Guest Post: The home microwave oven turns 50

by Timothy J. Jorgensen, Georgetown University

The year 2017 marks the 50th anniversary of the home microwave oven. The ovens were first sold for home use by Amana corporation in 1967, but they had actually been used for commercial food preparation since the 1950s. It wasn’t until 1967, however, that technology miniaturization and cost reductions in manufacturing made the ovens small enough and cheap enough (a still steep US$495; US$3,575 in 2017 dollars) for use in the kitchens of the American middle class. Now, it would be hard to find a U.S. home without a microwave.

It will be quick and it will be hot.
1967 promotional image for the Amana Radarange

Amana, a subsidiary of Raytheon corporation, actually called their first model the “Radarange” – a contraction of radar and range (as in stove). What do microwave ovens have to do with radar?

Radar is an acronym for “radio detection and ranging.” Developed prior to World War II, the technology is based on the principle that radio waves can bounce off the surfaces of large objects. So if you point a radio wave beam in a certain direction, some of the radio waves will come bouncing back to you, if they encounter an obstruction in their path.

By measuring the bounced-back radio waves, distant objects or objects hidden from view by clouds or fog can be detected. Radar can detect planes and ships, but early on it was also found that rainstorms caused interference with radar detection. It wasn’t long before the presence of such interference was actually utilized to track the movement of rainstorms across the landscape, and the age of modern radar-based weather forecasting began.

Original cavity magnetron as used to develop radar.
Mrjohncummings, CC BY-SA

At the heart of radar technology is the “magnetron,” the device that produces the radio waves. During World War II, the American military couldn’t get enough magnetrons to satisfy their radar needs. So Percy Spencer, an engineer at Raytheon, was tasked with ramping up magnetron production. He soon redesigned the magnetron so that its components could be punched out from sheet metal – like sugar cookies are cut from dough – rather than each part needing to be individually machined. This allowed mass production of magnetrons, raising wartime production from just 17 to 2,600 per day.

One day, while Spencer was working with a live magnetron, he noticed that a candy bar in his pocket had started to melt. Suspecting that the radio waves from the magnetron were the cause, he decided to try an experiment with an egg. He took a raw egg and pointed the radar beam at it. The egg exploded from rapid heating. Another experiment with corn kernels showed that radio waves could quickly make popcorn. This was a remarkably lucky find. Raytheon soon filed for a patent on the use of radar technology for cooking, and the Radarange was born.

Amana Radarange commercial from 1976.

As time passed and other companies got into the business, the trademarked Radarange gave way to more generic terminology and people started calling them “microwave ovens,” or even just “microwaves.” Why microwaves? Because the radio waves that are used for cooking have relatively short wavelengths. While the radio waves used for telecommunications can be as long as a football field, the ovens rely on radio waves with wavelengths measured in inches (or centimeters); so they are considered “micro” (Latin for small), as far as radio waves go.

Microwaves are able to heat food but not the paper plate holding it because the frequency of the microwaves is set such that they specifically agitate water molecules, causing them to vibrate rapidly. It is this vibration that causes the heat production. No water, no heat. So objects that don’t contain water, like a paper plate or ceramic dish, are not heated by microwaves. All the heating takes place in the food itself, not its container.

Microwaves have never completely replaced conventional ovens, despite their rapid speed of cooking, nor will they ever. Fast heating is not useful for certain types of cooking like bread-baking, where slow heating is required for the yeast to make the dough rise; and a microwaved steak is no taste match for a broiled one. Nevertheless, as the fast-paced American lifestyle becomes increasingly dependent upon processed foods, reheating is sometimes the only “cooking” that’s required to make a meal. Microwave ovens’ uniform and rapid heating make them ideal for this purpose.

Over the years, there have been many myths associated with microwave cooking. But the truth is that, no, they don’t destroy the food’s nutrients. And, as I explain in my book “Strange Glow: The Story of Radiation,” you don’t get cancer from either cooking with a microwave oven or eating microwaved food. In fact, the leakage standards for modern microwave ovens are so stringent that your candy bar is safe from melting, even if you tape it to the outside of the oven’s door.

What’s the deal with metal in the microwave?

Nevertheless, you should be careful about microwaving food in plastic containers, because some chemicals from the plastic can leach into the food. And, yes, you shouldn’t put any metal in the microwave, because metallic objects with pointed edges can interact with the microwaves from the magnetron in a way that can cause electrical sparking (arcing) and consequently damage the oven or cause a fire.

