"All human cultures build up a lot of the stories they tell each other, their rituals, their religions, and their science by thinking about light." "Man of God declared light divine." "Scientists bent it through glass to see to the depth of space and the minute interiors of cells." "It seemed, by understanding the truth about light, we would understand the truth about everything." "But it turned out, and this is surely one the great paradoxes of the light stories that we have been telling, it turned out, that the more people can manipulate light, the more puzzling and tricky, light turned out to be." "And in very same idea that light and truth go together, it turns out that a great deal of what light gives us is an illusion." "In 1664, the great natural philosopher, Isaac" "Newton, performed his ground breaking experiment, showing that a prism can split white light into colored rays." "But above all, what Newton did with his prism was to set up a great challenge for future generations," "He'd shown white light as a mixture of colors, but beyond that, he admitted to be completely mystified." "Color was light's last mystery." "Understanding color would be the key that would unlock the truth about light, and as it did, it would change everything." "Science, art, and even our understanding of the human mind." "The first step in the story into the heart of light needed one of the greatest upheavals in history." "The industrial revolution began in the late 18th century textile mills of North West England." "People were forced to think about light and particularly, color in a new and urgent way." "Controlling color counted." "Because the British market was being flooded by brightly colored clothes from India, from Asia." "British industrialists counted this flood with their own crafts and their own industrially manufactured dyes." "Standardizing those colors, getting chemical control over how they were made, and then making sure they mix tightly with the dye clothes, was the key to market success." "Perhaps the most dramatic impact of the new color industries was the way it changed folk sense, of what was natural, what was artificial." "Colors which were previously been understood as matching natural objects, the blue of the sky, the green of grass, the red of the rose, could be made completely artificially." "Artificial dyes revealed that many people didn't see a colored clothes the same way as others did." "For the first time, people realized there was a mystery about the way we see color." "It is inevitable that the puzzle of getting color judgments systematically wrong, appears precisely at the place and the time of mass color industrialization," "North West England at the end of the 18th century." "The man who matters was John Dalton." "John Dalton, the gifted son of an impoverished weaver, threw himself into the new chemistry of the industrial revolution." "He is best known now for proposing the atomic theory of matter, but his first scientific paper was based on his realization that there was something awry with his own color perception." "Dalton, who was a Quaker, showed several signs of getting color wrong or judging it badly when he went to Quaker meetings, he would sometimes turned up dressed in the most inappropriately bright colors in a red gown, not the sort of thing that" "a dweller, solid, Quaker citizen should be wearing." "For the first time in history, Dalton started to systematically analyze his own sense of color." "He went back to nature and to his childhood fascination with botany." "The bright pink flower of clover seemed bright blue to him." "The pink geranium, the pelargonium seemed absolutely blue when he collected it outside." "And when he brought it into the house and looked it by candlelight, it changed strangely from being blue to being yellow." "Dalton meditated on this problem, was it special to him?" "Dalton, who worked as a school teacher, asked his pupils whether they had the same problem." "And it turned out in a class of about 2 dozen, 4 or 5 boys suffered from exactly the same puzzle." "Dalton was the first person to identify and scientifically study color blindness." "Dalton himself thought it was caused by a physical property of the eye, he came up with a gruesome way of testing this idea," "In Dalton's will, he instructed his medical adviser," "Ransom, to take out one of his eyes, and dissect it." "Because Dalton guessed that the reason for his color blindness was that there was a blue liquid inside his eye." "Ransom followed Dalton's will to the letter." "He extracted one of the great man's eyeballs and cut it open." "There was no blue liquid." "Ransom, instead, described the eyeball as pellucid, it let the light through perfectly, it showed no staining, no color, there was no blue liquid inside, that couldn't be the explanation of Dalton's own color blindness," "instead, and this was what was really suggestive, the problem must be to do with some kind of judgments, something more psychological, something between the brain and the back of the eye." "Dalton may have got the cause of color blindness wrong, but he proved that condition ran in families£¬ and it came in just a few common forms." "He published this revolutionary findings in the new industrial age's greatest city." "Dalton's great lecture of October 1794 on the" "Manchester literary and philosophical society set a stage for nothing less than a revolution in the science of light and color." "The commercial imperatives of the industrial revolution would lead to the discovery that the mind has a role to play in how we see color." "The booming factories and towns of 18th century Europe, urgently needed brighter and more efficient lamps and lanterns." "Designing them would revolutionize our understanding of the true