Wikipedia:Reference desk/Archives/Science/2021 January 11

= January 11 =

When will Mars 2020 return sample to earth?
What I learn from Mars 2020 is that sample tubes are installed, so when will Mars 2020 return sample to earth? Rizosome (talk) 10:27, 11 January 2021 (UTC)
 * From the same article: "The "fetch rover" for returning the samples is expected to launch in 2026. The landing and surface operations of the "fetch rover" would take place early in 2029. The earliest return to Earth is envisaged for 2031." --Wrongfilter (talk) 10:57, 11 January 2021 (UTC)

Any real animal that people can ride on water like Lapras?
--Curious Cat On Her Last Life (talk) 12:23, 11 January 2021 (UTC)
 * See Dolphin for one possible example. Mike Turnbull (talk) 13:33, 11 January 2021 (UTC)
 * Ride on the back of a green sea turtle in the Great Barrier Reef. Alansplodge (talk) 14:22, 11 January 2021 (UTC)


 * Water skeeters (aka pond skaters) are animals that know how to ride the wave. (Video: .) Whirligig beetles are perhaps swimming, but such that they skim the surface. (Video: .) --Lambiam 10:45, 12 January 2021 (UTC)
 * It would take an awfully big whirligig to allow a person to ride it successfully. Matt Deres (talk) 14:49, 13 January 2021 (UTC)


 * I recall hearing of people riding swimming horses to avoid getting zapped by electric eels. I suppose if you gave the horse a flotation device you could ride it on water for longer. Zindor (talk) 12:51, 12 January 2021 (UTC)

How can Perseverance (rover) can land on Mars before Tianwen-1 rover?
Tianwen-1 was launched before Perseverance (rover), then how can Perseverance (rover) can land on Mars before Tianwen-1 rover? Rizosome (talk) 15:21, 11 January 2021 (UTC)
 * I don't have a direct answer, but there are many possible trajectories, speeds, and mission profiles, and it is entirely possible that the one launched later would land on Mars itself earlier. There should be no expectation that the elapsed time for the two missions would be similar, so there should be no expectation that the earlier launched one would touchdown on Mars earlier.  They were only launched a few weeks apart; now, if it had been a decade or more there may be some explaining to do, but given the proximity of launch times and the different mission profiles, it's not that surprising.  It's like asking how I, walking along a different path than you take, can arrive at a destination at a earlier than you, who left earlier, but took a different path and walked at a different speed than me.  -- Jayron 32 15:37, 11 January 2021 (UTC)


 * "You take the high road and I'll take the low road, and I'll be in Scotland before ye..." ←Baseball Bugs What's up, Doc? carrots→ 16:00, 11 January 2021 (UTC)


 * The Tianwen-1 mission comprises both an orbiter and a lander. The scheduled arrival at Mars, defined as insertion into a Mars orbit, will be in February 2021, if all goes according to plan (according to our article). If that is before February 11th, it will have arrived earlier at Mars than Perseverance. However, the orbiter is planned to remain in orbit for about three months before sending the rover down (again, according to our article). Apart from that, spacecraft travelling to Mars are cruising (i.e., in free fall) for almost all of the time. The initial velocity is an important determining factor. On a 200-day journey, just a 1% difference may already account for two days in elapsed time, even with very similar trajectories. --Lambiam 10:30, 12 January 2021 (UTC)

Help identify a goose-like family
During these times of full (or partial) lockdown, rare encounters with the wild take place. This is the case of a bird the family of which has been captured by a camera, in the north of Tel-Aviv city in Israel, in the 1st week of Jan (see the attached picture). Tried to identify it, but except for its goose-like appearance, I'll be glad to have a more professional identificaion. Thanks. בנצי (talk) 20:02, 11 January 2021 (UTC)
 * I suggest that the Egyptian goose (a somewhat variable species) fits the bill. {The poster formerly known as 87.81.230.195} 90.200.40.9 (talk) 20:09, 11 January 2021 (UTC)
 * I agree. Of all the geese listed at List of birds of Israel, the Egyptian goose is the only one with any resemblance to the birds in the image. (It's worth noting that our article states that the Egyptian goose is more closely related to shelducks than geese, but it looks like a goose, hence the common name). PaleCloudedWhite (talk) 20:20, 11 January 2021 (UTC)

