Seafloor Features Are Revealed by the Gravity Field - <AUTHOR> http://earthobservatory.nasa.gov/IOTD/view.php?id=87189 <comment><USER2> This reminded me of NASA's GRACE mission [1] that I recently heard about. It can track the depletion of California's aquifers (for example) based on the tiny changes in orbit of the two tandem satellites.

Was mentioned on a recent Still Untitled podcast episode by NASA CTO David Miller [2], the whole thing is worth a listen if you want to hear him eagerly talking about all the cool things NASA is up to.

[1] [http://www.nasa.gov/mission_pages/Grace/](http://www.nasa.gov/mission_pages/Grace/) [2] [http://www.tested.com/science/space/558108-return-rock- still...](http://www.tested.com/science/space/558108-return-rock-still- untitled-adam-savage-project-122215/)

</comment><comment><USER3> These maps were made by detecting small differences in sea surface altitude, and inferring the gravitation field. But changes in gravity can also be measured directly, using a gravimeter.

However, they tend to be finicky to work with--difficult to calibrate and to eliminate sources of error. After all, we know from Einstein that there is no measurable difference between gravitational acceleration and inertial acceleration (like, say, bumping a sensor).

Still, gravity seems like an area of immense promise for sensors of the future. We've spent immense effort improving and miniaturizing sensors for things like magnetic fields, electrons, and photons. But we've recently discovered--using gravity--that these things might represent only 5% of the total mass of the universe. We haven't even detected a gravity wave yet. We're just barely getting started at using gravity to observe and understand the universe.

<comment><USER4> _However, they tend to be finicky to work with--difficult to calibrate and to eliminate sources of error. After all, we know from Einstein that there is no measurable difference between gravitational acceleration and inertial acceleration (like, say, bumping a sensor)._

Gravity gradiometry is used in exploration geophysics. Typically this is done as a ground survey, taking measurements on a grid. I don't know how they do the error correction, but aerial gravity surveys can also be done. Obviously, the more stable the platform the higher quality the data, which is by De Beers used a zeppelin for surveys in Botswana looking for kimberlite pipes. This company [1] uses a BT-67 (an updated DC-3) as their fixed wing platform. The company I used to work for had a small gravity survey flown in the mid 2000s. When chatting with the technician from Bell, I facetiously asked whether they had considered an Antonov An-2 [2], and was surprised to hear that it had been (briefly) considered it as a platform.

[1] [http://bellgeo.com](http://bellgeo.com)

[2] [https://en.wikipedia.org/wiki/Antonov_An-2](https://en.wikipedia.org/wiki/Antonov_An-2)

<comment><USER3> When I studied geology we did a gravity survey along a road. The gravimeter was a big metal can; inside there was a weighted arm suspended by a spring. Measuring the differences in the static deflection of the arm gave us a reading of local gravity at each point along the survey.

The can had to be placed perfectly level, and sit for a couple minutes (to allow any vibration in the sensor suspension to dissipate) before taking the reading. We also couldn't take any readings when a vehicle was going past. Luckily this was along a fire road in the mountains, so there was very little traffic.

I've heard of both aerial and underwater (submarine or towed sensor) gravity surveys, and it's so impressive that they get usable data from a moving platform. I think one trick is to do multiple passes so that chaotic sources of error (like turbulence) average out at any given point--while real differences in gravitation would persist.

Edit to add: Going back to my comment above, I can't imagine how a truly portable (like, arbitrarily hand-held) gravity sensor could be developed, the way we have portable sensors for light, radio, sound, ambient pressure, magnetic field, etc.

<comment><USER5> Most of the moving measurements aren't gravimeters. They're gradiometers.

You don't actually get the same data out, and you can't use it in the same way.

The key part isn't just the acceleration due to motion. It's that you have to know your absolute elevation very precisely if you're using a gravimeter. Otherwise, the data you get can't be corrected relative to your other measurements and is more or less useless. (The method mentioned in the article actually measures the geoid directly by measuring the sea surface, which is an equi-potential surface.)

