The Ultimate Speed L imit -Written by Daniel Joseph Alapat

Contents ABSTRACT..................................................................................................................................................... 2

INTRODUCTION............................................................................................................................................ 2

ONE WAY SPEED OF LIGHT............................................................................................................................ 3

CAN BE BREAK THE SPEED BARRIER............................................................................................................... 6

ISN’T IT MOVING AT THE SPEED OF LIGHT.....................................................................................................7

CASE1................................................................................................................................................................7CASE 2...............................................................................................................................................................8CASE 3................................................................................................................................................................8CASE 4...............................................................................................................................................................9CASE 5...............................................................................................................................................................9CASE 6...............................................................................................................................................................9CASE 7.............................................................................................................................................................10CASE 8.............................................................................................................................................................10CASE 9.............................................................................................................................................................11CASE 10...........................................................................................................................................................11CASE 11...........................................................................................................................................................12

WHY DO WE WANT TO GO FASTER THAN THE SPEED OF LIGHT....................................................................13

WHAT WOULD MOVING FASTER THAN THE SPEED OF LIGHT MEAN.............................................................14

NEAR LIGHT SPEED TRAVEL......................................................................................................................... 15

CONCLUSION.............................................................................................................................................. 16

NOTES........................................................................................................................................................ 16

ACKNOWLEDGEMENTS............................................................................................................................... 16

REFERENCES............................................................................................................................................... 17

Abstract The speed of light is one of the most important topics in physics. It is so important because it tells us so much about our universe. The speed of light is the maximum speed at which any particle can travel, it’s the ultimate speed limit. The funny part is that we don’t know why it is so. This speed limits prohibits time travel and prevents us from going back in time like doctor who. In this paper I discuss different cases where the speed limit is thought to broken, why it makes meeting my ‘brother from another plant’ improbable and what happens when we try to break such rules in physics. I also discuss the very interesting theories of relativity and why light is special, it does not accelerate. So as soon as you light a match stick the light moves at the speed of light it doesn’t take time to acquire that speed.

Introduction“c” (in lower case) is used to represent the speed of light. Associated with the value 299,792,458 metres per second (approximately 3.00×108 m/s).According to Albert Einstein’s theory of special relativity, “The speed of light is the fastest, which all matter and information in the universe can travel.” This is also known as the cosmic speed limit.Why is c the symbol for the speed of light? The Latin word for speed of light is celeritas, it is the initial of this word (c) that is used to represent the speed of light.When I told my friends that I was writing a paper on the speed barrier, many of them asked me why such a barrier exists and why it is not possible to break this apparent barrier. Many others claimed of instances where this apparent barrier seems to be broken. However it is proven that it is impossible to break this barrier and that the fastest any particle can ever hope to travel is at 299,792,458 m/s.Most of my friends who had not taken up sciences in the 11th asked me what the importance of the speed of light is and how I was going to write 18 pages on a 9 digit number. The speed of light is very important and is used in many equations in physics, including one of the most famous equation in the world: E=mc2 (in fact this is not the full equation, this is

only for objects that are not moving. The full equation is {E^2= (mc^2) ^2 + (pc) ^2} we shall see its application later on. To understand the importance of speed of light we can look at the definition of a meter before and after the discovery of the speed of light. A meter was defined in 1793 as,

“One ten-millionth of the distance from the equator to the North Pole”

And later in 1960 as,

“1650763.73 wavelengths in a vacuum of the radiation corresponding to the transition between the 2p10 and 5d5 quantum levels of the krypton-86 atom”

However after the discovery of the speed of light it was redefined, in 1983 to,

“The length of the path travelled by light in a vacuum during a time interval of 1/299 792 458 of a second”.

O ne of the reasons this was done was so that the speed of light will have the value of a whole number.I feel that it should not be called the speed of light but the speed of a massless particle as all particles whose invariant mass is theoretically zero travel at this speed. The reason it is called speed of light is because the first massless particle to be discovered is light and hence the term speed of light is coined for all massless particles.

