No, Hold it, Who says the light in the pixels on my monitor screen are not moving. Then how does it get to my eye - if it isn't moving. The light source is turning on and off. It isn't moving across my screen but it is moving.

Flicking your wrist doesn't speed up the light. The distance from me to the moon doesn't change as he flicks his wrist. The distance is the same therefor it doesn't move 20x the speed of light.

The light that hits one edge of the moon isn't the same light that hits the opposite edge of the moon, so it doesn't move 20x faster as you project it from here to there. In fact, The light will be moving the exact same speed from me to it's destination despite where it is aimed on the moons surface.

Well, for the pixels thing, he specifically says "pixels", not "light emitting from pixels". The pixels themselves never move. The light the pixels emit (if any) does move, of course, to get from the pixel to your eye. But that's a separate issue.

He's also not saying that flicking your wrist speeds up light. The premise of this video isn't that light can travel faster than what we know as "the speed of light", just that "something" can travel faster - in this case, the image of a laser. The speed at which the image is traveling across the surface of the moon would indeed be faster than the speed of light. Which is fine, because as he points out, images don't have mass.

This is more about the ontology of motion than the speed of light, though the 2 are closely related.

Soooo....you still can't break the speed of light? Ok...

I hear what you are saying but I think his premise is unsound.
I can point a laser due north (into the stars) and then switch to point due south (into the stars.)
That doesn't mean anything can cross the universe (known or unknown) in a split second (except maybe Q)


I often thought about this as a kid. If I point a flashlight into the stars, will some entity, out there in space see my bean of light? I concluded that no they couldn't. Besides the fact that the light would get filtered out by space particles long before it reached anywhere, The light moves too slow. I can point my flashlight now and hold it there for one minute. Then that beam would have to travel for more years (Hundreds? - Thousands)? than even I could imagine until it hit something.

Did the light beam continue to travel through space after the minute I shut off the light or does it keep traveling? A blip of light traveling through space. If the light we see from stars could be light from stars that burned out years ago, then I suppose (if it was ever strong enough not to be filtered out) that blip would be possible.

So the fact that I can point and shoot a continuous blip of light in one direction in space, and then wave it around to another section of space, doesn't mean that blip is moving from one planet to the next (or even one galaxy to the next.)

This idea most likely asks more questions than it answers and I'm sure we could talk forever but I just think light defies the basic standards of measure we tend to use on it.

>> ^Bhruic:

Well, for the pixels thing, he specifically says "pixels", not "light emitting from pixels". The pixels themselves never move. The light the pixels emit (if any) does move, of course, to get from the pixel to your eye. But that's a separate issue.
He's also not saying that flicking your wrist speeds up light. The premise of this video isn't that light can travel faster than what we know as "the speed of light", just that "something" can travel faster - in this case, the image of a laser. The speed at which the image is traveling across the surface of the moon would indeed be faster than the speed of light. Which is fine, because as he points out, images don't have mass.

Well, your example doesn't work. The point here is that an IMAGE is moving. If you shine a flashlight into the sky and move it around, the chances of the flashlight image appearing anywhere is almost nil. So there's nothing really to move. Shining a laser on the moon, however, will make an image appear (assuming all other factors being correct, such as lack of clouds, etc). So that image will, in fact, "move" across the surface of the moon. It's no different, really, than shining a flashlight at a wall, and moving it around. The image moves, despite the fact you're doing nothing more than adjusting the tilt of the flashlight.

You're right that a standard flashlight wouldn't be visible from space, let alone another star system. However, if you had a powerful enough beam (or used wavelengths better "suited" for space travel), there are quite a few other stars that are much closer than 100 lightyears. Promixa Centauri, for example, the closest star to our system is only 4.2 lightyears away. So were you to put a sufficiently strong source accurately in that direction, you could even receive a response in your lifetime, were there something (or someone!) there to respond.

I am not geeky enough to see any errors in your explanation, just geeky enough to enjoy it.

You can also do this with a stream of pee

Frame dragging. The speed of light doesn't increase within the spacetime being dragged, but it would appear to increase to an observer outside the frame.

