" and more a case of a bunch of splitters focusing too much on the differences and not enough on the similarities, IMO Iapetus (talk) 09:54, 27 November 2018 (UTC)
 * The reason why all the planets in the Solar System orbit in the same plane—the ecliptic plane—is believed to be because they all formed from the same protoplanetary disk. Because of how physics works in three spatial dimensions, a gas cloud that gravitationally collapses with nothing to stop it will start rotating and flatten out, just like spinning pizza dough. Smaller objects in the Solar System that have wonky orbits are believed to have gotten that way as a result of gravitational perturbations from other objects, and/or collisions. In fact, it's increasingly thought that all the planets formed in different orbits from where they are now. Jupiter and Saturn gradually migrated, going through the early Solar System like a wrecking crew and flinging lots of objects into crazy orbits, onto collision courses with other objects, or ejecting them from the Solar System altogether.
 * Other star systems don't rotate on the same axis because they formed differently. The formation of star systems is chaotic, shaped by whatever triggered a system's formation in the first place. However, "regular" galaxies like ours have their own galactic planes, within which most of the stuff in the galaxy rotates. This results from the same physics at play in star systems. Ultimately the distribution of matter in the universe is based on what we think are the random quantum fluctuations immediately after the Big Bang that then were enlarged as the universe grew exponentially in size. --47.146.63.87 (talk) 07:43, 27 November 2018 (UTC)

Could seawater be used instead of SO2 for atmospheric geoengineering global cooling proposals?
Could seawater be used instead of SO2 for atmospheric geoengineering global cooling proposals? 103.18.132.202 (talk) 05:38, 27 November 2018 (UTC)
 * See Marine cloud brightening. Proposals certainly include this, but practicality is a different issue. Graeme Bartlett (talk) 06:16, 27 November 2018 (UTC)

== Is the Darvaza gas crater (The Door to Hell) causing any major effects on the planet? Its been burning since 1971 and I never until recently even knew it existed. A natural gas field collapsed into an underground cavern located in Derweze, Turkmenistan. ==

Is the Darvaza gas crater (The Door to Hell) causing any major effects on the planet? Its been burning since 1971 and I never until recently even knew it existed. A natural gas field collapsed into an underground cavern located in Derweze, Turkmenistan. 112.78.38.178 (talk) 06:20, 27 November 2018 (UTC)
 * On a planetary scale, I doubt it does anything other than spew lots of carbon dioxide into the atmosphere and thereby contribute to global warming, though we spew out plenty more deliberately. Natural gas is pretty "clean", producing mostly just and water when burned, which is a big reason why it's become increasingly popular as a fuel. Coal seam fires will of course pump out nastier stuff. But, the planet is a big place. Any local phenomena like this aren't going to have much of an effect far away. It's taking the entirety of industrial civilization burning stuff non-stop to alter our global atmosphere (to our detriment). --47.146.63.87 (talk) 07:49, 27 November 2018 (UTC)


 * This question is copied from Reddit where there is a good answer, so why ask again here?  <i style="color: blue;">D</i><i style="color: #0cf;">b</i><i style="color: #4fc;">f</i><i style="color: #6f6;">i</i><i style="color: #4e4;">r</i><i style="color: #4a4">s</i>  19:12, 28 November 2018 (UTC)

Automated 3D Printing Market
What is the future of Automated 3D Printing Market? — Preceding unsigned comment added by Aarkstore~metawiki (talk • contribs) 08:56, 27 November 2018 (UTC)
 * By automated 3d printing I guess you mean an automated factory using 3d printers. Yes of course they have a big future, I've used one myself even and it was good. There is an article on 3D printing but really Wikipedia isn't in the business of horoscopes or forum discussions, more on just finding what is out there already about things. Just do a google on the topic and you'll get as much as you'd eve want I'm sure. Dmcq (talk) 09:28, 27 November 2018 (UTC)
 * I don't know how popular Mold-A-Rama were, but to me it seems to be a similar concept, albeit with a limited range of output. --TrogWoolley (talk) 14:51, 27 November 2018 (UTC)

Hello , Thanks for the information Dmcq. --Aarkstore~metawiki (talk) 09:43, 27 November 2018 (UTC)

The advancement of technology is leading humans in every genre. Automated 3D Printing are dominating printing exhibitions with a high sci-fi vision towards the future. The punch in the design of the printer is a knock in for a future market which fabricates objects just as plain as thin air.

The global automation in Automated 3D Printing market size is growing with the advent of several modifications happening in a wider scenario. Technology Market is striking a chore with these modifications.

Current implications say that the Automated 3D Printing market is likely to experience a positive spree in the current decade.

The hype around the Automated 3D Printing is continuing with the public being aware of additive manufacturing machine from quite a while now. The machines work (profoundly) than simply printing of papers using a switch button. A great sense of relief comes when the machines are getting apprehensive in industrial processes. They are producing complex and highly difficult shapes of metals, plastic and ceramic structures. Furthermore, there is a series of significant data preparation modules which is helping in the post-processing method to ensure the outcome of this is as it should be. Market research reports portray them to be the next driving factors in a future domain.

