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Does anyone know when the Himalayas will stop rising? — Preceding unsigned comment added by 24.207.79.50 (talk) 00:13, 9 October 2015 (UTC)[reply]
According to Himalayas#Geology, the plate tectonics driving this rise are expected to continue for another 10 million years. However, the current rate at which the Himalayas are rising, 5mm per year, is unsustainable over that time period (it leads to an absurd prediction that the Himalayas will eventually rise to 37 miles in height, which is thicker than the plates themselves). So we have predictions for how long the subduction of the Indian subcontinent will continue, but I haven't seen predictions on when the mountains themselves will stop getting higher, or if they'll collapse under their own weight. Someguy1221 (talk) 00:36, 9 October 2015 (UTC)[reply]
They're constantly being eroded by wind, flowing water and ice – the bottom of the mountain rises by 5 mm, but the top is reduced slightly (on average 2 to 3 mm a year), so the actual growth is slower. Smurrayinchester 09:01, 9 October 2015 (UTC)[reply]
Also, a good earthquake could quickly knock down the height a bit. 209.149.113.94 (talk) 13:06, 9 October 2015 (UTC)[reply]
If there is significant net rise the potential for erosion increases so it's largely self-modulating.Hayttom (talk) 13:25, 9 October 2015 (UTC)[reply]
Also, the top several metres of the mountains in the Himalaya are mostly comprised of packed ice and firn, making their heights not quite so dependent on plate tectonics. Whoop whoop pull upBitching Betty | Averted crashes 19:59, 9 October 2015 (UTC)[reply]
See isostasy - as the Himalayas erode, they will continue to rise as the load is reduced and the lithosphere rebounds. This process will go on long after the collision finishes. The Rockies formed in the late Cretaceous to early Paleogene, finishing about 55 million years ago - they will be there as mountains for many more millions. Mikenorton (talk) 19:15, 15 October 2015 (UTC)[reply]
If first frost is November or October then when does plant volume peak?[edit]
As in cubic meters of organisms per acre.
Google says deciduous trees only grow a few months a year, so they must peak for an extended period until they start losing leaves. Species like maples might slowly decline for months as they seem to start losing seeds early. Do some weeds that are annuals grow until frost kills them, even if it's once in 30 years late? Or is a period of no growth (besides seeds) a normal part of annual weeds' lives? Are there any rules of thumb like grasses growing the latest or trees stopping growth earlier than bushes? Are there any common humid continental annuals in nature that shrink (besides seed or fruit loss) before frost hurts them? (possibly to cannibalize less vital anatomy for resources to make seeds?) Sagittarian Milky Way (talk) 09:24, 9 October 2015 (UTC)[reply]
Bottom panel: Seasonal cycle in atmospheric CO2 is driven by terrestrial NPP in the northern hemisphere. This is very interesting stuff! However, I don't have much time today to give a full account. You can ping me next week if you want more refs. First, plants age through senescence. Most grasses and deciduous trees do retranslocation. Sadly we don't seem to have a good WP article, see e.g. these research articles [1][2][3]. What this means is that much of the N and other nutrients is pulled out of the leaves before they fall or die back. This also applies to most annual weeds, and retranslocation starts to happen well before first frost.
Better graph showing how NPP draws down atmospheric CO2. In this case for Harvard Forest, peak biomass should occur sometime in June.The timing is always a bit of a guessing game, and many ruderal plants have indeterminate growth. Plants take cues from photoperiod, temperature, moisture, and even the color of light to "decide" when to do certain things like germinate, set seed, senesce, etc. So sometimes a freak early frost will kill green plants, and sometimes if the frost comes late there will be a few plants that took the risks to hang on longer. The study of plant phenology is vast and currently fairly in vogue, in part because climate change is mucking things up, and when plants and animals follow different cues events that used to match up no longer coincide, and lots of things die. Identifying exactly which cues which plants and animals use is tough, and there's almost always considerable variability within species. As an anecdote, I worked at a lab once where they studied Carduus as a model species. The plants are described as facultative biennials or short-lived perennials. They normally set seed in the fall, form rosettes, over winter, then bolt the next year, if they have the right amounts of light, water, and nutrients. But in odd conditions, they can live for over 12 years!
