We Know The Speed of Light But What Is The Speed of Dark ?

This question, like many others, centers on a negative concept. There are a few of these running around and it is fairly common to get tripped up by them, but part of the fun in science is when you can apply negative concepts to positive ones, helping us better understand how each facet of the universe work together AND independently. One such negative concept asks: “What is darkness?” “And is there such a thing as the speed of darkness?”

In order to know what the speed of darkness is, or anything else about it, we would have to quantify it. What is it? Well darkness is the absence of light. So darkness isn’t a thing, it is instead a lack of a thing. Therefore questions about characteristic of darkness, which is an absence instead of a presence, become hard to define.

The most correct answer to the question would be that darkness has no speed. In order for something to have speed, it must be able to move relative to other bodies. Since darkness doesn’t actually exist, it cannot move and therefore cannot have a speed. However, since the level of illumination of a given area cannot change at a different rate than the speed of light, you could also equate it as having the speed of light, though less correctly.

I’ll use an example to make my point. Lets say you are in a room which is completely sealed off from the outside world, and nothing can enter it (particularly light). In this room you have a perfect light bulb. It has no warm up or cool down time, when you flip the switch, it instantly starts or stops producing a steady stream of light. In addition to this, let’s say that the walls do not reflect light, but instead completely absorb it. For convenience, let’s make the room round and have the light bulb at the center. Most of this can’t actually be done, but this is still a helpful thought experiment.

Now lets say we suddenly turn off the light bulb. The light will travel at a predictable speed from the bulb, and as it does, it will leave behind it an area without any light at all (meaning the light in the room is receding at the speed of light. Note that the darkness isn’t advancing, but the light is receding. As I’ve said earlier, darkness isn’t actually a thing; therefore, it cannot have a speed.

However the lack of light in our hypothetical room is spreading at the speed of light. Colloquially, this is a minor point. It is however a very important distinction. Darkness doesn’t exist, and therefore cannot spread or move, but light (which obviously does exist) can. And in doing so it can also leave an absence of light, and this absence will grow or shrink at the speed of light.

Since darkness isn’t a tangible thing, it is hard to properly quantify its characteristics. It doesn’t have a speed, but light will always advance or recede at the universal speed limit (186,000 miles per second, or 299,792,458 meters per second).

Source:- http://futurism.com/the-milky-way-lyrids-by-mike-taylor/

Sailing Stones

Sailing Stones

अपने आप में अनोखा
बड़े-बड़े पत्‍थर और रोज अपने आप ही ‌सरकते हुए आगे बढ़ जाए, ये हैरत वाली बात है। लेकिन कैलिफोर्निया के रेसट्रेक पलाया कि ये खासियत है कि वहां के पत्‍थर अपने आप ही खिसकते हैं।

ऐसा क्यों होता है, इस बात ने विज्ञान को भी लंबे समय तक हैरत में रखा। इसके पीछे की सच्चाई जानने के लिए स्रिक्प इंस्टीट्यूट ऑफ ओशियनोग्राफी, युनिवर्सिटी ऑफ कैलिफोर्निया के सैन डियागो के वैज्ञानिकों ने पहल की।

एबीसी डॉटकॉम के मुताबिक इसके लिए उन्होंने सबसे पहले रिचर्ड नॉरिस और जेम्स नॉरिस ने उस रहस्यमयी रास्ते पर जीपीएस डिवाइस लगा दिए और उसको देखना शुय किया। आपको बता दें इस जगह को डेथ वैली या फिर सेलिंग स्टोन नाम से भी जाना जाता है।

निकली सच्चाई
उन्होंने सबसे पहली बार इस रास्ते का साइंटेफिक ऑबजरवेशन किया और इसकी फोटोग्राफी भी। साल 2013 के 20 दिसंबर महीने में उन्होंने 60 पत्‍थरों को मूव होते देखा।

बाद में उन्होंने डिस्कवर किया कि पत्‍थरों पर असल में हल्की बर्फ की परत होती है। सर्दियों के समय धूप होने पर वो गलने लगती है। तभी पत्‍थर पर पड़ा थोड़ा गीला पानी, बर्फ के अति छोटे कण और हवा के दबाव से वो खिसकने लगते हैं।

ऐसा देखकर लगता है कि पत्‍थर खुदबखुद ही यहां चलते हों। किसी आदमी को इसकी पीछे की सच्चाई पता ना हो, तो हो सकता है कि वो ये सब देखकर डर भी जाए।

The mysterious moving stones of the packed-mud desert of Death Valley have been a center of scientific controversy for decades. Rocks weighing up to hundreds of pounds have been known to move up to hundreds of yards at a time. Some scientists have proposed that a combination of strong winds and surface ice account for these movements. However, this theory does not explain evidence of different rocks starting side by side and moving at different rates and in disparate directions. Moreover, the physics calculations do not fully support this theory as wind speeds of hundreds of miles per hour would be needed to move some of the stones.

Wind and ice both are the favored hypothesis for these mysterious sliding rocks. But as those are only hypothesises, we can say that the mystery remains...

Sources:- http://www.oddee.com/item_96654.aspx

http://m.amarujala.com/feature/omg/world-of-wonders/mystery-of-sailing-stones-hindi-jp/

Nature Blows My Mind! The Strange Snow Formations Called Penitentes

Penitentes

So imagine this: You're strolling along a road in the Andes when suddenly you come across a patch of very spiky ice - spikes that hit as high as your waist, as high as your shoulders. There isn't any other snow around, just rocks and gravel... and these strange spikes of ice.

It'd be a little weird, right? These are called Penitentes (or nieves penitentes). The tall, thin spikes are typically blade-shaped and can be found at high altitudes above 13,000 feet and are made of hardened snow or ice. The blades usually are oriented toward the sun.

These amazing ice spikes, generally known as penitentes due to their resemblance to processions of white-hooded monks, can be found on mountain glaciers and vary in size dramatically: from a few centimetres to 5 metres in height. Initially, the sun’s rays cause random dimples on the surface of the snow. Once such a dimple is formed, sunlight can be reflected within the dimple, increasing the localized sublimation. As this accelerates, deep troughs are formed, leaving peaks of ice standing between them.


Sources:-
http://www.treehugger.com/natural-sciences/nature-blows-my-mind-strange-snow-formations-called-penitentes.html

http://www.oddee.com/item_96654.aspx

NASA probe shows PLUTO has blue skies

Nothing Is Solid & Everything Is Energy

Scientists Explain The World of Quantum Physics

It has been written about before, over and over again, but cannot be emphasized enough. The world of quantum physics is an eerie one, one that sheds light on the truth about our world in ways that challenge the existing framework of accepted knowledge.

