Earlier this month while driving to astronomy outreach program on a winter night, a friend of mine was telling me about his audio cassettes collection and portable cassette player. Discussion went on to electronic gadgets and at the end I was stumped by his question – “what makes a small device to store thousands of songs? What is so special about silicon in electronics?” I didn’t speak a word for next few minutes, and then I started talking. I told him about semiconductors, transistors, ICs, programming, storage… NOT in this order. For next fifteen-twenty minutes I spoke whatever I learned to get Diploma and Degree in electronics engineering. Sadly at that time what I told him was not helping to clear concepts and he literally went on back seat to sleep! :P Now let’s see what Electronics is !?!

Electronics axiomatically is about electrons and when studying it one has got to learn this

  • Flow of electrons is “Current”. This current flows from higher potential to lower potential.
  • This difference between potentials is called as “voltage”.
  • Silicon is semiconductor which is why it is widely used in Electronics.

Electronic System

Almost all electronic gadgets / instruments / control systems are generally box shaped (or whatever aesthetically looks good). It has knobs, buttons, displays termed as user interface (UI). It enables user to operate the system. If it is computer system, it process information and stores it. If it is control system, it controls to operation of machines connected to it. If it is communication system, it transmits/receives the electro-magnetic signals. So it can be said that today’s electronics isn’t stand alone system. It is merged with computers, mechanical and communication systems. Although technically electronics systems can be categorized as Analog and Digital, it is hard to differentiate it by looking from outside. Today’s systems are intelligent because of digital computing systems. It senses its own performance, environment in which it’s working and tries to perform at optimum level all the time.

Electronic System is pretty simple to define in one line. It takes input, processes it and delivers output. Electronic system needs power supply to work. Power supply injects electrons in the circuit. Circuit is a center of every electronics system. Circuit physically is a board (PCB) with lots of electronic components, devices mounted on it and connected with others by conducting tracks on a board in a designed manner. Circuit itself is designed to work or designed to make sure that system works exactly as it is intended. When power is applied, each component in electronics exhibit unique specific characteristics. Basic components of electronics are Resistor, Inductor and Capacitor. It also includes semiconductor components and hi-tech semiconductor devices. Combination of various components and devices serves the purpose.

IC to Atom, Atom to IC.


When we see PCB, first attractive thing we notice on it is black chip which looks like tiny creature having lots of legs. It is called integrated circuit chip (IC). We should thank Nobel laureate Jack Kilby for the invention of Integrated Circuits at Texas Instruments. The rapid development of Computer technology is because of IC. Since 1960’s capability of fabricating more complex circuit on compact IC is increasing. IC is composed of thin (nanometre) silicon wafer on which “many” transistors are etched (analogous to carve) and are interconnected in a specific manner. For physical connection metal connecting pins are taken out. Whole thing is fabricated in ceramic (Black structure) with standard packaging shapes. Analog applications ICs are signal amplifier, frequency filters etc.  Digital application ICs are Digital logic gates, micro-controller  processors, memory storage. There are lots of steps involved from designing to manufacturing of IC – Shown in short in next image.

IC design steps

IC design steps

  • IC DS1307 is real time clock. It counts each second, minute, hour, day and date. This data can be fetched by micro-processors at any instant.
  • IC LM324 contains four operational amplifiers which can be used as comparator. Compares two signals and tells which is high or which is low.
  • IC 555 is popularly used as timer.

Transistor Count

  • According to Moore’s Law the number of transistors on integrated circuits doubles approximately every two years. Now period is often defined to 18 months.
  • Intel’s Core i7 processor was introduced in 2008. Its size is 263 mm^2 and contains 731,000,000 transistors.

Before the invention of IC, there was important breakthrough in 1947 – Invention of transistor at Bell telephone labs. There was need of less bulky components than Vacuum Tubes which were slow, big with several other operational drawbacks.

Silicon Atom

Crystal Structure

Silicon is semiconductor which has 4 electrons in its outer-most shell. One atom of silicon bonds with other four electrons. So no electron is free to carry the current. When impurities like Phosphorus and Boron are added in pure Silicon it forms N type (One electron free to go in conduction band) and P type (One Hole free) silicon respectively. When P type and N type material are connected together, a junction is formed. This junction restricts the charged carrier to “move” from one type to another. Consider this as “OFF” state. But when appropriate external power supply is given, junction can be made open and current starts flowing. Consider this as “ON” state. Thus semiconductor silicon with additional impurities can make a components which can be operated as conductor / non-conductor as per requirement. This characteristic is basic building block of electronics.

