Newton proposed light travels in a straight line.But how is it possible for him to predict interference theory
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Newton's optics was based on light particles (photons). He could not have know about interference since no source of coherent light existed at the time for him to experiment with.
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As weird as it sounds, the theory of relativity says that if you are in a car traveling at 200,000,000 m/s with the headlights on, then the light from those headlights will pass a person standing still at 299,792,458 m/s and not 499,792,458 m/s. And if that stationary person shines a light at your car, you will see his light approaching you at 299,792,458 m/s and not 499,792,458 m/s.\n\nThe theory is so weird that numerous scientists have done numerous experiments to test it. The most famous of these experiments is the Michelson-Morley Experiment. All experiments have confirmed that this strange prediction of relativity is true.\n\nBelieve it or not!
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Theory of relativity.
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Since they already told you the mathematical answer, here is the conceptual one.\n\nImagine this:\n\nYou are standing in a lab. Your friend is standing on a kart on which a light clock has been built. The clock consists of two mirrors. One if mounted on the floor of the kart and the other is supended above it. The mirrored sides are facing.\n\nA photon of light bounces between the two mirrors. It hits the bottom mirror every second. Now your friend syncronizes the light clock to your watch so they both tick at the same rate.\n\nThen the kart is set in motion and travels with a velocity which is a large percentage of the speed of light.\n\nFrom your friend's point of view on the kart, the photon is still going up and down. But from your point of view, as the kart goes by, the photon is going up and down while moving sideways along with the kart, so it appears to you that it takes a diagonal path up and a diagonal path down.\nTrigonometry tells us that the diagonal path is longer than the straight up or down that your friend on the kart see's. Now this is the tricky part...\n\nFor the photon to hit the mirror at the same your watch ticks, traveling the path that you see it taking, it HAS to speed up because it has farther to go. The problem is, it can't speed up because the speed of light is constant. As a result, your watch ticks before the photon hits the mirror and to you it appears that the light clock is running slow. To your friend, the light clock is running just fine. This means that to you, EVERYTHING on the kart is running slow, and time on the kart has slowed down.\n\nNow, the same thing is going on from your friend's point of view when he looks at you on the ground as he goes by on the kart. Your watch looks like it's running slow, and everything you do appears to be running slow and from his point of view, your time has slowed down.\n\nBack to the kart, the faster it goes, the longer the path you see the photon take becomes, which means that the less diagonal and more horizonal it becomes. It never becomes completely horizontal for mathematical reasons but it comes close enough to it such that the photon NEVER gets to the mirror it was traveling to. What's happening on the kart from your perspective? Time has stopped.\n\nPretty funky eh?\n\nAccording to the actual equations, we cannot exceed the speed of light and time can't go backwards. That may be correct or it may be that there is what's called a discontinuity...basically where the rules of the game change in the middle of it.\n\nExperiments indicate that things may be able to occure faster than the speed of light, however, information itself cannot be transmitted faster than the speed of light.
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The property of light is that it takes the shortest route possible between 2 pts. IT IS A WRONG IDEA THAT THIS PATH IS A STR LINE. A str line is the shortest dist in Eucidean Goem, the geom of the Universe is NOT EUCLIDEAN IN NATURE. As for your other ideas, I pt out that a photon never stops travelling unless it gives up its energy. DO NOT USE NEWTON'S LAWS ON THE PROPAGATION OF LIGHT. THE PROPAGATION OF LIGHT IS EXPLAINED BY 2 THEORIES-\nMAXWELLS THEORY OF ELECTROMAGNETISM, speaking of the WAVE ASPECTS\nEISTEIN'S GENERAL THEORY OF RELATIVITY, speaking of the particle nature. GO through these when you r of the proper age to do so, let me warn you that studying the true nature of light requires a huge pre-knowledge of physics and it is very difficult and controversial.
