Wikipedia:Reference desk/Archives/Science/2017 March 29

= March 29 =

Why do boring things put humans to sleep?
On the airplane, human passengers may get bored and sleep. In a classroom, bored students sleep. Counting sheep supposedly puts humans to sleep. Watching grass grow is a long process with little stimulation, so it may put humans to sleep. Why do humans need constant mental stimulation? In the absence of stimulation, why do people feel bored and sleep? Do ADHD individuals need more mental stimulation than the general population? 50.4.236.254 (talk) 04:23, 29 March 2017 (UTC)


 * Sleep is a good thing to do when nothing else important is happening. I don't believe this to be unique to humans. StuRat (talk) 04:27, 29 March 2017 (UTC)


 * I didn't say this is unique to humans. I only asked, "Why do boring things put humans to sleep?" to narrow down the scope. 50.4.236.254 (talk) 04:45, 29 March 2017 (UTC)


 * Interestingly, stimulation also can trigger sleep, but that is in the context of narcolepsy. PaleoNeonate (talk) 05:18, 29 March 2017 (UTC)
 * Also, intense fear may sometimes have the same effect. 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 12:45, 29 March 2017 (UTC)
 * After checking out our boredom article, it does not seem totally useless, and says more than what we could say here. Have you read it?  PaleoNeonate (talk) 05:35, 29 March 2017 (UTC)


 * Because we need to sleep. Most people don't get enough sleep, if they don't engage in an activity that the brain will flag as important, it will start up the sleep mode. If the brain were not prone to doing this, then you'd have difficulties falling asleep when lying in bed. Count Iblis (talk) 08:06, 29 March 2017 (UTC)

Soyuz spacecraft on Zenit rockets
Apparently, there was a plan for the Soyuz spacecraft to be launched on the Zenit rocket instead of the Soyuz rockets beginning in the 1990s, but this plan fell through after the collapse of the Soviet Union; the fact that the rocket would now be a Ukrainian property didn't help matters either. However, I can't find any mockups or pictures of this configuration online. Do such images exist? Narutolovehinata5 tccsdnew 04:42, 29 March 2017 (UTC)
 * I've never heard of a proposal for Soyuz on Zenit (but I'm only an interested amateur). Is it possible you're thinking of Zarya_(spacecraft)? That was a proposed Soyuz successor, to be launched on Zenit . Fgf10 (talk) 07:20, 29 March 2017 (UTC)

Tubular structures on Mars
I came across several pages of pseudoscience junk on the internet about how some odd ribbed tubular structures clinging to the side of a canyon on Mars is evidence of intelligent life. Some of them included the NASA image title "M04-00291", which I eventually found on Google Earth (in Mars mode with the MOC image browser enabled). The coordinates on Google Mars are 38&deg;46'N 26&deg;47'W. Google Mars indicates that the Mars Orbiter Camera actually made three passes over that spot: These don't look artificial to me, they look more organic. In fact the first thought that came to my head when I saw the image was "giant crinoid fossils!" Highly unlikely though, as these structures look like kilometers in length.
 * http://viewer.mars.asu.edu/planetview/inst/moc/M0400291 - the original image from August 1999 that spawned all the pseudoscience articles. Zoom in on the upper right corner.
 * http://viewer.mars.asu.edu/planetview/inst/moc/E2000892 - acquired 3 years later in September 2002; the feature is in a corrupted area of the image though.
 * http://viewer.mars.asu.edu/planetview/inst/moc/E2101421 - acquired October 2002; zoom in on the right middle. The feature in the first image that looked like a glowing translucent swelling now looks like a crater that squashed and flattened the tube structure on impact.

Try as I might, I have never found any 'official' explanation or hypothesis of these structures. Clearly they must have been interesting to NASA, otherwise they wouldn't have taken three separate images. I wish there were a filter on Google for "reliable sources only" to get rid of all the junk in search results. Even Google Scholar was no help, although the only result it gave me included another similar image: http://viewer.mars.asu.edu/planetview/inst/moc/M1501228

The best source so far, which still seems rather speculative, is an essay by a geologist trying to assess known geological processes to account for the structures. In his addendum, he doesn't buy the "sand dune" hypothesis. I must admit that if they're sand dunes, I'd expect to see more of an angle of repose in the structures, not something that looks like it's clinging to a vertical wall.

