9th July: Microwave ovens

Today is the birthday of Percy Spencer who invented microwave ovens. 10 things you may not know about microwaves:

1. Microwave ovens were discovered accidentally. Percy Spencer hit on the idea when he was building radar equipment in a lab for Raytheon, and noticed that a Chocolate bar in his pocket had melted. He tested his idea by popping Popcorn and exploding an Egg.
2. Microwave ovens do not cook food from the inside out. In fact, the opposite is true. They work on the outer layers of food, heating it by exciting the water molecules. The heat transfers from the outer layers inward.
3. Metals reflect microwaves, whereas plastic, glass and ceramics allow them to pass through. Metal doesn't heat up dangerously in a microwave, but thin pieces of metal, such as foil or the tines of a fork, can act as antenna, and the waves arc off them, forming sparks.
4. Oil doesn't heat up well in a microwave because its molecules behave differently to those of Water. Thawing frozen Butter is hard to do in a microwave, partly because it is mostly oil but also because any water there is is ice, and ice crystals are harder to excite.
5. Boiling water in a microwave is actually quite dangerous. If it is heated for too long, water can become hotter than its boiling point if bubbles don't form. If this happens, as soon as the water is disturbed, by moving it or by putting something in it, the heat is released rapidly and it can erupt boiling water out of its container and scald you. Putting a wooden spoon in the cup and not heating it for too long minimise the risk of this happening.
6. It is also dangerous to heat plastic in microwaves. Scientists found that even plastic containers labelled as microwave safe can release Bisphenol A at levels that scientists have found cause neurological and developmental damage in laboratory animals.
7. Over 30 million microwave ovens are sold throughout the world every year.
8. The first commercial microwave oven was called the ‘Radarrange’. It went on sale in 1947 for $5000. It was 1.8 metres tall and weighed 340 kilograms. The machine was cooled by water and consumed three times as much power as today’s microwaves.
9. There is no proven evidence that anyone has ever been harmed by using microwave ovens.
10. A Welsh word for a microwave oven is Popty Ping, which literally translates as "oven that goes ping". Although "microdon" is the official word, "Popty Ping" sounds much more evocative of the microwave oven!