## Saturday, November 26, 2016

### How Zero G Planes Fly???

 Airbus 300
If you ever wished for weightlessness like astronauts, here is an easy way to feel it... Get into a Zero Gravity Plane. Zero Gravity Planes performs parabolic arcs to create a weightless environment allowing you to float, flip and soar as if you were in space. Parabolic flight or zero gravity flight is an aerobatic maneuver performed by an airplane that enables brief (15-25 sec) periods of near-zero-gravity. Astronauts feel weightless because their space shuttle is in a state of continuous free fall to the earth. If an astronaut on the space station drops a pen, it doesn't look like it's falling. That's because they're all falling together: the pen, the astronaut and the station. But they're not falling towards Earth, they're falling around it. Because they're all falling at the same rate, objects inside of the station appear to float in a state we call "zero gravity" (0g), or more accurately microgravity (1x10-6g). Objects in a state of free fall are said to be weightless. The object's mass is the same, but it would mark "0" on a scale. Eventhough your mass stays the same, weight varies depending on whether you are on Earth, the moon or in orbit. Gravitational force is a measurement of the acceleration due to gravity that causes weight. Zero gravity is a condition of weightlessness referring to the absence of a gravitational force (g-force or Gs).
Because of air resistance, objects in Earth's atmosphere only travel in arcs that approximate a true parabola. In case of a true parabolic arc in air, the only accelerative force is gravity pulling in a vertical direction which means horizontal velocity remains constant. So in order for passengers in the plane to experience a free fall safely, the aeroplane must climb at a steep angle, level off, and then dive, creating a parabolic arc, also called a Keplerian Trajectory or free-fall path. I.e. In parabolic flight, any plane flies in a parabolic arc involving three stages, an horizontal phase in which the gravitational force is the same as on Earth, 1g. A second phase which goes from 0º to 45º where the passengers weight increase up to 1.8g. Finally, for angles greater than 45º together with the adequate speed, the 0g effect is achieved.
During an entry phase, flight flies horizontally at an altitude of 24,000 feet, then the nose of the plane is lifted upward to an angle of about 45 degrees(nose high) until the plane reaches around 32,000 feet where the engines are pulled back to idle. This moment is called initiation with aircraft entering parabolic phase. As the plane goes over the top of the arc, the centrifugal force exerted on the plane and everything in it cancels out the gravitational force pulling downwards, making you feel as if you are weightless. At this point everything in the plane, experience a sense of weightlessness for the next 20-30 seconds. After these few seconds, at approximately 30 degrees (nose low) a gentle pull-out is started which allows the passengers to stabilize on the aircraft floor, thus exiting from parabola and regaining the initial level of flight.. The maneuver is then repeated almost to 15 times. Passengers experience a pull of nearly twice that of gravity (1.8 Gs) during the downward trajectory, at the bottom of the path, as well as the upward climb of the flight, which takes around 65 seconds to complete.
The first zero gravity flights were proposed in 1949 by the German aerospace engineer Fritz Haber and the German physicist Heinz Haber . Both had been brought to the US after World War II as part of Operation Paperclip. They proposed parabolic flights as a way of simulating weightlessness. Parabolic flights are also used to examine the effects of weightlessness on a living organism. While humans are by far the most common passengers, non-human animals have occasionally been involved in experiments, including a notable experiment on how weightlessness affected a domestic cat's righting reflex and a pigeon's attempts to navigate in a weightless state.
Zero gravity flights are the only way to test microgravity with humans without going through lengthy astronaut-training and flights to the International Space Station. Parabolic flights are extremely safe and have been flown for the past 50 years by NASA, The Russian Space Program and European Space Agency. For this reason, parabolic flights are often used to validate space instruments and train astronauts before spaceflight. Zero gravity aircraft are also used for expensive leisure pursuits and weightlessness experiments by NASA and also used in the entertainment industry.
Along with the experience of floating, passengers will also experience nausea due to motion sickness during the journey, that’s why such flights got nickname of “vomit comet”. The 1.8g assents has a strong effect on the fluids in your ears which affect your sense of balance, and that’s what makes you nauseous. Zero Gravity Research Facility in Brook Park, Ohio,US is the country’s main base for microgravity research and the world’s largest facility of its kind. The centre is used to develop and test equipment designed for flights on board the Space Shuttle and International Space Station (ISS). In late 2004, Zero Gravity Corporation(ZERO-G) the became the first company in the United States to offer zero-g flights to the general public.
If you want to experience a zero-gravity flight, you can book a trip on G-FORCE-ONE, a modified Boeing 727-200, through the ZERO-G Web site or at your local Sharper Image store for (\$4,950 - £3,950) per person. It's possible to book yourself on to a zero gravity flight from the Orlando Sanford International Airport and Fort Lauderdale International Airport in Florida, as well as from McCarran International Airport in Las Vegas and the Oakland International Airport in Oakland, California. Flights are also offered in New York and Los Angeles, as well as in Austin and Houston in Texas. The package includes your flight, unique merchandise and a post-flight celebration (or, depending on your point of view, a wake for your temporary dramatic weight loss). Passengers must be at least 15 years old if unaccompanied, or 12 if flying with a parent or guardian.
The G-Force One aircraft can also offer the experience of lunar gravity (the gravitational force of the Moon where you’ll weigh around a sixth of your weight on Earth) or Martian gravity (the level of gravity on Mars where your weight is around a third of that on Earth) by flying a larger arc at the top of the parabolic path This is when you can jump around the aircraft like you are walking on the moon/Mars. Is’t it awesome.??
I think a zero-gravity flight is the first step towards space travel, so be weightless and get ready for your sub-orbital flight...