However, if we don't worry about the absolute acceleration due to gravity, and instead measure the local rate of change in gravity, we don't need to know elevation precisely.

That's referred to as gradiometry. You can't use the data in the same way, but it's still very useful.

In a nutshell, most of the movable gradiometry sensors work by using multiple accelerometers. Acceleration due to motion affects both equally (with some caveats when rotation comes into play). The differences in acceleration between the two accelerometers is therefore purely a result of the "tilt" of the geoid locally.

It's difficult to integrate this back into an accurate picture of what the free air or Bouger anomaly would look like, but it's still useful information. We can't necessarily calculate the same things from it, but it's a great edge detector.

</comment></comment></comment></comment><comment><USER6> Applying the reverse of this is actually really fascinating as well. A friend of mine used to work on "navigation systems for submarines". According to him some submarines measure the pull of gravity to help keep track of their location.

<comment><USER7> Some of these shipboard gravimeters originally developed for subs during the cold war ended up on research ships -- and are still on them.

In my old life I would tend to these instruments (still in operation). Finicky, old, entirely analogue systems ... but they keep "working" 35+ years later.

<comment><USER6> And here I thought this was cutting edge technology...

<comment><USER5> We've been doing gravity surveys for over a century. All you need is to 1) know the elevation precisely, and 2) have a very well calibrated spring.

In fact, the really old Lacoste & Rhomberg style gravimeters are often thought to be more accurate than their modern counterparts because the springs used to be very meticulously hand-crafted instead of mass-produced.

Even Sandwell & Smith's method for inverting for bathymetry from the Free Air Anomaly (i.e. local sea level) has been around for a long time at this point. (Still damned neat, though.)

The cutting edge stuff these days is in satellite methods that can measure gravity anomalies over land (e.g. GRACE and GOCE). They're still much lower spatial resolution than the sea-surface based methods, but you can use them over the entire globe.

GRACE, for example, measures the distance between two satellites ~100km apart to an accuracy of ~1 micrometer. Pretty impressive! GOCE has multiple very precise accelerometers at different ends of the satellite. Because acceleration of the craft will affect accelerometers equally, the differences in acceleration must be due to local changes in the geoid. (In other words, GOCE is gradiometry based.)

</comment></comment></comment></comment><comment><USER8> paraphrasing: Underwater mountains exert a gravitational pull on the water above and around them causing small but measurable bumps.

This is very cool! I never thought about the ocean as being bumpy.

<comment><USER9> And a similar thing happens with large rifts, except the bump goes the other way.

</comment></comment><comment><USER10> These maps use data from JASON-1; JASON-3 is launching soon, possibly in mid- January.

</comment><comment><USER11> Url changed from [http://gizmodo.com/heres-the-most-complete-ocean-floor- map-e...](http://gizmodo.com/heres-the-most-complete-ocean-floor-map-ever- made-1750109568), which points to this.</comment>


Nineteenth century machine that performs Fourier analysis - <AUTHOR> http://www.engineerguy.com/fourier/ <comment><USER2> The designer of this machine is the Michelson of Michelson-Morley, Nobel prize 1907; his interferometer was a brilliant apparatus that disproved the aether hypothesis. I'm surprised the blurb for the book doesn't mention who he was.

<comment><USER3> The fascinating thing about the Michelson-Morley interferometer experiment is that they were attempting to validate the aether hypothesis, and measure the Earth's absolute velocity relative to the aether. Instead they failed to do so, and the experiment showed that the speed of light is the same in all directions relative to all observers regardless of motion. A quite shocking and non-intuitive result that served as a foundation for the theory of relativity.

Even today most non-scientists do not understand or appreciate this result, they still operate within a mental model of the universe involving absolute frames of reference.

</comment></comment><comment><USER4> It would be nice if there was a resource that summarized the mechanical counterparts of these operations:

\- summing displacements

\- subtracting displacements

\- turning displacements into rotation

\- multiplying displacements by a constant factor

\- multiplying two displacements together

etc.

