Wikipedia:Reference desk/Archives/Science/2021 August 1

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is a transcluded archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

August 1

Why are there not more clusters at indoor PCR test sites?

I just went to work for a week and would like to get tested, but I don't want to go into a clinic, and then an enclosed room, where other patients, including infectious ones, also take off their masks and sneeze upon having a long swab inserted into their nose. Isn't that a sure way to get a lot of viral particles into the air? Why don't more people get sick from that? Imagine Reason (talk)

People probably would get sick from that, but that's why most people test themselves at home (I do a self test at home twice a week) and all the public testing sites I've seen are in the open air and socially distanced. It probably depends where you live, but in the UK, self-test kits are given away for free at rail stations, pharmacies, etc.--Shantavira|^{feed me} 14:24, 1 August 2021 (UTC)

In the UK, most PCR test sites are drive-through and you are not allowed out of your car. Walk-through sites have one-way systems so that you never come into contact with other members of the public and the testing bays are sanitized after each test. [1] The lateral flow tests that you can do at home are not as reliable, but are a lot less fuss and are the best bet if you don't actually have symptoms. [2] Alansplodge (talk) 22:44, 1 August 2021 (UTC)

That's nice. In the US most test sites are doctor's offices or urgent-care clinics. Completely indoors. Open spaces are harder to come by. I guess I should look for a mobile testing site then. I've gotten the vaccine so I don't know how good antigen tests would be. Also, home test kits have high error rates. Imagine Reason (talk) 23:16, 1 August 2021 (UTC)

Indeed. Over here, the advice is to take a lateral flow test at home - if it's positive - book a PCR test to double-check. Alansplodge (talk) 18:09, 2 August 2021 (UTC)

Conversion of kinetic energy of a superfluid

Is it possible to convert the indefinite kinetic energy of a superfluid (e.g., after being stirred up) into electricity, similar to hydroelectric power plant? Or would the costs of maintaining the superfluidity be too high? 212.180.235.46 (talk) 14:51, 1 August 2021 (UTC)

Superfluids don't have indefinite kinetic energy. They have no friction so they don't lose any kinetic energy you give them. If you extract that energy, they will slow down like anything else would. --Jayron32 11:59, 2 August 2021 (UTC)

Would a oloid or sphericon planet be able to exist or if magically appeared somewhere be able to continue with its shape?

Would a oloid or sphericon planet be able to exist or if magically appeared somewhere be able to continue with its shape?

I am asking about those 2 specific things because they are developable surfaces.2804:7F2:691:D026:F49A:3097:3AC3:3524 (talk) 15:43, 1 August 2021 (UTC)

If the planet was small and rigid, I suppose it could hold its shape, just like the random chunks of rock in the asteroid belt hold their own shapes. Mars's moons (which are quite small) are also not very spherical. What we normally call planets are big enough to have substantial surface gravity. So they end up close to spherical or (because of rotation) oblate, to minimize the gravitational potential energy in the mass distribution. Even still, they will have surface features like mountains. The Earth itself is slightly pear-shaped: see geoid. 2601:648:8202:350:0:0:0:2B99 (talk) 19:11, 1 August 2021 (UTC)

A planet is by definition massive enough to be rounded by its own gravity so your objects wouldn't be called planets. PrimeHunter (talk) 23:44, 1 August 2021 (UTC)

The largest nonspherical object in the solar system is Iapetus, with a diameter of approximately 1490 km (since it's nonspherical, it doesn't really have a well defined diameter). The next larger objects, Oberon (diameter 1522 km), Rhea (diameter 1530 km), and Titania (diameter 1576 km), are only slightly larger but are in hydrostatic equilibrium and are therefore close to spherical. So about 1500 km seems to be the limit for a nonspherical body, at least one made from materials common in our solar system. CodeTalker (talk) 05:20, 2 August 2021 (UTC)

"A planet is by definition massive enough to be rounded by its own gravity so your objects wouldn't be called planets." Didnt knew that, so I obviously wasn't talking about planets and the answer would as the answer would be a no to everything that is not already rounded before you take its own gravity into account. So assume I am talking about what I meant (whateaver it the word for that) and not what I said (a planet).2804:7F2:59E:935F:79C5:98C9:D50D:4D98 (talk) 00:39, 5 August 2021 (UTC)

Well, you're going to have to redefine the parameters of your question a bit, since you now have no operative noun/subject at work here defining the topic of inquiry. Can physical bodies exist roughly in the shape of an oloid or sphericon? Sure: we can empirically validate that assumption easily enough. If you mean, can they exist at a given scale (that is below the threshold at witch the object's mass will precludes anything but a roughly spherical shape), what scale are we talking about? The answer to your question depends heavily upon the physical characteristics of the body in question, principally its mass and composition. SnowRise ^{let's rap} 22:45, 5 August 2021 (UTC)