Wikipedia:Reference desk/Archives/Miscellaneous/2023 March 16

= March 16 =

Travelling a light second
I was cogitating about celestial infinities, as one does, and it occurred to me that, while a single light year is a very long way in human terms, even a light second is quite a stretch. And I wondered if we know who was the first human to travel 186,000 miles (c. 300,000 km) in their lifetime. -- Jack of Oz   [pleasantries]  21:19, 16 March 2023 (UTC)
 * That's only about 10 miles per day for 50 years. Undoubtedly some trader or other itinerant traveled that far in ancient times, possibly just by walking. (That's ignoring the quibble that everyone on Earth travels that far around the sun in less than an hour.) CodeTalker (talk) 22:18, 16 March 2023 (UTC)
 * Methinks 10 miles a day is not an average that would be easy to maintain over such a long period as 50 years, prior to the modern era. --  Jack of Oz   [pleasantries]  06:16, 17 March 2023 (UTC)
 * I agree with JackofOz. I don't think anyone travelled a light second earlier than in the 19th century. Think railroad operators or workers on ocean-going steamships which already were available in the 19th century, I think only they had a chance. The 20th added aircraft and automobiles. --Ouro (blah blah) 07:14, 17 March 2023 (UTC)
 * George Müller (1805-1898) travelled 200,000 miles as an evangelist. According to this source, this was "an extraordinary feat in the 19th century". So, we have a latest possible date. --  Jack of Oz   [pleasantries]  08:24, 17 March 2023 (UTC)
 * Triangle trade2.png A sailor on a ship involved in the classical model of the Atlantic triangular slave trade would traverse more than 22,000 km in a single run, which could easily be completed within one year. Can we exclude the possibility out of hand that some unnamed soul signed up for at least fourteen such runs? --Lambiam 09:44, 17 March 2023 (UTC)
 * 10 miles a day? Balgarnie says in his hagiography of Titus Salt, It was a long distance for a boy of his years to walk every day. How few boys now-a-days would do it! Six miles to school and back! Yet he was only one of a group to whom the journey was a healthy and bracing exercise.
 * We're not talking daily for fifty years, of course. But if twelve miles a day was not something that was thought unreasonable for an eight year old boy in 1810, I wonder whether a light-second was so unattainable for an ordinary person going about their daily business. ColinFine (talk) 13:41, 17 March 2023 (UTC)
 * "Going about their daily business" covers a lot of imponderables. I comfort myself that just going about the house, doing the shopping, attending appointments, visiting friends, and similar incidental walking all counts towards the 10,000 or however many daily steps I think I'm supposed to do. But it doesn't count as "travel". --  Jack of Oz   [pleasantries]  22:51, 17 March 2023 (UTC)
 * That seems a weirdly limited definition of travel. I think most people will be perfectly fine with the statement "I travel 20 km to work/school everyday" e.g. [//forums.whirlpool.net.au/archive/1313628] or talking about how long or far it is to travel to the nearest supermarket [//www.stuff.co.nz/business/124783884/christchurch-coastal-suburb-loses-struggling-supermarket]. And in NZ the cost of travel for health appointments is something you can get assistance for [//www.workandincome.govt.nz/eligibility/health-and-disability/travel-costs.html]. It does have to be at least 8km but I'm fairly sure that's because travelling shorter distances are seen as something you should be able to financially manage yourself rather than because it isn't travel. Nil Einne (talk) 16:13, 18 March 2023 (UTC)
 * Funnily enough I just saw this TV commercial in NZ. [//www.youtube.com/watch?v=f11SQgDFmnk] / [//www.youtube.com/watch?v=-DcYOlfOCK4] (It's not new and I may have seen it before but I rarely watch live broadcast TV.) It claims the average person travels 25000km in their home throughout their lifetime. I wouldn't trust that stat but it does illustrate IMO that at least in NZ not that many would quibble over talking about someone traveling in their own home. Nil Einne (talk) 09:15, 20 March 2023 (UTC)
 * According to the Marco Polo article, it took him 24 years to travel to Far East Asia and back (Marco Polo) along the Silk Road (File:Travels of Marco Polo.svg), which was about 15,000 miles (24,000 km). That makes an impressive trip, but far too slow for a supposed one light-second travel – the average speed of 1,000 km/y would require 300 years to complete the task. The Silk Road article mentions the Persian Royal Road (Silk Road), which was about 2,857 km (1,775 mi) long and used to be travelled in nine days by royal couriers (although it doesn't mention how often one courier might have been sent, or how long one person could serve the function). By rounding the distance up to 3,000 km one way, and six thousand there-and-back, about 50 trips would be needed to cover one light-second. Assuming one trip per month, one would need less than two years and a half to complete 1 l.s. --CiaPan (talk) 11:27, 17 March 2023 (UTC)
