“ ABOUT TIME ” 1962 BELL SYSTEM SCIENCE SERIES FILM w/ DR. FRANK BAXTER PART 1 XD82965a

foreign system brings you another of its series of programs on science man's effort to understand nature's laws it is written to everything there is a season and a time to every purpose under heaven foreign what is time when we try to say what it is it eludes us yet man can measure time with the greatest Precision with his instruments he can stretch it or compress it what the scientist knows what he hopes to know about time is the fascinating subject we will explore foreign foreign [Music] the idea of time is so much part of our habits that if we're really to look at it or think about it objectively perhaps we'd better create a new atmosphere of thinking and for a new atmosphere suppose we take an imaginary trip into the vast Universe of stars and planets galaxies and meteors [Music] [Applause] [Music] all right foreign [Music] now to set the stage for our story about time suppose we imagine a brand new planet there we'll give it a name planet Q and the people there as we imagine them will be normal intelligent people except for one strange thing they don't know much about time and their king would like to set the clock sir are we ready to set the clock very well let the clock be set yes sir but where will I put the hands well you what time is it if you don't know find out yes sir foreign there's one more thing we've imagined here on planet Q an observatory and inside of it this will call it an earth scope we'll use it to examine some of the things that people on earth have found out about time come in hello say we've run into a little problem I wonder if you could answer a question the king wants to know what time is it oh yes what time would he like it to be oh the correct time you see we're setting our clocks so that we can do everything on time well tell him to set it any place he likes thank you [Music] any place that's right well let's see suppose we use the Earth scope screen bring the earth into Focus see what time it is down there foreign [Music] is that the correct time it is for London England what time is it they call it noon that also happens what they call midnight or is midnight before or afternoon 12 hours after or 12 hours before it all depends on what whether you're talking about yesterday or tomorrow but they had to start somewhere how did they go about it The rhythms of nature probably gave man his first awareness of time man must have observed the recurrence of natural phenomena the movements of the Sun the moon and the stars he noticed that these events in the heavens seemed to coincide with events on Earth spring and the rains summer growth of leaves the Autumn ripening of fruit he thought the moon sun and stars controlled his crops this was understandable because to him Sun the moon and the stars were gods people began studying the heavenly bodies as they made notes of their changing positions the science of calendar making began almost every civilization labored to devise a workable calendar some of them were based on the cycles of the Moon others on the movements of the Sun but none of them came out just right even the Gregorian calendar the one used today is not perfect [Music] wouldn't you think by now they'd have a perfect calendar it's not so easy you see the time it takes the Earth to rotate on its axis is a day but the time it takes the earth to revolve around the Sun is a year but a year comes out to 365 days five hours 48 minutes and 46 seconds oh and the problem is what to do with that leftover fraction of a day that's why they add an extra day every four years except of course when that year Falls at the beginning of a century of course but they add the extra day every fourth century of course but it's still off 26 seconds a year so they call it a calendar but it's still off 26 seconds a year it's very interesting I thought so and after we get the clock set we'll get a calendar but one thing at a time yes sir just explain to him that we need to know the time to eat to sleep and so forth Just anytime won't do well early man didn't regulate his habits to a clock all animals including man and plants too have a built-in time sense I didn't know that foreign considered a wonderful phenomenon of nature that plants seem to know when to flower and set their seeds at just the right time that furry animals have a way of knowing when to change to their heavy coats before the first cold Winds of Winter the birds by some Instinct know just the right time to set out on their long migrations always bear their young in a seasoned favorable for survival it was once commonly supposed that these seasonal occurrences are triggered by changes in temperature but investigations have shown that plants and animals depend mostly on timing mechanisms within themselves internal clocks internal clocks that's right interested yes this clock or biological timer determines the seasons by the changing lengths of day and night particularly the periods of Darkness Darkness yes [Music] here is Dr Anton long plant physiologist and director of erhart Laboratory who has been experimenting with a timing mechanism of the cockleberry plant the Autumn flowering cocklebur needs about eight and one half hours of continuous Darkness to flower as Autumn comes the nights get longer when they get long enough for the plant's timer to tick off eight and one-half hours of Darkness the flowering begins if the nights get longer that means the days get shorter how did they know it wasn't the short days that did it well they didn't so they conducted a series of experiments under artificial light they simulated various proportions of Night and Day from these experiments scientists proved that it is the darkness that the cocklebur plants measure and all plants and animals have one of these internal clocks well some plants