Wikipedia:Reference desk/Archives/Science/2017 September 5

= September 5 =

How often are palm readings accurate
Has any research been done to investigate the accuracy of palm readings?Uncle dan is home (talk) 03:20, 5 September 2017 (UTC)
 * We fortunately have a Palmistry article with some critical sources. — Paleo  Neonate  – 03:40, 5 September 2017 (UTC)
 * Read Palmistry for a clue. ←Baseball Bugs What's up, Doc? carrots→ 03:41, 5 September 2017 (UTC)
 * A possible scientific way to investigate it would be to start by asking the question: "What is the probability of a palm reading being accurate based solely on random chance?. 38.88.99.222 (talk) 08:16, 5 September 2017 (UTC)
 * That's not entirely the right question though. Palm readers, like most in-person psychics, can potentially read subtle clues from the responses, body language, and appearance of the people they are giving the reading for.  Such signals may guide them to making statements that are more likely to be true about the person receiving the reading than they might be about a random person.  For example, if the palm reader predicts you are going to meet a certain kind of man/woman in the near future, they might be guessing (in part) based on the kind of man/woman they think a person like you would be most likely to meet.  Dragons flight (talk) 10:58, 5 September 2017 (UTC)
 * BTW we have an article on that kind of things: the term is cold reading. Tigraan Click here to contact me 11:09, 5 September 2017 (UTC)
 * For the skilled con artist, there's a pretty good probability that their cold readings will turn out to be pretty accurate. Therein may lie the real answer to the OP's question. ←Baseball Bugs What's up, Doc? carrots→ 00:48, 6 September 2017 (UTC)


 * Mandatory link when discussing "accuracy" of such things: Barnum effect. Tigraan Click here to contact me 11:09, 5 September 2017 (UTC)

Mechanism of global warming causing extreme weather
Has the mechanism for how global warming causes recent increase of frequency of extreme weather events been shown? If yes, it would be more than a correlation and, in my view, much fewer people would be turned away from the concept of climate change. VarunSoon (talk) 06:57, 5 September 2017 (UTC)


 * Here is the science:


 * Thunderstorms and Tornados:


 * "There’s uncertainty in the findings because of the meager scientific attention thunderstorms have received. Unlike tropical cyclones, which climate researchers have studied intensely since Hurricane Katrina struck New Orleans in 2005, only a handful of researchers have focused on the impact of global warming on severe thunderstorms. Then there are problems unique to tornadoes. Beyond knowing that they require a certain type of wind shear, meteorologists just don’t know much about why some thunderstorms generate tornadoes and others don’t. (Only about 1 percent of thunderstorms generate tornadoes.) You can’t just take the results of the modeling for severe thunderstorms and assume they apply to tornadoes." --Source: NASA Earth Observatory


 * Tropical Cyclones (Hurricanes, Typhoons, Tropical Storms):


 * "The most recent draft of a sweeping climate science report pulled together by 13 federal agencies as part of the National Climate Assessment suggested that the science linking hurricanes to climate change was still emerging. Looking back through the history of storms, 'the trend signal has not yet had time to rise above the background variability of natural processes,' the report states." --Source: The New York Times.


 * "According to the United States Environmental Protection Agency, "The total number of hurricanes and the number reaching the United States do not indicate a clear overall trend since 1878" and "changes in observation methods over time make it difficult to know whether tropical storm activity has actually shown an increase over time." --Source: United States Environmental Protection Agency.


 * "Detection and attribution of past changes in tropical cyclone (TC) behavior remaim a challenge ... there is still low confidence that any reported long-term (multidecadal to centennial) increases in TC are robust... This is not meant to imply that no such increases in TC activity have occurred, but rather that the data are not of a high enough quality to determine this with much confidence. Furthermore, it has been argued that within the period of highest data quality (since around 1980) the globally observed changes in the environment would not necessarily support a detectable trend of tropical cyclone intensity (Kossin et al. 2013). That is, the trend signal has not had time to rise above the background variability of natural processes." --Source: Draft National Climate Assessment (section 9.2).[the Draft National Climate Assessment


 * "Observed regional climate variability comprises a number of factors, both natural and anthropogenic, and the response of tropical cyclones to each factor is not yet well understood. Long-term trends in tropical climate due to increasing greenhouse gas can be regionally dominated by shorter-term decadal variability forced by both internal and external factors such as changes in natural and anthropogenic aerosol concentrations ... In concert with these natural and anthropogenic external forcings, internal variability can play a substantial, and possibly dominant, role in regional decadal variability. Thus, when interpreting the global and regional changes in tropical cyclone intensity shown in the present work, it is clear that framing the changes only in terms of linear trends forced by increasing well-mixed greenhouse gasses is most likely not adequate to provide a complete picture of the potential anthropogenic contributions to the observed changes." --Source: NOAA/National Climatic Data Center,   Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin–Madison.


