Fun Physics: How to find out if an egg is boiled or raw ?

Without breaking the shell, how can we find out whether an egg is boiled or not ?

Mechanics gives us the answer. The whole trick is that a boiled egg
spins differently than a raw one. Take the egg, place it on a flat plate and spin it (Fig. 39). A cooked egg, especially a hard-boiled one, will revolve much faster and longer than a raw one; as a matter of fact, it is hard to make the raw egg even turn. 

The explanation lies in the fact that while a hard-boiled egg revolves as one whole. In a raw egg - the inside liquid do not rotate with the outside shell and so it puts the brake on the egg's motion. 

Also the boiled and raw eggs stop spinning differently. When you touch a spinning boiled egg with a finger, it stops at once. But a raw egg will continue spinning for a while. The reason for this is "inertia" of the liquid inside the raw egg - the liquid of the raw egg still continue moving even after the solid shell is brought to a state of rest. 

Lyrebird: World's weirdest bird that mimics Chainsaw, Car Alarm and More

Lyrebird is found in Australia

Lyre is a musical instrument of ancient Greece. Lyrebird's spectacular tail of fanned feathers, when spread out in display, looks like a lyre.

Lyrebirds are capable of imitating almost any sound. Mixed in with their own calls, clicks and song, you will usually hear them mimicking loud clear sounds made by other birds and mammals - including humans. They have been heard to mimic the sounds of chainsaws, horns, alarms and even trains. They sing throughout the year, and scientists think that the mimicry helps them to vocally set out their territory and defend it from other lyrebirds.

Video: Lyre Bird sings like a chainsaw! 

Video: Lyrebird mimicking children toy gun and other sounds

Now, it is your turn to find out and share one bird that mimics or makes unique and interesting sounds.

Riddle: Who is the greatest of the gods ?

A king was called "Pharaoh" is ancient Egypt. A Pharaoh asked - 
"Who is the greatest of the gods ?"

"I am not" - said Horus (Horus is a god of the sky and kingship)
"Anubis is" - said Isis (Isis is a goddess of health, marriage, and wisdom)
"Isis is lying" - said Anubis (Anubis is protector of the dead)

The Pharaoh knew that only one of the gods is telling the truth - the other two were lying. Who is the greatest of the gods ?

Robotics: How to water proof electronics

This is a continuation of the hydroplane robotics video.

Robotics: Constructing a hydroplane

Templates (source : http://www.rcgroups.com/forums/thumbgallery.php?t=1647267&do=threadgallery&type=files&group=none&starter=no) 

Micro Photography

Micro photography uses a special "micro" lens that captures finer details of an object.

Try to stand up

You'd think I was joking if I told you that you wouldn't be able to get up from a chair provided you sat on it in a certain way, even though you wouldn't be strapped down to it. Very well, let's have a go. Sit down on a chair in the same way the boy in Fig. 13 is sitting. Sit upright and don't shove your feet under the chair. Now try to get up without moving your feet or bending forward. You can't, however hard you try. You'll never stand up until you push your feet under the chair or lean forwards. Before I explain, let me tell you about the equilibrium of bodies in general, and of the human body in particular. A thing will not topple only when the perpendicular from its centre of gravity goes through its base. 







The leaning cylinder in Fig. 14 is bound to fall. If, on the other hand, the perpendicular from its centre of gravity fell through its base, it wouldn't topple over. The famous leaning towers of Pisa and Bologna, or the leaning campanile in Arkhangelsk (Fig. 15), don't fall, despite their tilt, for the same reason. The perpendiculars from their centres of gravity do not lie outside their bases. Another reason is that their foundations are sunk deep in the ground.


You won't fall only when the perpendicular from your centre of gravity lies within the area bound by the outer edge of your feet (Fig. 16). That is why it is so hard to stand on one leg and still harder to balance on a tight-rope. Our "base" is very small and the perpendicular from the centre of gravity may easily come to lie outside its limits.  Porters who carry loads on their heads are well-built a point, I presume, you have noticed. You may have also seen exquisite statues of women holding jars on their heads. It is because they carry a load on their heads that these people have to hold their heads and bodies upright. If they were to lean in any direction, this would shift the perpendicular from the centre of gravity higher than usual, because of the head-load, outside the base and unbalance them. 

Back now to the problem I set you at the beginning of the chapter. The sitting boy's centre of gravity is inside the body near the spine about 20 centimeters above the level of his navel. Drop a perpendicular from this point. It will pass through the chair behind the feet. You already know that for the man to stand up it should go through the area taken up by the feet. Consequently, when we get up we must either bend forward, to shift the centre of gravity, or shove our feet beneath the chair to place our "base" below.