Using these primitives, any computation could be transformed into a mechanical device. One could even build a compiler for it! This compiler could take a program as input and a 3d-printable model as output. Happy coding! :)

<comment><USER5> [http://www.youtube.com/watch?v=s1i-dnAH9Y4](http://www.youtube.com/watch?v=s1i-dnAH9Y4)

</comment></comment><comment><USER6> How about an 18th century machine that performs Fourier analysis? A violin!

Also it has a really good numerical approximation of 2^(7/12).

Why? A violin has 4 strings. The lowest string in frequency is the G, the first G below middle C on a piano. The other three strings are, left to right to the player, D, A, and E. Each adjacent pair of strings differ in frequency by a musical _perfect fifth_ so that, three times the frequency of the lower string in the pair is the same as two times the frequency of the higher string in the pair. So, as move across the strings from G to D, A, and E, at each step are multiplying frequency by 3/2 which, then, must be, and is, a nicely good approximation to 2^(7/12) which is essentially what a piano is forced to do for those notes.

A lot in violin playing is from listening to _harmonics_ , that is, _overtones_ , that is _Fourier_ analysis.

Also that each string has a _natural frequency_ of vibration is essentially a Fourier point.

But, wait, there's more, and much earlier! Newton ran a beam of white light through a prism which is a Fourier analysis -- essentially a power spectrum via Fourier transform. Then Newton was smart enough (uh, he was a bright guy) to use a second prism and show that the individual colors could not be further decomposed. So, somehow the first prism did some fundamental decomposition.

Also, some armies knew that soldiers walking across a bridge should not march in step. Why? Because a Fourier analysis of the bridge might show that frequency of the marching was a _natural frequency_ of the bridge and could cause large amplitude motions of the bridge, failure of the bridge, and the army to fall into the water below.

The main parts of the human ear do a Fourier analysis.

X-ray diffraction is essentially 3D Fourier analysis.

<comment><USER7> Wouldn't the human then be performing frequency analysis, not the violin itself?

You seem to be conflating decomposition of a signal with generation of the same, and Fourier analysis with a lot of things. How does one take a "Fourier analysis" of a bridge? Isn't that just resonant frequency?

<comment><USER6> > How does one take a "Fourier analysis" of a bridge?

Give the bridge an 'impulse. Then it's Fourier transform is has all frequencies. Then see what the bridge does: Get out the transfer function of the bridge. It might have a peak -- then don't march the troops at that frequency. Or the output motion of the bridge is the inverse Fourier transform of the Fourier transform of the input to the bridge from the soldiers times the transfer function of the bridge. If the signal from the soldiers puts too much power at a frequency that is high in the transfer function, then that is a "resonate frequency" and the bridge is threatened.

For the violin, yes, the human ear does a lot of Fourier analysis with the little hairs inside that coiled up thing, whatever it is called, but for the violin I was considering the beats when bow two adjacent strings together. So, bow the A string at 440 Hz together with the E string at about (3/2)440 Hz, and listen to the third harmonic of the A string and the second harmonic of the E string -- they should be the same frequency. If their frequencies differ by x Hz, then the sound will have amplitude modulations, _beats_ , of x per second. That's how a violinist tunes the instrument.

The Fourier part? The sound from the A string is roughly periodic but not a sine wave. Similarly for the sound from the E string. Do Fourier analysis, that is, Fourier series on each of the two periodic signals. Take the third term from the Fourier series of the A string and the second term from the Fourier series for the E string, and listen to the beats. While the signals from each string are periodic, they are not sine waves, but the terms from the Fourier analysis are sine waves which is partly why the beats are so easy to hear. So, in effect, are using, say, the E string to find the Fourier coefficient of the third harmonic of the A string.

The A and E strings are separated in frequency by an _interval_ of a _perfect fifth_ which is 7 semi-tones or, from a piano, about 2^(7/12) which is close to 3/2\. Well, that's the story for a perfect fifth. But there is also a perfect fourth, 5 semi-tones, a major third, 4 semi-tones, and a minor third, 3 semi-tones, a perfect 6th, 9 semi-tones, and, of course, an octave, 12 semi- tones. In _perfect_ tuning, each of these intervals has, for the two notes, overtones with the same frequency (for two small whole numbers, one of them times the frequency of the lower note is the same as the other times the frequency of the higher note) so that can _tune_ the interval by listening to beats. Of course, the easiest one to hear is the octave.