## Sunday, August 28, 2016

### Meet the Longest-Lasting Battery in the World....

Would you like to live a world in which you never have to charge your phone again. May be scientists inspired by this venerable scientific curiosity could help you... In the foyer of the Clarendon Laboratory in the University of Oxford lies an electric bell named as Oxford Electric Bell or Clarendon Dry Pile which has been ringing continuously since 176 years and has been recognised as the longest-lasting battery in the world.
 Oxford Electric Bell or Clarendon Dry Pile
Termed as one of the world’s oldest experiments, still no one knows exactly why it’s lasted so long. The only way to find out what is inside for sure is when the battery ultimately dies as opening the device could potentially ruin an experiment to see how long it will last. Therefore researchers will have to wait until either the battery finally loses its charge or else the ringing mechanism breaks on its own from old age.
Oxford Electric Bell made by Watkin and Hill, an instrument-making firm in London, and purchased by Robert Walker, a professor at Oxford was first displayed in 1840, says a handwritten note attested by his grandson on the bell. Some accounts at Oxford University says the bell could have been started even earlier, in 1825. The Guinness Book of World Records has named its power source the "world's most durable battery."
It’s a dry pile battery, which is one of the first electric batteries invented by a Giuseppe Zamboni during 1800s. They use alternating discs of silver, zinc, sulfur, and other materials to generate low currents of electricity. Being a dry pile battery, it’s got a paste inside with a minimum amount of water needed for the electrolyte to work. The battery is covered with an insulating layer of molten sulphur, in order to protect against atmospheric damage (i.e. moisture),connected in series at their lower ends to two bells. It’s theorized that the interior contains thousands of discs made of manganese dioxide and zinc. Between the bells is suspended a metal sphere or ‘clapper’ about 4mm in diameter which is attracted alternately by the bells and transfers charge from one to the other due to an electrostatic force, maintained by the ringing of the bells. The process is repeated over again and again. The frequency of its oscillation is about 2Hz and so far the bell would have rung roughly 10 billion times, and probably more than that, calculations from the university suggest.
High humidity can cause the clapper’s movement to slow and even stop, but when the humidity drops the bell can begin again without external intervention. As the clapper strikes and rings one bell, the corresponding dry pile charges and electrostatically repels it. The clapper then swings toward the other bell, and the same thing happens.
While it needs high voltage to create motion, the sphere only carries a small amount of electricity to the alternating dry piles. Because there’s just little bits of energy being discharged through the process, the drain on the battery is very less, and this may be the reason for its long run..
Presently the voltage left in the battery is so low that the human ear can't actually hear the ringing. Instead, the clapper oscillates back and forth between the bell constantly. A former researcher at the Clarendon Laboratory, A. J. Croft, described the apparatus in a 1984 paper for the European Journal of Physics. According to him, the battery pulls 1 nanoAmp each time it oscillates between the bell’s sides, which is an remarkably a low amount of current. But the voltage between the bells is 2 Kilovolts, according to guest host, Sally Le Page‏, in the latest video on TOM SCOTT’s you tube channel.
A similar type of dry pile batteries were used to power the infrared telescopes during World War II, because a portable, low-current electricity source was necessary. Croft further wrote that an Oxford physicist, inspired by the bell, is working to make a similar one to boost up the present era telescopes.
I think we're probably not going to build a better battery than this at this point. The bell has been ringing nonstop under the glass since 18oos and no one can tell when it will stop, leaving behind a mystery to be solved… The lifetime of this battery should be incredible, and if scientists are correct, it should work for thousands of years and outlive us..

