Speed of light Definition and 1000 Threads

If the speed of light is ~300 m/s in a vacuum, can the electric and magnetic fields of the wave be condensed such that it travels faster? The idea being that an outside force condenses these fields and lenghtens the wavelenght with no loss of energy thus increasing the directional speed. The...

Why the speed of light is constant for every observer ? Is it a special thing for photons cause I guess there's no other elementry particle that can move with c ? Also I want to investigate the constant of c for every observer, in the perspective of particle relationship. For example, can I...

Can anyone help me with a very basic question please. Is it really not possible for anything to travel faster than the speed of light, as dictated by relativity theory ? I am a complete beginner to Physics and only have very basic mathematics knowledge and I'm trying to understand the basics of...

I have been thinking about the Higgs field and how things interacts with it. I thought about why photons for example does not interact with it while quarks does. It could be because of the size and if when a particle is a certain size it will interact with the Higgs bosons and then slow down and...

I may have a fundamental misunderstanding of the concept, but I was wondering, how does the accelerating expansion of the universe calculate for the time dilation in light travel? From my understanding, we know that the universe expansion is accelerating because the farthest galaxies that we...

I was wondering if it is possible to use only a stopwatch and a telescope to find the mass of a planet, such as Saturn. I've experimented with a couple of things but I keep running into problems. I previously asked this question in the homework section, but it does not involve numbers, is not...

Homework Statement Using only a telescope and a stopwatch, find the mass of Saturn.[/B] (This question may or may not make any sense at all, it was a theoretical lab that my professor said without giving us a chance to copy it down and I am trying to recall the question from memory) If it is...

is anyone looking for what might be the effect of something going into or coming out of the speed of light?

What will happen if something traveling faster than light is found?What effect will it have on modern physics?

GW170817 showed that gamma rays came 2 seconds after gravitational waves. (after 130M years) Are these two seconds uncertainty at determination of difference of these speeds? Or is it possible to explain, why 2 seconds of difference, or is it possible to explain, at least, a part of this...

Suppose at the instant a gravitational wave passes through an interferometer, one of the interferometer's arm get stretched by 1%. Would the wavelength of the photon traveling in the arm also get stretched by 1%? If so, then would the frequency of the photon remain the same and hence increasing...

Help with the question of the concept of the stability of the speed of light. I gather that current atomic clocks are based upon the speed of the electron around their nucleus, which is a function of the speed of light. Measurements of the speed of light that depend upon atomic clocks therefore...

1. We have a moving platform traveling 700 miles per hour to the Right-Direction. 2. In the middle of the platform, we have a gun which fires a laser both at the front and back of the platform at the same time. 3. We have at both the front and back of the platform, a mechanical device. These...

If you search for "does a photon experience time", almost every other link says that they travel at the speed of light and so STR tells us that its clock doesn't tick at all. However why do they use the arguments for special relativity which was developed for massive particles moving close to...

In an elevator "vertically" accelerated at g in outer space, the equivalence principle says a "horizontal" light ray in the elevator looks like a parabola. I completely understand that the light ray is curved but don't understand why the deflected light ray is an exactly parabola. Almost all...

Hi, I am seeking to understand better how this well accepted idea: "...according to general relativity, gravity is a manifestation of the geometry of spacetime." (https://en.wikipedia.org/wiki/Loop_quantum_gravity) is compatible with the equally well accepted idea that gravity travels at the...

Why does an increased electrical permittivity reduce the phase velocity of light in a medium? Furthermore, what interactions do we see on an atomic level? I am aware of the equation that defines the speed of light in terms of the electrical permittivity and magnetic permeability, but I do not...

Why does an increased electrical permittivity reduce the phase velocity of light in a medium? Furthermore, what interactions do we see on an atomic level? I am aware of the equation that defines the speed of light in terms of the electrical permittivity and magnetic permeability, but I do not...

I just wanted to share this idea with other people who may be interested: I watched a PBS Space Time episode about the speed of light more accurately described as the speed of causality. And I Submit! That "time" is simply a interaction between atoms. And though an interaction can be...

I have as advised done some catching up on basic cosmology, looking at various discussion and lectures on the nature of the universe. Something that has always played on my mind, is that i remember reading and watching a documentary about the potential to achieve the velocity of light. It was...

Hello all, disclaimer here, I haven't taken quantum mechanics yet, all I know of it comes form books and PBS Space Time Series. Since a photon can, at any given instant, "split" into an Electron-Positron pair, does it mean that if this occurs between point a and b, the measured speed o that...

As I understand it, the ratio of the electric field strength to the magnetic field strength at any point in a propagating electromagnetic plane wave is equal to the speed of light. How can the electric and magnetic field be perpendicular to each other yet still validate the E = cB equation? A...

A thought experiment about the speed of light. Say I build a 600,000 km long tube around the circumference of the Earth at the Equator. The tube's inner diameter is constant at 54.4505 mm. A snooker ball is perfectly manufactured to its lowest tolerance by a special new machine. Each one is...

When I read the speed of light in vacuum is c, does it imply that light doesn't actually travel at this speed in nature? My guess is no, light always travels at c, it's just that in the definition, we're trying to ignore the affects on light from other stuff like the comological constant and the...

Wouldn't the first thought be that we would be burned to a crisp if we where hit with all the light(in our path) across the span of the entire universe simultaneously? It seems there could be paradoxes even before the advent of relativity. Or maybe it was shown mathematically that the energy...

