Speed of light Definition and 1000 Threads

quick question when a light source is moving at a good clip like the above where the light bulb is moving at half the speed of light am I wrong in the drawing that the light halo would be lagging towards the back but even on the two sides? what I'm wondering is how long would the light behind...

Hi guys. I know that light does not travel through time. Is that because its speed is constant for all observer?

Would the speed of light be effected by the mass of light. Is the speed of light relative to mass? In other words if you fuse photons will they be capable of reaching beyond C?

Hi, We know that gravity affects time and the presence of big masses such as planets will cause big distortions in spacetime which slows things down (if I'm floating in space, won't I be distorting spacetime for.. say.. an ant? Won't the ant gravitate towards me?). Anyway. we know that...

If we suppose that you could travel at near light speed through space, then would there be a problem with bumping into things? Could you avoid "stuff" in space, such as asteroids, planets, etc. (down to microscopic stuff like particles floating around)?

Since light bend in gravitational fields in line with the general relativity , does the speed of light slows down? or is it always constant and never change?

Sorry if this was asked but I couldn't find a answer! I heard that when you travel at near the speed of light (0.999...c, wrt the Earth or Sun maybe?) the universe would be seen blueshifted (even the CMB would be visible) and length contracted in front of you. However I also heard that we are...

Just to clarify: I only have very rudimentary knowledge of Physics, so please correct me if I am wrong. This thought came to my mind after I discovered some youtube videos and articles on the double slit experiment: AFAIK, if the information of which path the electron takes is obtained, there...

Suppose we launch two ships and move them close to the Sun. They have solar collectors and can absorb a massive amount of energy thanks to their proximity to the Sun. The ships are connected by a 1000 meter long rod of titanium, and each ship's rocket is position opposite the other's, so that...

Is it true that if time stood still it would violate the uncertainty principle. therefor if you traveled at the speed of light time stands still and you would violate the uncertainty principle. if this is true does that sugest that QFT sets a lower max speed that matter can travel at than what...

Here is a video of traveling faster than the speed of light by Veritasium : Could someone explain in detail about the spinning satellite idea and the reason why the carbon nanotube rods have to broadened as it gets nearer and nearer to the satellite ?

I have been doing a lot of reading about this and it seems really, really interesting. Correct me if I am wrong on any of this, but I'm going to attempt to summarize how traveling at the speed of light, or at least 99.998 percent the speed of light, would look in two different cases: in...

The question "If light speed is constant, how do you explain the Doppler Effect?" has been asked a lot in the internet. Anyway, I haven't found one concise answer. In the book Kleppner&Kolenkow Mechanics there is a brief explanation of the Relativistic Doppler Effect, but as usual in this topic...

I have been reading some sites that claim that the speed of light was greater in the past. They do not say whether it was locally different or over the entire universe. My view is that either way, we could detect it. Locally would be an anomalous region of the universe looking very different to...

If an object is in a vacuum and it is constantly increasing its velocity, since it would need to use energy to do so it would create a waste. Since it is the largest mass in the vacuum would the waste created be pulled towards the mass causing it never to reach the speed of light?

My basic understanding is that no matter how you observe light, it always a constant, it always travels at the speed of light. So even traveling at near the speed of light you will always measure light traveling at the speed of light. If this is the case? Why do we observe red shift?

The question that ponders upon the thought if the speed of light really is constant is a fairly common question. However, I was wondering about something and MAYBE this can provide some backup to the theory that the speed of light isn't constant, please point out any mistakes I make in stating...

I'v been troubled by something. Einstein's second postulate determines the speed of light in empty space to be a constant c, measured by all observers to be the same. So I was thinking, it is possible to slow light by making it pass through a dense medium like water or glass. If we imagine such...

SR section 1.7. Einstein states if a train and light beam are moving in the same direction, the speed of the light as seen from the train is c-v. ( c being the speed of light and v the speed of the train ). c-v being smaller than c is resolved by time dilation or length contraction. My...

OK, knowing enough astrophysics to get myself hurt, I'd like to pose the following poser that whupped me upside the head while watching the Black Hole marathon last night on the Science Channel. We have; 1) The Big Bang theory, 2) An expanding - at least, for the moment - universe, and 3)...

My apologies for the numerous times this has probably been posted, but I wasn't able to find a great answer through the search tool alone. Please correct me on anything I state incorrectly, and direct me to the answer.. My question is, if the speed of light is 299,792,458 m/s, its speed is...

I think my understanding of STR might be wrong. I was watching a documentary where they said that if you're traveling at the speed of light then time stops. Now let's say I'm traveling through intergalatic space from the Milky Way to the Andromeda at 99.9% the speed of light. I also have my...

I apologise in advance for my rather minimal knowledge of physics. Please assume that anything I write below is just my current understanding, and may very well be incorrect... Elementary particles decay into other elementary particles. When a a subatomic particle decays into a pair of other...

I recently watched a documentary presented by Professor Brian Cox called Human Universe. In it he was wondering how much leeway he would have, if he was "the creator of our universe", to alter the physical constants. He then went on to say that if he altered the speed of light one way then...

If I travel at the speed of light and have a mirror can i see my reflection? Thanks Any ideas?

I was thinking about the special theory of relativity and how as one approaches the speed of light, ones length contracts. what I would like to know is: If I had an object and I accelerated it towards the speed of light and it contracts in the direction of travel, what happens when it reaches...