One way speed of light The speed of light is 299,792,458 m/sec. However this is the round trip average. What I mean by this is having light to travel in 2 directions and taking an average. Consider a hallway 299,792,458 meters long. At one end of the hallway we shall place a torch which is connected to a clock. We shall also place a light detector which is connected to the same clock. On the other end of the hallway we place a perfect mirror. At exactly noon we will turn on the flashlight for a split second sending out a light pulse. What would happen is that, the light pulse travels the distance of the hallway hits the mirror and comes back and the light detector records the time. You would find that the clock will read 2 seconds past noon.So now

The total distance is 299,792,458 * 2 = 599,584,936 metersTotal time taken is = 2 seconds

Average speed = total distance / total timeAverage Speed = 599584936 / 2

= 299,792,458 m/s

But we don’t know if light actually takes the same time to go out as it takes to come back.Let us consider the case where light takes only 0.5 seconds to go from the torch to the mirror but takes 1.5 seconds to cover the same distance on the way back. In this case also the clock would read 2 seconds. Or let us consider another case where the light travels from the torch to the mirror in 1.5 seconds and takes only 0.5 seconds to come back. In this case also the clock would read two seconds. You might ask why would it be different in different directions ,well I don’t know ,why would it be the same because right to left is not the same as left to right. It is different so light could move in different speeds in different directions. But the point is that we don’t know so let’s do an experiment to find out.Let us consider the same hallway but this time we will remove the mirror and place it with a light detector connected to a clock. For obvious reasons the two clocks would have to be synchronised, that is they have to read the same time, at the same time.Here comes the problem it is very hard to synchronise two clocks that are separated by such a distance. Most of you must be confused as you might have two clocks that read the same time or that you might have a watch that set’s itself according to atomic clock in Boulder.So then that’s what we will do. We will put a radio transmitter on one of these clocks and when the clock strikes noon the radio transmitter will send out a pulse to the other clock and it will record the time but there’s a problem. Even though a radio pulse travels fast it does take some time to reach the other clock and the hence the other clock will be a little bit slower. Normally this lag is not usually considered as it very minute but in this experiment we have to be precise if we want to calculate the speed of light.Well there is a solution we could set this clock a little bit faster than the other clock to compensate for the lag but for that we would have to know the time it takes for the radio pulse to travel and at what speed does radio travel. A radio pulse travels at the speed of light (we know that, cause if you turn on a radio transmitter and torch at the same time they will hit the wall at the same time) but the speed of light is what we are trying to measure. So you can’t do it that waySome people think that you can solve this by putting the radio transmitter in the middle of both the clocks but you see that will imply that radio pulse and hence light will travel in the same speed in one way as it does the opposite way.We cannot try this experiment with electricity or magnetic field or anything like that as it all depends on the speed of light. Now most of you might say why not bring the two clocks together, synchronise it and then we will move one of the clocks. But there is a problem here too. According to Einstein’s theory of special relativity motion effects the passage of time. The act of moving the clock from the other one causes it to be desynchronised from the other one due to time dilation. All of you who have learned about this theory would probably say that there is an equation which tells you how much it is desynchronised and that is true, it is:

And guess what this equation contains, the speed of light. The very constant we are trying to find out.Apparently calculating the one way speed of light is impossible. I am sure that some of you think that it is possible, but no it is not possible. Physicist have been trying to determine the one way speed of light for 100 years and no one has been able to do it. Everything you can think of, I can promise you it has been tried, and doesn’t work, there’s some catch you haven’t thought off.We get this paradox, Apparently it is impossible to synchronise clocks without knowing the one way speed of light and it is impossible to measure the one-way speed of light without synchronised clocks Conclusion Physicists consider the average round trip speed of light equal to the one way speed of light so it makes the math easier. But there is no real way to prove this. We can chose not to accept this and say that light travels faster in one direction than it does in the other direction and you can be correct.So you see the speed of light is a convention, like driving on the left side of the road, we all agree to it and it works however you can pick another convention you can go to the United States of America and drive on the right side of the road and that works just as well.Albert Einstein concluded:

