To Go Beyond Yesterday

The Blog Physica Page on Condensed matter books is up. It is a page under construction and a lot more work has to be done. For example, as of now, it is egregiously weak on soft condensed matter books, books on semiconductor physics. So, dear reader, if you think you can help us in that regard, please do so.

Sometime ago, I came across the site by Arvind gupta at IUCAA Children’s Science Centre. For those who haven’t heard of him before, he is the 1988 winner of the National Award for Science Popularisation amongst Children, conferred by the Department
of Science & Technology, Government of India. And a recipient of Distinguished Almunus Award 2000 from the IITK “In recognition of his outstanding and seminal contributions in developing low-cost science-base teaching aids for young children and thus doing a great service to humanity at large”. (or you could just watch him in action at youtube right at the end of this post).

The site http://www.arvindguptatoys.com has a great collection of material regarding popular science and education in general. I particularly liked the comic titled the story of physics with a slightly humorous slant. You should check it out sometime, you might like it too. It is a children’s history of physics[1] with pages like the one below

Or, if you think you have already outgrown comics, you might like articles like this one - “In Search for the Meaning of Science” by A.K.Roy . There are many articles like the one by Roy which take a hard look into what science means for Indian society - deep reading, indeed.

And as promised, here is the youtube video of a “talk” by Arvind Gupta.

Arvind Gupta - Toys from Everyday Stuff

This video was shot at MAIS, Bangalore when tinkerer and toy-maker, Arvind Gupta (winner of the National Award for Science Popularisation) worked with kids of Std. 06 and showed them how to make some exciting inventions from ordinary stuff like straws, film roll cannisters, empty toothpaste tubes and string!

[1] By children’s history, I mean a kind of a kind of history which is consciously oversimplified (for example, by opting deliberately for a whiggish tone) so that it is accessible to children.

The Documentary on Rabindranath Tagore by Satyajit Ray - thanks to those who uploaded it on the YouTube !

Sometime ago, Arunn, a professor from IITM put up a post in his blog complaining about the lack of enthusiasm for science blogging in India. I have nothing much to add to what he has already said.

However, something is painfully clear - I, among the few Indians blogging on Science, haven’t done enough to make the situation better. And hence, the title of this post.

I very much sympathize with Arunn’s frustration - I am no stranger to that feeling. Last year, when I was still an undergraduate, I had along with some other undergraduate colleagues of mine started a blog named blogphysica . From whatever experience I have gained from that exercise, I can safely say that it is almost equally difficult to convince students about blogging science.

And that is just a restatement of what has already been said . A more pertinent question is of course, what can be done about it ? That, I realize is a difficult question - and it should be answered in the way all such difficult questions are answered : Formulate solutions, Attempt to implement them, Note the obstacles that arise, Go back to the drawing board armed with that knowledge and Repeat till you succeed.

This is a game in establishing a vibrant Indian SciBlogsphere and we are not going to win it in a day. It is very tempting for us to get annoyed when say, Scian Melt gets disbanded or when Panta Rei gets very few entries , but, I think we will win this game in the end .

Do I have anything more concrete to say than that broadly optimistic assertion ? Yes, indeed. Among the links to the left, you will find a list of links listed under the title “India/Science”. That list, captures in a way all that I know about Indian SciBlogging.

In particular, let me draw your attention to some blogs whose names have never been raised in this discussion before [1]. Indian Science News and Popular Science Writing - both maintained by a journalist named Y.Bala Murali Krishna. If we dig a little bit, we come across the “about us” posts tucked among the early posts in the blog [2].

So, we are told

Welcome to this “Popular Science Writing” blog aimed at promoting popular science writing for the young and the old and even the scientists,besides inculcating scientific temper.Any articles on this aspect are most welcome. …

I am bureau chief-cum-special correspondent of the United News of India(UNI) now working in Panaji-Goa specialising in science and technology, media and related issues besides photography. I have also been a journalism educator and resource person to the National Council for Science and Technology Communication(NCSTC) under the Union Ministry of Science and Technology….