Does anyone know of an explanation that we might have an article about? ~Anachronist (talk) 16:47, 29 March 2017 (UTC)


 * How about a lava tube, where the top has eroded away, exposing the interior ? I can't explain the evenly-spaced rings inside the tube, though.  Would cooling of magma/lava cause something like that ?  Perhaps the lava/magma would retreat in steps, forming a ring at each step ?  StuRat (talk) 17:35, 29 March 2017 (UTC)


 * Science Fiction author Ben Bova explores the possibility these structures were intelligently made in several of his Grand Tour books, Mars and Return to Mars come to mind. Still, these are fiction.  I am not aware of any serious scientific speculation that the structures are of intelligent creation.  -- Jayron 32 17:36, 29 March 2017 (UTC)


 * Yeah, my next thought after "crinoid" was "lava tube" but I have no idea about the strange ribbed appearance. I suppose if it was once a molten substance that shrinks dramatically when cooled, it might form rib-shaped cracks like that. Other pictures from Mars that have been positively identified as lava tubes don't have those features though.
 * I know, most of the stuff I found online was similarly fiction; the only difference is Ben Bova knows it's fiction, while most of the other pages I found came from "true believers". ~Anachronist (talk) 17:43, 29 March 2017 (UTC)


 * The image "E21-01421" which you linked describes the formation as a "trough with small bright bedforms" see the Wikipedia article on bedforms. It seems bedforms are caused by fluid flowing over a surface, as for what caused these bedforms it could have been liquid water or it could have been an ancient atmosphere or something else entirely. 208.90.213.186 (talk) 18:26, 29 March 2017 (UTC)


 * This is presumably a large feature, but it looks eerily like a fossilized facehugger alien at the humanoid stage, there's a head at the top of the trunk in the middle of the top of the image looking to our left, with the arm to our leftpointing to 8 o'clock, and the right one up to one o'clock. Definitely biomechanical in the style of H. R. Giger.  I'll have to suffer through Prometheus (film) again.μηδείς (talk) 01:17, 30 March 2017 (UTC)


 * If you want to go with a sci-fi alien, how about the (possibly organic) 3-legged vehicles the Martians used in War of the Worlds. Here's one illustration, featuring 3 legs, with cross-sectional circles shown on one: . StuRat (talk) 04:10, 30 March 2017 (UTC)


 * "Good God!" as Watson would say. Amazingly organic-looking for the result of some geological process. Edison (talk) 03:55, 30 March 2017 (UTC)

I don't know the geology, but just looking at images online there are some lava tubes that seem to have small regularly spaced ridges:  That said, even the best case I found wasn't very impressive - it isn't really feasible to see it with a collapsed tube because it would have long since eroded, and in the case I found there are railroad tracks for which I assume ridges were smoothed out where they pass through on the lower surface? It would be nice to hear an informed opinion here! Wnt (talk) 17:33, 30 March 2017 (UTC)

Have none of you seen Dune? - they're obviously the remains of sandworms. Richerman   (talk) 09:33, 1 April 2017 (UTC)

How does a LyfeLite bulb know when the power is out ?
See their web site. These are emergency backup bulbs that screw into a normal light bulb socket, charge a battery, and power the bulb from that when they detect that the power is out. The obvious flaw in this plan is that power to the socket being out might either be caused by power to the house being out or by the light switch being flipped to OFF. Their web site states: "The LyfeLite Emergency LED bulb is also intelligent enough to recognize when your light switch is on or off, so you can still control it by using the switch during a power outage." I'm rather skeptical. How can it tell the difference ? One thought is that the longer circuit when the switch is ON, during a power outage, would lead to more transient (radio ?) signals being picked up by the wire acting as an antenna, but this hardly seems like a reliable method, as the strength of those signals would depend not only on the distance to the light switch (and break in the circuit, during a power outage), but also due to the amplitude and frequency of signals being broadcast in the area. In a widespread power outage, those signals might be reduced, too. StuRat (talk) 21:13, 29 March 2017 (UTC)


