Light Sprints

light pulse

Small light pulses can now be modified so they slow down

Remember any physics lessons during your high school years? How it was always said the speed of a light was the most unchangeable constant of all? Well… keep reading. In a perfect example of how science changes to perfect itself, scientists at the University of Glasgow have carried out a very interesting set of experiments which ultimately showed that the speed of light can in fact change.

Now, we all know that when light enters a medium, such as water or glass, it slows down. Whereas the speed in a vacuum is said to be 299 792 458 m/s, it can go down to 225 056 264 m/s in water and even 124 018 189 m/s in diamond. This is due to the increased density through which the light has to pass through, so the light particles suffer more collisions which slow it down. But the news come from the idea that speed can also change in a vacuum, even if there is no change in medium and therefore in density.

However, there is a trick. This change in speed won’t happen spontaneously, it has to be slightly triggered. Although it is usually simplified as ‘straight’ or plane waves, where every point travels parallel to each other, light is a bit more complex than that. Two points in a ray of light can actually converge and join, bending their shape. When this effect happens, light speed is affected.

The experiment consisted of a source emitting only two photons. One of them was directed to flow through an optical fibre, so its journey was not interrupted and was as smooth as possible. The other one was passed through a series of apparatus which changed its structure for a short period of time and then restored it back to normal. The time it took each of the photons to arrive to the finish line was measured very precisely. No matter how many repeats the team conducted, the modified photons were always slightly slower and arrived after the untouched one.

The change is speed is not immense, and will have no effect on day-to-day calculations, but it could be have some importance on experiments which use short pulses of light. The fact this effect exists is already worth noting, as it is theoretically obvious but no one had proved it before.


Shedding Light on Light

Messing around with the very essence of matter, scientists at Princeton University in New Jersey have managed to change the nature of light into unprecedented characteristics.

To do so, all you need is a superconducting wire with photons flowing through it and a machine containing 100 billion atoms made of superconducting material. Easy, right?

These atoms can then be modified to act as one single atom, thanks to the unusual properties of superconduction and so once this is done, you just need to push these two objects closer to end up with a group of photons acting like crystals.


Light as we know it has drastically changed

This is so bizarre because usually, photons of light are free from interacting with each other. But in this experiment, they were able to ‘bond’ together to form a crystal structure. This happens because of a quantum process called entanglement, where two photons can become connected over large distances. When the giant atom was brought closer to the photons, these linked to it and exhibited similar properties to it, effectively making light solid. The mechanism could be varied so that light behaved like a liquid or a gas, and with further refinements, like even more exotic materials such as superfluids; fluids with zero viscosity which flow defying gravity.

Although this discovery sounds like just interesting information, it actually has applications. Obviously, it is important to understand matter and how it works (a science named condensed matter physics), since it brings us closer to discovering new materials or characteristics of objects which we can use in our favour. For example, it could help devise the very sought-after room-temperature superconductor, with which electricity could be transmitted in our day-to-day lives with an incredible efficiency, since it offers no resistance.

As if the nature of light wasn’t hard enough to comprehend already, with wave-particle duality, here’s a new behaviour to complicate things even more. Sorry, students, sounds like you’ve got something else to make sense of.

The Tree of Light

Today I bring you an interesting project I came across on my search for a new topic, which I found too interesting to ignore.

When you walk down a street at night, you will probably find lamp posts around you shedding light so you can see where you’re going. If you also happen to be in a park, you will probably see trees somewhere. Well what if I told you there was a way to combine these two seemingly opposite objects into one? The product is a surprisingly simple yet brilliant idea: trees that glow in the dark.

Glowing plants are not new to the field; in fact, they have been around since the 1980s. But it is only in the recent years that the idea of making glowing trees and planting them on the streets has appeared. It could indeed solve many problems: it would cut down electricity use and improve the city’s biosphere, being greener in not one but two ways.

To make a glowing tree, scientists have 2 methods. One involves genetic engineering, where genes from bioluminescent organisms such as bacteria are inserted into plant cells, and if a whole plant develops from that one cell, the whole plant will emit a soft glow. There have also been experiments which used firefly and jellyfish genes, but they were not as efficient and in some cases the plant had to be sprayed with a specific substance for it to actually glow.

The other method, which is a lot more specific, is to dip the plant in a solution of gold nanoparticles. The plant then absorbs the gold into its system, so when UV light is shone onto the plant, the electrons in the gold became excited, and produced a bluish glow when the UV is stopped.

A popular case of glowing plants occurred just last year, when a Kickstarter fund called ‘The Glowing Plant Project’ collected almost $500,000 and with the money was able to create plant seeds which, if treated nicely, would grow into a full, glowing plant. Its aim was to popularize biotechnology and genetic engineering in the mainstream public, and to do so, sent some seeds to all the donors. Of course, there was some repercussions, mostly by scientists disliking the idea of releasing engineered plants into people’s hands with no real regulation.

glowing tree street

Don’t they?

Whether it has drawbacks or not, glowing plants and trees are a fascinating idea, which could have many important applications; the use of glowing trees to substitute lamp posts being only one of many.

They do look pretty cool too.