 * "It is premature to conclude that human activities -- and particularly greenhouse gas emissions that cause global warming–have already had a detectable impact on Atlantic hurricane or global tropical cyclone activity. That said, human activities may have already caused changes that are not yet detectable due to the small magnitude of the changes or observational limitations, or are not yet confidently modeled (e.g., aerosol effects on regional climate)." --Source: National Oceanic and Atmospheric Administration, Geophysical Fluid Dynamics Laboratory


 * "The term climate change detection as used in this abstract refers to a change which is anthropogenic in origin and is sufficiently large that the signal clearly rises above the background “noise” of natural climate variability (with the “noise” produced by internal climate variability, volcanic forcing, solar variability, and other natural forcings). As noted in IPCC AR42, the rise of global mean temperatures over the past half century is an example of a detectable climate change; in that case IPCC concluded that most the change was very likely attributable to human-caused increases in greenhouse gas concentrations in the atmosphere.


 * In the case of tropical cyclones, the WMO team concluded that it was uncertain whether any changes in past tropical cyclone activity have exceeded the levels due to natural climate variability. While some long (century scale) records of both Atlantic hurricane and tropical storm counts show significant rising trends, further studies have pointed to potential problems (e.g., likely missing storms) in these data sets due to the limited density of ship traffic in the pre-satellite era.  After adjusting for such changes in observing capabilities for non-landfalling storms, one study found that the rising trend in tropical storm counts was no longer statistically significant.  Another study noted that almost the entire trend in tropical storm counts was due to a trend in short-duration (less than two days) storms, a feature of the data which those authors interpreted as likely due in large part to changes in observing capabilities.


 * A global analysis of tropical cyclone intensity trends over 1981-2006 found increases in the intensities of the strongest tropical cyclones, with the most significant changes in the Atlantic basin. However, the short time period of this dataset, together with the lack of 'Control run' estimates of internal climate variability of TC intensities, precludes a climate change detection at this point." --Source: Article in Nature Geoscience


 * "A satisfactory answer to the question of what sets the annual global rate of tropical cyclone formation, roughly 80 per year, has thus far evaded climate scientists. Several empirical relationships have been derived to relate tropical cyclone formation to large-scale climate variables, such as genesis potential indices, but there is to date no established theory relating tropical cyclone formation rate to climate." -Source: Oxford Research Encyclopedia of Natural Hazard Science