 * Their kickstarter page is .--Llaanngg (talk) 21:56, 29 March 2017 (UTC)


 * That kickstarter page is for a completely different product. It has a similar name, but is spelled differently.  CodeTalker (talk) 23:31, 29 March 2017 (UTC)


 * Some kind of voltage sensor sensing the voltage across the mains, and turning on the battery when the voltage is zero? 2601:646:8E01:7E0B:F88D:DE34:7772:8E5B (talk) 00:02, 30 March 2017 (UTC)


 * Wouldn't the voltage also be zero when the switch is turned OFF ? StuRat (talk) 07:17, 30 March 2017 (UTC)


 * Perhaps capacitance monitoring? When a switch is off the capacitance of the wire would be low (relatively short wire to the switch); when the switch is open, but the power is off, capacitance would be higher. That might be implemented with a capacitor in the bulb, then monitor the fall in charge when switch thrown (or power lost). Speculating ... Klbrain (talk) 00:36, 30 March 2017 (UTC)


 * Woah, that's a weird company. You literally can't find out anything about them or their products. Their phone numbers and web address are anonymized, and their physical address appears to be rented industrial warehouse, so you can't find out from that either. There's nothing about them really on their website, no real information on how the technology works, and their internet presence is virtually nill. You can find a business registration for them, so if they've gone that far it's probably not a total scam. But I also find no US patents or applications that use the word "lyfelite" anywhere, or have been granted to either of the two persons listed in the business registration. It's all very weird for what seems like such a cool light bulb! Someguy1221 (talk) 00:48, 30 March 2017 (UTC)


 * Sockets (commercial grade ones) for sustained luminaires have four connections (live, neutral, switched, earth) for just this reason, rather than the usual three (switched, neutral, earth).
 * I would hazard a guess that this lamp is not sustained, but is simply a lamp with a battery on-board. It turns on when mains is supplied, and it can be turned on (but doesn't do this automatically) if mains power is lost. If power goes out and the bulb wasn't turned on at the time, it doesn't light up spontaneously (as a sustained luminaire does). How to implement this? - maybe by sensing the impedance across the supply, when there is no voltage on it. It's a fair bet that this is a low impedance, because there will still be a load device connected, even if the power is off. Andy Dingley (talk) 01:03, 30 March 2017 (UTC)


 * Here's their TV commercial, where they claim (about 50 seconds in) that "When the power goes out, LyfeLite kicks on automatically !", accompanied by light going out, then coming back on a second later: . So, that might be clue, that there's a one second timer needed to determine that there is a power outage. StuRat (talk) 04:20, 30 March 2017 (UTC)

Note that I also looked online for reviews, hoping somebody would describe how they work, or at least how well they work. No luck. StuRat (talk) 03:55, 30 March 2017 (UTC)
 * I found some online reviews for a same-sounding product, "Everbright" from Sengled. They report that it works as advertised, as a drop-in replacement for a normal bulb in a normally-wired and -switched socket. Some observations include:
 * Turning off the switch for the socket turns off the bulb, but popping the circuit breaker keeps it on.
 * Having other bulbs controlled by the same switch makes the switch no longer able to turn the bulb off.
 * Those two strongly suggest it has something to do with how much wiring is connected to the hot side when there is no power applied. DMacks (talk) 07:53, 30 March 2017 (UTC)
 * So if "Turning off the switch for the socket turns off the bulb" how does it also "When the power goes out, LyfeLite kicks on automatically", implying that it does so when still switched off? I can see arcane ways to make a bulb behave like this technically, but I can't see past the human factors of giving users a bulb they can usefully control. If I need a sustained light for my stairs etc., the last thing is one that I need to have an argument with in order to convince it that I want it on right now. Andy Dingley (talk) 10:12, 30 March 2017 (UTC)


