# Most Liked Content

### #332511How Long Until We Could Make A Real Sword Art Online (sao) Nerve Gear Type De...

Posted by on 30 July 2014 - 02:43 PM

Moderation note: This is the original post that lead to the creation of the FullDive Technology” subforum. Posts have been moved from it into other threads, according to subject, to make them shorter and more readable.
This thread is for discussion of how to make an actual brain-computer interface like the NerveGear shown in the Sword Art Online anime

If you have seen the hit anime Sword Art Online (or S.A.O for short) you most likely know what the nerve gear is and what it does. Going into this though i will explain what it exactly does as if no one has ever heard of it. The Nerve Gear is a VR device (or virtual reality device). I have posted pictures as to what it looks like . Through the device every sense is being used. When you are in the game you smell the things around you, you can taste everything you eat. You can see and hear everything around you in a photo realalistic enviroment. You can feel everything as if it were in the real world right in front of you. (Please note the sensation of touch and feel is not to the of the real world though.) When i say you can  feel things i mean each type of feeling, mechanical reception the feeling of contact, thermo reception the feeling of hot and cold, stretch reception the feeling of muscle compression, kinestesia the sensing of body movements, proprioception the sensation of a body's place, and equilibriaception the sensation of balance. So i will break down what we have and what we will most likely have in the near future if everthing goes right that has to do with these five senses. Photorealistic graphics are expected to be around by the year 2020 as predicted by the scientist Michio Kaku. (thats two years before S.A.O is even released in the anime). Headphones are already great and will only get better with time. With taste and smell finding the answer will exponentially help the as the two senses are so closely related. touch is the big one here, there are many devices to simulate each type of touch i described but it would need to be all in one and need to all fit with in the helmet used as it is the only peice of equipment used in the show (though it is connected to a strong pc). the device would only need to touch your head and still give you feeling anywhere on your body. As for the controls they are completly controlled through the brain. You have the full range of movement that you have in the real world in the game, (without ever actually moving in real life). I would imagine this would be done through an EEG (electroencephalogram) that could take the brain's electrical signals used to move and redirect them into a computer that would us them as movement commands. By the way none of this is invasive so nothing has to connect into your body. So give your ideas to how far along we are to doing this and new tech that would make this possible. i personaly plan on going to college to create such a device so please lets start a discussion about this. i believe this is all possible because if humans put there mind to it anything can be created. An example of this is the atom bomb, everyone thought it was impossible to split an atom but we did it and now we have nuclear generators and reactors.
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### #332524How Long Until We Could Make A Real Sword Art Online (sao) Nerve Gear Type De...

Posted by on 31 July 2014 - 03:13 PM

Welcome to hypography jacob2mitts! Please feel free to start a topic in the introductions forum to tell us something about yourself.

How Long Until We Could Make A Real Sword Art Online (sao) Nerve Gear Type Device?
I’ll approach this question by break down what the Nerve Gear helmet in SAO and the SAO MORPG computer program is shown doing:
• Simulating a realistic world for many (on the order of 10000) simultaneous users
• Reading brain states with sufficiently high spatial and temporal resolution
• Analyzing in real time the read brain states to create input data for #1
• Writing brain states with sufficiently high spatial and temporal resolution
IMHO, #1 could be done now. Note that the simulated world doesn’t need to be a truly accurate simulation, modeling very complicated things like weather and biology, only accurate enough to give the appearance of a real world. Such simulation parallelize well, so the computer hardware necessary to run them scales well – the size of the simulated world and number of users can be increased to within reasonable limits by adding hardware.

#2 and 4 are harder questions, both to state precisely and to answer. Notice my use of the wiggle-word “sufficiently”. To the best of my knowledge, we don’t at present have a good guess as to how high a spatial resolution is necessary to capture the data needed for #3. However from well-known brain data, we can estimate a resolution that must be sufficient, though the actual needed resolution may not need to be so great.

The number of neurons in the human brain is about 1011, its volume about 0.0012 m2 (source: this 2013 Nature Article). From this, you can calculate the spatial resolution necessary to image individual neurons: about 0.00001 m (10 microns).

For temporal resolution, we know that the fastest changes in nerves - their “action potentials” – is on the order of 0.001 seconds (1 milisecond)

Present day fMRI brain imaging machines have a maximum spatial resolution of about 0.002 m, and a temporal resolution (how long they take to capture a full brain image) of about 1 second. To the best of my knowledge, the temporal resolution of fMRI could be increased by a factor of 1000 without undue difficulty – there’s no great drive to do so, because its current performance is good enough for its primary use in medicine. The spatial resolution, however, I understand has a theoretical maximum of about 0.0001 m, 10 times to course to image individual neurons. (source: this 2000 conference paper draft)

The conclusion I get from this is that, unless the actual needed resolution for #2 is much less than individual neurons, MRI technology isn’t feasible. MRI has the highest resolution of present-day non-intrusive brain imaging technologies, so either an entirely new approach is needed, or an intrusive one.

My best guess is that an intrusive technology is needed – many fine insulated wires inserted into the brain. So, rather than the neat helmet in SAO, something like the wiring implied by the “brain plugs” shown in 1999 film The Matrix,

though I imagine the connectors could be made nearly invisible, rather than the ugly industrial looking spike and socket shown in the movie. It’s possible that hardware could be implanted in the brain along with the wires, allowing a magnetic or radio rather than a hard-wired connection to the outside.

Once function #2 has gotten the brain data, is has to transfer it to a computer for fuction #3, analyzing the data. Taking the above, this requires a transfer rate of at most 1014 bits/second. This rate, though about 1,000,000 times higher than in commonplace hardware, has been achieved. The actual rate needed would be much less, because all of the neurons in the brain don’t fire in the same millisecond.

Compared to #2, imaging the brain in sufficient resolution, I don’t think #3, analyzing the brain data, would be terribly difficult. For a single user, it would, I expect, require more computer than running the MORPG, though, so in present-day technology, a top-of-the-line supercomputer would be needed for each user.

#4, writing to the brain, is so far beyond present day technology it’s hard to sensibly speculate about. There are some present-day devices that stimulate the brain non-intrusively, using magnetic fields, but they are very low resolution, affecting whole brain areas on the order of 0.01 m in diameter. Though useful in medicine for treating some brain diseases, they can only “write thoughts” in a very crude manner, such as causing temporary reduction in thinking or memorizing ability, or the perception of vague flashes of light.

Again, this leads me to conclude that a true “read-write” brain interface like the one suggested in SAO would need some sort of wired brain connection.

Function #2 – reading brain states – is also needed to “upload your mind” into a computer, a dear goal of extropians, transhumanists, and others of this ilk. 9 years ago, we had the thread Upload your mind into a computer by 2050?, discussing futurologist Ian Pearson prediction that this would be possible by 2050. This seems a not unreasonable guess for when at least the “read” part of the Nerve Gear from SAO might be possible –more likely, I think, than 2022, the Reki Kawahara (the novelist that wrote SOA, starting with the first light novels in 2002) prediction for a complete read-write one.

An important question to ask before going too far in trying to duplicate a fictional nonintrusive, direct brain read-write device, is whether this is really the best approach. My hunch is that it’s not, and immersive VR that “writes” to our existing sense organs – eyes, ears, and skin, etc. – while “reading” our motor nerves, is.

Another good question to ask is, given that pretty good virtual reality systems (eg Virtuality, a line of home and arcade systems) existed in the early 1990s, why wasn’t it popular, and why is so little of it around now? Given that consumer electronics technology is driven in large part by what proves popular, we’ve decades of evidence that gamers don’t want VR, preferring systems with keyboards, handheld controllers, 2-D displays, and speakers or headphones.

