HYWW:

Grapes in the microwave; bicycle luggage; oneperson commuter pod; SAmade water-recycling truck.

WHO KNOWS the reasons a scientist may have for choosing the question that will shape his or her life’s work. Maybe, when pondering life’s great mysteries, they prefer the guidance of physics to that of religion. Maybe they have always dreamed of circling the Earth in the International Space Station, watching the Sun rise every 90 minutes over the soapy blue of their home planet. Maybe they accidentally put a fork in a microwave one time. Or maybe it was the microwave thing, but with a grape.

The scientist in question, Aaron Slepkov, discovered the old grapein-the-microwave trick when he was young. It’s the one where a sliced grape erupts into a fireball of plasma – an ionised gas that is considered the fourth state of matter and is present in large quantities in, among other places, the Sun.

Twenty years later, Slepkov, now a physics professor at

Trent University, took on his own experiment to explain how the phenomenon worked. His findings were published in the journal Proceedings of the National Academy of Sciences of the United States of America.

‘In 1995, Slepkov had found the first website describing making plasma in a microwave, and he got really fascinated with it and kept it in the back of his mind,’ says study co-author Pablo Bianucci, PhD, and physics professor at Concordia University.

From a thorough inspection of the internet’s best ‘microwaved grape fireball’ videos, it seems to be necessary to cut the grape in half before microwaving, leaving a small, ion-rich skin bridge between the two hemispheres.

‘The more or less consensus explanation was that the grape would work as an antenna, and

that would create a current through the skin bridge that would eventually heat it up and create the plasma,’ says Bianucci.

Through the sacrifice of untold masses of grapes (and 12 microwaves), the researchers showed that this hypothesis – which had never been explained mathematically anyway – was false. Not only is a skin bridge between the grape halves not required, but you can ignite a plasma fireball in two whole grapes placed side by side in a small bowl, or two ground cherries, two quail eggs, or even two hydrogel beads of the type used in diapers.

Using microwaves with the doors removed, ‘they managed to decouple the generation of the plasma – the really flashy thing you see – from the actual phenomenon that’s going on underneath, which is the focusing of the electromagnetic radiation, the microwaves, in between the two spheres,’ Bianucci says.

It turns out that water-based orbs about the size of a grape amplify microwaves (which is electromagnetic energy, just like light) so effectively that a hotspot just between the two orbs creates plasma.

Apart from being cool, this research may someday contribute to the better understanding of a field called nanoplasmonics.

‘If you put, for instance, two metal nanoparticles next to each other, you have this same effect – a really increased electromagnetic field, but with the metals you see it with light instead of microwaves,’ says Bianucci. ‘The key thing is that the water has a high reflective index, so it shrinks the wavelength a lot. If we were able to find a material that works like water, but for light, where we could really shrink the wavelength of light, then we could probably use it to focus light into very, very small spaces.’

“THE GRAPE WOULD WORK AS AN ANTENNA THAT WOULD CREATE A CURRENT.

Cut a grape part of the way through, leaving two halves that are still connected by a small piece of skin. When placed in the microwave, the radiation causes the grape to increasingly spark from the middle.