Wikipedia:Reference desk/Archives/Science/2021 March 28

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March 28

Electrolytic conductivity

Is it true that a saturated aqueous solution of sodium alum has a higher electrolytic conductivity at room temperature than any other aqueous salt solution? 2601:646:8A01:B180:C950:DB2D:18A5:263 (talk) 07:49, 28 March 2021 (UTC)

Have you considered nitric acid? Graeme Bartlett (talk) 11:27, 28 March 2021 (UTC)

Ummmm.... the question is about salt solutions. An acid is not a salt.--Khajidha (talk) 13:17, 28 March 2021(UTC) Apparently the term "salt" can cover the solids of acids and bases. Didn't know that. --Khajidha (talk) 13:23, 28 March 2021 (UTC)

Solid acids and bases do not conduct electricity, and my question was specifically about electrical conductivity -- also, they are not salt compounds! (And also, my question was specifically about conductance in aqueous solution -- and an aqueous solution of acid does not fall under any definition of salt!) 2601:646:8A01:B180:7122:A592:B23F:43C5 (talk) 05:57, 29 March 2021 (UTC)

I was asking you to consider nitric acid in aqueous solution. I know it has very high conductivity, but I do not know the value, or if it is the highest. Graeme Bartlett (talk) 22:01, 30 March 2021 (UTC)

I was asking specifically about salt solutions -- not acid or alkali solutions! 2601:646:8A01:B180:684B:6115:7524:A95C (talk) 03:35, 1 April 2021 (UTC)

• The way to answer that question (unless you can plug it in a search engine and have your prayer granted) is to list the saturation concentration of all possible salts in water at RT, then for constituent ions look at the molar conductivity, and multiply the two. For the latter there is a table at Conductivity_(electrolytic)#Strong_electrolytes. For the former, sodium alum does seem to have a pretty fantastic solubility in water, so it seems plausible to me that it beats other salts.

If you already knew that, there is a good chance you are the most knowledgeable here to answer your own question... Tigraan^{Click here to contact me} 08:13, 29 March 2021 (UTC)

I am about 90% sure of that based on my own calculations (I calculated the saturation concentration and molar conductivity of sodium alum, the 2 other alums (potassium and ammonium) and a couple of other salts like calcium chloride, magnesium chloride and magnesium sulfate, and none of the others were even close), but I need to make sure! 2601:646:8A01:B180:B577:3901:2F94:5DF (talk) 12:50, 29 March 2021 (UTC)

E = m·c²

If I'm getting it right, although scientific folklore has always been attributing it to him, Einstein actually did not coin that famous equation in this exact form, did he? If so, who then did use that notation first, in reality? I was unable to find sufficient evidence on that issue. Thanks in advance for any assistance.--Hildeoc (talk) 17:47, 28 March 2021 (UTC)

What Einstein wrote in 1905 (in German) was that if a body radiates energy in the amount L, its mass diminishes by L/V². I don't know who recast the equation in its present form. --184.147.181.129 (talk) 21:11, 28 March 2021 (UTC)

It is said that his teacher created the equation, and Einstein just made it famous. I don't have any proof of this but that is what I read. Prairie Astronomer ^Talk 21:14, 28 March 2021 (UTC)

You ought to research statements such as this before putting them on the reference desk. You may be thinking of Friedrich Hasenöhrl. --Wrongfilter (talk)

It seems that Einstein was the first to write down the formula in precisely the form $E=mc^{2}.$^[1]  --Lambiam 22:09, 28 March 2021 (UTC)

Einstein used that form in 1907 ([2], p.287, with μ instead of m). Abraham Pais also mentions a paper by Planck from 1906/07, but I haven't got time right now to check in which form he wrote down the equation. --Wrongfilter (talk) 08:59, 29 March 2021 (UTC)

Planck writes it down as eq.48 on page 564 of Sitzungsberichte der preußischen Akademie der Wissenschaften, 13 June 1907 [3]. Not the exact form, though (because the popular form is a simplified version that misses much of the complexity). --Wrongfilter (talk) 10:19, 29 March 2021 (UTC)

@Wrongfilter: Sorry, but which exact equation on that page are you referring to?--Hildeoc (talk) 20:10, 4 April 2021 (UTC)

$M=(E_{0}+pV)/c^{2}$. I haven't actually tried to read the paper and don't pretend to fully understand the notation, but this is obviously very close to the pop equation. His mass M is independent of velocity, as it should be, $E_{0}$ is the internal energy, p pressure, V volume, and what he calls Wärmefunktion R is, I believe, enthalpy. My thermodynamics is rather rusty, sadly, but as far as I understand he makes the important point that relativistic mass arises from internal degrees of freedom, not from centre-of-mass motion. --Wrongfilter (talk) 20:42, 4 April 2021 (UTC)