What we perceive as our physical material world, is really not physical or material at all, in fact, it is far from it. This has been
proven time and time again by multiple Nobel Prize (among many other scientists around the world) winning physicists, one of them being Niels Bohr, a Danish Physicist who made significant contributions to
understanding atomic structure and quantum theory.

“If quantum mechanics hasn’t profoundly shocked you, you haven’t
understood it yet. Everything we call real is made of things that
cannot be regarded as real.” – Niels Bohr

 At the turn of the nineteenth century, physicists started to explore the relationship between energy and the structure of matter. In doing so, the belief that a physical, Newtonian material universe that was at the very heart of scientific knowing was dropped, and the
realization that matter is nothing but an illusion replaced it.

Scientists began to recognize that everything in the Universe is made
out of energy.

“Despite the unrivaled empirical success of quantum theory, the very
suggestion that it may be literally true as a description of nature is
still greeted with cynicism, incomprehension and even anger.” (T.
Folger, “Quantum Shmantum”; Discover 22:37-43, 2001)

Quantum physicists discovered that physical atoms are made up of vortices of energy that are constantly spinning and vibrating, each one radiating its own unique energy signature. Therefore, if we really want to observe ourselves and find out what we are, we are really beings of energy and vibration, radiating our own unique energy signature -this is fact and is what quantum physics has shown us time
and time again. We are much more than what we perceive ourselves to be, and it’s time we begin to see ourselves in that light. If you observed the composition of an atom with a microscope you would see a small, invisible tornado-like vortex, with a number of infinitely small energy vortices called quarks and photons. These are what make up the structure of the atom. As you focused in closer and closer on the structure of the atom, you would see nothing, you would observe a physical void. The atom has no physical structure, we have no physical structure, physical things really don’t have any physical structure!
Atoms are made out of invisible energy, not tangible matter.

“Get over it, and accept the inarguable conclusion. The universe is
immaterial-mental and spiritual” – Richard Conn Henry, Professor
of Physics and Astronomy at Johns Hopkins University (quote taken from
“the mental universe)

It’s quite the conundrum, isn’t it? Our experience tells us that our reality is made up of physical material things, and that our world is an independently existing objective one. The revelation that the
universe is not an assembly of physical parts, suggested by Newtonian physics, and instead comes from a holistic entanglement of immaterial energy waves stems from the work of Albert Einstein, Max Planck and
Werner Heisenberg, among others.

The Role of Consciousness in Quantum Mechanics 

What does it mean that our physical material reality isn’t really
physical at all? It could mean a number of things, and concepts such
as this cannot be explored if scientists remain within the boundaries
of the only perceived world existing, the world we see. As Nikola Tesla supposedly said:

“The day science begins to study non-physical phenomena, it will make more progress in one decade than in all the previous centuries of its existence.”

Fortunately, many scientists have already taken the leap, and have already questioned the meaning and implications of what we’ve discovered with quantum physics. One of these potential revelations is that “the observer creates the reality.”

A fundamental conclusion of the new physics also acknowledges that the
observer creates the reality. As observers, we are personally involved with the creation of our own reality. Physicists are being forced to admit that the universe is a “mental” construction.

Pioneering physicist Sir James Jeans wrote: “The stream of knowledge is heading toward a non-mechanical reality; the universe begins to look more like a great thought than like a great machine. Mind no longer appears to be an accidental intruder into the realm of matter, we ought rather hail it as the creator and governor of the realm of matter. (R. C. Henry, “The Mental Universe”; Nature 436:29, 2005)

One great example that illustrates the role of consciousness within the physical material world (which we know not to be so physical) is the double slit experiment. This experiment has been used multiple times to explore the role of consciousness in shaping the nature of physical reality.

A double-slit optical system was used to test the possible role of consciousness in the collapse of the quantum wave-function. The ratio of the interference pattern’s double-slit spectral power to its single-slit spectral power was predicted to decrease when attention was focused toward the double-slit as compared to away from it. The study found that factors associated with consciousness, such as meditation, experience, electrocortical markers of focused attention and psychological factors such as openness and absorption, significantly correlated in predicted ways with perturbations in the double-slit interference pattern.

This is just the beginning. I wrote another article earlier this year that has much more, sourced information with regards to the role of consciousness and our physical material world:

http://www.collective-evolution.com/2014/03/08/10-scientific-studies-that-prove-consciousness-can-alter-our-physical-material-world/

What’s The Significance?

The significance of this information is for us to wake up, and realize that we are all energy, radiating our own unique energy signature. Feelings, thoughts and emotions play a vital role, quantum physics helps us see the significance of how we all feel. If all of us are in a peaceful loving state inside, it will no doubt impact the external
world around us, and influence how others feel as well.

“If you want to know the secrets of the universe, think in terms of energy, frequency and vibration.” – Nikola Tesla.

Studies have shown that positive emotions and operating from a place of peace within oneself can lead to a very different experience for the person emitting those emotions and for those around them. At our subatomic level, does the vibrational frequency change the manifestation of physical reality? If so, in what way? We know that when an atom changes its state, it absorbs or emits electromagnetic
frequencies, which are responsible for changing its state.  Do different states of emotion, perception and feelings result in
different electromagnetic frequencies? Yes! This has been proven.

source:- http://www.collective-evolution.com/2014/09/27/this-is-the-world-of-quantum-physics-nothing-is-solid-and-everything-is-energy/

Thermoelectric Effect

The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa. A thermoelectric device creates voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, it creates a temperature difference. At the atomic scale, an applied temperature gradient causes charge carriers in the material to diffuse from the hot side to the cold side.

This effect can be used to generate electricity, measure temperature or change the temperature of objects. Because the direction of heating and cooling is determined by the polarity of the applied voltage, thermoelectric devices can be used as temperature controllers.

The term "thermoelectric effect" encompasses three separately identified effects:
The Seebeck effect,
Peltier effect, and
Thomson effect.

1. The Seebeck effect

The Seebeck effect is the conversion of temperature differences directly into electricity and is named after the Baltic German physicist Thomas Johann Seebeck. Seebeck, in 1821, discovered that a compass needle would be deflected by a closed loop formed by two different metals joined in two places, with a temperature difference between the junctions. This was because the metals responded to the temperature difference in different ways, creating a current loop and a magnetic field. Seebeck did not recognize there was an electric current involved, so he called the phenomenon the thermomagnetic effect. Danish physicist Hans Christian Oersted rectified the mistake and coined the term "thermoelectricity".

2. The Peltier effect

The Peltier effect is the presence of heating or cooling at an electrified junction of two different conductors and is named after French physicist Jean Charles Athanase Peltier, who discovered it in 1834. When a current is made to flow through a junction between two conductors A and B, heat may be generated (or removed) at the junction.

