Learn more about how microwaves have changed the way we communicate and helped us understand the origins of the universe.
The Pope is watching. This had a better job. Such thoughts probably crossed Guglielmo Marconi’s mind in 1932 as he set up a special antenna in the Vatican gardens while His Holiness Pope Pius XI watched.
The antenna was part of a new radio link connecting the Vatican to the Pope’s summer residence, Castel Gandolfo. And not just any radio link.
This one used microwaves – very high frequency radio waves. Marconi also created a portable microwave communication device attached to a car, connecting the traveling Pope with the Vatican. Some have said that this was the first mobile phone, albeit a very large one.
Thirteen years earlier, Marconi had shared the Nobel Prize in Physics with Ferdinand Braun for his contribution to the wireless telephone. The radio age was in full swing. But when Marconi switched to microwaves, he was embracing the role of radio with very unique properties.
Microwaves can transmit a lot of information. They can also cook food, or destroy enemy electronics. Microwaves even help reveal the origins of the universe.
Pip-pip-pip
Long before Marconi built a microwave for the Pope, someone else had already experimented with the same frequency.
At the end of the 19th Century, a brilliant Indian scientist named Jagadish Chandra Bose – now, sadly, largely forgotten – invented some of the first microwave technology.
This included the first devices to generate millimeter waves – the frequencies used by 5G devices today. In 1895, Bose showed that millimeter waves can ring a bell, and even fire a gun from a distance.
There is no doubt that Marconi gained some of his fame because of Bose.
On December 12, 1901, using microwaves, an Italian inventor made the first transatlantic radio transmission. Sitting in a hut on a cliff in Newfoundland, he listened to the swirling flood of noise in his ear for hours – until he heard what he had been waiting for.
Pip-pip-pip.
Morse code for the letter S. Frustrated, he turned the receiver to his colleague and asked, “Do you hear anything?” He could.
It was an amazing act. Those radio waves had traveled more than 2,000 kilometers from southern England, across open water. At the time, his record for the longest radio transmission was only 80 kilometers.
Over the years, some have questioned whether the transmission actually happened as Marconi described.
However, recent research shows that it was possible, even with his original radio equipment.
Among the equipment was a machine called a coherer, a simple device for detecting radio waves. Although the records are a bit sketchy, it seems that this accessory was made by none other than Bose.
Bose’s biographer, Sudipto Das, says: “He brought with him some fascinating instruments.
But Bose, perhaps, was far ahead of his time. First, there were several important microwave applications in the early 1900s that were no longer possible with low-frequency radio waves. Bose shifted his focus from physics to his main interest, plant physiology, and “became almost forgotten,” says Das.
Magnetron popcorn
However, the Second World War made microwaves important again. Radar allowed soldiers to spot enemy planes by intercepting radio signals from them. And a microwave device called a cavity magnetron developed in Britain in 1940, became one of the most powerful and effective radar technologies around.
Small enough to be carried on an airplane, its incredible range and accuracy gave the Allies a critical advantage that helped them win the war.
It was also the microwave-emitting magnetron that inspired Raytheon engineer Percy Spencer to invent microwave ovens in 1945. The peanut butter in his pocket began to melt when he passed the magnetron in the laboratory. And then when he lifted a packet of popcorn, the creation appeared and “exploded all over the laboratory,” a Reader’s Digest article later recalled.
This happened because, at a certain frequency, the microwaves excited the molecules in the food, causing them to vibrate at the same frequency. The ensuing conflict heats things up.
For microwave ovens, the choice is usually 2.4 gigahertz (GHz) – the same frequency used by many wi-fi routers. However, routers emit microwaves at much lower power than microwave ovens – that’s why you can’t make popcorn by just surfing the web.
Choosing the right cooking frequency is very important, says Caroline Ross of the Massachusetts Institute of Technology. Microwaves at 2.4 GHz penetrate well into food, and these frequencies also allow radiation to be absorbed by food molecules.
“When you go higher, like tens of gigahertz, the penetration depth is very small, so it blocks almost anything – even water in the air,” he explains.
Microwaves are unique because of their ability, at certain frequencies, to interact with matter. OK, reheating your leftovers might not sound like much fun – but what about using microwaves to put noise in people’s heads?
Havana syndrome
Military personnel who worked near the large microwave radar facilities built during World War II later recalled being able to see the radar in action. One witness wrote in the 1950s: “It was possible to hear the radar repetition rate when we were standing near the horn.
James Lin, a distinguished professor at the University of Illinois at Chicago, heard such stories and tried to reproduce the results in his laboratory in the 1970s.
“I was basically working like a guinea pig,” he recalls, explaining how he set up a microwave antenna and pointed it directly at his head.
Lin suggested that the microwaves induced pressure waves inside his head, which he heard as sound. To avoid cooking his brain, he kept his energy low. He says: “I could feel my heart beating. The fact that I was still alive … I guess it wasn’t too bad.
This became known as the “microwave auditory effect” and may help explain a series of mysterious illnesses reported by American diplomats around the world, most famously in Havana, Cuba.
Victims of the so-called Havana Syndrome report experiencing a strange grating noise, a feeling of increasing pressure in their ears, dizziness, nausea and memory loss. Was the enemy directing a microwave beam at these people? Although some have dismissed this theory, Lin says it is still the most reasonable explanation for the sensory symptoms.
Microwave weapons do exist, although those discussed in public tend to target machines rather than humans. The US military has missiles that can destroy enemy electronics with microwaves, for example. Microwaves can even take down drones.
On the other hand, Lin has developed ways to use microwaves for healing – for example, treating muscle diseases and irregular heartbeats.
For the latter, he says it is possible to insert a small machine that emits microwaves into the heart, through a catheter, in order to destroy abnormal heart cells. This method, which is now widely used, is less invasive than open-heart surgery, he points out: “Just give the heart a high-energy pulse, a microwave, to burn the cells.”
The universe speaks
But microwaves don’t just save lives. They also helped to reveal the origin of the universe. In the early 1960s, radio astronomers Arno Penzias and Robert Woodrow Wilson tried to use a large, horn-shaped antenna in the US state of New Jersey as a radio telescope. But they kept picking up a shrill or static whistle.
At one time, they thought it was due to pigeon droppings in the horn, so they chased the birds away and cleaned the mess. However, these birds were not to blame. What Penzias and Wilson were hearing was the sound of the universe itself.
Sean McGee of the University of Birmingham says: “It’s a picture of the first time. Penzias and Wilson had discovered what we now call cosmic microwave background radiation – a signature left over from the Big Bang, when the universe exploded about 13.8 billion years ago. Penzias and Wilson were awarded half of the 1978 Nobel Prize in Physics for their work.
The rest of the radiation they observed is present throughout the universe. There is a small amount of snow that sits on analog television screens because of this. In other words, until LED screens took over, people would carry the remnants of the Big Bang into their living rooms.
Satellites eventually helped astronomers map the microwave atmosphere, recording its changes as subtle temperature variations. That fluctuation seems to have influenced where galaxies formed as the universe expanded.
“We are all the result of fluctuations in the early universe that gave birth to galaxies,” says McGee.
Today, people use microwaves for any international satellite phone call. A huge jump in the cargo that Marconi carried in the Pope’s car in the 1930s.
It is appropriate that many people use microwaves to communicate every day, every day – because this is how the universe has spoken to us, helping to ensure our understanding of the greatest story of all time. The story of how it all began.
By Chris Baraniuk, BBC World Service. This content is produced in partnership between Nobel Prize Outreach and the BBC.
Published in March 2026
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