Diodes, Transistors and Thyristor family components (Widely used in Power electronics) are fabricated using various combinations P type and N type materials. We can control flow of electrons through components, electron density in a current, Voltage levels and thereby power level of a signal.BJT_NPN_symbol

A transistor in a circuit can be used as Amplifier, Switch and regulator. Transistor as a switch is vital in digital electronics. Digital electronics works only on 2 states. – Logic 1 and Logic 0. Transistors can switch between ON/OFF state more than thousand times per seconds. High speed transistors have switching speed more than that. This corresponds to state of the transistor ON and OFF. Hold this thought in a mind.

Programming Micro-controller (High Techy Techy!)

Suppose I want to design a system. There is a key / Button named K1. The moment  K1 is pressed, digital display should show message “Gotcha !” For this there is need of a device, which senses “key pressed” event and drives digital display to show message. So microcontroller (uC) IC chip is used.

block diagram

A program i.e. code is written to continuously monitor a key connected to uC. As soon as key is pressed uC sends commands to digital display to be ready; Transfer a data i.e.  message from uC to display; Latch data display’s memory and finally show it.

For every operation above, instructions (Pre-defined instructions provided by manufacturer) are written in specific programming language on a computer. Each instruction programmer writes, software converts it into HEX code (Hexa-Decimal number system – 0 to 9 and A to F) – machine language. Hence here is conversion of programming language into HEX code. Final code is needed to download into the uC. Downloader converts Hex code into Binary code (0 and 1). Hence whole program including message “Gotcha !” is now in the Binary code. All 0s and 1s.

On other side, Printed circuit board is designed to make connection between a key as input to uC and output from uC through data cable to digital display. Power supply is connected wherever necessary.

As told earlier

  • Each instruction has unique code.
  • ICs are made up of transistors.
  • Transistors can switch between ON/OFF state.

uC reads “Binary code” of a instruction of program download into its ROM, specific “set of transistors” becomes active and turns ON/OFF accordingly. This is called as execution of an instruction. This happens every time, for every instruction.

Digital Display also has its own processor. It differentiates between commands and data coming in and shows message accordingly.


Memory: ROM, PROM, EROM, EEPROM, FLASH. These are types of memory chips. Earlier memories were only read only memory. Then came programmable ROM. User could write data into it but could not erase it. After that new memory chips were manufactured. Exposing chips to UV light could erase its content. New Chips after that used to be erased by electricity. Now we use Flash memories in which data read/write can be done in fraction of a second. According to data, bit by bit transistor is turned ON or OFF. So very roughly one transistor along a capacitor holds i.e. stores one bit of data (This sentence isn’t totally correct).

Similarly, many components /devices / technologies are invented /  improved which can be categorized in “n” number of sub-fields of electronics. Sensors, actuators, transmitter/receiver, antennas, semiconductor materials, micro-processors, VLSI technology, displays, batteries, Digital Signals processors, communication protocols, filters, amplifiers, transformers, electro-mechanical switches, lighting, etc etc etc…

The “flow of electronics” is now one of the reasons why we live cherished life.

Also check this classic XKCD –  http://imgs.xkcd.com/comics/circuit_diagram.png

Real image of India on Diwali Night

This image is result of image enhancement by NOAA scientist to showing population growth between “1992 – 2003”. This is NOT image of India on Diwali night.

This image is result of image enhancement by NOAA scientist to showing population growth between “1992 – 2003”. This is NOT image of India on Diwali night.

There was a hoax spreading over all social media websites since past couple of years. A coloured image (Shown Above) of India taken from space, claiming the colours are because of lights during festival of Diwali. A year ago I and Omkar spent a lot of time to dig out from where that hoax started. But all went in vain. Although today I found original information about it here – Earth Observatory (EO) dated November 15, 2012.

EO Website added “In reality, any extra light produced during Diwali is so subtle that it is likely imperceptible when observed from space.” It also states image circulating on social media was not exact what it claimed about colours of Diwali.

In 2003 NOAA (USA’s National Oceanic and Atmospheric Administration) scientist Chris Elvidge used data of population growth over time and enhanced the image by various colours.

  • White – prior to 1992
  • Blue – became visible in 1992
  • Green – became visible in 1998
  • Red – 2003

Original image (Shown below) is “Night-time lights of India”.

