Wikipedia:Reference desk/Science

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

The Wikipedia Reference Desk covering the topic of science.

Welcome to the science reference desk.
Want a faster answer?

Main page: Help searching Wikipedia

How can I get my question answered?

  • Provide a short header that gives the general topic of the question.
  • Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
  • Post your question to only one desk.
  • Don't post personal contact information – it will be removed. All answers will be provided here.
  • Specific questions, that are likely to produce reliable sources, will tend to get clearer answers.
  • Note:
    • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
    • We don't answer requests for opinions, predictions or debate.
    • We don't do your homework for you, though we'll help you past the stuck point.
    • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.



How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

  • The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
 
Choose a topic:
 
See also:
Help desk
Village pump
Help manual


November 11[edit]

Java Programming[edit]

For java programming, what is the difference between read() and next()?

For example:

Let's say I import the java Scanner class. Then I proceed as follows:

Scanner userInput = new Scanner(System.in); System.out.print("Enter the number of students: "); int numberOfStudents = userInput.nextInt(); System.out.println("The number of students you entered is: " + numberOfStudents);

My question is would this work if I replaced "int numberOfStudents = userInput.nextInt()" with "int numberOfStudents = userInput.readInt()"? What is the difference between next and read? When should one be used over the other?

ThunderBuggy (talk) 17:20, 11 November 2018 (UTC)

According to the documentation Scanner class does not have readInt method. Ruslik_Zero 20:27, 11 November 2018 (UTC)
So I would have had to create a readInt method before using it then, right? And the "next" methods are included with the Scanner class? ThunderBuggy (talk) 03:29, 12 November 2018 (UTC)
This isn't a general Java language question but, like nearly all Java questions, a question about different libraries used by Java. As Java has been around a while, there are many such libraries and they're often inconsistent. If we started again, we wouldn't have so many of these variations.
For the Scanner library class,[1] this implements and extends the Iterator<String> classinterface [2], which defines a next() method.
What Iterator does is that it allows next() to read, identify and move past a series of "tokens" in the input stream. That means you can write an input loop for a long series of tokens with just a simple loop. Then Scanner extends this, so that it recognises different types of token, such as nextInt() to read integers.
Don't mess with next() etc. by trying to rename or facade them as something else. Otherwise you lose the advantage of using Iterator in a consistent and clearly understood way. There is no readInt() in Scanner or Iterator.
readInt() comes instead from DataInputStream[3] rather than Scanner. This is part of java.io rather than java.util.
Now we see the crucial difference! java.util is for chopping up bits of well-behaved data which are already loaded into memory. java.io though is for dealing with the nasty real world of outside interfaces, data sources which stop halfway or timeout.
So for what you're doing here, then yes, base it on DataInputStream and readInt(), rather than Scanner and nextInt(). You're doing this because of the purposes of the different classes (DataInputStream understands real world IO), not simply the different methods. Andy Dingley (talk) 13:55, 12 November 2018 (UTC)
Iterator is an interface, not class. So, Scanner class implements it and extends Object class. Ruslik_Zero 20:43, 12 November 2018 (UTC)

Fat and the blood-brain barrier[edit]

According to Wikipedia the human brain is nearly 60 percent fat. Also according to Wikipeida fat cannot cross the blood–brain barrier, hence the need for the liver to convert fat into ketone bodies which can then cross the blood–brain barrier and nourish the brain during periods of starvation. "Unlike free fatty acids, ketone bodies can cross the blood-brain barrier". So explain to me how the brain came to be 60 percent fat if fat cannot reach the brain due to the blood–brain barrier. 200.122.209.78 (talk) 19:51, 11 November 2018 (UTC)

See Lipogenesis. There's a reason you can get fat even if most of your energy comes from carbohydrates (such as sugars or starch) or protein and not fat. Nil Einne (talk) 20:35, 11 November 2018 (UTC)

November 12[edit]

