I wish people would call me out more often, how am I supposed to learn otherwise?

Thanks for the comments, Matt!

Unfortunately for scientists, the only time journalists report on science discoveries is when it has an attractive (no punch intented) catch phrase to go with it. If you saw the reporting, they do put the words attractive and repulsive in quotation marks. After reading the article that it refers to, I found out that it’s actually very basic physics (in a relative sense), and (thank god), there is currently only 4 fundamental forces in the known universe.

What that article refers to is a mechanical attractive and repulsive force between two waveguides (which are like fiber optics cables, but way smaller) due to induced dipoles in the waveguides created by the light. Let me quote a section of that article :

“Considering two proximate dielectric single-mode waveguides separated by gap g as depicted in Fig. 1a, propagating lightwaves in each waveguide interact through the excitation of dipole oscillations. The optically excited dipoles in one waveguide interact with the evanescent field of the other waveguide and generate a force that is dependent on the separation of the waveguides and the relative phase of the optical modes. When the modes are in phase (psi = 0), the optical force is always attractive; when the modes are out of phase (psi = Pi), the resulting force is repulsive when the separation is larger than a critical value gc , as shown in Fig. 1b.”

So what happens is, when the light is in phase, at every point on both waveguides (which are dielectrics), the electric field of the light creates electric dipoles (i.e. a magnet is a magnetic dipole, it has a “north” and “south” pole). If the light is in phase, the dipoles in both waveguides will be pointing in the same direction, and like magnets, this will cause a mechanical attraction ( because the “south pole” of one waveguide will be closest to the “north pole” of the other. If the light is out of phase, the “south (or north) pole” of one waveguide will be closest to the “south (or north) pole” of the other, and they will repel (as is the case in magnets). There are other little subtleties (as with the Cassimir effect), but that’s the basics of it. One photon cannot (as far as I and most of the scientific community knows) be attracted or repulsed by another photon in empty space (what exactly is a photon in a material is still debated).

Anywhom, thoses were my two cents.

As a scientist though, I feel the need to pop a few bubbles in a few things concerning this blog though.

I believe saying that light can fall is a misrepresentation of what is the physical reality of the effect, “falling” being an erroneous word for this situation. I believe falling refers to the attraction of an “object” (in the most general sense) towards a body of great mass due to classical gravitational attraction that is, the attractive gravitational force. Force being a key word here, if the total force is non zero, a net acceleration is present and we see this as “falling” in the everyday sense (even though you don’t necessarily need acceleration to be falling, in empty space, you do). What general relativity predicted (correctly) was that mass curves space, and this is the source of “gravitational attraction” in the classical sense. But the curvature of space can (and does!) change the trajectory of light, but there is no net attraction (in a classical sense, as with falling) between light and the body. So I would rather say that a the curvature created by a body that has some non-zero mass changes the direction of propagation of light, light doesn’t really fall, as no (fundamental) forces act on light). Anywhom, that’s about as much as I know about this subject and it’s my personal position on that subject. Might just be a play on words.

That’s one.