Do Animals have language ?

All animals communicate. But do they have language? Michele Bishop details the four specific qualities we associate with language and investigates whether or not certain animals utilize some or all of those qualities to communicate.

Riddle: Find logical mistake in the sentence

Mary, in 1925, told her friend, "My husband died in World War I."

Riddle: Color of the bear

If you are sitting in a house with all windows facing south and there is a bear in the window, what is the color of the bear ?

Super heroes of metal world

The word "metal" means strength; but strength can be measured in different ways just like superheroes have different powers.

Malleability

Malleability is the ability of a metal to be hammered into thin sheets. Gold and silver are highly malleable. When a piece of hot iron is hammered it takes the shape of a sheet. The property is not seen in non-metals.

Silver is a transition metal. It has the highest electrical conductivity of any element and the highest thermal conductivity of any metal. The metal occurs naturally in its pure, free form, as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc refining. It has long been valued as a precious metal

Ductility/Tensile Strength
Ductility is a solid material's ability to deform when it is pulled from both ends; this is often characterized by the material's ability to be stretched into a wire. Again gold is one of the most ductile metals.

Gold - its a very soft and beautiful metal coveted for thousands of years chemical properties of gold.

Hardness
Hardness is a measure of how resistant solid matter is to various kinds of permanent shape change when a compressive force is applied.

Titanium is classified as a transitional metal. Titanium is the ninth most abundant element in Earth’s crust. It is almost always present in igneous rocks and their sediments. Pure titanium is a lustrous white metal. It is strong, light with low density, and has excellent corrosion resistance. Titanium is as strong as steel but 45 percent lighter. It is 60 percent heavier than aluminum, but twice as strong.

Toughness
The toughness of a material is the maximum amount of energy it can absorb before fracturing, which is different from the amount of force that can be applied.

Molybdenum is tough metal used in many types of power tools chemical properties of molybdenum.

Corrosion resistance
Corrosion is a process of gradual destruction of metal due to oxygen(process is called - oxidation). 

Zinc is a metallic chemical element. It is the 24th most abundant element in the Earth's crust and has five stable isotopes. Corrosion-resistant zinc plating of steel is the major application for zinc. Other applications are in batteries and alloys, such as brass

Shear strength
Shear strength represents how hard you can try to cut it without it breaking. When you cut a paper with scissors, the paper is failing in its shear strength.

iron is used to make an alloy called "steel" which has very high shear strength. 

How smart are dolphins?

The video below shows bottlenose dolphins' hunting strategy explained in the video above

Video 1 source : ed.ted.com

What is religion ?

What do YOU think a religion is ?

Mouse eating cat

All of the 13 mice in the figure are doomed to be eaten by the cat. But the cat wants to eat them in a certain order. The cat eats one mouse and then counts around the circle in the direction in which the mice are looking. When it gets to 13 it eats the next mouse and starts counting again. Which mouse must the cat eat first so that the white mouse is eaten last?

Source: Fun with Maths and Physics by Perlman 

One word sentences

Certain words in english can be a noun, a proper noun, an adjective and also a verb. Using such words in the same sentence creates confusion in understanding the meaning - this is called "lexical ambiguity". 

'Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo’ is a grammatically correct sentence. How? Emma Bryce explains how this and other one-word sentences illustrate some lexical ambiguities that can turn ordinary words and sentences into mazes that mess with our minds.

How does potato battery work: explanation

Now you have made the potato battery, lets see how it really works. The key concepts are;

• Electrolyte - A medium through which electrons(flow of electrons is "electricity") can travel
• Electrodes 
• Anode - Positively charged electrode, in our experiment Copper is anode
• Cathode - Negatively charged electrode, in our experiment Zinc is cathode

How to make a battery using potato

The Speed of a Train

You are traveling in a train and want to find its speed, could you work it out from the clatter (sound) of the wheels?

Hexaflexagon

Hexaflexagon is a cool little project with paper that all of you will enjoy making.

Watch this video that explains the history of hexaflexagon and also how to make it. Let me know if you find hard to follow this video - I will tell you a trick on how to reduce the speed at which the video plays.

If it was hard to follow the video above, the link below shows step by step method to make a hexaflexagon

http://www.wikihow.com/Fold-a-Hexaflexagon

What is meteor shower ?

