My Science School

The Nobel Prize, which is awarded to those who “have conferred the greatest benefit to humankind”, is presented across a number of categories. Even though it recognises specific work done by people, the individuals receiving it more often than not make telling impressions in other ways too.

Take the case of Karl Ferdinand Braun, for instance. A German electrical engineer, Braun was a winner of the Nobel Prize. While he shared the 1909 Nobel Prize in Physics with Italian inventor Guglielmo Marconi "in recognition of their contributions to the development of wireless telegraphy", he contributed handsomely in other fields as well.

First big contribution

Born in 1850 at Fulda, where he was educated, Braun showed an early aptitude for mathematics. While his name is a homophone of brawn, a word that means physical strength, Braun had less to do with that and more to do with his brains. After studying at the Universities of Marburg and Berlin, Braun graduated in 1872. Along the way, he started focussing on physics.

He didn’t have to wait for long to make his first big contribution as he discovered the point-contact rectifier effect in 1874. The unipolar conduction (current flows freely only in one direction) of metal semi-conductor junctions that he discovered is even seen by many as the beginning of solid-state electronics.

Teaching career

Between his 1874 discovery and his invention of cathode-ray tube in 1897, Braun moved from strength to strength in his teaching career. Having started out as a teacher at a Gymnasium (school) in Leipzig, Braun went on to teach Physics at Marburg, Strasbourg, Karlsruhe and Tubingen in a little over 10 years. He returned to Strasbourg in 1895 as principal of the Physics Institute and remained there, even though he got other offers as well.

Braun’s invention of the cathode-ray tube, also known as the Braun’s tube, in 1897 built on the research done by fellow German physicist Heinrich Geissler and British chemist William Crookes. In order to study high-frequency, alternating-current electricity, Braun came up with the tube that now bears his name.

Short and slick paper

By removing air from a glass tube that contained an anode and a cathode, rays were emitted from the cathode on application of a voltage to both electrodes. Braun then found out not only how to focus these rays such that they struck a phosphor-coated screen on the opposite side, but also how to change the beam’s direction by placing an electromagnetic coil near the neck of the tube.

In a short, slick paper that was published in Annalen der Physik (one of the oldest scientific journals on physics now) on February 15, 1897, Braun clearly described the design and realisation of his tube. He didn’t stop there though, for, he also presented its application as an oscilloscope.

Recalls in Nobel Lecture

Braun dedicated his later years to research pertaining to radio and telegraphy, and it was his work in this field that eventually led to him winning the Nobel Prize. He didn’t forget his past though, as he recalled his invention in the following manner in his Nobel Lecture in 1909: “...I might perhaps recall an accessory which was of great use to me and other experimenters. I mean the cathode-ray tube which I described in 1897”.

While Braun died in 1918, the concept of using an electron beam for generating an image on a screen was made into a practical television system years later. In the middle and late 20th Century, TVs and other electronic display units with picture tubes based on Braun’s cathode-ray tube became commonplace everywhere. It stayed that way until they met their demise early in the 21st Century, when they were eventually replaced by other technologies.

 

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In 2016, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected space-time ripples after two black holes collided about 1.4 billion light-years from Earth. These space-time ripples are known as gravitational waves. LIGO first detected gravitational waves in 2015; 100 years after Einstein predicted their existence. The waves are a part of Einstein’s theory of general relativity.

The matter of Mercury’s orbit has been discussed earlier. It was general relativity which showed how Mercury’s motions were affected by the curvature of space-time. It is even possible for Mercury to be cast out of our solar system due to these changes after billions of years.

Gravitational Lensing is the phenomenon by which a massive object (like a galaxy cluster or a black hole) bends light around it. When astronomers observe that region through a telescope, they can see the objects directly behind the massive object, due to the light being bent. A commonly given example for this is Einstein’s Cross, a quasar in the constellation Pegasus. The light of the quasar was bent by a galaxy nearly 400 million light-years away in such a way that the former appears four times around the galaxy.

