Wikipedia:Reference desk/Archives/Science/2019 April 11

= April 11 =

Flight planning
Several questions: (1) Can a Gulfstream jet fly from Seoul to any airport within the contiguous USA nonstop, and if so, how many hours would the flight take? (2) If not, can it make the same flight starting from Tokyo, and how many hours would that take? (3) If either of these is possible, then after stopping to refuel (presumably somewhere on the west coast), how many more hours would it take for the jet to reach Washington DC? 2601:646:8A00:A0B3:78DA:714:B603:E789 (talk) 03:45, 11 April 2019 (UTC)


 * The article you linked shows that the Gulfstream 650ER has a range of 7,500 nautical miles or 13,890 km. The linked article about the specific model says it has this range at a speed of Mach 0.85.  13,890 km is far enough to reach any part of the USA from Seoul, provided that you have permission to fly over other countries as needed&mdash;probably North Korea, China, Russia, and Canada.  For example, the direct route from Seoul to Washington DC is only 11,197 km.  Now the speed of sound at typical airliner altitudes is just about 300 m/s, so the flying time (without delays for weather, air traffic, etc.) would be about 12 hours (corrected from first posting where I missed the 0.85 factor).  If you have to avoid certain countries, of course it would be longer. --76.69.46.228 (talk) 04:19, 11 April 2019 (UTC)


