ABOUT TIME

foreign [Music] wait a minute I have a question you have been splitting time smaller and smaller now is there any limit to how small time can be split if there is such a limit it would be shorter than the time it takes light which is the fastest thing we know to go across the smallest piece of matter which is an atomic particle this would be approximately one millionth of a billion of a billionth of a second well they wouldn't want to split it any smaller than that certainly they would if they could wouldn't they yes if they could you see if there is a limit to how small time can be split it would mean the time is not a continuous flow but is made up of little pieces little pieces of time it's unbelievable that's because our feeling of time is limited we can grasp only those intervals we're familiar with seconds at one end of the scale hours days months and at the other end the number of years in a lifetime this is a very small range in the middle of the vast scale of time the infinitesimal fractions of seconds at one end and the billions of years at the other we say that the age of the Earth is four and one-half billion years but how long is that let's consider the life of the Earth in terms of what went on what happened what changed since it's difficult to relate our feeling of time to large numbers let's squeeze the age of the Earth into one 24-hour day we begin at midnight four and one-half billion years ago it's a long time say two o'clock in the afternoon before any life at all appears on the earth at 7 pm Life Begins leaving remains in the form of fossils dinosaurs develop at 11 PM only one hour left to go in our Earth Day and now at just two seconds before midnight the human species first appears on Earth in the last tenth of a second the entire 6 000 years of civilization since the early Mesopotamians and ancient Egyptians takes place and in the last one thousandth of a second before midnight there are the two World Wars but there's one thing that bothers me if people weren't even around most of that time how do they know what went on and when perhaps a geologist should tell you about it this is Dr Gerald J wasserberg the events in our natural history and the times at which they occurred can all be told from rocks by examining the fossils the minerals the makeup of the Rocks we can tell what happened and the sequence in which these events happen by using radioactive elements as our clocks we can answer the question when did certain events happen we know for example that in four and one half billion years one half of the uranium in Iraq turns into lead by measuring the proportions of uranium and lead in a given Rock we can figure how long it took for that amount of lead to form this gives us the date at which the rock solidified in this way we have been gathering information on the age of the Earth its errors and its effects they see all that in rocks yes rocks hold the secret of our past and the only history of the Earth it's all there in the Rocks waiting for man to discover some places Nature has given man an opportunity to see the changes that have taken place over vast periods of time by exposing a sequence of layers preserving for us a long record of Earth history records that show there were once deep waterways where mountains now stand large land masses that have been lost to the Seas and the Earth is still changing the same forces that have changed the face of the Earth in the past are still at work wind rain Rivers glaciers [Music] earthquakes [Music] and volcanoes [Music] how will the earth look in the eons to come if the Earth has a past to four and one half billion years what is its future we can only guess but the vast time of the past is small compared to the far greater expanse of time that is the future we've gone from a million of the billions of a billionth of a second to billions of years well that certainly covers time do you know what I like about time it has ordered it has mathematical precision one can almost see time evenly flowing throughout the Universe very interesting that you should describe time that way thank you that idea of time was accepted as scientific truth on Earth very good thinking sir accepted that is until the beginning of the 20th century just what do you mean by that time is no longer considered absolute it is not the same everywhere you mean at the same time here is not the same time there and at the same time is not flowing everywhere no I'm afraid it isn't [Music] what does that look to you they're moving too fast how does it look now too slow you mean that one group's moving slower and the others moving faster than we are well yes we're moving normally but they are not but if you were with those people moving at their rate of speed either fast or slow it would seem normal to you and I couldn't tell not of everything conform to that rate feed an object falls the water pours speed you talk and think everything hmm when we look at those people moving at different time rates they look peculiar to us they look peculiar to each other [Music] and to them people moving in our time rate would look peculiar well that was an interesting demonstration but I I still can't believe that in real life time could flow at different rates scientists have found that time rates are actually different under certain circumstances under what circumstances well for one the faster anything moves the slower the time rate for everything connected with it you'd better tell me that again yeah all right just imagine people traveling in a spaceship at almost the speed of light they'd be living in a much slower time rate than we are they wouldn't how did they figure that out it all began with a famous experiment made back in 1887 by two American physicists A.A Michelson and ew Morley they wanted to measure how fast the Earth is moving through space so they set up an experiment based on a simple principle we all know well from everyday experience we do well let me show you I suppose we're in a moving car a train going in the same direction passes this much more slowly than it does when we're going in opposite directions in fact the actual passing speed is simply the addition or subtraction of our speeds it was this principle that Michelson and Morley tried to use in their experiment only instead of sitting in a moving car they sat in their laboratory on the moving Earth and instead of a train they used light by comparing the speed of the light in various Directions They hoped to measure the speed of the Earth well what happened there was no effect the lights seemed to travel in the same speed no matter which direction it was going in other words it looked as if the Earth is standing still that's impossible isn't it I thought it goes around the Sun yes they've known that for 400 years so scientists went right on making more experiments to detect the motion of the earth through space but none showed any effect how did they explain their way out of that one among those who proposed explanations was a young clerk in the Swiss patent office named Albert Einstein he said of course the Earth is moving but the laws of nature must be so constituted that there's no way to detect it or to prove you're moving without comparing or relating to something outside that isn't moving along with you this is the principle of relativity Einstein's theory of relativity the first part of his theory it's really not so hard to believe for example in a plane flying at a uniform Speed without any bumps or turns you can't tell you're moving without looking out of the window so in order for