The first ever images of a black hole were shown by the Event Horizon telescope in April 2019. The photos once again gave confirmation of several facets of general relativity. It not only showed that black holes exist, but also the existence of a circular event horizon. This is a point at which nothing, including light, can escape.

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You might have come across laser pointers while attending a seminar or conference, or perhaps used it to play with your cat or dog. In the sixty years since physicists demonstrated the first laboratory prototype of a laser in 1960, it has been put to use in numerous ways from barcode readers to systems for hair removal.

The technology behind laser devices is based on Einstein’s Theory of Stimulated Emission. This theory came a year after the discovery of general relativity. Einstein imagined a bunch of atoms bathed in light. He had earlier discovered that atoms sitting in their lowest energy state can absorb photons and jump to a higher energy state. Similarly, higher energy atoms can emit photons and fall back to lower energies.

After sufficient time passes, the system attains equilibrium. Based on this assumption, he developed an equation that can be used to calculate what the radiation from such a system would look like. Unfortunately, Einstein’s calculations differed from the laboratory results. It was obvious that a key piece of the whole puzzle was missing.

Einstein resolved this by guessing that photons like to march in step. This would mean that the presence of a bunch of photons going in the same direction will increase the probability of a high-energy atom emitting another photon in that direction. Einstein labelled this process stimulated emission. He was able to rectify the disparity between his calculations and the observations by including this in his equations.

A laser is a device to harness this phenomenon. It excites a bunch of atoms with light or electrical energy. The photons released as a result are channelled precisely in one direction. Lasers are used in delicate surgery or industrial processes that require precision.

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Many of the everyday mechanisms  we take for granted, such as automatic lighting of street lamps as daylight fades, how the elevator doors remain open when there is someone in the way, the device that regulates printer toner, and breathalyser tests- all of these use photoelectric cells that are based on Einstein’s theories.

Photoelectric cells, originally used to detect light, used a vacuum tube containing a cathode (to emit electrons) and an anode (to gather the resulting current). Modern versions of these “phototubes” have advanced to semiconductor-based photodiodes. These find applications in solar cells and fibre optics telecommunications.

Photomultiplier tubes are a variation of the phototube. Devices like solar panels that turn light into electricity are possible because of the photoelectric effect.

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Wall Street in New York is the home of the New York Stock Exchange. An army of mathematicians are employed there to analyze and predict the stock price variations. Their employers can potentially earn millions of dollars based on their predictions about which way the prices will jump.

Mathematicians however say that stock markets follow a random walk. This means that unless some spectacular event occurs, the prices have the same chances of decreasing and increasing at the end of any day. If patterns do exist, they will be elusive and difficult to find, which is why financial mathematicians are paid huge sums.

Some of the intricate mathematics used for stock market analyses can be traced back to Einstein. He developed the fluctuation-dissipation   theorem to explain the random movement of particles found in liquids or gases.

This movement called ‘Brownian motion’ was first observed by the Scottish biologist Robert Brown. Brownian motion is highly similar to the price fluctuations seen in stock markets. The similarity was observed in 1970 and since then it has been used on Wall Street. Einstein’s paper on Brownian motion is still used as the basis for certain stock market predictions.

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Einstein’s General Theory of Relativity has predominantly found applications in astronomy through gravity waves, big bangs and black holes. One of its rather unexpected applications was in the multi-billion-dollar industry centred around the Global Positioning System (GPS).

All GPS navigators including Google Maps work by measuring the distance from one point on Earth to one of the satellites orbiting our planet. Though GPS was originally developed with military use in mind, it has since become an inherent part of everyday life.

GPS is based on a collection of 24 satellites, each carrying a precise atomic clock. A hand-held GPS receiver which detects radio emissions from any satellite overhead can find the latitude, longitude and altitude with accuracy up to 15 metres and local time to 50 billionths of a second. The clocks on satellites are ahead of those on Earth by 38,000 nanoseconds. The reason for this is explained by the General Theory of Relativity. Though it may appear as an inconsequential amount of time, if these nanoseconds are not taken into account, GPS systems would be highly inaccurate.

