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Homework Help: A little help with Special Ralativity.

  1. Apr 8, 2013 #1
    Hi I'm a first time poster so go easy. Hopefully I'm posting in the right place.

    I'm doing a research paper (my first) on Albert Einstein. It's a general paper on his life and work. I've come to 1905 and his breakthrough papers. Basically I wanted to write a brief summary of what each paper entailed. I know it seems a long read but it is not. Anyway my main question is have I sufficiently written a summary of his fourth and fifth papers? I do realise I have made no mention of Newton's mechanics and Maxwell's electromagnetism (and the ether) but I do not know how i can succinctly explain these principles and keep the paper sufficiently tight. This is my effort so far:

    • The fourth paper would transform our perception of space and time. In “On the Electrodynamics of Moving Bodies” Einstein would deal with something that had been puzzling the scientific community for some time, namely that the measurement of the speed of light produced the same result (300,000 km/sec) no matter where it was measured.
    • This contradicted Galilean Relativity. For example if a light was shone from a moving object at a standing observer then the speed of the light measured should be the speed of light + the speed of the moving object. This, however was not the case, the measured speed of light was always 300,000 km/sec.
    • Einstein tried to make sense of this by studying speed itself. Every speed is relative, we might say a car travels at 40 mph but what we mean is it travels at 40 mph relative to the ground. We don’t take into account the speed of the earth around the sun or the sun through our galaxy.
    • The speed of light always measuring the same caused a lot of problems. What if you were in a space ship that was traveling at 250,000 km/sec and another observer was at rest on earth, how could light still be travelling at 300,000 km/sec faster than you and the person on earth? Who would be measuring it correctly?
    • The temptation for Einstein was to prove that the speed of light did change under certain circumstances. But Einstein decided to approach the problem from a different perspective.
    • He based his work around two postulates:
    The principle of relativity: The laws of physics are the same in all nonaccelerated frames of reference.
    The principle of light: The speed of light is a universal constant. All observers in uniform (nonaccelerated) motion measure the same value c for the speed of light.
    • This gave him the answer that the person in the space ship and the person on earth were both correct from their perspective.
    • Light could be traveling equally faster than the both of them if for each of them a second lasted a different length.
    • For both observers they would experience time as they always had.
    • However if the observer on Earth were able to see the observer on the space ship, they would appear to be moving incredibly slowly, because on the space ship one second of time would be longer relative to the observer on Earth.
    • This theory showed that there was a fundamental link between space and time (space-time continuum) and if an observer moves fast enough through space he will experience space and time differently from another observer who is moving at a different speed.

    Chapter 6.2
    • The fifth paper (an extension of his findings in the fourth paper) in 1905 “Does the Inertia of a Body Depend upon its Energy Content” proved to be Einstein most famous piece of work and produced probably the most famous equation in all of science:


    • Where E=Energy, M=Mass and C=The Speed of Light.
    • What the equation basically states is that the closer an object nears the speed of light (c ) the mass of the body (m) increases. If the body were to reach the speed of light it would be infinitely massive and of infinite energy.
    • Until this paper and equation energy and mass were seen as being complete separate.
    • This was the first time a relationship between the two was established.
    • Thus energy can be turned into matter and vice versa.

    Thanks for reading. I'm not looking for someone to write my paper for me, just a yeah or neah whether I've produced a sufficient enough explanation.
  2. jcsd
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