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In 1676, by a Danish astronomer, Ole Römer, working at the Paris Observatory. He had made a systematic study of Io, one of the moons of Jupiter, which was eclipsed by Jupiter at regular intervals, as Io went around Jupiter in a circular orbit at a steady rate. Actually, Römer found, for several months the eclipses lagged more and more behind the expected time, but then they began to pick up again. In September 1676,he correctly predicted that an eclipse on November 9 would be 10 minutes behind schedule. This was indeed the case, to the surprise of his skeptical colleagues at the Royal Observatory in Paris. Two weeks later, he told them what was happening: as the Earth and Jupiter moved in their orbits, the distance between them varied. The light from Io (actually reflected sunlight, of course) took time to reach the earth, and took the longest time when the earth was furthest away. When the Earth was furthest from Jupiter, there was an extra distance for light to travel equal to the diameter of the Earth's orbit compared with the point of closest approach. The observed eclipses were furthest behind the predicted times when the earth was furthest from Jupiter.\n\nFrom his observations, Römer concluded that light took about twenty-two minutes to cross the earth's orbit. This was something of an overestimate, and a few years later Newton wrote in the  Principia (Book I, section XIV): "For it is now certain from the phenomena of Jupiter's satellites, confirmed by the observations of different astronomers, that light is propagated in succession (NOTE: I think this means at finite speed) and requires about seven or eight minutes to travel from the sun to the earth." This is essentially the correct value.\n\nOf course, to find the speed of light it was also necessary to know the distance from the earth to the sun. During the 1670's, attempts were made to measure the parallax of Mars, that is, how far it shifted against the background of distant stars when viewed simultaneously from two different places on earth at the same time. This (very slight) shift could be used to find the distance of Mars from earth, and hence the distance to the sun, since all relative distances in the solar system had been established by observation and geometrical analysis. According to Crowe (Modern Theories of the Universe, Dover, 1994, page 30), they concluded that the distance to the sun was between 40 and 90 million miles. Measurements presumably converged on the correct value of about 93 million miles soon after that, because it appears Römer (or perhaps Huygens, using Römer's data a short time later) used the correct value for the distance, since the speed of light was calculated to be 125,000 miles per second, about three-quarters of the correct value of 186,300 miles per second. This error is fully accounted for by taking the time light needs to cross the earth's orbit to be twenty-two minutes (as Römer did) instead of the correct value of sixteen minutes.
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if light did not travel in a staight line then the mirror would make the light refract (focus)and since it does not it proves that light travels in a straight line
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>we know that physically one photon can not pass through the two slits at a time\n\nThat's kind of the whole point of considering the single photon case of the double slit experiment: it give results that don't match classical predictions, and so it becomes a good argument for quantum mechanics.  \n\nIf light were a classical particle, then yes, it can't go through both slits, and you'd end up with two overlapping Gaussian bands of light, and not an interference pattern if you summed up the results of many single photon experiments \n\nIf light were a classical wave, you'd get an interference pattern, but you'd expect the energy from it to be spread out all over the detector or photographic plate, just very faint.  \n\nWhat actually happens when this experiment is done is that the energy gets delivered to the detector all in one place, as if light is a classical particle.  But, the locations where the energy gets delivered, if the experiment is done one photon at a time and the results are stacked up, conforms to the interference pattern you'd expect from a classical wave.\n\nSo, we have something that matches neither a classical particle nor a classical wave in  behaviour.  \n\nBut, in quantum mechanics we have a description of something that does fit this behaviour.  That is, we have a wave which, when measured, has to provide energy in quantized steps.  To get from the wavelike portion to the particlelike portion, we have to recognize that there isn't a completely deterministic answer but rather a statistical one.  So, while this model descibes what a real photon does in the double slit experiment, it can't predict the exact behaviour of a specific given photon.  As best we can tell so far, this isn't just a shortcoming of the theory, it's actually how physical reality operates.\n\n\nEdit:  Ramblingman, it can be done with either an electron beam or a photon beam.  Both will show the same sort of effect, but traveling electrons will have a much shorter wavelength than light.  Quantum mechanics works for both things that were classically considered as waves, like photons, and things that were classically considered as particles, like electrons.