3. Thomson effect

In many materials, the Seebeck coefficient is not constant in temperature, and so a spatial gradient in temperature can result in a gradient in the Seebeck coefficient. If a current is driven through this gradient then a continuous version of the Peltier effect will occur. This Thomson effect was predicted and subsequently observed by Lord Kelvin in 1851. It describes the heating or cooling of a current-carrying conductor with a temperature gradient.

Applications

Thermoelectric generator

The Seebeck effect is used in thermoelectric generators, which function like heat engines, but are less bulky, have no moving parts, and are typically more expensive and less efficient. They have a use in power plants for converting waste heat into additional electrical power (a form of energy recycling) and in automobiles as automotive thermoelectric generators (ATGs) for increasing fuel efficiency. Space probes often use radioisotope thermoelectric generators with the same mechanism but using radioisotopes to generate the required heat difference.

Peltier effect: Thermoelectric cooling
The Peltier effect can be used to create a refrigerator that is compact and has no circulating fluid or moving parts. Such refrigerators are useful in applications where their advantages outweigh the disadvantage of their very low efficiency.

Temperature measurement:

Thermocouples and thermopiles are devices that use the Seebeck effect to measure the temperature difference between two objects, one connected to a voltmeter and the other to the probe. The temperature of the voltmeter, and hence that of the material being measured by the probe, can be measured separately using cold junction compensation techniques.

Thermal cyclers for polymerase chain reaction

The Peltier effect is used by many thermal cyclers, laboratory devices used to amplify DNA by the polymerase chain reaction (PCR). PCR requires the cyclic heating and cooling of samples to specified temperatures. The inclusion of many thermocouples in a small space enables many samples to be amplified in parallel.

मंगल को लेकर NASA का बड़ा खुलासा, स्पेस एजेंसी ने ग्रह पर पानी होने की पुष्टि की

वॉशिंगटन. अमेरिकी स्पेस एजेंसी नासा ने मार्स एक्सप्लोरेशन प्रोग्राम से जुड़ा बड़ा खुलासा किया है। नासा ने मंगल ग्रह पर पानी होने की पुष्टि की है। साइंटिस्ट्स का मानना है कि मंगल ग्रह पर देखी गई गहरी लकीरों को अब तरल पानी के सामयिक बहाव से जोड़कर देखा जा सकता है। नासा के सैटेलाइट से मिला डाटा से पता चलता है कि चोटियों पर दिखने वाले ये लक्षण नमक की मौजूदगी से जुड़े हैं। अहम बात है कि ऐसा नमक, पानी के जमने और भांप बनने के तापमान को भी बदल सकते हैं। इससे पानी ज्यादा समय तक बह सकता है। नासा के इस खुलासे से मंगल ग्रह पर जीवन होने की नई उम्मीद जगी है।

लुजेंद्र की बात पर लगी मुहर
मंगल पर पानी मिलने की संभावना इसलिए जोर पकड़ी थी, क्योंकि नासा ने इस अनाउंसमेंट में लुजेंद्र ओझा नाम के पीएचडी स्टूडेंट के शामिल होने की बात कही थी। 2011 में ग्रैजुएट कर चुके 21 वर्षीय लुजेंद्र ने मंगल पर पानी के संभावित लक्षण खोजे हैं। बता दें कि वैज्ञानिकों को मंगल के ध्रुवों पर जमे हुए पानी की जानकारी तो पहले से है, लेकिन इसे लिक्विड फॉर्म में खोजा जाना अभी बाकी है।

ओझा ने बताया था, भाग्यशाली दुर्घटना
एरिजोना यूनिवर्सिटी में पढ़ाई के दौरान ओझा को 'संयोगवश' पहली बार इस बात के सबूत मिले थे कि मंगल पर लिक्विड फॉर्म में पानी मौजूद है। प्लैनेट की सतह की तस्वीरों की स्टडी के बाद उन्हें इस बात के सबूत मिले थे। ओझा ने इस खोज को 'भाग्यशाली संयोग' बताते हुए कहा कि शुरुआत में उन्हें इसके बारे में समझ में नहीं आया। मंगल की सतह पर बने गड्ढों की कई साल तक स्टडी के बाद पता चला कि ये बहते पानी के कारण बने हैं।
 
40 साल पहले मिले थे पोल पर बर्फ के सबूत
मंगल पर पानी के सबूत मिलना कोई नई बात नहीं है। करीब चार दशक पहले इस प्लैनेट के पोल पर बर्फ की खोज की गई थी। इसके अलावा, ग्रह की सतह पर रगड़ के निशान इस ओर इशारा करते हैं कि लाखों साल पहले यहां समुद्र और नदियां रही होंगी। हालांकि, इस ग्रह पर कम ग्रैविटी और वहां के वायुमंडल के आधार पर माना जाता है कि ग्रह पर मौजूद पानी स्पेस में इवैपेरेट (वाष्पित) हो गया होगा। प्लैनेट पर लिक्विड पानी की यह पहली खोज है।

What happen to your donated blood after blood donation?

Step 1: The Donation

1. Donor registers
2. Health history and mini physical are completed
3. About 1 pint of blood and several small test tubes are collected from each donor
4. The bag, test tubes and the donor record are labeled with an identical bar code label to keep track of the donation
5. The donation is stored in iced coolers until it is transported to a Red Cross center

Step 2: Processing

1. Donated blood is scanned into a computer database
2. Most blood is spun in centrifuges to separate the transfusable components – red cells, platelets, and plasma
3. The primary components like plasma, can be further manufactured into components such as cryoprecipitate
4. Red cells are then leuko-reduced
5. Single donor platelets are leukoreduced and bacterially tested.
6. Test tubes are sent for testing.

Step 3: Testing

1. Steps 2 and 3 take place in parallel
2. The test tubes are received in Red Cross National Testing Laboratories
3. A dozen tests are performed on each unit of donated blood – to establish the blood type and test for infectious diseases
4. Test results are transferred electronically to the manufacturing facility within 24 hours
5. If a test result is positive, the unit is discarded and the donor is notified. Test results are confidential and are only shared with the donor, except as may be required by law

Step 4: Storage

1. When test results are received, units suitable for transfusion are labeled and stored
2. Red Cells are stored in refrigerators at 6ºC for up to 42 days
3. Platelets are stored at room temperature in agitators for up to five days
4. Plasma and cryo are frozen and stored in freezers for up to one year

Step 5: Distribution

Blood is available to be shipped to hospitals 24 hours a day, 7 days a week.

Source:-http://m.redcrossblood.org/learn-about-blood/what-happens-donated-blood

How to prevent dengu virus to host its carrier.

