Physics Discussion Thread

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Vivek Sreenivasan
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Physics Discussion Thread

Postby Vivek Sreenivasan » 13 Oct 2008 12:44

I think a new thread should be started similar to the 'mathmatics' thread that we had, to dicuss interesting topics in Physics. What do you guys think.

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Re: Physics Thread.

Postby Rahul M » 13 Oct 2008 12:47

since you are starting this thread you will be expected to contribute frequently and lead the discussions in a sense.
if you(or anybody else) are ready to do so, then fine, this thread can stay.
For the moment however I would let this one have a lifetime of two days. if it doesn't gather the required steam in that time, it will be locked and dumped.
regards.

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Re: Physics Thread.

Postby Vivek Sreenivasan » 13 Oct 2008 12:59

Okay id like by discussing the mysterious phenemenon of Quantum mechanics. One of the central questions in this field is weather light is a wave or particle. This is the orthodex interpretation

"Is 'is light a wave or a particle'? It really depends on how you set up the experiment. Now if you let the wave properties of light to show through ie in a double slit experiment guess what light is seen a a wave. Now it really gets strange here, If you have two slits in a board and you shine 1 photon at a time through one of the slits and allow multile photons to strike the counter at the other end, eventually a wave pattern builds up! Essentially the photon interfers with itself! Now if you try and observe which of the two slits the photon went through ie your forcing the photon to choose 1 slit over another the wave funtion collapses. Ie the very act of observation destroys the wave funtion and the photon is seen as a particle with no characteristic interfernce pattern!! So really the most you can say is that a photon has wave as well as particle properties"

Rather than the technical aspects im more interested in the philosophy of QM. I think that it indicates that there is no certainty in nature, everything is probabilistic. Dont get me wrong, there are somethings which are almost certain but no phenemenon has 100% certainity.

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Re: Physics Thread.

Postby Vivek Sreenivasan » 13 Oct 2008 13:02

Rahul M im interested in yourviewpoint regarding the philosophical implications of QM. Do you have such an opinion?

Entaglement is a phenemenon that is especially intersting, i dont think that even the best physicists understand this phenemnon completely.

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Re: Physics Thread.

Postby rsingh » 13 Oct 2008 19:06

Was at lecture by Professor Wolfgang KETTERLE,( 2001 Nobel Laureate in Physics, Massachusetts Institute of Technology, USA) yesterday. He explained his work. Cooling down gas to nano scale ( very near to absolute T) using lasers. That was fascinating stuff. You cool the gas so that it looses it Kinetic Energy and then at nano T you experience Bose-Einstein Condensation (BEC). Gas could shrinks to a ball that behaves as particles. Then you cut this by laser and you observe wave interference patterns. In other words you get new properties at super cool temperatures. He talked about super fluids and superconductors. For a non -Physics-type like me it was mind boggling. In the end somebody reminded that "if somebody claim to understand QM, he is overestimating himself". That was helpful for me to regain normal mullah-state -of- mind. Alas human are not dual in nature...........you can not claim to understand fiziks and be mullah at same time :)

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Re: Physics Thread.

Postby Rahul M » 13 Oct 2008 19:27

vivek why pick on me ? :eek:
truthfully, BR for me is a world away from physics and stuff and I want to keep it that way.
if you want to discuss fyziks, I would recommend the general discussion forum at
http://www.advancedphysics.org/forum

philosophical interpretation of QM is a very treacherous subject, even einstein got some of it wrong ! :shock:

rsingh ji, a trivia related to your post.
the condensate by Prof Unnikrishnan's group at TIFR is the largest in the world. (or at least used to be, sometime last year)

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Re: Physics Thread.

Postby sanjaykumar » 13 Oct 2008 22:27

Rather than the technical aspects im more interested in the philosophy of QM. I think that it indicates that there is no certainty in nature, everything is probabilistic. Dont get me wrong, there are somethings which are almost certain but no phenemenon has 100% certainity

Is this really so, or is it by convention ie the Copenhagen interpretation?

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Re: Physics Thread.

Postby Sanjay M » 13 Oct 2008 23:47

I like physics more than just pure mathematics, so I'll be interested in this thread, too.

advancedphysics.com is a good place for discussion, but there are others.

One of the best places is http://www.physicsforums.com

There are a lot of knowledgeable people on there. I post on there occasionally, too.
As a matter of fact, you may see posts on there which are exact copies of ones I've made here on BRF.

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Re: Physics Thread.