I have been engaged in participating in various science writing workshops across the country as a resource person besides various annual National Science Communication Congress sessions.Our aim is to prepare a dedicated band of people including the scientists, particularly the youth,who could write for different media organisations exposing the potential of the Indian Science and Scientists to the common man.The process involves application of various journalistic forms of writing, known as genres and avoiding jargon.

and the second blog welcomes us with the post

Hi friends,

This blog is to bring out some of the best science stories contributed from journalists,particularly of the United News of India, across the length and the bredth of India to benefit the readers.

It is aimed at encouraging popular science writing by post graduate students,scientists and journalists.

So, my question is this - How many other science writers are out there , who will be both eminently capable and very much interested in advancing the cause of Ind-Sci-Blogging ? And how is it that such kind of science writers are rare in Indian blogsphere despite the fact that we have whole institutions devoted to science communication ?

Note :

[1] To be fair to Arunn, he has already made it clear that his interest in this particular post is to understand “why “scientists” (or say, Ph. Ds. who have an expertise) in India seems not to have picked blogging yet as a means for communication.” And the blog I am now referring to, does not fall under that category.

[2] Those familiar with blogsphere would probably remark that it is not a very good blogging practice to bury the “About us” page among the early posts.

A peripheral glance at this blog should convince the reader that I enjoy reading more than writing. I write very sporadically (I do realise how cruel it is to the blog-readers ..). But, those who frequent here often will hopefully realise a kind of “silent blogging” happening as I update my links to the left.

For example, I’ve created new lists as new Maths blogs came along and my lists were updated when geology/chemistry blogsphere grew to its present size. I call this “silent blogging” for a very good reason. One, I am trying via these links to attract the attention of my readers to these blogs which is very similar to what a lot of posts in blogsphere end up doing. Secondly, the list of links to the left is my way of conveying my tastes - to tell those who visit this blog what sort of stuff I find interesting. In that sense, this list is a form of self-commentary, a way of communicating my perspectives.

A substantial part of what people are is what they find interesting. On that vein, I’ve included a link to my Google Reader(Shared Items) page (Feed URL) . It’s mostly a list of posts from all over the physics blogsphere. Occasionally, you might find a non-physics post, but, I will try to stick to physics posts for now.

As a compensation, here is a list of non-physics links which I found interesting.

1) Here are some great photos of the institute from which I got my undergraduate degree. It shows a lot of buildings as they were under construction. To my colleagues from there who are reading this, how many of these venues can you identify ?

2) Via one of my schoolmates, I came to know of this blog by Kalyan Verma. He seems to be a great lover of wildlife photography and has some interesting photos up on his blog.

3) Terence tao has an interesting post about the Navier Stokes equation - Why Global Regularity for Navier Stoke is Hard ? (By the way, I should probably sit down and write a post on whatever little I’ve learnt about Ricci flow and Perelman’s proof on Poincare’s conjecture - but, unfortunately, it is a bit too much effort to put together all my notes…)

4) See also his post about mathematical education - there is an interesting discussion in the comment section about math-literacy and its significance in the present world.

5) Recently, a lot has been written about the E8 story. Rather than flex my fragile representation-theoretic muscle, I will ask the readers to read an exposition by John Baez .

6) Also read the recent “This week’s finds in Mathematical Physics” dealing with quasicrystalline tiling and Islamic architecture apart from E8.

7) Carl Zimmer has an interesting post titled Said the Mouse to the Other Mouse, “Dude, You Would Not Believe The Colors I’m Seeing….” based on this paper in Nature. By changing a gene, biologists have made Mouse see colours that it normally cannot see ! Though Zimmer quiet doesn’t come around to talking about it, I was reminded of Ramachandran’s discussion (on what is known as “Qualia” in philosophy) in his book “Phantoms in the Brain”.

8 ) Talking of Ramachandran, if you haven’t read/heard it already you should definitely have a look at Reith lectures by Vilayanur S.Ramachandran titled “The Emerging Mind”.

