Light speed Definition and 322 Threads

I'm really confused! How can time be relative and speed of light absolute? If you were moving a long with speed, whilst someone else was stationary would you not measure light to be slower??

I posted this under general physics but i feel its better suited in this section. Ok, looking at it from the point of view of the photon due to time dilation the time at which its emitted to when it finally strikes an object is instantaneous, regardless of distance, from its own frame of...

Ok, looking at it from the point of view of the photon due to time dilation the time at which its emitted to when it finally strikes an object is instantaneous, regardless of distance, from its own frame of reference because its traveling at the speed of light. The twin paradox tells us that if...

Clocks run slower, deeper they are in the gravity field, or faster they are receding from observer. Question: If we could measure speed of light near the event horizon, or at far away galaxy, by means of measuring from distance, would we measure light going slower there? I am not asking...

If someone were traveling at let's say 99.9999% the speed of light time would go slower for them but their speed would stay the same. So let's say for every ten second we would experience here on Earth they would experience they experience 1 second. so they would travel (10 seconds X...

Light appears to travel at a constant velocity in a constant medium/matrix. According to Einstein, gravity is the opposing force of displaced space/time matrix by mass. The more mass, the more the gravitational displacement. Light is "bent" around massive objects. Shapiro? says there...

If a spaceship were to fly at 1/10 the speed of light and project a laser onto a distant moon, would the light cast from the ship reach the moon at 1.1 times the speed of light, relative to a stationary mounted laser fired at the same time/distance?

just a fun couple of questions that seem interesting. but redicoulous. say you could, and i know you can't, but say you could make an object travel faster than the speed of light. what would happen when you hit the light barrier? and if the object was traveling at 2x light speed,and it...

Let’s say we have a spaceship capable of traveling at the speed of light, and a planet we can visit 50 light years away. From earth’s perspective if we can track the ship we would be able to see it was traveling at the speed of light and we would also see it has taken 50 years to complete the...

a. Is it known if there are actually regions of space which would be far enough and expanding at a rate enough that light will never be able to reach us? Or, is it possible to say that a boundary may exist in a way that, beyond it we can be sure that light will certainly not reach us? b. Also...

I hope I can explain my question clearly enough for someone to answer. Suppose we wish to estimate the power required to accelerate a spacecraft from say 0.9c to 0.9999c in a certain time. By basic definition: Power = Change in Energy / Change in Time. Due to special relativity, there is...

From "The conceptualization of time and the constancy of the speed of light", Vasco Guerra and and Rodrigo de Abreu. I just came across this article which proves that the speed of light had to be constant by just assuming "good" clocks record time correctly irrespective of orientations...

When some people try to explain current flow in a circuit, their explanation troubles me. They say that electrons 'push against each other' and this is responsible for the close to speed of light propagation even when the electrons themselves are moving very slow. My view is that though...

We'll know that the base of special relativity theory is "the light has a constant speed in vacuum". Time dilation and Lorentz contraction are consequences of the constance of light speed. If we excite photons, for example, its frequence increases (and the wavelength could decrease), but...

I am curious as to how a photon traveling at 'c' is described by an observer also traveling at 'c'. Elementary education tells us that photons, always travel at the same average speed in the same medium, regardless of the motion of the observer. However, if both were traveling at 'c', from...

I heard that an infinite amount of time would pass as an object decelerates from the speed of light, is that true?

Not sure if this will have anything to do with quantum mechanics.. but... Ok so if you're traveling faster than light speed, then what do you see? I'm not talking about the whole doctor who scenario, its like traveling faster than sound, if the jet pilot is traveling faster than the sound it...

OK, I've been wondering, what's the significance of saying "speed of light in a vaccum" if lightspeed is a constant. Is the "vacuum" part even necessary?

If gravity slows light, would light be pushed faster away from a star that has less gravitational pull? Would we still observe it at c?

If two planets were traveling at .99c away from a planet in the center. What would be the speed difference between them? If you were on one of those traveling planets and launched a rocket in the direction you were already travelling, you could get it to go .99c away from you. If you...

Hi there folks, Physics isn't my speciality, I'm in medical studies, so i don't really understand a few things. One thing i don't understand is how the velocity of light remains the same independant of the observer's frame of reference, but everything else is relative. What is it about...

What evidence is there that at light speed things such as time dilation, and mass/energy, actually reach infinity?

if we ever had the technology to do this would it be possible for humans to travel at the speed of light?

Why would time stop if you travel at the speed of light?

So the other day while I was folding up some laundry I had this idea pop into my head. Now I'm not an expert or anything and I dropped out of physics in high school, but I do think quantum physics are interesting like most people. I figure this would probably be the best place to post this due...

I feel kinda silly asking this question. If you were traveling near the speed of light towards another ship and you shone one of those simple red lasers towards that ship would that ship blow up?

So I'm having a problem actually visualizing what close to light speed travel would look like, both from the viewpoint of an observer on Earth and from the viewpoint of an on-board traveller. It doesn't seem that any of the visualizations in the movies fit my understanding of it, so maybe I've...