GENETICALLY MODIFIED MOSQUITOS MASSIVELY REDUCE DENGUE FEVER RISK

TEST IN BRAZILIAN CITY JUAZEIRO IS MOST SUCCESSFUL TRIAL OF ALTERED SKEETERS EVER

Dengue fever is so excruciating that it is often called the “bone breaker,” causing severe pain in the joints and abdomen, vomiting, and circulatory system failure. It’s nearly impossible to treat, so the only way to cut down on incidences of the disease is to decrease the number of mosquitoes that carry it. One startling effective way to do that: genetically modifying mosquitos so their offspring won't survive. A year-long trial with genetically modified mosquitoes in northeast Brazil has been the most successful yet, reducing the population of the disease-carrying insects by 95 percent.

The British biotech company Oxitec has been developing a unique form of pest control for over a decade. Since dengue is primarily spread through the mosquito species Aedes aegypti, Oxitec has engineered a male mosquito that, to female mosquitoes in the wild, looks just like the usual males. However, when the mosquitoes mate, their young carry a mutation that kills them before they’re able to reproduce or transmit the disease.
Juazeiro, a city in northeast Brazil, was a great place to try them out. After it was wiped out for 20 years, dengue has been on the rise in Brazil, with an estimated 16 million new cases every year. Many of the mosquitoes that carry the disease are also resistant to pesticides, which meant that Brazilians were left with few options to decrease dengue’s prevalence. The neighborhood in which the researchers tested the modified mosquitoes was a low-income area with high rates of dengue infection, according to local public health officials. Over a one-year period, the researchers released the modified males into the local environment and monitored the resulting eggs, looking for a characteristic fluorescent marker engineered into the males’ genome. In the course of that year, the number of disease-carrying mosquitoes decreased by 95 percent as compared to a control group in a neighborhood next door.
This isn’t Oxitec’s first attempt to decrease the prevalence of disease-carrying mosquitoes—the company did another trial in the Cayman Islands in 2010—but this test was the most successful. The researchers hope to scale up their efforts to eradicate dengue and the insects that carry it in a larger area.

Source:-
http://www.popsci.com/genetically-modified-mosquito-knocks-out-dengue-brazilian-neighborhood

What is transformer? Definition & Working Principle of Transformer

What is transformer?

Definition & Working Principle of Transformer

Electrical power transformer is a static device which transforms electrical energy from one circuit to another without any direct electrical connection and with the help of mutual induction between two windings. It transforms power from one circuit to another without changing its frequency but may be in different voltage level.

Working Principle of Transformer

The working principle of transformer is very simple. It depends upon Faraday's law of electromagnetic induction. Actually, mutual induction between two or more winding is responsible for transformation action in an electrical transformer.

Faraday's Laws of Electromagnetic Induction

According to these Faraday's laws,

"Rate of change of flux linkage with respect to time is directly proportional to the induced EMF in a conductor or coil".

Basic Theory of Transformer

Say you have one winding which is supplied by an alternating electrical source. The alternating  current  through the winding produces a continually changing flux or alternating flux that surrounds the winding. If any other winding is brought nearer to the previous one, obviously some portion of this flux will link with the second. As this flux is continually changing in its amplitude and direction, there must be a change in flux linkage in the second winding or coil.

According to Faraday's law of electromagnetic induction, there must be an EMF induced in the second. If the circuit of the later winding is closed, there must be an  current flowing through it. This is the simplest form of electrical power transformer and this is the most basic of working principle of transformer.

For better understanding, we are trying to repeat the above explanation in a more brief way here. Whenever we apply alternating  current  to an electric coil, there will be an alternating flux surrounding that coil. Now if we bring another coil near the first one, there will be an alternating flux linkage with that second coil. As the flux is alternating, there will be obviously a rate of change in flux linkage with respect to time in the second coil. Naturally emf will be induced in it as per Faraday's law of electromagnetic induction. This is the most basic concept of the theory of transformer.

The winding which takes electrical power from the source, is generally known as primary winding of transformer. Here in our above example it is first winding.

The winding which gives the desired output voltage due to mutual induction in the transformer, is commonly known as secondary winding of transformer. Here in our example it is second winding.

The above mentioned form of transformer is theoretically possible but not practically, because in open air very tiny portion of the flux of the first winding will link with second; so the  current that flows through the closed circuit of later, will be so small in amount that it will be difficult to measure.

The rate of change of flux linkage depends upon the amount of linked flux with the second winding. So, it is desired to be linked to almost all flux of primary winding to the secondary winding. This is effectively and efficiently done by placing one low reluctance path common to both of the winding. This low reluctance path is core of transformer, through which maximum number of flux produced by the primary is passed through and linked with the secondary winding. This is the most basic theory of transformer.

Main Constructional Parts of Transformer

The three main parts of a transformer are,
Primary Winding of transformer - which produces magnetic flux when it is connected to electrical source.

Magnetic Core of transformer - the magnetic flux produced by the primary winding, that will pass through this low reluctance path linked with secondary winding and create a closed magnetic circuit.

Secondary Winding of transformer - the flux, produced by primary winding, passes through the core, will link with the secondary winding. This winding also wounds on the same core and gives the desired output of the transformer.

Source:-
http://img.directindustry.com/images_di/photo-g/electric-arc-furnace-transformer-112419-3725717.jpg

Flying Tree Snake

Flying Tree Snake
(Chrysopelea spp.)

If you are lucky, you may spot this elegant snake warming itself quietly in a sunny spot at Sungei Buloh Nature Park. But you have to be sharp eyed as they are well camouflaged.

They are the largest of the Flying Snakes, so named because they are the only snakes that can move through the air. They don't actually fly or glide but instead, perform a sort of parachute jump.

Soaring Serpents: To do this, they "suck in their guts" to form a U-shaped half-cylinder along the entire length of their bodies. The outer edges of their belly scales are rigid while the central portion of their belly scales fold upwards. This concave surface acts like a parachute, and increases air resistance to prolong the "flight".

The snake has some degree of control, undulating through the air as if swimming, holding its tail rigidly upwards and twisting the tail from side to side for balance. In this way, they can cross as much as 100m, although they crash land clumsily. This allows them to cross long distances quickly, perhaps to catch prey, escape predators or simply to move around. They generally parachute from tree to tree, but sometimes from tree to ground. To achieve this feat, they first have to climb up a tall launch point, which is not a problem as they have ridged (keeled) belly scales to help them grip vertical surfaces.

Although a cornered snake can be aggressive, the few snakes that I have come across in the park are shy and retiring. If they are left alone and observed from a distance, they remain motionless or quietly go about their business. Their venom is mild, and affects only their small prey. Their fangs are short, located at the back of the mouth, and are not hypodermic-like; the venom is injected through grooves in the fangs. Thus, they can only inject venom into prey that is well inside their mouths. As such, they hunt small prey like lizards, frogs, birds and bats. They stalk or pursue the prey and bite them on the neck. Small prey may be killed by their strong crushing jaws. Flying Snakes are active during the day and are mostly found in trees rather than on the ground.

