Wikipedia:Reference desk/Science

February 3

Antique car terms

What does of opposed 6x4 ins cylinders far in front crosswise side chains to rear drivers on page 225 of 1906 Automobile Trade Journal, Volume 10 mean? --Doug Coldwell (talk) 11:04, 3 February 2022 (UTC)

It seems to be describing part of the Lambert friction gearing disk drive transmission, which used chains as the final part of the transmission. There are several articles relevant to these early cars/trucks, for example Lambert Automobile Company and Buckeye gasoline buggy. Mike Turnbull (talk) 12:30, 3 February 2022 (UTC)

• Interested specifically in what 6x4 ins cylinders means.--Doug Coldwell (talk) 15:41, 3 February 2022 (UTC)

The reference you cite says: "and has cylinders of 6x4½ ins.," – this is the bore × stroke so the cylinders were 6 in (150 mm) in diameter with a stroke length of 4.5 in (110 mm) giving a total displacement of 127 cu in (2,080 cm³) Martin of Sheffield (talk) 16:30, 3 February 2022 (UTC)

To make the math more explicit, the volume of a cylinder is πr²h, so that's 3.14 * 3 in * 3 in * 4.5 in = 127 in³ --Jayron32 16:42, 3 February 2022 (UTC)

Yes, but possibly better expressed when the bore is given as π(D⁄2)²h or possibly even π(B⁄2)²S Martin of Sheffield (talk) 17:03, 3 February 2022 (UTC)

Indeed and more accurately so, because π is not equal to 3.14. Philvoids (talk) 17:57, 3 February 2022 (UTC)

and 6 inch is not 150 mm but 152.4 mm, and 3.14 × 3 in × 3 in × 4.5 in is not 127 in³ but 127.17 in³, and 127 in³ is not 2,080 cm³ but 2,081.157128 cm³. Tsk tsk, what is the Reference desk coming to...  --Lambiam 21:24, 3 February 2022 (UTC)

The endless decimal places of numbers like Pi are misleading. 3.14 is implicitly 3.1400, while 3.1416 is closer to the actual value of Pi. But the difference between the two numbers is only 1.6 one-thousandths. --←Baseball Bugs ^{What's up, Doc?} carrots→ 21:35, 3 February 2022 (UTC)

Unless anyone can tell me to what accuracy the original cylinders were made in 1906, I'd guess that 2 sf is reasonable. Anyhow, O-level maths taught us that your 3.1416 isn't accurate, the figure we learnt was 3.14159. Kids today! They never learn like we used to in the old days. :-) Martin of Sheffield (talk) 22:45, 3 February 2022 (UTC)

To one less trusting than BB above, 3.14 to me implies only ( >3.135 AND <3.145 ). I am assured that π is somewhere in that range but it's not easy to pin down. Philvoids (talk) 11:03, 4 February 2022 (UTC)

Useing 3.14 and 3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066063155881748815209209628292540917153643678925903600113305305488204665213841469519415116094330572703657595919530921861173819326117931051185480744623799627495673518857527248912279381830119491298336733624406566430860213949463952247371907021798609437027705392171762931767523846748184676694051320005681271452635608277857713427577896091736371787214684409012249534301465495853710507922796892589235420199561121290219608640344181598136297747713099605187072113499999983729780499510597317328160963185950244594553469083026425223082533446850352619311881710100031378387528865875332083814206171776691473035982534904287554687311595628638823537875937519577818577805321712268066130019278766111959092164201989 both give the answer as 127 in³ when rounding to the whole cubic inch, which seems reasonable given the precision of the measurements (it's actually TOO precise, as the diameter is given as 6 inches, and not 6.00 inches; at 1 significant digit, anything more precise than 100 cubic inches represents a false precision). But anyone who actually knows how to do math would have known that already and not tried to feed extra digits of pi into their calculator that will just get rounded off in the final answer anyways. --Jayron32 12:05, 4 February 2022 (UTC)