“That light requires the same time to traverse the path a-m as for the path b-m is in realty neither a supposition nor a hypotheses about the physical nature of light but a stipulation which I can make of my own freewill in order to arrive at a definition of simultaneity” -Albert Einstein (relativity pp22-23)

Now what if you want to choose that light travels at different speeds in different directions, well you are right as well, however calculations will become more difficult than they already are. If you still don’t mind then you will not be alone as this is the way many ancient cultures’ chose.However according to the English standard version of the bible:

“And God said, “Let there be lights in the expanse of the heavens to separate the day from the night. And let them be for signs and for seasons, and for days and years, and let them be lights in the expanse of the heavens to give light upon the earth.” And it was so.” Genesis 1:14 - 15

According to me when I read this I think that god made light and light fell on the earth after some time and light takes time to travel and light reached everywhere at the same time and not at different times so light must travel in the same speed in all directions.

Can we break the speed barrier According to Einstein:

E^2= (mc^2) ^2 + (pc) ^2(Where p is the momentum and c is the speed of light)

We can represent this equation as a right angled triangle as shown in figure:

 

From this it is easy to see that for an object that is in rest will not have any momentum and hence the equation will be E=mc^2. However if the particle in question is massless like light then mass =0 and hence E=pc Furthermore we can say the closer the energy of something is to pc the closer the something

E Mc2

pc

is to light and the mass is hardly mass at all. The side of the triangle which has mc2 is almost 0 and the triangle is almost a straight line.The velocity of an object is the speed of light times the ratio of the objects momentum to energy (v=c*(pc/e))

If your momentum increases pc get closer and closer to equalling your energy and your velocity becomes closer and closer to the speed of light However pc can never be equal to your energy as you can never be massless And thus your velocity can never reach the speed of light all because the hypotenuse of a right angled triangle is longer than its sides.

Isn’t it moving at the speed of light ? Case1The most common way people claim to break the speed of light is when you shine a laser at the moon and flick you wrist so that the laser moves the diameter of the moon in a fraction of a second and hence must be going faster than the speed of light. But this is an illusion. Nothing here is actually moving faster than speed of light, because the individual particles of light, the photons are actually only moving at the speed of light. Its just that they are landing side by side in such quick succession that they form a spot that moves faster than the speed of light. Let us see how it would be like if we were on the moon. Actually the point will be moving so fast it would be very hard for us to see it. Even If you could see it by the time the laser reached the moon the light would spread so much that the width of the laser would actually be almost 5 kilometres long.

Case 2Instead of a laser let us take a very, very, very long, rigid rod that did not bend such that if you flicked your wrist the end of the rod would move faster than the speed of light. Well this would not work as we know the fastest a force can propagate through an object is the speed of sound. That is because each atom has to bump in to the next one to propagate that force and in this process some energy would be lost in each transfer of the force. So actually very little of the force you put in will be transferred to the moon and the tip wouldn’t actually move at all.

Case 3If we had an aeroplane which has unlimited fuel. In theory it could accelerate and increase its speed and since it had more fuel it could still accelerate to a faster speed. In this process it could keep accelerating until it reached the speed of light and still keep on accelerating and hence go faster than light. There are few reasons why this wouldn’t work.One, terminal velocity I shall explain this with an easier example. Imagine I jumped off the top of the Burj Khalifa in Dubai, we know that the earth is pulling me down with an acceleration of 9.8m/s .Since the height of the building is 828 m. s=828m A=9.8 m/s2U=0V=?V^2 –u^2 =2asV^2=16228.8m/sV=127.39m/sUsing simple kinematics formula (v^2 –u^2 =2as) we can find that we will hit the ground at 127.39m/sec but actually we will find out that we hit the ground at a much lower speed. This is because there are other forces acting on us which we did not take into consideration like air drag. We would find that if I weigh 80 kg and if I was 1.8m tall I would hit the ground at a little less than 45 m/s and that is just if I am naked. How did I find this, well we know that air drag acts in the direction opposite to the force of gravity so when we reach a certain speed the force pulling us down (force of gravity) is equal to the force pulling us up (air drag) and therefore we would not accelerate anymore and fall at a constant speed.Therefore we can conclude that due to air drag we cannot reach the speed of light.

