Are 'tree waterfalls' possible?

Question:
Something like the above (Natural Springs by Ellie Cooper) - either where the water originates from atop the tree through regular rainfall, or is directed up and into the tree via the spring (or some other source) below - somehow. I'd ideally like these to be created naturally, but man-made alterations are also possible if that would make them work when they otherwise wouldn't. It doesn't need to be a global phenomenon either, it could be local to a certain area of an otherwise Earth-like planet.
Comment: I think your main problem is that *trees aren't that non-porous*. In real trees, there is a *lot* of empty space between the leaves, such that water cannot accumulate in a volume larger than what a single leaf can hold. If you can overcome that, then I think your problem is just how to add enough water to the top of the trees to keep up a continuous flow (do you even need that?).
Comment: Not quite what you're after but Plitvice might be of interest https://graylinecroatia.com/tours/split/split-to-zagreb-transfer-with-stop-at-plitvice-lakes-11077_74/
Comment: Only if they are a large man made structure covered in soil that only looks like a tree. water falls only work becasue soils retains water and acts as a storage slowly supplying water to the river. otherwise they only last as long as the rain does.
Comment: Also the leaves directly under the water would drown and the tree would eventually die from that.
Comment: Can you specify the size?
Comment: Can you clarify your question by describing how this fits into your own fictional world?
Comment: @elemtilas I haven't really found a place for it in my own world, it was mostly just to see if such a thing were possible on an Earth-like planet. I'd definitely like to include it in some way though; it would probably be a vacation/beauty spot - an area for people to come and relax.

I haven't thought about it in measures of feet or meters yet; perhaps something around the height of a redwood or giant sequoia at their tallest - so around 250-300ft (76-91m) - but significantly thicker based on the root/branch/trunk network below the treetop as seen in the image.
Comment: Not at the scale of a waterfall, but I recently saw a PBS/NOVA special: "H20: The Molecules That Made Us" https://www.pbs.org/wgbh/nova/video/molecule-made-us-pulse/ (26:19) Regarding rain forests... "...400 billion trees pumping a staggering 20 billion tons of water each day into the sky". The imagery at that moment is neat too. "...all these clouds move like a river"
Comment: A huge broccoli would do the trick.
Comment: @Slarty Thanks for that. A place to visit on my tovisit list !
Comment: Not as depicted in that picture, because there is no possible sufficient source of water.  Unless there is a constant downpour of rain in that area.  A waterfall, like a river, requires a substantial source of water that lasts a long as the waterfall.  Usually that source is a river or lake, that itself draws its water from an enormous watershed in the surrounding terrain (minimally, many square miles).  You trees don't have that and without it, any significant waterflow is only going to last a several minutes after a substantial storm.
Comment: I'm a little surprised no-one has mentioned bromeliads yet. A keyword you might find helpful is "phytotelma".
Answer: No, at least not with classical trees. A tree can be defined as

a woody perennial plant, typically having a single stem or trunk growing to a considerable height and bearing lateral branches at some distance from the ground.

Branches with leaves can't be dense enough to hold water, as this would defeat the purpose of the leaves on the trees. A leaf converts sunlight to usable energy and if it's packed tight enough to hold water, it wouldn't get sun. Furthermore, a leaves are designed to let water drip through to the trees root system below.
If you want something like on the image, I would suggest going with massive fungus which can be "waterproof" and don't undergo photosynthesis.
Comment: A massive fungus with photosynthetic plants colonizing its top side could get the tree aesthetic going.
Answer: Of course there can!
Unless you're looking for a biologically true answer,1 in which case they can't because, looking around the Earth, there aren't any.  BUT!  I happen to know Mephistopheles a particular mad scientist2 who thinks that with some suspension-of-disbelief gene splicing and some particularly unnatural "stuff," you might achieve your evil plan goals with the following ideas:

The tree is massive and grows a natural bowl surrounded by a leaf barrier. The leaf barrier is meant to slow the wind to minimize evaporation of the accumulated water.

One value of the water may be to foster the growth of bacteria, plant life, or animal life, that leaves behind a nutrient the tree needs in quantities it can't get through the soil. This could be a naturally-forming tree version of soil inoculant.
Another value to the water would be that the tree is a massive water-stealer, in which case everything under the tree is a desert.

One method of filling the bowl would be rain... but that's often capricious and, despite what our mad scientist just suggested, sunlight is going to evaporate the water pretty quickly no matter how deep it is. Therefore, I'm voting that the tree is capable of some world class transpiration. Transpiration is the process by which plants move water from the soil to where they need it. Some of it is used during the photosynthesis process - the excess is expired through the leaves (not unlike sweating, but in a much finer process that's a lot more atmospheric than it is fluid).  But, your tree is BIG! And that means the process shifts from atmospheric to fluidic. Since plants do this today, yours simply need to do it on a larger scale with greater efficiency.

What this really means is that your trees can only form along underground rivers or over large aquifers.  They need a large source of underground water.  Soggy soil isn't enough.

Finally, you might want to think through the waterfall concept.  Consider the laws of thermodynamics, which basically say that if you've been suckered convinced to buy something that produces more energy than goes into it, somebody's probably stealing your identity along with your money. In other words, a tree large enough to form a waterfall worth looking at would need a MASSIVE water source to justify the amount of waste water dumped on the ground below.  Therefore, you might consider virga.

Virga is that streak of cloud you see that kinda looks like rain falling to the ground — but nothing actually hits the ground due to evaporation or sublimation. Basically, there isn't enough liquid water to survive the trip. If your trees resulted in virga (which, IMO, would be massively cool, the mad scientist likes it, too), they would be more believable since the massive water source need not be so massive.
And for the record, my mad scientist friend loves this idea because basically it's the most beautiful and amazing thing on the planet — and nothing and no one can live near them because it's a honking desert underneath them. See footnote #2.

1 And, frankly, if you really are looking for an answer to your "can this fantasy idea happen in real life?" question then you're kinda in the wrong place... with the exception of our Anatomically Correct series, but that has rules.  Remember, this is a place where you, the creator of a fictional world, seeks help to create that world's rules and expression. Thus, if you're asking, "My wife wants one of these in the back yard, how can I get one?" the only answer is "concrete is your friend!" But if you're asking, "how to I get these into my world in a believable manner?" Read on.
2 Muahahahahahaha!
Comment: @Renan I had *no idea* that WB.SE had a user with that name.  Aboslutely!  **Will the *real* Mephistopheles please answer the question!**
Comment: Well, I'd like to see [Mephistoteles](https://worldbuilding.stackexchange.com/users/32097/mephistopheles)'s own take on this question now :D
Comment: This is fantastic. Like a lot
Comment: Presumably the tree puts this whole shebang together for several reasons: stealing water from other plant-based-competition; using the fauna on top for fertilization and food; and the waterfalls are actually part of a nutrient filtering process =)
Answer: In terms of physical possibility, I think that picture is honestly a bit of a stretch, just because water is so heavy that I doubt any amount of wood would be able to hold that much of it up. But if the trees are a bit smaller, or the planet has a lower gravity, or these trees are made of something much stronger than wood, then sure, why not?
The real question is an ecological one: why would something like that exist? Here's my offering:
Suppose there is a region of your world that consists of a very nutrient poor desert. It would be very hard for plants to grow there, except for a lucky geological coincidence: underneath the surface is an artesian aquifer, meaning that if you dig down far enough not only will you find ground water, but it's under pressure, so if you dig a hole the water will come up to the surface, forming an artesian well.
A tree with a deep enough root system can reach the water, but why would it channel the water up into its canopy instead of just growing its roots down into the aquifer?
Well, earlier I mentioned that this desert is very nutrient-poor, and trees need nutrients to grow. One excellent source of nutrients is bird poop. How can a tree attract birds to a desert? By growing a bird bath!
So imagine some kind of migratory flamingo-like bird. They eat plenty of food in the fertile regions of the planet, but then when it's breeding season they fly into the desert to mate and lay their eggs in the tree-tops, where they're safe from predators. The trees provide nesting sites and large, shallow pools of water for them to drink and perform their flamingo-like mating rituals, and while they're there they poop out all the nutrients they've eaten elsewhere, fertilising the trees. It's a reasonably plausible symbiotic relationship.
Of course, the pressure in the aquifer will vary quite a bit, and perhaps after the rains there will be so much water that it spills constantly out of the canopies, and the scene will look not unlike the picture you posted.
Edited to add: from a video link in LazyReader's answer I discovered that this is actually somewhat biologically plausible. Apparently there is a very old tree in Montenegro which has a hollow trunk and sits on an aquifer that, after several days of rain, has enough pressure to force it up through the trunk. Here's a couple of screen grabs:

One can just about imagine that under the right conditions, evolution might start to take advantage of this effect.
There is another video here with a little more information about this tree.
Comment: +1 for this amazing find.
Comment: Cherry picking another person's answer without their permission is kinda no bueno. Especially when I added the link to give a new user's good idea a chance. Please don't do it again. (In fact, your answer looks an awful lot like a rehash of both my answer and LazyReader's....)
Comment: @JBH yeah I saw and I upvoted both. Theirs are the answers I like best in this question.
Comment: If it ever rained, the trees would have to overflow the excess water they caught, or the extra weight could overload and break their branches - hence waterfalls.
Comment: @JBH huh? Since when is that bad and why? The other answer mostly addresses a different phenomenon, not really related to trees, and had that amazing link at the end as an afterthought with no explanation. The link is relevant to my answer and I felt it deserved to be highlighted a bit more clearly. You will note that I clearly credited the other answer as the source
Comment: "Cherry Picking" is not now, nor ever has been a disallowed, forbidden or frowned upon thing in "the Stack".  If you were here at the beginning, as I was, you would have seen many times the statement that it was OK and even *encouraged* that answers improve other people's answers and integrate information from multiple other posts in their own answers.  And this is frequently done in SE forums, most especially in the original, StackOverflow.  The purpose of SE is not provide an ego gratification service, that's merely one of its means.  It's purpose is to supply the best possible answers.
Comment: Cherry picking without permission has been a no-no since the beginning of the Stack and probably since the beginning of Stack Exchange. One of SE's expectations is that *people improve other people's answers.* Cherry picking is just a way to gain rep for yourself without being an original contributor. What deserved to be highlighted was LazyReader's answer - and you robbed it instead. Giving credit while taking payment doesn't make it right. And the link at the end wasn't an afterthought, it was a continuation of the concept of the Tepui into flora.
Comment: It is true that *the expectation* when using information presented by someone else, is that you are providing some sort of improvement/better answer in doing so though, such as combining it with other suggestions and information. And, it is also customary to acknowledge where you got your info/idea from.
Comment: He didn't find it @Renan. I did, and I included it in my edit to LazyReader's answer.... I'm a little piqued about the incident.
Comment: And that doesn't begin to address what you took from my answer to "improve" Lucky's answer by creating an answer of your own.  I'm irritated.
Comment: I'll make you a deal.  You roll your edits back to your original answer and I'll ignore the obvious influence of my answer on yours and delete all my comments.
Comment: Link to an actual policy (e.g. on worldbuilding meta or the main one) or else it didn't happen. And no deal I'm afraid, sorry. If your answer influenced mine then you should be happy, though in truth it's more a case of convergent evolution. My answer gives details that yours doesn't (e.g. you didn't mention artesian aquifers), so while there's some overlap it's hardly the case that one is derivative of the other. If you for some reason believe that my answer is somehow taking attention away from yours, you can address that by improving your answer.
Comment: (A) [The Editing Process from the Help Center](https://worldbuilding.stackexchange.com/help/editing). (B) [The Expected Behavior section of the Help Center](https://worldbuilding.stackexchange.com/help/behavior). (C) As there isn't a specific "thou shalt not cherry pick" policy anywhere, I have [asked the question in Meta](https://worldbuilding.meta.stackexchange.com/q/7874/40609).  (And you're right, mine didn't mention artesian aquifers. But it did mention aquifers, which is a bit like saying your car is different from mine because of the paint's color.)
Comment: An aquifer is just ground water. It's not under pressure, so there's no reason water would flow up into the tree canopy. Trees can transport water up from the ground from an ordinary aquifer, but they use evaporation to power that process, so it wouldn't form a pool. One might say that an aquifer is like a car that doesn't have an engine.
Answer: Perhaps giant fungal organisms? Mushrooms are effectively > 80% water, so with a little stretching of the genealogy one could imagine giant mushroom-like organisms that sponge up large quantities of fluid from nearby (or underground) sources. It could then continuously eject the excess from atop its structure via large pores, or perhaps on cycle (weather / solar cycles) open up its pores and eject mass quantities of fluids. Fungal organisms have been observed to use water to eject / propagate its spore content here on earth...
Comment: I would definitely go with giant shrooms, even the trees in OP's pic look more like giant shrooms than trees. Not sure about structural strength, but at least the water tightness is there
Comment: I would go with a giant tree with giant symbiotic mushrooms. The tree can pump the water up and needs to release it for the mushrooms, some of it dripping down the side of the tree. When it's windy it can grow into spectacular waterfalls.
Comment: If anything, I would say the painting looks like giant *somethings* — they might even be rock formations, somehow — that have an entire *ecosystem* (soil, plants, birds, maybe even other animals) on top.
Answer: From a certain point of view, such things already exist, they're waterfalls found on buttes called Tepuis:

A tepui /ˈtɛpwi/, or tepuy (Spanish: [teˈpuj]), is a table-top mountain or mesa found in the Guiana Highlands of South America, especially in Venezuela and western Guyana. The word tepui means "house of the gods" in the native tongue of the Pemon, the indigenous people who inhabit the Gran Sabana.
Tepuis tend to be found as isolated entities rather than in connected ranges, which makes them the host of a unique array of endemic plant and animal species. Some of the most outstanding tepuis are Auyantepui, Autana, Neblina, and Mount Roraima. They are typically composed of sheer blocks of Precambrian quartz arenite sandstone that rise abruptly from the jungle, giving rise to spectacular natural scenery. Auyantepui is the source of Angel Falls, the world's tallest waterfall.  (source, emphasis mine)

The change for your world is that the water pressure forces the water up through the non-homogeneous trunk of a tree rather than through the non-homogeneous rock of the tepui.  And there's an example of this after the image.

Now for the example of water forced up through the trunk. If you're looking solely at a tree, consider the following two YouTube videos. The first is a tree with a waterfall that occurs only when it rains.  The second is more on point where heavy water saturation in the local area appears to push water up through the trunk to create a waterfall... something like what you're looking for.

Waterfall via Rainfall on the Tree

Waterfall via water forced up through the trunk
Comment: You should probably describe what  exactly Tapuis are, and also describe what is in the YouTube video. This answer doesn't stand on its own without some googling and watching the YouTube video
Comment: While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference.  Link-only answers can become invalid if the linked page changes. - [From Review](/review/low-quality-posts/68781)
Comment: Isn't it amazing how often the answer to "could this crazy thing happen theoretically?" is: "It does!"
Comment: It's funny that you brought up tepuis, as they're quite prominent in my current setting as well. I appreciate the video links however - these could work as a starting point, though I'm ideally looking for something that was a bit more constant rather than relying on heavy rainfall.
Answer: Hyathodes.

https://www.botany.one/2017/07/hooray-for-the-hydathode/
Hyathodes are pores on leaves of certain plants.  When root pressure is great enough, excess water escapes thru the leave pores and dribbles out.  This is called guttation.  I think it is kind of an escape hatch so the excess water does not damage the plant.
If there were serious root pressure (for example a dry adapted tree during a wet time of year) I could imagine enough water coming up from the roots and out thru the leaves to accumulate.
Better though is a tree that did this on purpose.  Consider the aphid.  It drinks great quantities of tree sap and poops most of it out.  Tree sap is protein poor and the aphid must process a lot of it to the the protein it needs, throwing out the rest.  So too these trees.  They process great quantities of water, retaining the nitrogen, phosphorus and iron they need and throwing out the rest as a cascade off the leaves.
Comment: This is a terrific answer as it also provides not only a live example, but a reason why a tree would have so much water at the top!
Answer: One humid morning in real life I witnessed a situation where it was raining under the trees. The air was warm and moist and the leaves of the tree were apparently cool. Water was condensing on the leaves and falling to the ground like a gentle shower. Your tree could condense moisture from the air and funnel it to a specific path within the structure of the tree and let it fall to the ground in a stream. This would be dependent upon a constant supply of warm humid air moving past your tree.
Answer: Take a look at Cushion Plants.