Physics : Time[edit]

I wanted to know how could time possibly slow down with speed if it does will it affect biological growth of a human.Navjot1200 (talk) 11:39, 12 November 2018 (UTC) -

Time dilation depends on the relative speed of the observer. Your own time does not slow down from your own perspective, and everything happens exactly the same regardless of your speed (if gravity/acceleration is the same). It doesn't even make sense to ask how fast you are moving unless it is measured relative to something else. According to relativity there does not exist "fixed points" in the universe or an "absolute speed" compared to such points. You age normally but if you move very fast relative to observers then it looks to them like you are aging slower. However, if you are moving fast enough for time dilation to be significant for an observer on Earth then you are probably on a spacecraft where the gravity/acceleration may not be the same as on Earth, and that does affect biological processes. This may be avoided by a rotating spacecraft where your acceleration due to the rotation corresponds to the gravity of Earth. Gravity and acceleration are indistinguishable in the theory of relativity. PrimeHunter (talk) 12:45, 12 November 2018 (UTC)
Just to nitpick, while gravity and linear acceleration are indistinguishable, using a rotating spacecraft to create pseudogravity is distinguishable from Earth's gravity or from a spacecraft accelerating in a straight line. On a rotating spacecraft there would be an acceleration gradient between your head and your feet; since your feet are rotating faster, they would experience more pseudogravity. If you ran in such a spacecraft, running with the rotation direction would make you feel heavier, while running against the rotation would make you feel lighter. You would also experience Coriolis forces, so if you jumped in the air or suddenly stood up, you would feel a force pushing you backwards compared to the direction of rotation. --Ahecht (TALK
PAGE
) 16:21, 13 November 2018 (UTC)
How is that scenario distinguishable from a spacecraft in orbit rather than in straight-line free-fall?--Jayron32 16:53, 13 November 2018 (UTC)
Both are free fall and thus are hard to tell apart, but you can still tell that you are in orbit because of the tidal forces tend to make things closer to the planet than the center of mass slowly fall and things farther from the planet than the center of mass slowly rise. Or sometimes not so slowly. See Space elevator#Apparent gravitational field. --Guy Macon (talk) 08:53, 14 November 2018 (UTC)
In free fall towards the centre of the Earth will have a quick end to time for you when you impact the surface. If there was no surface and a black hole is there instead, there will be even more serious effects. Graeme Bartlett (talk) 06:09, 15 November 2018 (UTC)
Depends whether you'd rather die by a splat or a slurp. ←Baseball Bugs What's up, Doc? carrots→ 16:45, 15 November 2018 (UTC)
"It isn't the falling that hurts you. It's the landing". Is there any particular reason for assuming that the free fall is towards the the earth? --Guy Macon (talk) 14:55, 15 November 2018 (UTC)
Or the Moon, or Mars, or wherever. ←Baseball Bugs What's up, Doc? carrots→ 16:44, 15 November 2018 (UTC)

November 14[edit]

Electric/electronic device getting charged with static electricity[edit]

Why some non-earthed devices get charged with static electricity (and others not)?--Doroletho (talk) 00:21, 14 November 2018 (UTC)

It depends where they and whatever touches them are on the Triboelectric series. --Guy Macon (talk) 02:13, 14 November 2018 (UTC)

Aerothermal heating[edit]

I was expecting to find something else in the link above. It actually forwards to Aerodynamic heating (heating of a solid body produced by its high-speed passage through air). I was interested in a purported home heating/cooling system, that paired with a heat-pump, could harvest energy out of thin air (literally). That is, it can recover energy from air around the house. Supposedly, it could save up to 2/3 of power spent heating or cooling. Is this a viable heating and aircon system? Or is it an 'air-con' scheme? Is it possible to obtain energy from air (which has some energy in it, if not at absolute zero)? Or is it like the water powered car (that converts water into hydrogen with a battery, just to burn it in a fuel cell). I don't want to link to the companies offering it, but 'Air Source Heat Pumps' or 'Aerothermal heat pumps'. There's a Air source heat pumps article, but it is in chronically need of references and a more scientific background. --Doroletho (talk) 00:48, 14 November 2018 (UTC)