Sorry if the title was a little vague, character limits. The question at hand is this; If you were to accelerate an object to near speed of light, time around it would speed up, thus forward time travel. We all know this and I am no expert in this area but am incredibly curious. (Assuming we can...

This may be a dumb question, but some of these other thread got me wondering: is there a concept of local/proper time for electromagnetic waves? I imagine the only 'clock' that could measure time (ticks) at the speed of light would be the field oscillations.

It is said that due to the expansion of the universe, there are some distant galaxies that are moving away from us faster than the speed of light. They can't actually move faster than speed of light itself, because the law of physics over there are supposed to be the same as the law of physics...

The speed of light is postulated to be constant in all inertial frames. but why is it called a postulate actually? looking at the SI definition of the meter that is specifically defined by the propagation of light i notice it makes it constant by definition. so isn't this actually just a choice...

I was watching a seminar on black holes and one of the participants threw out as an aside that spacetime could travel faster than the speed of light - so within spacetime nothing could travel faster than spacetime but spacetime itself however was not bound by this rule so it could move faster...

First, I am new to physics and only taking my first course in calculus based classical mechanics with topics covering thermodynamics and an introduction to general and special relativity. Everything here is pretty much a question, even if periods exist and not question marks. My teacher had...

This may be a rather ridiculous inquiry, but Google queries haven't helped much. As I understand it, different colors (wavelengths) of light move at the same speed in a vacuum, which together make up what is often called "white light." However, when light enters the Earth's atmosphere, its...

[Moderator's note: this was originally the second part of a post in another thread; it has been moved to this separate thread.] PLEASE BE ADVISED: I'm a complete ignorant with regards to the details of what I'm about to say and I've never looked at the mathematics of the subject, let alone...

Hi, Physics Forum! I've been wondering what would happen in the following thought experiment. I am not physicist and may have made some incorrect assumptions. Please explain if any of these assumptions are wrong. What would happen if you threw a piece of (very long and strong) rope into a...

I am aware that an observer in free fall in a gravitational well will measure the local speed of light as c, but what about someone outside the well. Imagine this, Me and my friend are near Earth, and he starts freefalling to the surface, while i stay in space. If he then fires a laser beam at...

Just recently I came up with a new idea to measure one way speed of light and/or synchronize distant clocks: Let’s have two light sources at points A and B separated by distance d and sending constantly (perpendicular to AB) signals to clocks at A’ and B’ Let’s have an opaque rod of the length...

Okay...The speed of light is affected by density of the medium in which it propagates...It is more in rarer medium and lesser in denser medium...Hence we can conclude that a medium affects the speed of light...My question is that why this ''affect'' is not ''continuous'', like why the speed of...

Why does light move at the speed it does, why not half the speed or double?

Why speed of light is independent of frame of reference,why is it constant everywhere, speed of an object is different from different FOR then why this is not follwed by light, In deep space there is nothing to measure the speed of light relatively, then how it got its speed(299 792 458 m/s)...

It's generally understood that nothing can be accelerated up to the speed of light, and that nothing can surpass it. That being said, the expansion of space itself can exceed this "universal speed limit," as the Universe is expanding so fast that light can't catch up to it. Regarding the...

I had read in the Time-Life Science Library book "Man And Space" about the possibility of a very, very ambitious mission in which an astronaut would go to a galaxy 200 million light-years away, with the spacecraft simply being accelerated at 1 g during the whole time (in the direction of the...

Hello! My question is: If you travel in a material at the same speed as the speed of light (I assumed this is possible due to the existence of Cherenkov radiation) you will see the light basically stationary so you see a constant electric field which means no magnetic field. But light has both...

The speed of light is constant, in what ever direction, that's not disputed. Now in relativity that as I understand light speed constant C is bound up with time, eg faster you go faster time pass for an outside observer but stays the same in your field of reference. Or to put it another way the...

Special relativity states that the speed of light is constant for all the references, as long as they are not accelerating. For example, the speed of light would be c for a train moving linearly with a constant speed and would also be c for an observer who's not moving at all (I took the Earth...

Could einstein's theory be completely wrong if we discovered that the speed of light is different in an another galaxy ( speed light isn't constant) and if we proven that there is particles or objects which moves faster than light by 100 or 1000 times?

Hi, Simple question. if a ship is getting close to the speed of light its momentum (mass) will continue to increase requiring more energy to propel faster. The fuel in the ship will also gain energy and mass as it accelerates. at C it will require infinite energy because it will have infinite...

I have seen at many places that if ever matter travels more faster than light, it's relativistic mass will reach nearly infinity. Some says it's the inertia, so very high energy is required to accelerate. But since it is traveling with the velocity above 3×10^8 m/s, i believe that the high...

Hello, I was enjoying Zee's book on GR when I noticed the location of this "a(t)" thing in the metric sound quite disturbing to me. BTW: I experience the same annoyance and went down to the same conclusions, when I watched a related Theoretical Minimum lesson...Here's the setup, the flat...

This seems over optimistic to me but is 20% the speed of light feasible? https://www.sciencedaily.com/releases/2017/02/170201162456.htm

This is just kind of an odd question that has to do more with concept than practice but if you were going 1m/s slower than the speed of light and were holding a laser pointer would the laser only point one meter ahead of you? I know that light doesn't add like normal vectors but this is...