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Arunraja Shanmugavel
Lives in Chennai, India
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Arunraja Shanmugavel

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[New blog post] - Do What needs to be done http://checkarun.blogspot.in/2013/10/do-what-needs-to-be-done.html
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Mabu abu
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Wow !
 
This was great. Part high-level algorithms description, part magic show.
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Look at this GIF long enough and you can make the train change direction simply by thinking about it
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Very nice..
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Products of unhappy job http://hadonejob.com/
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The game of life, inside the game of life, inside...
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Have him in circles
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Arunraja Shanmugavel

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Self made wallpaper on theme [Do What Needs to be done] source - http://en.wikipedia.org/wiki/Shoma_Morita
Wallpaper made on Project 330, an online platform for creating, sharing and downloading wallpapers.
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7 Signs You Are a Fast Learner.
What is your sign?
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:O
 
Billions and Billions

As of this writing there are 861 confirmed extra-solar planets.  These are planets for which we not only know they exist, but we know some things about them, such as their orbit, mass, etc.  The Kepler mission, a space telescope surveying nearly 150,000 main sequence stars, has found nearly 20,000 possible planets.  Of these, we have found more than 2,700 candidate planets.  These are planets for which we know some of their properties, but which haven't completed the rigorous process of being officially confirmed. This is a huge change from just twenty years ago, when there were no confirmed main-sequence exoplanets.  

With nearly 3,000 candidate planets we can now do a bit of statistics on just how common planets are, their typical masses, and the type of stars they orbit.  You can see some of these statistics in the figures below.  The first image shows the locations of candidate planets seen by Kepler, while the second shows the distribution of these planets by mass.  

Of course we have to be a bit careful when looking at the statistics.  Kepler finds planets by a process known as the transit method.  It measures the brightness of 150,000 main sequence stars looking for the periodic dimming of a particular star.  There are several reasons why a star might dim, but one of them is because a planet passes in front of the star, blocking some of its light for a short period.  The bigger the planet, the easier it is to observe.  It is also easier to observe periods with shorter orbital periods than longer ones.  With shorter periods you can see more of them for a given observation time.  As a result, Kepler will find short-period planets first, and longer period planets as it keeps watching the stars.

Even with this observational bias we can see that planets have a range of sizes, and even Earth-sized planets are relatively common.  Popular science articles often use the term Earth-like, but that sounds like they have water and gazelles, but just because they are Earth sized doesn't mean they are habitable.  That's a topic for another time.

The transit method is just one way to discover extra-solar planets.  Another popular method is radial velocity method.  This method observes starlight and watches for a periodic Doppler shift.  As a planet orbits a star it causes the star to wobble a bit (http://goo.gl/LixbF).  As a star wobbles, its light is red shifted or blue shifted slightly.  By measuring a star's wobble we can detect the planets orbiting it.  Again this has a bit of bias.  Larger planets orbiting smaller stars are easier to observe than smaller planets orbiting larger stars.

So just how many planets are there in our galaxy?  A recent study (http://goo.gl/NcKSa) estimates that most main sequence stars have planetary systems, with an average of about 1.6 planets per star in our galaxy.  Since there's at least 200 billion stars in the Milky Way, that means more than 300 billion planets.  An other survey (http://goo.gl/CgjGO) looked at planets orbiting M class (red dwarf) stars, and estimated about 6% of red dwarfs have Earth-mass stars in their habitable zone.  Since about 75% of stars in our galaxy are red dwarfs, that means there may be 4.5 billion Earth-like planets in the Milky Way.  Earth-like in that they have a mass similar to Earth's and a temperature that could allow for liquid water on its surface.  Of course that's just in our galaxy.  There are likely 500 billion galaxies in the observable universe, so there may be a sextillion planets similar to ours.  Sextillion as in 1 with 21 zeros after it.

Billions and billions indeed.
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Work and play are words used to describe the same thing under differing conditions - Mark Twain 
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Have him in circles
266 people
Shailesh Gupta's profile photo
Shahul Hameed Khan's profile photo
Sudhanantham Balakrishnan's profile photo
Roshan V L's profile photo
Gnanasekaran Balasubramaniam's profile photo
Gopi Krishnan's profile photo
Shankha Acharya's profile photo
karan agicha's profile photo
Neeraj Kumar's profile photo
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Currently
Chennai, India
Previously
Erode, India
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Dinner at hotel was not excellent( very hard rottis ) but Good
Public - 3 years ago
reviewed 3 years ago
Noon Buffet is Cool
Public - 3 years ago
reviewed 3 years ago
3 reviews
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Map
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Very costly, Less quantity, less tasty
Public - 4 years ago
reviewed 4 years ago