 * The above is peer-reviewed academic science by actual climatologists. If you look at the popular press, you will find many sources that claim that there is a connection. Some even quote the minority of climatologists who do not agree with the scientific consensus. --Guy Macon (talk) 07:33, 5 September 2017 (UTC)
 * The views aren't that uniform, there even might be research bias. For instance, the Intergovernmental Panel on Climate Change stated that "A changing climate leads to changes in the frequency, intensity, spatial extent, duration and timing of extreme weather and climate events, and can result in unprecedented extreme weather and climate events". And this study found that "historical global warming has increased the severity and probability of the hottest monthly and daily events at more than 80% of the observed area and has increased the probability of the driest and wettest events at approximately half of the observed area". All in all, one can't cancel physics: a warmer climate, in particular, leads to more evaporation which in turn proved to be hazardous. Brandmeistertalk  11:01, 5 September 2017 (UTC)
 * It's not really important to see if you can prove to 95% statistical significance whether extreme weather events are extremer now. Do you really want to get to the point where it's nearly certain man is causing worse weather and we're still mostly using fossil fuels? Then it'll take decades to stop, decades for the temperature to stop rising after that and decades for the glaciers to stop glacially flowing to the sea faster than they're replaced after that. Computer models are already predicting 1 or 2° Celsius of rising no matter how fast we stop (realistically, it can't happen in a year or a day) and 2 is supposed to already cause problems. Now Guy Macon, is it already 95% statistically significant that the geologically lighting fast 46% increase in CO2 which had not happened in most of the Holocene is caused by man? Even if somehow not and even if climate really is less predictable than the 3,650-day weather forecast (it's not) then I'd like to see the CO2 stay at the 280 where it hasn't caused problems for civilization for the last 10,000 years instead of the unprecedented* double, triple or whatever the denialists want it to be. *yes, yes it was 400 ppm as little as 3 million years ago but sea level was 15-25 meters higher and the effects of that climate would cause a lot of other problems. Sagittarian Milky Way (talk) 16:07, 5 September 2017 (UTC)
 * Guy Macon is not just cherry picking data points to support his pre-determined conclusion that climate change isn't happening, he's even ignoring statements from the self-same sources that inconveniently don't support his thesis. See here already cited above, which states "Anthropogenic warming by the end of the 21st century will likely cause tropical cyclones globally to be more intense on average (by 2 to 11% according to model projections for an IPCC A1B scenario). This change would imply an even larger percentage increase in the destructive potential per storm, assuming no reduction in storm size."  Consensus is that, while data on existing extreme weather events is too sparse to make determinations on any one storm is due to climate change, models are also in general agreement that we are likely to see increases.  One atom of iron will not crush you, but an anvil will, and it makes no sense to debate which of the iron atoms did or not not break your bones.  In the same way, while any one storm or weather event cannot be said to be caused by climate change, the patterns are expected, based on the models, to show increased activity and intensity.  Merely because the anvil has not yet landed on our heads for us to asses the damage to our bones, doesn't mean we can't see it falling towards us.  -- Jayron 32 20:01, 5 September 2017 (UTC)


 * Not cherry picking at all. I am talking about actual peer-reviewed scientific evidence for or against climate change having an effect on the frequency or intensity of current tropical cyclones. (the reader should remember that the scientific consensus on this is "we don't know, not enough data to tell", not "there is no connection"). You are talking about predictions based upon computer models that in the future climate change will have an effect on the frequency or intensity of current tropical cyclones. Nobody disputes that. Nor is there any good reason to think that the predictions are wrong.


 * You are also a liar. You stated "...to support his pre-determined conclusion that climate change isn't happening". I have always been quite clear that the overwhelming scientific consensus is that AGW is happening, and that what little scientific opposition there is is a fringe view. And no, I am not interested in any accusations that I am being uncivil. WP:NPA does not require me to stay silent when someone is deliberately lying about me. Don't like it? Report it a WP:ANI. Clogging this thread with complaints about this will just waste everyone's time, because I plan on ignoring them. --Guy Macon (talk) 06:35, 6 September 2017 (UTC) (Stricken because it was a misunderstanding. Both sides have apologized). --Guy Macon (talk) 13:30, 7 September 2017 (UTC)


 * Why would I go to ANI? Also, thank you for clarifying your position on the matter.  It was unclear based on the tenor of your post what your position was, and I unequivocally apologize for calling you out incorrectly.  It was wrong of me, and I have no defense for it.  My sincerest apologies to you for what I did.  -- Jayron 32 11:12, 6 September 2017 (UTC)


 * Thanks. And I apologize for losing my cool above. Sorry about that. This is an area where one keeps running into two kinds of POV pushing editors. First there is the "global warming is a myth" crowd (often conservative Republicans). Then there is the "Every bad thing is always a direct result of global warming and anyone who says different is anti-science" crowd (often liberal Democrats). I have been accused of being in the latter group when I have pointed out the peer-reviewed science that clearly proves that the climate is changing and assigns a high probability that humans are a major cause. I have been accused of being the former when I pointed out that peer-reviewed science does not support global warning as a major cause of wildfires being so large and destructive lately -- that's mostly the fault of Smokey The Bear (decades of fire suppression helped create forests unnaturally thick with fuel, setting the stage for the infernos that march across the West every year) and to a smaller extent, how many arsonists and idiots throwing away lit cigarettes we have in any particular year. I just want Wikipedia to reflect the peer-reviewed science in places where it now reflects what is found in "popular science" type magazines and websites or worse, blatantly political websites. --Guy Macon (talk) 13:30, 7 September 2017 (UTC)


