Time Dilation - Einstein's Theory Of Relativity Explained!
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One evening in the spring of 1905 Albert Einstein, then a patent clerk in Bern, after trudging through his day's workdecided to board a tram car on his way homeEinstein would often wrap up his work as soon as possible to contemplate the truths of the universe in his free timeIt was one of these thought experiments he devised on that tram car that revolutionized modern physics foreverWhile receding away from the Zytglogge clock tower Einstein imagined, what would happen if the tram car were receding at the speed of lightHe realized that if he were to travel at186,000 miles per second the clocks hands would appear to completely freezeAt the same time Einstein knew that back at the clock tower the hands would tick along at their normal paceFor Einstein time had slowed down. This thought blew his mind.Einstein concluded that the faster you move through space the slower you move through time. How is this possible?Einstein's work was heavily influenced by two of the most iconic physicists of all timeFirst there were the laws of motion discovered by his idol Isaac Newton and second were the laws of electromagnetismlaid down by James Clerk MaxwellNewton's laws insisted that velocities are never absoluteBut always relative, so that their magnitudes must be appended by the phrase "with respect to"For instance a train travels at 40 km/h with respect to someone at restHowever, it only travels 20 km/h with respect to a train traveling 20 km/h in the same directionOr it travels 60 km/h with respect to another train traveling in the opposite direction at 20 km/hThis is also true for the velocities of Earth, the Sun and the entire Milky Way galaxyOn the other hand Maxwell found that the speed of an electromagnetic wave such as light is fixed at an exorbitant299,792,458 m/s regardless of who observes ithoweverMaxwell's notion seems incompatible with Newton's notion of relative velocitiesIf Newton's laws are truly universal. Why should the speed of life be an exception?This presented Einstein with a daunting dilemmaThis conflict between the ideas of Newton and Maxwell can be demonstrated with another of Einstein's brilliant thought experimentsEinstein imagined himself on a train platform witnessing two lightning bolts strike on either side of himNow because Einstein stands precisely in the middle of the two strikesHe receives the resulting beams of light from both sides at the same timeHowever things get more complicated when someone on a passing train views this event while whizzing past Einstein at the speed of lightIf the speed of light conforms to the rules of relativity, then the person on the train wouldn't witness the lightning strike simultaneouslyLogically the light closer to the man on the train would reach him firstA measurement of the speed of light made by both men would differ in magnitude, this would contradict an apparently fundamental truth of the universeEinstein had to make a difficult choice. Either Newton's laws were incomplete or the speed of light was not a universal constantEinstein realized that the two notions could coexist with a small tweak in Newton's lawsTo get rid of the discrepancy in the measurements Einstein suggested the time itself for the man on the trainMust slow down to compensate for the decrease in speed such that the magnitude remains a constantEinstein called this absurdity "Time Dilation" and his newfound theory "Special Relativity"Newton believed the time moved unflinchingly in a single direction forwardEinstein however had just realized the time stretches and contracts varying with velocityDue to its malleability time like spaceDeserved its own dimension in fact Einstein claimed that the two were one and the sametogether they formed a four-dimensional fabric or continuum called space-timeupon which the mundane events of the universe would unfoldEinstein Suggested that massive objects like the Sun didn't pull bodies like earth with a mysteriousInexplicable tug, but rather curved the fabric of space-time around themForcing earth to fall down into this steep valleyA highly simplified analogy is the dip in a trampoline made by a falling bowling ballIf a marble were placed on that trampoline the marble would immediately roll towards the bowling ball in the centerThis is also true for Earth's gravityWe are pinned to the ground because space so distorted by the Earth's mass pushes us down from abovehowever the slump in the fabric around Earth is not uniform andEarth's gravity grows more intense as we move towards its center where the curvature is at a maximumTherefore like the marble on the trampoline an object that falls towards the earth accelerates as it races towards the center of the planetIt falls faster when just above the surface than it does say when it is slightly above the atmosphereBut hey according to special relativity the faster you move through space the slower you move through timeThis means that time runs slower on Earth's surface than it does above the atmosphereNowBecause different planets have different masses and thus different gravitational strengthsThey also accelerate objects at different rates as we have learned this means a variable passage of timeThis is what happens in the movie interstellar when the protagonists land on a planet in the proximity of a black holeThe gravity on the planet is so severe that one hour on the surface is equivalent to seven years on earthTo understand how motion affects time let's consider the simplest timekeeping mechanismA second passes each time the photon is reflectedLet's imagine two people one in a spaceship slightly above Earth's atmosphere and the second on top of a small hillJust above the Earth's surfaceBoth are watching a man fall from space towards the groundLet's say that the falling man is carrying the photon clock explained a moment agoWhat do each of the two men observe as the man falls past them?What they observe is eerily similar to what a stationary person would observe when watching a ball bounce in a moving train.As the man falls from space, the light in his clock would appear to move in triangles to the two observersThis would mean that the light travels a longer distanceconsequently stretching the duration of a secondIt is obvious that the length of triangles the light traces and therefore the duration of a second isproportional to the velocity of the falling manWhen we recall that objects closer to the center of the planet fall fasterWe can determine the time would appear to pass slower to the man on the hillThan it does to the man in the spaceship above. Of course the difference is infinitesimalThe difference between the time measured by clocks at the tops of mountains and at the surface of Earth is a matter of nanosecondstime dilation affects every clock whether it relies on basic electromagnetism or a complex combination ofElectromagnetism and Newton's laws of motion. In fact even biological processes are slowed downYes, that's right your head is slightly older than your feet