Breeding: Little is known about their breeding habits. They lay 6-11 eggs, hatchlings are 15-20cm long and have the same pattern as the adults but their colours are brighter.

Role in the habitat: Like other predators, they control the populations of their prey. They are also eaten by others higher up on the food chain.

Status and threats: Flying Tree Snakes are not endangered at present. They do not tame well and do poorly in captivity.

Source:- http://www.naturia.per.sg/buloh/verts/flying_tree_snake.htm

Leidenfrost effect

The Leidenfrost effect is a phenomenon in which a liquid, in near contact with a mass significantly hotter than the liquid's boiling point, produces an insulating vapor layer keeping that liquid from boiling rapidly. 

This is most commonly seen when cooking; one sprinkles drops of water in a pan to gauge its temperature: if the pan's temperature is at or above the Leidenfrost point, the water skitters across the pan and takes longer to evaporate than in a pan below the temperature of the Leidenfrost point (but still above boiling temperature).

The effect is also responsible for the ability of liquid nitrogen to skitter across floors. It has also been used in some potentially dangerous demonstrations, such as dipping a wet finger in molten lead or blowing out a mouthful of liquid nitrogen, both enacted without injury to the demonstrator. The latter is potentially lethal, particularly should one accidentally swallow the liquid nitrogen.

The effect can be seen as drops of water are sprinkled onto a pan at various times as it heats up. Initially, as the temperature of the pan is below 100 °C (212 °F), the water just flattens out and slowly evaporates. As the temperature of the pan goes above 100 °C (212 °F), the water drops hiss when touching the pan and evaporate quickly. Later, as the temperature exceeds the Leidenfrost point, the Leidenfrost effect comes into play. On contact with the pan, the water droplets bunch up into small balls of water and skitter around, lasting much longer than when the temperature of the pan was lower. This effect works until a much higher temperature causes any further drops of water to evaporate too quickly to cause this effect.

This is because at temperatures above the Leidenfrost point, the bottom part of the water droplet vaporizes immediately on contact with the hot plate. The resulting gas suspends the rest of the water droplet just above it, preventing any further direct contact between the liquid water and the hot plate. As steam has much poorer thermal conductivity, further heat transfer between the pan and the droplet is slowed down dramatically. This also results in the drop being able to skid around the pan on the layer of gas just under it.

The temperature at which the Leidenfrost effect begins to occur is not easy to predict. Even if the volume of the drop of liquid stays the same, the Leidenfrost point may be quite different, with a complicated dependence on the properties of the surface, as well as any impurities in the liquid. Some research has been conducted into a theoretical model of the system, but it is quite complicated. As a very rough estimate, the Leidenfrost point for a drop of water on a frying pan might occur at 193 °C (379 °F).[citation needed]

The effect was also described by the eminent Victorian steam boiler designer, Sir William Fairbairn, in reference to its effect on massively reducing heat transfer from a hot iron surface to water, such as within a boiler. In a pair of lectures on boiler design, he cited the work of one M. Boutigny & Professor Bowman of King's College, London in studying this. A drop of water that was vaporized almost immediately at 334 °F (168 °C) persisted for 152 seconds at 395 °F (202 °C). Lower temperatures in a boiler firebox might evaporate water more quickly as a result; compare Mpemba effect. An alternative approach was to increase the temperature beyond the Leidenfrost point. Fairbairn considered this too, and may have been contemplating the flash steam boiler, but considered the technical aspects insurmountable for the time.

The Leidenfrost point may also be taken to be the temperature for which the hovering droplet lasts longest.

It has been demonstrated that it is possible to stabilize the Leidenfrost vapour layer of water by exploiting superhydrophobic surfaces. In this case, once the vapour layer is established, cooling never collapses the layer, and no nucleate boiling occurs; the layer instead slowly relaxes until the surface is cooled.

Leidenfrost point

 A water droplet experiencing Leidenfrost effect on a hot stove hot plate

The Leidenfrost point signifies the onset of stable film boiling. It represents the point on the boiling curve where the heat flux is at the minimum and the surface is completely covered by a vapor blanket. Heat transfer from the surface to the liquid occurs by conduction and radiation through the vapor. In 1756, Leidenfrost observed that water droplets supported by the vapor film slowly evaporate as they move about on the hot surface. As the surface temperature is increased, radiation through the vapor film becomes more significant and the heat flux increases with increasing excess temperature..

The minimum heat flux for a large horizontal plate can be derived from Zuber's equation,

where the properties are evaluated at saturation temperature. Zuber's constant, C is approximately 0.09 for most fluids at moderate pressures.

Source:- https://www.engineersedge.com/physics/leidenfrost_effect_13089.htm

Wireless Electricity Transmission

Wireless Electricity Transmission

Magnetic induction is a technology that you will probably remember from your physics classes at high school.

The magnetic fields used to transfer energy are "perfectly safe" -- in fact, they are the same kind of fields used in Wi-Fi routers.

In the house of the future, wire-free energy transfer could be as easy as wireless internet.

If all goes to WiTricity's plans, smartphones will charge in your pocket as you wander around, televisions will flicker with no wires attached, and electric cars will refuel while sitting on the driveway.

WiTricity has already demonstrated the ability to power laptops, cell-phones, and TVs by attaching resonator coils to batteries -- and an electric car refueler is reportedly in the works.

Introduction
Wireless Power transfer was first demonstrated by Nikola Tesla in the 1890s, however it is only really in the last decade that the technology has been harnessed to the point where it offers real, tangible benefits to real world applications.  Applications using resonant wireless power technology have been most noticeable in the Consumer Electronics market where wireless charging promises to deliver new levels of convenience for the charging of millions of everyday devices.

(Wireless) Inductive Power Transfer or IPT involves the transmission of energy from a power source to an electrical load, without connectors, across an air gap.  The basis of a wireless power system involves essentially two coils – a transmitter and receiver coil.  The transmitter coil is energized by alternating current to generate a magnetic field, which in turn induces a current in the receiver coil.

How does Wireless Power work?
The basics of wireless power involves the transmission of energy from a transmitter to a receiver via an oscillating magnetic field.

To achieve this, Direct Current (DC) supplied by a power source, is converted into high frequency Alternating Current (AC) by specially designed electronics built into the transmitter.

The alternating current energizes a copper wire coil in the transmitter, which generates a magnetic field.  Once a second (receiver) coil is placed within proximity of the magnetic field, the field can induce an alternating current in the receiving coil.