Grey-on-white texts

Some websites routinely display text as dark grey (such as #262626) on a white background. I find this harder to read, and especially so when the font is thin (such as Roboto), and wish I could turn this off. Question: is there some known reason for this presentation style?  --Lambiam 12:21, 3 February 2022 (UTC)

The reason is likely that the people who do this are bad at design? --Jayron32 12:52, 3 February 2022 (UTC)

Who does the website design, and for whom? Typically someone with an artistic flair is contracted to create a website for a customer. They are not contracted to produce a website for the readers, if it looks good then they get paid. The requirement is that the website stands out from the competitors and has all the latest "snazzy" tricks. Martin of Sheffield (talk) 13:42, 3 February 2022 (UTC)

Can you link an example? --←Baseball Bugs ^{What's up, Doc?} carrots→ 14:20, 3 February 2022 (UTC)

Here are two examples: UScourts.gov (maintained by the Administrative Office of the US Courts on behalf of the Federal Judiciary – no competitor) and Scientific American, which is even grey-on-grey, a form of torture (likely an in-house job; their "Senior Web Producer"?). There was a pre-Internet period when brown-on-yellow textbooks were in vogue under the theory (if I recall correctly) that the lesser contrast in intensity reduced eye strain.  --Lambiam 14:46, 3 February 2022 (UTC)

As a child mentally digesting Children's Digest that for many years was printed on light green paper, which the pubisher claimed avoided eye strain while reading, I concluded only that it was published on the cheapest possible unbleached pulp paper. Philvoids (talk) 17:52, 3 February 2022 (UTC)

But see Irlen syndrome (probably not a thing, but coloured overlays are often used to treat dyslexia). Alansplodge (talk) 21:55, 3 February 2022 (UTC)

Phase of ammonia at NH3 at 10bar

What's the boiling temperature of ammonia at 10bar? I've seen numerous calculators and equations but they are all in disagreement with each other. JoJo Eumerus mobile (main talk) 20:23, 3 February 2022 (UTC)

According to this it is 298 K. Ruslik_Zero 20:39, 3 February 2022 (UTC)

Ammonia is one of those common chemicals where Wikipedia has a good data page with this and other information. Note that there is a big difference between concentrated aqueous ammonia ("880 ammonia", as often purchased) and the pure material that you presumably are interested in, Jo-Jo Eumerus Mike Turnbull (talk) 22:11, 3 February 2022 (UTC)

February 4

What organic compound can survive the highest temperature without autoignition or decomposition?

What about heating in a vacuum or inert gas? Sagittarian Milky Way (talk) 07:01, 4 February 2022 (UTC)

Combustion cannot take place without oxygen, so autoignition can be ignored. It seems that the saturated hydrocarbons resist thermal decomposition the best, but: "Even very dense hydrocarbons decompose at 1200° C."^[1] There are several articles on the thermal decomposition of n-alkanes,^[2][3] of none of which I could access the text.  --Lambiam 10:40, 4 February 2022 (UTC)

In vacuum or inert gas it can't (unless it can burn itself like nitroglycerin), if you heat it the easiest way of course it might become inorganic by burning with the O2 in the air instead. So without oxygen seems to be saturated hydrocarbons then, they can survive more heat than I thought! Sagittarian Milky Way (talk) 15:37, 4 February 2022 (UTC)

The paper High Temperature Organic ΉElectronics identifies phenyl-substituted DNTT (dinaphtho[2,3-b:2,3-f]thieno[3,2‐b]thiophene) as stable after sterilization above 200°C and cites demonstration by Gumyusenge et. al. of organic transistor structures that are functional up to 250°C. Philvoids (talk) 10:53, 4 February 2022 (UTC)

I wonder if this could ever help with CPU cooling: simply let it reach 240°C. No one ever seems to invent something better than silicon despite progress becoming ever harder with it and many candidates for replacement. Sagittarian Milky Way (talk) 15:37, 4 February 2022 (UTC)