Nighttime lights of IndiaCredits: NOAA

Nighttime lights of India
Credits: NOAA

In other news yesterday NASA also released chunk of images. Many news agencies have noted it and now real photo of India on Diwali night is floating in Indian news papers.

Nasa’s Soumi NPP satellite released new images of the earth during nights called Black Marble. Soumi NPP collects remotely sensed data of land, ocean and atmosphere and distributes to various scientific communities for processing. Image set has many images of earth globe, continents and countries check here and –


Image of south Asia shown below is real! This image was acquired on during Diwali festival on November 12, 2012. To my surprise website mentions Diwali and describes it as – “Every fall, Hindus around the world light lamps, candles, and firecrackers as part of a five-day festival known as Diwali. The celebration, which has roots as a harvest festival, usually falls between mid-October and mid-November. In 2012, it began on November 11.”

On November 12, 2012, the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this nighttime view of southern Asia. The image is based on data collected by the VIIRS “day-night band,” which detects light in a range of wavelengths from green to near-infrared. The image has been brightened to make the city lights easier to distinguish.Credits: NOAA, NASA

On November 12, 2012, the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite captured this nighttime view of southern Asia. The image is based on data collected by the VIIRS “day-night band,” which detects light in a range of wavelengths from green to near-infrared. The image has been brightened to make the city lights easier to distinguish.
Credits: NOAA, NASA

Need of New drugs for TB

You see that white fuzzy object in the centre  Well, it consists of thousands of stars. Among these some are bigger than our sun and some are smaller. And there are many which can’t be seen by our naked eyes. Our solar system is made of sun at the centre with eight other planets revolving around it. And in the whole universe we know the only planet which has life  – Earth! The living planet! Earth has life in many forms. Plants, trees, birds, animals live together interdependent on each other. Few feed on plants. Few animals feed on other animals.

Not to forget micro-organisms  Life on earth started with it! So life on earth is pretty complex. But in all of these, human species stood aside of other living things. With its own intelligence man is the leader on this planet. Even though no species on the earth feeds chiefly on human flesh, there are many reasons which are catastrophic to man.

There is no way to say that intelligent Man is immortal and there are many ways in which human’s life comes to demise. TB is among the catastrophic diseases.

Tuberculosis, its symptoms and drug used

Tuberculosis has been present in humans since antiquity.  mycobacteria cause serious diseases in mammals. TB is one of them and is caused by Mycobacterium tuberculosis. TB is contagious and airborne. Dr. Sawant who gave some information about it to me said, “It mainly affects lungs. If bacteria are detected in sputum it is categorized in category1. In some cases i.e. in category2 it also affects Pleura and intestine. These bacteria enter in body through air.” Infected person coughs and micro-organisms in droplets travel through air and if other person breathes in that air, he gets infected, said Dr. Sawant. On asking about why TB is called as disease of poverty he said, “Body resistance of poor people is not so good because of lack of nutrition”. What I think – may be the standard of living also major factor in spreading TB.

Various combinations of medicine – ethombutol, pyarazinamide rifampicin are given to patients according to his health condition. It takes around 6 months to recover from TB in some cases more than that.

Since 1995, 46 million people have been successfully treated and up to 6.8 million lives saved through DOTS and the WHO’s Stop TB Program.

India’s Revised National TB Control Program has made efforts for systematically engaging all care providers through a public-private mix DOTS and has developed guidelines for the involvement of NGOs.

Still the purpose is not served.


TB is lethal disease. The number of people who died from TB fell to 1.4 millionin 2010, including three fifty thousand people with HIV, which means around 4 thousand deaths every day.

Being the largest country in Asia, India is the highest TB-burden country in the world and has contributed 25 percent of the estimated global TB cases in 2010.

There is need to take a note of important point – There is significant number of people who leave treatment without completing it.

Need of New Drugs

Multudrug resistance (MDR) TB and extreme drug resistance (XDR) TB are big problems in getting rid of this disease. Science Magazine reports why TB is hard to cure. Recently Down to Earth Magazine reported improved cure for TB.

So there is need of new drugs which would be very effective in short period of time. It should also be affordable as funds shown by WHO in this factsheet are so high.

Tb is more prone to poor people in developing nations, elevating the standard of living would help in solving problem.