Now, as for plant volume - that will be hard to find - most systems ecology discusses things in terms of dry biomass. Converting to and from wet biomass isn't too hard, but allometry means it's very hard to go from biomass to volume, even within one species. Also, due to the retranslocation, biomass of a deciduous forest doesn't fluctuate as much as you might think [4].
What does vary quite a bit is Net primary productivity. For example, the seasonal carbon flux to the terrestrial carbon sink is highly dominated by northern hemisphere forests. So when you look at the seasonal cycle in CO2, what you're seeing is the effect of plant growth drawing it down in North American spring. I can't see an isolated graph of this on WP but see the bottom panel of fig1 in Carbon_dioxide_in_Earth's_atmosphere. So in much of the USA and Europe, plant growth is fastest when the slope of atmospheric CO2 is the most negative, and the highest biomass will tend to be when the CO2 value bottoms out for the year. There's of course a lot more going on, but this is the basics of how plant growth and seasonality work out.
If you have a specific region of the world in mind, then you can get local NPP estimates through the Ameriflux and Fluxnet projects, and you can also get local phenological info through a phenology network. Here is the website for the USA national network [5], I believe there are analogs for other regions. Hope that helps, SemanticMantis (talk) 15:23, 9 October 2015 (UTC)(ETA: found a better graph at ecosystem ecology.)[reply]
what factors (deficiencies, surpluses, exposures etc) cause increased rate of cell death and decreased rate of regeneration, leading to incidents such as more-often spontaneous bleeding, bruising, scarring etc[edit]
Also, senescence (old age) can cause this. Specifically, cellular senescence tends to occur more often in an organism which is itself senescent. StuRat (talk) 15:23, 10 October 2015 (UTC)[reply]
I know that it is a thing in that it's something that's discussed on the 'net, but is it an established medical procedure somewhere, and does it work? I've found no reliable sources, but lots of mentions on forums and similar, and apparently autocircumcision has been deleted three times. To clarify, I'm talking about "training" the foreskin to remain retracted and look like a circumcision. I ask because I've run across a crosswiki IP editor who adds images without supporting sources to articles about circumcision, foreskin and balanitis, like here and here. To me it looks very much like an excuse to post "dick pics" or to promote some fringe view. Sjö (talk) 11:46, 9 October 2015 (UTC)[reply]
The article about Balanitis, an inflammation of the glans penis, cites several reliable sources that indicate circumcision is often the preferred treatment. Possible alternatives to circumcision may be laser treatment (Baldwin HE, Geronemus RG (1989). "The treatment of Zoon's balanitis with the carbon dioxide laser". J Dermatol Surg Oncol 15 (5): 491–4) or use of the silicon retraction ring. The latter is alleged in fora in anonymous posts that link to Wikipedia illustrations but I find no peer reviewed study of the medical effectiveness of the misnamed ornament that simulates a circumcision temporarily. Bestfaith (talk) 18:10, 9 October 2015 (UTC)[reply]
@Bestfaith: Have you seen any WP:MEDRS or WP:RS about autocircumcision? I haven't. Sjö (talk) 05:56, 11 October 2015 (UTC)[reply]
So, if I read that correctly, the foreskin can be "trained" to stay withdrawn, but not by using a silicone penis ring like in the images? Sjö (talk) 04:38, 12 October 2015 (UTC) And there's no reliable source for "autocircumcision". Sjö (talk) 15:13, 13 October 2015 (UTC)[reply]
@Sjö: No, I have not either and I would not expect a vetted secondary source to endorse the misleading term. If one could verify A doctor from Saginaw, Michigan writing in 1951 coined the term "autocircumcision" that is claimed here one might find a WP:RS. Bestfaith (talk) 17:51, 11 October 2015 (UTC)[reply]
Material effective in damping (cushioning) free falls from supertall buildings[edit]
Which material is the most effective in damping (cushioning) man's free fall from supertall buildings like Burj Khalifa and how thick such a material should be? By effective I mean absorption of terminal velocity of a free-falling man, so no injuries (or only minimal bruises) are inflicted. Just for theoretical interest, not because I'm intending to do so.--93.174.25.12 (talk) 17:43, 9 October 2015 (UTC)[reply]