nature of light." "Now put the lens in." "The key figure in this story was an" "American immigrant living in Europe called Benjamin Thompson." "Thompson did one of the most intriguing experiments ever on the behavior of light, but it started because he was trying to save money for his employers, the city of Munich." "The Munich government gave him a really important job which was to clean every single beggar off the Munich streets and put them into newly designed workhouse which Benjamin Thompson constructed." "As a reward, Thompson became a Count, Count Rumford" "Now on of the things his workhouse is going to need was lighting, and so Rumford decided to do a series of extraordinarily precise experiments to work out what the cheapest kind of lighting could possibly be." "One set of experiment he was really keen on doing was seeing if it is possible to compare say, the brightness of a candle, with the brightness of sunlight, now he need to stop down the sunlight that was coming into his lab," "so what he did was to use a series of colored filters in order to bring the light down." "But as he put colored filters in front of sunlight or lamps, he noticed something absolutely extraordinary." "So, look at the shadow through this red filter, and you see that the shadow is now a rather beautiful turquoise," "and the shadow cast by this lamp, which was black, has gone red." "Well, we might be able to see why the shadow on the left has gone red, because we have put red filter in front the light that is illuminating that shadow, but what is going on with the other color, that was Rumford's big problem." "At this point, Rumford tried to eliminate from his field of view, everything except the turquoise shadow," "he decided to look at the turquoise shadow through a tube painted black on the inside." "And this was even spookier." "To Rumford's utter amazement, when he used his tube, so the only thing in his field of view was the blue shadow, its blueness disappeared." "I was not able even to tell when the colored glass was before the lamp and when it was not, and though the assistant often exclaimed the striking brilliancy of the shadow's color," "I could not discern in it the least appearance of any color at all." "He couldn't see any color change, whatever the assistant was doing." "He saw a uniform shadow." "That was really hard to understand." "Two people see the same thing differently." "There could only be one explanation, that color exhibited by one of the shadows only is real, that of the other is imaginary, being an optical deception occasioned in someway unknown to us." "These colors that we see are actually the work of our own brains, they are not simply just out there in the world." "Rumford had shown, for reasons he didn't understand, that the human mind can add colors to the dull colorless grey of a shadow." "Rumford himself hoped that the effect of this discovery on the future of art, and painting would be revolutionary and so it was." "Contemporary painters, like Joseph Turner, realized that colored shadows would make their paintings more authentic, more psychologically real." "This is The Fighting Temeraire." "The shadowed side of the tug boat, instead of being grey, is tinged with violet to bring out the melancholy mood of the sunset." "The shadows in Claude Monet's paintings of Rouen Cathedral are alive with color, yellow to evoke the haze of mid day sun, purple for the dying light of twilight." "Rumford recon that the implications of the fact that colors are partly made up by the mind would then go far beyond painting." "Rumford, kind of had a dream, if colors are subjective, then you ought to be able to use them to entertain people, to seduce people in fact." "The idea was that you could key the keyboard of a harpsichord to colored lights, and when you played a note, a color would appear." "Rumford called this device, an optical harpsichord." "He never actually built one, it was too difficult with 18th technology." "It took 200 years for Rumford's dream of light and music to come true." "But back in the late 1700, people were observing more and more aspects of light and color which they had no way of explaining." "What it caused to John Dalton's color blindness?" "What was causing Rumford's colored shadows?" "What was needed was a breakthrough in the understanding of what light is." "And that breakthrough came in the early 1800, but not from someone who was investigating light, but from someone who was investigating sound." "The hero of this story was a wealthy, and precocious" "Cambridge medical student called Thomas Young." "Now as a member of the college and a wealthy one of that" "Thomas Young liked horse riding, he liked music, and he liked placing bets." "And there is a bet recorded in the gambling book of the college that Thomas Young, as a student, bet that before he graduated, he would write the best essay ever on sound." "He thought he did, no one else did, and he lost the bet." "But that essay argued that if you listen hard to organ pipes, you are unlocking the mystery of the way sound travels" "An amazing truth about light would be hidden in Young's essay about sound." "His initial interest was to investigate a fact that people had known since antiquity: sound travels in waves." "For instance, columns of air in organ pipes vibrate up and down, rather like ripples of water going back and forth in a lake." "Young studied the unusual and distinctive way in which sound waves behave, particularly when they overlap." "You play a single not on the organ, and it sounds pure." "if you add another note, which is out of tune," "you begin to hear beats, which are relates to the difference in frequency between the two notes." "When two waves meet, they can either add or subtract, you get pulses of