We, humankind are blessed by nature/evolution to be the leader on this planet; it’s our moral responsibility towards society to leave no man behind. We have to be obliged to take every section of society with us to prosperity.

Vigyan Prasar and OSDD are organizing Youtube video competition on on “The Need of New Drugs for TB”. Last date of submission has been extended to 30th November 2012

My entry in competition is coming soon!


Video by me and Aaditya Patil  on Youtube is live now.

Electric Transport – Today’s “Future Cars”

When I was in school, there was a awesome vehicle in my town. Anyone could discriminate it easily. Very unique small white car was having only two seats, unlike others with at least four seats commonly seen on Indian roads back then.

REVAi electric vehicle Credit: Wikipedia

Later I came to know it was Reva! That Reva was battery powered vehicle. A Bangalore based Reva Electric Car Company was co-founded by Chetan Maini in 1994 with joint ventures from USA. Mr. Maini studied Mechanical engineering in USA and till now has many awards for entrepreneurship and patents for energy managements for electric vehicles. He started company with the vision of stopping the climate change. Till March 2011 Company had marked sell of 4000. Since mid 2010 Mahindra bought major stake in Reva it is now Mahindra Reva Electric vehicles Pvt. Ltd. The latest Press-Release states Company inaugurated new plant which has solar energy and water conservation systems in it and is lit by energy efficient LEDs. Company had already introduced new technologies like car running on solar energy, 15 minutes charging time to run 25km and power the house on energy generated by car. As reported by HT last week, brand new Reva NXR is expected to be launched in November and company is going to set-up 50-200 charging stations per city! Target is to sell 10 thousand cars per year. A car has four seats and has either lead acid or lithium ion batteries.

Electric Vehicles – Model S and Roadster
Credit: Tesla Motors

Well, in the west Elon Musk’s (@elonmusk) Telsa Motors head-quartered in Silicon Valley – Palo Alto California, has reached mark of thousand bodies of Model S electric vehicle.Model S car runs about 480 kilometers per charge with the speed of 88km/hour. Whereas existing Reva models can run 80km to 120km. Tesla’s another vehicle Model X’s deliveries are expected in 2014. (Do check this webpage! See its falcon wings!) Model X has three-row seats and will come in two battery option 60 kWh and 85kWh. It is combination of SUV and Minivan. Tesla motors also has sports car named Roadster which is sold out in North America. Other than Tesla motors Mr. Musk is known for his organizations SpaceX – private rocket and spaceship launchers, Paypal.

Mr. Musk tweeted this pic – ““V proud of Tesla team for completing 1000th Model S body. More cars made this month than entire rest of year ””

All in all, the future cars will surely be running on electric power with great efficiency. May be this power is generated from solar energy. So it should not be greedy to fantasize about public transport vehicles running on electricity rather on renewable energy!

Credit: Tesla Motors

Unravelling mysteries of the Universe

Telephonic Interview with American astrophysicist George Privon. About his field of research and his experience at Indian observatory GMRT – Giant Metrewave Radio Telescope. This interview was published in “Satellite Science” magazine Feb-2012 issue in Marathi language.

Mr. Privon is currently a 6th year graduate student in the Department of Astronomy at The University of Virginia.

Question: Mr. Privon As I have through your profile we find that your field of work is very large. Tell us about it.

Ans: I started out studying active Galactic Nuclei (AGN): Supermassive black holes which have gas falling into it. After that I started studying the galaxies which have significantly higher rates of star formation than our own Milkyway. This all work comes under “Galaxy Evolution”. This essentially dominates my research interest. And this all research leads to resolving a main question “why galaxies we see today are the way they are?” This is very ambitious undertaking and researchers select very small area to focus on.

Question: Could you elaborate more about this Active Galactic Nuclei?

Ans: Sure!There’s evidence that all massive galaxies have a supermassive black hole in their centers. These black holes are roughly 0.1% of the mass of the galaxy. In most galaxies, this black hole isn’t doing much. But in about 10% of galaxies, there is gas falling into the black hole. As the gas falls in, it releases energy. Much of the energy is emitted as radiation, from radio waves through X-rays. Releasing energy this way is much more efficient than fusion (which is how stars produce their energy), so in some cases the small region around the supermassive black hole can actually outshine the galaxy in which it sits. The fact that all massive galaxies seem to have a supermassive black hole and that the mass of the black hole is roughly a set fraction of the total galaxy mass, it suggests that the growth of the black hole and the growth of the galaxy are linked, which is a bit surprising because the black hole’s gravity only dominates very close to it, and so the rest of the galaxy essentially doesn’t even know the black hole is there.

