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| An Excursion In Modern Physics. by Nobody: 12:39pm On Jun 24, 2018 |
Hi there! It's Teempakguy again.  It's been a while!  and I'm finally back again with my annoying science threads. I hope to keep this constant so please book your seats.Today were going to talk about time and space, and how a man who thought differently, completely changed our perception of what reality is. This thread will be ongoing and I won't finish it up at once because the subject is broad and there are some equations involved[which I have to edit via laTex] but I assure you it's going to be very interesting! So off we go. The Achievements By 1900, physics was an established field of study. We had managed to developed a rigorous system of mathematical and analytical physics to understand the world. We actually managed to find the mass of the sun, earth, and that of other planets. Using calculus and several contributions from several mathematicians and physicists, we developed a strong explanation of how the universe appeared to work. We had developed an outstanding explanation of sound, heat, and light waves. Electricity and the structure of the atom had been understood to some extent. You might wonder, well, that's cool! What else do we need? Indeed that was the prevailing thought then. A professor is even quoted as telling max Planck that physics was "almost at an end." All that remained was "A few little problems" And it turns out, one of those problems concerned something called a "frame of reference" Frames of references In physics, we have a need to often know where things are located. No, seriously. In physics, we are concerned with motion so it follows that we need to know where objects are located. Now, in order to locate objects, we need reference points. Something that is constant that we can use to compare with objects. For example, by picking a signboard at your area, you can describe your location with respect to the signboard location. This is called a frame of reference for obvious reasons. But then in physics, we find that everything is moving. Almost nothing is stationary. Even the sun is moving, not to talk of the earth. So how do we then locate objects with respect to objects that are moving? Well, several years earlier, Galileo discovered that if you are x meters from an object which is moving at speed v, then you can describe your position, x' , at any later time as x' = x + vt (called Galilean transformation) For example. If that signboard of ours is moving at speed 50km/h, and our house is currently 30km away from it, if you are planning to arrive at our house 1hr after being at the sign board, when you arrive, our house will be 30 + 50km/h *1h = 80km away from the signboard. So in this case, our signboard is a *moving* frame of reference. Even though we can use it to find the location of a stationary object, it is moving as well. This concept extends to the idea of an inertial frame of reference. inertial frames of reference In the 17th century, Sir Isaac Newton, the greatest physicist of old proposed three laws. The first is that an object will remain stationary or move in a straight line with constant speed unless you apply a force. Remember, this law is entirely dependent on how we pick our positioning system. Imagine if you are measuring the position of an object and you are standing on a moving seesaw, it will appear to be moving up and down even though there is no force acting on it! So in order for the law to be valid, we have to define what kind of reference frame it is valid in. This kind of reference frame is called an inertial frame and it is any frame of reference which is not accelerating. Seriously, that's it. If you are in a non accelerating place or object, the laws of Newton will hold perfectly for you-- and here's the kicker: your speed does not matter Now, if you think about this, you will realise that it means that if you are moving at a constant speed, you cannot know what speed at which you are moving or even if you are moving at all. (Kind of like how we're on earth which is moving and we don't know.) Honestly, even if you see another moving object, you still can't tell whether you're moving or not. Because you can always argue that the object is moving and you aren't and they can always argue that they are not moving and you are. Now since all physical laws can be derived from Newton's laws, we reach a single significant result which is a major cornerstone of physics: In all inertial frames, regardless of speed, or lack thereof, the laws of physics hold in the same exact way. This simple rule turned out to be a major troublemaker in years to come, a classic problem of a solution creating extra problem.  7 Likes 7 Shares |
| Re: An Excursion In Modern Physics. by Nobody: 12:47pm On Jun 24, 2018 |
@ johnydon22 and Ujsizzle. Please watch out for this thread, you might find it an interesting addition to the science library. |
| Re: An Excursion In Modern Physics. by Nobody: 11:34am On Jun 25, 2018 |