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Einstein received a paper from Indian scientist Satyendra Nath Bose in 1924. The paper was on a new perspective: to think of light as a gas filled with indistinguishable particles. Einstein recognized the relevance of the paper. He translated it to German and submitted it on behalf of Bose to the famous journal Zeitschrift fur Physik. Bose went to Europe and worked with Einstein at the X-ray and crystallography laboratories there.

Einstein worked with Bose to extend his idea to atoms and they predicted a new state of matter which came to be called the Bose-Einstein Condensate. A Bose-Einstein Condensate is a dense collection of particles with integer spin known as Bosons.

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Einstein was primarily in pursuit of a universal field theory after the General Theory of Relativity. He engaged in a series of unsuccessful attempts to further generalize the theory of gravitation in order to unify and simplify the fundamental laws of physics, in particular, gravitation and electromagnetism.

This ‘theory of everything’ was supposed to refute the quantum theory. Though he published a paper in 1929 which supposedly had such a theory, Einstein himself had to acknowledge the errors in his argument.

Einstein remained in the cocoon of his research, largely ignoring other developments in physics and quantum theory. He however, did a few collaborations with the Indian scientist Satyendra Nath Bose, the Austrian Erwin Schrodinger and his Hungarian former student Leo Szilard.

In the 1930s he worked together with Russian physicist Boris Podolsky and the Israeli physicist Nathan Rosen. Nevertheless, his search for the ‘theory of everything’ and his distrust of the quantum theory consumed him in his later years.

Einstein had also made contributions to the development of the quantum theory. The concept of light quanta (photons) was used by him in 1905 to explain the Photoelectric Effect and to develop the quantum theory of specific heat.

Despite playing a main role in its development, Einstein regarded the quantum theory only as a temporarily useful structure.

His efforts were primarily in formulating the unified field theory which he believed would turn out to be the reason behind quantization of energy and charge. He felt that the quantum theory lacked the simplicity and beauty befitting a rational interpretation of the universe.

He engaged in a series of private debates with physicist Niels Bohr about the validity of the quantum theory later on. The 1920s witnessed his prolonged public debates with Niels Bohr and Werner Heisenberg over quantum mechanics. Einstein was rather lukewarm about the quantum theory even from a philosophical standpoint, saying in 1926 that he was convinced God does not throw dice. However, Bohr showed the ambiguities in Einstein’s reasoning.

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The Nobel Prize in Physics 1921 was awarded to Albert Einstein “for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect.”

Albert Einstein received his Nobel Prize one year later, in 1922. During the selection process in 1921, the Nobel Committee for Physics decided that none of the year’s nominations met the criteria as outlined in the will of Alfred Nobel. According to the Nobel Foundation’s statutes, the Nobel Prize can in such a case be reserved until the following year, and this statute was then applied. Albert Einstein therefore received his Nobel Prize for 1921 one year later, in 1922.

However, Einstein did not attend his prize giving. Though he was informed that he was to receive the prize, he continued with a lecture tour of Japan.

Einstein has published four papers on the general theory of relativity. In the third paper, he used general relativity to explain why Mercury’s closest point to the Sun (its perihelion) is erratic.

Gravitational influence of the Sun and other planets was not sufficient explanation for this movement. Some even went as far as to suggest in the 19th century that a new planet, Vulcan, orbiting close to the Sun was the reason! But this was disproved as Einstein succeeded in calculating the shift in Mercury’s perihelion using the general theory of relativity.

The theory not only explained previously unexplained phenomena, it could even predict events that have not occurred yet. In 1919, the theory was validated again when Sir Arthur Eddington, secretary of the Royal Astronomical Society of London travelled to the island of Principe off the coast of West Africa. There, he had the perfect view of the Sun during a total eclipse.