Question: which are the groups you are working with, is this with Virginia University where you are currently working?

Ans: Yes, there is a general “Galaxy Evolution” group which includes members from the University of Virginia and the National Radio Astronomy Observatory. There’s a wide range of interests in the group, from local galaxies, to galaxies in the early Universe. I mostly focus on extreme systems in the local Universe. They are called the Luminous Infra-red Galaxies” (LIRGs). Essentially they are systems (often where two galaxies are merging), where stars are forming at 20-100 times the rate of our own Galaxy. But there is much gas and dust in these mergers, which absorbs the light from the newly formed stars. So instead of seeing lots of optical and ultraviolet light, all of that energy comes out in the infra-red  To obtain a better understanding of what is happening in these galaxies we are collecting data in multiple bands like radio, infra-red  optical, ultraviolet, X-rays. because each band gives you different information. This was the motivation for the trip to the Giant Metrewave Radio Telescope a few months ago.

Question: So how many galaxies or which did you focus on, while at GMRT?

Ans:  The whole sample I am looking at has about 200 galaxies, about 50 which are well suited to observe from the GMRT. While the galaxies are relatively close to us (compared to the size of the Universe), they are still  far enough away that it takes at least a few hours to detect the gas in them. So I selected three galaxies to observe as tests. I’m happy to say that the observations were successful. Also I found the faculty and staff at the National Centre for Radio Astrophysics very friendly and helpful both in helping with the observations and in talking about science.

Question: which are the other telescopes you have used for your regular observation?

Ans: The other two telescopes I use are the Expanded Very Large Array (EVLA) in New Mexico (USA), and the Westerbork Synthesis Radio Telescope (WSRT) in the Netherlands. With the GMRT, someone needs to physically go to the telescope and collect data. With the EVLA and WSRT, you send them a script and someone there does the observations for you. But after that, analyzing the data is very similar. I much prefer going to telescopes and taking the data myself. There’s something about being there that is just so much fun.

Question: Your website also mentions “Hubble” in your work. Tell us something about it.

Ans: My work with data from the Hubble Space Telescope is actually for projects on AGN. But for the AGN projects essentially we were looking to study how AGNs can interact with gas farther out in the galaxy. A previous project, while I was at the Rochester Institute of Technology, studied at about 80 galaxies with AGN to look at how interactions between jets of particles and gas clouds in the galaxies have changed over the age of the Universe. Some of the well known objects we looked at are: 3C 231, 3C 84, 3C 213.1, plus 3C 273 (quasar located in the constellation Virgo) which you can see with amateur telescopes.

Question: When did you develop interest in Astronomy and what were your initial projects?

Ans: Well, my grandfather is an amateur astronomer, so I guess my first bit of astronomy was seeing Halley’s Comet through a telescope when I was 2 years old. But I never really considered a career in astronomy until I was studying physics for my bachelor’s degree. I decided to take a year off from school, to spend 6 months doing research for a professor, and 6 months working for a company, to decide if I wanted to go on to graduate school or get a job. My advisor at the time (David Axon) is an astronomer. He pointed me towards another astronomer at RIT (Chris O’Dea), and I spent 6 months working for him, on the survey of radio galaxies with Hubble. I decided I liked that so much I didn’t do the 6 months of working for a company, and applied to grad school in astronomy.

Question: currently working on AGN, what do you plan to do next? What after AGN, LIRGs?

Ans: My main focus right now is the LIRGs and the work with the GOALS team. But I am hoping to continue doing both AGN and LIRGs. There is some overlap between them (many AGNs are LIRGs). The most exciting thing recently is certainly the observations at the GMRT. It was a great trip and I also got great data. I think my project can make great use of it and I am hoping to be back again for more observations. But, I think there’s enough we don’t know to keep me busy for a lifetime.

ek tha Tiger


Ek Tha Tiger theatrical poster: YashRaj Films

यश-राज फिल्म्सने बर्‍याच नामवंत नायक, नायिकांना सोबत घेवून चित्रपट बनविले आणि त्यातील बरेच गाजलेसुध्दा. गेल्या चार दशकांमधे यश-राज फिल्म्सने कित्येक नवीन कलाकारांना आपल्या बॅनरमुळे नावारुपास आणले, जे आधीच मोठे स्टार होते, त्यांच्या ’स्टारडम’मधे अजुन भर घातली. बॉलीवुडचा प्रसिध्द अभिनेता सलमान खान याने पहिल्यांदा यश-राज बरोबर ’एक था टायगर’ या चित्रपटात काम केले आहे. सलमानने गेले काही चित्रपट अक्षरश: स्वत:च्या जीवावर यशस्वी करुन दखवले आहेत, पण यावेळेस मात्र असे काही घडले नाही.