## Monday, July 11, 2016

### Is Fashion Jewellery poisonous???

Beware all!!! especially  people who buy low-cost jewelry from popular fashion chains. New research has found toxic levels of cadmium, a heavy metal that can be particularly toxic for kids. Simply wearing jewelry does not cause harm, but sucking, chewing on or swallowing it can cause many harmful effects to children's bodies, including death. Also Children's bodies more readily absorb the toxic metal.  Cadmium is a known carcinogen, which can lead to kidney failure, bone loss and other complications in those who are chronically exposed over time.
Jewellery that is painted or has a top coating does not make it safer for children: the coating can be chewed or worn off. Earlier lead was instead of cadmium. One of the big challenges with lead is that it has a sweet taste, which can encourage kids to put it in their mouths. It is inexpensive, so it is made with the cheapest materials available. Also it's easy to melt so it makes nice heavy pieces of jewelry. Lead, cadmium, chromium, mercury and arsenic among other highly toxic chemicals, can cause health issues like acute allergies, birth defects, impaired learning, liver toxicity and cancer.
Children’s jewelry is intended to attract, appeal to a child. In the production of art/children’s jewelry, some manufacturers use lead as a base metal, often combined with tin, since it produces an alloy that is easy to work with as well as easy for shaping. Besides making it look heavy it is also cheap. In the process of manufacturing, lead gets coated on the jewellery. Even short-term exposure to lead may cause long-term adversarial impact on children’s health. Adding to the grave situation, manufacturers coat jewelry items with bright colours to attract children, while most of these colours have organo-metallic compounds and metals in them, loosely bound to the surface, which can leach easily.
This type of jewelry is most often worn by the young, most of them children in the age group between 3 to 16 years, who are very sensitive to lead exposures, since it is a critical time for neurological development. Children (below 6 years) are recognised as the most susceptible to lead exposure even at low levels. Pregnant women are the second most vulnerable group. Lead also crosses the placenta and reaches the developing fetus. Absorbed lead is rapidly taken up by blood and soft tissue, followed by a slower redistribution to bone. Bone accumulates lead during much of the human life span and may serve as an endogenous source of lead that may be released slowly over many years after the exposure stops.
It has also been established medically worldwide, that lead is a potent neurotoxin causing irreversible harms to human health and environment. While lead levels are regulated in children’s toys cadmium is not, though cadmium is toxic just the same. Lead is also found in Antique painted furniture (including cribs), buttons, hair ornaments, Old painted toys, Lead paint on kitchen utensils, Imported painted toys. Also toys made of plastics (both PVC and non PVC), contain lead and cadmium.

Main danger lies because of its advantage of being cheap. cheapness of  fashion jewelry or costume jewelry makes
• These items appeal to those with a small budget.
• These items often fall apart potentially leaving small parts laying around in junk drawers or on the floor to tempt a toddler.
• The impact of even the smallest traces of lead on brain development in children includes irreversible learning and developmental problems leading to to lower IQ scores, delayed learning and shorter attention spans.
•  The EPA has listed lead as a probable human carcinogen

• Cadmium is classified as a known human carcinogen, associated with lung and prostate cancer
• Cadmium exposure is associated in animal studies with developmental effects, including possible decreases in birth weight, delayed sensory-motor development, hormonal effects, and altered behavior.
• Exposure to cadmium can result in bone loss and increased blood pressure.
• Acute toxicity from ingestion of high levels of cadmium can result in abdominal pain, nausea, iting and death.
• Acute toxicity from inhalation of high levels of cadmium can result in symptoms similar to metal fume fever and severe gastroenteritis from high levels of cadmium ingestion.
• Cadmium is extremely toxic metal, even dangerous than lead, and very hard to detect using house hold method similar to lead, most popular method to detect Cadmium is  X-ray Fluorescence Spectrometry (XRF).