Case 4To get rid of air let us consider another case where the aeroplane is so well designed that the air drag is zero or better yet let us consider a rocket in space with unlimited fuel and let us also say that the fuel has no mass. This will also not work as the faster we go the harder it is to accelerate.  As I accelerate an object its kinetic energy (mv^2/2) increases. This counts towards its mass (kinetic energy is proportional to mass). Therefore at really high speeds, the contribution becomes significant. I use extra energy (mc^2) to compensate this and to accelerate it further. This is "stored" as kinetic energy, which further increases the mass/resistance to acceleration. (Energy is proportional to mass) This effect is exponential, until we approach light speed, where the effect becomes so large that an infinite amount of energy is required for a small acceleration, which enormously increases its kinetic energy, so it increases its mass so much that the next tiny bit of acceleration needs even more energy which would be infinity plus infinitySo the final bit of acceleration to reach light speed takes infinite time and infinite energy.Therefore this is not possible.

Case 5Imagine a machine that rotates very fast and at the two end of the machine two tubes made from Carbon Nano tubes, each 285km long. If the machine was spinning at more than 10,000 rpm’s then the two ends to the tubes would be moving faster than the speed of light. Well however smart this theory is, there are a few reasons this would not work.For every spinning object there is a force pulling it towards the centre this is called the centripetal force. The same force that you feel when you spin a keychain around your finger. This force is depended on the speed of the object squared. So if the speed was very fast, the force would be very great and the rod would break. Even if the rod was of one gram the centripetal force will be 300000000 newtons. Then again carbon nanotubes are unbelievably strong. Only a tube 8 centimetre wide could support that force, but an 8 centimetre wide tube would weight much more than 1 gram so the force would be much greater and we would need a wider tube to support this force but a wider tube would increase the force and hence this is not possible.

Case 6Let us imagine a substance much stronger than carbon Nano tube and that weighs much less. Even then the tip would not move at the speed of light this is because the substance is held together by electromagnetic interaction that is the interaction between all the charges that

make up the material. This electromagnetic force is due to the exchange of photons. And these photons themselves move only at the speed of light. You see two atoms interact because they send out photons which tells them that another atom is there and hence they bond to form a molecule these photons travel only at the speed of light so if an atom was moving at the speed of light the photons would not meet and the molecule would not bond So we conclude even if we had infinite energy and super strong substances stronger than any substance known to man, the photons which hold things together only move at the speed of light. Therefor matter which are made up of photons cannot move faster than the speed of light since photons themselves move at the speed of light.

Case 7Tachyons A tachyon or tachyon particle is a hypothetical particle that always moves faster than light. The term "tachyon" was coined by Gerald Feinberg in a 1967 paper titled "Possibility of Faster-Than-Light Particles". He had been inspired by the science-fiction story "Beep" by James Blish. Feinberg studied the kinematics of such particles according to special relativity. However in our current understanding of physics no such particle can ever exist.

Case 8NeutrinoA neutrino is a fermion (an elementary particle with half-integer spin) that interacts only via the weak subatomic force and gravity. The mass of the neutrino is much smaller than that of the other known elementary particles. Neutrino are so small that if an atom was the size the solar system then a neutrino would be the size of a golf ball. Or the sum of the three neutrino masses must be less than one millionth that of the electron.The neutrino is so named because it is electrically neutral—it is not affected by the electromagnetic force—and because its rest mass is so small that it was originally thought to be zero. The weak force is a very short-range interaction, gravity is extremely weak on the subatomic scale, and neutrinos do not participate in the strong interaction. Thus, neutrinos typically pass through normal matter unimpeded and undetected. There are millions of millions of neutrino but they are so small and do not interact with the surrounding that it was thought that it would be impossible to do any experiments with it.Before neutrinos were found to oscillate, they were generally assumed to be massless, propagating at the speed of light. According to the theory of special relativity, the question of neutrino velocity is closely related to their mass. If neutrinos are massless, they must travel at the speed of light. However, if they have mass, they cannot reach the speed of light.