Fire rescue air cushions are often deployed to save lives of forced or voluntary (suicidal) jumpers from high buildings. This range of cushions need minutes to inflate with motors and are claimed to be useful for jumping heights up to 45 m. They are designed with 2 or 3 successive air chambers. The terminal velocity of a person in face down free fall position is about 195 km/h (122 mph or 54 m/s) which is a survivable fall on a sufficiently large cushion; however a head-down position as adopted by speed skydivers will greatly increase his/her velocity and probability of death. Bestfaith (talk) 18:38, 9 October 2015 (UTC)[reply]
Although they're still a subject of ongoing research, auxeticmetamaterials look promising for that. That said, when it comes to jumping off Burj Khalifa, I'd rather have a parachute. (Come to think of it, even taking the stairs seems preferable to jumping off, regardless off parachutes or cushions or whatnot.) --Link(t•c•m) 21:15, 9 October 2015 (UTC)[reply]
Free_fall#Surviving_falls, in a free falling plane, strapped into an airline seat, into the sea (from 300') and snow on rocks. Sleigh (talk) 02:06, 10 October 2015 (UTC)[reply]
Pictures of "aliens" often use the same sort of features, with a tall, thin body, a triangular shaped head, big dark eyes and a neutral expression. Assuming no governments have revealed actual evidence of extraterrestrials, what is this image based on? 2.216.10.148 (talk) 23:00, 9 October 2015 (UTC)[reply]
The classic fictional aliens, the greys, can be sourced at least back to an 1893 work by HG Wells. Wells argued that increasing reliance on technology would cause physical traits he deemed unnecessary to disappear or shrink, such as hair, ears, pronounced nose and brow ridge, and the mouth (which would shrink if not disappear)[6]. Was this his honest prediction as to what technologically advanced life would look like, or just a post-hoc explanation for an appearance he desired for fictional subjects? I don't know. I should note that in its original form, this was a proposal for what humans would look like in the distant future, but the image got co-opted (including by Wells himself) for use by fictional aliens. Someguy1221 (talk) 23:28, 9 October 2015 (UTC)[reply]
Let's look at some characteristics:
"Tall, thin body". That would make sense in a low gravity planet, such as Mars.
"Neutral expression". It would be unlikely we would be able to read each other's expressions, so we would each appear to have blank expressions to each other. ("It just held it's third tentacle at a 45 degree angle, does that mean it's angry ?")
"Big, dark eyes". Useful in low light levels, or if they are nocturnal. (The dark part being due to a larger opening for light.)
"Triangular head". This is common in insects, so I would guess they just choose that so they would seem "different".
Also note that the whole "two eyes, one head, two arms, and two legs" look is far from the only possible look. Even on Earth we have lifeforms that vary widely from this, like starfish. StuRat (talk) 00:51, 10 October 2015 (UTC)[reply]
It's also been noted that the space aliens imagined by earthlings are characterized by neoteny. They look like human babies, with big heads, big eyes, small bodies, lacking secondary sexual development, no body hair, etc. Space fetuses, if you will. - Nunh-huh 01:13, 10 October 2015 (UTC)[reply]
The lack of visible sex organs may just be due to censorship at the time. StuRat (talk) 01:17, 10 October 2015 (UTC)[reply]
As might the lack of nipples be. I suspect our space fantasies are multidetermined/overdetermined. - Nunh-huh 01:21, 10 October 2015 (UTC)[reply]
Lack of nipples would mean they are not mammals, and, at least on Earth, sexual reproduction is much more widespread than mammals. StuRat (talk) 15:02, 10 October 2015 (UTC)[reply]
Well, yes. I'm not sure it's reasonable to apply earth taxonomy to space critters, but nonetheless UFO observers have no qualms about calling some ETs reptilian. The point is not what actual space aliens would look like, but what our fantasies of what they would look like are based on. And I think it's pretty clear our limited imagination is basing those fantasies on earth creatures, rather than the myriad of possibilities including asexual, sexual, and other as-yet-unanticipated forms of reproduction. - Nunh-huh 17:12, 10 October 2015 (UTC)[reply]
See Through.the.Wormhole.S02E10.What.Do.Aliens.Look.Like. Tgeorgescu (talk) 22:45, 10 October 2015 (UTC)[reply]