I’m looking forward to seeing how the latest, and perhaps best-funded forays into VR, the Oculus Rift and Sony’s Project Morpheus, do commercially. Recent reports are that some very good games for these systems will be available late this year or early 2015. If these games are very good, but are not popular, my suspicion that VR itself is not popular will be bolstered.
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### #302433Can Science And Religion Coexist Peacefully?

Posted by on 01 December 2010 - 05:13 AM

I doubt it. Science is empirical, religion is dogmatic. At best, science can view religion as a failed hypothesis. The argument goes that the two operate in different spheres and should each be able to do its thing in peace. But that's exactly where the problem lies, because religion makes claims that interfere in science's domain. Religion makes claims that their god, or gods, are responsible for people recovering from illness, for physical occurrences like rainfall, etc. And to expect a failed hypothesis to be respected for no other reason than the sheer number of people who take it to be the truth, is disingenuous. The Truth is not a democracy, and should not be held as such. It's immaterial if there are 2 billion Christians world-wide, or only five. Without any evidence apart from the self-referential Bible, it is not worthy of any more respect than the notion that the moon is made of cheese. For that same argument, Hogwarts must be a real place, because it is written about in the Harry Potter books.

So, to make a long story short, I don't see how religion and science can peacefully co-exist and why religion should expect any respect other than the same passing glance a scientist will give any other failed hypothesis. Why would it be deserving of respect, in any case? Can I demand of you to respect the color green, because I believe that it has magical properties? That's roughly how ridiculous religions' expectation of undeserving respect is to the non-religious.
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### #235431My belief in Global Warming is getting shaky

Posted by on 09 September 2008 - 04:06 AM

Sorry to disappoint, but check out his wiki.

Kininmouth is a science adviser to the Science and Public Policy Institute, formerly the Center for Science and Public Policy.

William Kininmonth (meteorologist - Wikipedia, the free encyclopedia)

The New York Times reported that in 2002 Frontiers of Freedom received $230,000 in funding from Exxon.[5] The institute received$90,000 in funding from ExxonMobil in 2006[6]

Science and Public Policy Institute - Wikipedia, the free encyclopedia

Quote any more of these fellows and I'll just laugh. All these sad old accusations have been answered. The 'outsiders' are often sincere, but get cranky and are prone to seeing conspiracies where only good science has been offered. They don't like the peer review process, but that's science. Tough. If they don't like the way science is conducted, or the scientific method that checks their silly claims, then maybe they should take up Sci-Fi novel writing? Oh, I forgot, they already are.

EG: The 'blanket' strawman attack took the metaphor used by the IPCC to explain the process to laypeople, and debunked that as if it were a scientific claim, and the apparent 'confusion' with the basic radiative forcing equation is a technically worded slight of hand. Really, are we to believe that the 30 major climate institutions around the globe... the real peer reviewed ones that is... ALL made the same mistake on the BASIC PHYSICS?

Give me a break!

Check this list of complying organisations...

Scientific opinion on climate change - Wikipedia, the free encyclopedia

Contents
[hide]

* 1 Statements by concurring organizations
o 1.1 Intergovernmental Panel on Climate Change (IPCC) 2007
o 1.3 Joint science academies' statement 2008
o 1.4 Joint science academies’ statement 2007
o 1.5 Joint science academies’ statement 2005
o 1.6 Joint science academies’ statement 2001
o 1.7 International Council of Academies of Engineering and Technological Sciences
o 1.8 European Academy of Sciences and Arts
o 1.9 Network of African Science Academies
o 1.10 National Research Council (US)
o 1.11 European Science Foundation
o 1.12 American Association for the Advancement of Science
o 1.13 Federation of American Scientists
o 1.14 World Meteorological Organization
o 1.15 American Meteorological Society
o 1.16 Royal Meteorological Society (UK)
o 1.17 Australian Meteorological and Oceanographic Society
o 1.18 Canadian Meteorological and Oceanographic Society
o 1.19 Canadian Foundation for Climate and Atmospheric Sciences
o 1.20 International Union for Quaternary Research
o 1.21 American Quaternary Association
o 1.22 Stratigraphy Commission of the Geological Society of London
o 1.23 International Union of Geodesy and Geophysics
o 1.24 International Union of Geological Sciences
o 1.25 European Geosciences Union
o 1.26 Canadian Federation of Earth Sciences
o 1.27 Geological Society of America
o 1.28 American Geophysical Union
o 1.29 American Astronomical Society
o 1.30 American Institute of Physics
o 1.31 American Physical Society
o 1.32 American Chemical Society
o 1.33 Engineers Australia (The Institution of Engineers Australia)
o 1.34 Federal Climate Change Science Program (US)
o 1.35 American Statistical Association
* 2 Noncommittal statements
o 2.1 American Association of State Climatologists
o 2.2 American Association of Petroleum Geologists
* 3 Statements by dissenting organizations
* 4 Scientific consensus
* 5 Surveys of scientists and scientific literature
o 5.1 Oreskes, 2004
o 5.2 Bray and von Storch, 2003
o 5.3 Survey of U.S. state climatologists 1997
o 5.4 Bray and von Storch, 1996
o 5.5 Other older surveys of scientists
* 7 References

Oh, and that "# 3 Statements by dissenting organizations"?

Statements by dissenting organizations

With the July 2007 release of the revised statement by the American Association of Petroleum Geologists, no remaining scientific body of national or international standing is known to reject the basic findings of human influence on recent climate.[46]

The reason your dude and his "institute" are not listed? Well, they're more of a lobby group than a credible scientific organisation. If they don't like the scientific method... let them have their silly parties and rants to the already converted in scepticism. If the subject wasn't so serious I'd be less annoyed and more amused by them, but the trouble is people BELIEVE these guys based on a mishandling of the data, and EVERY one of their TIRED old objections has been handled repeatedly... but they simply will not recant.

Got any more? Come on... quote something from the list of 26 myths. You know you want to.
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### #348063Forums Have No Credibility

Posted by on 29 May 2017 - 08:44 AM

Am I the only one here who sees the irony in someone who has an opinion that forums have no credibility, posting that opinion on a forum? Is this an example of an Epistemic Paradox?

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Posted by on 16 October 2014 - 11:20 PM

Moderation note: This thread is for conversations by people seeking to volunteering to work with others, and people seeking to recruit volunteers.

Posts of this nature made in threads discussing neuro and computer science will be moved here.

Craig and Jacob I am Simply Commenting to say i look forward to a nerve gear being here shortly and I too have decided that would go to college specifically to learn exactly what to do and what is needed to create a nerve gear or amusphere gaming headset i hope one day ill get to meet you Jacob since you decided to do the same maybe we can work together on it in the future. Thank you Craig for your insight but i will dedicate my life to making this even if it doesn't turn up to be very popular. Once again Thank You guys.
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### #326243The Digital Demise Of Darwinism

Posted by on 11 February 2013 - 06:53 PM

The genetic code of life really is digital, like the code underlying computer software. I’ve always been compelled by the analogy: The genome as the software instructions for embryology. But I think it’s telling where the analogy breaks down.

Computer programs are replete. Instructions are concise & there is very little waste. Repetitive code is consolidated & channeled through subroutines, even where space is available. Anyone attempting to analyze or reverse-engineer any software today can unfailingly follow the principle that any bit of code that presents itself must do something - else it wouldn’t be there.

The genome, OTOH, is chock-full of repetition, as well as genes that are never expressed, genes that are expressed but do nothing, genes that turn on genes that do nothing, genes that turn on genes that have already been turned on.... et cetera, as well as great valleys and “deserts” of non-coding material. The genome is, IMHO, not only some of the best evidence that life is not engineered, but a strong message that not all digital coding is the result of engineering.
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### #318343Global Warming In The Media And In Fact

Posted by on 30 May 2012 - 09:24 PM

Why is there always ambiguity when this type of information is presented?

