Wikipedia:Reference desk/Science#Putting a very small satellite into orbit in space

I read in the Vatican News that the death of Pope Francis 'was confirmed through electrocardiographic thanatography.' Wiktionary says 'thanatography' means 'An account, usually written, of the death of a person.' So the death of the Pope was confirmed through an electrocardiographic account of his death. Is this more than a complicated way to say that an ECG could not detect a heartbeat? The news also said 'The cause of Pope Francis' death has been identified as a stroke, followed by a coma and irreversible cardiocirculatory collapse.' How can the doctors know the collapse was irreversible. Does this mean the doctors tried to revive him? Thank you. Hevesli (talk) 08:07, 23 April 2025 (UTC)

:Earlier in his hospitalization it was mentioned that his doctors were considering not resuscitating him. Since this runs afoul of Catholic teaching against euthanasia, they may have couched it in terms that avoid saying, "we let him die". Abductive (reasoning) 11:59, 23 April 2025 (UTC)

::What makes you think that is the same as euthenasia? It can be quite an inhumane thing to use too much effort in keeping somebody 'alive'. My understanding is that the Catholic Church is not opposed to DNR notices. NadVolum (talk) 18:47, 23 April 2025 (UTC)

:::I dunno, thanatography, euthanasia; DNR is kinda a gray area; sure, heroics aren't always good; this is the pope so best not to have any complicated discussions even if the church isn't against DNR orders. Abductive (reasoning) 10:30, 24 April 2025 (UTC)

:::There have been 266 catholic popes most of whom died in office so this old tale could have been about any of them. When the holy father's health worsened precariously the Vatican hospital doctors declared that they could do no more and that his life's End was imminent. Fortunately the Vatican has great financial resources and a second opinion was ordered from the highest reputed, and therefore most expensive, medical specialist. Alone with the pope the specialist gently told the sick man that he also could do nothing to save him. The old pope managed to croak a few words. "I am ready to die. Bring my lawyer to my bedside." The specialist asked "I know why I am here but why do you want a lawyer also?" Pope: "Just as my Saviour I shall die between two thieves." Philvoids (talk) 10:36, 24 April 2025 (UTC)

= April 25 =

I always imagined that (fixed) velocity was relative but acceleration (change in velocity) absolute, and that rotation was absolute being just a case of acceleration, i.e. the parts of a rotating body are constantly changing (direction of) velocity, i.e. accelerating in the general sense. However the article Absolute rotation does not even mention the word acceleration, as far as I can see. Shouldn't it? Isn't this an "easy" explanation? 2A00:23C8:7B20:CC01:CC87:EAA5:618F:BEF8 (talk) 20:45, 25 April 2025 (UTC)

:It is true that the article Absolute rotation does not contain the word "acceleration". It also names Newton whose laws represent classical physics and states "From the necessary centrifugal force, one can determine one's speed of rotation;..." without explaining this use of Newton's 2nd law of motion. I agree that the article might be made more accessible if it did not assume that the general reader already knows classical Newtonian mechanics. Such improvement might be done by adding explanation as you suggest or by appropriate links to other articles. The place to propose your changes is Talk:Absolute_rotation. Philvoids (talk) 13:05, 26 April 2025 (UTC)

:Newtonian mechanic's accelerations are relative though, for the Galilean transformations preserve distances and time intervals, but, like the Lorentz transformations, these transformations do not preserve velocities and all accelerations. For example, consider a shipmate waving hello from a ship's bow to a beachcomber as their ship sails along the coastline and then the mate sprints to the ship's stern to wave goodbye. With respect to the ship's deck our mate first accelerated then decelerated, but from the stationary shore's reference frame they first decelerated to a slower speed and then accelerated (unless the ship slowed too) to match the ship's speed again. In short, all motion depends on reference frames, and this was true even in Newton's time when physicists speculated that motion could also be intrinsic and absolute, i.e. with respect to an absolute ether (e.g. Aether theories). Modocc (talk) 22:28, 30 April 2025 (UTC)

File:Linear_momentum_conservation_2d.svg

I found a technique to solve conservation of linear momentum problems by drawing a diagram, as illustrated.

