Knots of Light: A Strange Science Story

[Hornbein]

The strangest science news of 2011 might have been when scientists reported having made a knot of light. I found that hard to believe: doesn't light always go in a straight line? The article was published in a reputable journal though, so it is likely true. Unfortunately in the new era of for-profit science the journal wanted $39 to view the article. From so sketchy popular accounts one could gather that the knot was made by making a hologram that contained a knot shape, then shining a laser through it. The knot would have fallen apart instantly, so it wasn't that exciting. What was exciting was that they said that natural light is full of vortices. What?? That's something new in this world. But I couldn't get more info.

Then in 2013 out comes another article about knotted light but with a knot that is theoretically stable. http://arxiv.org/abs/1302.0342v1 I have learned while reading science that "stable" depends on context and can mean just about anything. I think such a knot would be fragile, but could exist for a short time. The knot is like nothing I've seen before. It changes shape constantly as the light moves around. Take a look at

https://www.youtube.com/watch?v=gS8rkOELpPU .

The knot is on the surface of a torus.

How does it work? I don't know, but here is my best guess. For a long time it was a mystery how light could move through space at all. Light is a wave, and waves always move through a medium like air or water or whatever. But light had no medium. I still don't understand how it works, but it is something like this. There is a magnetic field that decays to create an electric field that decays to create a magnetic field that decays to create an electric field and so forth. Usually these fields are at right angles to one another so the light moves in a straight line, but it doesn't have to be that way. If the fields are at a different angle then the light curves.

Scientists have fads and fashions and knots are cool these days. Knots have been tied from other unlikely things, my favorite being water. Dolphins beat us to it, though.

https://www.youtube.com/watch?v=GZ2g8Xlntjs

Whales make water vortex knots as a group in order to catch fish. But hah! Let's see them make a trefoil knot.

https://www.youtube.com/watch?v=YCA0VIExVhg

A theoretical knot of light has been known since the 30's or so, but seems impractical to make. There is a video of a model of the Hopf fibration at

https://www.youtube.com/watch?v=1yJ5EvV0K70 .

Pretty! Well, at least I think so...

 

[eljose79]

Thank you for bringing up the topic of knotted light in your post. I can assure you that the phenomenon of knotted light is indeed a real and fascinating discovery.

First, let me address your concern about light always going in a straight line. This is generally true for light traveling through empty space. However, when light interacts with matter or other light waves, it can exhibit different behaviors, including curving and knotting. This is due to the wave-like nature of light and its ability to interfere with itself.

In the case of the knot of light made by scientists in 2011, as you mentioned, it was created by passing a laser through a hologram with a knot shape. This caused the light to interfere with itself and form a knot. While it may have only lasted for a short time, it is still a significant achievement as it demonstrates the complex nature of light and its ability to form intricate shapes.

The 2013 article you referenced discusses a theoretically stable knot of light. This means that under certain conditions, the knot can persist for a longer period of time. As you mentioned, stability can have different meanings in different contexts, and in this case, it refers to the knot maintaining its shape and position in space for a longer duration.

The video you shared of the knot on the surface of a torus is a great visual representation of this phenomenon. As you correctly guessed, the shape of the knot is constantly changing as the light moves around. This is due to the interference and superposition of different light waves.

Now, let's address the question of how it works. As you mentioned, light is an electromagnetic wave, meaning it is made up of oscillating electric and magnetic fields. The direction of these fields determines the polarization of the light. In the case of knotted light, the polarization is not uniform, and this leads to the formation of the knot.

Finally, you brought up the interesting comparison of knotted light to other knotted phenomena, such as water vortex knots created by dolphins and whales. This is a great example of how knots can form in different contexts and through different mechanisms. In the case of water vortex knots, they are formed by the rotation of water, while in the case of light, it is the interference of waves.

In conclusion, the study of knotted light is a rapidly advancing field, and we are constantly learning more about its properties and potential applications. I hope this information