addition and difference." "Young now made a dramatic leap in imagination, he realized that light must work in the same way that sound does." "If you shine a beam of light through a card with two slits in it, as the two light beams emerging from the slits recombine, you see a patter of bright and dark bands." "The two beams of light cancel each other out in places just as the two sound waves do." "That could only mean one thing:" "light, like sound, was a wave." "Today, everything from optical fibers to spectacle design is based on the idea that light is a wave." "But at the time, it was an incredible idea, from Newton on, the existing notion of light was that it is a stream of tiny core parcels, or particles." "Young's radical idea was greeted with house of derision." "Young's lectures on his new theory that light travel in waves were very controversial." "It was going right against 150 years of models of light as a particle." "Young hit back." "And the example that came to mind was a pond." "Think of waves traveling on the surface of a pond, and you could see the way light moves." "Young's lecture with their watery model of light were a powerful argument for a new wave theory which would explain how we see and how light travels." "The idea that light was a wave is now heralded as one of the great discoveries of science." "It meant color was at last comprehensible." "Just as different frequencies of sounds gives you different notes, different frequencies of light give you different colors." "On essence, the idea was really simple and it was illustrated during the 19th century by pretty simples machines like this." "Now imagine that this is a wave of light what Young asked is what happens when light waves of this kind enter our eyes." "It seemed obvious to him that what the retina is doing is vibrating, it is not some kind of passive screen that get hit by particles, it is a vibrating membrane, and the faster it vibrates explains the difference in colors," "so the blue making rays are vibrating really fast, red rays much more slowly." "And Young even guessed something really important about the way we sense color, if light is a wave, and colors are different frequencies of that wave, then maybe in the very back of the eye, we have different" "kinds of senses which pick up different kinds of vibrations." "Young experimented with spinning color wheels, and he saw if you spun fast enough, just three colors: red green and blue, can combine to appear as white." "What Thomas Young concluded from this is that the vast panoply of colors humans think they see comes from combining our responses to just 3 frequencies of light, red green and blue." "Now if that model is right, this will begin to explain the kinds of color blindness that his friend John Dalton was exhibiting, because if one set of receptors wasn't working properly, you wouldn't pick up that kind of color, that was Young's idea." "Dalton, the man who begun the study of color perception, provided bizarre posthumous confirmation of Young's idea." "In 1995, 150 years after his death, doctors extracted DNA from Dalton's eyeball, which amazingly have been preserved by a Manchester scientific society," "Dalton's DNA showed that he was blind to red and green." "Back in the 19th century, understanding the mystery of how we see color couldn't have come on a better time, color perception was now a matter of life and death." "In 1875, in Sweden, near the town of Largarenda, a train missed a red signal, and hurtle towards another in the middle of the night." "9 people died, hundreds were injured." "A local professor, guy called Holmgren, guessed that one of the guys on the north bound train was probably color blind and then mistaken a red light for green and sent the train hurtling to its destruction." "In Britain where there were more railway lines than anywhere else, the government lurched into action." "Experts from the scientific establishment were hired to do tests on whether there were good ways of spotting the color blind among its drivers and pilots." "The leader of the inquiry was Lord Rayleigh, a very well connected and very wealthy gentleman." "Rayleigh was an expert on light and sound and he had already studied the rather bizarre fact that a lot of his brothers in law, including the eminent Tory politician, Arthur Balfour, seems to suffer from a strange form of color blindness" "in which they were over sensitive to red lights, not as you would have thought a normal problems among Tories." "But what Rayleigh then did was to introduce a system of absolutely rigorous color testing on the working class." "Building on Young's 3 color theory, Rayleigh devised the first ever color blindness tests for every train driver and boat pilot in the country, and by the early 1900, the modern color perception tests which most people now take were developed." "But back in Victorian times, the human ability to discriminate between subtle differences in color was at the heart of massive controversy." "It was widely accepted that all people, not just the color blind, see color slightly different, and some Victorian scientists believed that if they could accurately measure this variation, they would prove, categorically, the most repugnant of all European ideas:" "white supremacy." "Color perception played an absolutely crucial role in European ideas about human nature itself, the coming fashion for racist explanations of the difference between human groups cashed out its ideas in the area of differential sensitivity to colors." "This is how it worked, it was believed that animals had faster, better attuned senses than humans" "and at that time, it was also believed that black people were lower down in the evolutionary scale, so more like animals." "And to prove that fact, all you