 * Something to do with being connected to a "long" but unpowered wire. Maybe Parasitic capacitance? DMacks (talk) 13:43, 30 March 2017 (UTC)


 * No, if it was switched OFF when the power died, then it would stay off until the switch was turned to ON. It only comes on automatically if the switch was in the ON position when the power died, as their TV ad showed. StuRat (talk) 16:07, 30 March 2017 (UTC)


 * It only comes on automatically if the switch was in the ON position when the power died, as their TV ad showed. - (emphasis added). I have not watched the ad, but I strongly doubt any company would devote ad time to showing their products not working. So, there is a good possibility that the switch off - cut power - switch on sequence turns the bulb on, since that is what would happen if the above explanation (the bulb sensing wire length via capacitance or something) is correct.  Tigraan Click here to contact me 16:17, 30 March 2017 (UTC)


 * They do say, at their web site: "The LyfeLite Emergency LED bulb is also intelligent enough to recognize when your light switch is on or off, so you can still control it by using the switch during a power outage". StuRat (talk) 16:22, 30 March 2017 (UTC)


 * My first guess was that it was a kind of Emergency light, but these are not wired and switched like a normal bulb.
 * Another option is that it's connected to a router (or similar device like Bluetooth) and when this goes off, it turns on. :And let's not forget that it could be some sort of scam, where they offer you some product with magical properties. Hofhof (talk) 13:29, 30 March 2017 (UTC)


 * For most kinds of power outage, if the light switch is on, there will be a DC path from the switched wire to neutral through the winding of the transformer that supplies power to the house. If the light switch is off, there will not be any DC or low-frequency path from the switched wire to neutral. I have no idea if this product uses this characteristic to decide when to use the battery to illuminate the lamp. Jc3s5h (talk) 17:17, 30 March 2017 (UTC)


 * I do not see the following point mentioned above, so I'll mention it even though it is late in the conversation...
 * There are three wires involved: Hot, Neutral, and Ground. If you put the switch for the light on ground, the light will always remain on and never turn off. If you put the switch on either hot or neutral, the light will turn on and off with the switch. So, it is guaranteed that the light switch is on either hot or neutral. It won't be on both. If it is on neutral, it would be trivial to measure a voltage difference between hot and ground. It will be 120VAC in the United States. If the switch is on hot, you might assume that there would be no difference between neutral and ground. That is not correct. Some electrical equipment requires neutral to be very close to ground - less than 0.5VAC. It takes a lot of work to get neutral that clean. A normal circuit won't be that low. But, even if it was just 0.5VAC on neutral, it would still be trivial to measure a voltage difference between neutral and ground. When power goes out, the voltage difference vanishes. There's no voltage on any of the lines. So, measuring the voltage difference between either one of the power wires and ground would be a simple way to detect that power has gone out. 209.149.113.5 (talk) 18:03, 30 March 2017 (UTC)


 * I am a bit confused by this, as the cords going to lamps in the US don't have 3 wires, but only 2, omitting the ground. Other appliances have all 3 wires. StuRat (talk) 18:12, 30 March 2017 (UTC)


 * A table lamp may be two wire, but every built-in light in my house is three-wire. All of the built-in lights in my old house are three-wire. All the lights where I work are three-wire. My assumption is that the device is for built-in lights, not for table lamps. Even those have regulations now. Metal lamps are supposed to be grounded. I still find a lot that aren't as it is my job to monitor for electrical issues and by code, we cannot have ungrounded metal lamps anywhere in the hospital. 209.149.113.5 (talk) 18:25, 30 March 2017 (UTC)
 * Amendment... I just checked neutral to air on an electrical outlet. No hot. No ground. It has a measurable voltage and a distinct 60hz frequency. So, even without ground, it is trivial to identify that there is power on a "dead" line. It is simply hard to get rid of all the electricity. It tends to trickle here and there all over the wires. 209.149.113.5 (talk) 18:28, 30 March 2017 (UTC)