Silicon has the advantage because it has the correct electrical properties for use in semiconductors. It isn't really a question of "inventing something better". There are a limited number of chemical elements to do the job with, and there isn't necessarily anything as yet better suited to the task and also meeting all of the constraints in terms of cost and availability and the like. --Jayron32 16:45, 4 February 2022 (UTC)

I saw a 1980s book that said technology so and so will probably make CPU transistors switch every few picoseconds or less by the 1990s, years ago I saw a slide from Intel I think that said there's a bunch of after silicon candidates, some semiconductor with two elements was supposed to be in the lead, some nanometer (3? 5? 7? I forgot) was supposed to be this, blah blah blah. Replacement of silicon with something with potential for orders of magnitude better seems to stay forever in the future, like trying to drive to the end of the rainbow. By invent I didn't meaning making a semiconducting compound no one's ever thought of before but learning how to work out all the kinks to make chips from it that'd outcompete silicon. That clearly hasn't happened yet and seems to be a near insurmountable engineering problem. Sagittarian Milky Way (talk) 20:04, 4 February 2022 (UTC)

• If you're interested in high temperature computing, look into the work towards new long-term Venus surface probes, using silicon carbine and the like. Fgf10 (talk) 18:04, 4 February 2022 (UTC)

• I think you mean silicon carbide; it's not exactly a new invention; it was actually one of the first semiconductors used by the electronics industry. I don't think their using sawed off machine guns in computers. --Jayron32 18:10, 4 February 2022 (UTC)

February 5

Chickens

How does chickens don’t move head when moved?

https :// youtu. be/ yetr1YDZwz8

--37.116.102.74 (talk) 09:55, 5 February 2022 (UTC)

This link works: https://www.youtube.com/watch?v=yetr1YDZwz8 . The domesticated chicken is a Flightless bird that has inherited the 3-axis head stabilisation ability of its flying ancestors. Philvoids (talk) 11:54, 5 February 2022 (UTC)

The ins and outs

The i of 1 December 2021 notes that on this day in 1997 "Kenny G set a world record when he held a note on his saxophone for 45 minutes and 47 seconds. The record has since been broken by Geovanny Escalante, who held a note for 1 hour, 30 minutes and 45 seconds, using a technique that allows him to blow and breathe at the same time." What is this technique? 86.175.202.208 (talk) 17:28, 5 February 2022 (UTC)

Circular breathing. Fgf10 (talk) 18:06, 5 February 2022 (UTC)

The previous record, of course, would also have had to involve this method. --184.144.97.125 (talk) 08:09, 6 February 2022 (UTC)

Catastrophic impact of asteroid on Earth

What difference does it make if an asteroid with a diameter of some km hits the Earth in the middle of the ocean? If we shoot at it with anti-aircraft artillery and break it up in smaller pieces? --Bumptump (talk) 19:37, 5 February 2022 (UTC)

Unless these pieces are small enough to evaporate in the atmosphere, the kinetic energy of the impact remains the same. Current anti-aircraft artillery will only make relatively small pits in a kilometres-deep rock. The highest altitude reached by artillery is Project HARP's world record of 180 km; if the asteroid is approaching with a speed of 94,000 kilometres (58,000 mi) per hour,^[4] that gives us a window of grace of less than seven seconds in which to shoot it to smithereens.  --Lambiam 00:40, 6 February 2022 (UTC)

Coincidentally (I assume), yesterday's issue of New Scientist magazine has an article on p10 ('We could save Earth from a planet-killer comet (if leaders listen to scientists)' by Jonathan O'Callaghan) reporting a recent study on precisely this topic, which can be found at [5]. The study was of course inspired by the recent film Don't Look Up.

