Wikipedia:Reference desk/Archives/Science/2021 September 10

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September 10

Why did NASA planned JWST deployment for 3 weeks process?

Here it says: Once in position, JWST will go through the process of deploying its sunshade, mirror, and arm, which will take around three weeks.

Why three weeks instead of deployment right after entering into Halo orbit? Rizosome (talk) 00:22, 10 September 2021 (UTC)

It's not saying that they're waiting 3 weeks and then they begin the deployment; it's saying the deployment takes 3 weeks to complete. The deployment process begins a few hours after launch, long before the telescope reaches its final halo orbit, as the diagram shows in the article that you linked to. Part of the time required for the process is apparently waiting for the telescope to cool down after the sun shade is deployed. There's a more detailed timeline here. CodeTalker (talk) 01:04, 10 September 2021 (UTC)

Apollo failure plan

If Armstrong & Aldrin (or any pair of their successors) could not leave the Moon, I guess they'd carry on doing whatever science they could until they ran out of air or water, and then open their helmets to vacuum; but has anyone in a position to know said anything publicly? —Tamfang (talk) 00:37, 10 September 2021 (UTC)

I think the contingency plan for Apollo 11 was to close down communications. The scientific part of the mission was extremely limited, after quickly deploying a seismometer and a laser ranger and collecting a few rocks to be analyzed back on Earth, there was nothing left to do for Armstrong and Aldrin in the way of science.  --Lambiam 08:23, 10 September 2021 (UTC)

Plenty of hits if you google "apollo failure plan". I don't know how much is accurate. This https://www.space.com/if-apollo-11-astronauts-died-nixon-contingency-speech.html mentions a contingency speech by Nixon; this was also mentioned in an Apollo documentary I saw recently on the Smithsonian TV channel. Thankfully, the Apollo missions were successful. I remember in the Australian news, speculation that Luna 15 might have been an emergency escape plan. --TrogWoolley (talk) 09:48, 10 September 2021 (UTC)

Thanks to MIT, we can hear Nixon deliver that speech. —Tamfang (talk) 01:01, 14 September 2021 (UTC)

I'm not sure they'd need to expose themselves to vacuum as both their spacesuits and the lander itself both used recycler technology to maintain a breatable atmosphere. So if the Oxygen supply ran out before the scrubber the astronauts would have lost conciousness and died due to hypoxia without the unpleasant sensation associated with asphyxiation caused by hypercapnia. 2A01:E34:EF5E:4640:9CF5:EEC0:F336:157F (talk) 13:49, 10 September 2021 (UTC)

They came very close to being stuck on the Moon. Count Iblis (talk) 17:07, 10 September 2021 (UTC)

I think they had backup methods. I think they could simply turn some valves by hand to start the engine. Bubba73 ^{You talkin' to me?} 04:05, 12 September 2021 (UTC)

If a freak meteorite destroyed the CM at touchdown how far from the landing site could they get, if they decided on a whim to make the distance record as hard to break as possible? Is the rover faster with one man or two? (for traction or balance or something) Could the throttle control be tied, taped or jammed in the "on" position? Sagittarian Milky Way (talk) 21:36, 10 September 2021 (UTC)

Perpetual motion of water

Greetings!

I found this video of perpetual motion (here) in which 4 watering cans are situated so that siphoning water through the spout of one can into the filling hole of another permits one to link a a number of cans so that they fill one another without any intervention and will continue to do so ad infinitum unless disturbed.

Why can't we harness the falling water with a water wheel and draw power from such a system? If we did, it seems we'd be drawing power from a perpetual motion machine, which seems to be a violation of the first law of thermodynamics.

Thanks!