 * A simple dumbed down explanation is that evaporation rates are higher at higher temperatures, but the atmosphere can hold more water at higher temperatures leading to more droughts. Now, what goes up must come down, so you'll get more rainfall despite longer drought periods, so that larger rainfall amount is going to be squeezed into smaller time periods. Besides such effects we need to keep in mind is that the mere fact that we're adapted to some state of the climate, a rapid transition to another state of the climate will always have extreme consequences for us. You cannot easily move large cities to better locations, you cannot easily redraw the borders of countries to redistribute fertile lands fairly. If climate skeptics say that a warmer climate is better because of more fertile lands, then even if they were correct about that (which is doubtful), it's not going to work out well for us, because we don't have a World government. Count Iblis (talk) 20:27, 5 September 2017 (UTC)


 * WP:OR. Yes, higher ocean temperatures do increase the frequency or intensity of current tropical cyclones. Do you have any peer-reviewed sources that say that AGW is the only or even the main determinant of ocean temperatures in the Gulf in the short term? You might want to read Enfield, David B.; Mayer, Dennis A. (1997). "Tropical Atlantic sea surface temperature variability and its relation to El Niño–Southern Oscillation". Journal of Geophysical Research. 102 (C1): 929–945. if you think that is the case. Of course that paper talks about variation that lasts a few years at most, and in no way invalidates the longer-term effect of AGW which has an effect lasting from for decades to centuries.
 * Likewise, it is trivially obvious that any sea level rise will make any flooding at the affected coast worse, including storm surge from tropical cyclones. But again, we are looking at a long-term global trend caused by AGW overlaid on local shorter-term sea level changes. Our article at Sea level rise says "Many ports, urban conglomerations, and agricultural regions are built on river deltas, where subsidence of land contributes to a substantial increase in effective sea level rise. This is caused by both unsustainable extraction of groundwater (in some place also by extraction of oil and gas), and by levees and other flood management practices that prevent accumulation of sediments to compensate for the natural settling of deltaic soils... This results in subsidence [of] over 3 meters in urban areas of the Mississippi River Delta." Again, this is local and temporary, and in no way invalidates the longer-term sea level rise caused by AGW. --Guy Macon (talk) 06:35, 6 September 2017 (UTC)


 * Sagittarian Milky Way (talk) 20:51, 5 September 2017 (UTC)


 * Indeed! Count Iblis (talk) 01:33, 6 September 2017 (UTC)


 * Indeed you are once again confusing predictions of a future effect with peer-reviewed science showing that we do not (so far) have enough data to show a current effect. --Guy Macon (talk) 06:35, 6 September 2017 (UTC)
 * It's not that 'there isn't (yet) enough data', it's that it isn't in principle possible, because Climate is not Weather, but rather the the long term average of weather – typically over a 30-year period. Also, weather itself is at root a chaotic system, so is not very amenable to definitive analysis of the 'cause' of a single weather event. {The poster formerly known as 87.81.230.195} 2.121.160.76 (talk) 08:26, 6 September 2017 (UTC)


 * You are completely correct about the the 'cause' of a single weather event. Did we have a lot of global warming in 2005, when we saw four cat5 Atlantic hurricanes, but less global warming from 2008 to 2015, when we had none? This does not imply that we will never be able to establish a connection though. That's not what the peer-reviewed science says. It says things like "the trend signal has not yet had time to rise above the background variability of natural processes", "The total number of hurricanes and the number reaching the United States do not indicate a clear overall trend since 1878", and "It is premature to conclude that human activities -- and particularly greenhouse gas emissions that cause global warming–have already had a detectable impact on Atlantic hurricane or global tropical cyclone activity. That said, human activities may have already caused changes that are not yet detectable." That last point is important. Just because we cannot prove it because of limited data, that doesn't imply that it isn't happening.