P.S. : Recently, I was tagged by the “Entertaining Research” Blog asking me to link this post by the “Effect measure” blog in which they have resolved to explain a technical paper on “a mathematical model to investigate the spread of antiviral resistance in the control of pandemic influenza”. In their own words

Why consider this an “experiment”? The experiment was to see if a paper that used a coupled system of non-linear ordinary differential equations as its main technical tool could be explained sufficiently so a lay audience could understand what was involved and how the model worked. In that way they would have a better appreciation for the findings and some understanding of an important tool, mathematical modeling. We took it as a personal challenge…

As somebody who can almost never sit down to patiently explain in writing the interesting things in science, I have nothing but great admiration for this effort spanning some sixteen posts on a single paper !

Subhojoy wrote an interesting comment to my previous post. You can of course read the entire comment and the ensuing discussion. But, for the benefit of readers, I just wanted to pull out some interesting things that came up - especially the latest comment of mine. I will just provide some context and reproduce that comment.

He pointed out that

.. science - universal and unifying as it may be - is also very much a *human* pursuit.

to which I essentially agreed with some qualifications :

as you say, there is something quiet engaging about science - a mature passion that is a mix of child-like curiosity, a detective’s diligence, a kind of exalted honesty not to fool oneself[1] , a deep humility [2] combined with a conviction to stand for a scientific fact come what may.

to which he replied

Well if one has the analogy of a ‘child’ in mind, I wouldn’t stress too much on the ‘exalted honesty’ and ‘deep humility’ part of it … Also, I think the ’scientific method’ is there precisely to exploit human intuition, and other human cognitive biases.

And here is the reply I wrote :

..I wouldn’t stress too much on the ‘exalted honesty’ and ‘deep humility’ part of it..

I think it is a question of what you choose to emphasise.

Sometimes in science, the boundary defining “being honest with oneself” is so clear-cut, so obvious that one should be crazy to cross that Rubicon. What would you think, say, of a person who denies a proven theorem in mathematics and actually believes that theorem to be false with his whole heart ?[1] Such people are indeed rare [2] and their self-delusions are obvious enough to their colleagues.

But, more often, it takes a lot of effort to protect oneself from self-delusion. Mathematician to a large extent and physicists to some extent do not need to put in so much effort - but, we should not underestimate how our natural cognitive biases can hamper our understanding of say evolutionary biology, anthropology or Cognitive Neuroscience. It often takes some effort to not let in our prejudices(both innate and acquired from our culture[3]) seep into our analysis.

Having said that, the misleading notion of a dispassionate scientist wearing lab-coat staring into nature “scientifically”[4] should be thoroughly debunked - there is no great scientist I know of who did not have deep feelings about their subject. Or more importantly, both rational and emotional thinking arise out of a single nervous system - to assume a priori that reason and emotion inhabit two different worlds is not an easy hypothesis to justify.[5]

This brings us to what you later write :

..I think the ’scientific method’ is there precisely to exploit human intuition, and other human cognitive biases.And as for ‘human’, I really mean these human ‘qualities’, like our curiousity or our bias towards seeing patterns.

I will agree that Science is deeply human in the way it involves some of our cognitive biases. But, the keyword is “some”. A bias towards seeing patterns might be a great gift but it is known how it hampers our understanding of probability and the notion of randomness - we tend to “see” patterns even when they are really not there ![6] Quantum mechanics is not very intuitive, which is unsurprising given that our brain evolved in a mostly classical world. So, science picks and chooses among our biases, sublimates some of them into deep understanding while cautioning us to be careful about some others.The scientific method could not have been formulated by those who didn’t have at least a preliminary understanding of human biases. In my opinion, a scientific understanding of human irrationality is absolutely necessary for better understanding of what constitutes scientific method.[7]

And I liked the quote by Grothendeick.

“Only innocence can surmount them, which mere knowledge doesn’t even take into account, in those moments when we find ourselves able to listen to things, totally and intensely absorbed in child’s play.” Grothendieck

I will just add that among the noblest influences that science has on its practitioners is to deepen that innocence. It takes quite a lot of wisdom to be child-like.

