Saturday, 19 August 2017

Li - Fi

Saturday, 24 June 2017

1. Babies have around 100 more bones than adults

Many of a baby’s bones fuse together as they grow

Babies have about 300 bones at birth, with cartilage between many of them. This extra flexibility helps them pass through the birth canal and also allows for rapid growth. With age, many of the bones fuse, leaving 206 bones that make up an average adult skeleton.
2. The Eiffel Tower can be 15 cm taller during the summer

Eiffel tower
Large structures are built with expansion joints which allow them some leeway to expand and contract without causing any damage.

When a substance is heated up, its particles move more and it takes up a larger volume – this is known as thermal expansion. Conversely, a drop in temperature causes it to contract again. The mercury level inside a thermometer, for example, rises and falls as the mercury’s volume changes with the ambient temperature. This effect is most dramatic in gases but occurs in liquids and solids such as iron too. For this reason large structures such as bridges are built with expansion joints which allow them some leeway to expand and contract without causing any damage.
3. 20% of Earth’s oxygen is produced by the Amazon rainforest

Amazon rainforest
The Amazon rainforest covers 5.5 million square kilometres (2.1 million square miles) of Earth

Our atmosphere is made up of roughly 78 per cent nitrogen and 21 per cent oxygen, with various other gases present in small amounts. The vast majority of living organisms on Earth need oxygen to survive, converting it into carbon dioxide as they breathe. Thankfully, plants continually replenish our planet’s oxygen levels through photosynthesis. During this process, carbon dioxide and water are converted into energy, releasing oxygen as a by-product. Covering 5.5 million square kilometres (2.1 million square miles), the Amazon rainforest cycles a significant proportion of the Earth’s oxygen, absorbing large quantities of carbon dioxide at the same time.
4. Some metals are so reactive that they explode on contact with water

Sodium exploding in water
This is what happens when sodium reacts with water

There are certain metals – including potassium, sodium, lithium, rubidium and caesium – that are so reactive that they oxidise (or tarnish) instantly when exposed to air. They can even produce explosions when dropped in water! All elements strive to be chemically stable – in other words, to have a full outer electron shell. To achieve this, metals tend to shed electrons. The alkali metals have only one electron on their outer shell, making them ultra-keen to pass on this unwanted passenger to another element via bonding. As a result they form compounds with other elements so readily that they don’t exist independently in nature.
5. A teaspoonful of neutron star would weigh 6 billion tons

Neutron star
Neutron stars contain some of the densest matter in the known universe

A neutron star is the remnants of a massive star that has run out of fuel. The dying star explodes in a supernova while its core collapses in on itself due to gravity, forming a super-dense neutron star. Astronomers measure the mind-bogglingly large masses of stars or galaxies in solar masses, with one solar mass equal to the Sun’s mass (that is, 2 x 1030 kilograms/4.4 x 1030 pounds). Typical neutron stars have a mass of up to three solar masses, which is crammed into a sphere with a radius of approximately ten kilometres (6.2 miles) – resulting in some of the densest matter in the known universe.
6. Hawaii moves 7.5cm closer to Alaska every year

Hawaii’s pace is comparable to the speed at which our fingernails grow.

The Earth’s crust is split into gigantic pieces called tectonic plates. These plates are in constant motion, propelled by currents in the Earth’s upper mantle. Hot, less-dense rock rises before cooling and sinking, giving rise to circular convection currents which act like giant conveyor belts, slowly shifting the tectonic plates above them. Hawaii sits in the middle of the Pacific Plate, which is slowly drifting north-west towards the North American Plate, back to Alaska. The plates’ pace is comparable to the speed at which our fingernails grow.
7. Chalk is made from trillions of microscopic plankton fossils

Chalk is made from single-celled algae that lived in Earth’s oceans for 200 million years.

