Can light go faster than the speed of light? I was thinking if a light particle/wave went past or near a planet/sun/black hole could the light be slingshot by its gravity and go faster than it currently is or is light too fast for this to happen?

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> Can light go faster than the speed of light? I was thinking if a light
> particle/wave went past or near a planet/sun/black hole could the light be
> slingshot by its gravity and go faster than it currently is or is light too
> fast for this to happen?
>
>
The speed of light remains (C)onstant.

That just came back to my mind, somewhat fascinating - having heard it in the news or read in a science paper, can't remember -
As recently discovered und sucessfully experimented in Austria, it seems to be possible to exchange information at infinite speed just in short words by creating a pair of corresponding electrons (I think they were, or photons) out of one by a complex mirror system or so. These two are connected on quantum level (for ever?) - whatever quantum state (spin) one particle is in, the other will be the same - instantly and at any distance. The problem is just that you'd have to move the pair apart over distances (no information-transmission is of any use if the origin is the destination) an that you'd be able to actually monitor the state of the particles or actively change it.
So there's the possibility someday maybe to actually "beam" information...

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Maybe we haven't figured out the physics of it yet - but to me, it's obvious that yes....light is not the upper limit.

To me, it's very simple - and you may, or may not agree. The Event Horizon of a black hole is such that light cannot escape - true? So, anything that would escape it would have to be beyond the speed of light. Simple. However...now..picture the gravity INSIDE the event horizon - and remember that it works BOTH ways. IF..at the event horizon...you have to accelerate to the speed of light - then, inside it - the gravitational pull is BEYOND the speed of light (unless you think it just...ummmm...stops...as you get closer to the singularity...?) It works both ways. At the event horizon - it's the speed of light - but...between the singularity and the event horizon.....?????? Does gravity STOP?????????

You tell me....

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Draconian, you're confusing the concepts of force, acceleration, and velocity. In particular, forces (such as gravity) don't have a speed associated with them.

Think about launching a rocket from Earth. If it doesn't end up going fast enough, it will just fall back to the ground. The velocity it must achieve is called the "escape velocity". What happens with a black hole is quite simply that the speed an object must achieve so that it doesn't fall back down would be greater than the speed of light. In fact, were it possible for particles to travel faster than the speed of light, black holes could not exist.

HACKMAN, while it's true that it's possible to have so called "entangled states" where a measurement of one particle also determines the state of the other, transmitting information would require the ability to choose what state one of the particles ends up in after the measurement. This is forbidden by the same physics that allows such states to exist. Entangled states only exist because two particle states with identical particles must satisfy what is known as "exchange symmetry", which demands that no observable quantities change if you switch the two particles. Being able to choose what state one of the particles will be in when you measure it violates this same symmetry.

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While gravity itself doesnt have a "speed" it's effect does. And that is the speed of light. For EX if our Sun just disappeared the Earth wouldnt feel the gravitational effects for 8 minutes and some change.
http://www.google.com/search?hl=en&lr=&q=What+is+the+speed+of+gravity%3F&btnG=Search

Solomon, I don't have much time although I'd really like to discuss this (which would require me to aquire more background information on quantum entanglement). The only thing I googled and found out as it confirms what I read: A scientist group around prof. A. Zeilinger in Vienna has managed to "beam" quantum states 500m across the Donau last year, despite all physical problems like Heisenberg uncertainty and so on. There was a major hype in the news about that where people tended to exaggerate the possibilities thus upsetting Mr. Zeilinger *g*. However it seems to be possible, next step is an exchange experiment at larger distances between two towers in Vienna.

Most of the stuff is in german unfortunately:
http://www.quantum.univie.ac.at/research/

and maybe some interesting publications, which I don't have the time to read now:
http://www.quantum.univie.ac.at/publications/thesis/

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> Solomon, I don't have much time although I'd really like to discuss this
> (which would require me to aquire more background information on quantum
> entanglement). The only thing I googled and found out as it confirms what I
> read: A scientist group around prof. A. Zeilinger in Vienna has managed to
> "beam" quantum states 500m across the Donau last year, despite all physical
> problems like Heisenberg uncertainty and so on. There was a major hype in the
> news about that where people tended to exaggerate the possibilities thus
> upsetting Mr. Zeilinger *g*. However it seems to be possible, next step is an
> exchange experiment at larger distances between two towers in Vienna.
>
> Most of the stuff is in german unfortunately:
> http://www.quantum.univie.ac.at/research/
>
> and maybe some interesting publications, which I don't have the time to read
> now:
> http://www.quantum.univie.ac.at/publications/thesis/
>

Theres also a branch of quantum research going towards how it could be used in computers as well.