 * And just because the science says that we don't have enough data to answer this question (and it does: those who keep disagreeing cannot point to any peer-reviewed science that supports their claims -- they keep confusing future predictions with current evidence) that in no way implies that we will never have enough data. The first successful weather satellite was TIROS-1 in 1960, which operated for 78 days. We didn't have full time coverage until Nimbus 3 in 1969. Since we started having satellite coverage, there have been nineteen cat5 Atlantic hurricanes; Camille (1969), Edith (1971), Anita (1977), David (1979), Allen (1980), Gilbert (1988), Hugo (1989), Andrew (1992), Mitch (1998), Isabel (2003), Ivan (2004), Emily (2005), Katrina (2005), Rita (2005), Wilma (2005), Dean (2007), Felix (2007), Matthew (2016) and Irma (2017). (Harvey was cat4). That simply is not enough hurricanes to prove or disprove a connection with AGW. There are lots of things we can prove about climate change. This isn't one of them. --Guy Macon (talk) 11:20, 6 September 2017 (UTC)
 * Hey and TPFKA, you may not have heard of new breakthroughs in attributional methods. This is subtle and difficult stuff, but we can sometimes attribute cause to weather events. For pop-sci coverage, see Scientific American article here . For serious science, see scholarly review article Attribution of extreme weather and climate-related events here . From climate.gov (for now at least), see here . For a whole book from the national academies, see here . Additional coverage here.
 * TL;DR: yes, we can sometimes attribute certain extreme weather events to climate change with high degrees of certainty. It's hard to do, it's hard to understand, but experts can do it. SemanticMantis (talk) 15:16, 6 September 2017 (UTC)
 * What a refreshing change! Someone is talking about the actual science, and brings up some new information that I was not familiar with. So much better than confusing evidence with predictions and saying thing about me that are provably untrue...
 * I am going to study that article in depth, but at first glance it looks like it is in agreement with established science, with the twist of discussing some new methods and information that the peer-reviewed sources I quoted above predate. Good stuff. In particular I found the graph at https://www.climate.gov/sites/default/files/Chart6_620.png to reflect what I am seeing in the peer-reviewed science. --Guy Macon (talk) 18:20, 6 September 2017 (UTC)
 * I was wrong. It was inexcusable.  I apologize for that.  -- Jayron 32 18:22, 6 September 2017 (UTC)

Liquid gas containers
Since Leidenfrost effect is finite, why liquid gas containers (such as for liquid nitrogen or oxygen) do not eventually freeze themselves and become brittle too, when in use? Thanks.--212.180.235.46 (talk) 10:37, 5 September 2017 (UTC)
 * Sometimes they do. One reason why you only put cryogenic fluids in vessels made of something suitable for that temperature. Generally such a vessel, like a Dewar, is made of metals in a grade chosen so that it doesn't become brittle when cold. Particularly with plastics, it's hard to find such materials. Andy Dingley (talk) 10:45, 5 September 2017 (UTC)


 * See Cryogenic storage dewar. -- Jayron 32 12:01, 5 September 2017 (UTC)
 * Not all lab benchwork is done with a Dewar. Plenty uses a cheap wide-mouthed vessel, often of foamed plastic. It's rare now, but in past years it wasn't an uncommon lab accident for someone to use a dry ice capable vessel, put liquid nitrogen in it, then have it smash from a trivial impact.
 * Dewars are (inherently) complicated, so are expensive and made with some degree of care. They rarely break. Andy Dingley (talk) 12:10, 5 September 2017 (UTC)
 * It depends on whether the OP is talking about long-term storage or using it. You've got to keep your liquid nitrogen in something when you aren't using it!  It isn't stored in Styrofoam containers, even if such containers are commonly used on the bench.  -- Jayron 32 12:16, 5 September 2017 (UTC)

== Feynman Lectures. Exercises. Exercise 12-12. Lecture 12. 2 Archive==

The 9.8 m/s^2 force per mass downward does not exist in an inertial frame of reference. -- I have never heard that some forces disappear in the inertial system. I did not find this in the article https://en.wikipedia.org/wiki/Inertial_frame_of_reference. According to the other exercises for lecture 12 to solve ex. you should count all forces, including weight. Can you give a link to the source? Username160611000000 (talk) 16:41, 5 September 2017 (UTC)


 * See our article on Fictitious force. Which I'll quote " Gravitational force would also be a fictitious force based upon a field model in which particles distort spacetime due to their mass." It happens to be the odd one because of GR. --Modocc (talk) 17:00, 5 September 2017 (UTC)


 * General Relativity is not a subject of lecture 12 and even first 50 lectures. So we consider a table (which is actually not an ideal inertial frame as it rotates with Earth, but we suppose that the caused effects are negligibly small) in Newtonian space. Let the sum of forces acting on the table be zero. Then a body sliding on the table also has the sum of forces along the Z axis equal zero. Username160611000000 (talk) 17:39, 5 September 2017 (UTC)


 * The effects of spacetime warping with GR are not negligibly small and GR is integral with the Standard Model. The table is classically in static equilibrium. The object however is not for it will slide down the wedge without the additional acceleration continuing to overcome it. --Modocc (talk) 18:12, 5 September 2017 (UTC)


 * Reading further we meet Fig. 14–1, in which Feynman shows all the forces in lab (inertial) system. Why didn't Feynman mention general theory of relativity ? Username160611000000 (talk) 13:19, 6 September 2017 (UTC)

Biology questions.
1. What are examples of foods we don't digest? 2 answers I have are cellulose, and D-amino acids.