The light emitted from a certain strand was measured and it was found that the light was deflected, or bent, by just the amount that Einstein had predicted. Einstein’s fame skyrocketed after this.

The General Theory of Relativity predicted that the space-time around Earth would be warped and twisted due to Earth’s rotation. The theory gave a new framework for all of physics and proposed new concepts of space and time.

In 1907, Einstein had certain realizations about his theory. He understood that special relativity could not be applied to gravity or to an object undergoing acceleration. Consider a person sitting inside a closed room on Earth. That person experiences Earth’s gravity. Now imagine if the same room was placed in space, away from the gravitational influence of any object.

If it is given an acceleration of 9.8 m/s2 (same as Earth’s gravitational acceleration), the person inside the room won’t be able to tell whether he is feeling gravity or uniform acceleration. This idea laid the foundation of the General Theory of Relativity.

Einstein’s next question was how light would behave in the accelerating room. When we shine a torch across the room, the light looks like it is bending forward. This is because the floor of the room would be coming up to the light beam at an ever-faster speed, so the floor could catch up with the light. As gravity and acceleration are equivalent, light would bend in a gravitational field.

It took Einstein several years to find the correct mathematical expression of these ideas. In 1912, his friend, mathematician Marcel Grossman, introduced him to the tensor analysis of some mathematicians. This helped him. After three more years of work, the foundations of this theory were laid in the four papers he published in 1915.

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Einstein was not the first scientist to observe and study the photoelectric effect. However, he was the first to properly understand the nature of light and draw the correct assumptions from it. Physicists James Clerk Maxwell in Scotland and Hendrik Lorentz in the Netherlands had already proved the wave nature of light in the late 1800s. This was proven by seeing how light waves demonstrate interference, diffraction and scattering- which are common to all waves including water.

Einstein’s 1905 argument that light behaves as sets of particles (initially called quanta and later ‘photon’) was contradictory to the classical description of light as a wave. A completely new model of light was needed to explain the phenomenon. Einstein developed a model for this purpose and according to this, light sometimes behaved as particles of electromagnetic energy or photons. Though others had presented this theory before Einstein, he was the first to explain why it occurred and consider its potential.

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Photoelectric effect is the emission of electrons from a substance when electromagnetic radiations fall on it. For instance, when light falls on a metal plate, electrons are ejected.

Light with energy above a particular point frees electrons from the surface of the solid metal. Each photon (particle of light) collides with an electron and uses some of its energy to remove the electron. Photon’s remaining energy transfers to the free negative charge which is called a photoelectron. This was a discovery that revolutionized modern physics as it clarified many doubts regarding the nature of light.

The photoelectric effect proposed by Einstein in 1905 remains valuable in various areas of research such as material science and astrophysics. It is also the basis of many useful devices. The ‘electric eye’ door openers, light metres used in photography, solar panels and Photostat copying are all applications of the photoelectric effect.

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The equation E=mc2 is perhaps one of the most famous scientific equations of all time. As mentioned previously, this equation came up in the fourth paper Einstein published in 1905. It states that energy is equal to the product of mass and the square of the speed of light. Which means that, matter can transform into energy if it moves fast enough.

One of the factors making this equation so remarkable is that it establishes a connection between hitherto seemingly unrelated entities. Before Einstein’s fourth paper was published, time and Space, and mass and energy were separate entities.

Through establishing the concepts of space-time and E=mc2, he formulated his theory of relativity. Though special relativity is one of the last intuitive theories ever made in the history of science, it turned out to be a crucial one for physics.

Scientists proved all the theories Einstein proposed in 1905. The uses of these theories did not always turn out to be for the benefit of mankind. Changing matter into energy is the principle behind the generation of nuclear energy which provides electricity to millions of people.

However, the same principle was used to split atoms and release the destructive energy of atom bombs. Thus, the equation which is a blessing in electricity production and medical diagnostic tools also became the foundation of the nuclear bomb.