Postby Sanjay M » 14 Oct 2008 00:01

rsingh wrote:Was at lecture by Professor Wolfgang KETTERLE,( 2001 Nobel Laureate in Physics, Massachusetts Institute of Technology, USA) yesterday. He explained his work. Cooling down gas to nano scale ( very near to absolute T) using lasers. That was fascinating stuff. You cool the gas so that it looses it Kinetic Energy and then at nano T you experience Bose-Einstein Condensation (BEC). Gas could shrinks to a ball that behaves as particles. Then you cut this by laser and you observe wave interference patterns. In other words you get new properties at super cool temperatures. He talked about super fluids and superconductors. For a non -Physics-type like me it was mind boggling. In the end somebody reminded that "if somebody claim to understand QM, he is overestimating himself". That was helpful for me to regain normal mullah-state -of- mind. Alas human are not dual in nature...........you can not claim to understand fiziks and be mullah at same time :)


Yeah, I once emailed Dr Ketterle right after he won the Nobel Prize for making the BEC, and he was kind enough to reply back.

Well, the way I see it, is that the low-level "noise" from quantum perturbations is drowned out by the much more powerful effects of kinetic thermal vibrations. So if you strip out those thermal vibrations, you'll only be left with seeing the pure small-scale quantum perturbations. This is when you can see the BEC behavior of a gas, with its wave-like patterns.

It shows that beneath our thermal-kinetic masked world, there is a world of much more subtle perturbations/effects which are happening at the quantum level.

Andrei Sakharov, the Soviet Nobel Prize-winner, famously said that these "mysteries of the vacuum would be the great challenge of 21st century physics"

We need to somehow decipher what's behind those quantum vacuum perturbations. This will help us to master Space itself.

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Re: Physics Thread.

Postby RamaY » 14 Oct 2008 09:38

An excellent book for starters "The Dancing Wu Li Masters" by Gary Zukov....

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Re: Physics Thread.

Postby Philip » 21 Oct 2008 15:14

Warning from outer space and from the Mayan's too.

The Mayan civilisation in S.America is one of the most intriguing.With the tomb of priest-king Pacal,hidden in a pyramid discovered only in the last few decades,along with the de-coding of the Mayan calendar and its secrets,the message sent to our generation from this highly advanced civilisation is only recently being clearly understood.According to the Mayans,we are in 2012 going to complete their "long" solar cycle,which along with its associated heightened solar activity,always brings disaster to the earth.The recent climatic catastrophes-the Asian tsunami,hurricane Katrina,floods,earthquakes,melting ice caps and glaciers,etc.,indicate global warming on an unprecedented scale,that cannot be explained by mere activity of man-admittedly a contributing factor.The author Maurice Cottrell has written many books upon the subject and "2012" sites can be found on the Net.

A decade ago,"Helios",the solar telescope launched into space for solar study,gave us first time clues to the nature of the sun and its activity.The shape of invisible triangular magnetic rays moving outwards from the sun,that are depicted in ancient carvings and Mesopotamian hieroglyphoics were re-discovered.We now have a shocking warning from NASA about the depletion of the sun's "heliosphere",that protects the earth from its harmful rays.This will cause dramatic effects upon the earth as the folllowing report indicates.

http://www.telegraph.co.uk/news/worldne ... nking.html

Sun's protective 'bubble' is shrinking

The protective bubble around the sun that helps to shield the Earth from harmful interstellar radiation is shrinking and getting weaker, Nasa scientists have warned.

By Richard Gray, Science Correspondent
Last Updated: 9:23AM BST 19 Oct 2008

Data has shown that the sun's heliosphere is shrinking Photo: AP
New data has revealed that the heliosphere, the protective shield of energy that surrounds our solar system, has weakened by 25 per cent over the past decade and is now at it lowest level since the space race began 50 years ago.

Scientists are baffled at what could be causing the barrier to shrink in this way and are to launch mission to study the heliosphere.

The Interstellar Boundary Explorer, or IBEX, will be launched from an aircraft on Sunday on a Pegasus rocket into an orbit 150,000 miles above the Earth where it will "listen" for the shock wave that forms as our solar system meets the interstellar radiation.

Dr Nathan Schwadron, co-investigator on the IBEX mission at Boston University, said: "The interstellar medium, which is part of the galaxy as a whole, is actually quite a harsh environment. There is a very high energy galactic radiation that is dangerous to living things.