What we can do:
1. Inspect your children's jewelry. Items made with a high percentage of lead are heavy for their size.
2. If you are concerned that a children's jewelry item may contain lead or cadmium throw it away in your regular household waste.
3. Do not give young children adult jewelry to wear or play with; it may contain lead or cadmium.
4. Don't let kids suck or chew on any jewelry.
6. A child who swallows jewelry containing lead or cadmium is at high risk of developing serious and potentially life-threatening health effects. Contact an emergency medical service immediately.
7.  Check for product recalls by contacting the retailer or manufacturer.
8. Be choosy about your purchases for birthday parties for your children's friends. Stay away from cheap jewelry and jewelry making kits unless you can, without a doubt, verify the lead content.
As all know, prevention is better than cure. In case of low-cost jewelry, which might make our outfits look better for a very low price; they might also slowly poisoning us. Therefore some caution is required. The more educated and demanding the public is, the more pressure will be on the manufacturers to adhere to strict standards regarding toxic substances in jewelry and jewelry findings. So be bold, its better late than never....

## Sunday, July 10, 2016

### Hairware

Don’t be surprised when a woman absentmindedly strokes her hair in public. She might be actually activating any one of her smartphone apps… Though sounds unlikely, it is possible now. A Brazilian inventor, Katia Vega, has developed an innovative new wearable gadget that allows users to discreetly control electronic devices by just stroking their hair.

The new Beauty Technology Prototype known as Hairware connects chemically metalized hair extensions to a microcontroller turning it into an input device for triggering different objects. It is actually a switch woven into hair extensions that can be used discreetly to activate apps. The extensions can be used as a wireless input device for mobile phones, and can be programmed to open applications, send preset messages, or broadcast a person’s location. According to inventor, a woman who is feeling threatened could use Hairware to broadcast her location, or activate a preset emergency text message, without visibly using the phone.

Hairware acts as a capacitive touch sensor that detects touch variations on hair and uses machine learning algorithms in order to recognize user’s intention. An Arduino microcontroller and a bluetooth radio in a hairclip provide the system's intelligence and connectivity, with an algorithm, which avoids accidental activation, learning over time when the user has intended to trigger an action.

Normally, while someone touches her own hair, unconsciously she is bringing comfort to herself and at the same time is emitting a non-verbal message decodable by an observer. The touch of a user’s fingers changes the hair’s ability to store an electric charge ever so slightly. This hair's ability can be used to set controls. For example, stroking it once activates one app and touching twice launches another. And because stroking our hair is a natural human activity, no one need know what the user is doing.

Hairware brings the opportunity to make conscious use of unconscious auto-contact behaviour. I.e. touching her hair is an unconscious action that woman do for getting more comfort. Using Hairware, they will replay this act on her hair but she is not just emitting a message to an observer, she would be triggering an object, creating a concealed interface to different devices.

The main advantages are interesting… No one knows that the user is wearing a device which can make possible concealed interactions. Also no one knows that the user is triggering an event and that the body surface is being used as a novel wearable interface by transforming materials into devices that look like body parts. In future, it can be used by intelligence agencies to gain secretive information, such as taking a photo or recording a conversation.

As hair is generally a focus of women, Hairware could be used as a tool for protection against risky situations. In this way, it could be used as an alarm device sending messages with the user’s location. It can be used in personal security, particularly for women, foresees potential applications for intelligence agencies.

As the video shows, this technology can be used to record a conversation, send location, or even take a selfie. The possibilities are endless here.

It adopts a seamless looking approach to wearable computing. It implements a wearable aspect to an existing part of the body in order to integrate technology with organic matter. Wearing a smart watch is one thing, but having technology as a part of your body such as skin or hair may require a little more convincing(I think). As it is removable and self-contained, there is no complicated setup required. This is something that could be useful in every field. But don’t get too excited to purchase this product for your daughter, sister, or mom as it's still in the development phase. I hope Vega soon commercialize the product .