and animals have another kind of timing mechanism this one doesn't measure Darkness or any apparent outside influence it regulates the activities of the plants and animals by time periods alone bean plants for example have this kind of continuous clock they raise or lower their leaves without much regard to temperature light or Darkness some animals like the hamster also have a continuous clock the hamster's daily cycle is broken into definite periods a period for eating a period for sleeping [Music] period for exercising [Music] his clock continues to run to regulate his Cycles even though he lives in continuous Darkness or continuous light practically every kind of living organism seems to have some sort of built-in time sense [Music] scientists all over the world are trying to find out how internal clocks work when they do find out it may mean that the cycles of plants and animals can be controlled directing their energies into producing more food more clothing more shelter that's quite incredible but one thing puzzles me if man has a built-in clock like those plants and animals why did he need other clocks he found that his internal time sense was not adequate for his needs which are far more complicated than those of plants and animals man had to find other means of measuring intervals of time so he invented a clock well a type of clock yes actually he stuck a stick in the ground and told time by the moving shadow this became the basis of the sundial Egyptians developed a clock that measured time with dripping water and there were other clocks that measured time with flowing sand none of these early time Keepers could measure small intervals of time with any accuracy in 1583 Galileo made a discovery which proved to be the first big advance in accurate time keeping as he watched a swinging lamp suspended by a long chain in the Cathedral of Pisa he noticed by counting his pulse beats that each swing took the same time so Galileo proposed using a pendulum as the basis for a clock the pendulum swinging steadily the Dutch scientists Christian Huygens devised a mechanism inside a clock that gave the pendulum a little push at the end of each swing this same mechanism also turned the hands on the clock face counting the number of swings it was the world's first pendulum clock the grandfather of all grandfather clocks and the grandfather of all our best timing methods [Music] for an order to measure time you need something that will give you a constantly repeating movement a rhythm then count the movements the more precisely these movements repeat themselves the more accurate your measurement of time I don't care about bean plants cuttlebirds and pendulums where do we set the clock the man in the observatory says we I'll find out for myself what he says [Music] um what a piece of Machinery isn't it yes it is what is it hair spring and balance wheel of a watch in slow motion oh the sort of portable pendulum real pendulums work only when they hang straight down so they're no good for watches or portable clocks but this mechanism gives a constant rhythm in any position at each turn of the balance wheel the escapement mechanism releases the Locking of an escapement lever ticking off the constant Rhythm you need to measure time the first watches were pretty but not very accurate then as as the old world began to expand across the seas accurate time keeping became really important you see without accurate timepieces navigation was a problem I just checked the sun's position and found out that it's 12 o'clock here buy this watch I've carried ever since we left England a month ago it's nine o'clock in Greenwich so our position is three hours or 45 degrees east of Greenwich where does that put us uh in Baghdad sir Baghdad watches just weren't accurate enough to keep exact granite's time on a long voyage in 1761 after years of experimenting an English clockmaker John Harrison developed the first really accurate portable time keeper it was off less than two minutes after a five months voyage the accuracy of the ship's clock or chronometers it's now called enabled man to navigate any Waters and encourage Sailors to explore the Seas all over the Earth although now ships can get Greenwich time by radio all navigation today still depends on knowing what time it is well now that's the same problem we're having knowing what time it is I don't suppose you care to explain how they set their clocks on Earth I'd be delighted oh good all clocks are set by radio signals in the Western Hemisphere these come from the United States Naval Observatory where signals are broadcast accurate to within one thousandth of a second [Music] from such radio signals broadcast from various observatories the clocks of the world are set but where do the radio signals get their time from from the official timekeepers special clocks regulated by quartz crystals quartz crystals what's wrong with pendulums and those other things balance Wheels they aren't accurate enough their rates affected by wear movement air currents and temperature quartz crystals are less subject to these influences but they give us repetitive movement just like the pendulum and the rotating balance wheel to the eye quartz crystals seem inert but actually under the influence of an electric current they vibrate measuring off tiny and precise slices of time these vibrations are added up by electronic circuits into seconds minutes and hours some quartz crystal clocks have a maximum error of one one hundred thousandth of a second per day well that's certainly accurate but if clocks are set by radio signals and radio signals are set by quartz crystal clocks how do they set the quartz crystal clocks by the Master Clock which is the Turning Earth itself every night when the sky is clear United States Naval Observatory astronomers photographs Stars through a fixed