Speed of light Definition and 1000 Threads

I'm not sure if this is the right area of the forums. If it's not. Tell me which area would be better and I'll post this there. Time Travel- Would have to be space travel... and possibly faster than light If the time traveled and the time it takes to travel took less time to travel...

hello there , now excuse me to those to whom this looks like the questions you have hard a thousand times before. Now I understand how we calculate the speed of light in vacuum and no doubt we can do that under laboratory conditions etc. Light bending in gravitational fields is also...

Is there a branch of physics that exist over the speed of light? like a superphysics or hyperphysics?

Homework Statement I was wondering if anyone knew of an equation or table that I could compare my labs measured speed of light to? I'm aware that the index of refraction is 1.000293 at 1 atm and 0°c but was hoping to find a way to check our values specifically. We ended up with 1.0002343 so...

How can one say that speed of light is constant.Is there any possibilities of speeds greater the c.If Yes/no then why?

The speed of light in a vacuum is the universal constant c. The speed of light in a medium is something less than c; let's call it s. Has the positive difference (c-s) been observed as light travels through ordinary matter in space such as gaseous nebula or plasma nebula? If no, is it...

Can someone please explain me why speed of light is measured same regardless of their speed? Will not a person moving with 0.6c measure speed of light as 0.4c?

Hi Guys , Just read this at The NASA site: http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/070904a.html ""Q ...My question is if the universe is accelerating, eventually should it not reach a speed faster than the speed of light? Has anyone investigated the question as to what will...

Hello Want to know if constant speed of light is a result cause by time dilation? When your time slow down as you approach speed of light you take a longer time to measure light speed in your spaceship, there for you think speed of light relative to your current speed is still c? When one...

Hello! I think I understand the principle of Special Relativity, that because the speed of light has to be constant to all observers, the only solution to the problem is that time slows down or speeds up for different observers who are traveling at different speeds. But my question is: Why...

is it possible that gravity reduce the speed of light, and addtionally does anyone know an equation to calculate the exact deflection of light due to gravity.

If time passes so much slower near the speed of light... What would happen if somone on Earth made a 10 minute phone call to somone traveling at the speed of light? In this case, the 10 minutes would be relative to a watch from the person on Earth and a watch from the person moving near light...

The position and momentum of a photon is uncertain. If that is the case, then shouldn't the speed of light be slight uncertain?

First off, I'm not a physicist (as I'm sure is evident by my multi-part question), but I'm hoping someone will be kind enough to explain this in basic terms. Part the first: I'm wondering if someone can explain to me in layman's terms why the speed of light is essentially the universal speed...

After reading a few threads about the speed of light and the expansion of the universe, I noted one a message which mentioned that even though light may be headed our way it can appear to be going away from us, if the universe were expanding faster than the speed of light. How does that make...

An observer is moving at 10% the speed of light. A light ray whizzes past him. He measures its speed to be exactly 186000 miles/sec. What happens at the physical level that he does not measure the speed of light to be less? Has the time of the observer slowed down? Or what?

You are driving down the road at almost the speed of light. And you fire a powerful laser that is attached to the front of your car. The laser beam hits a guy standing at the side of the road and goes through his hand. But to the guy at the road, your laser beam can't hit him, because to...

If you are the only object in the universe, what speed are you going? Well there would be no such thing as speed because your speed is only relative to other objects. So if there is no such thing as speed, how is there a speed limit? Let me give an example. If you take off from Earth...

I've been hunting around online but have found only long-winded explanations of the speed of light in non-intertial or accelerated reference frames, which mostly relate to gravity. I'm looking for just a straightforword treatment dealing more specifically with traveling acceleration and not...

An object moving at the speed of light will be mass-less or will it have infinite mass??

A spaceship moves near the speed of light. Its time becomes slow for an observer on earth. 1. Does 'time' slow only in and around ( i.e. the space inside and outside) the spaceship? If yes, to what extent ( i.e. how much meters or centimeters) above the physical boundary of spaceship. 2...

Hi, We know that light changes speed when going from a medium 1 to medium 2 (obviously, they are characterized by different driffactive indexes). Light wavelength doesn't change (same color) during such event. If medium 1 is less dense than mendium2, the speed of light in medium 1 is...

Hello all . We know when matter like electron reach near speed of light its mass increase and Limits to Infinity . Why we can not reach electron to c ? Because for changing speed at near speed of light : 1 - We need infinite momentum ? 2 - We need infinite energy ? 3 - We need...

I have been reading up on time dilation a bit this morning, and for the first time, I think it really clicked. Its raised some questions that I haven't seen answered anywhere, so I was hoping someone here could help. As I understand it, and please correct me if I am wrong, the only thing that...

If two stars, each moving away from each other faster than the speed of light, how would the light behave? Let me add more detail, if you have two stars a light-year away from each other and "off" and then accelerated both of them in opposite directions traveling at say .60c and identically...