Technology market for no surprise is experiencing a growth in machines which can do tasks on their own. Further, the area of expansion is going ahead with automatic machines taking a leap forward. The AM manufacturers are working their way on to provide a series of developments in printing systems. Companies like 3D Systems, GE Additive subsidiary Concept Laser, Stratasys and Voodoo Manufacturing are even on the developmental spree in automating the 3D printing technology. Market research is constantly upgrading the status of this while an advent into technicality is bound to happen in coming years.

The companies are initiating technology which involves automating the printers themselves or even with the use of robotic arms. Consequently, this will help in more production aspects thereby increasing the outcome of such processes. The end result would be much more fabrications and as far as manufacturers are concerned, the speed up in production would help them in growing. Increasing revenue and cost of production is lessening with new strategies into action by innovative companies who want to implement a cost-effective strategy altogether. — Preceding unsigned comment added by Aarkstore~metawiki (talk • contribs) 09:03, 28 November 2018 (UTC)


 * The technology has not reached the point jet, that provides the qualitative omnipotence it prommised. The list of usable materials expanded just 10 years ago (from plastic only) into an impressive list https://www.3dhubs.com/3d-printing/processes/dmls-slm/ but the most problematic issue, its very limited use for mass production, has a long way to go. 3D-Printing processing simple takes way to long. Just get the best 3D-printer available and put it next to an Thixocasting or Thixomolding-machine. After 1000-2000 (superior quality ( Page 74, 75, 78, 79)) "Thixo"-Parts, your 3D-printer will maybe spits out its first product. I want to be there when you present all these machines to your boss and after 2-3h waiting for that 3D part hear you point out "...but that 3D-Printing can produce parts no other machine can."
 * So there doesnt seem much potential in real Production for 3E-Printing apart from some very special parts that cannt be constructed for a much cheaper, much faster production or prototypes and models that else would be handcrafted! --Kharon (talk) 21:54, 29 November 2018 (UTC)

If ice cubes melting doesnt make a cup of water overflow then how do ice caps melting raise sea levels?

 * Moved here from the computing reference desk

If ice cubes melting doesnt make a cup of water overflow then how do ice caps melting raise sea levels? 212.237.124.15 (talk) 00:13, 27 November 2018 (UTC)


 * Here is a good summary article from NOAA: Is sea level rising?
 * Yes, sea level is rising at an increasing rate.
 * "The two major causes of global sea level rise are thermal expansion caused by warming of the ocean (since water expands as it warms) and increased melting of land-based ice, such as glaciers and ice sheets."
 * An ice-cube in a cup of water is so tiny that we can generally ignore the effects of thermal expansion; the magnitude of that effect is significantly smaller than the effect of surface tension that keeps the water in the cup. The Earth's oceans are much larger than a cup, so, ... we can't ignore the complicated math-y parts of the science relating to thermal expansion of water.
 * There are so many other "small details" that don't matter when you have one cup, and do matter when you have 1021 cups... but to keep things simple, the answer is mostly because warm water expands; and partly because some of the ice on Earth is on land, so it isn't even floating in the ocean; and partly because changes in climate will cause lots of water to move to different places than where it is right now; and partly because the rest of Earth's climate and geography will respond in complicated ways to any changes in climate. A change of only a few fractions of a percent become very important when they effect a change on the entire planet.
 * Nimur (talk) 00:23, 27 November 2018 (UTC)


 * 1) Warm water is less dense. The difference in density of water after a 1-2°C warming is fairly tiny on the scale of 10-20 cm height of a typical glass, but on the scale of 4,000 meters which is the average ocean depth those fractions of a percent can add up to quite a lot. Secondly, we can't naively predict that the extra water volume will be distributed equally on top of water levels we have today. Temperature influences currents and tides, which are a chaotic system. "Chaotic" here means that the system behaves according to rules (of physics) and can be modeled and its behavior predicted (if we can account for all the factors and have enough computing power), but there's no guarantee that small changes in one variable won't cause catastrophic changes in the system. For example, all tidal patterns on Earth are caused by the same forces: Sun's and Moon's gravity - but due to local geography and currents tides range in height from a few centimeters in the Mediterranean to 15 meters in the Bay of Fundy.
 * , and this is a much bigger problem: Ice cubes in a cup are completely afloat. As such, the force of buoyancy acts to keep the water level roughly constant as the ice cubes melt. (Not quite constant as the temperature of the resulting water changes, causing effects described above). However, ice caps are not afloat, they're on solid ground.
 * Also remember that ice melting on solid ground causes a feedback loop: ice is white and repels most of the solar radiation it receives back into space. As it melts, it's replaced by much darker ground, which absorbs more radiation. The extra radiation absorbed contributes to heating remaining ice faster, which in turn causes the appearance of more darker, more absorbing ground, and so on until there's no more ice. After this is done, Earth's surface will on average be darker, causing a higher equilibrium temperature (in addition to the temperature increase necessary to trigger the ice melt in the first place). Also, other feedback loops will be triggered by the higher temperatures, such as e.g. the release of methane clathrates, which will aggravate the greenhouse effect and drive the temperatures even further up. 93.139.59.187 (talk) 07:35, 27 November 2018 (UTC)