Tiny single-celled algae called coccolithophores have lived in Earth’s oceans for 200 million years. Unlike any other marine plant, they surround themselves with minuscule plates of calcite (coccoliths). Just under 100 million years ago, conditions were just right for coccolithophores to accumulate in a thick layer coating ocean floors in a white ooze. As further sediment built up on top, the pressure compressed the coccoliths to form rock, creating chalk deposits such as the white cliffs of Dover. Coccolithophores are just one of many prehistoric species that have been immortalised in fossil form, but how do we know how old they are? Over time, rock forms in horizontal layers, leaving older rocks at the bottom and younger rocks near the top. By studying the type of rock in which a fossil is found palaeontologists can roughly guess its age. Carbon dating estimates a fossil’s age more precisely, based on the rate of decay of radioactive elements such as carbon-14.
8. In 2.3 billion years it will be too hot for life to exist on Earth

Our planet will eventually become a vast desert similar to Mars today.

Over the coming hundreds of millions of years, the Sun will continue to get progressively brighter and hotter. In just over 2 billion years, temperatures will be high enough to evaporate our oceans, making life on Earth impossible. Our planet will become a vast desert similar to Mars today. As it expands into a red giant in the following few billion years, scientists predict that the Sun will finally engulf Earth altogether, spelling the definite end for our planet.
9. Polar bears are nearly undetectable by infrared cameras

Polar bears
Polar bears keep warm due to a thick layer of blubber under the skin.

Thermal cameras detect the heat lost by a subject as infrared, but polar bears are experts at conserving heat. The bears keep warm due to a thick layer of blubber under the skin. Add to this a dense fur coat and they can endure the chilliest Arctic day.
10. It takes 8 minutes, 19 seconds for light to travel from the Sun to the Earth

It takes five and a half hours for the Sun’s light to reach Pluto.

In space, light travels at 300,000 kilometres (186,000 miles) per second. Even at this breakneck speed, covering the 150 million odd kilometres (93 million miles) between us and the Sun takes a considerable time. And eight minutes is still very little compared to the five and a half hours it takes for the Sun’s light to reach Pluto.
11. If you took out all the empty space in our atoms, the human race could fit in the volume of a sugar cube

Over 99.99999 per cent of atoms are empty space

The atoms that make up the world around us seem solid, but are in fact over 99.99999 per cent empty space. An atom consists of a tiny, dense nucleus surrounded by a cloud of electrons, spread over a proportionately vast area. This is because as well as being particles, electrons act like waves. Electrons can only exist where the crests and troughs of these waves add up correctly. And instead of existing in one point, each electron’s location is spread over a range of probabilities – an orbital. They thus occupy a huge amount of space.
12. Stomach acid is strong enough to dissolve razor blades

Stomach acid
Your stomach lining entirely renews itself every four days

Your stomach digests food thanks to highly corrosive hydrochloric acid with a pH of 2 to 3. This acid also attacks your stomach lining, which protects itself by secreting an alkali bicarbonate solution. The lining still needs to be replaced continually, and it entirely renews itself every four days.
13. The Earth is a giant magnet

 Earth's magnetic field
The Earth’s magnetic field is used by compass needles worldwide.

Earth’s inner core is a sphere of solid iron, surrounded by liquid iron. Variations in temperature and density create currents in this iron, which in turn produce electrical currents. Lined up by the Earth’s spin, these currents combine to create a magnetic field, used by compass needles worldwide.
14. Venus is the only planet to spin clockwise

Venus was likely knocked off course by a gigantic asteroid.

Our Solar System started off as a swirling cloud of dust and gas which eventually collapsed into a spinning disc with the Sun at its centre. Because of this common origin, all the planets move around the Sun in the same direction and on roughly the same plane. They also all spin in the same direction (counterclockwise if observed from ‘above’) – except Uranus and Venus. Uranus spins on its side, while Venus defiantly spins in the complete opposite direction. The most likely cause of these planetary oddballs are gigantic asteroids which knocked them off course in the distant past.
15. A flea can accelerate faster than the Space Shuttle

