How Gravity Affects Time | Gravity and Me | Spark

[Music] Einstein's insight was that when something Falls it no longer feels the pull of gravity in fact falling is like floating in empty space this is the essence of Einstein's happy thought and what we now call his principle of equivalence Einstein's point is that when the man in the lift falls he doesn't just feel weightless he is weightless Einstein said the man feels no force pulling on him because there is no force pulling on him gravity doesn't act on him it acts on the space and time around him what we now call the geometry of space-time this was a radical redefinition Einstein says forget the idea of gravity as a force acting mysteriously between two objects now we have to think of it as the shape of space-time changing you see Newton saw space and time as independent fixed and immutable the three-dimensional space is the stage in which things happen but time is separate it ticks by at the same rate everywhere in the universe according to Newton an object would travel through space in a straight line unless acted upon by a force like gravity that will cause it to deviate from that path but Einstein said that space and time aren't fixed and immutable they're interconnected meshed together in what is known as space-time and he said that space-time can be looped that matter curves space and time around it so after Einstein we no longer see gravity as an invisible string pulling objects together instead a body like the earth warps the structure of space and time around it and an object in orbit follows a path which is as straight as possible through that space-time it's a fundamental part of Einstein's vision of reality space and time can't be disentangled you can't talk about space separately from time so matter warps time as well as space it's known as gravitational time dilation and it's possibly the strangest of all of iron Stein's discoveries [Music] I've got two identical clocks here now because the clock lower down is closer to the center of the earth it feels ever-so-slightly a stronger gravitational pull than the clock higher up Einstein's theory says that the lower clock will tick by at a slightly slower rate than the higher clock basically gravity slows time down it's an extraordinary conception of reality that Einstein describes spaces being curved and time is being distorted so why can't we perceive this in our everyday lives Einstein had a rather nice way of explaining it most of us have had the experience as children of trying to work out what our parents do for a living well imagine your father as Albert Einstein when he was about 12 years old young Edward Einstein asked his father why he was so famous what he discovered well let's put Einsteins senior on the spot but he came up with a beautifully simple analogy Einstein told his son when a blind beetle crawls over the surface of a curved branch it doesn't notice that the track it has covered is curved I was lucky enough to notice what the beetle didn't notice this is what Einstein meant the beetle is free to move in any direction on the branch it can move forwards backwards left and right but it has no concept of a direction up off the branch it's as though for the beetle the universe is missing the third dimension the beetle may think it's moving in a straight line along the branch but we can see that the surface is walking on is itself curving and twisted Einstein's point was that what we see as the twists and curves of the branch feel to the beetle like forces pushing and pulling it ok so consider this rather strange example imagine we have two beetles perched on this pumpkin and for whatever reason they want to walk up towards the top now if they start at the equator pointing due north as they walk there will begin by moving parallel to each other that means their paths should never meet but as they get closer to the top their paths get closer together now if they have clever beetles they might try and figure out what's going on and they could imagine that there's some mysterious force that's pulling them closer together but for us from our perspective we can see there is no such force all they're doing is following straight paths over a curved surface [Music] just as the beetles have no sense that the surface of the branch is curved we completely fail to perceive the bizarre ways that gravity shapes the reality we live him Einstein's problem was proving that he was right after years more thoughts he realized that there was away by looking far out into the solar system incredibly here in the grounds of her salon so castle is housed one of the original telescopes that were used to prove Einstein was correct in 1915 when Einstein developed his general theory of relativity it was just that it was a theory it had no proof in fact many people found it completely outlandish but then just four years later in 1919 this telescope and allow me to geek out a bit here and I'll give it its correct name this is the 13 inch Astro graphic reflector this telescope proved that I sign was in fact right that gravity does curved space itself since then observation after observation have confirmed that matter curves space and slows down time so the simple question of why things fall the way they do has led us deeper and deeper into the very nature of space and time itself gravitational science shows us how galaxies stars and planets fall by measuring gravity we've discovered the existence of dark matter that 80% of the mass of our universe is invisible and we don't know what it's made of and we've detected exotic objects with extreme gravity like neutron stars which have more mass than our Sun near only 20 kilometers across [Music] you

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Keywords: spark, spark channel, spark documentary, science bites, physics, physics documentary, jim al-khalili, jim al-khalili documentary, jim al-khalili quantum entanglement, jim al-khalili information, jim al-khalili gravity, jim al-khalili atom, jim al-khalili chemistry, gravity, gravity documentary, how gravity affects time, how gravity works, einstein, einstein documentary, einstein and gravity, science documentary, time dilation, general relativity, albert einstein, mind blown

Id: QQRj78jOxWo

Length: 8min 31sec (511 seconds)

Published: Fri Jan 04 2019