They are very low-growing here on Earth, but they are a true woody plant with leaves, rather than a moss or grass (which they do resemble). Their canopy is extremely tight - not watertight - but they also form mats underneath the growing canopy to conserve their dead leaves as insulation and compost.
You could imagine some sort of large-trunked version with a similar canopy, where the under-layers and branches form a dense, spongy 'aquifer' that can hold water. It would probably mean that the waterfalls would come out of the sides of the canopy, rather than flowing out of a 'bowl', and they wouldn't easily form permanent 'lakes' on top, but it seems at least plausible.
Answer: It's possible, you just need Giant trees, why normal trees won't work? Because water won't accumulate in a pond, it will simply fall off the leaves.
But giant trees have a problem with gravity, the taller the tree the harder it is to pull water from the ground up to the leaves, but giant trees have evolved a rain chamber that gaters water from the rain to overcome this obstacle.
Comment: How giant are we talking about?
Answer: The trees grow over geysers which push the water up inside the trunk. The reason for them to grow over a geyser which pushes hot water up their trunks is that there are minerals in the water they need. The minerals in this high concentration can only be found in water from the depths of the earth's interior. These minerals also contribute to the stability of the trunks so that they can withstand the pressure and heat. In the treetop there is a basin in which the water is filtered by e.g. roots. The filtered water flows down in the form of waterfalls on the sides of the treetops.
Because the trees filter the water so well, the thermal pools under the trees are a popular travel destination. Nowhere else can you find cleaner water.
Didn't do the math about weight or anything. I just tried to find a reason why there would be water in the treetops.
Answer: Generally speaking, a tree's roots extend as far as its branches extend.  If the branches caught and retained water like the image, then the soil around the root system would dry out and the tree wouldn't live very long.  I suppose the tree could evolve some way to absorb water through the canopy instead of the roots, but that's a distinct enough change that you it might not be classified as a "tree" any more.
Also, water will reduce the amount of light that reaches the tree's leaves.  Water is generally a bit murky, but even crystal-clear water will have some portion of the sunlight reflect off the surface.  This reduces the plant's ability to photosynthesize and would be a significant evolutionary disadvantage.
But let's forget about all that for now.  Pretend you have a magic tree with roots that extend to an aquifer and that doesn't need sunlight at all.  You still won't get something like you see in the image, at least not for very long.  Take the small tree-pool on the left as an example.  Based on the height of the woman standing near it (let's assume she's 1.7m tall), the tree-bowl appears to be ~1.5m deep and ~4.3m across.  That's roughly equivalent to a medium-sized above-ground swimming pool.  Given the rate that the water is flowing out of that tree, a completely full tree bowl would drain in no more than a couple of hours.  The square-cube law says the larger trees could drain for longer, but likely not more than a day or so.  You could see a spectacular sight like the image immediately after a large rainstorm, but they would quickly empty and you'd lose the waterfall effect.
The small tree next to the woman subtly reveals the only way you could get a scene that looks remotely like that image.  That tree's bowl is slanted at a rather sharp angle, and there's water visible at least halfway up the bowl.  This implies that the tree isn't holding or storing any meaningful quantity of water.  The water is coming from somewhere else and the tree is simply funneling it into a waterfall shape.  Some of the smaller trees in the foreground are dumping water at rates that are low enough that they could conceivably be fed by an underground spring and up through a hollow trunk.
The large trees in the background would almost certainly be an impossibility in the natural world.  The amount of energy needed to push water that high combined with the sheer volume of water coming off those trees means that the source water is under an unnatural amount of consistent pressure (geysers build up pressure and then spray in a burst, not a continuous flow).  Even if that pressure didn't blow a big hole in the rock, there's no way a young plant would be able to take root and survive while being blasted by a fire hose.
If you want to replicate this sort of visual experience in your Earth-like world, your more realistic option is for these "trees" to actually be rock/mineral formations.  The tree-like appearance is due to the various mosses and plants that grow on top of them.  This entire area was originally an underground cavern.  Springs ran through the cavern, eroding away the softer rocks and leaving behind stronger ones.  The cavern roof eventually collapsed, which is why you can see through to the sky.  The large "trees" in the background are pillars of erosion-resistant stone topped by a chunk of what was previously the ground that sat atop the cavern.  The smaller "trees" in the foreground are concentrated mineral deposits that accumulate around the openings where the spring's water exits the bedrock.  An arrangement like that would get you 75% of the way there.  You'd still have to figure out how to push significant volumes of water up to the top of the larger "trees", and I highly suspect you'll need artificial assistance for that.  Perhaps your inhabitants liked the visual effect of the smaller structures and wanted to replicate them on a larger scale.
Answer: Actually the structure on picture could have a non-tree explanation.
They're mineral deposits from the water, created on contact with air.
Somewhere deep there is a reservoir of water with high mineral compound, like quick setting concrete, that solidifies on contact with air. These are pushed up through the cracks and erupt as geysers. But because of the mineral buildup, you end up with mushroom like structures, as falling water deposits the minerals on edge of the structure.
The result is a very large stone structure like in the picture, with green fungus growth.
Answer: Yes, you have them in real life
Many plants have drip tips which is a heavy-precipitation adaptation to allow water to flow off of their leaves.  This creates small waterfalls.  Provided the scale of your setting is small enough (e.g. humanoid characters somewhere between 1mm - 10 cm in height) leaf-based waterfalls will be almost an inevitability.
Answer: Giant redwoods have quite interesting canopy ecosystems. See https://www.savetheredwoods.org/grant/sponge-like-mats-make-good-habitat-in-redwood-canopies-wandering-salamanders-benefit/
Notably, they are big enough that they can support soil formation. Scaled up you could have enough soil to have pools, and when the pools overflow, waterfalls. However, you're unlikely to get these at the edges of a tree like in the picture, simply because the whole top of the tree would need to be a pool, or the pool would need to form at the edge.
Basically, yes you could conjure up an ecosystem of very large, fairly densely packed trees that have behaviour like this.
Comment: Regarding the top of the tree being a pool... the picture looks like the branches/root structure have expanded outward, providing areas of semi-flat treetop. Would it be possible that the rainfall could eventually put enough weight on the tree that it shapes the topmost structure (with soil) enough to create a bowl-like shape for water to collect and then overflow?
Comment: @Vigilant Maybe! But bear in mind that a tree with an opaque "lid" on it is going to need to get all of its sunlight from the side.
Answer: The Traveller's Palm is known for its ability to trap water in the base of its leaves.
https://en.wikipedia.org/wiki/Ravenala
Another plant whose geometry leads to trapping water is Aloe Vera and similar plants.
https://en.wikipedia.org/wiki/Aloe_vera
Aloe Vera lives in a dry climate, and I would speculate that it could evolve to catch moisture in its leaves and funnel down to the centre where water could be absorbed. It's going to be tough to get enough water to be of any real advantage to a tree though. I would suggest heavy rainfall only about once a month would be the most conducive to developing a large plant with this characteristic. Of course, when the rains do come any excess will cascade off the leaves.
Aloe vera has a short stem, as do many arid plants, as it doesn't compete for light with its neighbours. There are plants in arid zones with tall stems. For example palms have a taller stem so it might be easier for a palm to evolve into a tree with a water trapping ability than Aloe Vera.
I can't imagine the diameter exceeding 10m though. Some of the trees in the painting look over 100m in diameter, bigger than any natural trees, and that's a separate issue.

Are 'tree waterfalls' possible?


Current snow depth in Tromsø

Question: I'm going to Tromsø, Norway and am concerned about the snow depth and how it will affect my ability to get around - how can I find out where to get the current depth online?
Comment: I accidentally discovered the website [webcams.travel](http://www.webcams.travel/) while looking at the yr.no page, and it turned out to be a quick and easy way to see what's the weather like at the moment in the location that interests you.
Comment: What Ivan said. You can walk anywhere that the locals might go, snow is cleared away, but if you want to go wandering around the countryside you'll need skis.
Comment: Get around where? The city? If you are worried about the city, I where there 2 years ago and there is no snow in the streets, but sometimes you can find some ice.
Comment: well im going to photograph the northern lights, skis you say? *gulp*.
Comment: I found with Stockholm that there was still snow in th city, 25cm or so. which wasn't annoying, but did slow me down a little more than I expected.
Answer: The Norwegian website yr.no is a good resource for weather information in Scandinavia. Looking at the information about Tromsø, among other things, there are live webcams on the bottom of the page, which, sadly, show that there is currently no snow at all there.
Direct link to the webcams: here and here. See also detailed weather information, together with rain/snowfall in mm (middle graphs, named Nedbør).
Comment: Another excellent webcam is at the [UiT CS department](http://weather.cs.uit.no/).  It includes archives and even time-lapse videos per past month or year, great fun to watch (:
Answer: Senorge.no has complete snowdepth information for the entire territory of Norway.  They have both present and historical information.
Currently, 8 August 2013, there is not much snow:

However, it's also possible to obtain historical data, for example, from 1 June 2012:

Or, indeed, from 24 January 2012:

If you want to go skiing to mountain summits, June may be a better time than January.

Current snow depth in Tromsø


Keyboard Messed Up: Windows XP Language Settings

Question: I've added Russian and the Russian typewriter keyboard layout in the Windows XP language settings and was able to use Russian letters in Word without a problem.
But when I tried to switch back to either my German or my US language/keyboard settings, the keyboard layout was the regular Latin character layout on the left side of the keyboard (seriously!), and it had mostly numbers and German Umlaute (ä, ü etc.) on the right hand side of the keyboard. Each number/letter occurred several times, whereas most of the letters that are usually on the right side of the keyboard are not there at all.
I tried switching back to Russian, but even that won't work anymore.
Obviously, this makes it impossible for me to use that laptop computer on which this happened at all, as the windows setting apply to most everything, including Firefox (I'm not writing this message on that laptop, of course!). Does anyone have an idea what I could do? I've already tried removing all language options but one, but that doesn't seem to help.
Thanks for all help you may be able to provide ...!
(I'm also a former Mac user who can't really afford their expensive machines anymore, but I should add that nothing like this ever occurred on my Mac ...)
Comment: If you type the first row of the keyboard, does it go `QWERTY` or `QWERTZ`? If the latter, it still thinks it's in German. That might help you figure it out.
Answer: I've got the answer ... I seem to have inadvertently hit the numlock key on my laptop's keyboard.
Think I've seen this answer as the solution to a similar problem, but first did not realize that this simple solution might apply to my problem.


Which is faster for a small amount of information, java file i/o or derby?

Question: I'm writing a small agent in java that will play a game against other agents. I want to keep a small amount of state (probably approx. 1kb at most) around between runs of the program so that I can try to tweak the performance of the agent based upon past successes. Essentially, I will be reading a small amount of data at the beginning of each game and writing a small amount at the end. It seems like I have 2 options, file I/O or derby. Is there a speed advantage to either? Or does it not really matter for such a small amount of data?
Answer: With 1kb of data, you are better off using standard file IO. Most likely, you could serialize the entire object tree to disk and dismply deserialize when you startup again. If you wanted to get fancy, you could use JAXB to serialize to XML instead of binary files.
As much as I love to fit every problem to the database solution, I don't think that's very practical here. Unless you have some special need of database specific capabilities, you are introducting a lot of overhead, complexity, maintenance problems by using a database.
The only areas where you might really want to use the database is if you have a lot of small objects/rows and you frequently perform sorts and filters on the data. But even then, you could probably keep a dozen in-memory ordered lists and get better performance with less resources and without the headache of a database.
If you really think you need a database in this scenario, consider HSQL. I don't consider it a real database, but it's a in-memory database that can persist to a file. Low overhead, low complexity, and relatively few points of failure. Plus, if you need to edit the persisted data, you can do so with a text editor. Can't say that about Derby.
Answer: Considering that these objects can vary per file size, and your computer's specs (bus speed, HD speed) affect this, the only way to be sure is to write your own benchmark.  Just create a simple for loop, count from 1 to 1000, and read the file inside the loop over and over (but do not create and destroy the objects inside the loop, just focus on the reading part).
Of course this whole exercise reeks of pre-optimization, which can lead to bad coding habit.  Just write your code in the most readable, simple fashion, and if there is a speed problem, refactor as needed.
But since it's a small amount of data, I would say it won't matter.
Comment: yeah, that's kind of what I figured.


Do I need a formal business plan to run a successful freelance business?