Waves imagine a large crowd of people standing in a field. there is no microphone and one person wishes to pass across information to the other members of he crowd. In this scenario, the person can speak into someone's ear, who is expected to speak into the ear of someone else. in this manner, the information travels around the crowd without anybody actually moving. this is the concept behind a wave. imagine a large and massive sea of particles, all floating around. these particles interact with each other. now imagine that you gave a few of these particles kinetic energy. since they are all interacting, they share this kinetic energy with each other as a wave that travels outward from the source of the energy. This is kind of what happens when you drop a stone into the water or make noise; the sound or water wave travels outward from the source, transferring energy to all the other parts of itself. in other words, we can define the concept of a wave as a way in which a medium updates itself. from this, it makes sense that if you're going to have a wave, you should have a medium in which the wave is to propagate. I mean, the point of a wave is that a medium is trying to update itself by transferring energy with which to update the position of other particles in that medium. what we can say about waves When we talk about waves, there are always several things we can define about it. for instance, we can define the amplitude, of the wave, which is a measure of how much disturbance the wave causes to the particles it passes through. usually, it depends on the energy it's trying to transmit. obviously, if you drop a coin into the sea, you'll get a wave, but compare that wave to the sort of wave you get when you drop a massive meteor into the same sea. the difference here is amplitude. you can also talk about the wavelength, which is how long the wave is, you can talk about the frequency, which is what you get when you take a portion of the medium and you talk about how many such waves can pass there during that time. most importantly, we can talk about the speed of the wave. This is how fast the wave is moving. and in this case, we find it very interesting to study the speed of a wave because you'll remember, we said earlier, it is impossible to discern whether you are moving or not as long as you are not accelerating. so what if you're moving along a medium with the speed of a wave that's moving in that medium  you'll see a stationary wave. if you're moving faster, you'll see a wave moving in the opposite direction.so in short, the speed of a wave in a medium to you also depends on the rate at which you're moving with respect to the wave. Light and The ETHER One of the great achievements of science is the proof that light is a wave. this proof was supplied by a brilliant physicist named john clerk Maxwell when he presented, and subsequently solved, a group of four partial differential equations that are now known as Maxwell's equations. he was able to extract a wave equation from these equations, solve the equation and determine the speed of the wave which turned out to be light. Now, let's look at these set's of logical implications. -- Light is a wave -- waves propagate in a medium -- therefore light propagates in a medium -- however light propagates in a vacuum -- therefore, even in a vacuum, there is a particular medium. -- the entire earth exists in a vacuum -- therefore the medium of a vacuum surrounds the earth -- therefore, the speed of light should depend on the speed at which the earth moves with respect to the medium of the vacuum. -- therefore knowing the speed of light from different directions, the speed at which the earth moves with respect to the medium of the vacuum can be determined. And so it was set that the next goal of physics was to determine the speed at which the earth moved with respect to this particular vacuum medium. while they were at that, they named this hypothetical medium. they called it ether. so then, the ether was defined as; that medium that permeates the entire universe, both in a vacuum and in matter, whose purpose is to account for light propagation in a vacuum. LOL, reminds me of dark matter. now, let's look at a few logical implications. IF there is an ether, then it is either stationary with respect to earth or not. IF it is stationary with respect to the earth, then it is not stationary with respect to other celestial bodies. IF it is not stationary with respect to other stationary bodies, then we should be able to measure different speeds of light for different parts of the universe. HOWEVER IF we always measure a constant speed of light for a part of the universe of the earth that is not stationary with respect to earth, then earth is NOT stationary with respect of the ether. THEREFORE, on earth, we should measure different speeds of light coming from different directions. The emboldened statement is the epitome of what science is about. IF you have a theory of how the world works, it must make a prediction that CAN BE TESTED. if your theory cannot be tested, YOUR THEORY IS NOT VALID. the above experiment is also what a brilliant physicist named michelson set out to test. 1 Like 2 Shares |
| Re: An Excursion In Modern Physics. by johnydon22(m): 11:37am On Jun 25, 2018 |
I'm here!!! |
| Re: An Excursion In Modern Physics. by Nobody: 4:59pm On Jun 25, 2018 |
johnydon22:you're highly welcome sir. |
| Re: An Excursion In Modern Physics. by bqlekan(m): 7:55pm On Jun 25, 2018 |
following |
| Re: An Excursion In Modern Physics. by Blakjewelry(m): 8:12pm On Jun 25, 2018 |
ride on |
| Re: An Excursion In Modern Physics. by Mirallas: 9:52pm On Jun 25, 2018 |
The famous Michelson-morley experiment.� |
| Re: An Excursion In Modern Physics. by Nobody: 8:27pm On Jun 26, 2018 |
the properties of a flowing river come, imagine with me. assume you have a river with speed v, flowing along to the right. And you have two canoemen. they have the same speed which we will call c and they are to cover the same distance which we will call d, only; one guy is covering his distance by crossing the river and crossing back, and the other is to cover his distance by going towards the right and coming back. now, we wish to find out how long it takes for each guy to complete their journey. for those who are unable to visualize, here is an image which I found on the internet. [img]http://skullsinthestars.files./2011/05/river_michelson.jpg[/img] due to nairaland's inability to support latex, I'm having some issues with the mathematics, however, the main gist is that the guy who goes across the river and comes back actually finishes the race faster than the guy who goes along the flow of the river and has to come back. Albert