The short take is that it would be possible to fragment a 10km-diameter comet or asteroid sufficiently if we were able to launch 1000 specially designed, precisely targeted and coordinated nuclear missiles 5 months before impact to reach the target 1 month before, although a few smaller fragments would likely still impact Earth and cause less-than-global damage and deaths. By implication, later and/or less than that would be insufficient.

As has been extensively discussed elsewhere, it would be much easier to prevent the object from impacting at all if it were deflected many months or several years earlier, but the study assumed the same scenario as the movie with the impactor only being spotted 6 months out (giving us 1 month to get our ordinance together). {The poster formerly known as 87.81.230.195} 90.209.123.164 (talk) 01:55, 6 February 2022 (UTC)

Responses so far have been concerned with the feasibility of breaking up the asteroid, but that's only part of the question. Someone must have worked out the damage from an oceanic strike by different sizes of impactor; so, supposing that we could break up this hypothetical asteroid, what difference would it make? --184.144.97.125 (talk)

As Prof. Jay Melosh explains here, in an ordinary impact, ejecta reentering the Earth's atmosphere will heat up and emit thermal radiation. This will cause the surface temperature to rise to hundreds of C and thereby cause the most severe immediate problems for the Earth's ecosystem. The total energy radiated to the Earth's surface is then equal to the kinetic energy of the ejecta, whcih is a fraction of the total kinetic energy of the original impactor. So, if we were to totally fragment a large asteroid and all pf the fragments would burn up in the atmosphere, then all of the kinetic energy of the impactor would end up in the atmosphere, making the most severe immediate effect of the impact much worse. Count Iblis (talk) 08:40, 6 February 2022 (UTC)

For a previous example, see Eltanin impact "...approximately 2.51 ± 0.07  million years ago... The asteroid was estimated to be about one to four km (0.6 to 2.5 mi) in diameter. No crater associated with the impact has been discovered. The impact likely evaporated 150 km3 (36 cu mi) of water, generating large tsunami waves hundreds of metres high". Alansplodge (talk) 10:22, 6 February 2022 (UTC)

See also If an Asteroid Hits the Ocean, Does It Make a Tsunami? (Probably Not). Alansplodge (talk) 10:26, 6 February 2022 (UTC)

A single large impact will create a different tsunami than multiple smaller simultaneous impacts a few hundred kilometres apart. With smaller fragments, there will be more waves, but less high and therefore more survivable. Ejecta radiating the energy back to the surface have been mentioned, but if fragments are small enough that they don't reach the surface, there won't be ejecta, so no efficient way to radiate the heat to the surface. Instead, the mesosphere (and for somewhat larger fragments stratosphere) will be heated, but heating on the surface will be limited. A 1 kilometre comet provides on the order of 10²⁰J of kinetic energy. Spread over about 10¹⁵kg of air in the mesosphere, that will heat the air by a hectokelvin. Somewhat larger impacts that blow ejecta into the stratosphere can cause a regional heating problem, but not global. Shockwaves reaching the surface from the stratosphere may be the main immediate problem. The main problem on a longer term is global cooling, but if we can arrange that individual impacts are small enough that ejecta stay mostly in the troposphere, is won't take too long before the dust has settled. So, breaking the impactor up before impact helps in some ways, even if the total energy stays the same. PiusImpavidus (talk) 12:07, 6 February 2022 (UTC)

This reminds me of the ridiculous scene in Independence Day where American fighter aircraft were trying to bring down a gigantic alien ship with puny air-to-air missiles. Clarityfiend (talk) 17:04, 6 February 2022 (UTC)

Like the puny artillery shell that sank the HMS Hood? --184.144.97.125 (talk) 06:07, 7 February 2022 (UTC)

Well, I'll admit it did take only one ramming to blow it up completely. Must have been designed by the same people who developed the Death Star. Clarityfiend (talk) 10:24, 7 February 2022 (UTC)

Aliens have been brought down by much punier weapons. Mitch Ames (talk) 01:24, 8 February 2022 (UTC)