2. Do vegetarians have different urines than non-vegetarians? My take is, they don't eat meat but they still digest the same amino acids, so perhaps it is not possible to tell the difference in urine?

3. Who kills bacteria/viruses better, acids or bases? Do acids or bases kill more bacteria/viruses?

4. What is the fate of dead bacteria? Do they just break up into proteins and carbohydrates? I was told it is safe to drink a cup of water filled with dead bacteria.

Thanks. 12.239.13.143 (talk) 21:56, 5 September 2017 (UTC).


 * For #2, given that they have far fewer kidney stones, I think it likely that you could tell a vegetarian by testing for lower levels of purines in the urine.


 * For #4, dead bacteria are better for you than live in that they won't grow more bacteria inside of you, but they are not automatically safe to eat. There are many cases of death by eating food where Clostridium botulinum once grew but was later killed. The Neurotoxin remains long after the bacteria die off.


 * -Guy Macon (talk) 23:25, 5 September 2017 (UTC)


 * For #1, "Dietary fiber or roughage is the indigestible portion of food derived from plants".--Shantavira|feed me 08:18, 6 September 2017 (UTC)


 * For #3, I would say acids generally are more effective against microbes, and even a fairly weak acid, a 5% solution of acetic acid, is quite effective. While anti-microbial alkalis generally need to be pretty strong to be effective. It's the reason why yogurts don't get overrun by bacteria, because the weak lactic acid kills them. You can find more information at Disinfectant and http://www.cfsph.iastate.edu/Disinfection/Assets/Disinfection101.pdf .  --Jules  (Mrjulesd) 21:03, 6 September 2017 (UTC)
 * Regarding #4, every cup of water you've ever drunk had live bacteria in it. Bacteria are everywhere. You're covered in them. This planet belongs to them; we're all just guests. Also note that virtually all bacteria are harmless to humans with functional immune systems; it's the remaining tiny percentage that cause problems if they get to you somehow. Anyway, dead bacteria get decomposed like every other dead organism. The cells will break apart over time, and their biomolecules will degrade, but usually they'll be food for something else first. If you drink bacteria, live or dead, you'll digest them, just like all the other food you eat. Well, sometimes some of them can survive, and then they might go on to join your gut biota. If they're "good" bacteria, like those found in probiotic foods, great! If they're bad hombres like certain E. coli strains, uh-oh. --47.138.161.183 (talk) 09:26, 7 September 2017 (UTC)

white dwarf striking neutron star at high speed
It seems theoretically possible for a white dwarf to strike a neutron star at 90% of the speed of light. Could that cause the neutron star to break up?144.35.45.46 (talk) 23:09, 5 September 2017 (UTC)


 * In general, collisions at low enough speeds behave in the usual way where you can model the objects as rigid objects, while at sufficiently high speeds, the collision between solid objects must be treated as if the objects are liquids. The transition point between the two scenarios is roughly the speed of sound. The speed of sound in a neutron star is $$\frac{c}{\sqrt{3}}$$, so the collision region has to be treated as a liquid or a gas, not a solid. But the matter from the collision is not going to escape the gravity of the combined system anyway and the dissipation of energy from the collision may make the white dwarf to become bound to the neutron star, so the two objects will end up merging into a larger neutron star or it may undergo gravitational collapse and become a black hole. Count Iblis (talk) 00:14, 6 September 2017 (UTC)