शेणॉय (गिरीश कर्नाड – मी पहिल्यांदा यांचे काम पाहीले.) हे RAW मधे ऑफिसर असतात आणि त्यांचा आवडता माणुस टायगर (सलमान खान) हा भारताचा गुप्तहेर असतो. देशा-विदेशात कामगिरीसाठी शेणॉय टायगरला पाठवत असतात. निर्णय घेताना बुध्दीचा वापर करावा, हृदयाचा नाही (हे प्रत्येक चित्रपटांत असते) अशी शिकवण शेणॉयनी गुप्तहेरांना दिलेली असते. एके दिवशी शेणॉय टायगरला सांगतात की त्यांनी कामाच्या जवाबदारीमुळे प्रेमाला तिलांजली दिली. त्या काही प्रसंगात कळते कि टायगर एकटा रहात असतो. परदेशात जिथे जिथे कामगिरीवर जाईल तिथे हणामारी करुन शत्रुला जिवानिशी मारुन टाकत असतो. (इथे बाष्कळ अ‍ॅक्शन सीन बघायला मिळतात.) घरी आला कि, त्याच्या आजुबाजुला रहणार्‍या सगळ्या महिला त्याच्यावर लट्टु असतात. (इथे थोडेफार हसायला मिळते.)

आयर्लंडच्या एका महाविद्यालयात एक निवृत्त भारतीय शास्त्रज्ञ (रोशन सेठ – भारत एक खोज मधले!) काम करत असतात. त्यांच्याकडुन क्षेपणास्त्रांची माहिती चोरीला (कि विक्रीला यात मला confusion आहे.) जाणार असल्याची माहिती मिळाल्यावर टायगर तिथे जातो. शास्त्रज्ञच्या घरी काम करणार्‍या झोयाशी (कॅटरीना) ओळख झाल्यावर सलमान डायरेक्ट तिच्या प्रेमात पडतो! टायगरचा साथीदार गोपी (रणवीर शोरे) त्याला वारंवार कामात लक्ष दे असे सांगत असतो. इथे काही विनोदी प्रसंग आहेत. पण हसायला येता नाही कारण ऑलरेडी हे प्रसंग प्रोमो मधे रीलीज केलेत! (yes #Facepalm) प्रेमात एक-दोन गाणी येउन जातात. एका रोमॅंटीक सीन मधे टायगर झोयाला उल्का दाखवतो! (तेही चंद्र दिसत असताना! हा “विनोद” खगोल-अभ्यासकांना नक्की आवडेल :D )

मध्यंतरापर्यंत गोष्ट थोडीतरी चांगली आहे, पण नंतर ’कायच्या काय’ होवुन जाते. झोया पाकीस्तानच्या ISI ची एजंट असते. ती गुप्त संदेश पाठवुन टायगरला इस्तंबुल येथे होणार्‍या आंतराष्ट्रीय बैठकीस बोलावुन घेते. तिथे ते एकमेकांना आपल्या प्रेमाची कबुली देतात पण समाज आणि RAW, ISI मान्यता देणार नाही म्हणुन कोणालाही न सांगता तिथुन पळुन जातात. मग शेणॉय आणि ISI ची लोक त्यांचा पाठलाग करु लागतात. नायक-नायिकेची जोडी देशाटन करत फिरते आणि सिनेमा संपतो. like ” and they lived happily ever after” (होय, खरच संपतो एकदाचा!)