Question: In the UK, HMRC have created some tests to determine whether you are in business of your own account, one of which is that you have a business plan that gets updated regularly. Initially in response to this I started writing one but haven't got very far with it. I been working for myself successfully for a few years now without having a business plan and am wondering whether I should even bother? Legalities aside, what advantages or extra opportunities might having a business plan in place bring to a freelance business?
Answer: If you already know what you want out of your business and how to go about it, you already have a business plan. Perhaps not formalized and written down, but one nonetheless.
There are several things you can get from putting it down in writing:

You have a comparison point - something that you can use to compare the vision to the reality and that will allow for course correction.
You can clarify your thinking by putting in on paper. Seeing the plan in writing can help visualize issues and faults with it and finding any holes in your thinking. It may show that the business is not actually viable the way you envision it.
Once on paper, you can show this to others and get feedback. These can be relatives, colleagues and prospective investors (not to mention HMRC...).

These are all tangible benefits for your business strategies - of course, you can easily have a successful business without the above and the simpler the business model, the less the need to formalize the business plan (for example many one man IT freelancers are just one man contracting - but is that a business?).
Comment: @LeslieatAcmeConsultancyLtd - You seem to miss the "Legalities aside" focus of the question.
Comment: Generally, I agree to the answer above. However @Obed it seems you are missing that fact that this is specifically in question to the HMRC's test to determine if one is *in business for services* or if one is *in the business of service*. [See this article from HMRC] (http://www.hmrc.gov.uk/manuals/esmmanual/esm1011.htm) and this from [Contractors UK](http://www.contractoruk.com/news/00it_contractor_genuinely_business_beats_ir35_claim.html)
Answer: Short answer yes, but a business plan helps.
Long Answer
There are two traps that come from business plans, IME:  Not having one, and following one closely.  This seems contradictory but it is not so much.  As Eisenhower said, "Plans are nothing; Planning is everything."
The major point of preparing a formal business plan is to think through all of the major facets of your business, write them down, and look at the major issues that may come up.  If you are creating a business plan for yourself what you can get out of the process is clarity regarding your business, what the options for promoting it are, etc.  Now, here you are not writing it down for investors.  You are writing it down for yourself, and thinking through all of these (how would you describe the market?  What options do you have to reach the market?  Which options should you start with?) gives you an advantage.
However, having a plan is worse than not if you slavishly follow it.  Chances are, if you put it on the shelf and don't look at it for a year, having throught through all the issues, you will find that your business follows, generally, the trajectory of the business plan (because both are a product of how you think and the clarity that comes from doing the plan will benefit your business).  The issue however is that life does not unfold according to our plans.  Unexpected opportunities may come up.  Things that we thought would be keys for success fizzle and businesses need flexibility.  I can't tell you how many times those things have happened to my business in my 8 years of self-employment.  You work around them based on what you need at the moment, and when you come back to your plan in a year, you will find you have made more progress than you thought.  This is true regardless of such setbacks.  I have again often been amazed at how much of my business plans I made progress on during more difficult times of my business, and this has usually benefited me greatly.
The process I recommend for the self-employed is as follows:

Write a formal business plan.  Target 20-30 pages.
Put the business plan on the shelf.  Don't look at it for a  year.
Every year, read, review, and revise based on what happened the previous year.

To recap:   What you get out of a formal business plan is a clear view of what options you have and what you can do to achieve your goals (and you should write a business plan with the goal of thinking through these).  Don't expect the universe to cooperate, but the process of writing one brings a great deal of clarity.
Comment: When I write a business plan for myself I generally follow the following approach:  1) survey of the market, 2) What people need, 3)  What I am offering, 4)  How to promote, and 5) the nitty gritty (financials, etc).  I find this gives me the best value.  If I am writing for someone else though this may be different.  If you want to bounce ideas back and forth, happy to chat about it.
Comment: +1 for not following the plan too closely. As you say, the future is never certain and one could easily miss opportunities if one sticks too rigidly to a plan. I think it could be a beneficial thing to write to provide some clarity on potential marketing and/or revenue channels that I hadn't previously considered
Answer: Short Answer: It depends
Longer Answer: It depends on whether you, your business or your business's future direction require one.
A business plan is just that: a plan. It identifies a way from here to there with the steps in between.  If you (and your business) are happy the way you are, having a Business Plan stating "No changes" is a waste of paper!
Whatever you do, do not try and run your business based on HMRC's propoganda. Their IR35 track record is based on Fear, Uncertainty and Doubt - and pretty much their initial decision is "Caught".
Should you truly feel that a Business Plan will help determine that you are IBOYOA  then make sure it is realistic... a "War and Peace" epic of how you'll change the world will only raise an eyebrow if you are still operating as an agency bum-on-seat
And (to go with the Eisenhower quote) the paraphrase of Helmuth von Moltke the Elder's thesis: "No plan survives contact with the enemy" - so keep it up to date!
Comment: Drat... don't have "Tag Create" privileges.  IBOYOA = In Business on Your Own Account. "Bum on Seat" = self-deprecating term for jobbing contractor akin to temp.
Answer: If we speak about the formal definition of the business plan, I don't see a way it could apply to the freelance activity. You don't sell anything, you don't produce any material goods, you don't hire people (if you do so, it's no more freelance activity).
However, if you take the business plan in more common-language meaning, the business plan for freelancer would be similar to the business plan for regular employee. I would rather call it career planning. Your costs and investitions are the things you learn and the time it will take you to reach certain point in which you can sell your services to the customers.
Such business-plan for freelancers could look like that (example for Poland):
1) Market analysis. The business contacts with China are more and more intensive and there are too less people that speak both Polish and Chinese fluent.
2) I need about 3 years full-time learning to learn Chinese fluent.

monthly cost of course materials/consultations - 300$
monthly living costs - 500$
6 months practice in China - 12000$
overall - 36000$

3) An average translator is doing monthly:

100 pages written translation, avg. 15$/page
40 hours oral translation, avg. 25$/hour
so I will earn on avg. 2500$ monthly (2,5x more than average wage)

4) That investition allows me to earn 1500$ more that now, so the invested 36000$ will return in 2 years
So the business planning for freelancer isn't much more different than the business planning of average person.
Comment: "You don't sell anything": huh, don't you sell services ? Don't you have to invest in equipment, marketing, training... ? Don't you need to balance charges and earnings, predict income, define a strategy... ?


Disabling quartz job in Grails

Question: I am using the Quartz plugin in Grails. Is there a configuration that I can use to disable the job, without commenting out or deleting the whole file?
Answer: as a workaround, you could make the job check a configuration option, or query the DB, and just not do its thing if its not supposed to.
Answer: I'm fairly certain this functionality does not exist in the current version of Quartz. However there is a patch that implements job cancellation and rescheduling, so it seems plausible that it will be added to the official release in the (near?) future. See this email thread for details. If you want to try the patch yourself, it can be found on the bug tracker.
Answer: I don't know if this is still relevant, but how about adding a return statement as the first line in the execute() method?

Disabling quartz job in Grails


Why is the clarinet able to play lower notes than the soprano sax?

Question: The clarinet and the soprano sax are similar in size, but the clarinet is able to play much lower notes than the soprano sax. Why is this the case? I understand that when the clarinet is overblown the pitch goes up by a 12th, not an octave, which extends the range, but I don't understand the physics of how it can play so much lower than the soprano sax. It seems like it could be partly to do with the size of the mouthpiece (soprano sax has a much smaller mouthpiece) or possibly to do with the bore shape, but I'm not really sure whether any of these reasons are right.
Answer: Both instruments (as well as all single- and double-reeded instruments and all brass instruments) behave as tubes closed at one end. The difference is that saxophone (and all other reeds) are conical, whereas the clarinet is cylindrical.
For a conical tube closed at one end, the fundamental wavelength is twice the length of the tube (Actually, it's a bit more complicated than that, but that will work for a basic understanding).
For a cylindrical tube closed at one end, the fundamental wavelength is four times the length of the tube (and the instrument only resonates odd harmonics). So for a basic approximation, a clarinet is going to be about an octave lower than a similarly sized conical instrument.
Comment: Just to complicate things :-),  the transverse flute  is essentially open near one end (not at the actual end of the head joint),  and is more of a Helmholtz resonator than a tube resonator.  But that wasn't part of the original question.  Just putting this out in case someone wonders why the flute, with cylindrical bore, overblows to octave, not 12th.
Comment: @CarlWitthoft if the flute were a Helmholtz resonator then it wouldn't be able to cleanly overblow _at all_. The fact that it overblows the octave despite being cylindrical demonstrates that it indeed behaves as a tube resonator with both ends open.
Comment: @leftaroundabout I'm not completely sure whether a Helmholtz device "counts" as an open-ended tube or not, but your point is well-taken.  I have built crappy ocarinas which overblow, but that probably points more to lack of fipple quality than anything else.
Answer: You pointed out the reason. The clarinet acts as a stopped pipe. An open pipe has a node (little air movement) at each end and an anti-node (lots of air movement) at the middle (or maybe I've got this backwards; check the physics of wind instruments pages.) Thus the clarinet's fundamental wavelength is twice the pipe length and the saxophone's is equal to its pipe length. Thus for the same length of pipe (the effective length of the instrument), the clarinet would sound an octave lower than the sax.
Next, (as mentioned in the question) the clarinet's natural overtones are the fundamental, third overtone, fifth, etc., while the sax's are the fundamental, second,third, etc. The clarinet starts and octave lower and its natural vibrations are the odd harmonics. A sax's natural vibrations are all the harmonics.
Comment: @supercat It's the conical shape. Both instruments are blown with the same mouth piece. (I'm neither a sax nor clarinet player, so I won't rule out minor changes to the mouth piece shape, but the operating principle is exactly the same. And that's what matters). The conical shape makes the pipe behave like an open-open pipe, even though it's actually closed-open.
Comment: You got it backwards: An open end does not allow for pressure to build up, so you always get nodes with movement but no pressure oscillation at an open pipe end. Both the sax and the clarinet have an open and a closed end (the mouth piece), and you get a pressure oscillation at the closed end of the clarinet. I.e. pressure oscillation at the mouth piece, and air movement at the other end. Which is the cause for the specific sound of the clarinet, because it means that its spectrum cannot contain any even harmonics. The sax behaves differently because of its conical shape.
Comment: Is the difference because of the conical shape, or is the difference because of the reed design?  A positive pressure wave pulse which hits an open pipe end will cause a negative pressure pulse to be sent back; a positive pulse hitting a close end will cause a positive pressure pulse to be sent back.  A positive pressure pulse which pushes a reed "closed" will cause a negative pressure pulse back, while one that pushes it "open" will cause a positive pulse back.  If a round trip results in a pulse of the same phase as the original, the pipe will support all harmonics with...
Comment: ...a fundamental wavelength of twice the pipe length (one round trip).  If it results in an anti-phase pulse, the anti-phase pulse will essentially cancel out any sound whose wavelength would be twice the pipe length, or any harmonics thereof, but it will support oscillation with a wavelength of four times the pipe length (two round trips), and odd harmonics thereof.
Comment: @supercat The clarinet with the cylindrical bore and closed-open behavior produces the fundamental (four times its length), but cannot produce the even harmonics (second harmonic = twice the length) because that would require nodes of the same type at both ends of the pipe, which is not possible in the closed-open configuration. You find this behavior of missing even harmonics in other instruments as well, and it always tends to produce a very characteristic sounds that resembles the sound of a clarinet.
Comment: @cmaster-reinstatemonica: On a pipe organ, both conical and cylindrical reed pipes can behave in either fashion, based upon the design of the assembly containing the reed.


