Wikipedia:Reference desk/Archives/Science/2016 May 31

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May 31

Mathematical expression for buyoancy or upthrust

After a number of steps we get the equation: 'Upthrust(U)= vdg' but in the next step we come to 'U= mg' but volume is of the submerged body and density is of liquid, then how can we show that 'vd=m' ? 49.126.255.55 (talk) 02:43, 4 June 2016 (UTC) — Preceding unsigned comment added by Sahil shrestha (talk • contribs) 02:22, 4 June 2016 (UTC)

What is this flower?

This was taken near the Angeles Crest Highway, but I have seen it other places in California, usually in semi-arid mountainous territory at relatively low elevations. It grows on a sort of green shrub, and has a sweet perfume.

It looks like Common Broom (Cytisus scoparius) - a European native which has been introduced and is becoming a nuisance in parts of the western USA. To be certain I would need to see the whole shrub, not just a close up of the flower, as lots of the legume family have quite similar flowers. 86.191.126.192 (talk) 07:51, 31 May 2016 (UTC)

Looks more like Spanish broom to me. Like you say - hard to tell without more pics. [| Google ] 196.213.35.146 (talk) 13:58, 31 May 2016 (UTC)

Spanish Broom looks like a winner. Thanks, all. --Trovatore (talk) 18:04, 31 May 2016 (UTC)

Resolved

serotonin and sleep are directly proportional or inversely?

knowledge should occur fasterFAMASFREENODE (talk) 09:00, 31 May 2016 (UTC)

Not exactly either. The direct effect of serotonin is to promote wakefulness, but if it is taken early in the day, it tends to improve sleep during the following night. Looie496 (talk) 17:27, 31 May 2016 (UTC)

. --Jayron32 02:59, 1 June 2016 (UTC)

because the liver converts serotonin into 5-hiaa, can reduced level of 5-hiaa and increased serotonin occur in impaired liver by hepatitis?

true knowledge should be discovered quickly in universeFAMASFREENODE (talk) 16:05, 31 May 2016 (UTC)

Florida Alligator able to survive in Burma?

After dealing with someone whose said that the US should get back at Burma for sending the pythons over here (yes, my head hurt), by sending our alligators over there, I started wondering. The two species of alligators *definitely* have ranges north of the crocodiles (overlap in south Florida between the American Alligator and the Crocodiles, unsure whether there was ever overlap between the Chinese Alligator and the Siamese Crocodile), but the main populations of Crocodile in Burma appear to be the Mugger Crocodile and the Saltwater Crocodile, both of which tend more toward saltwater. However the Burmese Python's range appears to go all the way up the Irrawaddy, so I'm wondering whether the Alligator could survive on the upper Irrawaddy and Chindwin.Naraht (talk) 20:00, 31 May 2016 (UTC)

Look first at niche, then at competitive exclusion principle. Basically, there are already scarier monsters there that will eat the young of and outcompete the adult American alligators. There is also the fact that "threatening" a country that has the saltwater crocodile with the American alligator is like threatening the use of . . . The Comfy Chair!. Finally, what if the Burmese were to respond by sending crates of cobras to the Southeast and mambas to the Southwest?

Crocs appear to be able to survive in quite different climates from where they originated from. One only has to look at those that have kept them as pets. The bigger problem though (as I see it) is whether they can successfully breed. They lay eggs and the egg nests have to have the right conditions for the eggs to mature and hatch. --Aspro (talk) 21:21, 31 May 2016 (UTC)

About six weeks ago, this journal article showed up in Herpetological Conservation: Molecular Analyses Confirming the Introduction of Nile Crocodiles, Crocodylus Niloticus Laurenti 1768 (Crocodylidae), in Southern Florida, With an Assessment of Potential for Establishment, Spread, and Impacts...

It's one data point that illustrates that crocodilians can adapt to other geographies. Florida is a very biodiverse place, home to American alligators, American crocodiles, and now ... Nile crocodiles. I suspect that similar transplantation of an American alligator or crocodile could yield a self-sustaining invasive-species population in many other parts of the world.