[1] I have chosen an example in mathematics . Similar examples in Natural Sciences do exist but are slightly more trickier to find/formulate.

[2] The main reason for they being rare is this - Most people (are simply ignorant of) / (do not care about) deep theorems in mathematics to express their opinions one way or another.

[3] I suspect “innate vs acquired” distinction might itself be an almost universal cognitive bias. That suspicion of mine , if you are interested, comes from my inability to formulate a natural way of defining that distinction.

[4] Sometimes one hears people sincerely believing that to do something “scientifically” is to take a thing, break it into pieces, get rid of all the “beauty” in the stuff, put it into a mental centrifuge, take the useful thing and dump the rest ! To be fair, quite some “scientists” go about doing their work this way - but, to do science this way is, in my opinion, is to descend into mediocrity. Scientific diligence is not mere mechanized execution. To do something scientifically is not so much about breaking stuff as much as it is about the wisdom to know when/how to break and when not to.

[5] Given that art,culture,science and religion(of both superstitious and deeply philosophical kind) arise out of a single system, the onus is on those who believe in great walls dividing these human endeavours, to justify their belief.

[6] The pseudo science of Astrology, for example, sustains itself mainly because of our “ability” to see connections between things which are unconnected. In fact, the wikipedia list of cognitive biases reads like one long answer to the question - “Why pseudo-science is so popular ?”

[7] I consider scientific method to be (at least partly) a scientific theory like quantum mechanics or evolutionary biology and that explains why our understanding of it is definitely incomplete.The successes of science definitely show that we have got a very good approximation to the theory of scientific method and scientists in most cases seem to have a very good gut feeling for what is scientific. But, it would definitely help to understand this gut feeling better. Many do not realise that “what is science ?” is as much a scientific question as it is a question in philosophy.

Name anything on earth or in the sky far beyond. Think of anything that you can think of. I can bet that Science has something interesting to say about it.

Except Science, there is nothing that humans have ever done , no goal that they have ever pursued that goes beyond our self-centric nature, our ever-present temptation to irrationally hold one species to be more important than all others and one planet to be the centre of everything.

Science is the universal language - when you learn how our heart works, you learn about hearts of so many other cousins of our species. When you understand the colours flowing out of a vapour lamp, you understand the language of the same gases staring at you from the stars far away. When you can decipher that small piece of magnet lying around, you understand the history of our planet etched in the magnetic domains of the Atlantic sea floor.

All that you see with your naked eye speaks electromagnetism - brandishing proudly their charged swords, writing psychedelic hues on the vacuum slate. Their masses come mostly from the ever-boiling strong interaction fields that pop in and out of nowhere like little kids. A silent swarm of neutrinos run through your body in a breeze more gentle than any that you’ve felt.

The deepest of your emotions is a symphony of atoms - the most mellisonant tune you’ve heard is their passionate dance in your eardrum.

Gold gets its golden hue from its electrons speaking relativity. The plain crystal of salt mumbles incessantly of solid state. The glorious sun hums as its plasma whirls around its magnetic roads.

To those who can hear, it is a concert with science as the ticket. For those who cannot, deep are my condolences.

And stronger still shall be my condemnation of all that deprives one of this most glorious of feelings - poverty of the body and soul, the hunger, human cruelty and indifference, mindless wars, boundless arrogance, shameless plunder and surrender to superstition. India celebrates Science Day today - and science means much more than most of its citizens assume…

• WordPress.com introduces . It is a big deal for a blog like this, since, it allows me to write equations “on the fly” . It works even in comments ! Just use the syntax $latex <LaTeX Eqn.>$

  For example, try this - $latex E= \sqrt{p^2c^2+m^2c^4}$ gives . Of course, the downside is that in rare cases, tempts you into using more math even when it is not strictly necessary.