Your statement "air (which has some energy in it, if not at absolute zero)" is factually incorrect. You need a temperature difference to extract any energy from the air. See Heat engine.
A heat pump is simply a clever way of using less electricity to heat your home. A normal electric heater gives you one watt of heating for one watt of electricity. A heat pump is basically an air conditioner that is trying to cool the great outdoors and which has the cooling fins inside your house instead of outside. Every watt you put into it gives you one watt of heat, just as in the electric heater, but it also cools down the cold side (which is outside) by pumping heat to the warm side (which is inside), so you get more heat for the same amount of electricity.
I agree that the articles on this are a mess, and a quick look showed me some things that simply are not true, like "By definition, all heat sources for a heat pump must be colder in temperature than the space to be heated." Whoever wrote that has no understanding of how heat pumps work. I am a bit busy at the moment, but in a week or so I will clean up the articles. --Guy Macon (talk) 02:39, 14 November 2018 (UTC)
The Volumetric heat capacity of Air is very, very low. See Heat_capacity#Table_of_specific_heat_capacities where Air is listed with 0.00121 and Water with 4.1796. You would have to compress gigantic volumes of air to heat the water for your central heating for a house. Heat pump systems that draw heat from a grid of tubes installed underground, in a riverbed and alike commonly use Ammonia (3.263) or similar suited chemicals for the heat extraction. --Kharon (talk) 05:09, 14 November 2018 (UTC)
Ground source heat pumps are one solution and they do often result in energy savings compared to air source, but Air source heat pumps are probably the most common by far. I've never heard of anyone using a ground source heat pump in NZ (I mean I'm sure there's someone), but (air source) heat pumps are becoming increasingly popular her in NZ with a lot of ads on TV etc, promotion by the government etc. Of course winters here are fairly mild, especially in Auckland. And also most homes have no central heating plus piped gas or other non electric heating is not so common, with wood burners (whether crappy old fireplaces or modern insert type ones) being the most common non electric [4]. According to this [5] air and water source heat pumps have 7x the installations of ground source in Germany and combined they have also just exceeded gas, for domestic heating. I find the water source bit a bit weird, I wonder if they actually mean air to water. Actually on that note, I should mention heat pump hot water systems are also gaining ground in NZ. Nil Einne (talk) 06:58, 14 November 2018 (UTC)
BTW, as for your volumetric heat capacity, I think you're overanalysing things you don't understand. Remember as Guy Macon already said, the Coefficient of performance for heat pumps, with reasonable outside temperatures is significant above 1. If you can heat a home with a 8kW electric heater (to give a random example) then you can do so with a heatpump for less, perhaps 4kW. Whether you're directly heating the air of the home, or heating water to distribute it through the house doesn't ultimately matter in terms of what you need. (Okay it can affect how well the heat is distributed and efficiencies but you choose whatever solution you find is best for cost-performance reasons.) The only reason you're heating water is to eat the air, occupants and furniture of the house. Nil Einne (talk) 07:10, 14 November 2018 (UTC)
