AdSense

Search This Blog

Labels

Thursday, November 5, 2015

Genius Albert Einstein's theory of relativity is 100 years old !!

I have been posting regularly on the attraction to yellow metal [women would read that as jewellery – while to men it is Gold]…. Most metals are shiny because the electrons in the atoms jump from different energy levels, or "orbitals." Some photons that hit the metal get absorbed and re-emitted, though at a longer wavelength. Most visible light, though, just gets reflected.Gold is a heavy atom, so the inner electrons are moving fast.  Longer wavelengths of light mean that some of the visible light that would usually just be reflected gets absorbed, and that light is in the blue end of the spectrum. The relativistic effect on gold's electrons is also one reason that the metal doesn't corrode or react with anything else easily.Gold has only one electron in its outer shell, but it still is not as reactive as calcium or lithium.

There are many things in life, which we read with awe-inspiration, but do not understand much.  The theory of relativity could easily be on top of the list for ordinary mortals like me.

Albert Einstein, the famous German physicist was born in 1879. He developed the general theory of relativity, one of the two pillars of modern physics (alongside quantum mechanics).   Einstein is best known in popular culture for his mass–energy equivalence formula E = mc2.   He received the 1921 Nobel Prize in Physics for his "services to theoretical physics", in particular his discovery of the law of the photoelectric effect, a pivotal step in the evolution of quantum theory.

He was visiting the United States when Adolf Hitler came to power in 1933 and, being Jewish, did not go back to Germany, where he had been a professor at the Berlin Academy of Sciences. He settled in the U.S., becoming an American citizen in 1940.  On the eve of World War II, he endorsed a letter to President Franklin D. Roosevelt alerting him to the potential development of "extremely powerful bombs of a new type" and recommending that the U.S. begin similar research. This eventually led to what would become the Manhattan Project. Einstein supported defending the Allied forces, but largely denounced the idea of using the newly discovered nuclear fission as a weapon. Einstein published more than 300 scientific papers along with over 150 non-scientific works.   Einstein's intellectual achievements and originality have made the word "Einstein" synonymous with "genius".

In 1905, Albert Einstein determined that the laws of physics are the same for all non-accelerating observers, and that the speed of light in a vacuum was independent of the motion of all observers. This was the theory of special relativity. It introduced a new framework for all of physics and proposed new concepts of space and time.Einstein then spent 10 years trying to include acceleration in the theory and published his theory of general relativity in 1915. In it, he determined that massive objects cause a distortion in space-time, which is felt as gravity ~ and it is one hundred years old now !!

This  month marks the 100th anniversary of the General Theory of Relativity, the most beautiful theory in the history of science, and in its honour we should take a moment to celebrate the visualized “thought experiments” that were the navigation lights guiding Albert Einstein to his brilliant creation. Einstein relished what he called Gedanken experimente, ideas that he twirled around in his head rather than in a lab. Here is something that appeared in NYTimes.

As these thought experiments remind us, creativity is based on imagination. If we hope to inspire kids to love science, we need to do more than drill them in math and memorized formulas. We should stimulate their minds’ eyes as well. Even let them daydream.Einstein’s first great thought experiment came when he was about 16. He had run away from his school in Germany, which he hated because it emphasized rote learning rather than visual imagination, and enrolled in a Swiss village school based on the educational philosophy of Johann Heinrich Pestalozzi, who believed in encouraging students to visualize concepts. While there, Einstein tried to picture what it would be like to travel so fast that you caught up with a light beam. If he rode alongside it, he later wrote, “I should observe such a beam of light as an electromagnetic field at rest.” In other words, the wave would seem stationary. But this was not possible according to Maxwell’s equations, which describe the motion and oscillation of electromagnetic fields.