• You would notice that I’ve put up a new page - The Scientific India . I realised that it is not possible for me to put the various science-in-India-related sites in my blogroll. Hence, I’ve created a separate page for those links.
• Talking about blogroll, I’ve added many new geology/math/many other blogs to the list. You will notice that I’ven’t created a separate list for Computer science - for now, I’ve decided to club it together with math, I’ll try to make a separate list later…[1]

Update (27/2) : I’ve added some more blogs. Check out this post titled “Quantum mechanics and Tomb Raider” by Terence Tao.

• Via n-category Cafe, I came across an article titled “What is good mathematics?” by Terence Tao. The second half of the article is on something called as Szemeredi’s theorem about which I know almost nothing [2]. But, I found the discussion in the first half quite interesting.

Endnotes :
1. Have a look at the inaugural edition of the carnival of mathematics . It has links to a lot of interesting posts including a post on algebraic topology titled “ for layman”.
2. These posts seem to be a good place to start if and when I want to learn what it is all about - I don’t see it happening any time in the near future, though.

Few days ago, I tried to answer the question - What is a frame ? As we saw, it is not a very difficult concept. But, let me just add something I forgot to mention the previous time. (Actually, I’m worrying about some other problem today - so it’ll be a short post.)

A frame is different from a co-ordinate system. I can’t repeat it enough, so I will say it again - A frame is different from a co-ordinate system.

The confusion between a frame and a co-ordinate system is unfortunately quite common among physicists[1]. A frame, as I have already explained, is basically a convention which decides ad hoc - what is “North”, what is “East”, What is “up” and what kind of “waiting” is a standard at each place and for all times.

A co-ordinate system, in contrast, is a set of numbers[2] given to each place at a particular time. For example, I can say give a set of numbers (1,2,3,4) to the place I was born as it was in the time I was born. Or give a set of numbers (5,6,8,0) to the place I was sitting in as it was when I was typing the previous full-stop. And if I can give such a set of numbers to each and every place, as it was/is/will be at every instant of time, then I am supposed to have “established” a co-ordinate system.[3]

That I hope settles the confusion[4].

Endnotes :

[1] Even in a cartan-conscious book like the one titled “Gravitation” (Misner,Thorne and Wheeler), it is not unusual to see a paragraph in which they use these terms interchangeably. And I think this confusion is a de-facto standard in engineering and physics outside general relativity.

[2] It is an interesting question to ask - how many such numbers do you require to cover every place at every instant ? Experience tells us that we need at least four numbers. This is what we mean when we say we live in a “four-dimensional space-time”.

[3] Quite often, it happens that it is neither necessary nor possible to “establish” such a system. In that case, we tone down our ambitions and worry only about some places as they were/are/will be during some instants. Such a thing can be called a local co-ordinate system.

[4] Stated like that, you might wonder why people confuse between these two words. The point is this - often co-ordinate system is used to construct a frame. The trick goes something like this . To give a standard way of waiting, you go about as follows.

a) Take the set of numbers associated with the place where you start waiting as it was at the instant you started waiting.

b) Similarly, take the set of numbers associated with the place where you end up after waiting as it was at the instant you finished waiting.

c) Now, choose the kind of waiting which keeps the first three numbers the same between a) and b) and declare that kind of waiting to be standard.

Similarly, by fixing the third number instead of the fourth, you can define “North”. And you can do the same thing for defining “East” and “Up” using the rest of the two numbers. Such a frame defined using co-ordinates is said to be a co-ordinate frame.

Sometime ago, Micheal Fisher had come to TIFR. And he gave a public lecture about critical phenomena. It was a great lecture and the presentation was quite impressive.

However, it was supposed to be a public lecture and a lot of non-physicists were there in the audience. Fisher did try his best to take them along, but, I suspect most of them were lost [1]. It is, in fact, quite unfortunate. I think the kind of things he was talking about, are the kind of things everybody should know about.