Electronics in the receiving device then converts the alternating current back into direct current, which becomes usable power.

The diagram below simplifies this process into four key steps.

1. The ‘mains’ voltage is converted in to an AC signal (Alternating Current), which is then sent to the transmitter coil via the electronic transmitter circuit.
2. The AC current flowing through the transmitter coil induces a magnetic field which can extends to the receiver coil (which lies in relative proximity)
3. The magnetic field then generates a current which flows through the coil of the receiving device. The process whereby energy is transmitted between the transmitter and receiver coil is also referred to as magnetic or resonant coupling and is achieved by both coils resonating at the same frequency. Current flowing within the receiver coil is converted into direct current (DC) by the receiver circuit, which can then be used to power the device.


What is meant by “Resonance”?
The distance at which the energy can be transferred is increased if the transmitter and receiver coils are resonating at the same frequency.

This resonant frequency refers to the frequency at which an object naturally vibrates or rings – much like the way a tuning fork rings at a particular frequency and can achieve their maximum amplitude.

A Brief History

The idea of inductive power was made possible in 1888 when German physicist Heinrich Hertz proved the existence of electromagnetic waves by creating a spark gap transmitter and receiver.

A spark generated by the transmitter also created a small spark in the receiver, which could be seen with a microscope. Serbian American inventor and engineer Nikola Tesla learned of Hertz’s work by the following year and began duplicating his experiments.

By 1891, Tesla had developed a high-tension induction coil, which he used to demonstrate wireless energy transmission. He successfully presented his technique to the American Institute of Electrical Engineers and the National Electric Light Association. By 1894 Tesla had developed the equipment to wirelessly light incandescent lamps at his New York laboratory. This method used resonant inductive coupling, which involves tuning two nearby coils to resonate at the same frequency.

By 1896 he had increased the range of transmission to 30 miles (48 km). Tesla began construction on his Wardenclyffe Tower, designed for wireless broadcasting and power generation, in 1901. After several construction delays and technical setbacks, the project ran out of funds a few years later and was eventually demolished. After this, no significant advances were made for more than 50 years.

In the early 1970s, experiments with RFID tags began and by the early 2000’s Professor She Yuen (Ron) Hui and S.C. Tang developed a charger to provide resonant power transfer for small electronics. Today wireless power is used for everything from industrial motors to charging smartphones and tablets.

Researchers predict that wireless power will be making a significant contribution to energy supplies by the end of this decade.

Benefits of Wireless Power

1. Reduce costs associated with maintaining direct connectors
2. Greater convenience for ​the charging of everyday electronic devices
3. Safe​ power transfer to applications that need to remain sterile or hermetically sealed
4. Electronics can be fully enclosed, reducing the risk of corrosion due to elements such as oxygen and water.
​Robust and consistent power delivery to rotating, highly mobile industrial equipment​
5. ​Delivers reliable power transfer to mission critical systems in wet, dirty and moving environments.
6. Whatever the application, the removal of the physical connection delivers a number of benefits over traditional cable connectors, some of which aren’t always obvious.  The video below highlights just some of the benefits and advantages of wireless power and offers an insight into a world where wireless power is widely integrated into industrial and mission critical environments.

http://www.youtube.com/embed/tKJGpXIu8s0


Source:-http://powerbyproxi.com/wireless-power/

Why does water rise in the burning candle experiment?

Objective: 
To study the rise of water in the inverted glass which covers a burning candle placed in water. 

Equipment:
three plates, four similar candles, three drinking glasses of same size.

Introduction:
The experiment described in the first part is very famous and is used by many teachers and students to show that there is 21% oxygen in air. In this demo experiment I will show that the real physics of rising water is very different.

Procedure:
Put a candle vertically in a plate. Light the candle. Put some water in the plate so that a small lower portion of the candle is in water. The candle keeps on burning. Cover  the burning candle by an inverted glass. The candle goes off and water rises in the glass. How much water will rise in glass depends on the thickness of the candle and how much time you allowed the candle to burn before you covered it.
Use a candle and cover it quickly after burning. As the candle goes off, very small amount of water rises in the glass. It could be hardly 5% of the volume of the glass. Leave this set up as it is and take another plate, put a similar candle, pour water, light the candle and wait for some time. If a fan is running nearby put it off. Now cover it with a glass of the same size. This time water rise will be much more. 
Now take the third plate and put two candles in it. Pour water in the plate and light all the candles. Wait for some time and then cover both by a glass of the same size as used in the previous trials. This time the water rise will be very high, may be 40-50%.
What is the Physics of this rising water? When candle burns the air surrounding the flame becomes hot. The flame itself is very hot gases. The pressure of this surrounding air is the same as the atmospheric pressure as all air is connected. As pressure remains the same and the temperature rises the density goes down from the gas law
PV = nRT. For a given volume n will decrease if T increases.  When you cover the candle(s) you trap this less dense air. As the oxygen is consumed and the candle goes off, the air (gases in fact) inside the glass cools down. As the number of moles n is now fixed, decreasing the temperature will decrease the pressure and this will suck water in the glass. In equilibrium the temperature in the glass will be the same as the room temperature, the pressure will be P= P0-hrg, where P0 is the atmospheric pressure and h is the height water rises.
If you cover the candle just after the burning, the air trapped is not that hot. The density is thus not much lowered and hence on candle going off the water rise is not much. On the other hand if you burn two candles together the surrounding air becomes much more hotter and hence the water rise is high.

Discussion:
The experiment described clearly shows that the rise of water has no relation with the oxygen content in air. In fact for each oxygen molecule consumed, you produce a molecule of CO2 among other products. Also the solubility of CO2 is lower than that of O2. So there is no question of decrease in pressure inside due to consuming oxygen.
There is another factor that contributes in rising water in the glass. At higher temperature the saturation vapour pressure of water is also high. As the air in the inverted glass is in contact with water, it will contain saturated vapour. When the candle goes off and the temperature falls, saturation vapour pressure also decreases and some of the vapour condenses. This also decreases pressure inside and helps in rise of water.
Please note that water starts rising only after the candle goes off.

विज्ञान अध्यापक फैलाएं वैज्ञानिक चेतना।।।

यह पोस्ट मैंने शिक्षा सारथी मैगज़ीन अंक मई, 2015 से ली है जो सेकेंडरी एजुकेशन हरियाणा के द्वारा प्रकाशित की जाती है। अच्छी लगी इसलिए शेयर कर रहा हूँ।

तांत्रिकों के काले जादू की सच्चाई!

तांत्रिकों के काले जादू की सच्चाई!