 * How sure of that are you? A white dwarf at the ridiculous speed of 0.9c has roughly 20 times as much kinetic energy as the total gravitational binding energy of the neutron star.  My guess would be more along the lines of a colossal explosion that blows most of the mass from both objects permanently away from the system.  Dragons flight (talk) 11:22, 6 September 2017 (UTC)
 * Sorry, but the mass of a neutron star is about 1.5 solar masses and size of about 20 km. The mass of a typical white dwarf is about 0.6 solar masses and size of about Earth's one - ~12,000 km. The neutron star will act like a bullet - it will just pass through the white dwarf unscathed while making a short lived hole in it. The white dwarf will also survive. Ruslik_ Zero  20:33, 6 September 2017 (UTC)
 * You need to justify the treatment of the objects as rigid objects here. The nuclei in the neutron star will collide with nuclei in the white dwarf and the binding to the neighboring nuclei can be ignored in a first approximation at these relative velocities. So, the collision between the objects becomes like the collision of two liquids. The relative speed needs to be significantly lower than the speed of sound before the binding of the nuclei with each other becomes an important factor and then the collision can be treated as a rigid object collision. But I think Dragons flight is right that due to the dissipated kinetic energy the system will then become unbound. Count Iblis (talk) 22:19, 6 September 2017 (UTC)
 * Sorry, I do not understand what you are talking about. The matter inside the neutron star is eight orders of magnitude denser than the matter in side the white dwarf. So, the NS moving inside WD is equivalent of a supersonic tungsten bullet moving in the martian air. The speed is high enough so that at the timescale of the encounter nothing will have time to happen inside the WD (though not inside the NS because it is very small and the corresponding timescale is short despite the relatively low sound speed). So, the NS will just push the WD matter in front of it forward and out of the WD. However, the ram pressure on the surface of the NS will be about 1/1000000 of that inside it (your can estimate it yourself). Therefore, the encounter will have negligible impact on the NS. It will be basically equivalent to a hammer hitting a bell - it will cause some vibration inside the NS but nothing of significance. For the WD the consequences will be more serious - it will have a tunnel in it for a short time and a shock wave moving from it. The latter will eventually decay into some vibrations although their energy will be still small as compared to the WD binding energy. Ruslik_ Zero 20:16, 7 September 2017 (UTC)
 * Well couldn't the collapsing of that tunnel cause the white dwarf to go supernova(Ive heard one kind of supernova is from mass impacting a white dwarf at high speed, and the collapse of a tunnel in center of white dwarf would have some similarity)?144.35.45.42 (talk) 02:09, 8 September 2017 (UTC)
 * Ignition of CO mixture inside the WD is possible though this requires temperatures in excess of 3 K. How much matter will burn and whether the WD survives is impossible to estimate without a detailed modeling. Ruslik_ Zero 18:10, 8 September 2017 (UTC)
 * The relativistic shock front created by the neutron star plowing through white dwarf matter seems like an excellent candidate for ignition to me. Dragons flight (talk) 19:06, 8 September 2017 (UTC)


 * Yes, I now see Ruslik's point about the far lower density of the white dwarf causing the neutron star to move through, I stand corrected on this. Count Iblis (talk) 19:57, 8 September 2017 (UTC)

neutron stars
Can there be neutron stars at the center of white dwarfs?144.35.45.46 (talk) 23:43, 5 September 2017 (UTC)


 * Take a look at Thorne–Żytkow object. A neutron star may exist at the centre of a white dwarf for a few seconds as it goes supernova too! Graeme Bartlett (talk) 05:15, 6 September 2017 (UTC)


 * Why can't the outer parts of a white dwarf be esentially part of an accretion disk for the neutron star inside and take longer to fall in?144.35.114.203 (talk) 14:37, 6 September 2017 (UTC)


 * An accretion disk is, after all, a disk, and not a sphere. The objects in the disk orbit around the central object until they fall in, so that only works in one plane, because multiple orbital planes would interfere with each other. StuRat (talk) 22:34, 6 September 2017 (UTC)


 * scarcely relevant-plenty of stuff still in the disk region>144.35.45.42 (talk) 00:24, 8 September 2017 (UTC)


 * Well, it's not a white dwarf star (or any other type) if it's an accretion disk, right ? StuRat (talk) 05:17, 8 September 2017 (UTC)


 * I've posted a graphic from the neutron star article. Note that a neutron star is surrounded by condensed matter.  If you look close enough to the surface I assume you even see some ordinary neutral molecules.  The gravity is intense at the surface, but the pressure depends on the depth within the stellar material, and still would be expected to drop to zero at the surface (ignoring atmosphere, that is!)  Note neutron stars do have an atmosphere  but the scale height is quite smaller than on Earth - the one in the link has just 4 inches of hot carbon atmosphere! Wnt (talk) 20:56, 8 September 2017 (UTC)