A meteoroid is a small body moving in the solar system. This will be called a meteor if it entered in earth's atmosphere - this meteor travels towards earth at 25,000 to 160,000 miles per hour. This meteor becomes brightly visible due to the heat and light it emits at this speed. This light and heat leaves a trail which can be seen in a night sky. This is what many people call "a shooting star" 

When earth passes close to a comet or astroid belt, many such meteors can be seen in the night sky falling at the same time - this is called meteor shower.

Every year in month of August earth passes through the path of a comet called swift-tuttle. This is a best time to watch meteor shower if you are in northern hemisphere.

Story of living: Part 2 - DNA the book of You !

Your body is made of cells -- but how does a single cell know to become part of your nose, instead of your toes? The answer is in your body's instruction book: DNA. Joe Hanson compares DNA to detailed manual for building a person out of cells -- with 46 chapters (chromosomes) and hundreds of thousands of pages covering every part of you.

In this video learn how a DNA stores all the information needed for a human body. 

Source: ed.ted.com 

Why do honeybees love hexagons?

Bees have been producing honey as they do today for at least 150 million years. Bees produce honey as food stores for the hive during the long months of winter when flowers aren't blooming and therefore little or no nectar is available to them.

Honeycombs are made up of hexagonal wax cells. This video describes why bees may have evolved in making hexagonal cells over any other shape. 

Enjoy ! :)

Fun Physics: Banana kick in Football

In 1997, Brazilian football player Roberto Carlos set up for a 35 meter free kick with no direct line to the goal. Carlos’s shot sent the ball flying wide of the players, but just before going out of bounds it hooked to the left and soared into the net. 

How did he do it? Erez Garty describes the physics behind one of the most magnificent goals in the history of football.

Story of living - Part 1

All living beings - bacteria, animals, humans, plants - are made of cells. Amoeba is a single cell bacteria; human and most of the living world is made up of many cells. A human body has around 200 different cells. Each body part - hair, skin, blood, bone, heart, liver, etceteras - is made up of a different type of cell. Each type of cell has certain physical properties and knows its function. 

How does a cell know its function - this information is stored inside the cell in the form of DNA(Deoxyribonucleic acid is a molecule). This information tells cell how to work. 

DNA looks like this, 

How do animals and plans grow ? - by cell division. One cell divided into two, two into four, four into eight and so on. This how babies grow into adults, seeds grow into trees. Since amoeba is a single celled organism, division of that single cell means the parent amoeba dying and two young amoebae being born.


Multiple cells form a tissue, group of tissues form a organ and all the organs together form an organism.

Watch this amazing video that shows the cells inside human body

What is "global climate change" ?

What is global climate change 

Is the climate of the whole Earth really changing?

Yes! Earth has been getting warmer—and fast.
Global climate is the average climate over the entire planet. And the reason scientists and folks like you are concerned is that Earth's global climate is changing. The planet is warming up fast—faster than at any time scientists know about from their studies of Earth's entire history.

What is climate?

"Climate" describes conditions over the long term and over an entire region.
Climate is the big picture. It is the big picture of temperatures, rainfall, wind and other conditions over a larger region and a longer time than weather. For example, theweather was rainy in Phoenix, Arizona, last week. But this city usually gets only about 7 inches of rain each year. So the climate for Arizona is dry. Much of Southern California also has a dry, desert climate. Brazil has a tropical climate, because it's warm and rains there a lot.

These two types of vegetation reflect their climates—one very wet and one very dry.

What is weather?

TV weather reporters need all the information they can get in order to predict the weather for just a few days.

Weather is local and temporary.
On our own Earth, we cannot control weather by turning a thermostat up to make it warmer or down to make it cooler. The best we can do is try to predict the weather. Weather scientists, called meteorologists, try to foresee what's going to happen next.

It looks like this storm is getting ready to create a tornado.

Is that big black cloud going to let loose over San Francisco, or wait until it gets to Sacramento? Will that new storm forming in the Atlantic Ocean turn into a hurricane? Conditions are just right for tornadoes. Will any form? And where might they touch the ground and cause trouble?
Weather happens at a particular time and place. Rain, snow, wind, hurricanes, tornadoes—these are all weather events.

Do we care if Earth is getting warmer?

The whole Earth as seen from 22,300 miles away, out in space.