आज भी कई ऐसे लोग हैं जो काला जादू, तंत्रमंत्र जैसे अंधविश्वासों में आसानी से फंस जाते हैं और तांत्रिकों के हाथों का खिलौना बने रहते हैं।

नींबू से खून निकालना, चढ़ावे के नारियल में अचानक से आग धधकने लगना, कपड़े पर लाल रंग का पंजा बन जाना जैसी हरकतें कर तांत्रिक मासूमों के सामने चकाचौंध पैदा कर देते हैं और लोग इस छलावे में आ जाते हैं।

जबकि असलियत यह है कि इन सब गतिविधियों के पीछे विज्ञान की एक दुनिया चलती है। कुछ केमिकल रिएक्शन और हाथ की सफाई की मदद से तांत्रिक लोगों को अपने शिकंजे में आसानी से लेते हैं। हमारी कोशिश लोगों को इसकी सही जानकारी देने की है ताकि वे डर के साए से निकल सकें।

तंत्रों के पीछे क्या है विज्ञान :

1.) नीबू में पहले ही मिथेन रेड व ऑरेंज का इंजेक्शन दिया जाता है और जैसे ही नीबू का एसिड इस केमिकल के संपर्क में आता है यह लाल रंग का हो जाता है। काटने पर यह खून जैसा दिखता है।

2.) एक बाउल में एनएओएच (सोडियम हाइड्रोक्साइड लिक्विड) पहले से रखा होता है जिसे तांत्रिक जादुई जल कहते हैं। इसके साथ ही टर्मरिक क्लॉथ रखा होता है। तांत्रिक यह दावा करते हैं कि यदि जीवन में किसी आत्मा का प्रकोप होगा तो इस जल को छूने और इस कपड़े पर हाथ रखने पर खून के धब्बे हो जाएंगे। जबकि एनएओएच का टर्मरिक के साथ संपर्क होने पर वह लाल रंग का हो जाता है।

3.) इसी तरह तंत्र में प्रयोग होने वाले नारियल में पहले ही सोडियम मेटल डाले जाते हैं और जैसे ही इस पर पानी का छिड़काव होता है यह रिएक्शन कर आग बन जाता है।

By:- Dr Rakesh Punj

http://punjvardanproduction.blogspot.in/2013/02/blog-post_3139.html?m=1

भारत में एक मान्यता के मुताबिक रात में पीपल के पेड़ो के पास नहीं जाना चाहिए।

अंधविश्वास या विज्ञान

अंधविश्वास
एक मान्यता के मुताबिक रात में पीपल के पेड़ो पर बुरी आत्माओ या बुरी शक्तियों का वास होता है | और हमें बताया गया है की रात को पीपल के पेड़ पास नही जाना चाहिए और पीपल के पेड़ को घर के आंगन में नहीं लगाना चाहिए |

इसके पीछे का विज्ञान

पीपल को पेड़ो का राजा माना गया है यह आम पेड़ो के मुकाबले ज्यादा जल्दी बढ़ता है और इसकी जड़े ज्यादा गहराई तक होती है और इसकी शाखाये भी लम्बी और घनी होती है | ये रात में ज्यादा तेजी से ऑक्सीजन लेता है और कार्बन डाई ऑक्साइड छोड़ता है जो की मनुष्य के लिए हानिकारक होती है | इसलिए हमारे बुजुर्गो ने रात के समय पीपल के पेड़ के पास जाने और उसके नीचे सोने से मना करते थे क्योकि वो इस रहस्य को जानते थे |

Even When You’re Standing Still, You’re Still Moving

Even When You’re Standing Still, You’re Still Moving

A human body, or any object on the Earth, is never at rest. Even when you’re asleep in bed, you’re moving pretty fast. Our Milky Way Galaxy is rotating at 225 kilometers per second, and hurling through the cosmos at an estimated 305 kilometers per second. Add those figures together, and we’re racing through space at around 530 kilometers, or 330 miles per second. So in one minute’s time, you’ve  traveled almost 20,000 kilometers, or more than 12,000 miles. And your friends always complain that you never go anywhere.

Why does water not catch fire, but instead extinguishes it? What is the scientific reason?

Hydrogen gas is an inflammable gas and oxygen plays a vital role in combustion process then how does water (hydrogen +  oxygen) extinguishes it?

Water doesn't catch fire because it can't burn anymore.  Burning in our atmosphere is a reaction with oxygen, and when we burn hydrogen  in presence of oxygen in proper proportion by use of electric spark then the result is water. So the hydrogen has already been burnt. You can't burn twice.

The properties of a compound (like water) do not have any relation to the properties of the elements which it comprises.

In case of H2 the potential energy of H atom is more so it is less stable but when it combine with oxygen to form a molecule of water then its potential energy is minimum and it is more stable.
Now the hydrogen atoms in a water molecule are already in a stable state, and do not posess the potential energy of H atoms attached to each other. They do not explode(burn) on contact with oxygen because they don't have energy to give off.

A good analogy is to imagine 2 rocks of exactly equal properties; one at the top of a hill and one at the bottom. You nudge the one at the top of the hill and notice it rolls away down the hill. You walk down and nudge the other rock and notice it doesn't roll away. Why not? It's already at the bottom!

The reason water extinguishes flames is because it is exceptionally good at absorbing heat.  Water both takes a lot of energy to raise in temperature and to transform into steam, so dumping a large quantity of water on a fire will decrease the temperature down to a level where flames are not actively propagating.


Source:-
https://www.quora.com/Why-does-water-not-catch-fire-but-instead-extinguishes-it-What-is-the-scientific-reason

Do you know why you can’t boil an egg on Mount Everest?

Imagine you climbed the Mount Everest! You have achieved something unbelievable and wonderful, you are unspeakably proud of yourself and you are absolutely excited and happy. But you will not be able to have one thing: a freshly boiled egg!

After you have done the unthinkable you believe anything is possible, just not boiling an egg. Why?

Well, the problem is with the height, the air pressure and the water temperature.

Air pressure and temperature – a never-ending relationship

As higher you get as lower the air pressure becomes. And air pressure is always connected with temperature. So, if the air pressure goes down the temperature goes down, logically if the air pressure goes up the temperature goes up as well. They are always in a relationship and connection.

So due to the low air pressure on a high mountain the water boils, with bubbles and steam, already at a low temperature.  We have to remember that once the water boils it will not get hotter. So if the water boils at a specific water temperature it will stay at this temperature, no matter what.

It’s about height, air pressure and water temperature!

At sea level water boils at 100 degrees Celsius (212 degrees Fahrenheit). And with every 300 m we go up the temperature at which the water boils goes down by 3 degrees Celsius.

Boiling eggs

So what’s the story with boiling eggs? Eggs have something interesting, the yolk and the egg white don’t harden at the same water temperature. The yolk needs around 65 C (149 F) to get hard and the egg white needs around 85 C (185 F) to get hard. So if we are at the Mount Everest, which we climbed up at the beginning, we are at 8 848 m (29029 feet).  There the water boils already at around 70 C (158 F). So the yolk might get hard but the white outside will stay glibber and we cannot enjoy our egg.