"Around 90 per cent of the galactic cosmic radiation is deflected by our heliosphere, so the boundary protects us from this harsh galactic environment."

The heliosphere is created by the solar wind, a combination of electrically charged particles and magnetic fields that emanate a more than a million miles an hour from the sun, meet the intergalactic gas that fills the gaps in space between solar systems.

At the boundary where they meet a shock wave is formed that deflects interstellar radiation around the solar system as it travels through the galaxy.

The scientists hope the IBEX mission will allow them to gain a better understanding of what happens at this boundary and help them predict what protection it will offer in the future.

Without the heliosphere the harmful intergalactic cosmic radiation would make life on Earth almost impossible by destroying DNA and making the climate uninhabitable.

Measurements made by the Ulysses deep space probe, which was launched in 1990 to orbit the sun, have shown that the pressure created inside the heliosphere by the solar wind has been decreasing.

Dr David McComas, principal investigator on the IBEX mission, said: "It is a fascinating interaction that our sun has with the galaxy surrounding us. This million mile an hour wind inflates this protective bubble that keeps us safe from intergalactic cosmic rays.

"With less pressure on the inside, the interaction at the boundaries becomes weaker and the heliosphere as a whole gets smaller."

If the heliosphere continues to weaken, scientists fear that the amount of cosmic radiation reaching the inner parts of our solar system, including Earth, will increase.

This could result in growing levels of disruption to electrical equipment, damage satellites and potentially even harm life on Earth.

But Dr McComas added that it was still unclear exactly what would happen if the heliosphere continued to weaken or what even what the timescale for changes in the heliosphere are.

He said: “There is no imminent danger, but it is hard to know what the future holds. Certainly if the solar wind pressure was to continue to go down and the heliosphere were to almost evaporate then we would be in this sea of galactic cosmic rays. That could have some large effects.

“It is likely that there are natural variations in solar wind pressure and over time it will either stabilise or start going back up.”

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Re: Physics Thread.

Postby Tanaji » 21 Oct 2008 15:47

RamaY wrote:An excellent book for starters "The Dancing Wu Li Masters" by Gary Zukov....


Seconded.

Of course the PhD types will turn up their noses at it since it doesnt have any "ekweshuuns" but is a great read as an introductory book.

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Re: Physics Thread.

Postby Vivek Sreenivasan » 22 Oct 2008 20:47

Thanks for those links Rahul M.

Im interested in discussing the nature of reality from an 'Indian' point of view. Indian perspective might be slightly different from western perspective.

I will raise an intersting question, what is the nature of time? Time is seen as being another dimension like the other three spatial dimensions. These four dimensions merge in Einsteins special relativity to become 'spacetime'.

This is important as thinking of time separately creates several difficulties. This 'spacetime' notion is absolutely brilliant. The notion of freedom also arises in this context. For example we can move foward and back, move up and down and side to side but with regards to the time dimension we can only move in one direction. Ie we cant go backwards in time. This is quite interesting.

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Re: Physics Thread.

Postby Rye » 22 Oct 2008 23:18

A good primer to physics with the correct level of mathematics are any works by George Gamow -- fun to read and educational. Mr. Tompkins series is great especially in explaining space/time, as is "Gravity", "Atomic Energy in Cosmic and Human Life" and "Biography of Physics". Any of his books are good for the lay physicist. (Most of these books are from the 40s and 50s but are brilliantly written and explained). "Physics: Foundations and Frontiers" is a must-read for any high-school physics-wannabe. There is no "Indian" and "Western" perspectives to science -- that's the nature of Physics and science in general.

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Re: Physics Thread.

Postby Rye » 23 Oct 2008 01:11

"Thirty Years that Shook Physics: The story of quantum theory" by George Gamow is also excellent for the lay reader with a science background. Explains how Quantum theory was developed over the decades and what experimental results drove the theoreticians of the time. All of his books read like a fun novel -- great style of writing.

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Re: Physics Thread.

Postby Arya Sumantra » 26 Oct 2008 15:29

For best conceptual understanding of Quantum Mechanics, there is very systematic and lucid book - Principles of Quantum Mechanics by Ramamurti Shankar. A lot of people vouch for it's approach and I bought it though i could not muster time out for it during my job. The book doesn't touch on philosophical side of QM though.

I had this childish analogy for coming to terms with wave and particle dual behaviour of electrons. It may be a bit immature but was sufficient to convince my mind. Suppose we knew only two states of matter: solid and gas and had to describe the behaviour of a liquid then like the solids it has a fixed volume and like the gases it could assume any shape(of confinement). An electron similarly is in a "third state" that shows interference like characteristics of waves and collisions and momentum transfer behaviour like particles.