If Mork decided he wanted to go home to his planet Ork (10 light years away) and traveled at 99.1% of the speed of light, while Mindy stayed in Colorado, who would have aged more, Mork or Mindy, in the following situations. a. If Mork went to Ork and returned to Colorado. Who would...

if we were able to move at the speed of light (somehow) how would things change due to the relativistic effects. Take this for example: if we were to go somewhere moving at 100 percent of c,and for simplicity say that it's 100 light years away, what would we feel or think? i know if we were...

I was talking with a guy at work about relativity. I have VERY limited knowledge in the area of physics ( one college level class on radiation physics, and read a few books and essays on my own) but he has absolutely none. He watched a show on Nova or Discovery that blew his mind about light...

So let me first off say i probably have no idea what I am talking about. I am simply a junior in high school whos only knowledge of physics is that of what i try to research on my own time. I really do like it though. But it is my understanding that light speed is a consistent rate and no...

Yesterday I saw an online news saying that scientists spotted a huge gamma-ray blast 12.2 bln light-years from earth...if this is true then the blast should have happened 12.2 billion years ago when the whole universe were still in quite an early stage according to the modern cosmolgy...then I...

By which I mean; if we see a galaxy at a distance of 1 billion light years, then we see that galaxy as, and where, it was 1 billion years ago. This is something that I presume no-one would disagree with. If there should be a galaxy situated at the same distance from us, but in the opposite...

if it is possible to travel faster than the speed of light will we be seeing the future or the past?

First off, for my first post I would like to say Hello to all! Secondly, I am definitely a rookie in the subject that I'm discussing and if any of what I mention has been answered or has an explanation, please follow up on that with me! Again, I'm just a rookie and I am seeking more seasoned...

If you could move at the speed of light what would happen? Could you survive?

Information In the book “Black Holes and Time Warps” by Kip Thorne it is mentioned on pg 121 that Einstein didn’t believe that black holes existed so the thinking that black holes can exist didn’t come directly from his writing, thoughts, or how he interpreted his relativity theories. Because...

[b]1. The problem statement, all variables and given/known Is it true that nothing can travel faster than the speed of light? Can't all electromagnetic waves travel at light speed. Also, if the speed of light is a constant, is the speed of the other electromagnetic waves a constant such as x...

Hello, I'm newbie to physics and relativity and I wish to know more. I've had a question for 5 years and nobody has been able to give me a clear answer. Here it goes! Suppose there were 2 astronauts in space one in front of the other. There is a distance of one light year between them...

My teacher lectured on time dilation today and I'm confused about some things he said. How does light maintain the 2.99X108 m/s? And for that matter, what propels it to move that fast in the first place? Finally, why, as the c is approached, does the mass of an object get infinitely large...

Hi there, I have a question for you pros on this site. If an observer were to reach the speed of light, would time dilate to a stop? Now I have another question about the nature of matter and light. I've made this observation: Matter has 3 physical dimensions (length, width, height)...

My question is whether the speed of light, as defined below, is precisely the same as the speed of light in free space, without gravity. DISCUSSION I'm trying to figure out if the standard value for "c" is or is not corrected for the very,very slight influence of Earth's gravitational...

Homework Statement "Anthony and Dobson are twins. Dobson travels in a straight line away from Earth for 7 years according to his time at 0.96 times the speed of light. After 7 years he turns back and travels back to Earth at half the speed. Meanwhile, Anthony was waiting stationary on Earth...

Two observers, A & B, are moving apart at constant velocity V. At distance D, B sends a pulse to A which arrives T seconds later. If B were instead accelerating at a rate such that he attains velocity V just when he is at distance D, and sends a pulse at this instant (while still accelerating...

Lets say that some object (object 1) is traveling at 60% of light speed. An identical object (object 2) is also traveling at 60% of light speed towards object 1. That would imply that the space between the two objects is closing up at a speed faster than the speed of light...but is this vision...

would the speed of light be attainable in a place where light doesn't exist?

Can anyone tell me if the speed of light in a vacuum was the same a few seconds after the big bang when the universe was small as it is today? In other words could it be that the speed of light changes as the universe expands? Also is it actually known why light travels at the speed it...

Take this scenario for instance. Now from the position of the Earth if you were to lookup into the night sky the distance between stars can seem like mere inches, but in actuality it could be 100’s of light years between the two. Now, for this scenario you are a person standing on the Earth...

I apologize for the the probably gross error on my behalf, but, not as a scientist in the GR /SR field, I am a bit confused. My question is why is c constant? I am not arguing why is c constant in a specific frame, I do not understand why you couldn't, for a lack of a better term, frame stack...

Electricity (the flow of current) is said to travel at near the speed of light (75-90%), but I read that electrons have a drift velocity of only 2-3 mm/hr or something close to that. So, if the electrons are so slow, should I think it is the holes that travel fast? Suggestions.