If the collision were instead elastic i.e. kinetic energy is conserved, is it possible to find all possible solutions graphically? Thanks, cmɢʟee⎆τaʟκ 22:17, 25 April 2025 (UTC)

:I'm not sure if there is a graphical approach to solving for area (ie v^2), I've never seen one. Greglocock (talk) 00:30, 26 April 2025 (UTC)

:File:Thales'_Theorem_Simple.svg

:Can one conclude that if the two balls had the same mass m, one could use Thales's theorem to state that if AC is the resultant vector in the diagram, the constituent vectors are AB and BC for any B on the circle, so that |AB|² + |BC|² = |AC|² to conserve kinetic energy i.e. ½mv₁² + ½mv₂² = constant? Cheers, cmɢʟee⎆τaʟκ 12:12, 28 April 2025 (UTC)

::If the balls have the same mass, then isn't the solution quite simple for perfectly elastic collision? Velocity components along the line between the two centres swapped between the balls, and perpendicular components unchanged. (Someone please correct if this is wrong!) With balls of different mass, the solution algebraically most probably involves some multiplications, additions and divisions, all of which can in theory be done "graphically" using ruler and compass, but of course it could get very messy in practice. A neat graphical solution is a bigger ask. 2A00:23C8:7B20:CC01:DCDC:39AB:FED1:9A1B (talk) 18:27, 28 April 2025 (UTC)

:::You're right, thanks. I hadn't considered it. cmɢʟee⎆τaʟκ 10:51, 29 April 2025 (UTC)

{{clear}}

= April 28 =

File:Yellow tulips with red flames.jpg

Anyone know what this is? It's quite striking. It seems to be a tulip of some kind, but I don't know what. Google says it's a Tulipa hungarica, but it doesn't look all that similar to my untrained eye. Would like to identify it correctly on Commons if possible. NinjaRobotPirate (talk) 02:44, 28 April 2025 (UTC)

:When I Google "yellow tulip with red flames" I'm told it's Tulip Olympic Flame, which does appear the same. Shantavira|^{feed me} 08:37, 28 April 2025 (UTC)

:It's a tulip and not a Tulipa hungarica, at least not a pure one; note the rounded tepals and the red flames. There are many species of tulips, many hybrids and countless cultivars, some of which managed to escape into the wild. To identify a particular species or, in case of a hybrid, combination of species, one may need a genetic study. I suspect this is some cultivar; one possibility has been mentioned above.

:The flames may be from genetics (and usually are in cultivars), but can also be caused by a viral infection. PiusImpavidus (talk) 09:12, 28 April 2025 (UTC)

:The same tulip is available at J Parkers in the UK, they call it Tulip 'Flaming Sun', https://www.jparkers.co.uk/tulip-flaming-sun-1112cm-collection-1 Stanleykswong (talk) 05:30, 30 April 2025 (UTC)

I just spent 15 minutes looking at tulip images. To me, your photo is of the "Fire Wing Tulip" which is thought to be part of the Tulipa Darwin Hybrid Group or Tulipa Triumph Group (both of those have categories on Commons). Olympic Flame is also part of the Tulipa Darwin Hybrid, but your tulips don't look like Olympic Flame. Viriditas (talk) 02:28, 30 April 2025 (UTC)

: Interesting. Fire Wing does look similar. NinjaRobotPirate (talk) 00:10, 1 May 2025 (UTC)

::I was surprised to learn that Fire Wing is new, and was only recently created in the early 2000s. Some of the Fire Wing images are different and don't look like yours, while others do, so I think the jury is still out. Given that Olympic Flame and Fire Wing may both trace to the Tulipa Darwin Hybrid Group, I wonder if that is something you can go on to look further. The last time I grew tulips was in 1996. I bought a huge bag of bulbs from Costco, who had at that time received a direct shipment from the Netherlands. Viriditas (talk) 00:14, 1 May 2025 (UTC)

::: These tulips were most likely planted by a professional who had access to rare cultivars, which unfortunately does complicate the issue. He's no longer available, but there are a lot of pretty flowers in the area. NinjaRobotPirate (talk) 00:26, 1 May 2025 (UTC)