On the spirituality front, I believe Kundalini state about which a lot of meditator's talk, to be resonance phenomena along the spinal chord comprising a standing wave between the topmost Sahasrara Chakra and bottom most Muladhara Chakra. All the intermediate 5 chakras in the body are the Nodes of this standing wave. Sadhaks achieve the Kundalini state in meditation when they are able to steady the travelling wave into a standing wave. Just my thoughts. The descriptions in Indian spirituality seem to converge a LOT with Wave physics

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Re: Physics Thread.

Postby Rye » 26 Oct 2008 18:03

Many islamic mullahs claim such things about the Quran "being very scientific" too....does not mean it is legitimate or right. Concepts in physics have specific domains of application -- it is usually wrong to pretend a concept that works in one area can be used in other areas unless there is experimental proof that such a correlation is warranted. Spirituality has nothing to do with Physics given what we know today, though clearly one can make a lot of money by writing a book pretending there is a connection.

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Re: Physics Thread.

Postby Arya Sumantra » 26 Oct 2008 20:52

Rye wrote:Many islamic mullahs claim such things about the Quran "being very scientific" too.

But what if it is the other way around i.e. the Physicist claims being a Vedantist ? Erwin Schrodinger who gave the Schrodinger Wave Equation was a well known vedantist. Here I reproduce his quote from International Berkeley Society forum(http://www.ursasoft.com/discus/messages ... 20010703am)

"In all the world, there is no kind of framework within which we can find consciousness in the plural; this is simply something we construct because of the spatio-temporal plurality of individuals, but it is a false construction. Because of it, all philosophy succumbs again and again to the hopeless conflict between the theoretically unavoidable acceptance of Berkeleian idealism and its complete uselessness for understanding the real world. The only solution to this conflict, in so far as any is available to us at all, lies in the ancient wisdom of the Upanishads."

The above was quoted from a thin volume by Schrodinger entitled My View of the World.

I, for my post am just expressing my delight at what I see as a convergence of spirituality and QM which others may disagree for want of any evidence.

Rye wrote:Spirituality has nothing to do with Physics given what we know today

Not so fast. If Science does not show a connection with spirituality then it does not comment about a disconnect either. Science is neutral about it and not taking either extremes. Besides Science is very adaptive. Once proven wrong it quickly adapts a new logic. Physics once claimed that Heat was an invisible fluid called Caloric which flowed from a hot body to colder body and changed its stance with Count Rumford's canon ball drilling experiments. Many Count Rumfords in future will disprove what is widely accepted today in Science.

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Re: Physics Thread.

Postby Rye » 26 Oct 2008 21:50

By spirituality, you seem to be talking about the paranormal and parapsychology kind of pseudo-sciences. There is nothing magical about coincidence, and the paranormal and pseudo-scientific "research" has been proven to be bogus many times over. CSICOP has been designing double blinded tests for that sort of thing for decades, and to date none of the results have been encouraging -- the Randi foundation has a 1 million $ prize avaliable for anyone who has theories connecting spirituality and physics...no winner of the prize yet for the past 10-15 years.

www.csicop.org

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Re: Physics Thread.

Postby Rahul M » 26 Oct 2008 22:18

Rye, I could be wrong but I don't think AS is talking about pseudo-science(paranormal behaviour and what not) at all.

if you ask me, vedanta is about the only religious philosophy that doesn't contradict modern science and in some cases provides eerily similar thought frameworks.

There is no "Indian" and "Western" perspectives to science -- that's the nature of Physics and science in general.

true in general but depends a little on how we define science or physics.

if we define science as "study and characterisation of nature" then of course there can be no Indian/western version of science.
in that I find terms like hindu mathematics/islamic science to be oxymorons.
add "christian science" monitor to that !

however, you can define science as the way of investigating nature.
that being said, the tradition of doing science and mathematics differed widely in the various civilizations especially ones that had little or no contact with outsiders.
as an example you will find that mathematical formulae were expressed in India as sutras unlike the notations used in the west.

now people may think that notation is trivial but it is decidedly not.
a radically different notation necessarily requires and demonstrates a completely different way of thinking.

the ancient Indians (and the chinese too AFAIK) therefore represented completely different ways of doing science that are now completely lost to us with little chance of a revival.
it could be that those ways of thinking would have left the western way of doing science in the dust if they continued or it could be that they would have met dead ends.
we won't know either way.
for better or for worse now it is only the western way of doing science that is left to us.

