Theory of relativity explained in 7 mins

hi so you want a simple guide to the theory of relativity great you've come to the right place part 1 classical relativity let's cart with some absolutes that we need to accept 1 there is no such thing as absolute motion or absolute rest objects move relative to each other for example look at the truck with two kids playing catch the truck is moving at a constant speed of 50 miles per hour but as the kids are also moving with it at 50 miles per hour they could easily think that they are standing still when the children's throws a ball at 10 miles per hour they observed that the ball they have thrown is moving at 10 miles per hour but their little brother who is not on the truck and his standing still has observed that the ball has moved at 60 miles per hour he has added both the speed of the truck and the speed of the ball together but is the little brother really standing still no the earth is constantly in motion the Sun is constantly in motion and the galaxy is constantly in motion therefore nothing is ever at Absolute rest or absolute motion things just move relative to each other this is classical relativity part 2 special theory of relativity time dilation the second thing we need to accept is that the speed of light is the same for all observers so let's imagine a beam of light being reflected between two mirrors let's replicate this setup so we have another beam of light being reflected between another set of mirrors but this time the mirrors are moving close to the speed of light we can see in the moving set of mirrors that the beam of light is moving a greater distance now let's put a couple of people into this scenario meet Alex he sits inside the moving set of mirrors and bill sits inside the stationary set of mirrors the speed of light must be the same for both Alex and Bill and their light beams must hit the bottom mirror after the same amount of time has passed but as Alex's light beam is covering a longer distance how is that possible well the only way for that to work is if time for Alex slows down look at the clock hand notice how Alex's clock hand is moving much more slowly compared to Bill's time for Alex has slowed which allows his light beam to travel a greater distance slizzard it this way feed equals distance divided by time as Alex's distance is more the value of his time must be more or rather Alex's 1 minute actually turns out to be longer than Bill's one minute when you compare the two time has slowed down for Alex this is called time dilation this is quite a hard concept to grasp because it seems to go against what we experience on a practical level but to understand the theory of relativity you must stop thinking of time as a fixed unit for everyone time is relative confused don't worry if you don't grasp all of this immediately remember it was the most brilliant scientist of the 20th century who put forward this theory so feel free to re-watch this part of the video as many times as you need part 3 special theory of relativity length contraction in the previous section we spoke about how the speed of light remains the same for Alex and Bill because while the distance Alex's light beam travels is more his time has dilated however and time don't increase by the exact same amount in fact time doesn't actually dilate enough to account for the speed to remain the same for both boys something else happens length contraction when objects are moving close to the speed of light not only does time slowdown but the object itself contracts this is called length contraction so in this scenario Alex and his mirrors are actually smaller than we thought and therefore the distance the light beam has to travel is actually smaller than we thought also in conclusion time dilation and length contraction work together to ensure that the speed of light remains the same for both Alex and Bill Einstein referred to think of space and time not as two separate things but one entity he called it space-time part four time travel time slows down for objects traveling close to the speed of light and time stops altogether for objects traveling at the speed of light it then follows that time must go backwards if objects travel faster than the speed of light so far it has been seen that no object can travel at the speed of light on approaching the speed of light objects start to increase in mass rather than speed and it would take an infinite amount of energy for an object to achieve the speed of light this is why we cannot travel back in time we simply have not been able to reach a greater speed than the speed of light part five general theory of relativity Einstein realized that the special theory of relativity which we explained previously only worked for circumstances when things moved at constant speeds through the universe what about when objects sped up what about the effect of gravity and come to think of it what is gravitational pull after all Einstein theorized that objects warped space-time around it causing it to become curved and as a result objects experience gravitational attraction to each other this warping of space-time explains how objects behave as they move through space this is the general theory of relativity part 6 how do we know it's true how do we know that the theory of relativity is true well countless experiments have been carried out and Einstein's equations hold true modern GPS uses Einstein's theory of relativity to pinpoint our locations with impressive accuracy in 1971 an experiment was conducted with four super accurate atomic clocks which were set to the exact same time as a reference clock the clocks were placed aboard commercial flights and the planes flew twice around the world first eastward and then westward when the clocks returned and were compared to the reference clock the clocks were no longer all synchronized and the differences were consistent with the predictions of special and general relativity so that concludes our explanation of the theory of relativity a bear in mind this is a very simplified explanation but it should give you a basic understanding of the core ideas so you can study further on your own we hope you enjoyed this video and be sure to subscribe to London city girl to see other interesting videos

Channel: LondonCityGirl

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Keywords: albert einstein's theory of relativity explained, Theory of relativity for dummies, Theory of relativity made simple

Id: ttZCKAMpcAo

Length: 7min 30sec (450 seconds)

Published: Sat Nov 01 2014