It takes a longer time, and more space, to explain the nuances and resolve ambiguities.

From a chemistry/biochemistry point of view, it is just about the balance of fossilized carbon and airborne carbon--or stored carbon and released carbon. Is the carbon in the air or the ground? That carbon balance can affect temperature by several degrees, relative to a background of conditions that set the planet's radiative balance.
===

It is important to answer your question, about CO2 levels, differently depending upon which scale of time--as well as the planet's evolutionary status--you are looking at. Multiple of 5 are convenient, since the planet is roughly 5 Billion years old, and life on land started roughly 500 Million years ago--10% of planetary time--and the dinosaurs were "gone" by 50 Million years ago (Mya)... and humans arose by 5 Mya--the last 1/10 of 1% of planetary time.

CO2 levels were 6 times each of those numbers you mentioned--either 280ppm or ~350ppm--probably ranging from lows of 1000 or 1200 ppm up to 2000 or 2500 ppm during various eras of those Dinosaur Times; and since life first came up onto the lands, ~500 Mya, and the continents were positioned very differently.
===

Throughout most of the past 500 Million years, nutrient-poor (and carbon-poor) Tropical Soils predominated globally. But for the past 50 Million years, Earth has been on a fairly stable (cooling) course; a path where Temperate Soils finally were able to evolve and dominate--soils that could support productive agriculture.

So before the last extinction event, 65 Mya, Temperate Soils only existed near polar latitudes. After much recovery and the rise of the mammals (especially herbivores) and the grasses, the past 50 million years have cooled enough to allow Antarctica to ice over. The Temperate (carbon-rich) Soils moved into the mid-latitudes (aided by the grass/dung/soil cycle) and continued drawing CO2 levels lower as fossil soil resources (carbon rich) developed and increased. The Atlantic grew to favor a global conveyor of cold deep water, as other ocean currents developed when the continents came to approximate their current position, over the past 20 to 30 million years. The Arctic also developed during this more recent half of the past 50 million years, when Temperate Soils became predominant, and the planet continued to cool--and the four seasons were finally able to evolve--consigning the tropical world to the equatorial latitudes.

During the past 5 million years, after the planet cooled enough for Ice Age conditions to predominate, humans developed. And then at ~500 kya we came to use fire as a tool to better manage our resources. That enabled tool use (~50 kya) and finally agriculture (~5 kya) to intensively and extensively manage those fossil soils (which had brought CO2 levels down to "pre-industrial" levels). Even today, agriculture creates 1/3 of greenhouse gas emmisions globally.

Is current global warming really a big deal, when compared with this previous global climate?

Humans are shifting that long-evolved balance between airborne carbon and carbon stored in the ground. If we want to survive as a civilization, we shouldn't shift the balance too quickly or too far. Management of that carbon balance would be a good goal for humanity. We have succeeded in preventing the return of global glacial conditions, but we also now need to prevent the return of global tropical conditions, which will degrade our precious arable soils and reduce crop productivity and agricultural yield.
===

So comparing Cretaceous CO2 levels with today is like comparing something on two different planets. Limit your comparisons of Quaternary conditions to those of the Tertiary--the last 1% of planetary time--at most, unless you add some significant adjustments and qualifications. If you want to see how CO2 affects climate today, you should probably limit the comparisons to times when other conditions more closely matched current conditions--to between 5 and 50 million years into the past (or look at the PETM ~55 Mya as a cutoff). The closer you get to current geologic time--looking at the past 5 million to 500,000, or even the past 50,000 years--the easier it is to compare historical CO2 levels.

Also, many of CO2's effects take from decades to centuries to be fully manifested, as with melting ice sheets. Recently, the levels have changed too fast for an accurate comparison with past levels (and the effects of those past levels), since the past levels changed more slowly and maintained the same level (or fluctuated around a mean) for much longer periods of history. Check into the Miocene and Eocene climates if you want a long-term benchmark for comparison with currently projected levels.

Understanding Earth's Deep Past, National Academy of Sciences, 2011

"By the end of this century, without a reduction in emissions, atmospheric CO2 is projected to increase to levels Earth has not experienced for more than 30 million years."

Thirty million years worth of change, within a century; wow.

That is before honeybees, earthworms, we, or our cereal crops evolved.
That will counteract the effect of the Milankovitch Cycle on global glaciations.

I wonder if there will be any consequences to biodiversity and evolution.

~
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### #307754Live After Death

Posted by on 01 June 2011 - 10:47 AM

The lead of the film, in her youth, liked talking over the radio. There are several flashbacks to her childhood and we learn soon that her mother died in childbirth. In one of the flashbacks she's talking to her old man and asks if they could reach mum over the CB radio. The father replies that there probably isn't a radio powerful enough to reach that far.

My mind starts wandering a bit about how to treat this state of affairs to a child. What would be a correct (honest, coherent), response to a posed question like 'where's mum gone?'.

I think the correct response to this question is the same when answering a child as when answering an adult, any difference being just phrasing and added explanation to compensate for the child’s smaller vocabulary and knowledge.

An honest response depends, of course, on who’s making it. A devout religionist who truly believes it may honest answer “she’s gone to dine at the right hand of Jesus in heaven” or any of myriad religious depictions of an afterlife. I don’t believe in such things, so an honest answer from me (which, as a rule, I endeavors to be the only kind I ever make) is very different, and a bit more complicated.

I pretty much agree with the views Douglas Hofstadter wrote in “I Am a Strange Loop”, which hold that who “I”, or “mum”, or any other human being, is, is essentially a program for being who we are, a collection of data and rules for using it that determines what we know, how we behave, and more intangibly, how we feel. Though most of this data is “hosted” in the brain of the person it defines, small bits of it are hosted in other brains. When I say “I know mum”, what I mean is that I have much scaled-down version of the “who am I?” model hosted in her brain in my own. If I “know mum well”, my model and hers agree most of the time – I know most of what she knows, know what she’ll do in a given situation, and can accurately empathize with how she feels or would feel in a given situation.

When mum dies, her brain stops “running the program” that is her. It’s irreversibly wrecked – in short time, no imaginable technology could get it running again, in its original, now decomposed hardware, or extracted into something else. However, the smaller versions of the “mum model” program in my brain, and those hosted in the brains of others that know her (I’m intentionally avoiding using the convention tense of “knew”) continue to run.

That’s how I’d answer the question: Mum’s in me, and in you, especially when we think “what would mum do?” or do the things she once did. As long as we remember her, she does, in a reduced but not entirely different way than when she was “remembering herself”, still exists in essentially the same way she every did.

I’d end the answer to a child in this specific scenario here.

Sadly, Hofstadter notes, and I agree, you and I too will likely die someday, and while people who never met mum when she was alive in her own brain may host small “mum models” formed from our describing her to them, these models will be smaller and less “knowing” than ours, so someday, in all likelihood, her model won’t be hosted in recognizable form in any brain – she’ll be almost or entirely forgotten, as someday, will be you and I.

However, I can’t help but go on to wonder if some people aren’t somewhat exempt from being forgotten in a generation or two. For example, when a passionate musician performs the music of Beethoven or Jimi Hendrix, trying to evoke the feel of it, they may be truly “running the same program” Ludwig and Jimi were when they performed it. If we believe that these parts of the Ludwig or Jimi model programs their long-decomposed brains once hosted were important parts, then in an important way, they’re alive in the musician – especially ones who’ve studied their biographies in an effort to “know” them. And as, at any given time, hundred of musicians are playing Beethoven and Hendrix with empathic passion, they are actually hosted on much more “hardware” now then they were when they were alive.

