DO NOT try at home: The Explosive Danger Of Microwaving Grapes
Most people know that metal sparks in a microwave, but few know that grapes pose a greater hazard. If you slice a grape almost in half and leave the skin intact, the fruit turns into a tiny bomb. Microwaves force the grape to spit out a white hot cloud called plasma, a gas so hot that its atoms break apart. The flash looks like a miniature lightning bolt.
Videos of the stunt spread across YouTube. For years no one knew why a cold piece of fruit ignited. In 2019 a team at the University of Illinois at Urbana-Champaign solved the riddle. Microwaves slip into the grape's round body and bounce around. The curved skin and the water inside act like a lens that squeezes the waves to a single point where the two halves touch. The trapped energy grows so strong that it rips the air apart and creates a fireball.
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The fireball is the same stuff that lights the sky during a storm - air whose molecules lost their electrons. Microwaves shake the grape's water molecules until the inside steams. The steam pumps energy into the gap between the halves and the air there glows white. The flash burns the oven walls and can set paper or plastic alight - the trick is not a party joke - it is a kitchen hazard.
Dr. Derek Müller of Veritasium and physicist Dr. Steve Posey showed the effect to millions in 2011. In a later clip Müller pointed out a second quirk. A microwave wave measures about twelve centimetres in air, but shrinks to one centimetre once it enters the grape. The grape is one centimetre wide - the wave fits exactly and rattles around inside. When two halves cling by a thread of skin, the waves in each half line up and double their strength. The joint glows - erupts.
Red or green, keep grapes on a plate in the fridge. They taste better cold and they will not burn your house down.