In the early 1980s, first measurements of neutrino speed were done using pulsed pion beams (produced by pulsed proton beams hitting a target). The pions decayed producing neutrinos, and the neutrino interactions observed within a time window in a detector at a distance were consistent with the speed of light.In September 2011, the OPERA collaboration released calculations showing velocities of 17 GeV and 28 GeV neutrinos exceeding the speed of light. WHAT!! .Father than light? That cannot be possible. In November 2011, OPERA repeated its experiment with changes so that the speed could be determined individually for each detected neutrino. The results showed the same faster-than-light speed.However reports came out that the results may have been caused by a loose fibre optic cable attached to one of the atomic clocks which measured the departure and arrival times of the neutrinos. An independent recreation of the experiment in the same laboratory by ICARUS found no discernible difference between the speed of a neutrino and the speed of light.Currently, the question of whether or not neutrinos have mass cannot be decided; their speed is (as yet) indistinguishable from the speed of light.

Case 9The big bangThe big bang is said to have expanded faster than the speed of light. This statement is wrong cause it implies that space used to expand at the speed of light but doesn’t anymore. Never the less nothing actually really moved the speed of light just space expanded faster than the speed of light. We claim that nothing in space and no information can travel faster than the speed of light and space is not a thing, it is the absence of a thing so no law of physics is being broken here.

Case 10 Negative matter and wormholes Compressing the space in front of you and expanding the space behind you, so that you surf on a tidal wave of warped space. This tidal wave travels faster than light if driven by negative matter (an exotic form of matter which has never been seen.)However we do not know if negative matter even exists. The only viable way of breaking the light barrier may be through General Relativity and the warping of space time. However, it is not known if negative matter exists, and whether the wormhole will be stable. To solve the question of stability, you need a full quantum theory of gravity, and the only such theory which can unite gravity with the quantum theory is string theory. Sadly, the theory is so complex that no has been able to fully solve it and give a

definitive answer to all these questions or in English if we could understand space properly and warp space then we could in theory move faster than the speed of light but we are nowhere near understanding such complex stuff.

Case 11 Quantum entanglement Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently of the others, even when the particles are separated by a large distance – instead, a quantum state must be described for the system as a whole.So this means that if two quantum entangled particles are taken to the two end of the universe and if spins are tested at the same time, one will give a positive spin while the other will give a negative spin. So that must mean that the information from one particle travels a very long distance in almost no time at all. This means that information is travelling at speed faster than the speed of light. But actually this is not really useful information cause According to the no-communication theorem these phenomena do not allow true communication; they only let two observers in different locations see the same system simultaneously, without any way of controlling what either sees. Hence no real information is communicated and hence relativity is not broken.

Why do we want to go faster than the speed of light

I am sure that after reading this paper you would be confused on why so much resources are spent on trying to go faster than the speed of light.Why can’t we just accept that the speed of light is the fastest we can travel and since the fastest man has been able to travel so far is 39,897 km/h on the Apollo 10 which is only 3.696724 % the speed of light this question should not arise for many years.The speed of light is very fast for our day to day life. Light can travel around the earth 7 times in a second. That is very fast. If I were on a cycle, cycling around a circle of 200 meter circumference. It would take me 1498962290 Rounds and if I was traveling at 1 round a second it would take me 17349 days to complete the distance light covers in just one second and this is if I cycle 24 hours a day continuously until I finish.The problem is when we consider the whole universe the distances are so huge that the speed of light is very slow.Let us consider the closest natural satellite to earth, the moon. Light takes 1.3 second to travel from the earth to the moon so when Neil Armstrong was asked how he was feeling when he first stepped on the moon. The radio transition (which travels at the speed of light) took 1.3 second after it was send to reach him and another 1.3 seconds for his answer to reach earth and that is without taking into account the time it took for his brain to stimulate the response. Let us now consider the closest star, the sun. Light from the sun takes 8 minutes to reach the earth. Which means if the sun disappeared right now it would take 8 minutes for us to realise it. Similarly it takes 44 minutes for probes in mars to communicate with earth.If we take the closest solar system the Alpha Centauri which is 40 trillion km away from Earth – nearly 300,000 times the distance from the Earth to the sun. It is really hard for our brain to comprehend these large numbers so we measure in light years. “a unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 1012 km “ So if were to travel at the speed of light it would take 4.5 years to reach the closest solar system Alpha Centauri. If we want to travel to distant galaxies in a lifetime we must travel faster than the speed of light and this is why there is so many efforts are made to travel faster than c. In short Light seems pretty quick to us, because nothing is quicker. But it still creates significant delays over long distances. Space is so vast that aeons can pass before starlight reaches us. Since our spacecraft are much slower than light, this means that we might never be able to send them to the stars. So we may never get to meet any aliens, and as the joint propulsion conference concluded “it is improbable that we will reach other galaxies in a lifetime”