Michaelson and Morley not to be able to tell the Earth was moving the light had to travel the same speed in either direction and that was the second part of Einstein's theory he said that light would always be observed to travel at the same speed no matter how fast or in what direction you were going you mean if I were in a very fast spaceship a beam of light would seem to pass me just as fast as it would you on the ground that's right sounds impossible doesn't it but Einstein explained it by pointing out that the only possible way that two people traveling at different speeds can both measure the speed of light the same is that they're measuring devices have become different because of the difference in their speeds and so they have different senses of time and space for example if you were in a spaceship to me on the ground your clock would seem to be running slower than mine let's try it all right with some simple animation let's see why the clock in a spaceship traveling near the speed of light and the clock on the earth measure time differently now here's a simple clock a hollow transparent Rod a mirror on each end and a beam of light bouncing from one end to the other beats tick off regular intervals same as any clock now we have two of them one is put in the spaceship and one kept on the ground to the man on Earth his clock continues to run at the same rate when he looks at the spaceship going by the action of the light in that clock looks like this think I see what's happening apps it'll be even clearer and slower because the spaceship is moving past the Earth man the light appears to him to travel diagonally to get from one end of the clock to the other because the light go further it takes longer between ticks and from the earth man's point of view the space band's clock is running slower [Music] the man in the spaceship must think his clock is crazy I would certainly think so well let's see inside the speeding spaceship the spaceman looks at his clock but seems perfectly normal to him just like it did on Earth his sense of time is different everything is changed proportionately so that the strange things would have had to happen weights would increase lengths would change all in perfect proportion so that he wouldn't notice any change and so that everything would seem perfectly normal is it so important that to everything seem normal remember the first part of Einstein's guess the principle of the laws of nature are so constituted that you can't tell you're moving without relating to something that isn't moving along with you then everything in the spaceship must seem perfectly normal or else the space man could tell he was moving with our light clock it's easy to see how this effect increases as your speed approaches the speed of light it's the same with everything in motion but in our normal lives we never get anywhere near speeds great enough to show this effect with our talk about that spaceship is it possible that people may someday travel near the speed of light at the moment it's pretty remote but based on Einstein's theory it's fun to conjecture what would happen here is a story of identical twins living in the einsteinian future our twins Peter and Paul they're having an argument over who's to have the honor of being the first Earth man to travel to the distant star Arcturus and back I want you to have the honor no you you deserve it [Music] see you in [Music] 60 years [Music] although Peter was 83 he didn't want to miss his brother's moment of Glory [Music] yes compared to his brother Paul was still a young man it doesn't look 83. he isn't traveling near the speed of light he aged less oh yes time slowed down that's right the closer he came to the speed of light the more Paul's heart beats with their periodic motion measuring time would slow down along with his rate of breathing other body processes [Music] Paul wouldn't notice though because his watch would slow down to the same degree [Music] know that Einstein guessed right and his theory is really true well let's ask a physicist Dr Richard Feynman of the California Institute of Technology in the laboratory we can get atomic particles to go nearly at the speed of light and so far all the effects predicted by Einstein show up for example particles which are unstable and disintegrate do last longer when they're moving than when they're standing still Einstein's theory of relativity has radically transformed Man's picture of the universe it has upset our traditional ideas about time and space and someday we may upset them once again because we're still learning what determines the direction of time what distinguishes past from future and what exactly is the present is now the same for everyone uh doctor is now the same for everyone no I was afraid of that well thanks for the use of the planet oh wait please you're not going to leave me now are you I mean we've gone all the way from shadow on the ground to sundials and pendulums and from atomic clocks to Suns moons stars from time that was fixed to time that is relative we've come a long way yes but now I have more questions than ever good the more we learn the more questions we have in the beginning you had only one question what time is it that's right well where do I set the hands of the clock oh that you can set them any place you want you mean because I'm the king no wherever you decide to set a clock in the beginning is more or less arbitrary however once you've said it that becomes your time and all your clocks must be synchronized thank you now we can set our clock [Music] thank you for our purpose that sort of winds up the story of Planet Q the story of time beginning stretching befores or who knows what complexities perplexities Mysteries how did Time start we don't know did the universe begin with a big bang 10 billion years ago some physicists and astronomers think so but others ask the question did the universe even have a beginning or been going on forever will it ever some 20 billion years from now when our sun burns itself out and explodes into Oblivion will time stop [Music] or will we just sit cooler and cooler longer and longer without light without warmth in the fathomless depths of space these are questions which baffle astrophysicists cosmologists many men of science [Music] men whose minds and imaginations are even now uncovering Clues to the mystery of time which is perplexed mankind for centuries what time is it the answer may be phrased in terms of molecular action the laws of nature but more directly what time is it is a question of our everyday lives contraction of Our arteries in our lungs the beating of our hearts the measure of our today's our tomorrows our lifetime [Music] as written in Ecclesiastes to everything there is a season time to be born A Time To Die time to plan a time to pluck up time to Cast Away Stones the time to gather Stones together a time to every purpose under heaven the Bell System is grateful to the many distinguished scientists who helped prepare the story of time our thanks to those who supplied and checked the scientific content and to the individuals and organizations Who provided special material our thanks to The Advisory Board which reviews the scientific aspects of these programs its members represent the broad range of modern Science Biology and genetics medicine bacteriology and body chemistry geophysics physics anthropology electronics and Acoustics mathematics engineering to all these men the Bell System is indebted for their support of this Venture in public education through entertainment foreign [Applause] thank you