How did an English person get entry to East Germany during the Cold War?

Question: I need to know how an English person was able to get authority to visit East Germany and what the most common crossing used was. Additionally, any information on how visitors were treated by Stasi would be helpful.
Comment: Welcome to History:SE. What has your research shown you so far? Where have you already searched? What did you find? Exactly _when_ during the Cold War is your period of interest? Please help us to help you. You might find it helpful to review our [Help Centre](https://history.stackexchange.com/help) and, in particular, [ask].  In general, [SE sites work best if the questions are supported by preliminary research](https://meta.stackoverflow.com/q/261592/2085030)
Comment: How would they have gotten into contact with Stasi in the first place, in your opinion?
Comment: @BernhardDöbler Since the Border Guards (Grenztruppen) stood under the orders of the Stasi (see link to the Order of 22.12.1979, Intoduction of Visa requirements in my answer) and had to pass on any information gathered from travelers, the 'how' they got into contact should be clear. This was clear to **realistic** travelers, even if the details, - known now - was not so clear. Unfortunately the **traveler_virtural_world_56zba67569Z** today still don't understand that they were the **cause** for the delays of the **realistic** travelers and contridict them at every opportunity.
Comment: Would your English person in question be there a random Jon Doe who's there for private pleasure (family visits, sight seeing) or someone who'd come to do research, business or politics, for example? And long would the stay be?
Comment: Hi. I am researching for a novel. The individual in question is trying to discover how his father, a German teacher, was killed under the Nazi regime. He was taken by his german mother to England after the war and grew up there. He  has applied for a two week visit  to go to the town of his birth. So i have been seeking information on how he would apply to visit, what would be the limitations imposed on him and how his actions might be monitored by the state.
Answer: I visited East Berlin and Dresden in 1978 with my mother and sister ( I was 18 at the time) from the USA.  We had to obtain visas many months prior to our visit from a travel agent who specialized in this.  When we arrived at each of our destinations we had to register with the city officials (listing where we were staying and for how long).  As I recall we could not check in to our hotel unless we had the proper paperwork from the city officials which was obtained when you registered.
The visas were issued for the exact time frame we had stated for the trip and we had to be out of the country by midnight of the day of our departure.
We came to East Germany (East Berlin) via train from Aachen.  We traveled to Dresden via train from East Berlin and then back to West Berlin after our time was up.
We had no interaction with the Stasi as far as I know.  Our interactions with the East German State consisted of customs at the border and at the various registration places (I don't remember what they were called) in each city we visited.
Comment: @sempaiscuba Due to agreements among the occupying powers regarding the status of Berlin, it was far easier for Westerners to visit East Berlin than (the remainder of) East Germany, even if, politically, there was (post-1961) little difference between the two for people who actually lived there.
Comment: You might have interacted with the Stasi. Border guards and administration officials might have been undercover agents, and overt officials would have checked your visa application against their files before it was approved.
Comment: Thank you Matt. That was really helpful.  I appreciate you taking the time to answer.
Comment: That's interesting.  I visited East Berlin in 1982. No advance visa was required, since I didn't stay overnight in East Berlin.  I was given an insert to my UK passport by East German immigration while I was on the train (I travelled by train from Hamburg to West Berlin). I then just took the U-Bahn to East Berlin each morning.  At the end of the day, I walked across the city and returned through Checkpoint Charlie (just because I wanted to cross at Checkpoint Charlie).
Comment: @CMonsour Correct. That was also why before 1977 foreigners received a permit that was valid for 24 hours. Starting 1977 a Visa until midnight, which was the rule for Germans.
Comment: As you can see from the original order for visas in my answer, which was issued  by the Stasi, the Border officials were under the direct control of the stasi even though they were a part of the military. All collected when to the stasi for evaluation.
Answer: For any visit for staying overnight, a form of package tour had to be organized by the Reisebüro der DDR

unless you were invited by relatives of on business

A visa would then be issued at the border, based on the papers issued by the Travel Agent (on behalf of the Reisebüro der DDR) or by the Volkspolizei for private visits.
Exception: day visits to East-Berlin or a Tourist bus tour to Potsdam, where a permit (1977 Visa with a DM 5 fee) would be issued at the border.
Day visits outside of East-Berlin were only possible for residents of West-Berlin, when they were applied for beforehand.
For all day visits, the same crosspoint you used to enter had to be used for exit.

Order from 22 December 1976, Ministry of State Security (Stasi)
  Introduction of Visa requirements for non Socialist citizens ...
  ...

die Ausreise hat bis 24.00 Uhr des Ausstellungstages des Visums über die Grenzübergangsstelle zu erfolgen, über die die Einreise erfolgte ;
the departure must be made by 24.00 on the day of issue of the visa through the border crossing point through which the entry was made;
  ...

Order contains all other regulations, referencing those that have not changed

Although there were some extra regulations for German citizens, these rules otherwise applied for all westerners.
Comment: Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/101126/discussion-between-sempaiscuba-and-mark-johnson).
Comment: Thank you Mark. Really helpful. Appreciate you taking time.
Answer:
Q: How did an English person get entry to East Germany during the Cold War?

Just crossing the border, ignoring all East-German border guards!
That may have been as simple that. Really.
Angering all of those East-Germans, to be sure. In Berlin, at crossing Friedrichstraße, Checkpoint Charlie.

On August 2, 1989, the "Berliner Zeitung" newspaper, which appeared in the eastern part of the city, reported that the East Berliners would be annoyed by the visits of Allied soldiers from the West, using a report from the German Press Agency (dpa): "Anyone who explores the surroundings of the 'Centrum' department store at the main railway station on Saturdays, for example, will easily find several British private cars and British military buses. In front of the 'Centrum' department store at Alexanderplatz there are two French military buses and three American ones. And then, with their tartan skirts and tight calves, a few 'Highlanders' march through the socialist consumer paradise.

That's because in Berlin the Western allies insisted that they were always allowed to 'inspect' the Eastern half of the city. Without any interference of not sovereign lackeys of the Soviets: meaning an East-German border guard could tell them squat. If the GDR-guards would try something funny, they were usually ignored, Westerner insisting to speak only to their masters.
Well, once they did try something funny. The result was:
 (src)
This image from October 1961 is always used in documentaries to illustrate American defiance after the wall was being build. But it was nothing like that. The tank stand-off came after E Allan Lightner wanted to return unhindered - as usual – from a night at the opera in East Berlin. After being asked for papers the result was the above; and shortly later the Soviet admission of guilt, Lightner's return and continued business as before:
If in uniform, any English could go to Checkpoint Charlie and visit the East. Some formalities with his regiment beforehand to know his whereabouts and presumably prevent defection. But the uniform was really optional. No uniform meant just to show a waver card and otherwise do the same.
From there it gets funny. Travel recommendations for soldiers said to "prefer U-Bahn but don't take any S-Bahn". Why? Because the S-Bahn would take drunken strangers out of Berlin, a thing not covered by 4-powers Berlin-status. But the point is that that could happen easily.
The starting quote illustrates that this option was used extensively during the 80s, especially by US troops. Since after Nixon cancelled Bretton-Woods the Dollar got so weak that they would prefer shopping and partying in the East.

–– Berlin crisis: the standoff at Checkpoint Charlie
––  Stefanie Eisenhuth: "Freizeit Beim Feind. US-amerikanische Soldaten in Ost-Berlin", Zeithistorische Forschungen/Studies In Contemporary History, Vol 15, 2018, (p11–39).
This is of course not the typical case for non-soldiers. But there are mainly three very different scenarios to observe: allied soldiers in Berlin or on their way to Berlin, diplomats or 'diplomats' (the latter being 'peace scouts' eg ordinary spies) and non-military private citizens. For the last scenario I refer to other answers here.
Comment: I have learned a lot from the answers given and your willingness to take time to discuss and comment.
Comment: -1 This is a terrible answer and pertains **soly** (i.e.not for an 'English person' as asked) for Allied Military. One a side note of the 3 Allies, the British soldiers were **strickly** checked by British MP on return to Checkpoint Charlie. They had to prove that for everything they bought that the East Marks were legly exchanged.
Comment: Yo, Almost "exactly"! Reading answer again might reveal to you that what is implicit throughout is also made explicit in the last paragraph: that this when soldiers want to cross. And if you read the question again it might also dawn how irrelevant any concerns about returns are, when it is answering a question how any English, including such soldiers, "get *entry* to the GDR". To the @upvoter-of-that-comment: I am very disappointed at your reading and comprehension skills.
Answer: Here is some anecdotal evidence. A friend of mine travelled to East-Berlin during the late part of the cold war. He's a Swedish citizen and he travelled using a tourist visa. Don't know how hard it was to get, but I think they wanted tourists for currency and propaganda.
He went by train and said that when the train stopped in West-Berlin all the tourists got off and it was just him and a few businessmen on the train. Then a grumpy border guard entered and demanded "Papire, bitte!" and when he saw that he travelled on a tourist visa he suddenly became very happy. "Ah, jungen touriste!".
He also claimed he was the only one to write graffiti on the eastern side of the Berlin wall so he may not have been entirely reliable.
Comment: No graffiti on the eastern side of the wall when I visited in 1978, you couldn't even get close to it from that side.
Comment: Anecdotal infomation really helpful to me.  Thank you


Will Cone standing on its tip, without any other force other than gravity topple?