The strategy in that movie was terrible. And the Death Star should've compartmentalized that trench with laser grids or force fields or brick walls or something. Sagittarian Milky Way (talk) 22:09, 7 February 2022 (UTC)

But we were shown in Rogue One that Galen Erso, coerced into working on the Death Star's design, secretly incorporated the weak spot, and in Star Wars that its crew didn't realise it was there until the attack was already in progress. {The poster formerly known as 87.81.230.195} 90.208.90.238 (talk) 16:31, 8 February 2022 (UTC)

February 6

Apollo 13

On Apollo 13, did the severe cold conditions (caused by the need to turn off all non-essential systems such as heating in order to conserve power) contribute to the premature failure of the CO2 scrubbers, as was the case on the Johnson Sea Link? 2601:646:8A81:6070:6C67:B2B6:D530:3F2A (talk) 10:20, 6 February 2022 (UTC)

My understanding is the scrubbers did not fail prematurely. The LEM filters were only designed to support two men for two days, and it instead had to support three men for four days, thus the need for adapting the filters from the command module. Do you have a source that says they failed prematurely? RudolfRed (talk) 22:32, 6 February 2022 (UTC)

That's what I was asking about -- was it only the increased load, or did the cold contribute as well? 69.181.91.208 (talk) 07:41, 7 February 2022 (UTC)

The lithium hydroxide in the canisters could only bind a limited amount of CO₂ and needed to be replaced regularly. At some point, the crew ran out of the limited supply of canisters that fit into the LM system. The scrubber itself did not fail, and while most LM systems were shut down, this would not have included the scrubber. I suppose (but cannot find definitive confirmation) that the scrubber may have included an internal heating system. But another issue is that the temperature-dependency properties of LiOH granules are rather different from those of the Baralyme used in the Johnson Sea Link scrubber. At a relative humidity in the air stream above 40%, LiOH is even reported to have a higher CO₂ absorption capacity at lower temperatures.^[6]  --Lambiam 09:55, 7 February 2022 (UTC)

So are you saying that the cold, damp conditions which prevailed in the LM actually stretched the scrubber's capacity longer? 69.181.91.208 (talk) 10:33, 7 February 2022 (UTC)

It would not have changed the capacity, which is only dependent on the stoichiometry of the reactants (which is to say, there are only so many formula units of LiOH available to react with CO₂), and temperature doesn't change that. The temperature would have affected only the kinetics of the reaction, which is to say the speed at which the reaction would have happened. AFAIK, the problem was not the kinetics, it is that they were literally out of usable LiOH in the LM scrubber system; which is why they needed to use the Command Module canisters. --Jayron32 13:39, 7 February 2022 (UTC)

February 9

Which was used first in nuclear bombs? Radium or Plutonium?

I couldn't find any specific information on nuclear bombs that answered this question.

"The world's first nuclear explosion occurred on July 16, 1945, when a plutonium implosion device was tested ..." Clarityfiend (talk) 07:48, 9 February 2022 (UTC)

I don't think radium has ever been used to create a nuclear bomb. Clarityfiend (talk) 07:50, 9 February 2022 (UTC)

Radium is not particularly fissile, which means it does not undergo a spontaneous fission reaction. Not all radioactive materials do so. Generally speaking, most fissile elements are isotopes of actinides with odd mass numbers. Radium is not an actinide, and has only 5 isotopes that have a halflife of more than a few seconds; of those only two have halflives measured in years; radium-228 and radium-226, both of which are even mass number. --Jayron32 12:10, 9 February 2022 (UTC)

Explosion/burning in chemical equation

In chemical equation are there any symbols / special characters to indicate that the reaction produces an explosion, vigorous burning or similar hazard? Googling only suggested that "gas explosion can be simplified as an one-step, exothermic chemical reaction: CH4 + 2O2 → CO2 + 2H2O + 886.2kJ/mol". Thanks. 212.180.235.46 (talk) 12:16, 9 February 2022 (UTC)