I guess the key point is that animations are illusions. They look like something is happening, which isn't. When you watch a Wile E. Coyote cartoon, he's not really disproving the theory of gravity. It has nothing to do with physics, and everything to do with perception.

Light doesn't have one set speed. Each frequency of light travels at slightly different speeds. I've long had this theory, and NASA has since confirmed it. We have detected very slight differences in the time it takes different frequencies of light to travel a set distance.

As such, we cannot say light has "a" speed, but rather a range of speeds. Therefore, could it also then be possible that the speed of an individual photon can be adjusted by various means in order to either speed up or slow down?

The answer is yes. Scientists have managed to slow the "speed of light" all the way down to 38mph. How is this possible? Well, as light has mass (albeit, a very miniscule amount), it will slow when traveling through a material, such as water, glass, oil, or even air. Passing the light through a super-dense, ultra-cooled material magnifies this effect.

As we already know different frequencies of light travel at slightly different speeds, and as we also already know, we can only visibly perceive a very narrow range of frequencies (for example, we cannot see infra-red or ultra-violet, or x- or gamma-rays), isn't it then perceivable that there are frequencies of light outside of what we can see that do travel faster than "the speed of light"?

And if this is true, then what else could travel faster? Are there things we can't even hope to detect simply because they exist in our timeframe for an impossibly short amount of time?

Part of the reason light is able to travel as fast as it does is its incredibly small (by our standards anyway) mass. What if mass is infinite? What if you could shrink yourself down to the size of a photon, or better yet, small enough to live on that photon as if it were the Earth. From your new perspective, the photon would appear to be very large, and as you are now traveling with it, that photon does not seem to be going as fast. You may see things that are even smaller and appear to move even more quickly, but something like the Earth would be imperceptible to you because you are so miniscule. It would be as the Universe to you--impossibly large, and inconceivably tangible. While you would know it is there, it would stand before you as a gigantic, unknowable concept, and things even larger than that would exist merely as mists of an imaginary daydream.

Now, imagine that the electromagnetic spectrum is infinite in both directions as well. Consider the possibility that, along with light, x-rays, gamma radiation, radio waves, and all the other things we know to make up the electromagnetic spectrum, sound is also part of that spectrum. Consider that light, being high in frequency exists near the top of what we can perceive of the spectrum, and sound is near the bottom. The vibrations become so slow and so wide toward the bottom that they effect the air and other matter around us, creating sound. And while we cannot see it, we perceive it with other sensory organs. Imagine that you could slow down light to the point that you can hear it, or speed up sound to the point that you can see it.

Now take another hit before that feeling goes away.

This is not accurate. As far as we know, light (a photon) is massless and its speed does not change based on frequency (color). However, its speed does APPEAR to change with frequency because of its interaction with matter (we call this refraction). Similarly, its apparent speed will change depending on the type of matter it is traveling through.

However, the photon is not actually slowing down. Rather, it interacts with other particles, bounces around, then emerges some time later. It does all of this at the speed of light, but the particle appeared to slow down because it was "busy" interacting with whatever medium it was traveling through.

Actually, what's really interesting, and more accurate, is that the photon that "comes out the other side" is not the same photon that went in. The original photon no longer exists, because it was absorbed by the material, at which point a number of interactions happened, and another photon was emitted. There are countless numbers of these interactions occurring when light travels through matter, and countless numbers of photons being created and annihilated before the photon that we actually observe comes into being.

>> ^ForgedReality:

Light doesn't have one set speed. Each frequency of light travels at slightly different speeds. I've long had this theory, and NASA has since confirmed it. We have detected very slight differences in the time it takes different frequencies of light to travel a set distance.
As such, we cannot say light has "a" speed, but rather a range of speeds. Therefore, could it also then be possible that the speed of an individual photon can be adjusted by various means in order to either speed up or slow down?
The answer is yes. Scientists have managed to slow the "speed of light" all the way down to 38mph. How is this possible? Well, as light has mass (albeit, a very miniscule amount), it will slow when traveling through a material, such as water, glass, oil, or even air. Passing the light through a super-dense, ultra-cooled material magnifies this effect.

