Updated: Jul 1, 2021
From establishing fundamental theories in physics to impacting modern technological advances, how did Einstein change the world of physics? And how did challenges to Einstein get disproven? Read on to find out.
Author Name: Ted Isidor
Editors: Ken Saito and Michael Zhu
Artist: Jiaqi Fan
Imagine if you were able to get really close to the sun. Picture its scorching heat and blinding light. Now, get even closer and observe the rays of light coming from the sun, which are in discrete packets of energy called photons. These photons travel at immensely high speeds as they get shot off from the sun. Imagine the rush of such an experience as you ride alongside this ray of light as it goes faster and faster. At the age of 16, Einstein had such a thought (which later became the so-called thought experiment) that inspired him to create an uproar in the field of physics. Einstein is hailed as a remarkable figure in physics and science in general because his theories changed the way we viewed the universe and studied its mysteries. His two theories General Relativity and Special Relativity, gave new ways of approaching physical phenomena in contrast to the previous ways, such as Newtonian Mechanics. General relativity gave way to understanding the curvature of space, to put it in simple terms, “matter causes space to bend, making gravity.” Special relativity says that when traveling at a constant velocity, any object/body will experience the same physical laws when compared to an object at rest and that the speed at which light travels is constant for all observers, regardless of whether they are measuring from Earth, Mars, or in motion. For decades physicists have tested the principles of special relativity to see whether these two ideas held.
Before the iconic scientist, many physicists and astronomers used Newtonian mechanics to understand how things move in the universe. The principles of Newtonian mechanics include force equals mass times acceleration (F=ma), an object in motion/rest shall remain in motion/rest until acted upon by another object, and that every reaction causes an equal and opposite reaction. These pillars of science, as great as they were, failed to describe many of the phenomena that took place in the universe, such as gravitational lensing, in which the gravity caused by a massive object in space causes a light ray to change from following a straight path to a curved one. Its major flaw can be described in one of Einstein’s thought experiments. Imagine an old train like the ones seen in old movies moving along a railroad track with you placed in a railroad cart all by yourself. In your hand lies a ball, which you bounce up and down within the rail cart. Now, your friend, whose name will be Michele, is standing along the side of the tracks watching the train you are in motion. For you, as an observer, the ball is only moving up and down when you bounce it, but for Michele, the ball is traveling a much greater path that resembles a triangle with a huge base. These two observers view the phenomena taking place differently. Now, in Newtonian Mechanics, one of the observers must be wrong. Here lies the weakness of Issac Newton’s work, first addressed by Einstein in his theory of special relativity. One of Einstein’s postulates was that the events an observer sees are relative to themselves, eliminating the idea that one person is right and the other is wrong. The other major postulate he had is that the speed of light must be constant for all observers. Take, for example, a case in which Einstein is on the ground with a tool that allows him to measure the speed of light and you are an astronaut aboard the ISS and are equipped with the same tools as your pal Einstein. On the ground, Einstein measured the speed light traveled to be 300 meters per second. In the case of you, an astronaut aboard a vessel traveling at 4.76 miles per second, you measure the speed of light surprisingly to be the same as Einstein. Though there are only two postulates in Einstein’s theory of special relativity, many more bizarre yet brilliant ideas sprouting from this theory, such as time dilation. It describes that when an observer travels at fast and faster speeds, time moves slower and slower. Another idea is that if an observer is traveling at a constant velocity, the physical laws that apply to events here on Earth will be the same. Now we see the beauty and simplicity of Einstein’s theory, but when it was first published, many scientists were reluctant to validate his findings and still believed in Newton’s way. Scientists began proving whether this theory, which could change everything, was valid.
To discuss how scientists proved the Theory of Special Relativity, one must first resort to the Michelson-Morley experiment. This experiment did not seek to prove special relativity but instead the existence of “the aether.” The aether was an old idea regarding how light can travel. Sound, for example, travels from one place to another via the atmosphere. Physicists, as brilliant as they were, thought, “Hey, what if light travels through its own atmosphere?” Physicists Edward W. Morley and Albert A. Michelson both set out to prove or disprove the existence of the aether in a unique way. Initially, the experiment went like this: A pulse of light is sent through a mirror that is half transparent and half non-transparent (set at 45 degrees), which will then break up this light pulse into halves. These halves will then reach other mirrors and reflect back to the half-transparent mirror. Now, if the aether exists, then one of the halves will arrive earlier than the other due to an aether wind. In regards to air on earth, wind results in the speed at which sound is traveling to be slowed or fast. The physicist thought that if the aether behaved like the atmosphere, wind in the aether would change the speed at which the particles travel, just like wind affects the speed of sound. The conclusion of this experiment told us that the answer to the question, “Does the aether exist?” is surprisingly no, because every time in which the pulse was measured, the light was consistently measured to be roughly 300 million meters per second, rather than fluctuating due to aether wind. This constant nature of light proved Einstein's theory, that “The speed of light is constant for all observers.” The results of this experiment initially faced resistance by hardcore aether fans, but in the end, Morley and Michelson were awarded the Nobel Prize for their work. The work of Michelson and Morely was impressive but it takes more than just one experiment to convince the world that Einstein is correct, so our path in discovering the truth of Einstein’s theory focuses now on proving or possibly disproving the “smartest man in the world.”
One way to prove the postulates of special relativity is by using a GPS app. The GPS app uses a group of satellites orbiting the earth to identify where something or someone is located and how to get from one place to another. The technology that enables this was initially designed to aid the military, but it turned out that the GPS was often inaccurate due to time dilation. Since satellites are farther away from the Earth than we are, time goes slightly faster (milliseconds). This margin or error itself is proof of Einstein’s theory of special relativity, but additionally, the mathematics behind this theory helps avoid a possible road trip disaster.
An idea remains an idea unless proven. As awe-inspiring as they may be, Einstein’s theories would have resulted in nothing without experimental results. Experiment and theoretical physics go hand in hand in progressing the study of physics, with the theory of special relativity being a clear example. Although theorists are the coolest kind of physicists, experimentalists can have the MVP cap for now.
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