Yes, we care! After all, Earth is our spaceship.
It carries us on a 583-million-mile cruise around the Sun every year. It even has its own "force field." Earth has a magnetic field that protects us from killer radiation and brutal solar wind. For its life-support system, Earth has all the air, water, and food we need.
Just like astronauts on a long space voyage, we need to monitor all our "ship's" vital functions and keep our Earth "ship shape."

Earth is a magnificent spaceship. Its magnetic field is an "invisible force field" protecting us from the Sun's stormy blasts. And Earth gives us everything else we need to live.

Does what we do matter?

Earth's fate is in our hands.

Everything that happens here affects something over there.
Earth has its own control system. The oceans, the land, the air, the plants and animals, and the energy from the Sun all affect each other to make everything work in harmony. Nothing changes in one place without changing something in another place. The overall effect gives us our global climate.

What is making Earth's climate warmer?

How can we take better care of our planet?

Scientists have discovered that humans are causing this warming.
But how do they know that? What are we doing that could cause the whole planet to get warmer? And how could warming happen so fast? What will happen to people and other living things if the planet keeps getting warmer? And what can we do to slow down or stop the warming?

How do we know the climate is changing ?

So what if Earth gets a tiny bit warmer?

The sky is still blue. Trees are still green. Wind still blows. Clouds are still white and fluffy. Rain still pours from the sky. Snow falls and it still gets really cold sometimes in some places. Earth is still beautiful.

Left to right: Virgin River in Zion National Park, Utah; dirt road through a dry valley in Onyx, California; Bryce Canyon National Park, Utah; polar bears in the Arctic.

So what is the problem? What is the fuss about climate change and global warming?
Well, after observing and making lots of measurements, using lots of NASA satellites and special instruments, scientists see some alarming changes. These changes are happening fast—much faster than these kinds of changes have happened in Earth's long past.

All these satellites, plus a lot more, are studying Earth and all the changes happening with the air, ocean, land, and ice.

Polar bear clings to a small chunk of melting ice surrounded by open sea.

Global air temperatures near Earth's surface rose almost one and one-half degrees Fahrenheit in the last century. Eleven of the last 12 years have been the warmest on record. Earth has warmed twice as fast in the last 50 years as in the 50 years before that.
One and one-half degrees may not seem like much. But when we are talking about the average over the whole Earth, lots of things start to change.

Why is Earth getting warmer?

Why is Earth getting warmer? Here's one clue: As the temperature goes up, the amount of carbon dioxide, or CO2, in the air goes up. And as the carbon dioxide goes up, the temperature goes up even more.
Carbon dioxide is a greenhouse gas. That means it traps heat from Earth's surface and holds the heat in the atmosphere. Scientists have learned that, throughout Earth's history, temperature and CO2levels in the air are closely tied.

This graph shows carbon dioxide levels over the past 450,000 years. Notice the sharp increase starting around 1950.
Ref: http://www.ncdc.noaa.gov/paleo/globalwarming/temperature-change.html.)

This graph shows CO2 levels over the past 450,000 years. As you can see, for 450,000 years, CO2 went up and down. But CO2 levels never rose over 280 parts per million until 1950. But then something different happens and CO2 increases very fast. At the end of 2012, it is 394 parts per million*. Why?
Because of us and our fossil fuels.
Now, let's look at that graph again, but adding the temperatures for that same period of Earth's history.

This graph shows how carbon dioxide and temperature have risen and fallen together in Antarctica over the past 400,000 years.
Ref: http://www.epa.gov/climatechange/science/pastcc_fig1.html.

You can see how CO2 levels change with temperature. Look at what it is doing now.
Yipes!

---

* Reference NOAA's Earth system Research Laboratory, Global Monitoring Division, http://www.esrl.noaa.gov/gmd/ccgg/trends.

How do we know what Earth was like long ago?

A big part of the answer is ice cores.
In Antarctica, scientists have drilled down two miles below the surface and brought up samples of the ice. These samples are called ice cores. It's like what you get if you plunge a drinking straw into a slushy drink and pull it out with your finger over the end of the straw. What you will have inside the straw is an ice core—although a very slushy one.
The layers in an Arctic ice core are frozen solid. They give clues about every year of Earth's history back to the time the deepest layer was formed. The ice contains bubbles of the air from each year. Scientists analyze the bubbles in each layer to see how much CO2 they contain. Scientists can also learn about the temperatures for each year by measuring relative amounts of different types of oxygen atoms in the water. (Remember, water is H2O: two hydrogen atoms, and one oxygen.)

(Clockwise from top left) Ice coring machine, hole in ice, pulling ice core from machine, man with hands on ice core tube in ground, scientist holding up ice core in triumph, man hand drilling ice core.