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Re: Physics Thread.

Postby Rye » 27 Oct 2008 00:06

Rahul M. wrote:
if we define science as "study and characterisation of nature" then of course there can be no Indian/western version of science.
in that I find terms like hindu mathematics/islamic science to be oxymorons. add "christian science" monitor to that !


Rahul,
That is my point too. However, it does not mean that the current method of scientific inquiry cannot be improved on. Also, I am not sure that there is anything "western" about current scientific methodology, it is the best we can do given a rather large area of ignorance/mystery for us -- the working of the human brain.

The problem is that experiments must be conducted using a tool that is extremely falliable -- the human brain. The human brain unconsciously jumps to conclusions that can skew the results of an experiment, which is the motivation for the "double-blind" method.

For example, it is very clear that homeopathy works because I have seen it work, and yet "western science" sneers at homeopathy because they cannot prove that homeopathy works by a double-blind method. The suspicion is that the "placebo effect" almost completely, but then maybe that is not completely true either -- the placebo-effect combined with the low concentration of the "cure" may just kickstart the body to produce the require chemical or its substitute. But then, without knowing how the mind works, one of the important parts of this equation, the reaction of the mind to not just the chemical itself, but the thought that "a cure is imminent" maybe responsible for people feeling better. This seems to especially work well with psycho-somatic illnesses rather than real diseases. But there is no real "scientific technique" to evaluate cures for psycho-somatic illnesses, which is probably why the tarot card reader seems to do as good a job as an astrologer, and science cannot come up with solutions that can substitute for the above kind of unscientific methods in many cases when it comes to real people.

however, you can define science as the way of investigating nature.
that being said, the tradition of doing science and mathematics differed widely in the various civilizations especially ones that had little or no contact with outsiders. as an example you will find that mathematical formulae were expressed in India as sutras unlike the notations used in the west.


Notation has to be separated from the theory itself usually, the core results can be expressed in different equivalent notations -- after all "notation" is a mental invention to formalize a certain way of thinking.

For example, if narco-analysis becomes a hard science (hypothetically speaking), maybe patients can just be hooked up to instruments and then their mind can be read to differentiate if they are being influenced by external factors. It would be difficult to improve on the current scientific method, without involving detailed knowledge of the brain itself, if such a thing is possible.

now people may think that notation is trivial but it is decidedly not.
a radically different notation necessarily requires and demonstrates a completely different way of thinking.


The flip side is that notation that is not concise usually limits thinking -- the notation that usually survives over time is the most intuitive one, and even that changes when newer discoveries leave older notation insufficient, so it is an evolutionary process.

the ancient Indians (and the chinese too AFAIK) therefore represented completely different ways of doing science that are now completely lost to us with little chance of a revival.
it could be that those ways of thinking would have left the western way of doing science in the dust if they continued or it could be that they would have met dead ends we won't know either way.


That's not necessarily true because the human mind can fool itself into misunderstand reality, so the designer, observer, and result analyzer are all made independent to reduce the chance for false positives, i.e., concluding there is a scientific basis for believing something, when there isn't. Even there, if the people conducting the experiment are measuring the wrong variables, the result will mostly be gibberish (at worst) or inconclusive (at best).

JMT

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Re: Physics Thread.

Postby Vivek Sreenivasan » 27 Oct 2008 16:01

The concept that there is no 'Eastern or Western' perspective on science in my opinion is misguided. Sure theories need to be backed up by facts to be legitimate but tell me how do you develop the THEORIES themselves?

Science is a lot more intuitive than many people realize, its not just about boring numbers and conducting experiments over and over again. Even Eisntein stated that "imagination is more important than knowledge". Bascially coming up with an idea requires inspiration and ideas can be different from different cultures.

For example it is widely purported that an unknown Indian genius in the past came up the with concept of 'zero', before this all number systems started off at 1, zero now is this basis of wide branches of mathematics and science, calculus and differential equations depend on it and so do physics. Can you imagine the inspiration for this breakthrough?

As another example, Einstein came up with the theory of relativity which radically changed our world view. This was an inspiration that he had and later proved. The ability to come up with these ideas themselves can be different according to different cultures. Therefore when i speak of physics from an 'Indian perspective', im interested in physics ideas about mysterious concepts like space, time, consciousness, etc from an indian perspective which can be different from western perspectives but still needs to be inline with the scientific process. Im not interested in some widely fantasic imaginations like astrology and rebirth, they are not scientific theories imo.