I'd be pretty careful with that stuff, just because it's brand name doesn't mean it's any use. For example, here summer dewpoints are 15-25°C but there's never a shortage of 300-1000€ brand name swamp coolers on sale, despite the fact that in any heat wave this climate makes them pretty much glorified fans. 78.0.233.248 (talk) 05:30, 14 November 2018 (UTC)
The phrase "You would have to compress gigantic volumes of air" above shows a misunderstanding about how such systems work. We aren't talking about using air as the refrigerant, but rather using fins with a fan blowing across them to do the actual heating/cooling of the air. No compression needed.
Re: ground source vs. air source, ground source costs more to install and requires access to some ground (not practical for a 30th-floor apartment in NYC) but the heat pump doesn't have to work so hard; on a really hot day the ground is cooler than the air, and on a really cold day the ground is warmer than the air. These are just engineering details; the basic design is the same either way. --Guy Macon (talk) 08:46, 14 November 2018 (UTC)
You seem to be describing what is known in Australia as a reverse cycle air conditioner. In summer we blow heat out into the atmosphere and cool the house. In winter we cool the atmosphere and heat the house. The latter is actually more 'efficient', as the power used to drive the pump also heats the house. Guy's points are also well made. We also have air to water heat pumps that use the air as a reservoir of heat energy and warms the domestic hot water. Again the pump energy actually ends up where you want it. These ssytems all work whatever the temperatures involved, that is, you can use air at 20 deg C to heat water at 60 deg C. Greglocock (talk) 10:24, 14 November 2018 (UTC)
Has anyone ever figured out a way to make one of those things so it doesn't make the entire neighborhood sound like a fan room? Related: Does anyone in the world value the sound of an honest breeze? Wnt (talk) 12:33, 15 November 2018 (UTC)
We know how to make quiet fans with any desired capacity -- basically more volume of air at a lower velocity and a careful design to maximize laminar flow and minimize turbulance. for example, https://www.bigassfans.com/ makes fans that move a lot of air without making a lot of noise. What we don't know is how to make a quiet fan as cheap as the noisy fans are. --Guy Macon (talk) 15:04, 15 November 2018 (UTC)
We have an ASHP that is much quieter than our previous oil boiler. It's a significant benefit.--Phil Holmes (talk) 16:29, 15 November 2018 (UTC)
The fan on our ASHP is rated at 34 dB, so it's basically inaudible. The compressor, however, is a bit noisier than the gas boiler that it replaced. Mikenorton (talk) 18:59, 15 November 2018 (UTC)
Are you talking about the total noise produced, or the total noise as experienced from inside the offending house if every window is always kept closed and the machinery is put somewhere outside on the far side of a barrier? Wnt (talk) 01:45, 16 November 2018 (UTC)
The internal machinery is in the place that the old oil boiler was - a small room within our kitchen. The external machinery is just outside the kithen window. It is much quieter inside and somewhat quieter outside, standing next to the external untit.--Phil Holmes (talk) 10:24, 16 November 2018 (UTC)

