Do not try this at home: explosion risk to heat grapes in the microwave
It is known that putting metal in the microwave will cause sparks to fly, but did you know that putting grapes in the microwave can have more explosive results?
Show key points
- Microwaving grapes, especially when partially cut and connected, can lead to plasma formation and dangerous mini-explosions.
- This explosive phenomenon occurs due to electromagnetic interaction between the grape halves, creating intense hot spots.
- Plasma, known as the fourth state of matter, forms when gases are energized enough to become ionized, like in the sun or lightning.
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- The reason this happens specifically in microwaves is due to the difference in microwave wavelength inside grapes versus in the air.
- Scientists confirmed in 2019 that Mie resonant responses explain how the electromagnetic waves generate plasma in grapes.
- This effect can damage microwaves or even cause fires, making such experiments risky and ill-advised at home.
- Despite the scientific curiosity, you're much better off safely enjoying grapes cold rather than turning them into a fiery snack.
While grapes are a delicious, small-sized fruit that can be gnawed and eaten pleasantly, they also have a dangerous secret: microwave heating them can create a miniature fireworks display and cause plasma to burst.
Do not try this at home: it will explode
This phenomenon has been repeatedly documented on YouTube. When you cut a grape in about half – leaving a portion of the shell that connects the cut sides – and then heat it in the microwave, you'll experience this mess, which is essentially a fusion reaction that leads to plasma formation.
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We are not talking about the flow of plasma through the vessels of human blood. Plasma in this case is the fourth state of matter: ionized gas. Like a liquid evaporating into a gaseous state when boiled, the gas turns into plasma when heated.
If you want an idea of how hot plasma is, think about this: our sun, our cosmic nebulae (interstellar clouds) and our lightning are all in plasma states. This type of heat can cause significant damage beyond overcooking grapes, as it can also lead to the destruction of microwave ovens, fires, and even property damage in extreme cases. So, perhaps, it's best not to try to recreate this little apocalypse at home.
The science behind the fruit explosion
Dr. Derek Müller, physicist and creator of the scientific YouTube channel Veritasium, uploaded a fascinating video to the platform in 2011 where he and fellow physicist Dr. Steve Posey showed the phenomenon of fruit turning into a fireball.
Unfortunately, the explanation that Müller gives in this passage about why grapes "explode" in the microwave is not very detailed - at the time, no one knew why this phenomenon occurred. But that changed in 2019 when some curious scientists from the University of Illinois at Urbana-Champaign began experimenting to uncover the truth behind why plasma arises by microwaveing grapes, publishing their findings in a study in the journal Proceedings of the National Academy of Sciences. As they stated, "Plasma formation is due to electromagnetic hot spots/smudges arising from the joint interaction of Mie resonant responses (Mie resonant response is a type of electromagnetic scattering phenomenon that occurs when an electromagnetic wave interacts with particles larger than the wavelength of the wave) in individual spheres."
In order to translate this technical description, we say that when semi-separated grapes are cooked in the microwave, the electromagnetic field of each piece begins to interact and interact with the other. This reaction creates tons of electromagnetic energy as the grape skin that connects the two halves and the molecules in the area begins to move at breakneck speed, creating a hot spot that ignites a spark and leads to plasma.
The effect of microwave on grapes
So, why does this effect only occur in the microwave? And why does it happen to different types of grapes? Dr. Derek Mueller made a subsequent video in 2019 to answer both questions. As he explains, microwaves generate heat through radiation. Inside the device, microwave wavelengths circulating in the air around the grapes are about 12 cm, however, the wavelengths inside the grapes are much smaller – about 1.2 cm, which is roughly equivalent to the size of the fruit.
Differences in size and the fact that light can quickly travel in grapes can trap microwave rays inside the fruit. Heating grapes in the microwave generates heat from the inside out, not from the outside in, which is the opposite, for example, when you heat Hot Pocket ready-made pancakes in the machine: the outside first heats up and then the heat finds its way inside (which is why, sometimes, the inside of food can remain cold if not given enough time).
However, when a grape is cut so that it is almost completely open, the rays have freedom of movement, and the electromagnetic fields generate enough heat to ionize the air. These newly formed ions can consume more energy (i.e., become hotter), leading to sparks and the formation of hot, smoky plasma.
So, instead, enjoy—maybe next time—only cold grapes – it's safer.