:"Fire Wings tulip" is similar in appearance to "Flaming Sun tulip", but has more pointed petals. Stanleykswong (talk) 07:05, 1 May 2025 (UTC)

= April 30 =

What was the maximum speed of one of these "little sheep" while pulling a train of 400 tons? I was only able to find the maximum speed when travelling light (50-55 km/h) -- by how much would a 400-ton train (such as a typical armored train from that era) slow it down? 2601:646:8082:BA0:D86C:E2FE:4764:1AB0 (talk) 03:19, 30 April 2025 (UTC)

:The Russian Wikipedia gives the traction as 8700—9500 kgf. At which speed does rolling resistance + drag of a typical 400-ton train equal about 9000 kgf? (Are these metric tons?) I bet this is an order of magnitude higher than 50–55 km/h, so my best guess is that it takes 15 to 30 minutes for the train to come up to maximum speed, but that speed would still be in the 50–55 km/h range.  ​‑‑Lambiam 08:47, 30 April 2025 (UTC)

:At 1.85 square metres of grate area and a somewhat realistic efficiency, I guesstimate that its sustained power is no more than about 100 to 150 kilowatts. With the rolling resistance of a 400 tonne train, that's maybe 40 km/h. But with the cut-off wide open for more traction, efficiency drops. Could be interesting to look into, but I've no time right now. PiusImpavidus (talk) 16:19, 30 April 2025 (UTC)

::The Russian Wikipedia gives the power as 550—720 hp, which amounts to about 400—530 kW.  ​‑‑Lambiam 22:27, 30 April 2025 (UTC)

:::It was a very rough guesstimate. In any case, it serves to demonstrate that it's most likely limited by sustained power, not by traction. At 85 kN traction, 400 kW power is reached at only 17 km/h.

:::All versions appear to have had the same firebox, so differences in sustained power can only be caused by differences in efficiency. And the slower you go, the more traction you need to reach maximum power, so a later cut-off, leading to less efficiency and less power. The 400 to 530 kW figure may have been measured using a train of less than 400 tonnes, giving more power. Although not too light a train, as power would normally mean drawbar power, which gets less if the train is too light and a larger fraction of the power is wasted on moving the loco itself.

:::To get an accurate answer, we need detailed performance data on these locomotives, and considering that steam locomotive design was often more art than engineering, such data may never have been collected. Absent that, any number between 30 and 45 km/h sounds totally believable to me. PiusImpavidus (talk) 11:00, 1 May 2025 (UTC)

= May 1 =

I know it's been done occasionally (there are photos if you Google it), but why is it that rhinos are generally considered unsuitable to use as mounts, while elephants have been ridden for centuries? 146.200.107.90 (talk) 00:53, 1 May 2025 (UTC)

:Indian elephants are domesticated. African elephants, as well as rhinos and hippos, are wild and dangerous. (Aside: There's more than one plural for rhinoceros, but rhinoceri is not on the list.[https://www.etymonline.com/search?q=rhinoceros]) ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:04, 1 May 2025 (UTC)

::Similarly, humans have been riding horses for about 6000 years. Humans do not regularly ride zebras despite their similarity in form and genetics to horses. Zebras cannot be domesticated despite many attempts. Some have been tamed enough to pull carts but not to ride. 02:16, 1 May 2025 (UTC) -- Cullen328

:::I saw something about zebras not too long ago. I think it said that in addition to being wild and ornery, their backs are not strong enough to support riders. As I recall, when they did a movie about Sheena or some such, the "zebra" she rode on was actually a regular horse painted with zebra stripes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:29, 1 May 2025 (UTC)

::::Maybe it's because it's difficult to get glasses or contact lenses for rhinos. I have never seen one in an optician's office, although I need a new prescription so I might have missed them. Sean.hoyland (talk) 03:53, 1 May 2025 (UTC)

:::::Especially if they're suffering from a rhinovirus. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:19, 1 May 2025 (UTC)

:::Wild horses aren't very suited to riding either. People invented chariots before cavalry, not only because it took a while to develop proper saddles and stirrups, but also to breed the right horse breeds. PiusImpavidus (talk) 12:02, 1 May 2025 (UTC)

