Story of a 'spinning lady'

Did you notice the figure above? To see the spinning lady, click this link and return back. Is it a spinning lady? In which direction, you feel the lady is spinning? clockwise or counter-clockwise? One can feel the spinning of the lady in either clockwise or counterclockwise. But once you feel lady spin in one direction, your brain continues in that state and insist to be in that state. If you feel that the lady is spinning in clockwise, it is too difficult to see the motion in counter-clockwise direction. But sometimes our brain switches from one state to other state automatically, but changing the state of feeling of brain is difficult to achieve manually.
This is a beautiful eye illusion. Do you know how that beautiful lady, cheated your brains?
Answer is, the lady didn't cheat you, but the cheater is her shadow. Actually, the image shows the shadow of a spinning lady. In this, a 'shadow' plays in important role in cheating you. The pure shadow of an image will not provide the entire information about an object to the brain. From a shadow, we can't predict whether the front side or backside of the object we are viewing. If you didn't understand what I just said, please go through an example.
Look at the picture below.
The middle picture is photo-shot of the spinning lady. Concentrate on the picture and tell what you are viewing- the frontside or backside? It may be both. Look at the left picture. It is the modified version of middle one by adding eyes in her face. Now you feel that you are viewing the front side of the lady. At the same time, you see the backside of the lady in the right picture, but that also a modified version of middle picture with marking of a hair bud. This is important to be noted. While you are viewing the middle picture only, your brain fall in to the mess of finding whether the shadow is of the front side or backside. Then your brain 'randomly' choose one possibility (not actually). But in other pictures, your brain has powerful proof that indicates the state of the lady's body.
Now the problem associated with the spin direction of the lady is not vague. If your brain 'assumed' a side of the lady's body you are viewing, this will determine which direction, she is spinning.

A lady who travelled faster than light....

I recently read and much inspired by this old poem:

Once there lived a lady
She could travel faster than light
She left out of home today
And returned back yesterday!

Sometimes the real things are stranger and mysterious.....

PHET science simulations for students

PhET interactive simulations - Fun, interactive, research-based simulations of physical phenomena from the PhET project at the University of Colorado.

I found those simulations were good in today's eduction- thanks for university of Colorado. Most of them are intended for Upper and High school students and pre- graduate students. However, if you just spend your time in experimenting with it, I am sure you get something new. Phet interactive simulations create a virtual lab environment. It's just a feeling that to enter into a physics or chemistry lab in a college. You can do anything in your own lab. Nothing to fear. No more comments from teachers...
One more advantage is that, you only need a java powered web browser. You can browse through different lab environments. If you like PhET virtual lab, you can download it for offline usage. Linux(80MB), Windows(97MB) and Mac OS(85MB) installation supported.

Browse phet simulations
Download phet for offline usage.

Why there is so many constants in equations?

I will tell you the secret of constants in mathematical equations. They are not intruded or the error or nothing, but it is essential part of the equation. I will tell you some facts while going on your story. I will exemplify what you want in this story.
Consider you are a young scientist. You close your room's door and start experimenting on something when you get leisure time on Sundays. You are doing something seriously on your table, with an electrical circuit. Your aim is to find the dependence of a node voltage X (ie, a voltage in a part of the circuit). You came to know that X depend upon the supply voltage V. You start experimenting and plot graph of X for different values of V. Then you
got a graph like this:
It is perfectly linear. So you write,
X is directly proportional to V
To be more specific, X increases for an equivalent increase in V. You repeated your experiment and plot another characteristics with time. This time, your supply voltage kept constant. Plot X with time t.

From the plot, it easy to find that dependence is,

X is directly proportional to e^(-t)

Then from the above town experiments, you can write that,

X is directly proportional to V*e^(-t)
ie, X = K*V*e^(-t) where a K is the proportionality constant.

You can find K from single experiment. Once you got the value X when for a particular V and t,

K = X/(V*e^(-t)

But I want to tell you that your experiment as well as your mathematical expression is not perfectly true. A true dependence of X on it's environment will be very complex and tedious to express in mathematical form. Your X may depend on the atmospheric pressure, temperature, material properties,...raining in New Delhi,.....war on Iraq and so so.
After several years, you repeated your experiment and find that X depending on temperature also. Temperature has a direct linear relationship (like V) on X. But last time, you didn't got it. What's the reason? You were not aware of that, you did the experiment in room temperature itself. But this time you get different answers in day and chilled night. Now you modify your equation as,

X is directly proportional to V*T*e^(-t) where T is the temperature
X = L*V*T*e^(-t) where L is the proportionality constant.

Here I want a point to stress. Do you think your previous equation was wrong? Not at all. It is correct in an isothermal environment. But it become wrong in a temperature varying environment. A single measurement depending upon many things in the surroundings. But many of them can be ignored, because, they have less relationship with X. Something can't be ignored, but they may not be measurable (such as number of electron collision per second).In such cases, just put a constant for that, as long as they are constants. To be more clear, if your experiment depends upon the radius of earth, just put it as a constant in your equation. But when you do the experiment in moon, your experiment may troubled, unless you replaced the radius of earth with moon. I meant that variables can be considered as a constant or variable according to the environment.