November 16[edit]

Car running cheaper with electricity than gasoline[edit]

How come it's cheaper per mile to drive electric cars than to drive gasoline ones? For me, electricity is the "most pure" form of energy. It's an energy that can be easily be converted into anything you wish: heat, movement, cooling, light. Shouldn't it be more expensive per kW to use electricity instead of gasoline (which can be useful everywhere else)? --Doroletho (talk) 15:15, 16 November 2018 (UTC)

Are you saying electricity is cheaper per mile than gasoline, or that gasoline is cheaper per mile than electricity? ←Baseball Bugs What's up, Doc? carrots→ 15:21, 16 November 2018 (UTC)
Sorry, corrected. --Doroletho (talk) 15:35, 16 November 2018 (UTC)
There's lots of contributing factors. Generating stations are more efficient and don't pay the same tax. Petrol engines are not efficient at all speeds - this is why diesel electric trains are so much better than pure diesel.. There's a small gain when going downhill with electric. There is also the gain from less pollution in cities which will lead to better health and perhaps intelligence which should I'd have thought also be counted in any monetary evaluation. Dmcq (talk) 15:42, 16 November 2018 (UTC)
(Personally I consider less pollution in cities a Pyrrhic victory. Better if the polluters smoke up their own town and leave the rest of us alone... 78.0.230.255 (talk) 22:23, 16 November 2018 (UTC))
Regenerative braking to recover energy also makes the car much more efficient overall, for example a Toyota Camry hybrid is 10-20 mpg more efficient than the base version depending on driving conditions. shoy (reactions) 16:04, 16 November 2018 (UTC)
See also Electricity pricing which can vary greatly depending on the area. EniaNey 15:55, 16 November 2018 (UTC) — Preceding unsigned comment added by EniaNey (talkcontribs)
Economically most developed countries established high taxes on fossil fuel to finance the road system. Electricity is generally much lower taxed, if at all. Technically electric engines are close to 100% effective in converting energy to movement. Electrical Battery storage is typically around 80%. Combustion engines only achieve 20-30% and of course a fuel tank stores fossil fuel at no loss. Additionally Electricity is produced at much higher efficiency in huge power stations. Even if they burn fossil fuel, they can achieve over 60% efficiency. Power stations based on renewable energy practically produce electricity for free since their energy source is endless/renewable. Last factor is the power grid that may lose another 10-15% electricity over longer distances. So electrical mobility is clearly more effective. But fossil fuel cars or trucks etc. still have a huge advantage in refueling time and reach with one filling. Much more even big planes. An A380 can fly almost 16000 Km with one tank filling and refilled in maybe 10 min or less. The Tesla Model X 100D may reach 475 km but then needs at least 75 min to charge.
So its a mixed comparison since combustion and electrical engines are at the end of possible development but batteries are still believed to have huge development potential. Thus slight advantage for electrical mobility. Besides electrical Trains beat everything in efficiency since they where used the first time. --Kharon (talk) 19:01, 16 November 2018 (UTC)
80% x 60% x 85% isn't a lot more than 30%. I think a hybrid running on propane should easily outperform this figure, not to mention it'll be much cheaper and much more convenient. 78.0.230.255 (talk) 22:23, 16 November 2018 (UTC)
Some fossil fuel power stations may achieve 60% efficiency, but your average 25 year old coal fired power station, designed in the 1980s, has an efficiency of about 40%. Factor in the other losses and it appears that a car with a petrol engine is probably more efficient at converting fossil fuel into movement than an electric car ultimately powered by a fossil fuel power station. The advantage of the electric car is that it won't kill your neighbour and that it can switch to clean electricity when available.
