Einstein succeeded in simplifying the physics that became complicated towards the beginning of the 20th century
By: Nitzan Achsaf, Window website for physics
A hundred years after Einstein's amazing year, most people still don't understand exactly what he did. Here, we will try to clarify things.In 18 months, Isaac Newton invented the differential and integral calculus (calculus), built a theory of optics, explained how gravity works and discovered the laws of motion. As a result, the year 1665 and the first months of 1666 are called Newton's wonderful years. It was an incredible streak of achievements that no one thought anyone could match. But before 1900, phenomena were discovered that the laws of classical physics could not explain. The theories of Newton and James Clark Maxwell, who continued him in the mid-19th century, were in trouble.
Then in 1905, a young patent clerk named Albert Einstein found a way forward. In 5 amazing papers he showed that atoms exist (at the time it was still controversial), introduced the special theory of relativity and put quantum theory on the map. It was a different feat than Newton's, but Einstein's amazing year was no less amazing. Unlike Newton, he did not have to invent new mathematics. But he had to change fundamental ideas of space and time. And unlike Newton, who published his results 20 years later (obsessed with secrecy), Einstein published his works one after the other, like a flood of ideas.
For Einstein, this was only the beginning - he went on to create the theory of general relativity and was the pioneer of quantum mechanics. While Newton came up with one system that explains the world, Einstein came up with two. Unfortunately - his discoveries - relativity and quantum theory - are against each other. Both of them cannot be correct everywhere, even though their statements are remarkably accurate in their field - the very large and the very small. Einstein would spend the last years of his life trying to reconcile the two theories and failing. But at that time, no one else was able to solve the problems, and Einstein was the one who saw them most clearly.
When Einstein won the Nobel Prize, in 1921, it was for the first paper he submitted in 1905, which proves the existence of photons - the particles of light. Until this work, light was considered a wave, which explained the interference patterns when light passes through a grating. Einstein, on the other hand, started from a different assumption, while taking into account the "black body" experiment.
A "black body" is a theoretical heated box that emits electromagnetic radiation (light, and its "relatives" such as radio and X-rays) at all frequencies. One of the main problems in physics at the end of the century was that blackbody radiation was supposed to increase to infinity at higher frequencies, which was physically impossible. 5 years earlier, Max Planck, an esteemed German physicist, thought that a black body could only emit radiation at non-continuous frequencies. The gaps between these frequencies are the quantum jumps from which quantum theory gets its name. Dividing the radiation into small but measurable parts in this way solves the problem of frequencies increasing to infinity.
Planck stopped shortly before he made the deduction that light, divided into small but measurable parts, means that it is made of particles and not waves. Einstein, however, concluded exactly that. Moreover, he went on to show how this assumption explained the photoelectric effect, another physics mystery at the time.
The photoelectric effect occurs when there is a flash of light on an electrical conductor. The light displaces electrons from their orbit and creates a current. The paradox was, that a stronger beam of light on the conductor did not increase the electric voltage, even though the current increased. In other words, the light produced more electrons, but not more energetic electrons. But if we increase the frequency of the light, the electric voltage will increase. Einstein showed that this phenomenon is explained if light consists of particles (which were only later called photons), whose energy is proportional to their frequency.
Although physics students today wonder how the Nobel Prize was awarded to Einstein for his quantum work and not for relativity, the truth is that at the time, including Einstein, everyone thought it was the more surprising result.
Although Einstein's hypothesis was eventually accepted, it had an importance that even he did not foresee. By the late 20s, quantum theory had developed in an improvised fashion. A young generation of physicists in the 20s and 30s grouped it into a universal system, which is now known as quantum mechanics. This showed that light is neither a particle nor a wave, but both together at the same time. Similarly, objects previously thought of as particles, such as electrons, are also waves at the same time.
Two results followed. The first, that luck plays an essential role in the interaction between elementary particles, and therefore also in the way the world works. Physics, until that time, was "deterministic", there were no uncertainties. But, uncertainty is at the core of quantum mechanics. One example of this is the "uncertainty principle" of Werner Heisenberg, which says that it is impossible to accurately measure both the speed and the position of an object. Another example is "Schrödinger's cat", which says that the cat can be simultaneously alive and dead because its fate depends on a quantum property of an object, whose state is not defined until it is measured.
The second result is that the world is "non-local", meaning that quantum interactions occur instantaneously over long distances. In addition, there is no mechanism in quantum mechanics that explains how a particle "communicates" in order to adjust the quantum property in this way. For example, if a particle rotates in a certain direction, its partner must rotate in the other direction. But, the first particle has no defined direction until it is measured (again, Schrödinger's cat), so the second particle cannot "know" where to turn until a measurement is made on the first particle; By this point in time, the other particle could be millions of kilometers away. Einstein called it "spooky action-at-a-distance".
Einstein was not comfortable with either result. Therefore, from that time until the end of his days in 1955 (which makes 2005 also the 50th anniversary of Einstein's death) he worked to remove them from physics. But in the secret of his heart he did not really believe that quantum mechanics is fundamentally wrong but only incomplete. And indeed he was the first to propose Schrödinger and Hisenberg (whose reputation was not yet established at that time) for the Nobel Prize.
The best analogy is for temperature. Temperature doesn't really exist. When something is said to be hot or cold, what is really being described is the average speed of the molecules of that substance. If the molecules move faster - it is hot, if they move slower - it is cold. Temperature is only an extract of the above average. Similarly, Einstein believed that quantum mechanics describes a statistical average of a hidden phenomenon that is deterministic.
In 1935, Einstein and his two partners proposed an experiment that would test the above idea by investigating action at a distance. But, only in 1982 was the experiment carried out. And when the measurements were made it turned out that Einstein was wrong and not the quantum theory. Remote action really happens. But, this is an excellent demonstration of Einstein's contribution to quantum mechanics. By frequently trying to find holes in the theory, he made it stronger and clearer.