The conflict between his thought experiment and Maxwell’s equations caused Einstein “psychic tension,” he later recalled, and he wandered around nervously, his palms sweating. Some of us can recall what made our palms sweaty as teenagers, and those thoughts didn’t involve Maxwell’s equations. But that’s because we were probably performing less elevated thought experiments.By the early 1900s, a variety of experiments showed that light travelled at a constant speed, irrespective of the observer’s motion relative to the light source. The physics community was puzzled by this, just as Einstein was still puzzled by his attempts to imagine riding alongside a light beam. So, in 1905, he performed some new thought experiments.He was then working at the Swiss patent office. Every day, he would attempt to visualize how an invention and its underlying theoretical premises would play out in reality. Among his tasks was examining applications for devices to synchronize distant clocks. The Swiss (being Swiss) had a passion for making sure that clocks throughout the country were precisely in sync. As the Harvard historian of science Peter Galison has found, more than two dozen patents were issued from Einstein’s office between 1901 and 1904 for devices that used electromagnetic signals such as radio and light to synchronize clocks.

What Einstein was able to visualize was that if you sent a light signal from the clocks the instant they struck the hour, a person traveling superfast toward one of the clocks would have a different view of whether they were in sync than someone traveling superfast in the other direction.He later explained this idea with another thought experiment. Suppose lightning bolts strike a train track at two distant places. Imagine that there’s a man standing on the embankment midpoint between the two strikes. If the light from each bolt reaches him at the same instant, he will say the strikes were simultaneous. Now imagine that there’s a woman in the midpoint of the train just passing him. If the train is moving forward superfast, by the time the light waves arrive she will be slightly closer to the lightning bolt in front. She will declare that it happened first.“Events that are simultaneous with reference to the embankment are not simultaneous with respect to the train,” wrote Einstein. Here’s the fun part: There is no reason to decree that the man is right and the woman wrong, because there’s no reason to assume that the embankment is “at rest” and the train “in motion.” The man, woman, train, Earth, solar system, galaxy, etc., are all in motion relative to one another, and none of them can claim the privileged status of being at absolute rest. So there is no “real” or “right” answer. What is “simultaneous” is relative, depending on your state of motion.

That means time is relative. If you travel near the speed of light, time slows down. Don’t feel bad if you can’t grasp this right away. It was another four years before Einstein was able to get a job at a university teaching physics.This relativity of space and time became known as the Special Theory, because it applied only to a special case: an observer moving at a constant velocity.

The effects produced by gravity and the effects produced by acceleration are equivalent, Einstein postulated. Thus they must have the same cause. “The effects we ascribe to gravity and the effects we ascribe to acceleration are both produced by one and the same structure,” he declared.In his Special Theory, Einstein had shown that space and time were not independent, but instead formed a fabric of “space-time.” With his general version of the theory, which became known as the General Theory of Relativity, this fabric of space-time became not merely a container for objects. Instead, it had its own two-way dynamics: moving objects would curve the fabric, and the curves of the fabric would influence how objects moved.
On four consecutive Thursdays in November 1915, Einstein laid out his General Theory to the Prussian Academy of Sciences in Berlin. In his final lecture, on Nov. 25, he produced the equations that describe the gravitational-inertial field. Einstein’s final equations used the condensed notations of tensors to compress sprawling complexities into squiggly symbols and subscripts, making them compact enough to be printed on T-shirts for physics geeks.

Years later, when his younger son, Eduard, asked why he was so famous, Einstein replied by using another simple thought experiment to describe his insight that gravity was the curving of the fabric of space-time. “When a blind beetle crawls over the surface of a curved branch, it doesn’t notice that the track it has covered is indeed curved,” he said. “I was lucky enough to notice what the beetle didn’t notice.”In fact, Einstein did more than just notice what the blind beetle couldn’t see. He was able to imagine it by conjuring up thought experiments. That ability to visualize the unseen has always been the key to creative genius. As Einstein later put it, “Imagination is more important than knowledge.”

That makes very interesting read, though most part was not fully understood by Yours Truly – excerpted from the article of Walter Isaacson, the C.E.O. of the Aspen Institute;  the author of “The Innovators” and biographies of Einstein, Steve Jobs, Benjamin Franklin and Henry Kissinger, as it appeared in NY Times.

With regards – S. Sampathkumar

5th Nov. 2015. 

No comments:

Post a Comment