Speed of light Definition and 1000 Threads

How is the speed of light, and path of travel, effected in time-space distorted (by say, gravity)? We know that the sun/earth's gravity distorts time-space. So when a photon travels from sun to earth...as it nears the earth... how much length would the photon travel? Would it be slightly...

I'm not sure if this post belongs with general physics or relativity, so feel free to move it. I am trying to get a better grasp of special relativity and I think the following scenario will help. Say rocket X moves at -0.51c and rocket Y moves at +0.51c and they take off from point Z. When...

In my physics class, we learned that light moves slower when traveling in different materials like water or air. However, it is the fastest in a vacuum. I was wondering why this happens. I read something about a refraction index in the different materials. For example, water has a refraction...

The rotation speed of planets around the sun follows a simple rule: if you double the distance to the sun the rotation speed is reduced by the square root of 2. No matter the mass of the planet. If Earth mass was different the period of rotation around the sun will be exactly the same. But in...

i don't know in which section it belongs, so i am putting it here... according to various theories proposed by various researchers, time travel depends on the speed of light. as far as i have read/heard - i) anything traveling faster than the speed of light moves back in time. ii) anything...

Abstract In this experiment, a beam of light from a laser was reflected off of a rotating mirror to a fixed mirror, and then reflected back to the rotating mirror. The returning light was focused to a point image in a microscope. Due to the continued rotation of the mirror while the light...

The speed of light is measured to 299 792 458 m / s and 1 meter defined to 1/299 792 458 of the speed of light. Let us assume that A live at the top of a skyscraper and B in the cellar the past 10 billion years. After 10 billion years B’s clock have “lost” 10 second due to different...

Hello! if a car(A) is moving with a speed 2m/s and another car(B) is moving in opposite direction with speed 3m/s. then velocity of car(A) with respect to (B) is 5 or -5m/s . so my question is why the same principle does not follow with speed of light as according to theory of relativity speed...

Because time slows down at the speed of light does then light itself potentially travel at almost infinity per zero seconds? (trying to leave aside relativity and gravity issues for a moment, so just theoretically?) Is that then the real reason why nothing can go faster than light - ie...

Just a random question regarding the speed of light. I am not a physics major or a college student, just curious. I was watching a program on the science channel (I think) and it was talking about how the speed of light is absolute. The example it gave was traveling in a car at a high rate...

The relativistic mass formula is m=γm, and at the speed of light, relativistic mass is infinity. But, the Lorentz factor at the speed of light is 1/0, but this is undefined, so why do physicists call this "infinity"?

Is the speed of light "really" just a conversion constant, like 2.54 cm/inch? Rather than arguing about the usual, (which we have a spate of at the moment), I'd like to see if this is a fair summary of how physics and physicists view the speed of light - as a units conversion constant. I...

I feel a little like the kid that, when his dad tells him that he has to water the plants, asks 'why daddy'...to which dad replies 'because the plants need water to live'...to which the kid asks 'why daddy'...and it goes on and on. Why? Why? Why? Here is my confusion and my question. If...

You know that in accelerators like LHC,particles are accelerated to speeds very near to that of light I want to know what phenomenons are observed in such high speeds,because lorentz transformations don't seem very clear there Thanks

Some time ago,I read among the news,that two physicists have extended SR to velocities greater than c in a way which is compatible with the original theory and still in their theory,v=c plays the role of a singularity I searched on internet but couldn't find any paper explaining the theory and...

Using a simplified (radial co-ord only, spatially flat) FRW metric with the usual co-ordinates of cosmological time t and co-moving radial distance r: ds^2 = -c^2 dt^2 + a(t) dr^2 we find the path a lightbeam takes by setting ds=0 to obtain \frac{dr}{dt} = \frac{c}{a(t)} Therefore if a...

I'm doing some research trying to find behavior of particles at speeds faster than light. I'm wondering if anyone knows if there are any papers on this, as I can't seem to find any except for papers on superluminal movement rather than what happens when particles actually travel faster than the...

I get why it is impossible to accelerate faster that the speed of light, because at the speed of light and object has infinite mass and so need infinite force to accelerate it. But, I don't get why you can't accelerate to the speed of light. So what I'm saying is I get why you can't accelerate...

. http://en.wikipedia.org/wiki/Black_hole and we know that when object travels near the speed of light it gains infinite mass, so does it means that it becomes a black hole?

Not really sure if this is the right location for this post, but here it goes. I have found myself becoming increasingly interested in light and wondering if the speed of light could be increased by some amount. If the light was charged, and released near a powerful electric field, could the...

Hi, there is something I can't understand: Consider a stationary observer at A. Now consider an observer B in a train that moves with constant velocity v with respect to A. In the train, B tries to measure the speed of light using an empty tube of length L0 (proper length as measured by B). He...

I wad thinking since black holes are so dense ... lights speed would get slow significantly , so isn't it that if you are at light speed ( 3 x 10^8 m/s ) then you might come out of a black hole ? Its the same concept we learn in 10 grade ! Am i right ?

This is quoted from "The Elegant Universe" "the velovity of light is a kind of cosmic speed limit, a speed that nothing in the universe can exceed." - The Elegant Universe, On Einsteins Discovery My Question is, How did einstein test/know this? How could he have possibly known what the...

Hi, The theory of special relativity is based on assumption that the speed of light in vacuum does not depend on the source or observer. I have two questions regarding this. 1) Which is constant, speed or velocity? Is the direction also constant? 2) Are there experimental verifications...