The point is that the fossil fuel power station isn't fuelled with petrol. It may use low-grade bunker oil, already much cheaper than petrol, but that's usually considered still too expensive. Most fossil fuel power stations burn coal or natural gas, which are just impractical for road vehicles. PiusImpavidus (talk) 11:50, 17 November 2018 (UTC)
In the UK at least, there are very few active coal power stations and no active oil-fired stations. More electricity comes from combined cycle gas (i.e methane, not petrol), nuclear, and wind than from coal. Last year nearly 50% of the UK's electricity was zero-carbon at point of generation.--Phil Holmes (talk) 17:27, 17 November 2018 (UTC)
In the EU-28 in 2014 coal and lignite was 25% [6]/[7] and natural and derived gas 15%. Oil was 2% and other fuels 1%. Nuclear 28% and renewables 29%. Nil Einne (talk) 20:14, 17 November 2018 (UTC)
In NZ, although electric cars are not very common and we're a tiny tiny percentage of the global production, [8]/[9] in 2017 it was 58% hydro, 17% geothermal, 0.4% biogas, 4.9% wind, 0.2% solar PV, 0.012% oil, 1.2% coal, 13% gas and 4.91% cogeneration (I believe most of this is gas but I'm not certain). See also [10] and Electricity sector in New Zealand. However coal usage in energy overall remains higher [11] and per earlier sources. Also there's a lot of political controversy over whether the ban on new gas and oil exploration permits will lead to more use of coal for electricity generation (or just increase gas imports, or neither) [12] [13] amongst the generally more international focus of the possible effects [14] Nil Einne (talk) 20:39, 17 November 2018 (UTC)
BTW the US in 2017 was [15] 32.1% natural gas and 29.9% coal. Petroleum liquids are 0.3% and petrol coke is 0.2% and other gases are 0.3%. Nuclear is 20.0% and renewable 17.0%. Other sources are 0.3% and pumped hydroelectric is -0.2%. Nil Einne (talk) 22:16, 17 November 2018 (UTC)
Petrol engines can achieve 40% efficiency when they are in optimum conditions. But stopping and starting and or going at the wrong speed for maximum efficiency reduces that very considerably. It has far less effect with electric motors and they can actually gain a bit back from braking instead of it being a total loss. There is a very good reason so many big engines are diesel electric rather than pure diesel. One of the major gains is that they enable the diesel engine to run with optimum efficiently or else be switched off. This is also used in hybrid cars. Dmcq (talk) 21:37, 17 November 2018 (UTC)
With regards to the efficiency issue, this has various comparisons [16]. Although a news source, the data seems to come from the EU. It includes various sources for the electricity including the EU-mix and oil, but not coal. It includes the cost of extraction and transport for the petrol, and the various costs for the electricity. The full electric beats petrol, although plug in hybrid can beat full electric e.g. with nuclear. (To be clear, this is for energy, on a GHG basis full electric on nuclear does very well as you would expect.) There seems to be a colouring error with some of them relating to the highlighting but I'm assuming the data is still right. I don't know what sort of driving profile is assumed but I suspect it's the average city dweller in the EU. However for the full life cycle analysis it's mentioned at the end it's disputed if electric is actually better. Also we have a Environmental aspects of the electric car article, I don't know how good it is but it has a bunch of refs. Nil Einne (talk) 22:32, 17 November 2018 (UTC)
There is a difference in comparing energy systems, manufacturer methods and material choices. Besides you can also re-equip old vehicles by ripping out their combustion engine and build in some electrical engines and batteries. I bet this becomes a "thing" soon. Would love to drive an "electrified" old luxury class Mercedes-Benz or Jaguar. --Kharon (talk) 01:03, 19 November 2018 (UTC)