शेवटी शेवटी एका पाठोपाठ एक Action प्रसंग येतात. विनोदाला जेवढे हसु येत नाही तेवढे serious action scence ला हसु येते. काही गोष्टी खुप unrealistic आहेत झोया आणि टायगर प्रत्येकी ४-५ गुडांना/पोलिसांना बेदम मारतात. हणामारी करताना एका इमारतीवरुन दुसर्‍या इमारतीवर उड्या मारत फिरतात. भारतातल्या गोपीला जसे काही परदेशातले रस्ते माहित असतात म्हणुन तो कार चालवतो. झोयाला विमान उडवता येत असते. टायगरला गोळी लागलेली असताना तो बाईक चालवत उडणारे विमान पकडतो! (this one is epic #Fail) चित्रपटातले बरेच प्रसंग, डायलॉग अक्षरश: predictable आहेत. e.g. (डायलॉग – जिंदा या मुर्दा । प्रसंग – टायगर झोयाला गोळी मारत नाही, शेणॉय टायगरला हृदयापासुन शुभेच्छा देतात आणि इतर अनेक.)

शेवट वाईट केला आहे. सलमानची विशेष काहीच जादु नाही. कॅटरीनाची हिंदी जरी त्रास देत नसली तरी अभिनय ठिकठाकच आहे. रणवीर आणि कर्नाड हे मस्त अभिनेते आहेत.  गाणी विनाकारण येतात. युरेशीयातील आणि इतर काही ठिकाणी  चित्रीकरण झाल्यामुळे लोकेशन्स छान आहेत. (Surprise) सध्द्या सारखे वाजणारे माशाल्ला हे गाणे चित्रपटात नाहीचे. एकुणच कबीर खान दिग्दर्शीत ’एक था टायगर’ जाम बोर आहे. तरी सुध्दा ७५ कोटी खर्च करुन बनविलेल्या या सिनेमाने पहिल्याच दिवशी ३१.२५ कोटी (विकीपेडियाची माहिती) कमावले आहेत!!!

नवीन परग्रहाचा शोध

नासाच्या स्पिट्झर अवकाश दुर्बीणीचा वापर करून खगोलशास्त्रज्ञांनी एका नवीन ग्रहाचा शोध लावल्याचे मानले जात आहे. परग्रह म्हणजे आपला सूर्याव्यतिरीक्त इतर तार्‍याभोवती फिरणारा ग्रह. UCF-1.01 असे नाव देण्यात आलेला हा परग्रह आपल्या सूर्यमालेपासून ३३ प्रकाशवर्षे दूर असून आणि याचा आकार पृथ्वीच्या दोन तृतीयांश आहे. विषेश म्हणजे हा पृथ्वीपेक्षा लहान असलेला सर्वात जवळचा ग्रह असण्याची शक्यता वर्तवली आहे.

केवीन स्टिवेनस्टन यांच्या नेतृत्वाखाली लिहिलेल्या शोधनिबंधास अ‍ॅस्ट्रोफिजीकल जर्नलने मान्यता दिली आहे. “प्रचंड उष्ण आणि खुप जवळ असलेल्या या ग्रहाची आम्हाला चांगली निरीक्षणे मिळाली. अशा लहान आणि जवळच्या ग्रहांचा शोध लावल्याने भविष्यात आपलल्या त्यांच्या वैशिष्टयांची माहिती करुन घेता येइल.” असे सेंट्रल फ्लोरीडा विद्यापिठाशी संलग्नीत केवीन स्टिवेनस्टन म्हणाले.

अवकाशातील तारे, आकाशगगांनी उत्सर्जीत केलेल्या ३ ते १८० मायक्रोमीटर मधील इंफ्रारेड किरणांचा अभ्यास करण्यासाठी स्पिट्झर दुर्बीणीचा वापर केला जातो. पृथ्वीप्रमाणेच हि दुर्बिण आवकाशात सूर्याभोवती फिरते ( हेलीओसेंट्रिक कक्षा ). या दुर्बिणीचा उपयोग आधी लागलेल्या परग्रहांवर संशोधन करण्यासाठी स्टिवेनस्टन आणि त्यांचे सहकारी (red-dwarf) M dwarfs श्रेणीतील GJ 436 या तार्‍याभोवती फिरणार्‍या GJ 436b या नेपच्युन एवढ्या परग्रहाचा अभ्यास करीत होते. त्यावेळेस तार्‍याच्या इंफ्रारेड किरणांची प्रकाशमानता कमी-जास्त होण्याच्या नोंदी मिळाल्या. याचे कारण GJ 436b हा ग्रह नव्हता. प्रकाशातील फरक हा नियमित असल्याने तेथे इतर ग्रह असल्याची शक्यता वर्तवण्यात आली. UCF-1.01 आणि UCF-1.02 असे तेथील दोन ग्रहांना नावे देण्यात आली असून या शोधास पुष्टी मिळाल्यास त्यांना अनुक्रमे GJ 436c and GJ 436d अशी नावे देण्यात येइल. तरी यातील UCF-1.02 ग्रहाची पुरेशी माहिती शास्त्रज्ञांना अजुन मिळालेली नाही.

