Wikipedia:Reference desk/Archives/Science/2021 September 18

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September 18

If KE generated is tiny due to an object's size, what's the purpose of avoiding it here?

In here it says: The amount of work energy needed to move a unit of electric charge from a reference point to the specific point in an electric field with negligible acceleration of the test charge to avoid producing kinetic energy or radiation by test charge.

If Kinetic energy is due to an object's motion. then an object (in this case, charge) tiny in size, so is necessary to avoid producing KE? Rizosome (talk) 02:54, 18 September 2021 (UTC)

While the mass of the electron is tiny, the velocity and thereby the kinetic energy that an electron can obtain by using an electric potential difference to move them – as is done in particle accelerators used in high-energy physics – can get very large. It can go up to several GeV, a billion times the work of moving an electron around in a low-voltage circuit. The avoidance clause is part of the definition, and is not a matter of a practical set-up for measuring potential.  --Lambiam 06:39, 18 September 2021 (UTC)

How exactly GeV getting avoided here? If it not a matter of a practical set-up, then why it is included in definition ? Rizosome (talk) 04:31, 19 September 2021 (UTC)

The definition (like any definition) describes an idealised situation where the charge is moved infinitely slowly from one point to another. Only in this idealised situation is the difference in potential equal to the work done on the charge. This makes for a clean precise definition, but describes a situation that in practice can only be realised approximately. In any real life situation, the energy balance is more complicated as it has to take into account the difference in kinetic energy and the amount of energy radiated away. Real life is messy, definitions are abstractions that reduce things to the essential aspects. A similar thing happens in thermodynamics, where theory demands that changes of the state of a system occur infinitely slowly so that the system is always in equilibrium. In reality systems always go through non-equilibrium states that are much harder to describe.

Having said that, it seems to me that for the lead sentence of a Wikipedia article this one is rather cluttered. It might be less confusing if that sentence did not mention KE and radiation; the definition could be made more precise further on in the article. --Wrongfilter (talk) 06:41, 19 September 2021 (UTC)

Would a Space probes named after people article be a good idea?

Let me know! 2405:4803:F190:6577:15C3:CAFB:2446:BE2E (talk) 06:41, 18 September 2021 (UTC)

What about using a category? See also WP:CLN and WP:SAL.  --Lambiam 07:08, 18 September 2021 (UTC)

Maybe only if there was also an article on space probes not named for people. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:53, 18 September 2021 (UTC)

More than 70 space probes have been launched, of which only about 10 were named after people. Cassini was named after Giovanni Cassini, Hubble was named after Edwin Hubble, and Kepler was named after Kepler. How many others do you know?  --Lambiam 20:58, 18 September 2021 (UTC)

I count around 25 in List of Solar System probes, though this includes "sub-probes" and some legendary/mythical/fictional "persons." {The poster formerly known as 87.81.230.195} 90.200.67.3 (talk) 05:22, 19 September 2021 (UTC)

That list contains many spacecraft that are still in the planning phase, such as Lucy. (Burning question: Do skeletons qualify as "people"?)  --Lambiam 07:05, 19 September 2021 (UTC)

At this point, Cassini, Kepler and Hubble are likewise "skeletons". ←Baseball Bugs ^{What's up, Doc?} carrots→ 18:39, 19 September 2021 (UTC)

Wouldn't a category suffice? Imagine Reason (talk) 22:21, 18 September 2021 (UTC)

No, we should not create such a category. Per Wikipedia:Categorization "A central concept used in categorizing articles is that of the defining characteristics of a subject of the article. A defining characteristic is one that reliable sources commonly and consistently define[1] the subject as having" This is not a subject that is frequently discussed about space probes. --Jayron32 16:06, 20 September 2021 (UTC)

It is actually fairly common that a news item or communiqué on a space mission such as a probe discusses who it is named for (if anyone):

• With its liftoff, University of Chicago Prof. Emeritus Eugene Parker became the first person to witness the launch of a namesake spacecraft. The Parker Space Probe is the first NASA mission named in honor of a living person.^[1]
• Gavin said the mission was named after Leonardo da Vinci for his Renaissance thinking that went beyond science and art.^[2]
• The Galileo probe, named for the Italian astronomer who discovered Jupiter's four largest moons, orbited the gas giant from 1995 to 2003.^[3]
• The spacecraft was named after John Young, NASA’s longest-serving astronaut, who was an integral part of missions to the moon and the space shuttle program.^[4]
• The names of Octavia Butler, a visionary award-winning writer, and Jakob van Zyl, a brilliant engineer and manager who helped send spacecraft across the solar system, are now part of the Perseverance rover’s mission.^[5]
• The probe was named Huygens, after the person who discovered Titan.^[6]

 --Lambiam 11:30, 21 September 2021 (UTC)

WP:Listcruft says: "In general, a "List of X" stand-alone list article should only be created if X itself is a legitimate encyclopedic topic that already has its own article. "--Shantavira|^{feed me} 08:26, 19 September 2021 (UTC)

Then we have lots of listcruft: List of Asian superheroes, List of Bangladeshi playback singers, List of Chileans of German descent, ...  --Lambiam 11:04, 21 September 2021 (UTC)

Finding examples of people doing the wrong thing is not an endorsement of that wrong thing, you know. --Jayron32 11:13, 21 September 2021 (UTC)

Neither a list nor a category, any more than List of ships named after people or Category:Towns named after presidents. It's not particularly significant or WP:CATDEFINING. Clarityfiend (talk) 03:45, 23 September 2021 (UTC)