Hey everyone just a quick question, I'm trying to understand E=mc2 and I keep getting conflicting information that we ARE moving at the speed of light and some saying that we are not all moving at c. Can anyone clear this up? Thanks!

Scenario: Alice is "sitting" on photon A Bob is "sitting" on photon B both are moving in same direction, their paths are parallel to each other. Per relativity the speed of light is constant So Alice will measure Bob's speed to be c and Bob will measure Alice's speed to be c yet they are...

I was wondering if anyone knows of such a website or program whereby I can type a speed I would like to travel, and it will allow me to travel around the Earth or through the universe at that speed? Nothing like a flight simulator but just something that will allow me to control the speed the...

In the spinning cylinder room example mentioned in relativity, where the nearest distance between 2 point is actually curved line.. and light take a straight pass right, which is farer than the curved line due to time dilation in the middle of the room due to a smaller acceleration than side of...

... can someone explain to me why the following thought experiment does not give the object a speed greater than 3*10^8 m/s. Imagine that the experiment takes place in a very large vacuum. A very long toy train is moving at 100 m/s on a track from rocket propusion. On the top of this train...

Faster than speed of light?? Throughout my schooling ( middle school and beyond, to be precise) I've learned and believed that nothing travels faster than speed of light... But my university textbook of physics says that matter waves can travel faster than speed of light... Isn't this kind of a...

Lets say ship 1 is traveling just under the speed of light so time slows down for the crew and the age less quickly than the stationary crew in ship 2. Relative to the crew in ship 1, the crew of ship 2 are traveling at just under the speed of light, so time moves slower for them and they should...

Dear Forum Users, I am a graduate student in Mathematics and not physics, so please bare with me. Also, I know that a similar topic has been discussed before but i could not get a clear answer from reading the previous posts. And here is the question i have been wondering about...

Hello Some authors claim that Einstein's second postulate (constant speed of light) simply emerges from the first one (or more precisely, its converse contradicts the first postulate). Serway Modern Physics: Now, is that true? And if yes, what's so special about light than other object (ex...

Homework Statement Find the Einstein luminosity (LE) in terms of just c and G (the speed of light and the gravitational constant), i.e. determine a power (in watts) from just these two terms using dimensional analysis. What is this value? Once determined, you should be able to show that an...

I was thinking about refraction and phase velocity change, when i thought about whether the c in e=hc/lambda is always 3x10^8 or does it refer to the speed in the medium? Thanks

Ok, i know this makes me look like a crackpot, but suppose for an instant there is an aether or absolute space or whatever! Let me be on a rod that travels tranversely with respect to aether and let me be exactly on the middle point of this rod. I have a GPS device with me and send it upwards...

Hello 1 km long train traveling on a straight track at a constant speed V of 90 percent of the speed of light. At some point in the ground near the track there is a flashlight, when the last wagon passes the flashlight, a beam is sent to the engine. on the engine there is a facility that...

Speed of light "boundary" ? I have a simple question : When everyone is talking about the "speed of light boundary" what is it relative to ? Speed is ALWAYS relative to "something" else, otherwise it doesn't even make any sense. Which brings a second point : if there is indeed a speed...

It is usually written that the speed of light in a dielectric medium is ##v=\frac{c}{\sqrt{\epsilon_r}}##, where ##c## is the speed of light in vacuum and ##\epsilon_r## is the relative permittivity. But, how can it be calculated for lossy and not necessarily low-loss dielectrics, i.e. those...

This isn't for any homework or coursework. I am new to physics and have decided to embrace my inner geek that i have been suppressing for 30 years. Some light reading recently has pointed out to me that the speed of light is not a constant velocity we should hope to achieve but the speed at...

I thought about an idea that keeps spinning my head around. It's proven that the faster you move the slower the time passes for you and let's assume that speed of light is the limit. So if you had a spaceship that can travel at let's say 99.9% of speed of light wouldn't that be the same thing as...

can we in theory travel faster than light?

Suppose a beam of light is approaching you from a distant source. As it comes closer to you, it doesn’t hit you; instead it misses you by a 10 meter distance. How can the rate of acceleration of that beam relative to you, be explained(in non-jargon language)? What would the speed of that be...

If airplanes' highest speed depends directly on the air it is moving through and not the ground, does it mean we can build a time machine if only the air moves near the speed of light?

If when you're moving at the speed of light time freezes, why then does it take light 8 minutes to reach the Earth from the sun?

If Galaxy A drifts apart from Galaxy B with twice the speed of light then how could a Galaxy C next to Galaxy A drift apart from Galaxy A at a similar speed? edit: PS. Wouldn't that need some kind of "universal central observer" to limit Galaxy A from Galaxy C to not drift apart by more than 2*c?

I've seen other posts about this, but would appreciate an explanation if anyone knows. I've read that traveling faster than the speed of light could affect causality. Example: item I traveling in a tube could be seen arriving at end B before it ever left end A. A=======I=B Is this an...

I know the textbooks say light travels 186,282.4 mps, but if time slows for a very fast object, how do scientists really know the speed of a photon?

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...