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# From Post-it Notes to microwaves – why serendipity lies at the heart of innovation

19 May 2020 James McKenzie
Taken from the May 2020 issue of Physics World, where it appeared under the headline "Serendipity in action". Members of the Institute of Physics can enjoy the full issue via the Physics World app.

Accidental discoveries lie at the heart of many technological innovations. James McKenzie runs through his favourites

Writing in this column two years ago, I quoted Geoffrey Nicholson – the father of the Post-it Note. While working at the US adhesives giant 3M, he is alleged to have said that “research is the transformation of money into knowledge; innovation is the transformation of knowledge into money”. But don’t imagine that innovation is a planned, formulaic process. It’s not a case of pouring the funds in and waiting for new technology and innovative products to pop out.

The invention of the Post-it Note, for example, was entirely accidental. Spencer Silver, a scientist at 3M, had been studying strong adhesives when he came across one that was seemingly useless. As he later recalled, it “stuck lightly to surfaces but didn’t bond tightly to them”. Silver initially had no idea what to do with his discovery, but years later another 3M scientist, Art Fry, suggested creating a bookmark that could stick to paper without damaging it.

Thanks to Nicholson’s vision, that bookmark eventually became the Post-it Note and is now a classic example of an invention or new technology looking for an application. Another is penicillin, which Alexander Fleming discovered in 1928 after leaving out some old bacterial cultures and noticing a few weeks later that some mold had killed the bacteria.

There are so many examples of serendipitous inventions that I wonder if the only way to discover things is by accident.

Then there’s vulcanized rubber. The American chemist Charles Goodyear had been trying to create a weatherproof rubber for years, but succeeded in 1839 only when he accidentally dropped some regular rubber mixed with sulphur onto a hot stove and found that it still maintained its structure.

In fact, there are so many examples of serendipitous inventions – take your pick from superglue, Coca Cola, Teflon, champagne and chewing gum – that I wonder if the only way to discover things is by accident.

### The X-factor

The first accidental physics-based discovery that I can think of occurred on 8 November 1895 when the physicist Wilhelm Conrad Röntgen was experimenting in his laboratory in Würzburg, Germany. Studying a vacuum tube covered in cardboard, he suddenly noticed a mysterious glow emanating from a chemically coated screen nearby.

After playing around some more, Röntgen discovered that when he put his wife’s hand between the glow and the screen, he was able to see her bones. This observation led to the world’s first X-ray photographs, with Röntgen going on to win the inaugural Nobel Prize for Physics in 1901. His finding revolutionized diagnostic medicine.

Perhaps my favourite example involved Percy Le Baron Spencer. Employed as a physicist at Raytheon in the US, in 1945 he was studying the high-powered microwaves emitted by an active radar set when he noticed that a chocolate bar in his pocket had melted.

Seeking to verify his accidental discovery, Spencer created a high-density electromagnetic field by feeding the microwave power from the magnetron into a metal box from which it had no way to escape.

When he placed popcorn in the box and fired up the magnetron, Spencer discovered that the temperature rose rapidly and the corn popped. On 8 October 1945 Raytheon filed a US patent application for Spencer’s microwave cooking process, and an oven that heated food using microwave energy from a magnetron was soon placed in a Boston restaurant for testing.

When he placed popcorn in the box and fired up the magnetron, Spencer discovered that the corn popped.

By 1947 Raytheon had built the “Radarange” – the world’s first commercially available microwave oven. Almost 1.8 m tall and weighing 340 kg, this colossus cost about $5000 (roughly$57,000 in today’s money). It consumed 3 kW of power, about three times as much as today’s microwave ovens, and was water-cooled. Unsurprisingly, it wasn’t an overnight success and only sold into niche commercial applications where the speed of cooking mattered. One early example was installed in the galley of the first nuclear-powered merchant ship the NS Savannah.

Things didn’t progress much until the late 1970s when Japanese companies such as Sharp Corporation figured out how to make microwave ovens small and cheap enough for people to use at home. The market boomed and I can remember my own family buying one of these early cookers in the 1980s. My father thought it was amazing (in fact, I suspect he bought it himself) but my mother wasn’t impressed. Still, what was wonderful was you could bake a potato in it in under four minutes.

## Do try this at home

All the discoveries I’ve mentioned occurred more by accident than design, but don’t assume that scientific discoveries automatically lead to technological innovation and overnight command sucess. Bringing real, commercial products to market takes significant time, effort and know-how.

Nevertheless, I hope we don’t end up in a risk-free world where ad-hoc experimentation is stifled by worries over process or by overzealous health and safety concerns. After all, who knows what we might be missing out on.

Realizing that many of you may still be self-isolating or stuck indoors by the time you read this article, let me finish by giving you a couple of great (and safe) physics experiments you can do with your own microwave oven. One is to cut a grape nearly in half and place it inside, with the cut side facing up. Turn the oven on for 10 seconds and, boom, you’ll create some fantastic plasma balls. The other is to use your microwave to measure the speed of light with a chocolate bar. I’ll leave it to you to figure out exactly how.

In fact, perhaps the current period of enforced isolation will get the entire physics community thinking great thoughts and making amazing discoveries. After all, remember what happened when the plague forced Isaac Newton to flee Cambridge for the family home in Lincolnshire – he only went and devised the universal law of gravitation. So who knows what fantastic new technologies will emerge from the current lockdown in years to come?