Michelson and Edward morley used this concept to try and determine the flow of aether. The grand experiment The exeperiment occured in 1887. assume that you have your aether as the river in the analogy i gave earlier, and your two boatmen are your light beams, naturally, you should expect to find one light ray taking less time to go and come back than the other, and thus, you can infer the direction in which the aether is flowing. so basically, you expect that since the earth is moving through the aether at constant speed, then the aether should appear as a wind moving relatively to the earth and using the concept of two items with fixed speeds moving perpendicularly, you want to know the direction in which the aether wind is moving. The great experiment . . . failed. They detected NO change in travel times. That's mindblowing. that's like having a race and then you have a favourite runner so you cheated by shortening their track, only for their competitor to finish the race at the same time, but then you claim the competitor was running faster, but then he wasn't  The implications of this defy common sense; It's either that there is NO ETHER if this is true, then what does light travel in ? isn't light supposed to be a wave or EARTH is STATIONARY TO THE ETHER that isn't possible because the earth accelerates as it revolves around the sun, at some point, the earth would have to change speed with respect to the aether. or BY MOVING IN THE ETHER, DISTANCES ARE AUTOMATICALLY COMPRESSED IN THAT DIRECTION that would imply a complete change in the laws of physics as we know it. or THE EXPERIMENTERS WERE WRONG. er . . . the michelson morley experiment has been repeated severally over the past years with amazing increases in accuracy, no difference in travel times has ever been found. they weren't wrong, guys. As it turns out, this conundrum was solved independently by three guys But one of them stole the show with his original thinking and paradigm change. P.S we did have to update the laws of physics anyway. |
| Re: An Excursion In Modern Physics. by Nobody: 4:26pm On Jun 27, 2018 |
Mirallas:well, yeah, that one. |
| Re: An Excursion In Modern Physics. by Nobody: 4:50pm On Jun 28, 2018 |
An apology Good evening, folks, I'm sorry about missing an update yesterday. It just so happened that I had a mathematics test yesterday and I had to leave my computer at home for safety purposes. I then arrived so late to the house and i was so tired. A recap -- Light is a wave -- Light is everywhere -- All waves move in a medium -- Therefore, the medium that carries light is everywhere and we can call it aether -- The earth undergoes circular motion around the sun -- Therefore the earth is an accelerating frame -- Therefore it is not possible to have the earth stationary with respect to this medium -- Therefore, by a cleverly designed experiment, we can deduce how fast the earth is moving in this medium -- After the experiment was carried out, there was no indication of aether -- Therefore, our theory has to be modified. George Francis Fitzgerald His contribution to the field isn't ground breaking or revolutionary, but it is useful. He realized that if objects were to contract in the direction of motion, it would explain the null result of the michelson morley experiment. he even had an argument about the relationship between light and electricity and how that could affect the spacing within atoms due to their motion. Hendrik Lorentz Lorentz was a genius in his own right. I mean, he did win the second Nobel prize. He also did a lot of work on explaining the null result of the michelson-morley experiment and basically laid down the mathematical foundation for what the next guy did. He was able to derive a more accurate relationship between moving reference frames and objects which allowed for the result of the michelson-morley experiment. usually, in physics, even when we don't fully understand something, we can still be satisfied that if it is mathematically consistent, it will probably describe the world, and indeed, several equations in physics were derived before we actually understood what was happening behind the scenes. but seriously, everything that fitzgerald and lorentz did was just convenient mathematics. In physics, this is nice, but we do like fundamental theories that explain WHY something happens. Which is why the next guy made a lot of people satisfied. His name was Albert Einstein. |
| Re: An Excursion In Modern Physics. by Nobody: 9:12am On Jun 29, 2018 |
A new Idea the end of the 19th century and the beginning of the 20th century saw a lot of speculations on why the aether appeared not to exist. like we discussed earlier, lorentz and fitzgerald had already taken stabs at the problem and were able to find mmathematical explainations for the effect. what no one knew was WHY. enter James Clerk Maxwell. It turns out that when he derived the equation of the speed of light, it was not a variable at all. in fact, it did not depend on anything except two other constants. This implies that the speed of light itself is a law of physics. it's actually funny how no one made this connection, every was stuck on the idea that since light is a wave, then it must need a medium in which to exist. Ironically, unlike many other waves, the speed of light does not depend on anything except two universal constants, that alone points to the fact that it's a special kind of wave.  now, recall our earlier assertion that the laws of physics are the same in all inertial frames. now, connecting it with our previous bolded statement, that implies that the speed of light is the same in all inertial reference frames and BAM. the theory of special relativity was born. Now, let's look at these set of logical reasonings. -- the derived speed of light depends only on universal constants -- therefore the speed of light should be a universal