 * Ice cubes frozen to the rim of a glass full of water will make the glass overflow when they melt.  <i style="color: blue;">D</i><i style="color: #0cf;">b</i><i style="color: #4fc;">f</i><i style="color: #6f6;">i</i><i style="color: #4e4;">r</i><i style="color: #4a4">s</i>  12:07, 27 November 2018 (UTC)


 * A cup of water with ice cubes in it is not overflowing in the first place. The oceans are already overflowing. They already cover portions of the continental masses (which would be the equivalent of the rim of the cup). --Khajidha (talk) 14:03, 27 November 2018 (UTC)

Fill a bucket with ice cubes (or with a big chunk of ice - it doesn't matter). Put in enough water that the ice floats. Melt the ice, and the water level doesn't change even slightly. That's how sea ice acts. Now put something in the bucket large enough to stick out above the water and pile the ice on that. Melt the ice and the water level will rise quite a bit. That's how ice caps with land underneath act.

Here are the numbers for the Antarctic ice cap: https://www.nature.com/articles/s41586-018-0179-y

Here are the numbers for the Greenland ice cap: http://polarportal.dk/en/nyheder/arkiv/nyheder/end-of-the-smb-season-summary-2017/

A non-technical overview: https://www.theguardian.com/environment/ng-interactive/2018/sep/12/greenland-antarctic-ice-sheet-sea-level-rise-science-climate

--Guy Macon (talk) 19:32, 27 November 2018 (UTC)

Is there air resistance in space?
<moved from RDL. -- Jayron <b style="color:#090">32</b> 15:09, 27 November 2018 (UTC)>

Is there air resistance in space? 109.70.189.75 (talk) 11:21, 27 November 2018 (UTC)


 * Do you keep asking such questions in the wrong place in order to be annoying? AnonMoos (talk) 11:44, 27 November 2018 (UTC)


 * I suppose one could regard this as a language question, since space is characterised by the lack of air. Who is this questioner who copies random questions from other sites?  I think we had a spate of this some time ago.   <i style="color: blue;">D</i><i style="color: #0cf;">b</i><i style="color: #4fc;">f</i><i style="color: #6f6;">i</i><i style="color: #4e4;">r</i><i style="color: #4a4">s</i>  11:57, 27 November 2018 (UTC)


 * Space is not a perfect vacuum, so yes, there will be some trivial, but non-zero, amount of resistance that the particles of matter out there provide to an object moving. It's not much, and it depends on what you mean by "space", but the average density of particles of matter in the "empty" interstellar space is still about 1,000,000 particles per m3.  Compared this to the earth's atmosphere, which has about 2.5 x 1025 particles per cubic meter (calculated from the 22.4 liters per mole of particles of a gas at standard temperature and pressure), and you see it's insignificant in comparison, but it still isn't zero.  -- Jayron <b style="color:#090">32</b> 15:20, 27 November 2018 (UTC)
 * One could say that "air" specifically refers to the Earth's atmosphere and say that there would be no "air" resistance outside said atmosphere no matter what the density of particles around the object in question. --Khajidha (talk) 17:00, 27 November 2018 (UTC)
 * There's also no "hard limit" that defines the edge of the Earth's atmosphere. One operational definition is the Kármán line, but as noted in that article "An atmosphere does not abruptly end at any given height, but becomes progressively thinner with altitude." It just gradually becomes less and less until it becomes indistinguishable from the solar system medium.  It should also be noted that the solar system is orders of magnitude more dense than interstellar space.  Still nowhere near as dense as Earth's atmosphere, but there's MUCH more stuff around our neighborhood than in deep space, according to Interplanetary medium about 10 to 100 times as dense.   -- Jayron <b style="color:#090">32</b> 17:08, 27 November 2018 (UTC)
 * To which I could reply that "air" has been used for centuries to mean "what we breathe", so that if the concentration of gases drops below the limits of unassisted respiration it is no longer "air" but is still "atmosphere". --Khajidha (talk) 17:13, 27 November 2018 (UTC)
 * I suppose you could, but to what benefit? I'm hugely in favour of pedantry on the RefDesk, but only when it's to the point of the question - this is not. Shall we say that objects above industrial areas experience no air resistance because the toxic smog renders the air unbreathable? In this context, the OP's meaning is clear. Matt Deres (talk) 17:48, 27 November 2018 (UTC)
 * See also Orbital decay. -- ToE 19:50, 27 November 2018 (UTC)