So, when using two strings this way, really are doing a Fourier analysis using one string to take the Hilbert space inner product of the two signals and using a sine wave from one of the overtones and its inner product with the other signal to _scan_ that signal for beats and, thus, where the overtones are and, thus, really doing what Fourier analysis does, a projection via Hilbert space inner products onto orthogonal axes (sine waves at the overtone frequencies, that is, at frequencies that are whole number multiples, whole numbers again, of the frequency of the original periodic signal). So, adjust one of the two strings and in effect scan the sound from the other string for it's overtones -- that's essentially Fourier analysis. I will resist writing out all the math, but, really, a lot of Fourier theory is fairly intuitive stuff where a lot of the main ideas can be done with just pictures.

Or, yes, it would be a little simpler to play just, say, the A string and have an audio oscillator that puts out a sine wave and, then, slowly sweep the frequency of the oscillator sine wave and listen for beats with the sound of the A string -- that's essentially just Fourier series analysis of the periodic signal of the A string. But if don't have an audio oscillator handy, and use another string, say, the D or E string, and its overtones, each of which is a sine wave, and adjust the frequency of the D or E string and, thus, _sweep_ a selected (listen carefully!) overtone of the D or E string past selected overtones of the A string and do much the same as with the audio oscillator.

Gee, I knew there was some Fourier theory in there somewhere!

<comment><USER8> Hello, I just have to ask, are you suffering from mental illness? If you aren't, it may be a good idea to get to a GP/Doctor and get checked out. Your comments on this thread read EXACTLY like some of the writing I have read by a family member with Schizophrenia. Feel free the flag / down vote me, but if you aren't aware then it could potentially help a lot...

<comment><USER6> Let's see: (1) Make some progress learning to play violin. I did. E.g., I made it through not all of but over half of the Bach "Chaconne", regarded as great music and challenging by nearly all violinists. (2) Learn some Fourier theory, pure and applied. I did that, for work with the fast Fourier transform on sonar problems for the US Navy and other problems. Also I took some grad math courses that covered Fourier theory carefully, right, based on measure theory.

I wrote the material here quickly, and better explanations could be possible:

For a violin, when tuning, and really also for much of the playing, to get the frequency ratios correct, which is most of what playing a violin with good _innotation_ is about, use overtones, that is, the terms of a Fourier series expansion of a periodic (not necessarily sine or cosine) signal. In particular, when bow two strings together, i.e., at the same time, say, the A and the E, with the A already at 440 Hz from, say, a tuning fork, and slowly adjust the frequency of the E string, then are, in part, adding an overtone of the A string with the signal of the E string and, really, as adjust the E string, _sweeping_ in frequency, as in the terms of a Fourier series, a sine wave overtone of the E string the terms of the Fourier series of the A string. When that overtone of the E string gets close to the frequency of a term in the Fourier series of the A string, get _beats_ , that is, an amplitude modulation which violin students learn to listen for and hear. When the beats go from a few a second down to less than one a second and basically go away, then have found the frequency of the desired overtone of the Fourier series of the A string, that is, have essentially part of the Fourier series of the A string.

As do other cases of bowing two strings together, get to find more overtones: E.g., want to use a finger of the left hand on the A string to play B, C, C#, D and E. E.g., Beethoven's 9th Symphony has "Ode to Joy" and can play that in A Major with C# C# D E E D C#, .... Well, to get the B correct, bow it with the E string and look for a perfect 4th. For the C, look for a perfect major third. For the C#, look for a perfect minor third. For the D, bow with the open D string an look for an octave. For the E, bow with the E string and look for unison. In eadh case, as adjust finger on the A string, will be doing a sweep in frequency looking for a term in the Fourier series of the other string.