 * Thanks! So if the flight leaves in the small hours of the morning, then they'll reach Washington some time in the afternoon, without delays? 2601:646:8A00:A0B3:78DA:714:B603:E789 (talk) 04:46, 11 April 2019 (UTC)
 * Well, Washington is 13 hours behind in time zone, and the flight would cross the international date line. So you would leave at 4 am on Thursday, you would arrive at 5 am on Thursday ;-) (modulo my brain being not quite awake yet). --Stephan Schulz (talk) 05:37, 11 April 2019 (UTC)
 * Oh, I forgot all about the time zones! So it would still be at night? 2601:646:8A00:A0B3:78DA:714:B603:E789 (talk) 07:10, 11 April 2019 (UTC)
 * Not "still" but "again". Flying east gives you shortened days and nights, so you'd have sunrise and sunset within the 12-hour flight.  Those of us who live in eastern North America and have flown to Europe will remember that you can leave not long after suset and arrive around breakfast time after only about 7 hours of travel. --76.69.46.228 (talk) 05:23, 12 April 2019 (UTC)
 * Yes, indeed, and now that my brain had a minimal amount of coffee, if a 12-h flight east results in a 13 time zone skip, you would indeed arrive one hour earlier than you left off ;-). This effect made Phileas Fogg a cool 20000 Victorian pounds. --Stephan Schulz (talk) 07:46, 11 April 2019 (UTC)
 * Just a note, the effect is because the plane is (very roughly) flying at the same speed the Earth is spinning, so when you fly in the same direction as that spin, you basically arrive at the same (local) time as you left; in other words in the time it took you to fly twelve hours, the earth also rotated through about 1/2 (or 12 hours) of it's day. Relative to the sun, you're basically standing still.  In the case of getting there an hour earlier, you beat the sun by 1 hour to where you were headed.  This is why the International Date Line is necessary.  If you could stay aloft at that spot as the earth spun underneath you, your clock would not change in local time, but you would still need to mark the passage of each day.  By convention, we do that at the Date Line.  -- Jayron 32 10:56, 11 April 2019 (UTC)
 * That would be correct if the flight was westbound (leave Washington 4 am Thursday, arrive Seoul 5 am Friday without ever seeing much daylight).
 * All that depends on your latitude. Go far enough south and you can walk at the same speed as the Earth beneath your feet is spinning. Bazza (talk) 13:06, 11 April 2019 (UTC)
 * Or north. I'm pretty sure there was a performance artist that performed that feat at the north pole, essentially shuffling his feet over the course of 24 hours so that he did not turn with the earth. Googling is failing me this morning, though, so I can't seem to pick up the name. Matt Deres (talk) 14:35, 11 April 2019 (UTC)
 * Yes, that just means that the "hour" marker on his watch never changes; only the minute and day. If he was clearing a (nominal) time zone per hour, he would remain in the same hour window all day, and then flip the day ahead when he cross the IDL.  -- Jayron 32 16:22, 11 April 2019 (UTC)
 * Gulfstream publishes an interactive range map, if you want to play with it. A G650ER can depart Japan or Korea and can reach nearly any destination in the populated parts of Europe or the North American continent, without refueling.  Yet, this is under ideal conditions with range as the primary consideration; in practice, other factors might change the plan, including considerations about weather, passenger-comfort, and schedule.
 * The fine print reminds us that "best range" conditions for the G650ER involve flying slower, carrying less than half the peak passenger load, and receiving direct routing from air traffic control. In the real world, you'd want to plan a safety factor to ensure you could guarantee you had enough fuel, beyond any reasonable doubt, even if faced with adverse unplanned conditions.
 * Nimur (talk) 14:04, 11 April 2019 (UTC)
 * In my case, the flight involved will carry 1 litter patient who was rescued from a North Korean prison camp (+ medical personnel), and it will be imperative for the flight to stay out of North Korean airspace and possibly Chinese airspace as well (but Russia will most likely allow a medical flight to fly over its soil). And the patient in question has precisely 100 hours to live at the time of his rescue unless successfully operated on.  As for fuel reserves, the normal IFR reserves will apply. 2601:646:8A00:A0B3:78DA:714:B603:E789 (talk) 01:26, 12 April 2019 (UTC)
 * Looking at the map link I posted before, it doesn't seem as though it would add much distance to avoid both North Korea and China, but I have not tried to work out how much. By the way, if this is for a novel, be aware that "precisely 100 hours to live" is a cliche of unrealistic writing and is not the sort of thing any doctor would predict. --76.69.46.228 (talk) 05:23, 12 April 2019 (UTC)
 * Not if he has several poison pellets implanted in his vital organs with delayed release (or timed release -- which one of these terms is correct?) set for 100 hours after implantation (as is the case here). 2601:646:8A00:A0B3:78DA:714:B603:E789 (talk) 07:18, 12 April 2019 (UTC)
 * Might the evacuee be transported on a military medevac flight, like the C-130, Mainstay of Medevac (as detailed in that 2018 article by the US Air Force Pacific (PACAF) press office?  ... or if it was truly a special requirement mission, a C-17 on a special ultra-long-range medevac mission?  Both aircraft have been used for medical transport missions, and are even capable of supporting medical procedures during flight.
 * In the wee hours of the morning, if you listen to air traffic in your neck of the woods, you will occasionally hear medevac callsigns on little jets, long after the mostly-living have been tucked away in bed. Here's the website of one corporation that operates mostly in the United States: LifeFlight fleet.  Their biggest gig is the Citation CJ4, which is already at the "so-extraordinarily-expensive-per-operation" mark that it defies logic to understand how, even for a noble safety-of-life mission, these guys can remain solvent.  I can only imagine that the Government will be paying for the fuel in your hypothetical fictionalized intercontinental Gulfstream medevac... so, ... why wouldn't they be using a Government aircraft?  On the other hand, maybe this fellow's spectacular American medical insurance  covers intercontinental jet airlift ... but as Life Flight says on their website, "If you are unfortunate enough to have an insurance company who decides to pass along a significant portion of the invoice to you, they may provide feedback that sounds reasonable, but is not."
 * Nimur (talk) 15:36, 12 April 2019 (UTC)
 * Using a heavy-lift jet to carry one person is even less economical -- and besides, the Herc is slow, and time is of the essence here! And doesn't the US Air Force have a few small medevac jets for contingencies just like this? 2601:646:8A00:A0B3:78DA:714:B603:E789 (talk) 11:29, 13 April 2019 (UTC)
 * The U.S. Air Force has many capabilities, and many aircraft, including the C-37A and C-21A; but to my knowledge, they have no small jets that are specifically tasked for medical evacuation airlift flights. On the contrary, they have Air Mobility Command, whose overall job is to manage and execute personnel and materiel movement, anywhere in the world, using the best-available asset.  There's probably an already-scheduled C-17 flight from Point A to Point B (for arbitrary points A and B) and if the need is great enough, they can probably find space on it for your two tons of unmarked cargo.
 * Typically, a military medical evacuation is conducted on the ground using an ambulance; and if it's very urgent, it's possible that the Army (or similar organization) might fly the patient to the local airfield hospital, using a Black Hawk or a UH-72, or something similar. If the patient needed to be taken farther - because the local in-theater hospital isn't capable of helping - the Army would coordinate with the Air Force "Aerovac" for a long-range transport on a C-130 or C-17 or even on board a KC-135.  One can imagine that a similar process exists for non-Army patients in "similar" situations.  Somebody of sufficient authority would have to justify why the local hospital isn't good enough, because somebody else is going to have to justify the expenses.
 * More details are published in Army Techniques Publication 4-02.2 Medical Evacuation.
 * From the article I linked earlier, there is precedent for using a C-17 to airlift one patient: "We can do pretty much whatever is required..." but while we're aiming for hyper-realism, the same article also says: "paperwork, phone calls, e-mails, mission planning and weather support all had to be in line..."
 * The more special the mission, the more paperwork it's going to require... reality can be so much more interesting than fiction...!
 * Nimur (talk) 18:42, 14 April 2019 (UTC)