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Re: Physics Thread.

Postby Rye » 27 Oct 2008 20:50

Vivek Sreenivasan wrote:
The concept that there is no 'Eastern or Western' perspective on science in my opinion is misguided. Sure theories need to be backed up by facts to be legitimate but tell me how do you develop the THEORIES themselves?


The direction of development of theories comes from astute observations on the nature of reality. The order is 1) observe 2) hypothesize 3) verify The first two require creativity and the third requires honesty and objectivity.

Science is a lot more intuitive than many people realize, its not just about boring numbers and conducting experiments over and over again.


intuition alone gets you nowhere, if you cannot explain the intuition in terms of real terms. Also, it is not all intuition, sometimes the important intuitions only come because of anomalies/discrepancies in the experimental results, which leads to confirmation that the current theory may have holes in it.


Even Eisntein stated that "imagination is more important than knowledge". Bascially coming up with an idea requires inspiration and ideas can be different from different cultures.


That does not mean that the imagination is of any use without the knowledge. Einstein was completely aware of the cutting edge of Physics in his time when he came up with his theories of relativity -- he was completely knowledgable in his domain. The creativity that comes after acquiring all that knowledge is more important and useful. Else it would be reinventing some wheel that was already invented eons ago.

As another example, Einstein came up with the theory of relativity which radically changed our world view. This was an inspiration that he had and later proved.


that is not quite how it happened -- Morley-mitchelson and others did experiments that proved that the speed of light is a constant in all directions. Einstein's own theories are based on this fact -- any of the books by Gamow will show you that the ideas did not arise out of a vaccum but arose from existing popular results back in the day when Physics was considered "cool".


The ability to come up with these ideas themselves can be different according to different cultures. Therefore when i speak of physics from an 'Indian perspective', im interested in physics ideas about mysterious concepts like space, time, consciousness, etc from an indian perspective which can be different from western perspectives but still needs to be inline with the scientific process.


The typical order of inventing new theories and ideas is (a) understand current works (b) critique current works to see if they stand up to scrutiny -- if not, pick up loose threads and see if the sweater unravels (c) if the current ideas are sound, then determine the unanswered questions in the field at the time and find out what are the conceptual difficulties that stop development of a field in specific directions.

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Re: Physics Thread.

Postby jamwal » 29 Oct 2008 10:58

Is there any good source for String Theory? By good, I mean easy for a layman like me. Has there been any progress lately?

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Re: Physics Thread.

Postby jobatra » 30 Oct 2008 08:15

jamwal wrote:Is there any good source for String Theory? By good, I mean easy for a layman like me. Has there been any progress lately?
jamwal wrote:Is there any good source for String Theory? By good, I mean easy for a layman like me. Has there been any progress lately?


zweibach's "first course in string theory" is the only novice textbook. you are still expected to know most of your undergrad quantum/e&m/wave mechanics etc.

based on the string theory for undergrads course at mit

Re: Shankar's Quantum Mechanics. Yes, it's a good book but definitely not enough on it's own. There are almost NO pictures, which really bothered me. Chapter 12 is a joy (Angular momentum and symmetries). best treatment of angular momentum anywhere i have seen.

I would recommend a combination of griffiths/shankar at the entry level. if you want one book that covers everything -- look no further than cohen-tannoudji.

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Re: Physics Thread.

Postby ramana » 30 Oct 2008 23:56

So Jo, What are you upto nowadays? Havent seen you in quite few years! Are you inot your doctrate?

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Re: Physics Thread.

Postby Arya Sumantra » 31 Oct 2008 08:12

Vivek Sreenivasan wrote:when i speak of physics from an 'Indian perspective', im interested in physics ideas about mysterious concepts like space, time, consciousness, etc from an indian perspective which can be different from western perspectives but still needs to be inline with the scientific process.


Might want to take a look at this:

Om pUrNamadah pUrNamidam
pUrNAt pUrNamudachyate
pUrNasya pUrNamAdAya
pUrNamevAvashiShyate
Om shAntih, shAntih, shAntihi (Isavasya Upanishad)

Translation:
Completeness is that, completeness is this,
from completeness, completeness comes forth.
Completeness from completeness taken away,
completeness to completeness added,
completeness alone remains.
Peace, peace, peace!