:::Fwiw, Google images has several photos of people riding zebras. So it can be done. Occasionally, I guess. 146.200.107.90 (talk) 13:15, 1 May 2025 (UTC)

::::Zebra says: "{{tq|In the early 20th century, German colonial officers in East Africa tried to use zebras for both driving and riding, with limited success.}}" Martinevans123 (talk) 13:19, 1 May 2025 (UTC)

::Didn't Hannibal and his guys famously ride African elephants across the Alps? 146.200.107.90 (talk) 13:17, 1 May 2025 (UTC)

:::He used a different species, North African elephant, which is now extinct. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:48, 1 May 2025 (UTC)

::::Did the Romans wipe them out? —Tamfang (talk) 19:24, 4 May 2025 (UTC)

:::::According to the article, Yes. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:01, 4 May 2025 (UTC)

:Rhinos are considered the 4th most ferocious animals in the world (right after the African elephant, the African killer bee -- WTF, no article?! -- and the sun bear, in that order), so this is probably the reason why. 2601:646:8082:BA0:F051:2F1F:9C50:8350 (talk) 10:20, 1 May 2025 (UTC)

::IP editor. I think you want the Africanized bee article. Mike Turnbull (talk) 10:46, 1 May 2025 (UTC)

::Riding African killer bees might be tricky, but probably ecologically sound. Martinevans123 (talk) 10:59, 1 May 2025 (UTC)

:The rhinoceros doesn't even make it to this list [https://www.discoverwildlife.com/animal-facts/deadliest-animals-to-humans]. NadVolum (talk) 11:40, 1 May 2025 (UTC)

:Taming and domesticating are different concepts. When taming an animal, humans change their behaviour to make them more willing to cooperate with humans. When domesticating an organism (not necessarily an animal), its genetics are changed to make them more suited to what humans want to do with them. Arguably, elephants have been tamed, but not domesticated (tame working elephants are usually female and impregnated by wild males, so genetically they're still wild) and silkworms have been domesticated, but not tamed. Any species that can be bred in captivity can be domesticated, but not necessarily tamed. Social animals, like elephants, horses, buffalos and wolves, are usually easier to tame than solitary animals like rhinos, but that's not a very hard rule. Smarter animals also tend to be easier to tame, as they have more learned and less instinctive behaviour. Animals that have been tamed are easier to domesticate (as one can handle them in captivity), animals that have been domesticated can be easier to tame (after selective breeding to make them more cooperative) and provide higher rewards after taming (as they can do more useful jobs).

:Some issues with riding rhinos appear to be:

:*As a solitary animal, it may be harder to tame.

:*They are dangerous. When taming an animal, most people prefer one that's less likely to kill them.

:*Rhinos procreate slowly and need a huge pasture, making selective breeding expensive.

:*Like elephants, they are too large to be efficient people movers, limiting their use to moving goods and VIPs.

:PiusImpavidus (talk) 12:58, 1 May 2025 (UTC)

::Year of the Elephant. 2A02:C7C:F0EC:ED00:B968:4A6C:C17D:3311 (talk) 15:27, 1 May 2025 (UTC)

:Indian Rhinoceroses have been killing people rather frequently: [https://www.theguardian.com/environment/2025/apr/16/conservation-success-rhinos-nepal-human-conflict-towns-chitwan-national-park-aoe Sauntering on streets and grazing on lawns: what happens when rhinos move into town? ] Modocc (talk) 00:04, 2 May 2025 (UTC)

Meta-pedantic peeve: When you use a pedantic plural, make sure you actually get it right. Without looking it up, I'm pretty sure the word you want is rhinocerontes. Or, you know, just rhinoceroses is also fine. --Trovatore (talk) 19:15, 1 May 2025 (UTC) UPDATE: Looked it up and I can't find rhinocerontes; closest is Spanish rinocerontes without the h. Extrapolating from the ancient Greek it looks like it could maybe be rhinocerata, given that κέρᾰτᾰ is the nominative and accusative plural of κέρᾰς, "horn". --Trovatore (talk) 19:48, 1 May 2025 (UTC)