Well and for time travel to be possible, according to our current understanding of physics, we need to travel faster than light. So if you ever wish to travel back in time and kill your grandfather then you have to travel faster than light. But this will bring the issue of the grandfather paradox and the idea of multiverses which is another thing all together.

What would moving faster than the speed of light meanAlbert Einstein once wondered, what if he was in a train moving at the speed of light, what would happen if he held up a mirror. Would he see his face in the mirror?Albert Einstein felt that he should see his reflection. If that was the case how will it look like for a person standing outside the train, is the light from the face of the person to mirror moving at twice the speed of light. This is all very confusing let us consider a simpler example of a man sitting in a train moving at 3km/sec. He throws a ball at the 1 km/sec less than speed of light. Since moving very close to the speed of light is possible and not breaking any laws of physics. Now logic suggest that for a person outside. The ball will be moving at the speed of the ball + the speed of the train (3+c-1).But then if this was possible then breaking the speed of light would be very easy. So Albert proposed that since the mass must be the same. The time must be moving at different speeds for the person inside the train and for a person outside a train. He proposed the theory of Special relativity that is, motion effects the passage of time.Confused, here imagine a light clock (that is a light pulse trapped between two mirrors parallel to each other) on a bus and one on the bus stop. When the bus reaches the bus stop Jack gets on the bus and Jill waits for the next bus. Now when the bus starts moving Jill will see that the light clock which is with Jack on the bus travels in a triangular path so in the same amount of time that is taken for the light to start from the mirror on the bottom to go to the mirror on the top and return will be same for the clock at the bus stop since light travels at the same speed. So the distance travelled by both the light pulse will be different but the speed of light is the same and we know Speed=distance / time Let s1 be the speed of the light pulse on the bus and s2 be the speed of the light pulse on the bus stop S1=distance travelled by light pulse on the bus / time it tookS2= distance travelled by light pulse on the bus stop / time it took

We know that distance travelled by light pulse on the bus> distance travelled by light pulse on the bus stop But s1=s2 but this creates a problem, the time it took for both the light pulse will be different.But for us it took the same time, this must mean that time is not the same for everyone and time is slower for objects in motion as compared to objects at rest. If the speed of light was in fact not the limit and if it is possible to go faster than all textbooks have to be rewritten, theories have to be rethought, the theory of relativity will be no longer, calculations must be redone, that is why the announcement of that of the neutrino traveling faster than the speed of light was very controversial.

The theory of relativity is based on the fact that light speed is same throughout and that the speed of light in a vacuum is a constant. So if one day when I wake up and turn on the lights in the room and the light moves faster than the speed of light then the theory of relativity would be no longer but such a day is very improbable as the theory of relativity is so well tested and embedded in physics.Relativity is not what is relative to one another like a car is fast compared to snail, But what is not relative like the speed of light it is those things which are absolute however you look at it. Without such absolutes there can be no science.

Some people think that the speed of light is not constant as they have heard that the speed of light in water is 225,000,000 meters per second which is almost ¾ the speed in vacuum. This is partly true because light does take more time to travel in water but that is no because the speed is slower but because the distance is longer. Due to the particles in water light takes a longer path and hence the speed seems slower but in reality light is still moving at the speed.