Excuse me Men, here is some happy news for you too…Vega is planning to extend Hairware and turn beards into active app controllers too.

## Friday, July 8, 2016

### Fall of floating Idol of temple of konark mystery

Did you know the sun temple of konark in india is one of the unique temples around the world???  Yes, it is … because of artistic magnificence and engineering dexterity. The name Konark is derived from the words Kona – Corner and Arka – Sun; it is situated on the north eastern corner of Puri or the Chakrakshetra. The mythological reference is that Lord Krishna's son Sambawas cured of leprosy by Sun god and he built the temple in the honour of Surya.Another story goes like this : Sun Temple of Konark, once contained a giant lodestone magnet, which held the entire edifice together by its force. This was so powerful that it used to disrupt the magnetic compass of the ships going through that route.The Portuguese removed the main magnet or lodestone as it was the cause of the destruction of lot of their ships and destroyed it. This lead to the collapse of most of the temple structure.
The temple was constructed from oxidized and weathered ferruginous sandstone by King Narasimhadeva I of the Eastern Ganga Dynasty.. The temple is built in Kalinga style of Architecture in east to west direction in such a way that the rays of the rising sun fall on the idol of the Solar diety in the main sanctum. It took 12 years its completion. Works started in 1245 AD and completed in 1256 AD. It has been declared a world heritage site by UNESCO in 1984.
It’s known as “Black Pagoda” due to its dark color and used as a navigational landmark by ancient sailors to Odisha. The black colour of Sun Temple could be due to the accumulation of moss, lichen and other fungal growth which turned the surface of the temple into black colour. Its magnetic power drew ships into the shore and caused shipwrecks in the past.
The large structure of Konark Temple seen today is actually the entrance of the main temple. The main temple which enshrined the presiding deity has fallen off and only the remains can be seen. The temple is erected in the form of a huge chariot of Surya, the sun god. This chariot is placed on twelve pairs of splendidly carved wheels and drawn by seven dynamic horses. According to one saying, these 12 pair of wheels symbolizes 24 hours in a day, while the other say, these wheels represent 12 months of the year. Seven days of the week are said to be the representation of seven horses. These wheels are not ordinary wheels but are inspiration for the modern time watches. The spokes of the wheels create a sundial and one can calculate the precise time of the day by just looking at the shadow cast by these spokes.
On either side of the entrance of the Konark Sun temple has two huge lions. Each lion is shown crushing an elephant. Beneath each elephant lies the human body. Lion represents pride and elephant represents money. What a wonderful thought…!!!! It depicts problems faced by Human beings.
Around the base of the temple there are images of animals, foliage, warriors on horses and other interesting structures. On the walls and roof of the temple beautiful erotic figures are carved. Infront of the temple there is natya mandir (dancing hall) where the temple dancers used to perform dances in homage to the Sun god. There are three images of the Sun God, positioned to catch the rays of the sun at dawn (happy and cheerful), at noon(Grim), and sunset(with a tired looking horse)Every day, the Sun’s rays would reach the Nata Mandir from the coast and reflects from the diamond placed at the center of the idol. The pillars have been aligned to ensure the sun rays pass through without an obstruction during the Uttarayana and the Dakshinayana ! This is another angle of alignment. The geometric perfection is amazing !
Beyond the Natya Mandir, stands the 128 feet high Jaganmohana, the Audience Hall or the front porch.
The Uniqueness of the Sun Temple at Konark lies in the fact that it was built using the concept of magnets. The peak of the temple was said to be a giant 52 ton magnet. A massive magnet was placed at the temple top and each two stones of the temple are inserting by iron plates. The statue of the Sun inside the temple was said to be floating free in air based on the unique arrangements of the main magnet and the reinforced magnets around the temple walls. Between every two stone pieces in the temple there lies an iron plate.
Sun temple of Konark is a masterpiece of Orissa's medieval architecture. The size of the temple is awe-inspiring ; the Original structure was over 220 feet in highKonark is an exceptional mixture of marvelous temple architecture, heritage, exotic beach and salient natural beauty. It showcases planned execution and engineering brilliance of our ancestors. It was, or I may say is, the most beautiful temple ever built for the Sun God which got destroyed over time.