Homework Statement In terms of the energy involved (using formulas provided), explain why accelerating a spacecraft to the speed of light is impossible. Homework Equations time, mass and length dilation formulas, and a few astrophysics formulas, E = Ek + mc2, projectile motion formulas The...

Is it possible to derive the speed of light from quantum electrodynamics (like it can be done from Maxwell's equations) or is the fact that the speed of light in vacuum is constant and has a certain value an assumption in the theory? My understanding is that QED assign a mass zero to photons and...

I read somewhere that at 90% the speed of light the mass doubles. So does mass only nearly double at the speed of light and does mass not become infinite at the speed of light? I thought nothing with mass can travel at the speed of light because mass would become infinite at light speed. Also...

My friend posed a question to me that I was unable to succinctly answer (or answer at all for that matter). So I thought I'd make an account and ask people who know more about this than I do. Ok. So let's assume that Person A starts at Position 1. Person B is at position 2, which is 1 light...

Homework Statement A 5.9cm-thick layer of oil (n=1.46) is sandwiched between a 1.3cm -thick sheet of glass and a 2.4cm-thick sheet of polystyrene plastic (n=1.59) How long (in ns) does it take light incident perpendicular to the glass to pass through this 9.6cm -thick sandwich...

Homework Statement The Apollo 11 astronauts set up a panel of efficient corner–cube retroreflectors on the Moon's surface (see figure below). The speed of light can be found by measuring the time interval required for a laser beam to travel from the Earth, reflect from the panel, and return...

Magnetic field moving faster than speed of light? We know the equations for speed of rotating magnetic field, as N= 120*f/P, where f is frequency of AC currents & P is number of magnetic poles. Say by some method we are able to produce a very high frequency AC voltage & apply that to a stator...

If two galaxies are separated by a large distance such that radiation transmitted from the mid-point between the two galaxies never reaches either galaxy due to the expansion of space, how can the expansion of space at the mid-point ever affect the distance between the two galaxies. i.e. how...

As per Maxwell's equations the speed of light is c = 1/√(permeability X permittivity) I find that both permeability and permittivity have pi in their calculations. Since spacetime is not flat, the value of pi would change due to the curvature of space near large masses. Does this mean...

Pretty straight-forward, I'm just curious. My current level and understanding of physics has lead me to believe that as an object accelerates it's mass becomes higher and if it were to be able to reach the speed of light it would get infinite mass. I believe this currently, however, two of my...

We know that gravity speeds up a body, like a meteor which enters the Earth gets constantly speeded up by Earth's gravity. And from relativity we know that light bends near a massive body because Newton's law of gravitation is just an approximation and actually gravity depends on energy and...

I'm reading Pauling's General Chemistry and he starts off his first chapter with, "Matter may be defined as any kind of mass-energy that moves with velocities less that the velocity of light, and radiant energy as any kind of mass-energy that moves with the velocity of light." I know that we...

Hi, I'm new to this, so I'm hope this is how this works. But I had a question. I've heard that even theoretically, it is impossible to go faster than the speed of light. Because, even if you provided enough energy to move something faster than the speed of light, i.e using either a lever or a...

Hello, Lately I have been wondering about the implications of the speed of light being constant for all observers, to me this seems to imply that there are different versions of reality for different observers. I will use a scenario to illustrate my reasoning. After you read this I would like...

A quick question I hope: What would I see from Earth if I sent a rocket to Saturn at nearly the speed of light? If the rocket travels a million miles at a thousand miles an hour I will see it arrive in 1000 hours. If the rocket travels at nearing the speed of light I won't see it arrive for...

Is there any reason to think that that the speed of light could vary with time (taking t=0 at Big Bang), ie, could light have been slower or faster billions of years ago? Also, is there any experimental evidence so far that either confirms or denies this? Do we know of any experiment that proves...

Hi, I've read that the speed of light is consistent for all observers, no matter where they are. So, for instance, a photon on a train is going at the same speed whether you are on the train or off the train. If it was a football, instead of a photon, it would be different speeds right (the...

If a spacecraft moving near the speed of light has a camera set up inside observing the people in the spacecraft , and the camera is connected to a computer on Earth so that observers on Earth could watch the video that the camera sends, what would the people on Earth see? Would they see...

"breaking" the speed of light limit. I couldn't quite figure out how to describe it shortly hence the weird title. I was wondering what it would "look" like if the following situation happened. Lets say you have a space craft. It is going at a speed of 0.7 c. in relation to star X...

Hello I have doubt about this idea.Why things can't go speed of light.I heard that we have to give unlimited energy to make a thing goes speed of light.If you expain it to use math I will be glad Thanks for your help

Got the following from a friend who teaches HS physics... Measuring the speed of light with chocolate and a microwave oven http://morningcoffeephysics.com/measuring-the-speed-of-light-with-chocolate-and-a-microwave-oven/

I never understand why the speed of light is the same for all observers irrespective of their motion relative to the source of light. Now suppose I am sitting at the back of a vehicle which is traveling at the speed of 0.999999999999c and light approaches me from behind the vehicle. i.e. I am...

I know about the Michaelson-Morley expt. trying to measure the speed of light, once in the direction of motion of the Earth and then perpendicular to it. But the source of light was a torch (or similar) which is (obviously) on earth. I have somewhere read that it was also done with the source...

Hi guys, I am reading griffiths electrodynamics. I have a question. How does Maxwell equation suggest that the speed of light is same for all observer? I know Maxwell's equation gives a value of C. How can we infer that it is same for all observer. Special relativity just assumes that the...