Mathematical equivalent of what this verse describes is Zero though it describes complteness, Infinity

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Re: Physics Thread.

Postby Rye » 01 Nov 2008 01:19

The multiplicative inverse of zero is basically infinity, i.e., X/zero is "not defined" but if you use the notion of limits then that tends to infinity. If there is an "Indian way" of looking at science, it can be with the synthesis of existing fields in ways people have not thought about yet.

JMT

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Re: Physics Thread.

Postby Pulikeshi » 01 Nov 2008 09:45

Cool thread!

Have you guys looked at - Steve Wolfram's A New Kind of Science

Also, Charles Seife's Decoding the Universe: How the New Science of Information Is Explaining Everything in the Cosmos, from Our Brains to Black Holes

I found the latter to be a very interesting book with implications for how we view the universe - there are still some fundamental issues not answered by Quantum Mechanics or even String Theory for that matter. As the latter is more mathematical and not something that traditional experimental Physicists have had a case to get their hands dirty on.
Information Theoretical perspective may be interesting way to reconcile some of these issues.

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Re: Physics Thread.

Postby Rye » 01 Nov 2008 21:44


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Re: Physics Thread.

Postby Rahul M » 01 Nov 2008 22:34

that is not quite how it happened -- Morley-mitchelson and others did experiments that proved that the speed of light is a constant in all directions. Einstein's own theories are based on this fact -- any of the books by Gamow will show you that the ideas did not arise out of a vaccum but arose from existing popular results back in the day when Physics was considered "cool".

einstein actually said he didn't know of MM experiment at the time and the subsequent theory of GTR was certainly not based upon any experimental observation.

what you are describing is by and large called phenomenology. in proposition of a theory it's mostly a talented guy and his intuitions about nature -- the so-called stroke of genius !

of course that intuition takes hard work to develop to a point when the aspects of nature you are working with becomes second nature, it's not all born with.

an interesting comment may make this clearer :
Paul Olum suspected that when Feynman wanted to know what an electron would do under given circumstances, he merely asked himself, "If I were an electron, what would I do?"

:D

http://query.nytimes.com/gst/fullpage.h ... wanted=all

btw, the I seriously recommend the book this appeared in, "Genius : The Life and Science of Richard Feynman" By James Gleick, the guy who wrote chaos.

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Re: Physics Thread.

Postby Rye » 01 Nov 2008 23:58

Rahul, I agree w.r.t. Gleick's book. You are right. I think Eintein may have just needed the assumption that there was a limit to the speed of light "c" to work out his theories. MM was to determine the actual speed of light, so I should not have mentioned it in my post.

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Re: Physics Thread.

Postby Pulikeshi » 02 Nov 2008 00:55

Of course speed of light varying with time and the resulting cosmogony has also been described as well - some aspects of all this remains controversial (as in religious debates)

Check Paul Davis - Quantum Aspects of Life

A must pick - What is life? by Schrödinger to understand what inspired Crick to search for "crystalized" information (genetic material) in living systems.

His discourse on 'order-from-disorder', 'order-from-order' and determinism and free will are brilliant for any one with Vedantic background to understand.

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Re: Physics Thread.

Postby Rye » 02 Nov 2008 03:53

I thought speed of light was only affected by the medium of transmission...it is time that slows down in the frame of reference of a body as it approaches the speed of light.

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Re: Physics Thread.

Postby Vivek Sreenivasan » 02 Nov 2008 08:43

The CERN reactor in Europe is going to conduct some pretty fundamental experiments into the nature of reality. They are looking for the so called 'Higgs Boson' (Boson is actually named after an Indian). This particle is supposed to provide all other particles with mass. It will be interesting if they find it. If they dont, its back to the writing books wrt the Standard Model. But the experiment has been set back several months after some accident occurred. This experiment is so powerful that mini-black holes are going to be created!

On the question of light, the picture is actually very nuanced. Light seems so simple a concept it actually is pretty complex. Light can be seen as alternating electic and magnetic fields. I also read that light has no energy itself, ie if its still (can a light particle be still?) it has no energy and that all its energy is derived from its movement. But another interpretation holds that light behaves like a particle.

Bascially modern science has been reduced to talking about the 'behaviour' of light under certain circumstances. Depending on how you construct a experiment light can behave like a particle or a wave. That seems to be most we can say about the nature of light atm.

Such an apparently simple concept as light is actually very nuanced. I think this has implications on how we view reality itself. Simple things on the surface can have very deep undercurrents.