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Actually, the way modern physicists think of it, the question doesn’t quite make sense.  The problem is the “traveling at the speed of light” part, because one of the conclusions of Einstein’s Special Theory of Relativity is that nothing can travel that fast.\n\nInterestingly, though, its was consideration of a similar question that started Einstein down the path toward relativity… Light is best described by Maxwell’s Equations, which predict that any experiement will measure same speed for light in a vacuum.  When Einstein thought about traveling at the speed of light, he realized that there must be a problem.  In fact, Maxwell’s Equations don’t allow for a “standing wave” solution, which is what a light wave would look like if you were traveling at the speed of light. \n\nSo Einsten took things back to basics, which is what he was good at.  Let’s start with what he actually said… His Special Theory of Relativity started with two postulates (or assumptions): 1) that the laws of physics are observed to be the same in any non-accelerated “reference frame” and 2) that the speed of light (c) is observed to be the same for all observers.\n\nThe first assumption basically says that as long as you’re traveling at a constant speed, all your experiments will give the same results.  That seems reasonable.  But the thing about the speed of light always being the same sounds a little odd: the Michelson-Morley experiment (and others) had detected no change in the speed of light when measured from a moving frame of reference, however, and as I already mentioned, Maxwell’s Equations yield a specific value for the velocity of light.\n\nStarting from there, Einstein worked out how to add velocities together, and it comes out to be not simple addition, but a fraction that never gets larger than c. Basically, what happens is that the measurement of time and distance changes, so a physical object (e.g., a spaceship) can never achieve lightspeed.\n\nSo”  That’s a long-winded way of saying that your headlights themselves can’t travel at the speed of light.  If we want to think about them traveling very, very close to the speed of light, however, we realize that the light they emit still travels at lightspeed (as measured by the fast-moving headlights themselves), so they stil work the same way headlights would work on a car traveling much slower.\n\n\nRyan Wyatt\nRose Center for Earth & Space\nNew York, New York
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It is the results of Einsteins work on relativity. Einsteins showed gravity cause space-time to warp which will affect how objects interact with each other. Newton explained gravity as the attraction one object has for another, Einsteins theory's have made up for some of newton's short falls, such as Mercury's orbit which doesn't stay the same each time changes with each orbit. Newton laws don't account for this change but Einsteins theory's predict these changes exactly. Theory's of Space-Time were never design to explain the Ether.
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Your question is similar to Einstein's question that led to a revolution in physics, so it's not a stupid question by far. Einstein asked, what would happen if someone could travel along a beam of light? What would the traveler see? \n\nThink of relative motion. When I'm on a train, watching the country side go by, it appears to me that everything else is moving and I, the tables, the chairs, and the people on the train are not moving. If I were standing on the ground watching the train go by, it would be the oppisote: I would appear, to myself, to be standing still, and the train, people on it, chairs and tables would all appear to be moving. Relative motion, hense the term "relativity."\n\nWhat Einstein discovered is that even if one could travel at the speed of light, that person would observe the light in your headlight traveling away from him AT THE SPEED OF LIGHT. Weird, huh? Think about it. If you're on a ski slope and an avalance is chasing you, what are you going to do? You are going to RUN. Why? It decreases the rate at which the avalance is approaching you. If the avalance is traveling 20  mph and you can run 15 mph, the avalance is only gaining on you at a rate of 20 mph - 15 mph = 5 mph. You slow it's approach to you. However, that does not work with light. If you ran away from a light beam, and managed to travel at the speed of light, the light beam behind you would STILL BE APPROACHING YOU AT THE SPEED OF LIGHT. Light speed is constant in every reference frame, no matter WHAT the speed of the observer. \n\nIn short, you would see the light in the headlight traveling away from you at the speed of light.