I have travelled on a commercial flight from Seoul to Chicago. We headed roughly SSW from Incheon, turning East but not overflying the S. Korean mainland. I think we crossed Kyushu and turning NE, we passed well to the east of Tokyo in adopting the great circle route. Not sure if we overflew Russia. Looking at the great circle mapper, the route fro Tokyo to Washington would definitely overfly Russia, the route to Chicago might, and the flight I was on possibly didn't. Direct from Seoul to Chicago is about 400 miles shorter than to Washington, and both would overfly N. Korea and Russia and China. I'd say the ICN-ORD path I flew was near 8,000 miles, compared to the direct route of about 6,500 miles, so whether a Gulfstream could do this sort of route to Washington without refueling is doubtful given that ICN-NRT-IAD is 7,536 miles and going south of Tokyo will add to that. EdChem (talk) 04:25, 17 April 2019 (UTC)
 * At the altitudes a Gulfstream flies, the jet stream wind speed is not negligible: consult the High Level SigWx charts. On any given day, winds aloft are regularly over 100 knots, which alters the range and ground-speed of a fast jet in a very considerable fashion.  Winds aloft are so significant that the shortest path (e.g. the great-circle) is often not the fastest path.
 * For example, at this very moment, winds aloft at the high flight levels over the Korean peninsula are faster than 150 knots, and they're probably blowing in the "wrong direction" if one hopes to fly the great circle to the United States.
 * International flight planning is a complicated science!
 * Nimur (talk) 22:52, 18 April 2019 (UTC)

X and Y chromosomes versus others in genetic diversity
As I understand it, any particular non-sex chromosome a person "inherits" from a parent need not be identical to any such equivalent from that parent (e.g. my chromosome 1 from my mother will be some sort of blend of both her chromosome 1s).

My question: is this true for X chromosomes inherited from mothers? It's difficult to see how it could be true for X and Y chromosomes from fathers, so are these (near) identical in the father and child?--Leon (talk) 15:55, 11 April 2019 (UTC)
 * No, there is some crossover between X and Y chromosomes from the father. See Pseudoautosomal region, which is the part of those two chromosomes which are homologous to allow crossover.  In those regions, in meiosi,s in the father there is crossover in those regions, thus a daughter CAN inherit genes from their father's Y chromosomes, if those genes were in these regions.  -- Jayron 32 16:21, 11 April 2019 (UTC)
 * Interesting, does it work the other way round (can a son inherit some of their Y chromosomal DNA from their father's X chromosome)?--Leon (talk) 19:37, 11 April 2019 (UTC)
 * The answer appears to be "yes", if I understand the article correctly. The pseudoautosomal region is the remnant of the ancestral X and Y chromosomes, which were regular paired autosomes just like the other chromosomes. For more info: XY sex-determination system. --47.146.63.87 (talk) 23:00, 11 April 2019 (UTC)
 * Note however per the article, in humans the regions are only about 3Mbp compared to 155 Mbp and 59 Mbp for the respective chromosomes. So it's only a small part of the X and Y chromesome from the father that isn't inherited intact. For the X chromosome from the mother, AFAIK recombination is no different from any other chromosome. Nil Einne (talk) 03:02, 12 April 2019 (UTC)
 * Chromosomal crossover is the article on the general topic. --47.146.63.87 (talk) 23:00, 11 April 2019 (UTC)