## Thursday, July 7, 2016

### Six Degrees Of Separation

 Six Degrees of Separation

Six degrees of separation is the theory that anyone on the planet can be connected to any other person on the planet through a chain of acquaintances that has no more than five intermediaries. The theory was first proposed in 1929 by the Hungarian writer Frigyes Karinthy in a short story called "Chains." Most people have heard of the "six degrees of separation" theory -- the idea that everyone in the world is separated from everyone else by six links. Is it a myth or a fact of life?

A 'degree of separation' is a measure of social distance between people. You are one degree away from everyone you know, two degrees away from everyone they know, and so on. The concept was popularised by John Guare's 1990 play, Six Degrees of Separation, which was turned into a film starring Will Smith, Stockard Channing, Donald Sutherland and Ian McKellen.

Starting from Stanley Millgram in 1967, many people have experimented on the topic and the fight still continues. that involved sending folders or letters from a group of people in one part of the country to a specific person they didn't know in another part of the country. The people were told to get the material to someone who might know someone that would know the individual.  In fact, he found that the letters or folders took, on average, between five and six connections to reach the intended recipient. Though the average number of links was five or six, the majority of the connections ranged from two to 10 links. In spite of being challenged by Judith S.KleinfeldMilgram's work was revolutionary as it paved way to more discussion and understanding.

 Six degrees of separation
In 2003, Duncan Watts and colleagues at Columbia University, asked emailers to try and forward a message to one of 18 target people in 13 different countries, going via their friends and acquaintances. All together more than 60,000 people took part. They found that successful chains were completed in between 5 and 7 steps, similar to Milgram’s results. Leskovec and Horvitz for Mcrosoft in 2006, analysed data from 30 billion instant messages sent around the world and found average number between senders is a slightly bigger 6.6.  In august 15, 2015, Derek Muller of Veritasium has come up with a  a scientific explanation which makes it  easier to maintain connections with distant acquaintances than ever before. For example, Muller explained that in 2011 Facebook analysed their data and found that 92 percent of all their users were connected through just five steps. Moreover Facebook, the online social network, has a 'six degrees' application to test the theory through the connections of Facebook users. That may reduce a degree or two: Barack Obama already has well over a million Facebook friends.

A site called Six Degrees, launched in 1997, is considered  to be the first social networking site and the precursor of sites like facebook which have effectively lowered the number of intermediaries in the chain, arguably to almost zero.  Remember that we are not talking about the chances of connection between two people taken at random. We are talking about the chances of meeting a person who knows someone from our past. Over a lifetime, these chances are high, especially for educated people who travel in similar networks. In the digital age, the world has shrunk more, turning us into a "global village."  So lets test this to know a fact or myth!!!!!

You can definitely test theory yourself; initially I also had some doubt about the credibility of this theory as everyone else. Then I did a experiment by sending E-mail to some of my school friends,  reality is I even did not know the E-mail address of my school friends, I just know their name and place where they use to live around 20 years back. In my mail, I explained their physical appearance based on my assumption.  And I requested one of my nephews to pass this mail to my school friend whom I explained in the mail or someone who might know my school friend. I’m really surprised and happy that I can able to contact 7 school friends out of 10. Any way 3 of my school friends did not reply or they did not get my message.  And some of my friends got my message from multiple sources. In my experiment lowest chain in 4 and highest is 11.

Any way I am happy with my experiment because it helped me to understand how close we are even when we did not know. It really helped me to establish connection with my old friends, whom I thought I lost connection.  After that I tried to contact individuals in the chain unfortunately most of them did not reply, thinking it’s a Spam message.....

I request you to please try from your side and please share your experience....  Please note that it will take some time so be patient, as still I am waiting for my unconnected 3 friends....

## Thursday, June 30, 2016

### The Li-Fi: Internet Revolutioner

Due to the increasing demand for wireless data communication, the available radio spectrum below 10 GHz (cm-wave communication) has become insufficient. The wireless communication industry has responded to this challenge by considering the radio spectrum above 10 GHz (mm-wave communication). The answer to increasing frequency congestion as Internet usage continues to rise across the world is provided by Light-Fidelity (Li-Fi). It’s a very exciting technology that has been on our radar since Professor Harald Hass gave a TED talk on the topic back in 2011.