Question: A cone standing on its tip is considered to be in unstable equilibrium as a slightest force could topple it. So, if the cone is stood on its tip with no other force other than gravity (and the corresponding ground reaction force), will it continue to stand without toppling? Has this been attempted experimentally?
Answer: If you made the most perfect cone possible, so that its tip was a single atom, and stood it on the most perfect surface possible (a perfectly smooth, perfectly hard sheet of atoms), and completely removed all forces other than gravity, it would still topple. This is because those atoms are all jiggling around due to thermal motion. This effect fundamentally cannot be removed, and sooner or later it will cause enough of a perturbation to cause the cone to start falling. It might take a fairly long time before this happens, however.
A more realistically imperfect cone might have a better chance. A real metal object isn't perfectly smooth. It's fairly likely that the tip of the cone will actually be rounded, even if it appears perfectly sharp under a microscope, and on an even smaller level it will be quite jagged. The same applies to the surface. It's possible that the two will find a way to mesh together such that they balance, especially since neither will really be perfectly hard, so they'll inevitably sink into one another a bit.
As for whether the experiment has been done, I'm sure a lot of people have made cones of varying degrees of imperfection and attempted to balance them with varying degrees of success. But the idealised experiment - perfect cone, perfect surface, no other forces - would be rather expensive. Creating and checking the cone tip and the surface would require an electron microscope, but the really hard part is eliminating all other forces. Air movement, seismic vibrations, electromagnetic effects, perhaps even the gravitational field of nearby objects would all have to be accounted for. For these reasons I doubt that version of the experiment has been done.
This is going beyond what's practically possible, but in principle, thermal effects could be eliminated (or very nearly eliminated) by cooling the system down to absolute zero. It's impossible to completely reach absolute zero, but we can get very close. But if we do that we run into a different problem: Heisenberg's uncertainty principle. The problem is that in order for the cone to be perfectly balanced, its centre of mass must be exactly above the point of the cone, and also the cone has to not be moving at all, i.e. it must have exactly zero momentum. But if the cone was set up in that way we would know the exact position of the centre of mass, and we'd also know its exact momentum at the same time. Quantum mechanics says this is impossible, and this means that even if you could eliminate thermal effects completely, it would be fundamentally impossible to set the cone up so that it was absolutely, perfectly balanced.
Comment: What about a temperature of absolute zero to eliminate thermal motion?
Comment: @vsz I've added a section explaining why the cone can't be perfectly balanced even at absolute zero, because of Heisenberg's uncertainty principle. Thanks for raising an important question!
Answer: A few seconds.   What "a few" is numerically depends on the author of such calcuations, but generally something like 4 or 5 seconds, maybe up to 10.   Quantum mechanically, it must fall.  Which direction, no one can say. The perfect symmetry of an ideal cone on an ideal flat surface will be broken as the object "chooses" some direction.  For realistic materials, microscopic imperfections, thermal motion of atoms, and electromagnetic fluctuations will surely perturb the object to fall in  a particular direction.
There was an article in American Journal of Physics, probably early 1970s, that either explained the calculation for a pencil standing on its tip, or made reference to another paper that did the calculation.  I looked, but did not find it right now.  But others have written about this topic.
Try this more recent paper:
http://rickbradford.co.uk/HowLongCanAPencilRemainBalancedOnItsTip.pdf
or
http://mccammon.ucsd.edu/~jcsung/qmp.pdf
Whatever the proportions of your cone, if it's a cone, pencil shape, or a pin, the difference won't matter much.  The time it stands may vary some due to different moment of inertia, but nothing wild.
If attempted experimentally, it is possible for an object to stand on point slightly longer.  As it starts to fall in one direction, a tiny random jiggle of the table due to sound waves, a truck going by outside the building etc, may happen to move the point back under the center of mass of the object, delaying its fall. But I won't be placing any bets on the object standing for, say, half a minute.
If simulated in a computer, using classical mechanics and having the pointy object placed exactly at the origin and using a perfectly symmetric grid, it could stay up forever. This is a pathological result, however. Simulations that are too perfect have trouble breaking symmetry.
Answer: Two additions to the other good answers:

"with no other force other than gravity" - the cone will obviously fall down. In order to balance it, the surface it's standing on must exert force on it.
Even if Earth's gravitation pulls it straight down, we must not forget other gravitational forces. The most significant would be the moon's pull, which constantly changes direction, and would disrupt the perfect balance.
Comment: The force exerted by the surface is the reactive force to gravity is it not? If we exclude that, when I say no other forces, it will become free fall.
Comment: Other gravitational forces - That is a good point and did not come to mind when I thought about this.


Writing technique resources

Question: Are there resources (books, blogs...) which describe proven techniques to obtain certain effects? For example: you will obtain this effect if you use the first person, effective ways to describe fear, doubt, exhaustion, love... are the following.
Answer: Writers read. We read lots of things in order to learn from our betters how they do what they do. Read the instructional blogs and books, but being a reader who picks apart stories and sentences to see how they achieve their effects will provide better, more inspiring, instruction.
Comment: I believe you have it. While there might be a manual out there somewhere, the first place to go is to find authors who achieved what you want to. Figure out how they did it, and copy and paste (the technique, that is). Rinse and repeat.
Answer: Yes and no.
Yes: There are heaps of resources to explain how to do pretty much anything in writing.
No: The world changes and humans change faster. What worked once might not work later, and a technique that might be used to great effect now could be a tired cliche in a few years. Plus your readers will all be different. The first time I read the twist that the narrator was the murderer all along, I was thrilled. After that, it's old hat. But other people might read the same books in a different order...
More specifically to your examples, you can read about the general consensus on which 'person' to write in, but when it comes to describing emotions on the page - finding the perfect, original way to do this is every writer's goal. If it were fixed (or easy) we wouldn't need writers to be creative.
Having said that, you should read about 'motivation-reaction' units, which break down reactions into: Feeling > Reflex > Rational speech / action. That's quite helpful to understand. http://www.advancedfictionwriting.com/articles/writing-the-perfect-scene/ (you have to scroll down a fair way)
Answer: At first this seemed a superficial Q, but when you think about it, why not?
In many arts, like painting, there are clear technical manuals. This is in no way limited to "crafts". Obviously the artist interprets and applies the method, or goes against it, in his own personal way. Why should writing be different?
There should be

"proven techniques to obtain certain effects?"

Unfortunately, Adrien Hingert, I am not aware that any such site exists.
You might find some answers by combing through S.E. Writers for Q like:

The "Rules" of Writing
Books to improve writing skills
What are good reads about writing?
Answer: If you are looking for effective techniques for producing an effect on the reader, you will not find them in writing so much as in storytelling. It is in the juxtaposition of people and events that you create an emotional effect. Robert McKee's book Story may be useful to you on this point. He makes that point that a good story badly written beats a bad story beautifully written every time.
Answer: I'll add to the already good answers:

effective ways to describe fear, doubt, exhaustion, love...

There are a lot of writing guides out there, some more general, some more specific. Some bad, some good. I'll tell you about my experience with a book called "the Emotion-Thesaurus" that a friend gifted to me and I'm using (even if not consistently).
As the title implies, it's a dictionary for emotions (Love, Anger, Despair ...). Each one gets two pages with useful informations, such as external cues, internal cues, effects of prolonged exposure, related emotions and so on. So it's a pratical guide to make your writing more vivid.
In my experience, I'm used to show certain emotions in a certain way. One of my characters bites her lips when she's feeling uncertain. Yet I can't use it too much, and I can't apply it to everyone, so the thesaurus comes in handy: other characters may show uncertainty by averting their gaze, stuttering, pausing for some time ...
So this may be a resource worth checking. Consider that it's not something you're supposed to read from start to end (I suppose it would be extremely boring, trying to read a dictionary). It's as good as you're willing to open it up each time you want to give more depht to a given emotion.
Answer: As a habit I read some educational General Literature and Factual/Referance on Google Books (previews are free)
booksgoogle.com
www.writersdigest.com
Answer: I'm not familiar with anything exactly matching your description, but you might want to take a look at tvtropes. They don't describe how to archieve certain effects, but they do describe more or less general concepts (so-called tropes). Some tropes are things you can just use in a story (e.g. tomato surprise, lampshade hanging), while others are concerned with completely different things (e.g. writing by the seat of your pants).