This gets more complicated when we consider that many of us “get” our Ludwig and Jimi models second-hand, from orchestras and other musicians, say Stevie Ray Vaughan. Ludwig and Jimi had influences, so their models are built in part from others’. Far enough down this road, one starts to wonder where the ideas that influence us end and the “us” that is us begins, and how important this distinction really is.

The tentative moral I offer here is: be great, and you may live a very long time, or if greatness is beyond you, be part of something great. The boundries that separate the “I”s of us from one another and from the “it”s of ideas may be less important than we think.
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Posted by on 30 May 2011 - 08:03 PM

seems like the closer you get the more beautiful the flower is
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### #227095New bird family tree

Posted by on 11 July 2008 - 12:02 AM

Let me try... (BTW, by surprising I don't mean everything in it is brand new information. I'm just contrasting it with what was believed a few years ago.)

Here it is:

Starting from the left, the first branch to split off (Q) is the ratites, or “primitive” flightless birds like ostriches, rheas, emus, kiwis, etc. This group also contains the tinamous, South American birds that can fly. The composition is not a surprise, but it is a surprise that the Australasian flightless birds are more closely related to tinamous than to non-Australasian ratites.

The second branch (P) contains the Anseriformes (“primitive” waterfowl such as ducks, geese, etc.) and the Galliformes (gamebirds, such as pheasants, guineafowl, etc.). No surprises there.

With the third branch and its two main branches (M and N) things get really messy (and has an ornithologist or two in a tizz). Columbiformes are pigeons, the next three families in N are mesites, sandgrouse and tropicbirds, and the last two orders are flamingos and grebes respectively. The relationship between the last two has long been suspected, as has that between pigeons and sandgrouse, but until recently no-one thought N formed a clade. Tropicbirds were thought to be related to pelicans, frigatebirds, gannets and other shorebirds (order Pelicaniformes) while mesites were placed in Gruiformes (see later).

In M the relationship between Apodiformes (swifts) and Caprimulgiformes (nightjars) was expected, though their placement and closeness to clade N was not until recently.

The two Gruiformes (traditionally consisting of cranes, crakes, rails, etc.) are the sunbittern and kagu. The Gruiformes has been gruesomely dismembered and its parts scattered all over the tree. (At least ornithologists were puzzled by the above two birds; some of the scatterlings they were not even thinking about.)

J has also raised eyebrows. Opisthocomus at the base of it is the hoatzin of South America, which has variously been considered a cuckoo, a chicken, a turaco, a rail, or a seriema. Truth is, taxonomists didn’t know what to do with it. (They still don’t.)

Group I, surprisingly, allies some of the Gruiformes (ones mentioned here include cranes, limpkins, finfoots and rails) with the cuckoos (Cuculiformes). Even more surprisingly, bustards (Otididae), groups with cuckoos, rather than with Gruiformes as expected.

H makes rather a mess of the waterbird orders. Shorebirds (Pelicaniformes) were thought to be quite distinct from waders (Ciconiiformes), although a relationship was suspected. The first 11 genera are: Anhingas, cormorants, gannets, frigatebirds, great herons, boatbilled herons, American white and scarlet ibises, shoebills, hamerkop, pelicans, and storks. Procellariiformes (tubenoses – marine birds such as albatrosses and petrels) seems to yield no surprises. A few years ago, however no-one would have thought their closest relatives were penguins (Sphenisciformes). Another surprise is that, at the base of this huge waterbird clade, are the distinctly terrestrial turacos (Musophagiformes), which were thought to be closer to cuckoos.

The long branch going to G is for convenience, not an indication that the next group is very distant from the first. The “higher” waterbirds order, Charadriformes (waders, gulls, auks, plovers, jacanas, etc.), remains fairly intact - though Turnix (buttonquails) and Pedionomus (plains wanderers) were once considered either Galliformes or Gruiformes.

The two families of E are (1) the eagles, kites, kestrels and (not usually included, but close, the secretarybird) and (2) the condors and New World vultures. The last were at one time thought to be related to storks.

Mousebirds (Coliiformes) end up as sisters to owls (Strigiformes), which is surprising – but, to be honest, no-one knew where they belonged anyway.

C contains the hornbills, hoopoes, toucans, woodpeckers, kingfishers, etc. The only mild surprise is that trogons seem to belong here.

The placement of Falconiformes (falcons) is surprising, as falcons were, until quite recently, considered members of the eagle family!

Psittaciformes (parrots) as sister group to the passerines is a huge surprise. Not too long ago it was thought that their closest relatives were pigeons, right at the other side of the tree.

The Passeriformes is by far the biggest order, and contains most of the dinosaurs in the average garden – finches, canaries, crows, etc. It is a natural order that goes undisputed. I just wonder what the poor rifleman (Acanthisitta – a very ordinary-looking little New Zealand bird) did to be cast out so far on a limb?
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### #170508Oh wow, Time for SEX! (picture post)

Posted by on 20 April 2007 - 03:00 PM

Made ya look. Perhaps im an ***, but this is sex nonetheless:hihi:

Some cacti are flowering! most are now ID'd, have to admit, cactus classification sometimes makes me hate taxonomy alltogether!!!!!!

http://img.photobuck...ophflower11.jpg

EDIT: i guess i did not show the actuall sex, as i am no pervert! i will say, however, there was a baggy, forceps and a little blue paintbrush involved.

on a side note, does that smiley look like "agree"?

Enjoy the flowers
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### #158641Evolution vs. Creationism

Posted by on 13 February 2007 - 06:45 PM

Evolution is an observed and documented fact, there is less reason to deny evolution in favour of creationism than there is to think sardines live in tins.
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### #126777Large Structures in Space

Posted by on 19 August 2006 - 01:07 AM

Science fiction has always played host to the idea of having large structures in space. From Dyson spheres to Death stars, these structures lay firmly in the realm of fiction, but will it always be this way? Human technology is growing at an alarming rate, now with the dawn of the space age behind us the sky is no longer a limit. If our technology continues to grow exponentially it seems logical that we will eventually be able to build such structures, but even logic must give way to physics in extreme cases. While it may follow logically, it will be physics that has the last say, whether it is physically possible to build these structures depends on a wide range of factors. Some of these factors include: size, material composition, availability of materials, stability etc.

One of the most famous of these large structures would have to be Dyson Spheres. They where first put forward by Freeman Dyson in 1959, in "Search for Artificial Stellar Sources of Infrared Radiation" in Science. Freeman Dyson was a Cambridge graduate where he did his bachelor degree of arts in mathematics; he then went on to become a Professor of Physics at Cornell University. Dyson himself admitted that the idea was not entirely his own, he was inspired by a book called ‘The Star Maker’ written in 1937 by Olaf Stapleton. It is even thought that Olaf may have got the idea from J. D. Bernal.
There is some confusion concerning what a Dyson Sphere is actually meant to be like. The original proposal was that by having many individual satellites orbiting about a star it would be possible to collect a large portion of the stars energy output. There are some other more fanciful theories that take a Dyson Sphere as a solid continuous sphere, which can even be lived in.

The idea of a Dyson Sphere comes from the constant need for more energy. It is theorised that as humanity continues to grow it will always be in need of more and more energy. To demonstrate the progression to using solar energy, these calculations have been included.
- The sun puts out 3.827*1026 Jules every second.
- The Earth has a radius of 6,378km this gives it a cross sectional area of:

Ae = 2*pi*(6,378x102)^2
Ae = 2.556*10^14 m^2

- The Earth orbits the sun at a radius of 1.496x10^11m, this makes the surface area of a sphere at that distance:

As = 4*pi*(1.496x1011)^2
As = 2.812*10^23 m^2

- Earth makes up a percentage of this sphere:

Ae/As * 100 = 9.088*10^-8%

- Hence Earth can only capture a small amount of the suns total energy output:
9.088*10^-10 * 3.827*10^26W = 3.478*10^17W

Albeit this is a tremendous amount of energy, but the entire Earths surface must be covered to get this energy. Even then there is looses from the atmosphere, clouds and our equipment.
One day in the future we may have the need to get more energy than this and a Dyson Sphere is one such solution.