For the bridge, treat it as a linear system. Then given and input signal, to get the output, take the Fourier transform of the input, multiply it by the impulse response of the bridge, and then take the inverse transform. The impulse response is what get when hit the bridge with an impulse, that is, a signal with all frequencies with equal power. If the bridge has a _resonant_ frequency and the troops march with that frequency, then the product of the two Fourier transforms and the inverse transform will be large and the bridge might fail. Fourier transforms win again.

My comments on Fourier theory are fine and should be entertaining for the HN audience.

I wrote the remarks quickly and kept the content intuitive. If I wrote it all out in terms of measure theory, then I'd be still more difficult to read. That you found something objectionable with what I wrote is absurd.

Your remarks are ignorant about Fourier theory and/or just hostile to me. A guess is that I wrote something you didn't understand and, thus, you got hostile. Such hostility is not appropriate on HN.

Put the two together and the criticize what I wrote about where essentially Fourier theory pops up playing a violin. There's more, e.g., the image through a lens of a point source and, then, much of antenna theory, right, also for sonar, especially the phased array case. And there's the issued of power spectral estimation -- did quite a lot of that via Blackman and Tukey.

Right, the Michelson-Morley interferometer, like Young's double slit, is basically antenna theory and, thus, also Fourier theory. I omit the details of the math.

What I wrote was supposed to be fun reading.

There's nothing wrong with what I wrote. Maybe you don't like it; and of course it was not a full course in Fourier theory; and I omitted the math; but for much of a STEM technical audience it should have been easy to read.

Your medical diagnosis is totally wacko nonsense, incompetent, irresponsible, erroneous, inappropriate, insulting, and provocative.

Here's your logic: You know some sick people who write. You observe that I write. So, you conclude that I must be sick. Erroneous. Nonsense.

<comment><USER9> > What I wrote was supposed to be fun reading.

It was! As a (very) amateur-level musician and programmer, I greatly enjoyed reading your comment. It took a couple of times (because of my shaking understanding of Fourier transforms, _not_ your writing), but I understood your point in the end.

So thanks for sharing. I'm glad you're enthusiastic about this stuff, it'd make a great blog post.

</comment></comment></comment></comment></comment></comment><comment><USER10> This is apropos for the topic. Before the era of digital computers, ships used to use analog fire control computers.

It is fascinating to watch these. It reminds me to pay attention to the fundamentals, the particulars are only temporary.

[http://www.eugeneleeslover.com/VIDEOS/fire_control_computer_...](http://www.eugeneleeslover.com/VIDEOS/fire_control_computer_1.html)

</comment><comment><USER11> It's hardly 'long-forgotten'...

From Körner's book 'Fourier Analysis' (CUP, 1988):

"[...] Kelvin ... designed and built a ... machine (the harmonic analyser) to perform the task 'which seemed to the Astronomer Royal so complicated and difficult that no machine could master it' of computing the coefficients from the record of the past height [of tides].

Kelvin's harmonic analyser has a good claim to be the grandfather of today's computers not only because he obtained government money to build it but also because it represents the first major victory in the struggle 'to substitute brass for brain' in calculation. It is pleasant to record that Kelvin's instruments were so well adapted to their purpose that it took electronic computers 20 years to replace them.' \- p.30-1

and

'We have seen ... how Kelvin invented machines which could compute periodic functions from their Fourier series and conversely obtain the Fourier series of a given periodic function. One such machine was constructed by Michelson to work to a higher accuracy and to involve many more terms that previous models. (Michelson's ability to build and operate equipment to new standards of accuracy was legendary. Of his interferometer which he invented and used in the Michelson Morley experiments it was said that it was a remarkable instrument - provided you had Michelson to operate it. His experiments to measure the diameter of the nearest stars using an interferometer were not reproduced for 30 years.)" \- p.62

<comment><USER12> I love Körner's book: it is amazing, interesting, accurate, his personality shines through . . . . I spent quite a bit of time with it when we had debates about some of the technical issues underlying the machine. This book likely isn't the place to start your study of fourier methods, but it is THE place to end!