 * It should be quite easy to tell if the switch is "on" or "off". The receptacle has two (relevant) wires: "hot" and "neutral." The neutral wire is always connected back to ground at the fuse box. The "hot" wire is disconnected (when the switch is off) or connected back through the fuse box to one side of the secondary winding of the transformer on the pole (or wherever) outside your house. The other side of the secondary winding (or the center tap in a split-phase system) is connected to neutral (and to ground). This means that when there is no power on the primary (i.e. in a power failure) The measured DC resistance between the "hot" and the "neutral" will be quire low (a few ohms) if the switch is closed, and will be very high (>100K ohms) when the switch is off. You can verify this the next time your power goes out. When there are multiple switches, the two wires in at the light may change roles depending on the switch settings, but the effect is the same: the resistance will be low if the light is supposed to be on and high if the light is supposed to be off. There is one type of power failure That will fool these lights: if your house becomes disconnected from the transformer. This occurs if a tree falls on your service wire or if the fire department pulls your meter. The light would also NOT come on if a breaker (branch or main) trips. -Arch dude (talk) 03:38, 1 April 2017 (UTC)


 * Sounds good, but DMacks said the 'same-sounding product, "Everbright" from Sengled', does come on when the circuit breaker pops. So, it sounds like it must be using a different method. One of the reviewers here assumes that that product uses the DC path to determine if the switch is ON or OFF: .  StuRat (talk) 05:03, 1 April 2017 (UTC)

Is this technology "adaptive" ?
Follow-up Q: Since it seems to be using some aspect of the length of the connected open circuit to determine if the breaker is flipped or the switch is off, this then makes me wonder if they could handle places where there's a long distance to the switch, like say a restaurant, or a short distance to the breaker, like an apartment. These distances may well overlap. Could it measure the "normal" states by you turning the switch on and off, while there is power to the system, during installation, then use that to determine when the system is in the abnormal state (breaker flipped OFF or power outage) ? StuRat (talk) 16:36, 30 March 2017 (UTC)
 * it could measure the distance to the break and then just do min/max or some other heuristic. there are Ethernet cable testers with a "distance to fault" function. They do it by measuring the time between a signal and its reflection - HF signals are going to reflect off the end of an unterminated line. if that is indeed how it's done, which I don't know - my first idea was what Jc3s5h suggested above (DC path), but since you say it can tell between someone flipping the switch and the circuit breaker popping... terrific question... Asmrulz (talk) 22:55, 30 March 2017 (UTC)


 * The suggestion above that AC voltage may be measurable even though the light switch is turned off is just one possible way to do this. Looking for a broken line is another. The tool is usually called a TDR (time-domain reflectometer). They are bulky, but I'm sure someone could make a tiny one. In my opinion, making a tiny voltage sensor is cheaper and easier, so I assumed that is what they were doing. 209.149.113.5 (talk) 14:53, 31 March 2017 (UTC)

Radio signal around the world
Can an amateur radio signal travel around the world and come back to its origin? That is, without a repeater along the way. I suppose some kind of radio signal should be able to go all the way through, but I wonder how much power it requires. --Llaanngg (talk) 21:47, 29 March 2017 (UTC)


 * Here's a research paper from my old friends, ''Multi-hop whistler-mode ELF/VLF signals... (2004). The antenna array is quite large, but the signals propagate quite far, to the geomagnetic conjugate hemisphere (for lay-persons, that's pretty much "around the world" without a repeater).  The mode of radio propagation for these types of wave is "unique."
 * Nimur (talk) 22:14, 29 March 2017 (UTC)


 * This is called long delayed echo and has been known and in the literature for decades. Akld guy (talk) 00:59, 30 March 2017 (UTC)


 * Another propagation method is by reflecting short wave radio signals from the ionosphere. Also known as HF on radios. Normally in the day-time there is heavy absorption in the lower D-layer. But the lower frequencies have less attenuation. In the night, particularly at the end, ionisation is low and higher frequencies pass trhough to space. But there can be a time around sunset when a wave could travel all round the terminator of the Earth, also through sunrise regions, and come back. This results in an echo about 0.15 seconds. Graeme Bartlett (talk) 01:13, 30 March 2017 (UTC)