 * The text says "By having fresh horses and riders ready at each relay, royal couriers could carry messages and traverse the length of the road in nine days" [my italics]. So did all the individuals traverse the whole length of the route, or did they all merely go back and forward between two relay stations while the messages themselves were carried onward by the next set of riders, or did individuals (the royal couriers) travel the whole route guarded by relays of riders? I suspect the latter, but the text could be made clearer. {The poster formerly known as 87.81.230.195} 5.64.160.67 (talk) 23:54, 17 March 2023 (UTC)
 * According to Herodotus VIII.98 the message was passed hand to hand from one rider to the next. "These neither snow nor rain nor heat nor darkness of night prevents from accomplishing each one the task proposed to him, with the very utmost speed." So the message kept moving, day and night. --Lambiam 08:30, 18 March 2023 (UTC)
 * I suspect Herodotus adapted that from Sir Terence Pratchett's historical study of the Ankh-Morpork Post Office. "Neither Rain Nor Snow Nor Glo : m Of Ni : : t Can Stay these Mes : engers Abo : t Their Duty " (The stolen borrowed letters spelled "Hugos", the apostrophe-deficient name of a nearby hairdressing salon.) {The poster formerly known as 87.81.230.195} 5.64.160.67 (talk) 01:23, 19 March 2023 (UTC)
 * It is a reasonable assumption that the Angarium would have striven to keep prompt and thrustworthy chapars in their service as long as they were fit, so the time can plausibly be pushed back to the days of Darius I . --Lambiam 11:54, 17 March 2023 (UTC)
 * There is some internal inconsistency in the data reported in the article Angarium. It is stated that the distance from Susa to Sardis, 2699 km, was covered in 9 days. This is sourced to The Persian Empire: A Historical Encyclopedia, also cited in Royal Road). Other sources even make this only 7 days. Sticking with 9 days and rounding 2699 up to 2700, that is on average 300 km per day. But Herodotus writes, "according to the number of days of which the entire journey consists, so many horses and men are set at intervals, each man and horse appointed for a day's journey". Combined with the other bit of info this implies that a horse can cover 300 km in one day. But no horse could do this before automobiles with horse trailers were invented. A plausible distance a horse can go on foot in one day is 50 km, so if each horse completes a day's travel, 2700/50 = 54 horses are needed, 54/9 = 6 horses per calendar day. The road needs to be divided into equally many tranches to supply a rested horse at each stop. This gives 24/6 = 4 hours travel time for each tranche. A horse in good condition can cover 50 km in just 4 hours, but then definitely needs to rest. The limitations make it much less plausible that any Persian courier completed one lightsecond. My money is on an unknown 18th-century sailor. --Lambiam 10:54, 19 March 2023 (UTC)
 * I'm pretty sure horses can go a lot more than 50km per day if properly kept and fed and allowed rest between travel days. Endurance riding has official one-day competitions with up to 160km. Your 50km seems appropriate for a horse and rider doing long-distance travelling and foraging for horse food. --Stephan Schulz (talk) 14:38, 19 March 2023 (UTC)
 * Assuming riders and horses formed fixed teams, and a one-day rest for a horse after a day's travel of 150 km, a rider would traverse on the average 75 km on a day on the job. One lightsecond was then completed in 4,000 days, say 12 years. A twelve-year career for a sound and able rider is within the range of plausibility. Under the assumptions, given the large number of riders needed for the Angarium system, it is reasonably likely that at least one rider, some twenty-five centuries ago, met the 1 $c$ s limit. --Lambiam 12:31, 20 March 2023 (UTC)
 * Yes. And if they are organised like the Pony Express, with the rider changing horses but continuing, it becomes even more plausible. I don't know what the ancient sources say. But there also was a regular trade in the Indian ocean at that time, making use of the reliable Monsoon winds, and just like with the Atlantic triangle, some of the sailors there might have made it (though it's a bit harder). --Stephan Schulz (talk) 13:58, 20 March 2023 (UTC)
 * It's not that fast cause it's only ~0.0001 c and there's only 3,600 seconds in an hour. Sagittarian Milky Way (talk) 01:49, 22 March 2023 (UTC)


 * In Hertfordshire, there was a famous 12th-century hermit called Sigur, who lived in Northaw Woods but walked every day to St Albans Abbey to say his prayers before walking home again. Northaw is about 11 miles from St Albans, so he could have completed your light second challenge in 23 years and a couple of months, by my unreliable reckoning. Sadly, history doesn't record Sigur's longevity. Alansplodge (talk) 13:57, 19 March 2023 (UTC)


 * The sense I get from the above responses is that we don't know and will never know, because it was never recorded anywhere. It took some weirdo from the 21st century to even think of such an abstruse question. Thanks for all your research and thoughts. Yours sincerely, Some Weirdo From the 21st Century, aka Jack of Oz   [pleasantries]  07:20, 21 March 2023 (UTC)