DRosenbach ^{(Talk | Contribs)} 13:00, 10 September 2021 (UTC)

The first law of thermodynamics tells us this cannot be a source of perpetual motion. There is some "trick" involved as can be seen in the video - notice that when the operator sets the water in the first 3 watering cans into motion, he then steps backwards and stops adding water to the 1st can but the 1st can continues to pour water into the 2nd can, even though water hasn't started flowing from the 4th can into the 1st can! Notice that after the operator first stops adding water to the 1st can the water level in that can remains completely full even though water is pouring out of the 1st can into the 2nd. Some sort of trick must be involved because how could water be flowing from the 1st can into the 2nd when no water is yet flowing into the 1st from the 4th? The trick may be that there is a cut in the filming which is not detectable to anyone watching the video, but during the cut some other source of water (not visible to the viewer) is connected to the 1st can, and then filming resumes. Dolphin (t) 13:24, 10 September 2021 (UTC)

Funny, when I overfill a watering can, the extra water just spills out of the filling hole. Water only starts to come out of the spout if I tilt the can. The person in the video seems to be playing with a different physics ruleset. --Amble (talk) 22:37, 10 September 2021 (UTC)

Any holes below your filling hole? Sagittarian Milky Way (talk) 01:16, 11 September 2021 (UTC)

No, which is why pouring water in the filling hole of a real watering can sitting flat on the ground doesn’t cause water to come gushing out of the higher spout, as it appears to do in the video. —Amble (talk) 02:21, 11 September 2021 (UTC)

I wonder if there's a hosepipe hidden inside one of the watering cans feeding out the spout. Sort of like Brian Wansink's (supposed) bottomless soup bowl experiment. Blythwood (talk) 03:48, 11 September 2021 (UTC)

I think it was probably done with video editing. But if not, maybe a small submersible pump hidden inside the can? --Amble (talk) 22:13, 11 September 2021 (UTC)

Are short codons possible?

I just can't seem to find any references for this. My question is relatively simple. Is it possible for a codon to consist of less than three bases? Earl of Arundel (talk) 13:29, 10 September 2021 (UTC)

I'm not sure I understand your meaning. Do you mean "Could someone imagine a fictional biological system that used two- or one-base codons" or do you mean "are there examples of exotic forms of life that use two- or one-base codons that we know about"? --Jayron32 13:33, 10 September 2021 (UTC)

Precisely, the latter. And moreover what might happen if the DNA/RNA "machinery" actually did encounter a shorter snippet at the end of a chain? Eg. Would it destroy the strand, ignore the snippet, make an amino acid anyway, just get confused? Earl of Arundel (talk) 13:50, 10 September 2021 (UTC)

Our Genetic code article has a section on variants of the code, but the variants mostly involve changing the meaning of a small number of 3-base codons. The article says Despite these differences, all known naturally occurring codes are very similar. The coding mechanism is the same for all organisms: three-base codons, tRNA, ribosomes, single direction reading and translating single codons into single amino acids. (emphasis added) CodeTalker (talk) 20:12, 10 September 2021 (UTC)

Of course it isn't much of a stretch to imagine some rare cases where physical damage to a strand of DNA (due to radiation or what have you) could however cause that sort of thing to happen. Surely the cells have some way of dealing with those kinds of errors. Earl of Arundel (talk) 15:17, 11 September 2021 (UTC)

Not very good ways; see frameshift mutation, Earl of Arundel. HLHJ (talk) 20:32, 12 September 2021 (UTC)

I see. So in some extreme cases it really can cause serious problems. Well I guess that answers my second question! Earl of Arundel (talk) 15:22, 13 September 2021 (UTC)

Our Codon degeneracy article notes the important point that the number of codons sets a limit on the number of different amino acids that can be encoded. Going the other way (and drifting off the original specific question), doi:10.1093/nar/gnj003 demonstrates development of four-base codons. DMacks (talk) 15:26, 11 September 2021 (UTC)

Okay, so cells are often able to mitigate for these irregular chains, but mutations sometimes do occur instead. Well that makes sense. And thank you for the links! Earl of Arundel (talk) 19:45, 11 September 2021 (UTC)

What if they'd used respirators?