vertical telescope from this they determine the precise instant when the observatory passes directly under a particular star the next night they note again what time they pass under that particular star [Music] thank you [Music] the positions of the multiple exposures on the star plate are then carefully and accurately measured [Music] the information is turned over to the electronic calculator the result is the true determination of time based on these readings they're able to find the precise time that it takes the Earth to make one rotation the official clocks are compared to this and their rates are calibrated come in excuse me sir I was just wondering ah you're just in time I have come to a decision we'll set our clock by the Earth the perfect time keeper well not perfect what do you mean by that the Earth is gradually running down running down I refuse to accept that but it's true friction is the main Force that's slowing down the Earth where does the Earth get its friction from tides these tidal bores in the Bay of Fundy are good examples friction from tides in the shallower Seas is gradually slowing down the Earth slowing down if we can't trust the Earth what can we trust well the scientists themselves are not satisfied with the Earth as a clock now they're working on an atomic clock a clock based on the cesium atom has been developed at the National Bureau of standards in Boulder Colorado this clock keeps Time by counting motions inside the atom as the nucleus spins its axis swings back and forth and the swings are detected electrically and counted the Motions of atoms are more regular than those of pendulums balance Wheels the Earth and even of quartz crystals and it's likely their regularity will continue as long as matter exists this clock is believed to have a maximum error of one second in three thousand years well that's accuracy as Sir it occurs to me yeah well I don't think it would make much difference to anybody if they did lose a second or two now and then or everyone depends on accurate timing whether they're aware of it or not for example with quartz crystals it's the precisely controlled number of vibrations per second that determines the killer cycle and mega cycle channels used in Broadcasting television in Multiplex where many messages travel a single cable or travel or radio relay beam accurate timing of electrical impulses is the heart of all communication systems an even greater accuracy in timing is needed by scientists who are constantly trying to get a more complete and accurate understanding of the physical universe and today the quantity that can be measured more accurately than anything else is time well I suppose such accuracy is important to a scientist and Engineers but still one little second doesn't seem so important really or second is important take a look nine and three tenths seconds what kind of a clock was that a stopwatch it measures intervals of time down to a tenth of a second of course it's not very practical when you're trying to measure a millionth of a second but who'd want to measure a millionth of a second scientists engineers technicians anyone who deals with things moving at high speed what kind of a clock would they use for that usually a cathode ray oscilloscope never heard of it basically it's much like a TV picture tube but it's used differently the beam of electrons sweeps across the screen over and over again in the same track now if we connect say a microphone sound will jog the beam and make a jog in the trace like this the ticks of a watch put time markers on the sweep five to the second when we speed up the sweep the time between ticks is stretched out to full screen speeding up the sweep still more and using an electronic timer we can put on markers of a hundredth of a second or less and measure the speed of a bullet as it cuts two wires only a foot apart let's take another look and stop the picture the interval between the two vertical lines we've drawn here represents the time it took for the bullet to break the two wires how long was that a thousandth of a second that's really quite a long time a radar scope with even faster sweeps tells how long it takes for a radar signal to strike an object and bounce back that tells you your distance from the object or you can time signals from three lower end stations operated by the United States Coast Guard by comparing them adjusting the traces so they will coincide know your exact position by putting markers on a very fast sweep scientists find it easy to measure intervals of a billionth of a second well that's not too bad is it do you have any idea how short a time that is do you frankly I don't well a billionth of a second has the same relationship to one second as one second has to 35 years one second to 35 years now I see how small that figure is and even the billionth of a second is long compared to the much shorter times that scientists have to deal with although the atomic world that makes up this drop of water is still hidden from the eyes of man we know a good deal about how these bits of matter behave how they move and in how short a Time [Music] in this drop of water there's a vast number of atoms in constant motion and just one of these atoms will have ten thousand collisions in a billionth of a second and in the time between each of these collisions the outside electrons of the atoms would go around 100 times and in the time it takes an outside electron to go around just once the inside electrons would go around 100 times and in the time it takes the inside electron to go around just once the particles in the nucleus of the atom would vibrate one hundred thousand times these are the tiny intervals that scientists must try to measure thank you foreign

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Length: 28min 38sec (1718 seconds)

Published: Thu Apr 04 2024