Nimur (talk) 21:56, 31 May 2016 (UTC)

OP:Sort of responding to all... The place that I'm asking about is farther up the Irrawaddy than either of the Burmese Crocodiles go, so they aren't in direct competition. Upstream is both freshwater, which the Alligators are just fine with and cooler (and the Alligator appears to dominate the Crocodile in colder weather. Not sure if Burma has any animals more able to disturb Alligator nests than you would find in North America, the Burmese Python doesn't appear to go directly after nests. The temperatures seem fine for the production of both genders based on egg temperatures.Naraht (talk) 01:03, 1 June 2016 (UTC)

Well, then, again, the competitive exclusion principle would be relevant. If the alligators can survive where the crocs can't, then the alligators will survive where the crocs can't. It still seems a bit comfychairish, and the cobra/mamba threat still exists. μηδείς (talk) 03:54, 1 June 2016 (UTC)

@Medeis: Thanks, the Mamba is an African snake, so Burma doesn't have any. (And all except the Black Mamba are probably too arboreal for the Southwest USA). OTOH, I think the Monocled Cobra and the Mandalay Spitting Cobra would do just fine in the Southeast. North America definitely came up short when it came to poisonous snakes (and spiders) compared to the rest of the world.Naraht (talk) 18:16, 1 June 2016 (UTC)

When you have a question that asks about "getting back at Burma" it kinda implies bioterrorism. In that case, sending Black Mambas to Southern California (many parts of which are green and treeful) seems like a workable attack, even if the Burmese would have to ultimately get the snakes from South Africa. Given the premise of your question was not based on indigenosity, there seemed to be no need for my answer to be even stricter. μηδείς (talk) 01:36, 2 June 2016 (UTC)

indigenosity ?? AllBestFaith (talk) 13:45, 2 June 2016 (UTC)

Apparently a real word; Indigenosity, Aboriginality, and the Dubious Concept of Indigenization ;-) Alansplodge (talk) 18:17, 2 June 2016 (UTC)

Purportedly so. Φοβοῦ τοὺς Δαναοὺς καὶ δῶρα φέροντας. AllBestFaith (talk) 18:53, 2 June 2016 (UTC)

Timeo Danaos et dona ferentes The Quixotic Potato (talk) 06:23, 4 June 2016 (UTC)

Severed corpus callosum experiment

in this video : https://www.youtube.com/watch?v=lfGwsAdS9Dc at around 5:30, the subject is flashed two words BELL and MUSIC to his right and left hemisphere.

in the earlier experiments it is shown that the two hemispheres cannot communicate, when the left speaking hemisphere is flashed a word it can then vocalize which word it saw, but when the right brain saw a word flashed on the left side it could not vocalize it, it could only draw it.

But then when shown BELL on the left and MUSIC on the right, he is told to pick one picture out of 4 and he picks a BELL and his explanation is MUSIC and then he goes on to describe how he heard bells earlier and then they talk about how great it is that the left brain has to come up with rationalizations of it's choice.

doesn't this latter experiment show that the brains can still communicate? And if your hypothesis was that the two halves cannot communicate wouldn't you expect him to not pick the BELL since his right brain can't share with him that information. Is this only because they made him pick with his left hand? I would have liked to seen what happens when the two words aren't as closely related.

2601:406:4C01:5480:2467:E302:30E:5586 (talk) 21:52, 31 May 2016 (UTC)

The corpus callosum isn't the only thing linking the two halves of the brain. It doesn't explain at corpus callostomy or split-brain, but there are five commissures, of which this is just one (but the largest). There is also the somewhat mysterious interthalamic adhesion, though the thalamus apparently connects more via the posterior commissure. Bear in mind that the cerebral cortex that the CC links together is a vast portion of the brain that handles all manner of specifics, but it is kind of an add-on, in the sense that it has been massively expanded but isn't really a brain in and of itself. The thalamus and other non-cortex parts of the brain are more fundamental to consciousness per se, I think. Wnt (talk) 23:16, 31 May 2016 (UTC)

[EC]The experiment shows that there IS "some" level of communication, but only at a subconscious level. Our article is Split-brain, it's a very complex subject which is not yet very well understood. if you find this stuff fascinating, I can wholeheartedly recommend the works of Oliver Sacks, start with The Man Who Mistook His Wife for a Hat. Vespine (talk) 23:19, 31 May 2016 (UTC)

A subject area you might like to research is Laterality. There is some really interesting stuff on animals which look at strangers with one eye, but at familiars with the other. DrChrissy ^(talk) 13:07, 1 June 2016 (UTC)

Physics area-Conical Pendulum- Search for modern uses

If a conical pendulum can move and be maintained at a constant speed with no energy input causing such movement, what are the practical commercial purposes to which such resultant movement of /force generated by the pendulum can be put. ?