:The Ancient Greek plural is {{serif|ῥινοκέρωτες}}, not *{{serif|ῥινοκέροντες}} or *{{serif|ῥινοκέρατα}}. Wiktionary lists rhinocerotes, coming to us via Latin from Greek, labeling it as "now rare".  ​‑‑Lambiam 22:08, 1 May 2025 (UTC)

::Its plural is rhinoceroses according to Google's AI [https://www.google.com/search?client=firefox-b-1-d&q=rhinoceros+plural] and rhinoceri places a distant second in occurrences. [https://books.google.com/ngrams/graph?content=rhinoceroses%2Crhinocerotes%2Crhinocerota%2Crhinocerata%2Crhinoceri%2Crhinoceroi%2Crhinocerosses&year_start=1800&year_end=2000&corpus=en-2012&smoothing=3] Modocc (talk) 22:34, 1 May 2025 (UTC)

:::Thanks {{u|Lambiam}} and {{u|Modocc}}; good info. I still think if you're going to go for pedantic and say rhinoceri, you might as well go all the way to diatopically/diachronically correct and say rhinocerotes. --Trovatore (talk) 02:59, 2 May 2025 (UTC) For avoidance of doubt, presumably pronounced /raɪnɔːsɛroʊtiːz/, rye-naw-seh-ROTE-eez. --Trovatore (talk) 03:10, 2 May 2025 (UTC)

:Given that ceros ≠ κέρᾰς, I would not bet on κέρᾰτᾰ. I'd have guessed ceroi.

:At least OP did not go with cerii. —Tamfang (talk) 19:27, 4 May 2025 (UTC)

::Ride 'em cowboy! Martinevans123 (talk) 19:39, 4 May 2025 (UTC)

= May 2 =

Whence comes this misconception that the apple fell on Isaac Newton's head when he first got the idea about the law of gravitation? Anyone know the source of the confusion? 2601:646:8082:BA0:84C8:522A:EF41:5D (talk) 05:31, 2 May 2025 (UTC)

:The oldest recorded source may be a letter by Euler, dated 3rd September 1760. In translation:

::{{serif|This great English philoſopher and geometrician, happening one day to be lying under an apple-tree, an apple fell upon his head, and ſuggested to him a multitude of reflections.}}^{[https://books.google.com/books?id=_1oIAAAAIAAJ&pg=PA202&dq=%22an+apple+fell+upon+his+head%22&hl=en]}

:If the story of a falling apple being a source of inspiration is true at all, we cannot be certain that said apple did not actually land on the great philosopher's noggin. In Voltaire's poem, Newton saw the apple falling, but neither Conduitt's nor Stukeley's account (see {{section link|Isaac Newton%27s apple tree#The apple incident}}) states that the observation was visual. Conduitt writes that the apple landed "on the ground", but this may have been his assumption if Newton, regaling others of his inspiration story, left the somewhat ignominious landing site unspecified.  ​‑‑Lambiam 08:09, 2 May 2025 (UTC)

::Thanks! So, probably a case of Chinese whispers about the incident, then? 2601:646:8082:BA0:8029:3AF8:59DC:7A79 (talk) 12:04, 2 May 2025 (UTC)

:::It makes for a more colorful story if it literally hit him on the head, rather than just metaphorically. ←Baseball Bugs ^{What's up, Doc?} carrots→ 15:40, 2 May 2025 (UTC)

Is it true that on a Stanier Black Five, when running flat-out, the boiler could actually boil the water faster than the injector could pump it in? I've done the calculations for the maximum steaming rate earlier today (based on the boiler being able to make just enough steam to supply the cylinders at 55 mph with full throttle and 15% cutoff), and by my calculations the boiler can vaporize a maximum of 10.2 gallons of water per minute -- is this an accurate estimate, and if so, is it more than the maximum flow rate through the injector? 2601:646:8082:BA0:79DE:B608:5A9E:D281 (talk) 06:18, 2 May 2025 (UTC)

:I'm no specialist on the Stanier Black Five, but since nobody answered within 24 hour...