For the purpose of energy collection a great many solar collectors surrounding a star would suffice as a solution. Though this solution is also going to be fraught with difficulty, imagine navigating swarms of satellites, thousands of them, each with their own individual paths. This would make maintenance and energy collection very difficult, though it remains the more physically plausible solution.
There are other uses for a Dyson Sphere that would require it to be solid, or at least continuous. For example if a civilisation wanted to hide themselves for security reasons or needed more space to live, a Solid Dyson would be required. The resources required to create a solid sphere would be truly enormous. If you wanted to live in the sphere and it was around a star that is like our sun, it would have to have a radius of one astronomical unit. For a sphere of radius 1Au and thickness y meters would have an approximate volume of:

V ≈ 2.812*10^23y m3

This means for a Sphere of just 1cm thick the volume of matter would be 2.812*10^21m3. This is twice the volume of the Earth. As you can imagine a 1cm think cube couldn’t be very strong, but if you increase this to even 10cm the volume quickly becomes more than that of all the matter in the terrestrial planets and asteroids in the solar system! This fact doesn’t make a solid Dyson Sphere impossible, just impractical. The impossibilities may lie in whether or not such a structure would be stable or not.

The effect of the spheres gravity on the sun is not a worry, since the net gravitational force of the sun due to the sphere will always equal zero. This can be thought out logically. If the sun was at the center of the sphere it would have equal amounts of mass distributed at the same distance from it in all directions, this all cancels to a net force of zero. While if the sun was off center then the side it is closest to would have a stronger field strength due to less distance, but at the same time it the opposing side now has more mass behind the sun and though it is further away these effects perfectly cancel each other out.
The suns gravity has no such cancelling effect and hence will have an effect on the stability of the structure. There have been theories that the gravitational force due to the sun on the sphere could be negated and the sphere essentially held up by radiation pressure and the solar wind. This is not to be confused with the solar wind, the solar wind is made up of high speed particles emitted from the sun. While it may have some effect and help hold up the Dyson Sphere, it is negligible, only 1% of what radiation pressure will do. It may sound absurd that light could hold up the sphere, but it may be possible for very low density materials. Radiation pressure is stronger the closer you get to the sun, this is a problem as gravity also gets stronger the closer you get, so this means it doesn’t matter how close or far away, no distance is at an advantage for this purpose.
For an object that absorbs the incident radiation, which for a Dyson Sphere made for energy production it will presumably absorb most light, the force per m2 (or pressure) of the sphere due to radiation is:

Fr = L/(4*pi*r2*c) N/m^2

Where L equals the luminosity of the sun (3.827*1026W) c equals the speed of light (3x108ms-1) and r equals radius of the sphere.
The force per m2 of sphere due to gravity is:

Fg = (Msun*Ds*x*G)/r^2 N/m^2

Where Msun equals the mass of the sun (1.99x10^30Kg), Ds equals the density of the Dyson Sphere, x equals the thickness of the sphere, G equals the gravitation constant (6.67x10^-11m^3 kg^-1 s^-2) and as before r equals the radius of the sphere.
Hence the net force of the sphere would be:

Fnet = L/(4*pi*r^2*c) – (Msun*Ds*x*G)/r^2 N/m^2
= (1.02x10^17)/r2 – (1.33x10^20*Ds*x)/r^2 N/m^2
= (1.02x10^17 – 1.33x1020*Ds*x)/ r^2 N/m^2

For an Fnet of zero, ie forces balanced:

0 = (1.02x10^17 – 1.33x10^20*Ds*x)/ r^2
1.02x10^17 = 1.33x10^20*Ds*x
Ds*x = 7.65x10^-4

Hence if we where able to make a Dyson sphere out of aerogel - the least dense substance know to man at just 1.1kg/m^3, the sphere could only be 0.000695m thick, that’s less than a millimeter! Clearly a solid Dyson Sphere would not be able to support itself with radiation pressure alone! This means that it would have to rely on the materials own structural integrity. Whatever the material is it would have to be something with a very high tensile strength, relatively low density and also be very abundant in the solar system.

Another Large Structure is a Ring World or a Halo. It is a large ring that is habitable on the inner side. This idea is most famous from the recent video game series ‘Halo’ from which so far three books have sprung.
The main reason a civilisation would want to create one of these rings would be for habitation. For one reason or another, a civilisation may find that they are out of space on their home planet, or perhaps due to climate changes their world is becoming inhospitable to life. They will then need somewhere else to go. Some systems may have another planet to go to, while others may not. If travelling to another star system all together is out of the question – either due to not having the capabilities to travel the vast distances in between star systems, or not having enough ships to move a large part of the civilisation – a ring world may become an option in such a crisis.
The ring could be constructed in an orbit around the sun matching that of the planet, or even perhaps in orbit around the planet itself. The ring could be inclined to the sun at such a way as to have half in darkness and half in light, so that if it is set rotating at the right speed it would have a normal day/night cycle.
The concept of a ring world is much different from a Dyson Sphere, while inhabiting the inner side of a Dyson sphere was only a late addition to the theory; a ring world is solely intended for that purpose. This means that one way or another, the ring is going to have to supply its own gravity. Doing so by mass is out of the question, so we must look to more artificial means of creating gravity or at least simulated gravity. Since we have no means By far the easiest way of doing this would be to spin up the ring. The spin creates an centripetal force that makes objects stick to the inside of it, much the same way that a bucket of water spun around on Earth will not spill. The gravitational force can be calculated thus:

F = (mv^2)/r
ma = mv^2/r
a = v^2/r
Where r is the radius of the ring and v is the velocity at which it is spinning.
Hence to have Earth like gravity of 10ms^-2, a ring of radius r would have to be spun at:

V = √(10r)
If you want the ring to resemble Earth like conditions and have a 24 hour day, then:

Period of one rotation = 24*60*60 = 43200 seconds
Then:
V = (2*pi*r)/86400
From above:
√(10r) = (pi*r)/43200
10r = (pi2*r2)/(1.866x10^6)
re-arranging:
r = 1.890x10^9m
v = 1.374x10^5 m/s

This velocity may well prove to fast to implement in practice. It may be necessary to have longer days so the ring is allowed to spin at slower rate.

When building one of these rings for habitation, one of the main factors will be useable living space. Assuming that all of the operating parts can be stored within the ring, and that the inner surface is totally useable, then the habitable area would be:

A = 2*pi*r*w

Hence:

A = 11.88x10^6*w km2

Where w is the width of the ring in km. If the ring was just 10km wide it would have 80% of the land area that Earth does. This leaves plenty of space for farming and living space; water can be stored in the ring itself, with small lakes for aesthetic purposes.