[1] Imagine Reason (talk) 14:40, 10 September 2021 (UTC)

Is there a question? --OuroborosCobra (talk) 17:54, 10 September 2021 (UTC)

Inaccessible link. --CiaPan (talk) 20:54, 10 September 2021 (UTC)

9/11 Survivors Are Still Getting Sick Decades Later: ‘Am I Next?’ It's an interesting question, but is either trivial or calls for speculation, which we won't do here. Certainly hazmat suits would have resulted in fewer people being exposed to toxins and thus fewer long-term problems. --jpgordon^{𝄢𝄆𝄐𝄇} 22:26, 10 September 2021 (UTC)

I'd have thought that there'd be a lot of science done now on the effects of building destructions on air quality and the usefulness of filtering masks in such air. Imagine Reason (talk) 20:49, 11 September 2021 (UTC)

Perhaps it doesn't require much research to conclude that breathing building debris is bad for you. This article from the American Lung Association sums up:

1) Most people who had intense early exposure did sustain around a 10 percent reduction in lung function and this reduction was sustained after more than a decade. 2) Some of the effects could have been reduced with widespread use of personal protective respiratory equipment. 3) Persons most affected generally had pre-existing lung problems. Smokers were harder hit than non-smokers.

Alansplodge (talk) 17:15, 12 September 2021 (UTC)

See respirator. Emergency responders often did use elastomeric respirators. Filtering out particulates can be done with a mechanical filter respirator (or, less efficiently, with almost any type of cloth mask), but filtering out gaseous toxins requires different types of chemical cartridges for different chemicals. Since the NYT does not make it clear what it is that is causing the symptoms, and OuroborosCobra did not specify the type of respirator, it's not possible to predict the exact effects. The Lung Association article mentions alkaline dust and silica dust (which can be kept out with a mechanical filter, since they're solid dust) and acrolein (which can be kept out with a mechanical filter if it's in liquid droplets, but it's fairly volatile, and so some of it will have been a gas that can go through a mechanical filter). But there were obviously lots of other chemicals, depending on when you were where. HLHJ (talk) 20:29, 12 September 2021 (UTC)

Why would I have specified anything, including respirator type? I responded to the fact that the original poster had not actually posed a question in starting this discussion. --OuroborosCobra (talk) 14:55, 13 September 2021 (UTC)

Apologies, OuroborosCobra; I meant to ping Imagine Reason, the OP, and messed up. Obviously this is because you have a boring name and not a vivid, evocative one like four random letters. HLHJ (talk) 03:56, 15 September 2021 (UTC)

Do vaccine booster shots need to be same as original vaccine?

Not a request for medical advice, but rather a general question. When a vaccine booster shot is given, does it need to be the same as the original vaccine? COVID vaccine booster shot is what brings this to mind (if someone had the Pfiser vaccine originally, can they get Moderna as the booster?) but also curious about other vaccines that require booster shots. RudolfRed (talk) 20:12, 10 September 2021 (UTC)

By "booster" I mean, for example, a third shot of a two-shot series given some time (6+ months) after the original. RudolfRed (talk) 20:22, 10 September 2021 (UTC)

See Mix-and-match COVID vaccines trigger potent immune response (19 May 2021). Alansplodge (talk) 21:58, 10 September 2021 (UTC)

As to COVID vaccines, the three vaccines principally used here in Canada fall into two major types: the Pfizer and Moderna vaccines are mRNA vaccines while AstraZeneca's is a viral vector vaccine. The Advisory Committee on Immunization recommended in June that "When the first dose in a COVID-19 vaccine series is an mRNA vaccine, the same mRNA vaccine product should be offered for the subsequent dose if readily available. When the same mRNA vaccine product is not readily available, or is unknown, another mRNA COVID-19 vaccine product recommended in that age group can be considered interchangeable and should be offered to complete the series"; and that "When the first dose in a COVID-19 vaccine series is the AstraZeneca/COVISHIELD vaccine, either the AstraZeneca/COVISHIELD vaccine or an mRNA vaccine product may be offered for the subsequent dose to complete the series, however an mRNA vaccine product is preferred as a subsequent dose due to emerging evidence including the possibility of better immune response...". As far as I know this advice hasn't changed. --184.144.99.72 (talk) 04:29, 11 September 2021 (UTC)

As a majority of COVID vaccines is based on the full length spike protein (or even on the whole virus) they are probably interchangeable. Ruslik_Zero 20:16, 11 September 2021 (UTC)

Thanks, everyone, for the information and replies. RudolfRed (talk) 21:36, 11 September 2021 (UTC)