तार्‍याभोवती ग्रहाच्या परिभ्रमणामुळे निरिक्षकाला तार्‍याच्या प्रकाशमानतेत नियमित कमी-जास्तपणा जाणवतो. यास ग्रहणाचा एक प्रकार म्हणजे अधिक्रमण असे म्हणतात. नवीन ग्रहांचा शोध अशा अधिक्रमणांच्या निरिक्षांणांतून मिळालेल्या माहितीमुळे लागतो. अधिक्रमणाला लागणारा वेळ, प्रकाशाचे कमी झालेले प्रमाण यावरुन ग्रहाची प्राथमिक माहिती काढता येते, जसे की आकारमान, कक्षा. जर ग्रह आकारने लहान असेल आणि तार्‍याच्य जवळून परिभ्रमण करीत असेल, तर निरिक्षणे मिळणे फार जिकरीचे होते. नासाचा केप्लर मिशन हा उपक्रम परग्रहांचा शोध लावण्यासाठी प्रसिद्ध आहे. केप्लर अवकाश दुर्बीणीसुधा अधिक्रमणांचीच निरिक्षणे घेते. या उपक्रमात १८०० तार्‍यांची गणना केली आहे कि ज्यांना उपग्रह आहेत आणि यापैकी फक्त ३ तार्‍यांच्या ग्रहांचा  पृथ्वीच्या आकारमानाशी साधर्म्य आहे.

UCF-1.01 या उपग्रहाचा व्यास ८४०० कि.मी. आहे तर तेथील तापमान सुमारे ६०० अंश सेल्सिअस इतके प्रचंड आहे. हा ग्रह मुख्य तार्‍याच्या इतक्या जवळून फिरतो की त्याची एक फेरी पुर्ण होण्यास लागणारा वेळ म्हणजे परिभ्रमण काळ १.४ दिवस (पृथ्वीचा दिवस) इतका आहे.  उष्णतेमुळे भाजुन निघालेल्या या लहान ग्रहावर कधी काळी जर वतावरण असेल तर ते एव्हाना नक्कीच नष्ट झाले असणार आहे. या ग्रहांच्या शोधाची पुष्टी करण्यासठी त्यांची घनता मोजणे आवश्यक आहे परंतु अतिसंवेदनशील साधनांचा वापर करुनही मोजणी करणे सध्या अशक्य आहे कारण त्याची घनता फार कमी – संभवतः पृथ्वीच्या एक तृतीयांश आहे.

ग्रहावर जीव असण्याची शक्यता ही त्याच्या आणि तार्‍याच्या अंतरवर अवलंबुन असते. तार्‍यापासुन काही ठरावीक अंतरच्या क्षेत्राला habitable zone म्हणतात. ग्रह या zone असला तरच त्यावर जीवसृष्टी तयार होण्यास पुरक वातावरण, तापमान आणि पाणी असण्याची संभावना असते.

आपला सुर्य G-type तारा आहे आणि पृथ्वी habitable zone मधे आहे. GJ 436 हा तारा M dwarfs या श्रेणीतील आहे. या तार्‍यांची घनता सुर्याच्या घनते पेक्षा ८ टक्के ते ५० ट्क्के इतकी असते. अशा प्रकारचे तारे फार अंधुक असतात, साध्या डोळ्यांना न दिसणारे आणि आपल्या आकाशगंगेत त्यांची व्याप्ती ७० टक्के आहे. परजीवांच्या संशोधनाचा विचार करता अशा तार्‍याचा अभ्यास तुलनेने कमी केला जातो कारण यांचा habitable zone तुलनेने फ़ार अरुद असतो. हा zone तार्‍याच्या फ़ार जवळ असल्या कारण्याने धोकादायक radiation चा प्रश्न असतो.

आतापर्यंत habitable zone मधे असलेले क्त ५४ ग्रह सापड्ले आहेत.

 Paper Publication http://arxiv.org/abs/1207.4245

News release http://www.spitzer.caltech.edu/news/1441-ssc2012-11-Spitzer-Finds-Possible-Exoplanet-Smaller-than-Earth

M dwarf the search for life is on. Interview