Does light travel in curve lines in free space? I read in https://www.sciencemag.org/news/2012/04/light-bends-itself that some scientists have found a method to make light travels in curve without any external influence using Airy Function. I'm relay curious to know how this is possible?  
 A: It is just a property of the Airy function that its peak intensity follows a curve. However, one should also pay attention to the rest of the function. The function as a whole does not violate momentum conservation. If one would calculate how the centroid of the whole function moves, one would find that it actually moves along a straight line.  
A: 
Does light travel in curve lines in free space?

Thanks, a very interesting question. Answer is YES (in some circumstances). For example, if we put photon straight into black hole's event horizon, then such photon will start to orbit black hole in circles. Thus if you would be put into black hole event horizon too - you could even see your own occiput. Strange effect indeed, thanks to black holes.
A: As the article says, the effect is really an illusion.  There's nothing special about the Airy function.  Imagine that you transmitted a laser pointer beam through a lens, thereby focusing the beam to a small spot.  Now move the lens in a circle, and the spot will move in a circle.   
Now let's get rid of the lens and just move the laser pointer in a circle so the beam traces out a cylinder. Move it VERY fast, and what you'll observe is a coil: the light moves at a constant speed and takes a while to get to any given distance, so if the light were going through smoke it might appear something like a barber pole zooming along its own axis.  Shining on a piece of paper, the light would resemble an arc of a circle, rotating around the circle's center.
What's described in the article is implemented in a different way, but otherwise is essentially the same as what I've described above.