As Cosma Shalizi writes in his notebook on statistical mechanics, “Statistical Mechanics (and Condensed Matter) [are the] first mathematical, natural science of emergent properties”. But, sadly enough, as he adds

If a non-scientist wants to learn about some large and important part of science, say planetary astronomy or genetics, there are usually a handful of reliable, uncontroversial, well-written, non-technical books about it to be found in the stores and libraries, which will convey at least something of the field’s history, problems, results and methods. By this point there must be dozens of good popular books written on evolution, particle physics, cosmology, relativity and quantum mechanics, notwithstanding that the last two are about as abstract and abstruse as science gets. There are even excellent popularizations of mathematics, in a continuous tradition from E. T. Bell (if not before). ….

A few months ago, when I was trying to explain some parts of my research to my father, I realized I was assuming he knew what statistical mechanics was, and something about how it worked, when in fact he did not. My first thought was to pass on some popular work about statistical mechanics (it’s only fair; he did it to me constantly when I was younger). A great many thoughts later I realized I could not think of a single one which didn’t stake out some very peculiar philosophical position, or did more than just blab about the second law, never mind something as good as Einstein for Beginners or The First Three Minutes or Does God Play Dice? Granted that relativity and particles and chaos are sexy, and statistical mechanics is not, it’s peculiar that there’s nothing. Stat. mech. is, after all, one of the essential theories of current physics, actually used by chemists and biologists and materials scientists, etc., the part of physics most directly applicable to daily life (you could illustrate the core of it with a coffee cup, and the whole with a kitchen), and bound up with deep puzzles about why time goes the way it does. This cries out for a remedy.(italics in the original)

And the deeper you go in condensed matter, popular science books become rarer to find. Whenever I try to talk about condensed matter physics to somebody back home, I am irrevocably drawn into talking about its “usefulness” vs what makes it scientifically interesting. Peter Armitage indeed has a point when he wrote -

…..
As a field we can be justifiably proud to have discovered the physics that led to the transistor, NMR, superconducting electronics etc etc. But this boon has also been a curse. It has made us lazy and has stifled our capacity to think creatively about outreach in areas where we don’t have the crutch of technological promise to fall back on.

This is a luxury our cosmology colleagues don’t have. They feel passionately about their research and they have to (get to?) convey that passion to the public (with predictably good results). We feel passionately about our research, but then feel compelled to tell boring stories about this or that new technology we might develop (which predictably elicits yawns and perhaps only a mental note to take advantage of said technology when it is available in Ipod form). We do this because we are bred and raised to think that technological promise is a somehow more legitimate motivation to the outside public than genuine fundamental scientific interest. It doesn’t have to be this way.

Due to our tremendous technological successes there is also the feeling then that at some level ALL our work should touch on technology. This is the easy strategy, but ultimately it hasn’t been good for the health of the field. This is because, for many of us, technology isn’t our passion and it shows…..

The reality is that many of us in CMP don’t have the inclination or interest to ‘make’ anything at all. For instance, we may pursue novel states of matter at low temperature and consider the concept of emergence and the appearance of collective effects to be just as fundamental and irreducible as anything in string theory. We should promote what excites us in the manner that it excites us….

Meanwhile, I just got hold of a book from TIFR library titled “Constitutions of matter” by Martin.H.Krieger[Amazon][American Scientist Review] [Journal of Chemical Education Review]. It is really not a popular science book, but if you like the kind of mathematical physics that statistical mechanics throws up, you might like it.

[1] Some of my colleagues were of the same opinion. In fact, I opined that biology students might have got something about scaling whereas my colleagues were a bit more pessimistic.

I was looking around for something to post for JustScience.net. (I’ll come around to plasma physics as promised sometime later this week ) .

Jennifer (of Cocktail Party Physics) makes a list of “the Top Ten Things About Physics We Wish Everyone Knew” - Lo and behold, I find one of my favorite topics to ramble about -

…
3. Frames of reference. Yet another bit of jargon so common to scientists, they forget that the phrase might not hold any real meaning for John/Jane Q. Public, even though it’s a fairly simple concept. It’s still necessary to define the term. Chad touched on this in his post on forces, but it’s central enough that it bears repeating. For instance, it’s tough for a non scientist to grasp why scientists occasionally argue about centrifugal versus centripetal force without a solid grasp of frames of reference. It’s just as critical when considering the differences, physics-wise, between linear and rotational motion, and to understanding why Einstein’s theory of special relativity was such a revolutionary advance….