constant -- this would make the speed of light a law of physics on it's own -- the law of physics are the same for all observers moving with constant motion -- therefore, the speed of light is the same for all observers moving with constant motion. meaning that for someone standing still and someone moving at 99.9 percent of the speed of light, they will both measure the same speed of light. now, we will now logically derive all of the results of special relativity. there won't be any mathematics because some people might not understand it as much as they would a logical derivation, however, I will include an image for the main results. Why NOTHING can travel faster than light. -- light has a speed that is constant for all observers -- therefore, a chunk of light that is traveling is the same speed for the person who is stationary and the person who is moving fast. -- if someone were to move at the speed of light, it would appear stationary to them -- however, we have shown that light must be moving ahead of them with some speed -- therefore, they cannot catch up to light -- therefore, they cannot even move faster than light. note; the limit on light speed is actually not that simple, the fact is, due to time dilation, you can actually move at whatever speed you want, but for other observers, it will be adjusted to ensure that you do not exceed the speed of light, which leads us to the concept of time dilation. time dilation -- the speed of light is constant -- if you release a light beam while moving, the speed of light to you should be c - u where c is the normal speed of light and u is your speed. -- but that doesn't happen, you still measure the speed of light to be the same. -- however, speed depends on time. -- therefore, while moving, something must have happened to your clock. -- since you are measuring the speed of light as the same as the person who is stationary, despite the fact that you are running, then that means you have a slow clock. -- the speed of light is the same for all observers regardless of speed -- therefore, the faster you move, the slower your clock is. this gives rise to the concept of length contraction length contraction -- If the speed of light is the same for all observers, then it must cover the same distance as measured by an observer -- imagine a ruler of length l that is also moving in the direction of light as observed by someone stationary. -- As the light beam crosses one end, the ruler also moves so that the end of the ruler is now a bit farther from where it was before, which means that light has to travel a longer distance as measured by the stationary observer. -- meanwhile, someone that is moving the ruler sees it as stationary, therefore, light travels a shorter distance to them. -- but since light speed is constant, then for all observers, light goes from end to end in the same time, both for the person moving with the ruler, and the stationary observer -- therefore, light just covered two different distances at the same time. -- but the speed of light is constant -- therefore, the length of the ruler must appear shortened to the stationary observer to ensure that with the same speed, light moves from one end to the other in the same time for everybody. -- the faster you move, the more extra distance light has to cover. -- therefore, the faster you move, the shorter your length appears to stationary observers. lastly, we look at simultaneity. -- If the speed of light is constant, then it must cover equal distances at the same time. -- thus for a light released at a point, it must strike a point 5 meters ahead and 5 meters behind at the same. -- but if the light source and those points are moving forward relative to a stationary observer, they will observe that the light strikes the behind first before the point ahead due to the points themselves moving towards the front. -- therefore, two simultaneous events in one reference frame are not necessarily simultaneous in other reference frames. What to take from all this. the world is more complicated than we can care to assume. The laws of physics aren't what they appear to be. For instance, your speed has an upper limit, not everyone can say things occur at the same, moving things are always shortened in the direction of their motion, time moves more slowly for things that move faster . . . and most fascinatingly, all of this strange results come from these two postulations; 1. the laws of physics are the same in all inertial reference frames 2. the speed of light is therefore the same in all inertial reference frames. the ability of Einstein to generate so many original non-intuitive results from the above starting point is perhaps why several scientists consider him to be one of the greatest geniuses to ever live. he offers an advice that many might find useful and which is undoubtedly a secret to his outstanding success in physics; Imagination is better than knowledge. 3 Likes 1 Share |
| Re: An Excursion In Modern Physics. by Mirallas: 9:17pm On Jun 29, 2018 |
Following.I am enjoying this, Nice work. |
| Re: An Excursion In Modern Physics. by horlahwaley(m): 11:09pm On Jun 29, 2018 |
nice one op, am enjoying dis |
| Re: An Excursion In Modern Physics. by Feraz(m): 1:27pm On Jul 02, 2018 |
Signing up. Welcome Teempakguy! |
| Re: An Excursion In Modern Physics. by Nobody: 10:35pm On Jul 02, 2018 |
Feraz:it's good to be back.  |
| Re: An Excursion In Modern Physics. by BaEnki(m): 1:08pm On Jul 03, 2018 |
Welcome back Teempakguy, I've missed your contributions so much, very intuitive writings. Maybe you have to present backed up equations in an handwriting form, then snap and upload them. |
| Re: An Excursion In Modern Physics. by Nobody: 6:11pm On Jul 04, 2018 |
BaEnki:cool plan. actually, I've considered this thread completed, but your idea sounds great. |
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