Nexus - 0406 - New Times Magazine-pages

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NEWSCIENCENEWSCIENCENEWSCIENCE Clock A is at the north pole (more cor- elapsed time) were obtained when the From this person's point of view, the rectly, at the centre of the Earth). Clock B_ clocks returned to the laboratory, those beam travels a distance of 300,000 kilome- is the laboratory clock (now at the equator) clocks would have been incurring time _ tres in his reference frame. However, from which is spinning around A at close to __ variations as they moved around the planet. the point of view of a person past whom 1,600 kilometres per hour. If a person were to be looking at those _ the device is moving, the beam will take Clock C represents the clock in the first clocks, as per Figure 1, they would (purely — more than one second of his time to travel section of the Hafele-Keating experiment, hypothetically) see the clocks ticking over _ this longer path (Figure 4). and is moving around A at 2,100 kph. at different rates. Clock D represents the second part of that If an observer is located at the equator a rAi experiment, spinning around A at 1,100 _ with his own set of atomic clocks B, then, kph. as clocks C and D move past him, he would determine continuous time varia- tions in those clocks compared to his clock > with each of their trips around the planet (Figure 2). clock C time Special theory's time dilation is depicted dilation in physics textbooks using a device known as a light-clock. Imagine a glass tube, 150,000 kilometres tall. From the point of view of a person . standing next to the device, a beam of light observer's . clock B time travels from the base to a mirror at the top | Figure 4 Figure 2 of the tube and back to the base. This determines one second of elapsed time in This is based on the assumption that the his reference frame (Figure 3). beam of light will follow the angular path at c (i.e., the special theory claim that the ; speed of light in the stationary observer's clock D time reference frame remains constant, regard-