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English physician and physicist who established the principle of interference of light and thus resurrected the century-old wave theory of light. He was also an Egyptologist who helped decipher the Rosetta Stone (see photograph).\n\nIn 1799 Young set up a medical practice in London. His primary interest was in sense perception, and, while still a medical student, he had discovered the way in which the lens of the eye changes shape to focus on objects at differing distances. He discovered the cause of astigmatism in 1801, the same year he turned to the study of light.\n\nBy allowing light to pass through two closely set pinholes onto a screen, Young found that the light beams spread apart and overlapped, and, in the area of overlap, bands of bright light alternated with bands of darkness. With this demonstration of the interference of light, Young definitely established the wave nature of light. He used his new wave theory of light to explain the colours of thin films (such as soap bubbles), and, relating colour to wavelength, he calculated the approximate wavelengths of the seven colours recognized by Newton. In 1817 he proposed that light waves were transverse (vibrating at right angles to the direction of travel), rather than longitudinal (vibrating in the direction of travel) as had long been assumed, and thus explained polarization, the alignment of light waves to vibrate in the same plane.\n\nYoung's work was disparaged by most English scientists: any opposition to a theory of Newton's was unthinkable. It was only with the work of the French physicists Augustin J. Fresnel and François Arago that Young's wave theory finally achieved acceptance in Europe.\n\nYoung also studied the problem of colour perception and proposed that there is no need for a separate mechanism in the eye for every colour, it being sufficient to have three—one each for blue, green, and red. Developed later by the German physicist Hermann L.F. von Helmholtz, this theory is known as the Young–Helmholtz three-colour theory.\n\nHaving become interested in Egyptology, Young began studying the texts of the Rosetta Stone in 1814. After obtaining additional hieroglyphic writings from other sources, he succeeded in providing a nearly accurate translation within a few years and thus contributed heavily to deciphering the ancient Egyptian language.\n\nYoung also did work on measuring the size of molecules, surface tension in liquids, and on elasticity. He was the first to give the word energy its scientific significance, and Young's modulus, a constant in the mathematical equation describing elasticity, was named in his honour.
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The general theory of relativity is much more complex and difficult to understand than the special theory. It proves the force of Gravitation, as proved by Sir Isaac Newton, wrong. According to Newton, gravity was a force between two bodies, which depends on their respective mass and the distance between them. \nThe basic idea of general relativity can be illustrated with the help of an imaginary experiment as performed by Einstein.  Suppose a lift is at rest in space.  If a ball is released within the lift, it will float in space and not fall.  If the lift accelerates upward, an observer within the lift will see the ball fall to the floor exactly as it would under the pull of gravity.  The ball appears to fall because the floor of the lift, as seen from outside the lift, it accelerates upward toward the ball.  All the effects we associate with gravity would be seen by the observer in the lift.  Einstein called the phenomenon shown in this experiment the Principle of Equivalence. This principle states that it makes no difference whether an object is acted on by a gravitational force or is in an accelerated frame of reference.  The result in both cases will be the same.  From this principle, Einstein reasoned that matter in space distorts or "curves" the frame of reference of space. The result of this curvature is what we experience as gravity. The Euclidian or flat geometry was unable to explain the curve, so Einstein used geometries called Riemannian geometry to explain the effect. \nAccording to Newton's theory, a planet moves around the sun because of the gravitational force exerted by the sun.  According to the theory of general relativity, the planet chooses the shortest possible path throughout the four-dimensional space- time, which is deformed by the presence of the sun. This shortest possible path is called a geodesic.  This may be compared to the fact that a ship or an aeroplane crossing the ocean follows the section of a circle, rather than a straight line, in order to travel the shortest route between two points.  In the same way, a planet or light ray moves along the "shortest" line in its four-dimensional world. \nSo far, three things have been discovered in which Einstein's theory of general relativity receives experimental proof as opposed to the theories of Newton.  These differences are not great, but are measurable.  In the first place, according to Newton's theory, the planet Mercury moves in an ellipse about the sun.  According to Einstein's theory, Mercury moves along an ellipse, but at the same time the ellipse rotates very slowly in the direction of the planet's motion.  The ellipse will turn about forty-three seconds of an arc per century (a complete rotation contains 360 degrees of an arc and 360 X 60 X 60 seconds of an arc).  This effect is rather small, but it has been observed.  Mercury is nearest to the sun and the relativistic effect would be still smaller for other planets.  \nIf we take a picture of part of the heavens during an eclipse of the sun and near the eclipsed sun, and then take another picture of the same part of the heavens a little later, the two photographs will not show identical positions for all the stars.  This is so because, according to general relativity, a light ray sent by a star and passing near the rim of the sun is deflected from its original path because the sun's gravity curves space.  The effect of gravity on light is also the reason why black holes are invisible.  The gravitation in a black hole is so strong that light cannot escape from it. \nPhysicists have known for more than a hundred years that when some elements are heated to incandescence they give off a pattern of spectral lines (coloured lines), which can be examined through a spectroscope.  According to the Einstein theory, the wavelength of light emitted from a massive object will become longer because of gravitation.  This results in a shift of the spectral lin
