### March 26, 2007

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 .

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 !

## LaTeX / Maths blogs

### February 21, 2007

• WordPress.com introduces $\LaTeX$. 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 $E= \sqrt{p^2c^2+m^2c^4}$ . Of course, the downside is that in rare cases, $\LaTeX$ 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 $A_\infty$ 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.

## What is a frame ?

### February 5, 2007

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”.

## News From Indian Blogsphere

### January 19, 2007

I’ve updated my blogroll adding many new blogs and removing some dead links. Now, to some news..

1) Via Desipundit,

Dr. APJ Abdul Kalam raises the question of terrorism on Yahoo Answers and the world responds (Yahoo staff assure it is indeed the President)..

I should grant it to our president – sometimes he is just amazing ! And among the respondents is Kiran Bedi herself ! And my opinion, if you’re interested, is not very much different from hers as far as the general question is concerned. And it is very difficult to come up with a more useful reply unless we focus on to a specific case of terrorism…

2) Arunn points to a call to blog Just Science for one week

…we would like to propose a Week of Science, to begin on Monday, February 5, and end on Sunday, February 11. During that time each blogger should post about science only, with at least one post per day…

Bloggers who self-identify as scientists and science writers should post on:

1. Published, peer-reviewed research and their own research.
2. Their expert opinion on actual scientific debates – think review articles.
3. Descriptions of natural phenomena (e.g., why slugs dissolve when you put salt on them, or what causes sun flares; scientific knowledge that has reached the level of fact) …

I guess I should sign up too. And like Razib, I should start putting posts on queue – there is no way that I’ll be able to write one post per day.

Update :

3) Abi points to an interesting report on primary education in India.

## The Life of a star For Dummies !

### January 5, 2007

When going through one of the posts in this month’s edition of Philosophia Naturalis, I discovered a cute set of animations at Voldosta State University’s site. And the subject ? Well, as the title should have already told you, it is the life of stars !

What is going to happen to our Sun in the future ?

What really happens inside the sun as it slowly dies ?

And, a more interesting question – what happens if you have a star bigger than the Sun ?

Or, if that sounds like a remote question , then try this – what makes the carbon in you and me ? And Why do astronomers proudly declare that “We are Star dust !” ? 🙂

That is not the only reason why these animations caught my attention. You see , when I was in my school, our physics book had about two pages about how stars are born and how they die. And our physics teacher (Mrs.Sumitra Raghavan, in case you’re one of my schoolmates and you’re curious to know who I’m talking about) decided that that part of the lesson would be left for me to teach it to the rest of the class.

Indeed, if I remember correctly, the whole of cosmology/astrophysics chapter was taught by students . I did try my level best then (and had great fun 🙂 ) – but, now, looking back at that attempt at “teaching” , I can’t but feel a slight twinge of guilt at not being able to convey the wonder of it all…

The first thought which occured to me as I saw these animations, is how effective I could’ve been at conveying what I wanted to say, if only I could’ve showed the class something like this !

## Philip Ball

### December 13, 2006

For sometime now, I’ve been reading a popular science book titled Designing the Molecular World: Chemistry at the Frontier by Philip Ball(you can find a short biography at his site). It’s a decent book which I will recommend to anyone who is interested in popular science.

So, Imagine my surprise when I found his blog titled homunculus(via Highly Allochthonous) ! It is filled with some great scientific writing.

Just to give you a taste –

Are chemists designers?
Not according to a provocative article by Martin Jansen and Christian Schön in Angewandte Chemie. They argue that ‘design’ in the strict sense doesn’t come into the process of making molecules, because the freedom of chemists is so severely constrained by the laws of physics and chemistry…

Chemists won’t like this, because they (rightly) pride themselves in their creativity and often liken their crafting of molecules to a kind of art form….

It’s flat, it’s hot, and it’s very weird

Graphene, that is. I have been talking to some fellows about this new wonder-stuff, which wowed the crowds at the American Physical Society meeting in March. Mainly to Andre Geim at Manchester, who is one of those wry chaps you feel you can inherently trust not to load you down with hype. I’m working on a feature on this for New Scientist, which will delve into the decidedly wacky physics of these single-atom-thick sheets of pure carbon. It’s not your ordinary two-dimensional semimetal (yes I know, name me another), mainly because the electrons behave as though they are travelling at close to the speed of light. So here’s an everyday material in which one can investigate Dirac’s relativistic quantum mechanics, which normally applies only in the kind of astrophysical environment you wouldn’t want to end up in by mistake…

Further, I came across an article titled Newton’s Curse written by him in his webpage. It talks about the ‘alchem’ical interests of Newton.

And here is an excellent article titled Beyond Words : Science and Visual Theatre which I liked a lot. The summary reads

Science is becoming increasingly visible in the theatre, where it is often regarded as a fertile source of ideas and metaphors. I argue that we should not overlook the potential of science as an abundant well of visual imagery for the theatre. Scientific research and discovery can provide new physical languages for theatrical expression, and new ways of looking at and depicting the world. Scientists at the nexus of experiment and discovery have often seen things never before observed by human eyes; such visions, recreated or re-imagined for a theatre audience, can stimulate the kind of wonderment that is central to the theatrical experience.

## Nobel’06

### October 5, 2006

And since this is not a blog confined to physics, I will also link to the Nobel prize announcement in Physiology or medicine and chemistry.

Frankly, I have trouble distinguishing which is which from the citations alone 🙂 And I’m not alone *…
Try guessing – a Nobel has been given to Roger D. Kornberg “for his studies of the molecular basis of eukaryotic transcription” and a Nobel has been given to Andrew Z. Fire and Craig C. Mello “for their discovery of RNA interference – gene silencing by double-stranded RNA”.

And I’m late as usual, but should wish Happy Birthday to the one who deserved the Nobel(but didn’t get it) – anyway, as Einstein remarked “Generations to come will scarcely believe that such a one as this walked the earth in flesh and blood”.

* If you’re further interested in the question “Is it chemistry ? “, you should have a look here and here(might need a subscription).