:With such cylinder dimensions and at 15% cut-off, it uses 18.5 litres of high-pressure steam per stroke. At 55 mph (one Black Five reached 96 mph, but this may have been on the downhill), such wheels and 4 strokes per revolution, that's 17 strokes per second. Combined, that's 317 litres of steam per second. I don't know the density of that steam (because I don't know the temperature after the superheater), but I suppose something like 3–5 grammes per litre, so that's somewhere around a kilogramme per second. Your 10.2 gallons per minute equals 765 grammes per second (assuming those are Imperial gallons, it's after all a British locomotive; your IP location, time of posting and spelling suggest however that your gallons may be smaller), so that's close. With the given grate area, this is more or less what's expected. So yes, your estimate appears reasonably accurate.

:Now keep in mind (you probably know this, but I'll mention it anyway) that with steam locomotives there's a big difference between sustained power and peak power; sustained steam use and peak steam use. You can extract a huge amount of power and steam out of the boiler by letting water level, temperature and pressure drop, much more than the fire and injectors can provide. This is nice, as trains need more peak power than sustained power, and explains why big firetube boilers are good, despite being slow to bring up to working pressure. I suppose the question is about sustained steam generation.

:Having a firebox that can heat water from room temperature (or a bit hotter, assuming a pre-heater) to 200°C and then boil it faster than your injector can provide this water has some advantages. There's a faster cold start and peak power can be sustained longer, as pressure drops less fast. The cost is a faster drop in water level. Having oversized injectors also has an advantage: you can quickly fill the boiler, at the expense of a pressure drop, which may be good when cresting a summit. On the descent, you don't need boiler pressure, but you do need high water level to keep the crown sheet, now at the high end of the boiler, covered. I suspect engineers (=the people designing them) typically aimed to have the injectors somewhat oversized compared to the grate, also because injectors are cheap compared to grate area. Less than optimal designs were common though, as engineers often worked more on experience and educated guesses than on science.

:I don't know about the injectors on the Stanier Black Five.

:Most locomotives had two injectors. On express locos, often one was powered by exhaust steam (after the cylinders, before the blast pipe, there was enough pressure left) and running whenever the loco was moving. The other was powered by steam directly from the boiler and used only when more water was needed. The exhaust injector, working on lower pressure steam, would have less capacity than the live injector, even more so at short cut-off. PiusImpavidus (talk) 10:13, 3 May 2025 (UTC)

Around the late 2010s decade or maybe early 2020s, I came across a Wikipedia article about the mechanical engineering mathematics of connected bodies (by something like a string, for example). I do not remember the title of the article, but it had a parenthesis term at the end of its title, like (mechanics) or (engineering) or (kinetics) or , but I don't remember the word exactly.

The article may have been similar to the articles "Dynamics (mechanics)" or "Linkage (mechanical)" or "Tension (physics)", except it was about a very specific topic. The article may have been related to categories like ":Category:Mechanics" or ":Category:Dynamics (mechanics)".

The article has either been deleted, renamed or changed so much that I no longer recognize it. I was interested in it because it seemed like it could be relevant to a topic I am studying, the n-body problem.

If you know the topic that I am talking about, please let me know. Cerebrality (talk) 12:42, 2 May 2025 (UTC)

:@Cerebrality AI is getting better. I asked MS Bing "what is the wikipedia article about mechanical engineering mathematics of connected bodies?" and it said Kinematic chain. I hope that's it! Mike Turnbull (talk) 16:05, 2 May 2025 (UTC)

::Thank you for contribution. Unfortunately, "kinematic chain" is not the article I was looking for. Cerebrality (talk) 00:30, 3 May 2025 (UTC)

:::Perhaps Dynamic substructuring? The Udwadia–Kalaba formulation can also be used to derive the equations of motion of a system of connected bodies, but I'm not sure this can be used for bodies connected by strings.  ​‑‑Lambiam 09:06, 3 May 2025 (UTC)

::::Thank you for contribution. Unfortunately, while interesting, this is not the article I was looking for. Cerebrality (talk) 14:06, 3 May 2025 (UTC)

= May 3 =

I'm reading a story in which (among other things) someone is trying to build a gun that shoots 1.5kg iron slugs (5cm diameter) at 60% of the speed of light, for use in space combat.