What about other famous mountains?

Mont Blanc at 4 810 m (15 782 feet), Mount Kilimanjaro at 5 895 m (19 341 feet) and  Mount McKinley at 6 194 m (20 237 feet) ?

Well, at Mont Blanc water boils at 84 C (183 F).  We can boil our egg there with no problem. At Mount Kilimanjaro the water boils at 80 C (176 F) and at Mount McKinley the water boils at 79 C (174 F). There we might have a problem with boiling the egg white. But maybe, if we boil the egg long enough, we will be successful there as well. But once we are above 7 000 m (22 966 feet) no eggs can be boiled anymore.

And do you know what a pressure cooker has to do with all I mentioned above? Well, in a pressure cooker you get the pressure really high which allows the temperature to be above 100 Celsius (212 Fahrenheit). This speeds up cooking.

Source:-

http://simplyilka.com/2014/05/22/know-cant-boil-egg-mount-everest/

How do Astronauts communicate in space?

How do Astronauts communicate in space?

Sound is a form of energy which require material medium to travel.

In order to hear sound it must travel through air (gas particles). Sound can only travel through a solid, liquid or gas. Space being an almost perfect vacuum does not allow sound to travel and be heard by the ears. Sound is vibrations of air particles, so any “sound” that is heard in space has to come from other means such as from the electromagnetic spectrum and these waves are not sound.

As such, astronauts communicate with each other in space when they are spacewalking through the use of radio waves. Radio wave signal are sent to their headsets which then translates the signal into the form of sound . When receiving and sending message to earth it is sent in the form of radio waves which is then translated to sound wave by a radio set.

Radio wave is a part of the light spectrum called electromagnetic spectrum and is therefore a light wave. Electromagnetic waves does not need a medium to travel.

Astronauts can however, talk to each other as if they were on Earth only when they are in their space ship. Here, there are enough air particles to vibrate and take the sound to their ear drum.

Source:-

http://tellmewhyfacts.com/2007/12/how-do-astronauts-communicate-in-space.html

Bernoulli Balls

Bernoulli Balls

A simple hair-dryer becomes a magical levitation device through an understanding of the principles of fluid flow.

Ingredients:

1. hair dryer (make sure you have an appropriate power supply available!)
2. small light balls (such as polystyrene balls available at most craft shops, or ping pong balls)

Instructions

1. Orient the hair dryer so that the outlet is pointing directly upwards. Turn it on.
Place a ball carefully in the flow from the hairdryer. It will balance in the air, appearing to levitate!
2. Gently move the hairdryer from side to side – the ball will stay in the air stream, i.e. will also move back and forth. Repeat this process moving the hairdryer up and down.
3. Carefully tilt the hairdryer – the ball will still stay in the airstream, hanging in mid-air with nothing directly underneath it.
4. Try using balls of differing sizes, and challenge your audience to see how many they can place in the airstream at once.

How Does it Work?

The upward pressure from the hairdryer balances the downward force of gravity, keeping the ball 'levitating'. The more impressive part of this trick is being able to move the ball along with the hairdryer and angle it. The stream of air sticks to the surface of the ball. This is a demonstration of the Coanda Effect, which emerges when fluids like air or water pass over curved surfaces. When the ball approaches the edge of the stream, air is curved round the ball and directed out of the stream. This has the effect of pushing the ball back into the stream. This is the process that enables the ball to balance inside the airstream and stay in the airstream as the hairdryer is moved around.

Tips for Success

Try to find a hairdryer with a 'cool' setting – it will last longer and allow you to perform the trick for much longer in one sitting, without the hairdryer overheating. Make sure that the balls aren't larger than the output of the hairdryer or it won't work. Tilting the hairdryer to too great an angle will cause the ball to fall out of the airstream – although most audiences enjoy seeing the effect!

Serving Suggestions

This is a good eye-catching demonstration that can keep audiences amused for a significant period of time – everyone wants to have a go, especially when challenged to make the largest number of balls stay within the airstream. However, it does require a power supply so is generally limited to indoor venues.

Did You Know?

The Bernoulli Effect underlies the principle of the aerofoil. By encouraging air to flow more quickly over the top surface of a wing an upward pressure is produced by the slower moving air beneath. This phenomenon can also be demonstrated by holding up two sheets of paper and blowing between them. Instead of moving apart, they are drawn together. If you thought anyone could have worked this out, remember that Daniel Bernoulli was awarded his masters degree at the ripe old age of 16.

Source:-
http://www.physics.org/interact/physics-to-go/bernoulli-balls/index.html

Balloon Kebabs

Balloon Kebabs

Density and pressure effects are explored using a simple visual demonstration.

Ingredients:

balloons
wooden kebab skewers

Instructions

1. Blow up the balloons (not full) and tie them off.
2. Challenge your audience to make a 'balloon kebab' – to insert the wooden skewer all the way through the balloon without popping it. Let a few people have a try – they will invariably try to insert the skewer fairly slowly through the side, and the balloon will pop.

Show them how physics can make the trick work:

1. Start by lining up the skewer point with the darker patch on the balloon, opposite the tie end. Gently push the skewer through. You may find that a twisting motion works best.
2. Once the skewer is through one side, push it gently through the balloon until the point of the skewer is at the opposite end – the darker area around the tie.
3. Insert the skewer tip gently through the soft part of the balloon where the tie is – again use the twisting motion if it helps. Voila! – you have made a balloon kebab!

See video at:- http://m.youtube.com/watch?v=jwE4oSv7Qds

How Does it Work?

This trick works through an understanding of surface properties. A balloon is formed by inserting air into a flexible thin rubber sheet. Most of the balloon is stretched evenly, but there are two points where the rubber is least stretched – and thus there is the lowest surface tension. These correspond to the tied section and the darker patch at the opposite side of the balloon – in fact the darker colour indicates that the balloon is less stretched over that region. Most of the balloon is under high tension, so attempting to push the skewer through just makes the balloon pop. But at the low tension sections it is possible to make a small hole without breaking the overall surface of the balloon.

Tips for Success

This trick works best with round balloons (rather than long skinny ones) – mainly so that the kebab skewers can fit! Don't blow up the balloon too much or it will pop even if you do it correctly. Make sure the skewer ends are fairly sharp – blunt skewers are more likely to pop the balloon.
You may find that your balloons sometimes burst even if you follow the instructions. The audience will enjoy the entertainment so just laugh it off and try again!

Source:- http://www.physics.org/interact/physics-to-go/balloon-kebabs/index.html