</comment></comment><comment><USER13> Direct link to the eBook PDF: [http://www.engineerguy.com/fourier/pdfs/albert- michelsons-ha...](http://www.engineerguy.com/fourier/pdfs/albert-michelsons- harmonic-analyzer.pdf)

Direct link the the accompanying video playlist: [https://www.youtube.com/watch?v=NAsM30MAHLg&list=PL0INsTTU1k...](https://www.youtube.com/watch?v=NAsM30MAHLg&list=PL0INsTTU1k2UYO9Mck-i5HNqGNW5AeEwq)

</comment><comment><USER14> An even older "machine" that performs Fourier analysis: a lens [1].

[1] [http://en.wikipedia.org/wiki/Fourier_optics](http://en.wikipedia.org/wiki/Fourier_optics)

<comment><USER15> I wrote a blog post[1] about the Fourier transform and lenses. Lenses taking Fourier transforms has surprising evolutionary effects.

[1]:[http://scottsievert.github.io/blog/2014/05/27/fourier- transf...](http://scottsievert.github.io/blog/2014/05/27/fourier-transforms- and-optical-lenses/)

</comment></comment><comment><USER16> If I remember right, this machine inspired the discovery of gibbs phenomena. One of the few times a mathematical result was seen in practice before writing it down on paper.</comment>


The surprising and continuing influence of Swami Vivekananda (2012) - <AUTHOR> http://online.wsj.com/news/articles/SB10001424052702303404704577305581227233656 <comment><USER2> If you're interested in someone who both loves Yoga & meditation, and tends toward a rational bent, you should also check out Gopi Krishna.

[http://en.wikipedia.org/wiki/Gopi_Krishna_(yogi)](http://en.wikipedia.org/wiki/Gopi_Krishna_\(yogi\))

He was a pretty normal guy living a pretty normal life in the 1900's, and in his 30's through meditation he had a textbook enlightenment experience which resulted in a metamorphosis of sorts that he ultimately came to believe was biological / physiological in nature and could be repeated in others. He's one of the first if not the first person to suggest that what we think of as enlightenment is actually a biological event that the human body can perform given the right triggers, rather than simply a different state of mind or frame of thought. This is a revolutionary idea if you think about it; talk about "hacking the brain". The great thing about him is he's very relatable and not aloof, he kept his job as a government clerk and aside from selling a small handful of books, was clearly not interested in making money off his ideas.

He tried for years to raise interest in the scientific community to study the phenomenon, but of course grant money is hard to come by, and doubly hard if you're doing anything remotely unconventional, so his research foundation never took off and he passed away in I think it was 1981.

A lot of people don't know about him, but they've started putting his books on Kindle so you can go check them out. All of them are extraordinary reads, although I'd start with his prose, and then move to his poetry if you're interested in that.

[http://www.amazon.com/Gopi- Krishna/e/B00IPU7XD4/ref=sr_ntt_s...](http://www.amazon.com/Gopi- Krishna/e/B00IPU7XD4/ref=sr_ntt_srch_lnk_2?qid=1411864845&sr=8-2)

<comment><USER3> Maybe this is a wrong context to ask this question. Can someone tell me what exactly is a mystical experience and how it differs from normal human experience. When does one consider himself enlightened?

<comment><USER4> A mystical experience happens through unity, an everyday human experience through duality.

Duality is when you unconsciously make a distinction between you and your thoughts and perceptions. "I think therefore I am" is the subject observing his thoughts, this is duality.

When you silence your mind, you just are and then there is no opportunity for you to define yourself, to make distinction between what you are and what you're not. "I am all that is" is the subject realizing there is no separation between him and his perceptions, this is unity.

Yoga is one systematic way of cultivating this silence that is required to access those mystical states of mind.

As for enlightenment, I could not say because I'm not ;).

</comment></comment></comment><comment><USER5> Some brilliant quotes from this :

>> Faith, he wrote, must be based upon direct experience, not religious platitudes.

>>More presciently, he warned that India would remain a vanquished, impoverished land until it "elevated" the status of women.

So apt with current state of affairs in india!In fact (am from india) , every time any female from family (female) has to go out , a male always accompanies them!Sadly even kids are not spared from this!Hope the everyone learns to respect them in india rather than look at them as on object or thing!