Reflexive gasp
Sometimes while falling asleep I make reflex-like quick inhalation (gasp) through nose, similar to yawning for extra oxygen. Possibly this has to do with slower/shallower breathing while sleeping, so perhaps other people have this too. Is there a name for such non-voluntary nasal gasps? For the record, I'm healthy and not seeking a medical advice. 212.180.235.46 (talk) 20:37, 11 January 2021 (UTC)
 * How do you know you don't need medical advice? ←Baseball Bugs What's up, Doc? carrots→ 21:32, 11 January 2021 (UTC)
 * Ignore him. It's a well-known thing, perfectly normal. See hypnic jerk, aka hypnagogic jerk. --  Jack of Oz   [pleasantries]  22:14, 11 January 2021 (UTC)
 * I've experienced that myself. While not seeing a doctor about it, I also haven't sought the advice of unqualified internet users. ←Baseball Bugs What's up, Doc? carrots→ 23:25, 11 January 2021 (UTC)
 * Neither was the OP seeking advice. In case you missed the small print, he said: "For the record, I'm healthy and not seeking a medical advice". --  Jack of Oz   [pleasantries]  05:13, 12 January 2021 (UTC)
 * Sure. ←Baseball Bugs What's up, Doc? carrots→ 09:22, 12 January 2021 (UTC)
 * WP:AGF. --OuroborosCobra (talk) 20:14, 12 January 2021 (UTC)
 * Sure. ←Baseball Bugs What's up, Doc? carrots→ 22:26, 12 January 2021 (UTC)
 * While hypnic jerks are a plausible explanation, still, without examining the questioner, how can we be sure this is not a symptom of an illness like obstructive sleep apnea? Many sufferers of mild forms of sleep apnea do not experience excessive daytime sleepiness or other tell-tale symptoms and are not aware of the condition. --Lambiam 09:41, 12 January 2021 (UTC)
 * It's not for us to be diagnosing - or even suggesting - problems, particularly where the OP denies there's a problem. Our self-imposed limitation on providing medical advice includes diagnosis of symptoms.  --   Jack of Oz   [pleasantries]  21:26, 12 January 2021 (UTC)
 * Indeed. Wouldn't that include replying, "It's a well-known thing, perfectly normal."? --Lambiam 08:17, 13 January 2021 (UTC)
 * Well, it is a well-known thing, so much so that we have a whole article on it. "Perfectly normal" is my precis of "Hypnic jerks are common physiological phenomena.[5] Around 70% of people experience them at least once in their lives with 10% experiencing it daily.[6][7] They are benign and do not cause any neurological sequelae.[7]" --   Jack of Oz   [pleasantries]  22:33, 13 January 2021 (UTC)
 * Suppose someone asks: "I have bumps all over my skin, should I see a doctor?" Can we answer then, "No, don't worry; these are goose bumps, a perfectly normal common physiological phenomenon"? How would we know, without examining them, that the questioner's bumps are goose bumps? Likewise, how do we know that this questioner's gasps are indeed hypnic jerks? It is plausible, but without further examination we cannot be sure. --Lambiam 13:01, 14 January 2021 (UTC)
 * I take your point. The OP is welcome to read the link I provided, and if that doesn't sound like what he's experiencing, and he's still concerned, he should consult a medical practitioner. --  Jack of Oz   [pleasantries]  21:23, 14 January 2021 (UTC)

As the name implies, sleep apnea happens when you're sleeping, not when you're falling asleep. Snoring is a common form of apnea. 2601:648:8202:96B0:0:0:0:313A (talk) 03:25, 14 January 2021 (UTC)
 * Snoring is not a form of apnoea. If air is passing through the larynx sufficient to make a noise then apnoea is not occurring. I suspect you are referring to the fact that a person who snores may be at risk of sleep apnoea. Richard Avery (talk) 12:33, 14 January 2021 (UTC)