In a non scientifically controlled environment, it would appear that the above anomalous outcome of movement of the pendulum without application of force can be achieved. 165.228.196.113 (talk) 23:40, 31 May 2016 (UTC)

If you have a perpetual motion machine, great! The catch is, you don't. You'd have to cite the specific circumstance, but there must be some subtle power input. There are many ways in which this can happen, because the total amount that needs to be input is so small, just enough to oppose the friction of the bob going round and round in the air. For example, electromagnetically pulling the bob at one point (or several) to keep it in time would work. Not quite the same thing, but you may have seen Foucault pendulum demonstrations where the pendulum never runs down, because they have some gizmo that pulls on it somehow, ideally without disturbing the overall rotation of motion in that case. Wnt (talk) 00:38, 1 June 2016 (UTC)

We have an article for Conical pendulum and circular motion, there is no "anomalous movement" as far as I can tell. You can not get the pendulum to start swinging without energy input. It is true once it is swinging, it will maintain a constant speed without energy input, but that's due to Newton's laws of motion. In practice, on earth, just like a thrown ball or a car when you release the accelerator, a pendulum WILL eventually slow down due to air resistance and small frictional forces in the string, but a well designed pendulum where those forces are minimized can swing for a very, very long time, it can SEEM like it's not slowing down at all, but for all practical purposes, (unless you work at CERN or NASA) there's no exceptions to Newton's Laws. Vespine (talk) 02:06, 1 June 2016 (UTC)

The main force that acts to stop the pendulum is gravity, not air resistance or frictional forces in the string. Each time the pendulum swings left or right, gravity acts to bring it to the downward position, and gravity always wins. Akld guy (talk) 02:35, 1 June 2016 (UTC)

But all things being equal, the force required to accelerate the pendulum up to a certain point is precisely the force imparted on it on the journey down. And in a conical pendulum, there is no downward movement anyway, it's effectively an "orbit". Vespine (talk) 02:58, 1 June 2016 (UTC)

So that it's not ambiguous, I am saying it IS the string and the air, and NOT gravity. One relavant article is Simple harmonic motion. Without friction, but WITH gravity, a simple oscillator would continue forever. Vespine (talk) 05:43, 1 June 2016 (UTC)

But that's not what you said and it's not what I commented on. You said, "In practice, on earth, ..., a pendulum WILL eventually slow down due to air resistance and small frictional forces in the string, ...". My comment was that [in practice], gravity is the main influence that stops the pendulum. Not air resistance or string tensions. Akld guy (talk) 20:33, 1 June 2016 (UTC)

@Akld guy you are contradicting Vespine who is in no way being impractical. Gravity is needed for a hanging pendulum to operate and can be irrelevant to a conical pendulum. To call an agent responsible for slowing a pendulum, you have to explain how that agent disposes of the kinetic energy that is stored in the pendulum. Air resistance and string friction both convert motional energy to heat but gravity cannot do that. AllBestFaith (talk) 13:41, 2 June 2016 (UTC)

None of what you said is in dispute with what I said, except that you seem to have inferred that I meant that air resistance and string tensions are irrelevant. I said no such thing. They are factors in bringing the pendulum to a stop, but the main factor is gravity, which both makes the pendulum swing to and fro and also eventually brings it to a stop, since the effect of its force is far greater than the forces brought to bear by air resistance and string tensions. In other words, gravity is the dominant force, exactly what I said. Akld guy (talk) 21:37, 2 June 2016 (UTC)

@Akld guy now would be a good time to listen rather than expend more bold text on your philosophical notion that defies the fact that gravity keeps a friction-free hanging pendulum swinging indefinitely, that being an example of a mechanical dynamic equilibrium like an Orbit. Your insistance on being right is becoming disruptive to answering the OP about conical pendula that are by construction immune to gravity. AllBestFaith (talk) 16:39, 3 June 2016 (UTC)

Where did you get the notion that the Conical pendulum is immune to gravity? The article says no such thing. The question posed by the OP assumed that gravity had no effect, but he/she was mistaken and was corrected by User:Wnt who stated that you can't have a perpetual motion machine. Akld guy (talk) 22:07, 3 June 2016 (UTC)

@Akid guy I apologise for not clarifying earlier my thought in which a "conical pendulum that is immune to gravity" equates with the Balance wheel on which we have an article. The OP's post says nothing about gravity. The effect of Wnt's correct post is that the OP's words "be maintained at a constant speed with no energy input" should be expressed as "be maintained at a constant speed by a small power input to replace losses so that there is zero nett energy loss or gain". Vespine's also correct post identifies the practical energy losses and adds Wikilinks, most notably to Newton's laws of motion. It belongs to pre-Newtonian superstition to suppose that gravity expresses a "will" i.e. that heavy objects (such as rocks) want to be at rest on the Earth and that light objects like smoke want to be at rest in the sky and the stars want to remain in the heavens. Clinging to that notion with a dogma that "gravity always wins" is at worst a nihilist assault on good Vespine and at best an unverifiable cosmological prediction. AllBestFaith (talk) 13:35, 4 June 2016 (UTC)