The microwave oven has definitely transformed the way most of us cook. So let’s all celebrate the 50th anniversary of the home microwave and the many hours of kitchen drudgery it has saved us from. But if you want to mark the date with an anniversary cake, best not to cook it in your microwave – you’d likely end up with just a very hot and unappetizing bowl of sweet mush.

Timothy J. Jorgensen, Director of the Health Physics and Radiation Protection Graduate Program and Associate Professor of Radiation Medicine, Georgetown University

This article was originally published on The Conversation. Read the original article.

Guest Post: 2016 lasts a little longer thanks to a leap second

by Darryl Veitch, University of Technology Sydney

To the time-poor of the world: take heart, for 2016 is a generous year. Not only were you granted a leap day on 29 February, you will soon score a New Year’s Eve countdown bonus, a leap second, to hold off 2017 for a final sip or regret.

Whereas leap years add a day to align the calendar with the seasons, leap seconds align our everyday clocks with the Sun’s position in the sky, that is, with the Earth’s rotation.

Currently our planet takes roughly 86,400.00183 seconds (on average) to turn, instead of the expected 86,400 seconds you get by multiplying 24 hours by 60 minutes by 60 seconds. This may not sound like a great difference, but it amounts to a full second every 18 months. If left unchecked, it would become noticeable over time, and ultimately become problematic.

How did we get into this awkward situation? Why not just define a second so that there are exactly the right number? This sensible idea was tried in 1874, but hit a snag: the Earth keeps changing.

In terms of today’s standard SI second (defined via atomic physics), the above discrepancy is due to the fact that the day is losing about 0.0015 seconds per century, due largely to tidal friction.

Not only that, it also changes quite erratically due to mass redistribution.
For example, it is slowed by oceanic thermal expansion due to global warming, just as a playground spinning seat slows, via the conservation of angular momentum, when you place your body farther from the centre.

Leap seconds are used to make sure our usual timekeeping system, Coordinated Universal Time (UTC), never gets more than 0.9 seconds away from the Earth-tracking alternative, Universal Time (UT1).

But unlike leap years, leap seconds cannot be calculated centuries in advance. Because the Earth moves erratically, it must be observed closely, and leap seconds scheduled on an as-needed basis.

In UT1, seconds actually vary in duration, being stretched and compressed to match the Earth’s variations. In UTC, all seconds are standard SI seconds, which is much simpler, but it means that if you want to slow down or speed up UTC, there is no alternative but to jump.

All the leap seconds so far have been “positive”, meaning that an extra second is inserted, corresponding to jumping the clock back, and so slowing it down.

Time’s up for the leap second?

The leap second system has been with us since 1972. It represents an important chapter in the entangled history of civilian timekeeping, and of the definition of the second itself. Its days, however, may well be numbered.

For a number of years, support has been growing within the International Telecommunications Union, the standards body governing leap seconds, to abolish it.

The chief reason is complexity. Simply put, hardware and software can and do get things wrong. And the potential impacts are serious, from failures in navigation leading to collisions, to erroneous financial transactions, computer crashes and the inability to specify UTC times reliably into the future, because the leap second times are not yet known!

Because UTC jumps back at a leap second, effectively the second before the leap is repeated. Managing such “time travel” is inherently complex and error prone, so much so that in many cases the recommended action is to simply shutdown the system and restart it after the leap.

A dramatic illustration of the problem can be found in the internet. All computers have software clocks that generally rely on communication with time servers over the network to synchronise to UTC. Network timekeeping is a core internet service, and at its heart are the Stratum-1 servers, which have direct access to reference hardware such as atomic clocks.

We collected data from around 180 such servers around the world during the June 2015 leap second event, and assessed them from two points of view.

First, the clocks themselves: did they jump cleanly and sharply exactly as required?

Second, at the protocol level, that is with respect to the messages the servers send to the computers that rely on them: did they inform them properly of the upcoming leap?

Overall, we found that, at most, 61% of the servers were performing correctly. Many of the servers are well known and highly utilised, potentially impacting thousands of clients, possibly resulting in security vulnerabilities.

An expanded experiment is currently underway for the 2016 event, involving almost 500 servers, including from the widely used ntppool project.

This is part of a broader network timing project at UTS led by myself together with Dr Yi Cao, which aims to refashion the global system, and in particular to make it scale in a trusted way to the Internet of Things.

Finally, we must point out that leap seconds occur simultaneously across the globe, and it can’t be midnight everywhere.

Thus, as I confirmed with Dr Michael Wouters, responsible for Australia’s reference time at the National Measurement Institute, for us it will occur at 11am AEDT on January 1, 2017. Save the last sip till then.



Darryl Veitch, Professor of Computer Networking, University of Technology Sydney

This article was originally published on The Conversation. Read the original article.