Suez Canal blockage

Probably a silly question, but why can't they just get another ship of similar size (maybe one that's going to be decommissioned soon anyway) and have it full steam ahead and shunt the Ever Given out of the way? --Iloveparrots (talk) 18:11, 28 March 2021 (UTC)

Then you'd have two ships blocking the canal. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:32, 28 March 2021 (UTC)

That sounds like a really great way to make the situation far worse by creating lots of debris, losing a ton of containers that will end up spilling their contents (as well as sinking, making clearing the canal that much harder), leaking fuel and oil, and probably dozens of other problems. All the while, it wouldn't actually clear the canal. --OuroborosCobra (talk) 22:48, 28 March 2021 (UTC)

So, replacing an incident with a disaster? enjoyer|talk 03:44, 29 March 2021 (UTC)

I was thinking of using another ship to give it a push at one end or the other and get it pointing in the right direction, not just ramming the thing and seeing what happens next, FWIW. --Iloveparrots (talk) 09:04, 29 March 2021 (UTC)

• I guess the answers above are correct, but I have no way to know they are. How about providing some refs? Tigraan^{Click here to contact me} 08:04, 29 March 2021 (UTC)

  @Tigraan: There's not going to be references refuting every bad idea. The human capacity for bad ideas is far greater than the solid scientific studies which have been done to refute them. There's a thousand really bad ideas we could all come up with for freeing the ship. It is unrealistic to expect that there already exists, out there in the world, references we could come up with to refute them. --Jayron32 11:55, 29 March 2021 (UTC)

  I get that, but maybe ramming is actually the standard procedure and very specific exceptions apply in this precise case. Before you tell me that is ridiculous: how do you know that? (Unless you have special expertise to say "I reckon that (...)" with some degree of certainty much above what you would hear at the proverbial pub, the only correct answer is "they know what they are doing and they have not done it".)

I do not expect a randomized controlled trial of ship-ramming either; a joking footnote in a book from an expert in a tangentially related topic might be enough. Also, I expect there are some refs about what is to be done when a ship is stuck in a waterway (I suppose for instance Locks have procedures in place for similar accidents). Maybe they are not applicable, but if I were trying to answer the question I would search them first before typing out my thoughts. Tigraan^{Click here to contact me} 13:33, 29 March 2021 (UTC)

Strong tug boats could only do the job after more than 20,000 tonnes of send had been dredged around the bow of the ship.^[4] The other side was stuck on a rocky bottom. So it was really stuck, like, you know, stuck. The ship itself is reported to have a 224,000-tonne mass.^[5] You’d need to ram it with a ship of a similar mass moving at top speed to make it even shift. Ships are simply not designed and built to withstand such midship ramming.  --Lambiam 11:15, 29 March 2021 (UTC)

I didn't mean a midship ramming. Was thinking of using a ship to give it a push at one end or the other. --Iloveparrots (talk) 11:50, 29 March 2021 (UTC)

That's called a tug(boat)! there are lots of them already trying to move the Ever Given. They are designed to be able to apply high force, as described at Tugboat#Propulsion. The issue is how to do that without over-stressing the hull of the stranded ship. According to today's news [6], using tugs has already been partially successful, thankfully. Mike Turnbull (talk) 12:02, 29 March 2021 (UTC)

You are aware until recently it was like this right? [7] Trying to push or pull it at either end with a large ship would require said large ship to get quite close to the edge. This seems like a disaster waiting to happen before you even hit the Ever Given.As Michael D. Turnbull said, there are already specialised vehicles designed for that sort of thing, i.e. tugboats which were used. Nil Einne (talk) 15:13, 29 March 2021 (UTC)

Besides all the above good answers, it's worth considering that finding these other ships and getting them into place would probably have taken many weeks. Meanwhile Ever Given is now on the move after less than 1 week. It's likely even the option of removing containers would have made a substanial difference before you could try this idea. Nil Einne (talk) 15:13, 29 March 2021 (UTC)

Sister ship Ever Greet was en route to the canal when it was diverted to the Cape of Good Hope route.^[8] Judging from the angles, its position at the time was probably in the Arabian Sea, about a week away from the locus of blockage.  --Lambiam 10:18, 30 March 2021 (UTC)

What interests me is that the "Ever Given" has the word "EVERGREEN" quite clearly painted on its side. 91.125.11.49 (talk) 12:00, 1 April 2021 (UTC)

That's because it's owned by these guys. If you are that interested they can probably send you a picture. Martinevans123 (talk) 12:17, 1 April 2021 (UTC)