>>'If there is a God, we must see him. And if there is a soul, we must perceive it.'

<comment><USER3> >>Faith, he wrote, must be based upon direct experience, not religious platitudes.

If one can objectively establish something by their own experience doesn't that just become a fact? Why do we need faith in the first place.

<comment><USER6> Not defending the particular point of view above.

But to me it looks like a lot of personal experience is just personal; it is subjective and it is hard to establish a particular experience as "fact" without widespread consensus. So faith might be necessary in the meantime.

</comment></comment></comment><comment><USER7> Vivekananda also lives on as an icon for the RSS and other extreme right wing Hindu groups.

Here for example is RSS leader Mohan Bhagwat speaking in front of a big Vivekananda picture:

[http://samvada.org/files/Independence-Day-Bangalore- Aug-15-2...](http://samvada.org/files/Independence-Day-Bangalore- Aug-15-2012-761.jpg)

Maybe they claim him wrongly? IDK.

<comment><USER8> All I would say is, do not let those scumbags distance you from reading about this guy. They have been trying to 'churchify' hinduism since ever and playing fast and loose with history and building this identity of "a racially and spiritually superior never-did-nothing-wrong majority that has been repeatedly wronged" that now needs to collect its dues and reclaim its prestige. It is striking how often that line works.

But yeah, expect downvotes because many people believe that crap. More true among Indians outside of India and in particular regions within, perhaps fuelled by the urge to connect with their roots. That is a perfectly legitimate emotion, just spoiled by the presence of these people who try to make some quick religio-political capital out of it.

</comment></comment><comment><USER9> Maharishi Ramana is someone who truly was a maharishi and attained atma gyan(enlightenment). [http://bhagavan-ramana.org/nanyar.html](http://bhagavan- ramana.org/nanyar.html) [http://www.sriramanamaharshi.org/wp- content/uploads/2012/12/...](http://www.sriramanamaharshi.org/wp- content/uploads/2012/12/Talks_Exract.pdf)

</comment><comment><USER10> this lecture [http://goo.gl/Fo1ZLJ](http://goo.gl/Fo1ZLJ) has a whole lot of detail about the influence of yoga in the west.

</comment><comment><USER11> The amount of nonsense which has been written about yoga (Vedanta and Buddhism) is, ironically, matches the amount of nonsense about OOP and Java.)

Yoga, at least according to the yoga sutra of Patanjali is *unity with the whole (That)", through unity of mind and body via breath as a preliminary practice, without which any further "realizations" are impossible (training routine).

Vedanta, which is rather mediocre "systematization" of Upanishads has been profoundly summarized by Ramakrishna - "Wanna see God? Look between two thoughts." (at the source/origin of thoughts). This is enough for realizing one's "true nature" (which is popular culture associated with a ray of light - pure energy).

The essence of Buddha's teaching is "life is shaped by our mind, we become what we think", which directly points to the mind as the ultimate source of all "suffering". (Problems doesn't exist outside one's head. Just physical processes).

There is also Rumi, who had the same realizations, but put them in different words.

The problem with all these fine and subtle teachings is, like Sartre pointed out, "the other people" with their stupid ambitions and flawed actions.

Instead of yoga we have gymnastics (in some cases even acrobatics) and whole industry of yoga pants and joints when they are sited for $30/h. Instead of Vedanta we have the same mysticism, where all the deities are morphed into the one. Instead of Buddhims - tons of narcissistic graphomany published by Snow Lion and the others.

So, no, so-called piece of mind comes not from yoga courses or a crowded retreat, but form realization of being an inseparable part of the whole, of That (or being in accordance with Tao, or "letting God/Love in", etc, etc.) It is in being "in balance" (in Eastern terms), non-contradicting with the whole.

I am guide for Himalaya and Tibet region for a few years now - and I could tell that all the magic and miracles, mantras, mandalas, sacred rituals or any form of shamanism "working" only in the realm of one's mind, and does not exist outside it.)

</comment><comment><USER12> spam!

</comment><comment><USER13> Not sure why this article is on Hacker News.

<comment><USER14> History is in scope here.</comment></comment>