had to show was that their responses to light and color were better." "In 1898, a group of Cambridge based scientists and medics went from" "England to the Torres Straits, the islands between Australia and new guinea." "One of the most important members of this expedition was a man named William Rivers." "Rivers was an extraordinary figure." "He was a brilliant physiologist, and medic." "He'd written the definitive accounts of optics, and vision, and color perception." "What Rivers was gonna do was to set up a psychology lab on the beach." "This is one of the actual bits of equipment Rivers took to the Torres Straits to assess native's color perception." "It is called a tintometer, it was designed to test human sensitivity to subtle changes in color." "What Rivers was going to do was to test how Torres Straits islanders matched colors, so for example, he might take a particular red, and dropped it in to this tube, and then invite the islanders to select a glass" "color which corresponded to that, like that, then the islander would look down the tube, and degree that this two colors are the same, or this shall be slightly darker, or slightly lighter." "What this allowed Rivers to do, then, was to construct numerical color scales for islanders' color perception and test whether islanders or others could make finer color discriminations." "Day after day, bemused islanders queued up to look at tinted slides, spinning disks, and have their reaction time measured." "But River was in for big surprise, what he found, by an large, the range of discrimination of colors he found amongst the islanders was not bit different from the range of discrimination of colors amongst the English." "In other words, the English differs from each other as much in their color discrimination as they did on average for many Torres Straits islander." "The psychic unity of human kind, most people see things in roughly the same way." "To Rivers it turned no credit, when he found that this evidence contradicted his original hypothesis, he simply ditched it." "On his return to England, Rivers spear headed a movement that argued that there was no scientific evidence for the superiority of European culture over any other." "For many of the sides I think Rivers is an extraordinary hero," "He understood extremely well that European culture, Cambridge culture could be studied in exactly the way that other cultures was studied by European scientists." "He has a wonderful story about what it would be like if an islander from the Pacific came to Cambridge and began to study the Cambridge natives, surely Rivers pointed out, this islander would naturally assume that the natives of Cambridge" "had some kind of primitive, or sentimental, or superstitious mentality which completely explained their bizarre rituals and strange behavior." "Studying the human response to light created two new sciences:" "psychology and anthropology," "but light itself remained enigmatic." "Thomas Young's idea of light waves was accepted, but what was these waves made of?" "The answer would come from studying an aspect of light, but it is not at first obvious, the fact that the light doesn't just show us the world, it changes it." "As anyone who had a rather bad sunburn would tell you, light doesn't leave the body it touches unaffected, on the contrary, light is a powerful chemical, physiological, and biological agent which can have the most huge effects on anything with which it interacts." "The story of this discovery of the most miraculous of light's properties begins in the late 1700s in industrial England with one of the greatest English chemist Joseph Priestley." "Joseph Priestley, a Yorkshire man, of impeccable intellectual credentials, tough minded, radical, materialist, and ambitious, was one of the leading natural philosophers of late 18th century Britain." "And for Priestley and his closest friends, light and life went together." "In this experiment, Priestley put a mouse into a sealed bell jar, to test what happened to the air, as the mouse breath in and out" "Fairly quick, the mouse sickened, got exhausted, and died." "This air, he reckoned, must be really bad, really bad not just for living animals, but for plants as well." "So into the jar, Priestley introduced a set of growing plants." "And he left them there for several weeks." "To his amazement, they grew happily." "Whatever was in the air that killed the mouse seemed to make plants flourish." "Priestley decided to test what it was in the air where the mouse had died that was responsible for encouraging the life of plants." "He would simply introduce another mouse." "The result was absolutely amazing, he found, provided that the plants was growing there, that the animal would suddenly revive." "This was, what he called, the luxury air, which only a couple of mice and myself have had the privilege of breathing, and there was more, what Priestley found was that the quality of the air wasn't just improved by growing" "the plant in it, if you shone a light on the plant, the air quality went shooting up." "What it showed was that light shining on the green matter in plants could restore the air to an almost paradisiacal quality where it would keep animals alive for unparallel periods of time, where flames would burn with extraordinary life." "Light and life went together." "We now know Priestley's discovery as photosynthesis, the remarkable way plants absorb the energy from light, and in the process, convert carbon dioxide into oxygen." "Light doesn't just show us the world, it is a form of energy that is essential for all life." "The discovery that light was energy and could effect powerful chemical changes would have surprising results." "It would open up a world that no one had ever seen before." "The story