Not sure if this was posted but this seems like an interesting paper. Then again, I'm not well read in this topic to judge their arguments: Einstein's special relativity beyond the speed of light http://rspa.royalsocietypublishing.org/content/early/2012/09/25/rspa.2012.0340 Physicists...

Hi, I was reading "Why does E=mc2 and why should we care". This is a statement from the book: "There is a good reason why light travels at the speed it does" Could someone help explain this? I am sure light doesn't travel with the speed c≈3×108 m/s because it needs to satisfy a physical...

Hi, Firstly, I want to thank all those knowledgeable people here that offer their input so freely. I have found it very enlightening and educational. I apologise in advance if the following is quite long but there are a couple of cosmic rules that I can't quite grasp so I will try to articulate...

Why do we move (including the dimension of time) at the speed of light? I understand that when our velocity increases in a spatial dimension, it will decrease in time, but why is the initial, overall velocity c?

Am a bit confused about the speed of light being constant, does this mean that whatever speed I am going at, up to and including the speed of light, I will always measure it as going 300000000 mts/sec faster than myself?

Please feel free to move this to the correct forum. After doing some reading, I've found that Electromagnetic radiation travels at the speed of light in a vacuum. EMR also travels in the path of a wave. Whereas, light and/or light photons travel in the path of a straight line. Having said...

Let's say I had an object in space, a ring in this particular case, who was using light energy to spin itself up. The ring was built with a reactor inside of it along with a passenger/observer (we'll call the inside observer Bob for now). Bob, the ring, and the reactor are pretty much...

Homework Statement Light travels through water at a speed of about 2.25e8 m/s. Is it possible for a particle to travel through water at a speed v greater than 2.25e8. Homework Equations E=(Rest Energy)/sqrt(1-v^2/c^2) The Attempt at a Solution I realize that light requires no...

From answers given to me here and elsewhere, I finally got a (what I think should be the right) answer to the problem: Suppose that the universe were expanding in such a way that two planets were receding from each other at a constant speed of 1.1c (or, in other words, their distance would...

Hello, We know we can not see light.It is only the effect of light that we actually see . Is it because of the fact that our eyes can't move at a speed of light? or its just basically the nature of light that we can never see it..? If I move my eyeballs at 'c', would I be able to see...

I thought I read that if you were in a ship near the speed of light, all the stars would appear to be in front of you. The closer to c you are, the more everything will be collapsed to a cone facing forward. Is that right? Thinking about it a little from the non-moving frame, it seems like...

Ok. I admit I'm completely new to Relativity (I had my first lecture today!). What I learned was that the speed of light is a absolute constant that doesn't change. I then came into some situation like, 1. I'm driving my car with velocity v and turn on my headlights, won't the speed of light...

One of the main postulates of relativity is that the speed of light is always constant. However, light does not always travel at c, it only travels at that speed in a vacuum (supposedly). When it is in a medium such as water or air, it moves at a noticably slower rate, where even other objects...

The speed of light in a vacuum is constant because it participates in no inertial reference frame. If I am moving at 300m per second and shoot a beam of light ahead of me that beam travels at 300,000m per second irrespective of my speed or my motion. If I increase my speed, time slows down...

I have been curious about this but cannot find any real resources that answer it succinctly: Our current understanding of the universe is that nothing can travel faster then the speed of light. so far science in general has been unable to prove otherwise. However: As far as we know the age of...

I'm currently reading Sakurai's 'Modern Quantum Mechanics' (Revised Edition) and at page 76 he introduces a spin half hamiltonian H = - (\frac{e}{mc}) \vec S \cdot \vec B. But what is c doing in this hamiltonian? Clasically the energy of a magnetic moment in a magnetic field is E = -...

So everyone knows the speed of light is a universal constant. However in many phenomena involving light it is useful to think that light is 'slowing down' like light travels slower in glass/ water then it does in a vacuum. How can this be if it is a universal constant?

Time passes faster further from the center of gravity of a large mass (like the Earth). For example, if a spaceship travels faster than the speed of light from Earth to another planet and after 1 year returns to Earth. From Earth to the other planet takes 3 months and return 3 months. Would...

Here's how I understand the situation: when an electrical current is running through a wire, the individual electrons are moving very slowly. The reason that a light bulb turns on so quickly after the switch is closed, then, is because as the electrons near the switch start moving, they push on...

In school yesterday my teacher told me that we could not travel at the speed of light because the faster we go the more our mass increases and that we would reach infinite mass before we reached the speed of light so there could never be enough energy to propel us that fast. I asked my...

I was reading about the speed of light and it says that no object can travel at the speed of light because the mass of the object increases as it moves faster. How is that possible? Also if light travels at such a speed because it has no mass, then why does light get affected by gravity near...

this is from Omnes' book Understanding QM Has this problem been resolved or is it still outstanding?

I know that the speed of light in a vacuum is always measured to be the same regardless of the observer's frame of reference. My question is, does the same apply to the speed of light as it travels through any non-vacuum medium? My gut feeling tells me yes, since its speed through the medium...

Hi all ! Firstly, I am a computer science student, and I have very very very little idea about what I am talking about. That's why I am here. I don't understand what Higg's boson is, but after the recent confirmation, I watched a huge number of videos on the internet to get an intuitive...

Hi all, I'm a basic novice at physics so please be gentle :) As I understand it, C (from E = MC2) is the constant representing the maximum speed of information transmission in the theory of relativity. The Speed of Light in a vacuum is atributed to C under the theory that, as light has no...

I know that lorentz transformations are the same in matter and vacuum My question is,when light is propagating in matter,it certainly has a speed smaller than c Does this mean that we should treat it differently from light in vacuum? I mean in a vacuum,we say that time doesn't pass for light...