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> Theres also a branch of quantum research going towards how it could be used in
> computers as well.
>

I have heard stuff about that hurts my head a bit thought :) ( http://computer.howstuffworks.com/quantum-computer.htm )

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Well leaving all science out of it, i have some memory of an experiment that found that with the right manipulations the speed of light can be slowed. From that I can say that the speed of light is NOT constant. Therefore it is possible that light could theoretically be accelerated to speeds faster than what we consider to be the Speed of Light.

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Kolch - Crunching for the BOINC@Australia team since July 2004.
Search for your own intelligence...

As I understand it, the speed of light isn't a constant... For example the speed of light in water is lower than in air which is just a bit lower than vacuum (hence refraction occurs as light passes bands of different densities). Furthermore, I read somwhere, that (lightweight) black holes "evaporete" slowly, what gives me impression, that there are "thingys" moving faster than light.
But I might be completely wrong. (It's up to the "brainiacs" to figure it out)

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Good point: It all depends on what one understands under 'speed of light'.
Most people think about the physical constant c, which is by definition a constant. But, the speed of light depends on the medium through which it is travelling. The speed of light will amount to th constant c (which is by definition the speed of light in vacuum) when traveling through vacuum, where the refraction index is 1.
If you have a medium with a higher refraction index (for example water) speed will be reduced by a factor depending on that index. In approximation it will be c/n (but there are some higher factors of the refraction index coming into play which usually are negligible).

I clearly remember the experiments done to slow down the speed of light to a few m/s, as I was at that time doing my PhD on a related subject in atomic physics (laser-cooling of atoms for Bose-Einstein condensation). The principle of those experiments was based on modifying the refractive index so that light would be slowed down. Note that they achieved slow speed, with almost no light loss, by using higher order effects of the refractive index in a Bose-Einstein condensate as optical medium.
Some articles: http://www.spie.org/web/oer/may/may99/cover2.html
http://www.hesston.edu/academic/faculty/nelsonk/PhysicsResearch/boseeinstein/nkrr.htm

However, until today, c is the highest possible speed at which light may be travelling. Which doesn't necessarily imply that nothing could travel faster...

I also remember having seen a presentation of Prof. Zeilinger a few years ago. In fact, his quantum entanglement experiment confirms earlier experiments of Alain Aspect showing the violation of Bell's inequalities and thereby confirm the predictions of quantum mechanics. It should prove that there is no communication between two particles slower or at light speed in entangled quantum states. It does however not prove that there is a communication between both perticles... but does prove that quantum physics (Heisenberg's uncertainty principle...) is correctly describing the reality.
The article of Zeilinger is at: http://xxx.lanl.gov/PS_cache/quant-ph/pdf/9810/9810080.pdf (watch out, heavy stuff...)

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Black hole evaporation involves a phenomenon known as "virtual particles". One of the predictions of quantum mechanics is that, on very short time scales, pairs of particles with opposite properties (such as an electron and a positron) can appear and annihilate each other. Hawking demonstrated that if this occurs just at the event horizon of a black hole, one particle will end up inside the black hole, and its partner may escape. The net result of this, as required by conservation of energy, is that the mass of the black hole decreases by the mass of the particle that is not trapped. So, this situation does not actually involve anything moving faster than light.

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Found this...

Shows that scientists have succesfully observed light travelling at speeds faster than the Speed of Light. No date or links to reference material but it closes the arguement for me.

EDIT</B>
Oh, and for those wondering 300 times the Speed of Light is roughly 90,000,000 kilometres per second.
[b]/EDIT

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Kolch - Crunching for the BOINC@Australia team since July 2004.
Search for your own intelligence...

I guess light goes faster than the speed of light...

I have a pretty simple example for this depending on Relativity. It is known that the speed of light is 299792458 m/s.And roughly just round it up to 300 000 000 m/s.

Now imagine that in the future we have built 2 spacecrafts ( imagine them as big as the death star in star-wars .. planet sized things ) that can travel at 200 000 000 m/s.

Now, to set up the scene we need 3 people.. one of them at a stationary planet,
the other two are at the spacrafts.