begins with Tom Wedgwood, son of the famous potter Josiah." "Tom Wedgwood's experiments would kick start one of the most revolutionary technologies of all time, photography." "It began with Tom try to help out the family business." "Wedgwood's pots were famous for their hand drawn decorations and tom wanted to find a way of decorating pots automatically." "So what Wedgwood did was to prepare of special chemical mixture, made up of silver nitrate and common salt." "Others have noticed that silver nitrate goes black when light shines on it." "But Wedgwood experiment it with ways of using this to draw patterns what he called sun prints." "What I am going to do is to make a sun prints by wrapping my silver nitrate with this foil and then exposing it suddenly to a very bright light." "What we get are these blackened images where the silver nitrate has been hit by the light." "Deluged as we are by fantastic photographic images, these grey splodges looked rather unimpressive," "But in 1770, they gave a glimpse of a wonderful future." "Wedgwood and his collaborators were absolutely fascinated by this process of sun printing." "Because what is meant was that there might be a way of preserving forever the information that light carries to the eye." "The dream of enlightenment immortality was turning into the reality of photography." "Within 50 years of Wedgwood's experiments, paper soaked in silver nitrate was being used to capture real images." "Photography became a craze." "The expose is going to have to be about 30 seconds." "OK." "Stand probably with your head or your shoulders so that they can supported by the mantelpiece behind you." "Now this could make you bit of uncomfortable, could you draw yourself up a little." "Photography pandered to the vanity of middle class" "Europeans, cause having your own portrait was now affordable." "Photography was a very seductive and popular art, but I think it was also seen as extremely threatening." "All sorts of social boundaries were broken down or breached by the new photography process." "Things you weren't supposed to see, places you weren't supposed to look at, images that were not for popular consumption, the boundaries between elite tastes and vulgar industrial tastes, all these fences were being torn down by the chemical process of photography." "29... 30." "Thank you very much." "Photography was crucial to Florence Nightingale campaigns to improve military hospitals, it helped fund the salvation army, and it brought home to the public the horrors of the American civil war." "But photography will do more than uncovering social secrets, the ability to capture light would reveal unimagined truth about the natural world." "It would revolutionize biology, engineering, and ultimately through physics, take us into a new dimension." "It started with a simple question, what happens when a horse gallops?" "In the age of the horse, it was an old question as how exactly they move when they galloping." "Do their feet, all, simultaneously, come off the ground?" "Now that was an ancient question, but you couldn't solve it with the naked eye" "Eadweard Muybridge, a photographer on the west coast of America, was commissioned for a bet, to use this new fangled technology to prove once and for all, how a horse really moved." "Muybridge's plan was to use 24 cameras placed in a row across the race track, each attached to a trip wire." "And when the horse galloped past, its exact movement at that instant will be caught on camera." "Muybridge then developed the photos and had a series of amazing images of horses moving quickly." "It was true that at one point in the gallop, the horse takes all its fee off the ground." "Something you could never see with the naked eye which the camera had now revealed for the first time." "But the ability to freeze motion with a photograph was far more than a gimmick, others believed that if they could examine animal motion in fine enough detail, they would be able to replicate it, artificially." "A French scientist, Etienne Marey, had a particularly audacious dream" "Using Muybridge's cameras, he hoped to discover the secrets of flight." "But it turned out pretty quickly that birds are just too quick and move in far too complicated way to be able to be photographed the way Muybridge took pictures of horses." "So Murey cast about for another kind of camera, and he found one." "A camera that worked like a gun, when you fire it, it took an enormous number of shots each second, so what Murey would do would be to point this gun at a bird and follow it through the sky taking first hundreds and then thousands of shots each second." "The scientific study of bird motion now became possible." "And by the end of the century, Murey's photographs, not just of flying birds, but also of how winds controlled and are effected by the air flow around them were being used to design the very first effective flying machine." "Photography not only revealed what you couldn't see with the naked eye, it let humans reveal their own dreams." "Murey's bird photos directly inspired the" "Wright brothers who built the first aeroplanes." "And his camera was adapted into the first movie camera by the Lumiere brothers," "By 1900, in this world of new technological wonders, scientists finally believed they could explain what light was." "Building on Thomas Young's idea that light is a wave, the great Scottish scientist James Clerk Maxwell showed what this mysterious wave were." "Pulses of electromagnetic energy." "Humanity's long quest to understand light seemed over." "Light, it was argued, was completely understood, we know what it is, we know where it came from, and we know where it is going, light is a form of electromagnetic radiation which travels through empty space at a finite