Writing technique resources


Choosing the correct level of politeness when translating foreign material

Question: Here is my question: how do you choose the correct level of politeness in Japanese, when translating foreign material that may not follow Japanese rules? Let's say we have a formal setting, e.g. a shop clerk and a customer. The shop clerk was a former collegue of the customer's mother, so she speaks in a very casual way (let's say the equivalent of plain form), and actually ask "do you mind if I speak like this?" Although she knew his mother, it's still the first time they meet, moreover he is a customer, so I guess in Japanese she would at least use the polite (-masu) form, but I was wondering if that would be a faithful translation and, on the contrary, if her speaking in plain form would be perceived as rude (it's only meant to convey intimacy). What do you think?
Comment: I think this question is fundamentally unanswerable as is, because how best  to translate depends on both (a) the source material and (b) the purpose of the translation in question. Without both being well defined, it's hard to say what is "the correct level" of anything one can vary in translating (obvious there's an infinite number of ways to translate wrongly).
Comment: Rather than try to figure out how to preserve the level of politeness of the situation, I would try to translate the situation in relation to the cultural norm. It also depends on the kind of store, such as a family run business vs. a department store (Cf. "いらっしゃい" vs "いらっしゃいませ"). Is the speech typical for that situation? If so, I would try to translate the gestalt rather than the exact interpersonal and sociolinguistic parameters.
Answer: It would be natural to first think of the social position and standing of the people involved in the conversations so that it is easier for Japanese readers to imagine the mood and relationship of the characters.
If, for example, there is a homestay family welcoming a foreigner into their home you might pose the family speak politely if they are unfamiliar with the guest or casually if they wanted said guest to feel more at ease. The guest can then, in turn, be framed to speak politely if he/she intends to show good manners or be a rare visitor to the country, or casually if totally unaware of the norms or be familiar with the hosting family.
In other words, it is best to keep the constructs of Japanese society in mind when framing your sentences and choosing the proper form, because you aim for the Japanese readership after all.
Comment: I have no idea what is actually the most common here, but I would say there are two different schools: Either you adjust the speech to what it would have been had the speakers been Japanese living in Japan. OR, you keep the social constructs of the society that is being enacted, which in my opinion would better keep the spirit of the book. Japanese readers are already aware that it's being played out in another country. You are saying that the first method is "best", but I would say this is very subjective. Do you know for certain which method is preferred in general?
Comment: I see your point. I was just offering that advice because of the target demographic. It wouldn't hurt to frame things from the viewpoint of your readers to help them understand.


How can I convert a blackball LMDB database into a wallet-readable format?

Question: The resulting file after running monero-blockchain-blackball is a data.mdb LMDB file. Unfortunately, this file cannot be opened directly by the GUI or CLI. How can I extract the necessary data so that the wallet can read it?
Answer: You will need to follow these steps to convert the database to a list of outputs that the wallet can read. I have performed this conversion on Debian/Ubuntu.
In order to extract the data, you need to build the LMDB tools. Follow the instructions on GitHub to make the LMDB binaries.
cd ~/monero/external/db_drivers/liblmdb
make
Then run the following:
./mdb_stat -a /folder/with/blackball/database
This will show the hash of the database that you have created. Take a note of the database name (eg: blackballs-418015bb9ae982a1975da7d79277c2705727a56894ba0fb246adaabb1f4632e3). You will use it in the next step.
You now need to extract the outputs that need to be blackballed. Use one of the following:
./mdb_dump -s blackballs-<hash> /folder/with/blackball/database/ | awk '/[0-9a-f]{64}/{print $1}' > /output/path/file.txt
./mdb_dump -s blackballs-<hash> /folder/with/blackball/database/ | grep ^.................................................................$ | tr -d \  > /output/path/file.txt
The resulting .txt file can be imported into the official GUI and CLI.
Comment: For the record, the database name will always be blackballs-418015bb9ae982a1975da7d79277c2705727a56894ba0fb246adaabb1f4632e3 for mainnet, which is what the vast majority of people will need a list for.


Storing beer in a keg

Question: After beer is done fermenting can I move it to a keg not carbonate it and let it sit for a long time? Or could it sit for a longer period of time after being carbonated?
Comment: I had a batch sitting in a secondary (glass carboy) for a month (at cellar temperature) because I had left for vacation.  I bottle-conditionned after that, and it turn out great.  Important things for preservation are: no air and cool temperature.
Comment: How long is "a long time"?
Comment: A month or two. The way it sounds is I can have a keg pressurized by co2 and continuously drink out of it for a couple of months. Does that sound right to you?
Answer: I do this regularly, not using a keg, but e.g. a glass container.

Clean and disinfect well before usage
Make sure that you do not splash when transferring

What I also do is add some extra sugar to start a little fermentation to let the CO2 blow out the rest of the air after transfer. I use 4g per litre of volume that needs to be filled (you do need an airlock then of course).
However, it also depends of the kind of beer you have made. This is better for strong beers than for light beers. I do this for bock, barley wine and imperial stout.
Answer: This would seem to be the same process as storing beer in a "brite tank" to allow it to clear after fermentation. Using a clean keg is always a good idea but I have found it sufficient to scald the keg using a kettle of boiling water. However I do clean and rinse the keg after use and before storage.
One could leave the beer to clear in a barrel/keg/secondary bin without adding any sugar and I have done this for periods of two or three weeks without any ill effect on the beer.
I agree with the comment above about adding a small amount of sugar/glucose (dissolved in a minimal amount of boiled water) to allow some continued fermentation to scavenge the oxygen from a closed keg while conditioning/ageing. However almost 100g for a 24 L keg is sufficient to carbonate it for dispensing from the keg. If one wanted to store it less or "un"-carbonated then approximately 20g of sugar would be sufficient to start minor fermentation and scavenge the oxygen in the closed barrel. There would be little point in doing this for an unsealed keg/barrel.
Answer:
After beer is done fermenting can I move it to a keg not carbonate it and let it sit for a long time?

Bulk aging at cellar temps is generally not done in a keg, unless you use a spunding valve or something similar as if you leave it sealed, any pressure build up won't have anywhere to go and will carbonate the beer. The can have mixed results on the flavor of your beer.

Or could it sit for a longer period of time after being carbonated?

Generally, a carbonated and sealed ale will last a long time at cellar temps; the stronger (higher ABV) and more hops (higher IBU or dry hopped) the longer it will last.
Bulk aging after carbonation at fridge temps is also known as lagering.

The way it sounds is I can have a keg pressurized by co2 and continuously drink out of it for a couple of months. Does that sound right to you?

This sounds like a different question. Perhaps you should start with what it is you are trying to accomplish.

Storing beer in a keg


Higher ping in cs go can cause problem in registry of shots?

Question: I have not played CS:GO in steam for a couple of months. Now I have started playing again, I've noticed that despite playing on a server with a high ping (>300), I am still not lagging.
Is this high ping going to affect my shots registering?
Answer: Yes, it definitely will. You are most likely not noticing the lag because of interpolation.
A high latency will negatively effect any online game, most notably FPSses - in the case of Counter Strike latency is extremely important. I would recommend not playing on servers with a ping higher than 50, the lower, the better.
On a side note, look at high (128) tick servers which should give you a more competitive experience.
Answer: Traditional 'lag' and latency are two different things that people tend to associate and often occur together, but they have different effects.
With a high latency (ping), you're going to have issues giving commands rapidly, as you have to wait for the server to confirm them. For example, when scoping with a high ping it will take longer for you to appear scoped in than with low ping. The same is true with switching guns, picking up a new gun, firing, etc. Because of the way CS handles your shots, though, if you aim well you will still not have any problems with those shots hitting.
Lag is when that ping value is fluctuating significantly or you're getting loss or choke (dropped information, visible if the net_graph 3 setting is used). This will be a much more significant hindrance to you than a high ping will. This can cause clearly accurate shots to miss, will cause players to skip across the screen, can cause hangups where the game seems to freeze, and just generally sucks.
It's possible for players to have high ping and no lag, and it's possible for players to have low ping and be lagging terribly. I used to play on Australian servers from USE, and while my ping was around ~250-300 I was still able to play reasonably well, though the game feels a lot slower and more clunky.
You can change the maximum ping to servers that CS:GO will put you in through matchmaking with the following console setting, if you would like to have a lower ping:
mm_session_max_ping "100"


Developing your writer's voice

Question: I'm a relatively new writer and sometimes I feel like my writing is too bland and that I'm struggling to develop my writer's voice. Does anyone have any good tips?
Thanks
Answer:
Just keep writing. Writing is something you have to (and can) learn. So allow yourself the time (and many failures) to do so. Think of writing as being similar to learning a language or learning a craft. Practise makes perfect.

Write what you care about. If you are not emotionally involved in what you write about, it will not touch your readers either.
Since I do not know you, and people care about different things, I cannot recommend what that might be for you. But generally it helps if you put something of yourself into your characters, and something of your own experiences into your story. The despair you have felt when your first boy-friend dumped you can inform your portraial of a mother losing her first child; you love of Japanese manga can serve as a basis for the dedication of a scientist for his research. While the individual experiences differ, the basic emotions are the same across all people and allow us to feel compassion and understand each other. So use this to transfer what you know to what you haven't yet experienced yourself.