There is so much wrong with this crap. I can't even begin to explain.

@ForgedReality. I am not going to go knee deep into this. But I think you have misunderstood a few things. First, dispersion or the index of refraction of many materials is frequency dependent. Ironically, my graduate research focused extensively on this! In it's simplest form, the dispersion relation is (w/k)^2 = (c/n)^2. That means that the group velocity is limited by c. So in a medium where the refractive index is nonzero the speed of light is less than c. Frequency dependence further complicates the issue. It implies that the refractive index is different at different frequencies. Hence, light at one frequency has a different group velocity than light at another frequency. This has been known since Hertz. It was explained by Einstein.

Lene Hau's experiments at the Rowland Institute are a little more difficult to explain.

It is a little easier to explain something related to her experiments: Bose-Einstein condensates. Naively, you can think about light as billard balls. If you hit one ball moving at a given velocity in a given direction with an identical ball moving in exactly the opposite direction and same velocity, then by momentum transfer you can cancel the motion of both balls. When you do this with light you create a Bose-Einstein condensate.

This is equally misguided, but it is closer to the correct interpretation.

>> ^offsetSammy:

This is not accurate. As far as we know, light (a photon) is massless and its speed does not change based on frequency (color).....
>> ^ForgedReality:
Light doesn't have one set speed. Each frequency of light travels at slightly different speeds.

Where did I go wrong? I'll be very happy for you to set me straight. I'm no physicist!

I do understand that talking about the motion of a single photon, as if it moved linearly through space, is not accurate and not how photons behave, but I don't think I'm particularly qualified to talk about the rules of quantum electrodynamics and was just trying to correct ForgedReality's interpretation as best I could.

>> ^MycroftHomlz:

This is equally misguided, but it is closer to the correct interpretation.
>> ^offsetSammy:
This is not accurate. As far as we know, light (a photon) is massless and its speed does not change based on frequency (color).....
>> ^ForgedReality:
Light doesn't have one set speed. Each frequency of light travels at slightly different speeds.

On a side note: There is significant push by Nader Engheta and other to explore materials with refractive index near zero.

This stuff is pretty interesting: http://en.wikipedia.org/wiki/Metamaterial

Downvoted for being intentionally misleading. This isn't "Breaking the speed of light" by any reasonable definition. The video half admits that by the end, but still starts out by claiming to "Break the speed of light". I hate crap like this.

I'm going to give this one more shot in as layman's terms as I can.

-Moving the direction of a beam of light does not speed the light up.
-The distance the beam travels in each direction is the same.
-The distance and/or speed of the light can only be measured from point A (The laser pointer) and point B (The moon in question).
-There is no measurement from Point B1 (the left side of the moon) to Point B2 (the right side of the moon). No matter how fast you shake the pointer around.
-The light that hits B1 is not the same *Blip of light that hits B2.
-You are NOT pushing the light around, you are projecting a separate wave of light to each new co-ordinate as you move it around.

An example: Imagine you tie a piece of thread from point A to point B1, then imagine you flick the beam to B2. You will now have a new thread from A to B2 and not from A to B1 to B2.

@Sagemind @rychan... Did we scare them off with Science?

*promote... interesting discussions...

Promoting this video back to the front page; last published Friday, March 30th, 2012 10:25am PDT - promote requested by MycroftHomlz.

>> ^rychan:

Downvoted for being intentionally misleading. This isn't "Breaking the speed of light" by any reasonable definition. The video half admits that by the end, but still starts out by claiming to "Break the speed of light". I hate crap like this.


But it does beg the question, "what is it that's moving?" What is an image? Is it just data? Is it a series of points being illuminated in sequence?

In the pixel model, there is a distinct on/off state for each pixel. What about the dot from the laser. It's continuous. Or is it? This thing raises a lot of very deep questions. I don't think it's "intentionally" misleading at all. Just difficult and provocative. That makes it good.