Other scientists study cores of sediment from the bottom of the ocean or lakes. Or they study tree rings and layers of rocks to give them clues about climate change throughout history. They compare all their findings to see if they agree. If they do, then their findings are accepted as most likely true. If they don't agree, they go back and figure out what is wrong with their methods.

Left to right: Scientist kneels next to a tree core showing its many years of rings; cross-cut tree trunk showing its rings; scientist studies tree specimen with microscope and other instruments.

In the case of Earth's climate history, the facts agree from a lot of different kinds of studies.

How can so little warming cause so much melting?

Water can soak up a lot of heat. When the oceans get warmer, sea ice begins to melt in the Arctic and around Greenland. NASA's Earth satellites show us that every summer some Arctic ice melts and shrinks, getting smallest by September. Then, when winter comes, the ice grows again.
But, since 1979, the September ice has been getting smaller and smaller and thinner and thinner. Check out the Climate Time Machine and watch the ice shrink.

Earth's Arctic area: On left, the ice cap covers a large part of the Arctic Ocean. this image is an average of the ice extent during Septembers of 1979-1981. On right, however, a much smaller area is covered by ice in September 2007.
Ref: http://www.nasa.gov/topics/earth/sea_ice_nsidc.html.

See how much three glaciers have shrunk over time. Columbia Glacier from 1980 - 2005; Arapaho Glacier from 1898 to 2003; and Grinnell Glacier from 1940 - 2006.

Glaciers are another form of melting, shrinking ice. Glaciers are frozen rivers. They flow like rivers, only much slower. Lately, they have been speeding up. Many of them flow toward the ocean, then break off in chunks--sometimes huge chunks. In places such as Glacier National Park, the glaciers are melting and disappearing. The air is getting warmer, and less snow is falling during winter to renew the melted parts of the glaciers.

Doesn't rising sea level just bring us closer to the beach?

As more sea ice and glaciers melt, the global sea level rises. But melting ice is not the only cause of rising sea level. As the ocean gets warmer, the water actually expands! Sea level has risen 6.7 inches in the last 100 years. In the last 10 years, it has risen twice as fast as in the previous 90 years. If Greenland's ice sheet were to melt completely, sea level all over the world would rise by 16-23 feet (5 to 7 meters). The map above of the southeastern U.S. shows in red the area that would be under water if sea level were to rise by 20 feet (6 meters).
Double yipes!

Play with the Climate Time Machine to see what rising sea level will do to other parts of the world.

How does climate change affect other species?

Life is a web, with every strand connected to every other strand. One species of plant or animal changes, and a whole chain of events can follow involving many other species.

This caribou mom looks a little thin. Photo: Al Seib/Los Angeles Times.

For example, herds of caribou live in cold, Arctic locations. Caribou hate mosquitoes. In the past few years, warmer temperatures in summer have allowed mosquito populations to explode. So the caribou spend a lot more energy swatting away the mosquitoes. All this swatting leaves the caribou less energy to find food and prepare for the next long winter. Female caribou are especially troubled because it takes so much energy to give birth and raise their young.

This marmot may have awakened from his winter nap too early, but he still seems to be getting plenty to eat.

Animals that hibernate in the winter also suffer from warming temperatures. Marmots, chipmunks, and bears are waking up as much as a month early. Some are not hibernating at all. These animals can starve if they stay awake all winter, because they can't find enough food. If they wake up too early because it feels warm enough to be spring, the days may not yet be long enough to signal the plants to start their spring growth. So, again, the wakeful animals go hungry.
Many trees in the Western U.S. are already suffering from climate change. Droughts leave trees thirsty and stressed. Pine trees need cold winters, too. With warmer, drier conditions, the trees are more likely to become infected with insects. These bugs bore into the trees and lay their eggs. Eventually, they kill the tree. Some forests in the West have lost over half their trees already to pine beetles. When the forest is gone, birds and small mammals that lived there have to find new homes--if they can.

This forest is infected with pine beetles. The close-up is the inside of a tree infected with the beetles.

There are many more plant and animal species and communities struggling to adapt to the rapidly changing climate.

September 2009 Station Fire near Los Angeles.

This satellite image shows the "Station Fire" of September 2009, which burned one-fourth of the Angeles National Forest (near Los Angeles). In the future, drought conditions and record hot temperatures could make fires like this more frequent and intense.

Source: http://climatekids.nasa.gov/