Near light speed travel When we travel at very fast speed like 90 % speed of light then the laws of physics are a little different, well they aren’t different cause we experience them at regular speeds also but their effects are so minuet that you do not know it’s there. It’s like looking at something under a powerful magnifying glass. The dirt particles that you see is there when it was when you look at it with your naked eye only that you never realise it. When you walk towards me, if I am stationary then the time that you calculate to reach me will be less than what i calculate but this difference is so small that it is unrecognisable. Let us imagine us in a scoter going near light speed. As we approach the speed of light are field of view will decrease until it becomes a point that is infinitely small. This small circle which is our field of view would be blue shifted in the centre and red shifted on the sides.To people watching me I will appear blue as I approach them and red as I pass them.This is because the wave length of red light is very high and the wave length of blue light is very small.

Conclusion The speed of light is a constant and it is the fastest any particle can travel. It is a fundamental law of nature just as much as gravity. It is an absolute value which will not change. The speed of light is the ultimate speed of limit and sets limits on what humans can ultimately do, the universe is not required to be in perfect harmony with human ambition.

Notes1). the 'speed of light' in this article refers to the speed of all electromagnetic radiation in vacuum.2). Between 1960 and 1983 the metre was defined as: "The metre is the length equal to 1650763.73 wavelengths in vacuum of the radiation corresponding to the transition between the levels 2p10 and 5d5 of the krypton 86 atom." It was discovered in the 1970s that this spectral line was not symmetric, which put a limit on the precision with which the definition could be realized in interferometry experiments.

Acknowledgements There are many people who I would like to thank. Firstly I would I like to thank my friend’s- Saandra Nandakumar and Jacob Jose whose constant criticising of my logic made me think better. I would also like to thank my friend Akash Arun who was patient to listen to my theories and ask questions which helped me understand much better. I would also like to

thank the YouTube channels veritasium, minuitephysics and vsauce for making physics interesting. Lastly I would like to thank all my physics teachers who made me love this subject as specially ma’am Sheena who helped clear doubts which I encountered while writing this paper

ReferencesImage for formula of special relativity: https://www.google.co.in/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj2iNOYxv_PAhXBQI8KHeI5DekQjhwIBQ&url=http%3A%2F%2Fwww.citycollegiate.com%2FphysicsXII_17d.htm&psig=AFQjCNF-Ut_Sn5XmEMlrNV_pNETcczfpdw&ust=1477814489540645

images for the triangle and graph for e2=(mc2)2+pc2https://www.youtube.com/watch?v=NnMIhxWRGNw&t=65s

image for warped space drivehttps://www.google.co.in/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjRvvKRvsjQAhVJt48KHabBCjMQjRwIBw&url=http%3A%2F%2Fwww.andersoninstitute.com%2Falcubierre-warp-drive.html&bvm=bv.139782543,d.c2I&psig=AFQjCNEJH8GuSD8krkgsipC6c8NJN3_tRg&ust=1480320540334445

Definitions of a meterInternational Astronomical Union, Measuring the Universe: The IAU and Astronomical Units, retrieved 10 November 2013

One way speed of light:Jason lisle - https://www.youtube.com/watch?v=5vUel1AIM8w

Wikipedia - https://en.wikipedia.org/wiki/One-way_speed_of_light

Faster than speed of light:Veritasium - https://www.youtube.com/watch?v=vVKFBaaL4uM

Can we break the speed barrier: https://www.youtube.com/watch?v=NnMIhxWRGNw

Case 11 - https://en.wikipedia.org/wiki/Quantum_entanglementCase 10 - http://bigthink.com/dr-kakus-universe/what-travels-faster-than-the-speed-of-lightCase 8 - https://en.wikipedia.org/wiki/NeutrinoCase 7- https://en.wikipedia.org/wiki/Tachyon Case 5,6 - https://www.youtube.com/watch?v=EPsG8td7C5kCase 1- https://www.youtube.com/watch?v=lR4tJr7sMPM