Basically if you want more space to live in you have to increase the width.
If you increase the width then the mass is going to go up. With increasing mass means an increasing amount of energy will be needed to make it spin. The rotational kinetic energy for a hoop is:

Kr = ½mrv

With the values found previously that is an energy of:

Kr = 1.30x10^14m J

This is a tremendous amount of energy and it may or may not be available to the race at that time, but the function of the ring depends on it, or else no gravity, no day night cycle. This amount of energy could be achievable through the use of antimatter. It could be set up to have many thousands of boosters around the outside of ring where antimatter is annihilated with normal matter. During an antimatter/matter annihilation all mass is turned into energy in the ratio of E=mc^2, since c^2 is such a large number (9x10^16), these reactions allow a high energy yield from a small amount of mass. That said for the purposes of spinning up the ring, you would require 0.72g of antimatter per kilogram of the mass of the ring. To produce such a large amount of antimatter the civilisation would have to have quite an efficient means of creating it. Recently released data by CERN stated that when their facilities are fully operational, they will theoretically be able to produce 10^7 antiprotons per second. So to produce that 0.72 grams of antimatter it would take us approximately 1.44 billion years! And that’s not even considering how the antimatter would be stored until use, that in itself could prove quite a feat.
There are yet still even more problems that need working out, problems that conceivable solutions are yet to be found. For example I have not addressed how the atmosphere of such a ring would be maintained. Earth has an atmospheric pressure of 101kPa at sea level, but we can survive in much less – astronauts only have 30% of that when they go EVA but then the oxygen level is increased to compensate. This would become a problem for metals that are susceptible to corrosion. Even then, trying to maintain the atmosphere at 30% of Earths could still prove difficult, if not impossible. As one possible solution to overcome the problem of leaking atmosphere, some designs have the ring enclosed and like a giant tube, this is plausible but would require a lot more materials.

In order for a ring world to be constructed many engineering feats would have to overcome. The stresses on such a structure would be enormous. It may be necessary to have supporting spokes like that on a bicycle wheel. Just like a Dyson sphere, to provide the strength needed it would probably have to be constructed out of some exotic form of matter that we are yet to discover.

A fictional large structure that is also worth mentioning is the Death Star for the famous Star Wars saga. The death star has a much different function than that of the previous two I discussed; the death star is a weapon. It is a weapon of far greater power than any ‘weapon of mass destruction’ that we know of. The death star is able to destroy a whole planet, reducing it all to a floating mess of asteroids. The first death star constructed was 160km in diameter, large enough to be mistaken for a small moon. It was constructed to enforce the Imperial’s totalitarian rule over the galaxy. There is not much insight into how the weapon and manoeuvring systems, only that they are powered by a hypermatter reactor. Since there is no such thing (as yet) called hyper matter, the death star remains firmly in science fiction. However the concept that one day a weapon of this magnitude could be constructed remains evident.

Isaac Newton once wrote “to myself I seem to have been only alike a boy playing of a seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me.” Newton had only scratched the surface of what science would one day be able to do. These days we may have lifted our head slightly and started uncovering small parts of this vast truth, but there will always be more to learn. Taken with what we know right now, these ideas of large structures may seem impossible, but with what we may know one hundred or even a thousand years in the future, these structures may become a commonplace. The sky is no longer a limit.

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### #103996LaTeX Fomulas: Math v2.0

Posted by on 11 May 2006 - 10:32 PM

NOTE: I am in the process of reworking this, it is still a decent reference, but i will be working on it, so expect changes

Intro:
This has been a long coming, endless traps have been setting the math evolutionary progress back throughout time, and you, Physics and Math people have been forced to use simple text equation display techniques to show complex math. Well, be that no longer, as i am about to introduce you to the world that no longer follows the standard text rules, it defies the normal thought, depends only on how far you are willing to take it and has no rivals in the realm of
 Microsoft
. I will attempt to teach you how to block the evil force from taking control of you, make you free as in freedom, to be what you want to be and know no limit. And when the forces of evil can no longer hold you down (and i am referring to M$IE support for CSS 2 and 3), you will enter the new realm of Latex.  how's that for an intro? Actually, it is quite sad that this hasn't happened any earlier, we are a scientific community, so the need for something like this, has bound to be around from very early on in the game (back when Uncle AL, TeleMad, FreeThinker, Gahd and Tormod ran the "Math and Physics" show). But i do have this to say, the software really hasn't caught up with this until early last year, so i guess it's just been ignored or something. Latex itself is a language, similar to HTML, but with major differences; it is a typesetting language made to be able to generate files that will be printable on many different types of printers. Latex is actually a dialect of Tex that was created by D.E.Knuth, it includes many plugins to the original Tex, including the one that i will describe to you today, one created for math. So what is the major difference between Math v1.0 and Math v2.0? Well its simply this, say you have an expression, and in Math v1.0 you would write it like such: f(x)=integral from -infinity to x of (e^(-t^2))/(radical(pi^x))dt uh, yeah, its kinda hard to follow, and some people would actually need to write it out to understand what is going on.... Wouldn't it be easier if you said just: $f(x)=\int_{-\infty}^x \frac{(e^{-t^2})}{\sqrt{\pi^x}}dt$ So, finally arching your attention? I sure hope so, because i am excited as well, and it is not that difficult to write this expression, in latex it looks like this: f(x)=\int_{-\infty}^x\frac{(e^{-t^2})}{\sqrt{\pi^x}}dt It may seem a bit much, but trust me, this will be a breeze once you get it. Basics: BB Tags Hypography uses a $tag to signify the beginning and$ tag to signify the end of a latex section of the post. Tags are surrounded by square brackets such as [tag] and respectively [/tag]. I strongly urge you to not forget to close the tags, it is not vital, but it is a good practice, even if you only plan to display an expression Tex Characters: Most characters in latex are rendered as the regular characters, such as a-z 0-9 () {} [] *$ % and so forth $a-z 0-9 () [] * \ \%$. Some need escaping, such is the case with $and % in our previous case, escaping means putting a \ in front like \$. But latex introduces some characters that have a meaning and render things differently (for math purposes) such characters would include the underscore (_) and the carat(^). Those characters are used to identify sub and superscript, respectively; for example a_b renders as $a_b$, a^b renders as $a^b$. Latex also has a load of characters that are not defined by regular keyboards, they are special characters and follow the following syntax: \name. Things like \alpha, \beta, \gamma, \delta, \pi and many many others are included ftp://tug.ctan.org/pub/tex-archive/info/symbols/comprehensive/SYMLIST
Those character commands are case sensitive, so \delta $\delta$is different from \Delta $\Delta$.

to be continued...

Continued

Size:
Latex supports many size options, the new software lets us support all of it, but for simplification reasons, any text you type, enclose it in the \text{} tag, you can actually control color, font and size from within those, but to simplify the size for you:
\tiny $\text{\tiny{tiny}}$
\small $\text{\small{small}}$
\normalsize (default)$\text{\normalsize{normal}}$
\Large $\text{\Large{large}}$
\LARGE $\text{\LARGE{even larger}}$
\huge $\text{\huge{huge}}$

I highly recommend using the default size... its just text

You have probably noticed, but latex in math mode also removes spaces thus not making it ideal to write normal text. Another thing to notice is that it outputs an image, however it is partly so, this image is dynamically generated and actually does not get saved on our server; it only exists in your browser, hence linking to it from other websites may be a bit harder then you'd expect, and if the outside traffic picks up too much, i will have to block anyone from the outside domain to be able to use this program...