Rye in a vacuum the speed of light is a constant. What is weird is that even if your travelling at 99% the speed of light and shine a torch the light 'particles' travel away from you as though you were still!. In this case yes time and space get warped. It seems that in a vacuum light will always move away from you at a constant 3X10^8M/sec sec regardless of what you do. If you try to catch up with the light particle, nature will conspire to ensure you dont, not even to 0.0001%.

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Re: Physics Thread.

Postby Pulikeshi » 02 Nov 2008 09:14

Rye wrote:I thought speed of light was only affected by the medium of transmission...it is time that slows down in the frame of reference of a body as it approaches the speed of light.


Correct, but there are other theories that speed of light was faster during the early universe and has since slowed down -

Variable Speed of Light

See the section on 'Varying c in time" and onwards, the work of Petit and Moffat in particular -
Also the paper of Casado Gimenez:

A SIMPLE COSMOLOGICAL MODEL WITH DECREASING LIGHT SPEED
(The math is simple enough for anyone with a decent physics/math background to understand.)

That said, these theories are just that, and remain controversial. Which you know I like! :mrgreen:

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Re: Physics Thread.

Postby jobatra » 05 Nov 2008 21:43

ramana wrote:So Jo, What are you upto nowadays? Havent seen you in quite few years! Are you inot your doctrate?


ramana! so surprised you remember...

yes, doing my phd somewhere where it snows in october...definitely not bay area :)

how have you been?

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Re: Physics Thread.

Postby ramana » 11 Nov 2008 10:27

Pretty good. Convey regards to your dad. My son is now a in law school.

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Re: Physics Thread.

Postby Amber G. » 09 Dec 2008 02:46

FWIW -

For those who want to get intro to QM, one of the best, IMO, are Feynman lectures (3 volume). They are fairly readable (will require college level math). There is also extracts from these "Seven Easy Pieces" ( I have seen these in book stores with audio of lectures - very much fun to hear) which deals with these subjects with less math - and IMO excellent for non-physicists.

(I have had a chance to be in lectures given by Feynman, and think he is the best teacher I have ever had)

Also as mentioned before, Popular books by George Gamov are really good, One which I liked very much was "One Two Three, Infinity" . (I spent quite a few summers at Boulder (they had a nice summer program, popular among grad students at that time) and they had many selves of his books (These books were were so popular that they were translated into many languages) So you can get a copy in Hindi or Marathi etc... :)
One two three Infinity surveys math, physics (including QM, relativity), chemisty, biology etc. Tomkins (there is a paper back version which combines a few (Tomkins in wonerland, Tomkins Explore the atom etc) of the earlier books alos there are updated versions now - some additions after GG's death to bring it up to date) deals with Relativity, Atomic Physics, cosmology, high-energy physics, thermodynamics ... fun book to read.

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Re: Physics Thread.

Postby Amber G. » 16 Dec 2008 03:36

Okay, just for fun, 4 random, old classic problems (They are well known, but may still be fun) - comments welcome though put them in "tiny print" so as not to spoil others fun. (Some problems are easy - some are not that easy :)


P1 - What will happen if all the north polar ice (floating) is melted. (Assume we are considering NO land ice - from Greenland or Antarctica etc .-- ONLY the icebergs) Will sea water rise, fall or remain the same?

P2 - In your garage you have a pendulum about 2 meter long with about a 5kg weight below and it is not moving. There is glass about 20 cm away from the weight. All you are allowed to use is a drinking straw. (You can sip a drink with the straw or blow air through it etc) Can you make the pendulum swing so that it hits the glass. (You can not touch the weight, or touch the weight with the straw - or move the glass closer etc)

Note: It's an open-ended problem but is not a "trick" problem (Nice problem to do in practice). (Problem is from Duke Physics Dept's challenge problem )

P3 - Consider an ordinary lawn sprinkler, it is an "S" shaped curve and when water flows out, it spins. It is easy to guess which direction it will spin (opposite direction of the water when it comes out of the nozzle) Imagine if the sprinkler is dipped inside a swimming pool. (If you still push water, and force it to come out of nozzle, obviously it will still spin in the same way as if it was in the air). What happens if you suck water (that is water from the pool is going in the nozzles and is being sucked from the center) - which direction the sprinkler will spin?

P4 - In a (very small) lake, a person sitting in a boat, throws some scrap metal (made of iron - which was originally inside the boat) from boat into the water. Will lake water rise/fall ?


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