Wikipedia:Reference desk/Archives/Science/2023 June 22

= June 22 =

Omega-6 vs. omega-3 fatty acids.
All over the media says omega-3 is healthy and omega-6 is not, except omega-6 can be healthy if taken at the same ratio at omega-3. But upon reading omega-6, gives contradicting information, saying the components of it are healthy. Linoleic acid is a more healthier omega-6, while arachidonic acid, is not. Seed oils high in linoleic acid include corn, cottonseed, soybean, and sesame (58%, 54%, 51%, and 41.3%), while seed oils high in arachidonic acid include soybean oil. In fact, out of the only 2 essentially fatty acids that the body requires but cannot synthesize, are linoleic acid (an omega-6) and alpha-linoleic acid (an omega-3), both polyunsaturated. I wonder if anyone can give feedback on this paradox heh. 170.76.231.162 (talk) 17:52, 22 June 2023 (UTC).
 * I don't see the problem. Both omega-3 and omega-6 fatty acids are necessary for a healthy diet. But too much of either of them (or of ANY food component) is unhealthy. Even too much oxygen or too much water can kill you.--User:Khajidha (talk) (contributions) 18:57, 22 June 2023 (UTC)
 * Both are are required for good health; see Essential fatty acid interactions. The healthiness of a nutrient that is not a straight-out poison cannot be discussed in isolation. That also holds for essential nutrients. Almost all popular sources discussing dietary choices and health make unjustifiable simplifications and generalizations; it is best to take their advice with a grain of salt. Not too much though; your body needs salt but too much is unhealthy. In fact, getting too little or too much of any nutrient are both harmful, but what is too little or too much may depend on the person and their constitution. (Vitamin C is a rare exception in that getting more than is useful appears to be harmless.) --Lambiam 19:36, 22 June 2023 (UTC)
 * Well, there is some thought that it increases the risk of certain kidney stones. --User:Khajidha (talk) (contributions) 19:42, 22 June 2023 (UTC)

What's the straightest flight?
Where the wheel touch-to-wheel touch part of a flight number fits an ellipsoid geodesic very well with no yawing from liftoff to touchdown for any reason except the mildest turning and it's a Boeing/Airbus-sized jet. Maybe not being turnless every time but more than half of the time. When I was about 10 I wondered if they ever did this when the runways and shortest path almost aligned and the more I learned about aviation the rarer it seems. Sagittarian Milky Way (talk) 19:19, 22 June 2023 (UTC)
 * So you'd need two commercial airports, where each has a runway pointing at the other airport? DMacks (talk) 19:32, 22 June 2023 (UTC)
 * You need only one runway. If the aircraft keeps flying straight along the geodesic it took off along, it will end up where it came from and can land on the same runway. --Lambiam 19:45, 22 June 2023 (UTC)
 * It'd be harder than usual to sell an over 44 hour long nonstop flight to nowhere and Heathrow to Sydney is barely commercially viable a few years from now maybe even with Qantas publicly challenging Airbus and Boeing to invent something fuel-efficient enough to carry enough self-loading cargo and all the low-hanging fruit is gone for getting closer to maximum thermodynamic efficiency, flying more than 2.35 times as far would be amazing. Sagittarian Milky Way (talk) 20:15, 22 June 2023 (UTC)
 * You did not specify it had to be a commercially viable flight. --Lambiam 10:03, 23 June 2023 (UTC)
 * If it's not commercially viable it doesn't exist so can't be the straightest! Sagittarian Milky Way (talk) 12:40, 23 June 2023 (UTC)
 * Also a straight diagonal at the equator line on the Earth ellipsoid gets surprisingly far from the starting point in only one orbit. Not like enough to precess all the way around in only a few orbits but enough to precess around in like 418 orbits. Sagittarian Milky Way (talk) 20:51, 22 June 2023 (UTC)
 * And the wind from the correct half in both airports cause landing with a groundspeed faster than airspeed is frowned upon and without mandatory restricted area avoidance turns (i.e. all westward takeoffs from JFK do a hard left as soon as it's safe to to annoy less people, ex-Hong Kong dodged skyscrapers or mountains before landing) and approach and departure paths seem highly regulated in most or all places. They don't let you fly where you want in busy areas. Sagittarian Milky Way (talk) 19:51, 22 June 2023 (UTC)
 * Your original question was missing a lot of details that you now seem to think are important, such as a distance, airspace restrictions, and some vague notion of commercial/public value. Stop making us guess: state the parameters please. But for "round trip to nowhere", a bunch of airports not near major restrictions at various latitudes have a runway 9/27, so you can pick a latitude, check earth circumference there, and then check if the true heading is within your as-yet-unstated tolerance. For example, the circumference of the earth at Sveg Airport is about 8000 miles (obviously varies with altitude, another parameter you didn't specify) and the true heading of the runway is about 3° from due east/west. DMacks (talk) 21:34, 22 June 2023 (UTC)
 * None of those details changes the answer, I was just responding to Lambiam that the longest nonstop airline flight ever made or in the foreseeable future is less than 1/2.35th of a circumference so it isn't 1 runway. If they ever do then I guess that's close enough (a few dozen miles off as I also said). "Airspace restrictions" and "whether any airline wants to run a Boeing/Airbus-sized jet between these airport pairs" are merely more reasons why "geometrically possible" and "a flight number exists that the general public can book a seat on that goes straight on most trips" are not the same thing. Tolerance is whatever's the straightest that has been mentioned so far. Altitude not important. Finally even if someone did inexplicably start Boeing/Airbus jetliner-sized service (from Sveg of all places!), going east or west till you came back (that runway looks a bit small) that'd be very far from the geodesic which penetrates 60 degrees south. Also if you walk around the North Pole staying 1 meter away you clearly have turned even though you went east or west the whole time. East or west clearly isn't straight except for the equator. Sagittarian Milky Way (talk) 23:38, 22 June 2023 (UTC)
 * The question is well-defined and he did not alter anything. He mentioned geodesic from the beginning.
 * It can't be a long flight, though. Wind always influence fuel economics. Zarnivop (talk) 02:42, 23 June 2023 (UTC)
 * It's even possible that on a straight flight (including both runways) that was in the direction of the prevailing wind (normally a helpful thing), the pilot might turn 180 degrees for take-off and landing just to perform them into the wind. -- Verbarson talkedits 16:36, 23 June 2023 (UTC)
 * With the consequence that if flight XXXX does that flight XXXX±1 probably is forced to fly upwind the whole way cause you can't move the cities. Unless the physical plane only triangles from A to B to C to A in a circuit and not A to C to B to A. Do one way loops like this exist where you can fly nonstop from A to B but not B to A? Sagittarian Milky Way (talk) 18:12, 23 June 2023 (UTC)