Spaces and Styling:

Spaces are not mandatory, however i encourage my readers to use them to avoid confusion, for example you can write \frac{2}{x} and it will render as $\frac{2}{x}$, however this is fine it still presents a problem, if the fraction is x over 2 then \frac{x}{2} will not work, latex will render the command as fracx and that is not a valid command and hence a problem is due. To avoid confusion i recommend sticking to a good syntax style, such as using popper curly braces and spaces, you can either write that fraction as \frac x2 or using the prototype you should really get used to writing \frac{x}{2} that way you will not have to remember the braces when a complex fraction is due and the fraction or any function for that matter will come out right the first time. On the topic of spaces, i can see that people will ask about newlines and things of that manner. You can actually write text and use newlines and things of that nature. A new line is represented by a \\ and if you needed to write text, you can use the \text{} mode to write it and spaces and such will be used. For example y=\left\lbrace\begin{array}{c c}{2x+5} & \text{if x is less then 1/2} \\ {\pi{x}}^e & \text{if x is more then 1}\end{array}\right. $y=\left\lbrace\begin{array}{c c}{2x+5} & \text{if x is less then 1/2} \\ {\pi{x}}^e & \text{if x is more then 1}\end{array}\right.$ Latex actually provides spacing commands \, \: \; \quad \qquad, those take no arguments and (a\,b\:c\;d\ e\quad f\qquad g) renders as $(a\,b\:c\;d\ e\quad f\qquad g)$

Latex has a couple of fonts, here's how to use them:
\mathnormal - default - $\mathnormal{A B C d e f 1 2 3 \delta \Delta \infty \lceil \rceil}$
\mathrm - default without italic lower case - $\mathrm{A B C d e f 1 2 3 \delta \Delta \infty \lceil \rceil}$
\mathit - italic -$\mathit{A B C d e f 1 2 3 \delta \Delta \infty \lceil \rceil}$
\mathbf - bold - $\mathbf{A B C d e f 1 2 3 \delta \Delta \infty \lceil \rceil}$
\mathsf - sans serif - $\mathsf{A B C d e f 1 2 3 \delta \Delta \infty \lceil \rceil}$
\mathtt - mono space - $\mathtt{A B C d e f 1 2 3 \delta \Delta \infty \lceil \rceil}$
\mathcal - caligraphy - $\mathcal{A B C d e f 1 2 3 \delta \Delta \infty \lceil \rceil}$
\mathfrak - fraktur - $\mathfrak{A B C d e f 1 2 3 \delta \Delta \infty \lceil \rceil}$
\mathbb - blackboard bold - $\mathbb{A B C d e f 1 2 3 \delta \Delta \infty \lceil \rceil}$

you can also choose to bold a symbol (such as a greek symbol)
\boldsymbol
$\boldsymbol{\Delta} \Delta$

also there are times when latex does not render something quite to your personal spacing specifications, sometimes you need to add or subtract a small space to "nudge" things into place, for this they created a set of spaces for "nudging"

\: 4/18
\; 5/18
\! -3/18

the negative space is handy for places like this:
$\left(\begin{array}{c} n \\ r \end{array}\right) = \frac{n!}{r!(n-r)!}$
it looks good, but it could look better
$\left(\!\!\!\begin{array}{c} n \\ r \end{array}\!\!\!\right) = \frac{n!}{r!(n-r)!}$

Brackets, Braces and More:

Ofcourse latex supports every imaginable and unimaginable bracet and brace you can ever imagine, from the simple [] () to over and under braces, and more. The curly brackets have their own symbol, as they are used in the syntax, \lbrace and \rbrace will render as $\lbrace\rbrace[\math]. Also braces brackets and such render as their default size unless they are specified to do differently, so if you have a complex fraction that you need to be bracketed, say [\frac{(\frac{x+3}{7})+5}{3x+8}] will render as [math][\frac{(\frac{x+3}{7})+5}{3x+8}]$ however to actually extend those brackets you can use \left and \right flags to do the job, so with the addition of them \left[\frac{\left(\frac{x+3}{7}\right)+5}{3x+8}\right] $\left[\frac{\left(\frac{x+3}{7}\right)+5}{3x+8}\right]$.

Now as promissed the unimaginable stuff. These things are referred to as math accents, and they include vector signs and things of that nature. So tags like \vec{} \hat{} \tilde{} \dot{} \ddot{} will output as $\vec{x} \hat{x} \tilde{x} \dot{x} \ddot{x}$. If you need an expression under the sign, the developers have also thought about you, the \widevec \widehat \widetilde do just that $\vec{xyz} \hat{xyz} \tilde{xyz}$. Not done yet, also available are \underline{} \overline{} that underline and overline text, as well as \overbrace and \underbrace that make horizontal braces as such $\overbrace{x+2}$. There's more to add though, as the sub and superscript come into play here, using it you can explain expressions such is that a1 a2 .. an are just referred to as ai in the matter, you can write that as \overbrace{a_1,a_2...a_n}^{a_i} $\overbrace{a_1,a_2...a_n}^{a_i}$ with the underbrace remember that you are trying to put stuff under the brace, so use the subscript sign (_) to accomplish the task. Also once again, notice that proper use of brackets is the key, it is easy to make a mistake in the expression, so use the advanced mode preview fearute.
Also available symbols:
\langle and \range $\left\langle xyz\right\rangle$
\| $\left\| xyz\right\|$

[B]Common Math Needs:[/B]
Matixees, use the \begin{matrix} and \end{matrix} to display one
\left[\begin{matrix} a1,1 & a1,2 & ... & a1,n \\ a2,1 & a2,2 & ... & a2,n \\ ..... & ..... & ..... & ..... \\ am,1 & am,2 & ... & am,n \end{matrix}\right]
$\left[\begin{matrix} a1,1 & a1,2 & ... & a1,n \\ a2,1 & a2,2 & ... & a2,n \\ ..... & ..... & ..... & ..... \\ am,1 & am,2 & ... & am,n \end{matrix}\right]$

matrix uses no relimiters
pmatrix ()
bmatrix []
Bmatrix {}
vmatrix |
Vmatrix || ||

example:
A_{m,n} = \begin{pmatrix} a_{1,1} & a_{1,2} & \cdots & a_{1,n} \\ a_{2,1} & a_{2,2} & \cdots & a_{2,n} \\ \vdots & \vdots & \ddots & \vdots \\ a_{m,1} & a_{m,2} & \cdots & a_{m,n} \end{pmatrix}
$A_{m,n} = \begin{pmatrix} a_{1,1} & a_{1,2} & \cdots & a_{1,n} \\ a_{2,1} & a_{2,2} & \cdots & a_{2,n} \\ \vdots & \vdots & \ddots & \vdots \\ a_{m,1} & a_{m,2} & \cdots & a_{m,n} \end{pmatrix}$

like matrices arrays allow you to space your content horizontally as well as vertically, they also allow you to define the lining for it:

\begin{array}{c|c}
1 & 2 \\
\hline
3 & 4
\end{array}

$\begin{array}{c|c} 1 & 2 \\ \hline 3 & 4 \\ \end{array}$

similarly

$\begin{array}{c|c||} \hline 1 & 2 \\ \hline 3 & 4 \\ \hline 5 & 6 \\ \hline \end{array}$

or if you get really creative with them:

$\begin{array}{|r|l|} \hline 7C0 & hexadecimal \\ 3700 & octal \\ \cline{2-2} 11111000000 & binary \\ \hline \hline 1984 & decimal \\ \hline \end{array}$