Fleas experience 100 g when they jump

A jumping flea reaches dizzying heights of about eight centimetres (three inches) in a millisecond. Acceleration is the change in speed of an object over time, often measured in ‘g’s, with one g equal to the acceleration caused by gravity on Earth (9.8 metres/32.2 feet per square second). Fleas experience 100 g, while the Space Shuttle peaked at around 5 g. The flea’s secret is a stretchy rubber-like protein which allows it to store and release energy like a spring

Friday, 23 June 2017

1. Water can boil and freeze at the same time
Seriously, it's called the 'triple point', and it occurs when the temperature and pressure is just right for the three phases (gas, liquid, and solid) of a substance to coexist in thermodynamic equilibrium. This video shows cyclohexane in a vacuum.
2. Lasers can get trapped in a waterfall
Oh my gosh, yes. Not only is this an incredible example of total internal reflection, it also shows how fibre optic cables work to guide the flow of light.
3. We've got spacecraft hurtling towards the edge of our Solar System really, really fast
We all know rockets are fast, and space is big. But sometimes when we're talking about how long it takes for us to get to distant parts of the Solar System (eight months to get to Mars, are you kidding me?) it can feel like our spacecraft are just crawling along out there.
This gif shows just how wrong that idea is by comparing the speed of the New Horizons probe, which flew past Pluto last year, to a 747 and SR-71 Blackbird.
4. An egg looks like a crazy jellyfish underwater
A cracked egg on land might make a big mess, but 18 metres (60 feet) below the surface of the ocean, the pressure on the egg is 2.8 times atmospheric pressure, and it holds it all together like an invisible egg shell. True story.  
5. You can prove Pythagoras' theorem with fluid
Not buying what your maths teacher is selling when they tell you a2 + b2 = c2? You can actually prove it with liquid.
6. This is what happens when a black hole swallows a star
As the star gets sucked up into the black hole, a huge jet of plasma is burped out, spanning hundreds of light-years. "When the star is ripped apart by the gravitational forces of the black hole, some part of the star's remains falls into the black hole, while the rest is ejected at high speeds," explains Johns Hopkins University researcher, Suvi Gezari
7. You CAN see without your glasses
According to MinutePhysics, all you need to do is make a pinhole with your hand, which will help you focus the light coming into your retina. Sure, it won't give you 20/20 vision, but it's a good start if you've left your glasses at home.
8. This is how a face forms in the womb
Embryonic development is an incredibly complex process that scientists are still just beginning to understand. But one thing researchers have been able to map out is how the embryo folds to create the structures of the human face in the womb. We could watch this all day.
9. Popping your knuckles isn't necessarily bad for you
One researcher popped the knuckles of one hand for 60 years but not the other, and found no discernible difference in the amount of arthritis between the two of them at the end of his experiment.
Find out more in this video from Vox:
10. A single solar flare can release the equivalent energy of millions of 100-megaton atomic bombs
And they're happening all the time.
11. Cats always land on their feet, thanks to physics
As Smarter Every Day demonstrated with this awesome slow-mo footage, cats actually use the two halves of their bodies separately to ensure rapid rotation (don't try this at home).
Watch the full video here:
12. You'd be better off surviving a grenade on land rather than underwater
Those balloons? That's what would happen to your lungs if an explosion went off near you underwater.
13. If you spin a ball as you drop it, it flies
I mean, it really flies. It's thanks to the Magnus effect, which occurs when the air on the front side of a spinning object is going the same direction as its spin, which means it gets dragged along with the object and deflected back.