Have fun. If writing is torture, reading will be torture. Be honest with yourself and write only if you actually enjoy writing. Some people enjoy the idea of being a writer, but don't actually enjoy writing itself. You won't be successful if you do not enjoy the process, and would have both more joy in life and more success with whatever you do if you found out what you really want to do and did that. If you experience a lack of joy in writing, have the courage to explore your interests and do something else.
Answer: Maybe you already have a voice. It is difficult for writers to judge their own voices. You live with your voice all day long, in your head, so it seems normal to you, and boring. Other people (most of whom exist outside your head to some extent) don't live with your voice all day long.
What do other people say about your voice?
That said, I think there are things you can do to explore and refine your own voice. I like playing with writing exercises. Two kinds:
Goldilocks exercises. Pick something that you can vary about your writing. Sentence length, say. Take something you've written and rewrite it using sentences no longer than 10 words (or 7 if 10 is too easy). Notice the effects. Then rewrite it again using sentences no shorter than 25 words (or 35). Notice the effects. Given everything you learned from those two rewrites, rewrite one more time, focusing on how you can use sentence length to get the effects you want.
You can use goldilocks exercises for anything that you can use more of or less of. Like description. Describe a setting using no more than seven words. Describe the same setting using no more than 100 words. Notice the effects.
Tie one habit behind your back exercises. Pick any feature of writing. Rewrite a scene with no uses of that feature. None. Zero. No form of the verb "to be." No adjectives. No dialogue. No exposition. Notice what challenges that poses for you. Notice what you have to do to overcome those challenges. Now you know more ways to do whatever you normally do with "to be" or adjectives or exposition. Given what you've learned, rewrite your scene focusing on the effects of thing you just experimented with.
One more that doesn't fit into either of those categories: The Horrible Awful Brutal Word Count Massacre. Take a scene you've written. Remove ten percent of the paragraphs. Then remove ten percent of the remaining sentences. Then remove ten percent of the remaining words. Try to cut the least important paragraphs, sentences, and words, but you will have to cut things that matter. Count the words. That's your word count limit. Rewrite the scene to say everything the original scene said, but without exceeding your word count limit.
Choices. None of these exercises is about what it seems to be about on the surface. Eliminating "to be" is not (really) about eliminating "to be." It's about discovering the effects of "to be," and alternative ways to achieve those effects. That gives you choices. Same for sentence length. Same for word count. When you play with one variable, you learn unexpected things about other variables.
Each is about noticing the choices at your disposal, and the effects of those choices. Once you are aware of the possibilities, you can make the choices consciously for a while. Then they will fade into the background and become incorporated into the voice you are developing.
Your choices are your voice.
Comment: Fun ideas.  You must teach creative writing.
Answer: I always considered "finding your voice" something vague and meaningless, like "finding your inner you" or "finding your true self".
What happens in reality is this: you copy your favorite writers, and then, gradually, their style starts merging with yours (that is to say, your own feelings, your own thoughts).
Personal example: I started by writing like Haruki Murakami, but I don't like jazz so I don't include it in my writing. Neither cats, wells, or Japan (since I don't live in that country). I did keep his lyrical prose, surrealism, and use of metaphors, though--then mixed all that with my love for science, rationality, and philosophy. Also, I don't agree with writing a story that doesn't have a clear theme/meaning, so I decided not to pick that from him (he's still my favorite writer, though).
So, don't think too much about it. Just write.
And be careful, many writers use this finding-my-voice thing to procrastinate, to have an excuse to not to write.
Comment: I'd even go so far as to recommend consciously aping someone else's voice. It's an interesting exercise trying to write a story as Ray Bradbury, and then tell the same story as Ray Chandler.
Answer: I'm not the best at writing, but I do know a couple of things for you to remember if you still can't find your "voice".
Here is a quote:

This sentence has five words. Here are five more words. Five-word sentences are fine. But several together become monotonous. Listen to what is happening. The writing is getting boring. The sound of it drones. It's like a stuck record. The ear demands some variety.
Now listen. I vary the sentence length, and I create music. Music. The writing sings. It has a pleasant rhythm, a lilt, a harmony. I use short sentences. And I use sentences of medium length.
And sometimes, when I am certain the reader is rested, I will engage him with a sentence of considerable length, a sentence that burns with energy and builds with all the impetus of a crescendo, the roll of the drums, the crash of the cymbals–sounds that say listen to this, it is important. - Gary Provost

and remember, don't count words, count moments, and the detail that you put in to them needs to reflect the pace of what's happening.
Comment: +1 for reminding us of the often forgoten, yet vital, rhythm of writing.
Answer: I have two tips.
1. Read.
This probably sounds strange at first. But I find some similarities between writing and speaking. You learned your speaking habits from those around you--your parents and caretakers when you were younger, your teachers (hopefully, at least as far as grammar and vocabulary goes), and nowadays more likely your friends and acquaintances. You have the option to form your writing voice more consciously.
You find your own voice bland? Well, try to find some writers whose voices you think have qualities you admire. Maybe it's a sort of tongue-in-cheek humor, or understatements. Maybe it's a lot of detail, or maybe you admire how they simply hint at things and simultaneously make things very clear.
Read them a lot. Expose yourself to it as much as possible. Analyze if you feel like it, though I wouldn't say analysis is absolutely necessary.
2. Write.
It's your voice, and you can only develop it by exercising it. If you find a few authors you like, according to tip #1, try imitating their style. Heck, if there's a radio talk show host you like, or you think your English professor is witty, try imitating their way of expressing themselves in writing.
Developing a voice takes time, and practice, but I'm a firm believer in effort and practice, not talent, being the key to success.
EDIT: You may also find How do you find your unique style? helpful, and my advice is essentially the same as the first answer there. Heh. Only saw that afterwards.
Comment: Thank you very much, everyone. Your comments have been most helpful.
Answer: A few scraps of advice I heard along the way:

All great writers are great readers.
Write every day.
Burn the midnight oil.
Answer: Please read this interview with the writer Joan Didion:  [Paris Review, Fall/Winter 1978]1  She is one of the greatest prose stylists in the 20th and 21st centuries, and here's one thing she said when asked about her greatest influence:
"I always say Hemingway, because he taught me how sentences worked. When I was fifteen or sixteen I would type out his stories to learn how the sentences worked. I taught myself to type at the same time. A few years ago when I was teaching a course at Berkeley I reread A Farewell to Arms and fell right back into those sentences. I mean they're perfect sentences. Very direct sentences, smooth rivers, clear water over granite, no sinkholes."
She literally wrote out Hemingway's sentences.  In the end, her voice and Hemingway's could not be more different, but she studied what she loved and it contributed greatly to her own development as a writer.
Read a lot.  Study the writers you love.  Write from the heart.  Your writing will grow into its voice over time.
Answer: your voice is to some extent a composite of the voices you read. Read lots of different authors of all different heritages, occupations, styles, and subjects. It's like eating a variety of healthy foods, or solving a bunch of different types of problems: you pick up a lot of handy tricks for your repurposing/improvement.

Developing your writer's voice


Which is correct: こんばんわ or こんばんは?

Question: I've seen both こんばんわ and こんばんは used; which is correct here? If we interpret the は as the topic particle, は would seem correct, but it seems that わ is used quite frequently anyway...
Answer: こんばんは is correct.  The former is mostly a stylistic/emphatic usage.
Answer: こんばんは is correct, according to that page in Japanese.
My gut feeling is the same - 今晩は -> こんばんは.
That said, a cursory Google of こんばんは yielded 13M hits, whereas こんばんわ yielded 26M.
Answer: こんばんは (今晩は) is the one in the dictionary for "Good evening!". I think that こんばんわ has a cuter feeling, maybe a little softer. It's a total guess, but it might be related to the feminine わ at the end of sentences. Actually, this page seems to be saying it's related to 和 (わ - peace) which gives it a nicer feeling.
Answer: こんばんわ is cuter.  こんにちは is more correct/formal/proper.
Answer: The right way is always こんいちは, こんばんは with the particle "HA, は" It's like that because it's the old Japanese way to say "good day". the "ha / は" works the same as "is": "Anata ha, watashi ha" 「あなたは」, 「わたしは」 meaning something like, "today is a good day" etc. After some time, it becomes fused in everyday colloquial language. Also, we should not forgot that Japanese Kana only represents "sounds of spelling". We are allowed to write こんばんわ with "wa", but we need to check where we are using it. This way of using "wa" can only appear in informal text such as web chats, with close friends, and manga. For any document that is official or with strangers it's mandatory to use the formal way, with "ha" and preferentially using kanji with the particle 今日は, 今晩は.
Answer: Both こんばんは and こんばんわ sound the same as the ha (は) in こんばんは sounds like wa with its current context so basically there is literally no difference between the feeling that わ adds since it doesn't make the it sound any different, just making it clear not delivering hate.

Which is correct: こんばんわ or こんばんは?


Doesn't the sarcomere contract during isometric contraction?

Question: During muscle contraction, the lenght of the sarcomere changes, length of myocyte changes and so does the length of muscle. However, if the length of muscle is not changing length as in isometric contraction does it mean that the sarcomeres are not contracting?
Answer: Yes, sarcomeres do contract during isometric contraction, they just don't change the overall length of the muscle. This is due to the tension being transferred to elastic filaments within the muscle that maintain the same muscle length but increase the muscle tension. Thus, this is how sarcomeres can contract while the muscle does not have an overall change in length. (See this link for a paper discussing these elastic elements within the muscle itself; also, this is discussed at this wikipedia link as well).
In an isometric contraction the sarcomere is increasing the tension in the muscle, but without an overall change in length. (Isometric Contraction = No change in length, but INCREASE in tension)
Once a muscle overcomes the tension needed to lift a weight/load, then the tension ceases to increase but the sarcomeres begin to shorten which moves/lifts the load. When the length of the sarcomeres change and the tension remains the same, that is called isotonic contraction. (Isotonic Contraction = No change in tension, but DECREASE in length)

The picture below is from a website discussing these muscle physiology principles and is freely available on the web.
Comment: I learned something new... looks like the sarcomeres can contract during an isometric contraction, though this doesn't mean the muscle contracts. What appears to happen is that the sarcomere contracts but the tension is transferred to elastic filaments in the muscle which maintain the same muscle length but increase the tension - this is how sarcomeres can contract while the muscle does not (see http://jcb.rupress.org/content/105/5/2217.full.pdf+html for more info) - I will add this to my answer
Comment: I vaguely recall having studied that even though there is sarcomeric contraction, there is no reduction in length in isometric exercise due to equal compensatory relaxation of sarcomeres elsewhere.. is this true? If not how is the length maintained despite contraction?
Comment: so, *contraction* (in the sarcomere context, not the muscle) need not mean decrease in sarcomere length right?