There is more then a dozen common math symbols recognized in latex:
\arccos $\arccos{\left ( \frac{\pi}{2} \right )}$
\arcsin $\arcsin{\left ( \frac{\pi}{2} \right )}$
\arctan $\arctan{(1)}$
\arg $\arg{\left ( \frac{-1-i}{i} \right )}$
\cos $\cos{(\pi)}$
\cosh $\cosh{(x)}$
\cot $\cot{\left( \frac{3\pi}{2} \right )}$
\coth $\coth{(x)}=\frac{e^{2x}+1}{e^{2x}-1}$
\csc $\csc{(y)}$
\deg $f_m([X])=\deg{f[Y]}$
\det_ $\Delta_{\overline{a}} \det(A)=\overline{a} \times \overline{c}$
\dim $\dim{X}=-1$
\exp $\exp{(x)}=e^x$
\gcd_ $\gcd{(a,}=2 \sum_{k=1}^{a-1} \lfloor kb/a \rfloor +a+b-ab$
\hom $\hom{(X, Y)}$
\inf_ $\inf{\{1,2,3\}}=1$
\ker $\ker{T}:=\{ v \in V: Tv=0_w\}$
\lg $\lg{(2)}=\log_2{(2)}$
\lim_ $\lim_{x \to \infty}{(2x+1)}$
\liminf_ $\liminf_{n \to \infty}{(x_n)}$
\limsup_ $\limsup_{n \to \infty}{(x_n)}$
\ln $\ln{(2)}=\log_{e}{(2)}$
\log $\log{(2)}=\log_{10}{(2)}$
\max_ $\lim_{0 \to 1}\max{(x, 1-x)}dx=\frac{3}{4}$
\min_ $\lim_{0 \to 1}\min{(x, 1-x)}dx=\frac{1}{4}$
\Pr_ no clue when this is used, if someone figures it out, let me know, i will post example
\sec $\sec{(20)}$
\sin $\sin{\theta} = \cos{\left( \frac{\pi}{2} - \theta \right )}$
\sinh $\sinh{(x)}=-i \sin{(ix)}$
\sup_ $\sup{(X_n)}$
\tan $\tan{(x)}$
\tanh $\tanh{(x)}=\frac{\sinh(x)}{\cosh(x)}$
\infty $\infty$

[B]Stuff that didn't fit anywhere else[/B]
\not can be used with other symbols \not\in $\not\in$
\cancel $\cancel{ABC}$
\overset{a}{=} $\overset{a}{=}$
\underset{a}{=} $\underset{a}{=}$
\overrightarrow{abc} $\overrightarrow{abc}$
\overleftarrow{abc} $\overleftarrow{abc}$
\widetilde{abc} $\overwidetilde{abc}$
\widehat{abc} $\overwidehat{abc}$
\overline{abc} $\overline{abc}$
\underline{abc} $\underline{abc}$

\subtrack
$\sum_{\substack{ 0<i<m \\ 0<j<n }} P(i,j)$

more math stuff:
roots:
\sqrt $\sqrt{2}$
root of another power
\sqrt[#] $\sqrt[5]{2}$

\exists - $\exists$
\forall - $\forall$
\neg - $\neg$

brackets:
() \, [] \, \{\} \, || \, \|\| \, \langle\rangle \, \lfloor\rfloor \, \lceil\rceil
$() \, [] \, \{\} \, || \, \|\| \, \langle\rangle \, \lfloor\rfloor \, \lceil\rceil$

You are free to practice latex in this thread: http://hypography.co...ice-ground.html
I will try to answer them as well I can, and eventually others will be able to answer them as well as they can, but it will create only one thread to go to for answers about latex synthax.

Here is a good reference, and this is my reference for some of the things on this page: LaTeX/Mathematics - Wikibooks, collection of open-content textbooks

Thanks for your time, use math v2.0 wisely, and become free in your expression of math...
 Peace

• CraigD, TheBigDog, modest and 2 others like this

### #353093Why Is Gravitational Force Always Attractive ?

Posted by on 25 November 2017 - 11:52 AM

Why is gravitational force always attractive, as opposed to electrostatic forces, which is are both attractive and repulsive ?

It just is, according to observation. And of course, in general relativity (which is currently our best model) it is not really a force at all, but a manifestation of the curvature of spacetime by mass.

• Farming guy, petrushkagoogol, Dubbelosix and 1 other like this

### #351402Political Power Vs Mechanical Power

Posted by on 15 September 2017 - 01:11 PM

I do the interviews for the entry level positions on up to plant supervisors at the 6 water plants I'm responsible for. Having a college degree or state water license is now needed for every position. It was not like that 10yrs ago. So I end up forced to hire a recent college grad who is very intelligent, but doesn't know anything about plant operations, and he's trying to tell 30 guys who have been at the plant for twenty or thirty years what to do?  They just can't garner the respect and the guys take advantage of that when they can.

Then there is the other side of the coin with some 30yr employees, who know operations inside and out, who also have great people skills and all they lack is the degree. I can't put them in a supervisory role because they lack the paper. Our company pays the bills if they choose to go to college so long as it is somewhat relative to some part of our business. After working 8-9 hours most don't feel like going to sit at the community college for 4 hours 3 nights a week. They may be old-school and not very good or intimidated with computers so it dissuades them online courses too.

I do understand the need for higher education, but I've seen it too many times where my company has a person with 30 to 40 years of knowledge and experience on the sidelines doing something menial because of a rule. especially when you know they are capable of so much more.

As far as hiring I usually have 5-6 college kids come in for summer help while they go to school. They can cut grass and help operators, mechanics and technicians with their tasks. From this I get a good sense of what their work habits are and I have hired a few who showed promise. People will tell you anything you want to hear in an interview, it's best to see them in action.

• sanctus, Buffy, Farming guy and 1 other like this

### #3510989/11/2017

Posted by on 11 September 2017 - 03:25 AM

.
This thread is most certainly not promoting any errors with respect to date formats and their usages.

This thread is about what occurred on September 11, 2001, which never would have occurred prima faci had the events on February 26, 1993 come to full fruition.

Yes, I know what this thread is about. Sometimes we discuss tangential things that just happen to spring up, like date formatting. Because you start a thread, that doesn't give you control over everything that will get discussed here.

Did I earn a place on your ignore list yet? I would consider it an honor to be included with exchemist and Dr Kretin.

• sanctus, Farming guy, exchemist and 1 other like this

### #3510649/11/2017

Posted by on 10 September 2017 - 04:24 PM

What "inferences" could you make base on:

1. Today is September 10, 2017.
2. Tomorrow is September 11, 2017.
3. I quote from the OP, the last line: "What will you be doing tomorrow?

The key problem with your logic here is that there is absolutely no justification for limiting the "inferences" we might be making solely to what you put in the OP. All of your other posts are fully relevant to my and other's assessment of your intent.

Can you make an argument that people should evaluate your behavior solely upon what you decide is relevant?

And quite frankly, how are we supposed to know?

You should be relieved of your job as Administrator. You are dangerous.

Yes, I've been called "dangerous" and many other things as well. Although never a "Likudnik." But I have been called a "Self-hating Jew," a frequent epithet among folks like Shapiro and Horowitz.

You are harassing me.

When you're given a warning by an admin about your behavior, you'll find that on most sites the admins pretty much fall into a Thin Blue Line. You've been here for all of 2 days and you're already telling us how we should run our forum or what things our members should and should not say.

I assume that your behavior here is pretty much what people experience of you in real life. How's that working for you?

Given how quickly people end up on your ignore list, I assume that within about a week there will be nothing left for you to read here.

We're happy to have new members join and contribute, but this is an existing community of people drawn together by common interests with accepted conventions of interaction, and it's up to you to figure out whether you fit in with us, not scold us for not fitting in with your view of the world. Does that make any sense to you?

You never know who's going to become your friend. Friends are always chance meetings,
Buffy

• sanctus, Farming guy, Deepwater6 and 1 other like this

### #3510149/11/2017

Posted by on 10 September 2017 - 03:32 AM

Is there anywhere in the world other than the USA which has this confusing date convention? For me, tomorrow will be 11/9/2017, and I won't be doing anything in particular.

Same here.

Nor, more perhaps to the point, seeing as I am a Londoner, do I do anything special on the anniversary of so-called "7/7", the 7th July London bomb attacks. And nor does anyone else.

This practice of commemorating terrorist attacks seems to me to play into the hands of terrorists by enabling them to feel they have permanently scarred the community, it cultivates an unhealthy sense of victimhood and it can all too easily be used by unscrupulous or politically motivated people to whip up emotions - in this case anti-muslim prejudice.

We should just get on with our lives as normal.

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