Tuesday, 2 May 2017

Louis de Broglie, 

the Prince of Quantum

Then Louis de Broglie (15 August 1892 – 19 March 1987)—a novice scientist whose first degree was in history—thought otherwise: what if particles also behaved like waves? A century ago there were still questions as attractive as this, to which one might dedicate a doctoral thesis. And that is exactly what de Broglie did. After studying in depth for several years the bases of quantum physics established by Max Planck and Albert Einstein, he presented his thesis in 1924 with an important theoretical discovery: electrons behave as waves and, not only that, all particles and objects are associated with matter waves.
From Einstein’s support to experimental demonstration
This is the well-known de Broglie Hypothesis. Putting together Planck’s equations (quantization of energy: E = hν) and Einstein’s (special relativity: E = mc2), de Broglie calculated what the length of these matter waves associated with each particle would be, depending on its velocity and mass. Thus, according to de Broglie, our whole world is quantum, not just light—a conclusion so bold that it was immediately rejected by many physicists, and ignored by others.
Although in 1924 his scientific career was still short, when he presented his doctoral thesis the French physicist had already done other research, which had led him to clash with some of the most influential physicists of the moment. Not so with Einstein, who enthusiastically supported de Broglie’s conclusions, but even Einstein’s support was not enough to prove him right: his hypothesis had to be experimentally demonstrated.
Artistic rendition of the wave-particle duality. Credit: Timothy Yeo / CQT, National University of Singapore
If the electron were a particle that behaved like a wave, then it would have to show typical properties of waves, such as diffraction and interference. And then some very strange things would happen: for example, one electron would be able to traverse two different holes at the same time. This was demonstrated by the electron diffraction experiment of Davisson and Germer (1927), thus confirming the hypothesis of de Broglie, who was awarded the Nobel Prize for Physics in 1929, just five years after he had presented that bold doctoral thesis.
First step to the electron microscope
Few doctoral theses in the history of science have been so dazzling that they have reached the Nobel with the same work that gave the author the title of doctor. Another great example is that of Marie Curie. Incredibly, Louis de Broglie, with his first great scientific research, succeeded in laying one of the pillars of quantum physics: the wave–particle duality, which states that waves can behave like particles and vice versa. From his idea of matter waves was born wave mechanics, the new formulation of quantum physics that Schrödinger developed to apply to atoms and molecules. And admitting the wave properties of electrons was the basis for inventing the electron microscope (released in 1932), which allows us to see things much smaller than typical optical microscopes permit, because the wavelength of the electron is much shorter than that of photons of visible light.
For all these reasons we remember Louis de Broglie as the ‘prince of quantum’, although in the macroscopic world this scientist aristocrat only became a duke when his brother inherited the duchy de Broglie in 1960. By then, he had already received a multitude of recognitions for his scientific achievements, in addition to the Nobel Prize: he occupied seat 1 of the French Academy (1944), received two prestigious medals—Henri Poincaré (1929) and Max Planck (1938)—and was also the first recipient of the Kalinga Prize (1942), awarded by UNESCO to highlight outstanding contributions to the dissemination of science.
Pollen grains image taken on an electron microscope, an application of the de Broglie hypothesis. Credit: Dartmouth College
In addition, he was the first world-renowned scientist who called for countries to join forces to meet the great challenges of science in multinational laboratories. CERN (the European Organization for Nuclear Research) was born of this request, and his long life (he passed away at age 94) allowed him to see the exceptional achievements of this particle physics laboratory inspired by his scientific vision.