The fact that this is my favorite topic is not a secret, of course. But, I’ll try a slightly different tune this time - I will assume that you’ven’t read any of the links in the previous line.

A frame of reference is basically a convention that is very useful in physics. Before going into what it actually is, let us look at a simpler but a related concept.

Consider the surface of the earth . On the earth, we find it very useful to name a specific direction as “North”. You can goto any place on earth(except the poles) and you have a reference direction which all of us have agreed to call as “North”. Similarly, we call a specific direction as “East”.

Now, why is this a useful thing ? It is useful because it gives a way for people to communicate with each other. Consider, for example, a person on a plane flying over the place marked P in the figure below. Now, if we want to tell the pilot to goto the place marked Q , one of the easiest ways to communicate the instruction is to ask him to go say 5 kilometres towards East.[1]

Let me invent a shorthand and give an instruction - “Fly 5 E “

Similarly, if you have a person at the place marked R , to goto Q , you just have to tell him to go 5 kilometres towards East and then 4 kilometres towards North. So, now the instruction is “Fly 5 E + 4 N“. So far so good.

Now, imagine that I intend to meet this pilot at the place Q some 10 hours after now. So, including the travel time, I want him to wait for 10 hours and be at Q after 10 hours. Now, how do I say that ?

Let’s assume the time taken for travel is very small. So, basically, I tell the pilot to fly 5 E + 4 N and then wait for 10 hours. Let us combine the two instructions into one and send him a single line instruction “Fly 5 E + 4 N + 10 T ” - of course, T represents waiting or “flying in time”.[2]

Now, the question is this - Is my instruction unambiguous ? At the first sight, it does seem to be . But, I will insist that it is not !

To understand why, consider this possibility - say the pilot goes to the place Q and he is very tired after the journey. Since he has ten more hours, he decides to have a good sleep. So, he boards a good train going towards the place S and goes to sleep. He wakes up after ten hours to find himself at S. Having faithfully followed my instructions, he is angry that I am not there !

You might be saying - ” Come on, this is cheating. He didn’t just wait. He also traveled some more distance !” But, the pilot can insist that no-he didn’t go anywhere, that it was the stations which moved towards him as he slept. This might sound very philistine, but, technically, he is right !

What is mere waiting for one person can actually be waiting plus some additional motion for a second person, provided the first person is moving as seen by the second person. So, in a sense, what the first person calls waiting is actually what second person sees as waiting with flying.

So, the moral of the story is that it is not enough if I just say “Wait for ten hours”. It is like saying “Fly for five kilometres”. If I tell you “Fly for five kilometres”, you should ask me back - “Along which direction ? ” . Similarly, if I say “Wait for ten hours”, you should ask me according to whose definition of “waiting” - you see like “North” and “East” we also have to define a “way of waiting” so that our instructions are unambiguous.

So, you might be wondering, what has all this got to do with frame of reference ? The answer is simple - A frame of reference is basically a convention which decides ad hoc - what is “North”, what is “East”, What is “up” and what kind of “waiting” is a standard at each place and for all times.

The point about frames of reference is that one way of definition is as good as any other - sky is not going to fall if tomorrow everybody starts calling East as North and North as East. But, I am saying that and much more - heavens are not going to fall even if all of us change our convention of what it means to say that we are just “waiting” .

So, that in short, is what a frame of reference is . I’ve not addressed the other things that Jennifer mentioned - “centrifugal versus centripetal force”, “linear and rotational motion” and things like inertial and non-inertial frames of reference. I’ll probably take it up later in some other post.

[1] Actually I am cheating you. If you take the given figure to be a representation of earth, the distance shown would be about a thousand kilometres. If I had actually shown 5 km on that figure, it would be so small that you would have a hard time seeing what I’ve drawn.

[2] Of course, I am just repeating what I had already told before . The things I put in bold are basically vectors, and T is what physicists like to call a “Time-like vector”.