1) How do I calculate the kinetic energy of the slug? Do I just use $E/\backslash sqrt\{1-0.6^2\}=E/0.8=1.25E$ where E is the Newtonian approximation? I think that is about as much energy as a 7MT nuclear bomb, if that matters.

2) What happens if the slug actually hits a spaceship? Would it most likely just punch a hole all the way through, without slowing down much? Assuming a large enough ship to self-seal around the holes, is that all that effective a weapon? I.e. the ship is USS Enterprise size or larger.

Thanks. 2601:644:8581:75B0:3DAF:465A:7AA1:65A0 (talk) 04:04, 3 May 2025 (UTC)

:The article Railgun may be helpful.-Gadfium (talk) 04:30, 3 May 2025 (UTC)

:The total energy is $\backslash frac\{m\; c^2\}\{\backslash sqrt\{1-\backslash frac\{v^2\}\{c^2\}\}\}$. Subtract from it the rest energy $m\; c^2$. See kinetic energy (there is a section on the relativistic generalization). Icek~enwiki (talk) 06:12, 3 May 2025 (UTC)

::Using the Lorentz factor

:::$\backslash gamma=\backslash frac1\{\backslash sqrt\{1-\backslash frac\{v^2\}\{c^2\}\}\},$

::this difference can be written compactly as $E\_\backslash text\{kin\}\; =(\backslash gamma-1)\backslash ,mc^2.$

::When $v=0.6\backslash ,c,$ we have $\backslash gamma-1=0.25.$ The energy required to get the projectile up to speed is at least equal to the kinetic energy it gains, about 33.7 PJ. For comparison, the energy released by the Trinity nuclear test was about 0.1 PJ. BTW, the material composition of the slug is immaterial; it might as well be a canister of elderberry preserve.  ​‑‑Lambiam 08:39, 3 May 2025 (UTC)

:That would depend on the spaceship. Is the hull made of unobtanium? Are there shields of some sort? Clarityfiend (talk) 11:07, 3 May 2025 (UTC)

:At this speed each iron nucleus will have energy of about 15 GeV, which will absorbed by the material the hull is made of. This with result into fireball of high temperature plasma exploding inside the ship. Ruslik_Zero 20:07, 4 May 2025 (UTC)

::Hmm, will it, though? This isn't a single nucleus; it's a big ol' hunk o' metal. The spaceship atoms in the way of the slug atoms are going to be getting out of the way in a hurry. How much they interact with the rear portion of the slug strikes me as a fairly difficult simulation problem that depends on a lot of details that haven't been specified, but I can imagine a fair portion of the energy being carried out the other side of the spaceship, still as kinetic energy.

::I certainly agree that it isn't going to be good for the spaceship, but if the question is whether we're wasting energy that isn't going into the kill, I don't think we can answer that with the information given. --Trovatore (talk) 20:27, 4 May 2025 (UTC)

Thanks everyone. Yes the ships have deflector shields that use antigravity generators of some kind, which is why such fast projectiles are needed. The shields can handle the impacts at 0.1c which is why they are working on getting the speed up to 0.6c. If the defector shield means the slug's energy is transferred to the shield though, that's probably worse than just punching a hole in the ship and coming out the other side. 2601:644:8581:75B0:C710:F116:861:28C5 (talk) 09:30, 5 May 2025 (UTC)

:Hmm, I wonder whether the articles Stopping power and Terminal ballistics might be of any use to answer your question? 2601:646:8082:BA0:C887:6F01:C269:367F (talk) 13:07, 5 May 2025 (UTC)

(CC:{{ping|Prokaryotic Caspase Homolog}})

File:Time_Dilation_vs_Orbital_Height.png

In the attached thumbnail, GP-A which is presumably Gravity Probe A is placed on the gravitaional time dilation graph instead of the total time dilation one like the others. Is there a reason for it? Thanks, cmɢʟee⎆τaʟκ 22:33, 3 May 2025 (UTC)

:GP-A did not orbit. It was launched nearly vertically, reached 10,000 km, and came back down. —Amble (talk) 02:54, 4 May 2025 (UTC)

::Thanks. That explains it. Cheers, cmɢʟee⎆τaʟκ 19:13, 4 May 2025 (UTC)

= May 5 =