1st person: moving one way at 200 000 000 m/s (V1 = 200000000 m/s )
2nd person: moving the opposite way ( toward 1st person ) at 200 000 000 m/s
(V2=200000000 m/s )
3rd person: observing the 2 craft from a stable location. ( V3= 0 m/s )

Now we all know that two objects moving towards eachother, observe eachother ( or perhaps crash at eachoter ) at a speed of the total of both objects :)

So visualize these guys looking at eachother from their windows or detectors or something..

1st person sees 2 nd person moving toward him at a speed of V1+V2=400000000m/s
2nd person sees 1 st person moving toward him at a speed of V2+V1=400000000m/s
3rd person sees both people moving toward eachoter at 200000000m/s

according to the formula e=mc², where if the speed is at the speed of light
( c ) the mass comes to a singularity and all becomes energy..

the 1st and 2nd guys would see eachother as pure energy ( as they travel at plus 100000000m/s the speed of light ), but the 3rd person sees them as rather more normal objects..

Or just think that you are travelling at 200 000 000 m/s and you turn on your flashlight.. the speed of light from the flashlight would be 200 000 000 m/s + 300 000 000 m/s .. weird... Or perhaps manage to throw a ball real fast while travelling at that speed.. the ball would be travelling faster than light and would be totally energy to someone looking outside your craft but you don't..

Sorry for a long long long post but.. i think this would pretty simply tell that things could travel faster than light.. real faster..

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>
> 1st person sees 2 nd person moving toward him at a speed of V1+V2=400000000m/s
>
> 2nd person sees 1 st person moving toward him at a speed of
> V2+V1=400000000m/s
> 3rd person sees both people moving toward eachoter at 200000000m/s
>

1st and 2nd people have just enough time to think "oh sh!t..."
3rd person just stands there and thinks "what the f*$k was that?"

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Kolch - Crunching for the BOINC@Australia team since July 2004.
Search for your own intelligence...

Just had to add one more thing.. After all speed is all relative.. =) it is how objects move from one place to another at a certain amount of time.. And how do we measure speed ? we measure it according to our position ( or the position of the device we are measuring it with ).. Things would have speed according to us ( or one another ). We are the REFERENCE point to it's calculation.. we stay they move, they have speed.. they move we move they have speed.. two things moving together seem to have no speed but they have speed to another observer.. speed can only be, where two or more things move ACCORDING to eachother and have a reference so they can be measured,calclulated,felt,seen whatever...

thanks..

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Yes, and there's where Einstein's relativity theory comes into play...
(have a look at: http://science.howstuffworks.com/relativity2.htm)

So you can't just add two speeds together and get a speed twice as high. But, according to Einstein's relativity theory, the maximum speed limit you'll see is... the speed of light.
PS: Nobody has experimentally proven the contrary yet.

I must admit to kolch that I am aware of experiments that showed some speeds faster than c, these were wave group speeds and not the wvave speed itself.
Nice experiment to try at home :-)
http://www.newscientist.com/article.ns?id=dn2796

And I found that one relating to the 'faster speed of light' you've mentioned. Seems to be in OK with Einstein's laws..
http://www.msnbc.com/news/435007.asp?cp1=1

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Reading too much into the NEC experiment...The light appeared at the exit of the chamber before it entered it. Which creates in itself a time travel paradox. What if they somehow closed the entrance before it fully entered? Would some of the light that had appeared at the exit just disappear as if it were never there? Or would the light just never appear there because somehow it knew that its path would be blocked and it would never make it to the otherside?

Another point...If light waves are pure energy and pure energy has no mass, what force do black holes generate that holds all light in? As I understand it gravity has no effect on objects without mass.

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Kolch - Crunching for the BOINC@Australia team since July 2004.
Search for your own intelligence...

>1st person sees 2 nd person moving toward him at a speed of V1+V2=400000000m/s
>2nd person sees 1 st person moving toward him at a speed of V2+V1=400000000m/s
>3rd person sees both people moving toward eachoter at 200000000m/s

1. 1st person see the 2nd person moving toward him at
v=(v1+v2)/(1+((v1*v2)/c²)=276923076 m/s. You forgot the Lorentz transformation: Galilean tranformation doesn't work for relativistic speed.
Same thing for 2nd person seeing the 1st.
2. You're right for the 3rd person because his speed is 0m/s in his own referential.
Well, perhaps my little computation is wrong but 400000000 m/s is impossible because when you try to go at the speed of light, your mass is growing (E=mc²).
If you travel at the speed of light, your mass is infinite and your proper time is infinite too. Not a very funny situation...:o)

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Arnaud