Light-Fidelity (Li-Fi) is a continuation of the trend to move to higher frequencies in the electromagnetic spectrum. Data is transmitted by modulating the intensity of LED light at nanosecond intervals, too quick to be detected by the human eye. It uses visible light between 400 and 800 THz (780–375 nm) to transmit binary data in the form of light pulses. Actually how it works- Li-Fi uses common household LED (light emitting diodes) lightbulbs to enable data transfer, boasting speeds of up to 224 gigabits per second. Standard LED lightbulbs use a constant current, which emits a constant stream of photons perceived by us as visible light. LEDs are semiconductors so the current and output can be modulated at high speeds, which is picked up via a photodetector device. The optical output is then converted back into an electrical current, which is processed and sent to your device as data. Li-Fi depends on your device being within range of the light being transmitted by your Li-Fi bulb.

 Li-FI Block Diagram

Why we use LEDs specifically? Its because LED bulbs use 85% less energy than incandescent bulbs and last up to 20 times longer. LED lights are natural beam-formers, which makes it easier to create separate uplink and downlink channels, which essentially means more secure internet browsing. Using LEDs as it has both reduced the light consumption as well as heat dissemination. Besides energy-efficiency of LEDs, there is an added benefit for LiFi cellular deployment in that it can build on existing lighting infrastructures.

Due to its shorter range, Li-Fi is more secure than Wi-Fi. Light's inability to penetrate walls makes it potentially secured. Li-Fi lowers the possibility of external sniff and hacking attempts. The visible light spectrum has 10,000 times more bandwidth than radio waves spectrum. Plus, it’s unlicensed and free to use.

Data can be transmitted over the light spectrum, this makes Li-Fi a form of optical wireless communication. Li-Fi uses infra-red and ultra-violet (visible light) waves to communicate data. Infra-red and ultra-violet spectrums can carry more information than radio frequency waves. This is why Li-Fi can achieve greater speeds than Wi-Fi. Li-fi can deliver internet access 100 times faster than traditional wi-fi, offering speeds of up to 1Gbps (gigabit per second). I also believe that the high speed and the large data density could totally change the way we watch television and also will have great impact on satellite communications.

Benefit of using Li-Fi technology in hospitals, nuclear power plants and aircraft cabins is that it does not cause electromagnetic interference.  Li-Fi technology will allow high data connectivity for each air craft passenger at all times. The reduction in cabling requirement also means a lighter aircraft. It is also used in cellular and underwater communications as light can penetrate for large distances unlike radio waves which get absorbed in water, preventing  underwater radio communications.

Since new generation vehicles are coming with LED headlights and taillights and street lights, signage and traffic lights are switching  to energy-efficient LEDs. So, Li-Fi technology can be easily used for vehicle-to-vehicle and vehicle-to-roadside sensor communications for road safety and traffic management system.

On a larger scale, lasers can be used to transmit high rates of data between satellites in space or to dishes on the ground. Such systems can allow military or telecoms information to pass between two towers or from space to the earth.

Limitations
• A major hurdle is that the connection will be lost if a user leaves the room. To have a continuous Li-Fi network inside our house, we will need  lightbulbs in every room to have seamless connectivity.
• Another major issue is that Li-Fi does not work outdoors, meaning that public Li-Fi will not be able to replace public Wi-Fi networks any time soon. When it comes to outdoor use-cases, interference from sunlight prevents one from employing Li-Fi solutions.
• Though Li-Fi is not unidirectional, i.e. it can both transmit and receive data, LEDs can currently only be used to transmit data due to feasibility and cost issues involved, as specially designed ASIC receiver or SoC receivers are required for uplink transmission.
• Opaque obstacles on pathways can affect data transmission
• One of the biggest drawbacks of Li-Fi is that it requires light to be switched on all the time to deliver connectivity.
Li-Fi technology made its way out of laboratories to live trials in 2015. LiFi is a 5G technology which will unlock the Internet-of-Things and in the future, using light bulb as your wireless hotspot. With faster connectivity and data transmission, Li-Fi  promises to be cheaper and more power efficient than existing wireless technologies. It should be remembered that Li-Fi probably won’t replace Wi-Fi altogether, rather, both the technologies will be used simultaneously for a cleaner, greener, brighter tomorrow.