November 17[edit]

neon bulb as sensor[edit]

hello, I had this weird idea. does the breakdown voltage of a neon bulb (the kind used in phase testers, illuminated switches etc) depend at all on external conditions (temperature, incident visible light, UV, α, β, γ)? IOW, if I brought a neon bulb to a few mV below breakdown, could it detect stuff? or, better yet, if I made made an oscillator and measured the frequency (f-to-V), would it reflect something? Aecho6Ee (talk) 20:17, 17 November 2018 (UTC)

Yes.
Just what is a harder question. Neons, especially older ones, are sensitive to all manner of environmental factors. You can even use them as random number generators. Andy Dingley (talk) 22:44, 17 November 2018 (UTC)
Ionizing radiations such as gamma radiation, X-rays, and alpha and beta particles can all trigger electrical breakdown in a neon tube, as exploited for their detection in the Geiger–Müller tube. DroneB (talk) 15:54, 18 November 2018 (UTC)

November 18[edit]

Why do cats lick themselves when you scratch them near the base of the tail?[edit]

I've had at least two cats who do this. They lick their chests or their front paws. Is it a reflex? Is it an indication that they like it, that they don't like it, or neither one? --Trovatore (talk) 00:33, 18 November 2018 (UTC)

I've only seen females do that, though sometimes they just lick the air and chirp while looking in random directions. If they they tolerate the person doing so at all, they usually start purring and don't run off after. That spot would be getting... friction during mating.
My mom's current male and my brother's male both like being patted there but not scratched, and only by their favorite individuals after a period of learning to trust that patting is all that's going to happen. In the case of my mom's cat, Gravy is either to be found tucking his head into my hand (to hell with whatever I'm doing or holding) or sitting next to my bedroom door singing "I Can't Stop Loving You". My brother's cat is a complete misanthrope but deigns that my brother and his girlfriend should be exterminated last. Ian.thomson (talk) 00:58, 18 November 2018 (UTC)
My current Mama Cat (spayed female) licks her chest and seems to be OK with it, but it's hard to be sure. My late lamented Sox (neutered male), maybe the sweetest cat who ever lived, would sometimes lick his paws violently from a mere touch in that spot. I got the sense that it distressed him so I tried to avoid it, although it seemed to come and go — I'm thinking maybe there was some intermittent skin condition or nerve problem. --Trovatore (talk) 01:08, 18 November 2018 (UTC)
This site says that cats generally do not appreciate being touched there. A study in Applied Animal Behaviour Science found likewise. Most male cats I've encountered who were otherwise enjoying my presence would get angry if I tried to go there. Females would either be confused at first or way too receptive to only males petting them there. This is why I strongly suspect that that area has nerves that would be stimulated by having the receptive role in mating (which for most male cats would be disturbing for anyone they don't submit to). Ian.thomson (talk) 01:32, 18 November 2018 (UTC)

White dwarf -versus- Wolf-Rayet: who wins?[edit]

In one corner, we have R136a1, a Wolf-Rayet star, 50000K surface temperature, 315 solar masses. In the other, on a slow collision course, we postulate a puny white dwarf like one of the stars in SDSS J0106-1000, 0.17 solar masses, made of a condensed plasma 5000 times denser than anything we know on Earth.

Question: who wins this fight? Does R136a1 bring the heat of its core to bear, or of gas it dumps onto the oncoming challenger, to the point where the white dwarf unbinds and becomes a cloud of carbon and oxygen atoms again? Or does the aging supergiant take to condensed matter like a new religion, and become reorganized onto the white dwarf, while presumably ejecting a larger amount of material because the infalling material produces enough heat to blast it away? Or, for that matter, does some aspect of the interaction simply bat the white dwarf away like a grandmother beating off a rabid squirrel with her laptop? Wnt (talk) 00:33, 18 November 2018 (UTC)

The low mass helium white dwarf will quickly sink to the center of the WR star and will be quietly sitting there (surrounded by hot helium core material) and slowly evaporating. Otherwise there will be no changes in the appearance of the WR star. I can not say how much time it will take for the WD to completely evaporate. Ruslik_Zero 20:21, 18 November 2018 (UTC)
I don't feel convinced. According to this the CNO cycle starts at 1.5 x 107 K, which seems comparable to the 1 x 107K figure our article on white dwarf gives. True, this one is presumably well past that threshold, but on the other hand, well, the Sun has a density of 1 g/cc like water, and R136a1 has 315 solar masses packed into a radius about 30 times larger, which is to say, it has about an aerogel-like density (maybe it beats styrofoam at the middle, but I doubt it). So if the innards of that star are a few times hotter than the white dwarf but now the gravity is increased from being proportional to styrofoam to tons-per-teaspoon, I am thinking the white dwarf is going to account for itself quite well ... unless, that is, there is a way to evaporate or destroy it first? Wnt (talk) 23:35, 18 November 2018 (UTC)
There are no collision courses! The universe is full with Binary stars and systems containing multiple suns that circle each other in stable or even chaotic pattern for billions of years without colliding. Its a common misconception based on our bad habit to display stellar objects and their distance between each other totally out of proportion, to get a visual picture with all objects visible. But in reality, with the proper proportions most system objects become invisible, like normal humans cant see any other planet of our system unless gifted with very good sight or an telescope and the knowledge when to look where exactly at night under very good weather conditions. --Kharon (talk) 00:44, 19 November 2018 (UTC)

Breaking the Earth[edit]

How much blow it takes to break the Earth like a pottery? Impact of a Mars-sized world could've easily broke the Earth into pieces therefore we wouldn't be here to discuss this very topic. There's a theoretical weapon as seen in sci fi powerful enough to break the Earth. PlanetStar 03:08, 19 November 2018 (UTC)