measured speed," "and the physics of light, the technology of light became a kind of symbol of the great successes of physics and engineering and the whole of science." "But there was a dramatic twist in the tale, enter a Swiss patent clerk, called Albert Einstein, aged just 25, using the idea that light was an energy wave, Einstein was forced to conclude that all the laws of physics needed to be completely rewritten." "To understand how Einstein could think so differently from his predecessors, picture the world in which he grew up." "So imagine you were living in an European city around 1900, your world had completely changed, you saw people whizzing past on bicycles, the first horseless carriages, motorcars, you could go to the cinema, and see exact reproductions of what it is like" "to move really fast through space, through time." "Einstein¡¯s was the first generation went to the cinema." "And like most people, he loved watching how time could be played with, speed it up, slow down, and even frozen." "Einstein began to realize that time might variable in the real world too, and you'd experience it if you could travel like a beam of light." "And he certainly began to imagine what it would be like sitting on a light beam traveling through space, all sorts of paradoxical effects, he quickly worked out would follow," "Flying along a light beam into the depth of space, Einstein would see a reality completely different to the normal one." "Time would stop, distance stretch out, it was just as weird as a cinema trick." "And 1915, he published on his general theory of relativity, an astonishing intellectual achievement, it declared that humanity's most basic intuitions about space, time, and light cannot be trusted." "Now Einstein's big idea was that when light travels near a heavy object, like our sun, it bends" "What the gravitation of a very heavy object does is to distort space and time." "Near very heavy objects, straight lines curve." "Put in another way, a vast entity like a star makes empty space, the void itself, curve," "it seemed bizarre, but if Einstein's incredible idea was right, it could be proved by looking at the stars." "Near the sun, light will change direction, it will curve, and the apparent position of stars beyond the sun will shift." "We will be able to see stars in positions that weren't there before." "But normally the sun is so bright; that it blanks out the stars that is in the sky behind it, there is only one rare occasion, when we can see the stars behind the sun, and that is during a total eclipse." "During an eclipse, the sun's disk is completely darkened, the temperature drops, and the sky seems to be extremely dark." "Some of the stars, which the sun's light otherwise is too bright for us to see, some of those stars suddenly become visible," "What you want to do, is take a photo of a star you can see just past the sun's edge, and that would mean, that the light wave from that star is coming really close to the sun." "If Einstein is right, then that light ray will bend a bit, and the star will seem to have shifted from where it normally is when the sun is not there." "Einstein worked really, really hard, to trying get astronomers to watch stars during a solar eclipse, because if those stars seemed to shift position a bit, then his theory will be proved right." "In 1919, there was a total solar eclipse, and a team of the finest British astronomers, led by Arthur Eddington, armed with best telescopes and photographic equipments went to Africa and" "Brazil to prove whether Einstein's mad ideas about space and time were true." "The scientific world held its breath and waited for the result." "It took months to do all the comparisons and calculations, but at a meeting of the prestigious royal astronomical society in London in November 1919, Eddington and his colleagues were able to stand up and say: our photographic data proves, unambiguously, that Einstein is right." "A small shift of stars had completely changed the world." "All of a sudden, literately overnight, Einstein became a world celebrity." "The new Newton, a global hero, there were cartoons of the whole of earth with a single flag attached to the planet, saying simply:" "Einstein lived here." "He became not just a celebrity, but kind of figure, of what it was to be a scientist, what it was to be a genius, and I guess what it is to obscene the secrets of universe." "one person who visited Einstein said visiting" "Einstein is like visiting 4th dimension." "He stopped being a human being, he became a force of nature." "And the drama with which this revolutionary discovery was proclaimed put the new science of light right at the center of the news media, it made the physics of light into a global event." "But above all, what Einstein had done was overturn 3000 years of thinking about light." "Every philosopher, from the ancient Greeks to 9th century Arabs, from medieval monks to Isaac Newton, from Galileo to Maxwell, had unquestioningly accepted one fact about light: it travels in straight lines," "And now Einstein had shown that even this was wrong." "So Einstein was right, light don't travel in perfect geometrical straight lines, but it travels through a space and time that is curved." "that makes light as it were depart from the straight and narrow." "Light had once be the sign of reliability." "It had been a tool for astronomers;" "it had been their basic technique for finding out how the cosmos worked." "Now it turned out, that far from being a tool, light was a puzzle, it was a problem, it twisted, it turned, it bend, it strayed." "Einstein's world became a world in which light needed to be teased upon, and in which the message that light brought from the most distant stars was a puzzle, and a challenge to human intellects."