Einstein’s Love-Hate Relationship with Quantum Physics

If there is one scientist that almost anyone on the street could name, it is certainly Albert Einstein. As Jürgen Neffe recounted in his biography, Einstein was the first mass media scientist in history, promoted to the status of idol when the London newspaper The Times reported in 1919 that the theory of general relativity had been demonstrated by photographs of an eclipse of the Sun that revealed the curvature of the light of the stars, as the physicist had predicted.
Einstein received the Nobel Prize in Physics in 1921. But although his name has been mythically linked to his theory of relativity and his famous equation E = mc2, it was not this achievement that earned him the prize, but rather his explanation of the photoelectric effect, a phenomenon that Heinrich Hertz had observed in 1887. In 1905, Einstein described the mechanism by which light, when shone onto a metal surface, caused the ejection of discrete packages of energy, or quanta. The idea of ​​the quanta of light gave birth to a scientific revolution, which in the first decades of the twentieth century would give rise to the development of quantum physics.
A portrait of Albert Einstein in 1931. Credit: United States Library of Congress
Despite opening the way to a new physics, Einstein maintained a strange relationship of suspicion toward the views held by those leading this vibrant new field of science. Physicists such as Heisenberg or Schrödinger introduced with ease concepts that deviated from realism, such as that the actions of the observer determined the properties of the system, or that an atom could be intact and disintegrated at the same time (or that a cat could be alive and dead at the same time, as in Schrödinger’s most famous metaphorical example).
“God does not play dice”
But for Einstein, this dependence on probability suggested rather a lack of awareness of the laws involved in the governance of reality. “I am convinced that He [God] does not play dice,” he wrote in a letter to fellow physicist Max Born. On another occasion he asked his biographer Abraham Pais if he believed that the moon only existed when they looked at it.
In 1935, Einstein published, together with his colleagues Boris Podolsky and Nathan Rosen, a mental experiment that today we know as the EPR paradox. There exists the possibility that two particles share their properties, as if they were twins. But if, as the predominant school of thought on quantum physics defended, the action of an observer on one of them must influence the other, this would imply that there was an instantaneous communication between the two. This, argued Einstein and his collaborators, would break the unbreakable limit of the speed of light. There must therefore exist “hidden variables” according to which the system obeyed a sort of previous programming.
New York Times headline from 1935, regarding Albert Einstein and quantum theory. Credit: New York Times
In conclusion, quantum physics was not wrong, Einstein thought, it was simply incomplete. Just as general relativity had described a fabric of space-time that bound bodies together, eliminating the need for a gravitational action at a distance that had troubled Isaac Newton himself, Einstein believed that these hidden variables in the local environment of the particles before their separation would explain their later behaviour without resorting to what he called “spooky action at a distance.”
Discussions for decades
The EPR paradox fuelled lively discussions among physicists for decades, but it was in 1964 that the Northern Irish physicist John Stewart Bell ruled out the existence of hidden variables that could explain what we now know as quantum entanglement. As a consequence of Bell’s theorem, it was concluded that there was a non-local action at a distance between the particles.
An artist’s concept of quantum entanglement. Credit: YouTube/Stargazer
However, Bell’s statement did not settle the debate. In later years, other physicists have endeavoured to close the possible cracks (or loopholes) of quantum entanglement experiments that could open a path for other explanations within the realist view of Einstein. For example, critics argue that experiments may be vitiated by errors in the instrumentation or by biases of the researchers.
Among those physicists who have tried to shield quantum entanglement experiments against any possible loopholes is Ronald Hanson of the Delft University of Technology (The Netherlands). “The loophole-free tests of 2015, of which ours was the first, have closed all loopholes that can be closed,” Hanson tells OpenMind. “Does this prove the existence of entanglement? I would rather put it the other way round: the worldview of local causality, or local realism, has been proven false,” says Hanson.
In favour of quantum entanglement
But there are still those who argue that the short time that elapses between the generation of the particles and their measurement in the entanglement experiments could continue to support the idea of ​​programming. A recent experiment has tried to get rid of this possible loophole by measuring photons from stars up to 600 light-years away. It is highly unlikely, say the researchers, that the programming of particles could last for 600 years. However, for Hanson these so-called “cosmic” experiments of Bell do not provide a fundamental advance, since they do not rule out the influence of hidden variables.
According to David Kaiser, a physicist at the Massachusetts Institute of Technology and co-author of the latter study, “it is still a bit too early to proclaim that quantum entanglement has been “definitely proven.” The reason, says Kaiser, is that the latest experiments until now have closed the loopholes two at a time, but not all three at the same time. “But the recent progress in the field looks more compelling, in favour of quantum entanglement, than ever.”
Does this mean that the great Einstein finally failed in his mistrust of the quantum? Whether the current experiments would have made him change his mind or not, “who can say?” concludes Kaiser. “My view is that Einstein was one of the first to discover the non-local consequences of quantum theory. He did not believe those consequences could be true.” If he had had the opportunity to witness the latest developments, Hanson continues, “he would have accepted these as facts of nature; he was a very smart man!”

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Top 10: Science in 2016: Discover some of the most interesting science stories of 2016