Avraham Pace, a physicist who wrote Einstein's biography, said that there were two things that Einstein was better at than anyone else - he knew how to find invariance principles and how to use statistical fluctuations. Invariant principles play an important role in the theory of relativity. And really, Einstein wanted to call relativity the 'theory of invariants'.
The concept of an invariant, is something that remains constant after several changes. A circle is constant under rotation, as it looks exactly the same no matter where it is rotated. A square, on the other hand, is only fixed under a 90 degree rotation (and multiples of 90 degrees). Under any other angle - the square will look different.
Einstein's insight was that the speed of light is such a constant. The speed of light will remain constant regardless of the speed of the observer. Add to this Galileo's condition, that the laws of physics should appear the same as long as the observer is in steady motion, and the theory of special relativity follows. But why did Einstein think that the speed of light is constant?
It all started with the Michelson-Morley experiment first performed in 1887. Although Newton explained in the 17th century how light behaves, no one knew what it was made of until 1860 when Maxwell showed that it consisted of fields Electrons and magnets oscillate. This immediately raised the question - in what were the fields swinging? At that time, no one could understand that waves do not have to be oscillations in a certain medium. In the ocean there were waves in the water, and sound waves moved in the air; It seems strange that waves can 'just be'.
Therefore, scientists assumed the existence of the ether (aether) - an undetectable substance through which light travels. But if it orbits the sun, and therefore moves through space, it must also move through the ether. The thought was that if we measure the speed of light in the direction of the movement as well as in the direction perpendicular to the movement, we can get different results. That's exactly what Michaelson and Murray thought. But, they found that the two speeds were exactly the same.
A possible explanation for the disappointing results of the experiment was given by Henrich Lorentz (Henrich Lorentz), a Dutch physicist, who came up with the necessary mathematical explanations for the answer - there is a shortening of the experimental system in the direction of the movement of the Earth, just to the extent necessary for the two velocities to appear the same . However, Lorenz could not explain how the shortening occurs. He hypothesized that the cause might be forces acting within the molecules.
What Einstein realized, without adding new mathematics, but still in a completely new way, that this explanation is simply not true. Space really shrank, and time really slowed down. This is exactly what Pace meant when he said that Einstein knew how to choose constant variables. Everyone thought time was constant, but it is not. No one thought that the speed of light was constant, but it is.
The same distinction eventually led to the development of general relativity by Einstein. One of the consequences of the speed of light being constant is that nothing can move faster than it. Einstein noted this already in the first paper he submitted in 1905. At that time he had not yet seen the second implication, that the constant also implies that mass and energy are interchangeable. The 'exchange rate' is defined using the speed of light and is represented
By the famous equation: E=mc/2 where E is the energy, m is the mass and c is the speed of light. This equation, the results of which were seen in Hiroshima and Nagasaki in 1945, occurred to him a few weeks later, and was published in a document written in November 1905.
The speed limit was problematic for Newton's theory of gravity, since according to Newton, gravity moves instantaneously - something that according to Einstein is impossible. This made Einstein think about what exactly mass is.
In 1907, he realized that the feeling a person has when he is pulled by the gravitational force of the earth is the same as the feeling in nature of a person in acceleration, for example when he is pushed against his seat when an airplane takes off. These two sensations are related to the mass of the same person, but classical physics assumed that these are different phenomena. Einstein, however, concluded that since gravity and acceleration look the same, they really are the same.
He called this theory the principle of equivalence. But, unlike in the special theory of relativity, for which Lorentz developed mathematical explanations, in this case there was no mathematical explanation to rely on. This took Einstein another 9 years, and together with the help of his mathematician friend Marcel Grossman, they developed the mathematics behind the general theory of relativity. that way
Einstein developed the concept of space and time.
The second part of Pace's opinion, that Einstein is a great statistician, is seen in his work, which tends to get lost in the mess of relativity and quanta. One of the things that Einstein did in 1905 was to prove the existence of molecules (and therefore, by simplification, also the atoms that make them up) and deduce their size. This required the use of statistics, because of the large amount of molecules.
One of his works deduced the size of the molecules from the viscosity of a solution of sugar in water. For years it was his most cited study. A second paper addressed the question of Brownian motion - random movement of small particles, such as dust or pollen, in a solution. This movement was seen for years under a microscope, but no one could explain it. Einstein, in a short and beautiful work, explained how motion is caused by molecules hitting particles, thus proving that molecules really exist.
Einstein also used statistics in his work on assigning discrete (non-continuous) values to light and the photoelectric effect. He also continued to apply statistics to quantum theory, even before it was fully developed by Heisenberg, Schrödinger and their peers. In 1922 he got a job from Satyendra Nath Bose, an Indian physicist unknown at the time. Bose developed the statistics regarding the behavior of large numbers of photons. Since photons are similar particles, which do not collide with each other, their behavior is unlike anything anyone has seen before. Einstein realized that Bose made a small number of mistakes, but he also realized that certain atoms, if cooled to near absolute zero, would show the same behavior as photons. In fact, they will act like one giant atom.
This prophecy seemed very strange at the time, and only in 1995 the first Bose-Einstein condensate was made in the laboratory. Examining that condensation is one of the hottest areas in experimental physics.
This is just another example of Einstein's perception, when he saw things that no one else at that time saw. As he said in 1932 'the real aim of my research has always been to simplify and unify the system of theoretical physics'. Einstein was not able to unify physics, but although this seems paradoxical to the layman, he did manage to simplify it. Once one learns the complex mathematical language required to express one's ideas, Einstein's theories are the simplest and clearest in physics.
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