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“Imagine you are talking with a typical 8th grade student. Explain why Einstein was worried about what would happen if you could “chase a light beam”. After you submit your response (try to keep it under 250 words), you will be able to see other students’ responses. Introduce yourself to your group, and look and see how your response is similar to and different from your peers. You should aim to respond to at least two other posts in the week's forum. You could, for example, point to something commendable in the post (such as a point that was particularly clear, or an idea that you hadn't considered). If you can, you might also be able to make a recommendation: perhaps there's something further that is relevant to the post, something missing, or a way of rephrasing a point? As you look to respond to two other members of your group's posts, try to respond to someone who has not already received any comments first.

Today, many 16 year olds are chasing lots of things: Footballs in games, goals in life, and girls in school! However, Einstein, unlike most of us, was tackling the conundrum of chasing light at this age. This young boy was imagining himself running at the speed of light, c = 3x108 m/s, so that alongside him was a single beam of light. Now, I am sure you are thinking why a 16 year old is so intrigued by something this “weird”. To help you understand, let me present you with a thought experiment; Imagine sitting in a plane up in the air, now right alongside you is another similar plane, the 2 planes are perfectly aligned and the background scenery of the sky and ground is the exact same. So, tell me in your eyes, will the second plane really be moving at a speed? The answer is no, relative to you, the secondary plane will be at rest i.e. not moving. It is this idea that led Einstein to contemplate chasing a beam of light. Einstein was worried because if the beam of light obeyed the standard laws of electrodynamics and optics it should appear to be at rest (following the example of the secondary plane), however, this is not really what happens; Maxwell, an earlier physicist, had published a well backed paper stating that light will always propagate at a constant speed, c. Conclusively, Einstein asked himself,” will the light beam appear to be at rest, still moving at the constant speed, c, or is there an underlying flaw in our understanding of Electrodynamics and Optics?”

Discussion Forum: Week 3, due Sept. 29 - Discussion Group-07 Hide Full Description Einstein’s theory is admittedly very weird. It just doesn’t seem like moving objects contract, moving clocks run slow, or that astronauts return home younger than their earthbound twin. Why doesn’t everyday experience just show that Einstein is wrong? (Many, many people think that it does!)

After writing an answer and submitting it by Wednesday at 10 p.m. (try to keep it under 250 words), you will be able to see other students’ responses. Look and see how your response is similar to and different from your peers. Do they mention new ideas that you had not considered? Are there any further puzzles to raise with me or the TAs?

Every day, one can find situations that relate to Einstein’s theory, e.g., If I saw a moving car and decided to measure its length, my answer, and the answer of an individual B inside the car will be different. This seems like a contradiction; however, our answers are different because we are not measuring the same distance; for me, I place flags labelling the start and end of the car at the same time but for person B the front flag went first hence for him I am measuring the car length plus some distance moved by the car. Person B and I disagree about which events are simultaneous. Moreover, from spacetime geometry, it’s easy to see the fundamental principle explaining all “weird” attributes of Einstein’s theory. Everyday experiences don’t prove Einstein wrong because of perspective in relative motion. The world line of a relatively moving observer will be at an angle to the worldline of the second observer, resulting in a tilt of their simultaneity surfaces i.e., an imagined plane that shows simultaneous events. This tilt brings about the phenomena of length contraction and time dilation. To illustrate, when twin B leaves earth and takes a roundabout trip maintaining a speed of 86.6% the speed of light, the hypersurfaces of his simultaneity are tilted compared to the Earthbound twin A’s horizontal hypersurface. From these hypersurfaces, we read that twin B judges twin A’s clock to be running at half the speed of his clock. At the turn-around point, twin B’s hypersurfaces change dramatically which causes a time dilation effect: Twin B will be half the age of Twin A upon reuniting. To conclude, these “weird” attributes may seem imaginary because we can’t feel them however, they are real, real in the eyes of a relatively moving observer....