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Newton' and Einstein's on relativity
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Let’s start with what Einstein actually said… His Special Theory of Relativity started with two postulates: 1) that the laws of physics are observed to be the same in any non-accelerated reference frame and 2) that the speed of light (c) is observed to be the same for all observers.\n\nThe first assumption isn’t too worrisome, but the second seems trickier. It’s certainly not intuitively obvious, but it makes sense from both a theoretical and an observational perspective. Observational because the Michelson-Morley experiment (and others) detected no change in the velocity of light when measured from a moving frame of reference; theoretical because Maxwell’s Equations yield a specific value for the velocity of light.\n\nWhen Einstein considered Maxwell’s Equations, he realized that they don’t allow for a “standing wave” solution, which is what a light wave would look like if you were travelling at the speed of light. So he already sensed there would be a problem with travelling at very high speeds. Indeed, when you re-work the addition of velocities, it comes out to be not simple addition, but a fraction that never gets larger than c. Basically, what happens is that the measurement of time and distance changes, so a physical object (e.g., a spaceship) can never achieve lightspeed.\n\nHere’s where the infinite thing comes in.  Because the laws of physics must remain the same (remember the first postulate), then the changes in length and time at high velocities also start to affect the measurements of momentum and of energy—and since E=mc^2, mass and energy are equivalent, so mass itself has to change.  The rate of change has a term in the denominator that’s the square root of (1-(v/c)^2), so if the velocity (v) approaches the speed of light (c), then the denominator approaches zero; but if the denominator of a fraction approaches zero, then the total fraction approaches infinity.  Thus, you start to talk about problematic things such as infinite mass and energy and size.\n\nBut remember that nothing can actually travel at the velocity of light, so although this fraction should get very big, it shouldn’t actually become infinite.\n\n\nRyan Wyatt\nRose Center for Earth & Space\nNew York, New York
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Did you know that The same Isacc Newton invented the Calculus and aclculus is the best technique currently applied by physics of all dimentions to get the most accurate answer by spliting down a large problem into many different small steps of the problem inorder to get the most accurate answer available. thus generating the most effective solution in the world of physics.\nhe has contributed much to the society of man in the physical perspective. ironically he didn't have any prior mthematical knowledge when young.
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Michaelson and Morely did some experiments to try to see if the speed of light incipient on the earth was different for light coming from different directions.  Th idea was that if light travels in waves (as it seems to in many regards), then these waves needed to travel through a medium (like when sound waves travel through the air).  This medium was termed "the ethereal ether" and was thought to pervade space, including places with a vacuum; light was thought to be a wave travelling through it.  So Michaelson and Morely decided to try to see our speed relative to the ether by using somthing called an interfereometer.  This compared the speed of lightcoming from different directions.  The idea was that a star we are headed towards should reveal a higher speed of light, while ones we're rushing away from should have a lower speed, due to the Doppler effect.  What they found was that the speed was the same in all directions, meaning that if there was an ether, then we we perfectly at rest relative to the ether.\n\nThen mathematicians and physicists looked at the theories of Scottish physicist James Clerk Maxwell.  Maxwell had taken all existing theories on electricity and megnetism and unified them into a single, cohesive set of equations.  These equations showed how electricity could create a magnetic field, and a magnetic field could induce an electric current.  This could happen in such a manner that an electric field would induce a magentic field, which in turn induced an electric field, which in turn induced a magnetic field, and so on.  The equations made it clear that this wave would travel at a certain specific speed.  Incidentally, that speed was similar to the speed of light measured by French scientist Fizeau in 1849 (several decades earlier) and confirmed by Foucault.\n\nIt was all of this that led Einstein to formulate his special theory of relativity.  Since light moved as an electromagnetic wave, and since those waves had a speed that was predicted directly by Maxwells equations and was independent of the velocity of the observer, Einstein came to recognize that simultaneity was not a universal concept, and that time changed with velocity.  The idea of the ether was discarded as needless baggage.