Monday, January 23, 2012

All About Microwaves

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Here is more than you ever wanted to know about Microwaves

First of all, here are the basics...
Microwaves have wavelengths that can be measured in centimeters! 
The longer microwaves, those closer to 30cm in length, are the waves 
which heat our food in a microwave oven. 
However, microwaves are good for a lot more than just cooking.
Before the advent of fiber-optic transmission, most long-distance telephone calls were carried via networks of microwave radio relay links run by carriers such as AT&T Long Lines. Starting in the early 1950s, frequency division multiplex was used to send up to 5,400 telephone channels on each microwave radio channel, with as many as ten radio channels combined into one antenna for the hop to the next site, up to 70 km away.
Microwaves are excellent for transmitting information from one place to another because their energy can penetrate haze, light rain and snow, clouds, and smoke. 
In the 1950s, Canada became a communications innovator with the creation of the Trans-Canada Skyway - a microwave system purpose-built to carry telephone and TV from Canada's east coast to its west coast. Because microwaves travel in a straight line and do not follow the curvature of the Earth, towers were built every 48 kilometres. The towers ranged from nine metres high to over 100 metres high in northern Ontario. The system included 139 towers spanning over 6275 kilometres and cost $50 million ($386 million in 2012 dollars).
It took just one-fiftieth of a second for a microwave signal to travel from one coast to the other. The Trans-Canada Microwave system was officially completed on 1 July 1958. At the time, it was the longest microwave transmission network in the world, stretching from Sydney, Nova Scotia to Victoria, British Columbia, placing Canada at the forefront of communications technology. The system was implemented under Bell Canada president Thomas Wardrope Eadie as an all-Canadian microwave network for transporting telephone conversations, Teletype messages and television signals.
This microwave tower can transmit information like telephone calls 
and computer data from one city to another.
Today, microwave radio is used in broadcasting and telecommunication transmissions because, due to their short wavelength, highly directional antennas are smaller and therefore more practical than they would be at longer wavelengths (lower frequencies). There is also more bandwidth within the microwave spectrum than in the rest of the radio spectrum; the usable bandwidth below 300 MHz is less than 300 MHz while many GHz can be used above 300 MHz. Typically, microwaves are used in television news to transmit a signal from a remote location to a television station from a specially equipped van.
Most satellite communications systems operate in the C, X, Ka, or Ku bands of the microwave spectrum. These frequencies allow large bandwidth while avoiding the crowded UHF frequencies and staying below the atmospheric absorption of EHF frequencies. Satellite TV either operates in the C band for the traditional large dish fixed satellite service or Ku band for direct-broadcast satellite.

How do we "see" using Microwaves?

Shorter microwaves are used in remote sensing. These microwaves are used for radar like the doppler radar used in weather forecasts and are just a few inches long. 
Radar is an acronym for "radio detection and ranging." Radar was developed to detect objects and determine their range (or position) by transmitting short bursts of microwaves. The strength and origin of "echoes" received from objects that were hit by the microwaves is then recorded.
Because radar senses electromagnetic waves that are a reflection of an active transmission, radar is considered an active remote sensing system. Passive remote sensing refers to the sensing of electromagnetic waves which did not originate from the satellite or sensor itself. The sensor is just a passive observer. 

What do Microwaves show us?

Because microwaves can penetrate haze, light rain and snow, clouds and smoke, these waves are good for viewing the Earth from space. The ERS-1 satellite sends out wavelengths about 5.7 cm long (C-band). This image shows sea ice breaking off the shores of Alaska.
The JERS satellite uses wavelengths about 20 cm in length (L-band). 
This is an image of the Amazon River in Brazil.
This is a radar image acquired from the Space Shuttle. It also used a wavelength in the L-band of the microwave spectrum. Here we see a computer enhanced radar image of some mountains on the edge of Salt Lake City, Utah.
In the 1960's a startling discovery was made quite by accident. A pair of scientists at Bell Laboratories detected background noise using a special low noise antenna. The strange thing about the noise was that it was coming from every direction and did not seem to vary in intensity much at all. If this static were from something on our world, like radio transmissions from a nearby airport control tower, it would only come from one direction, not everywhere. The scientists soon realized they had discovered the cosmic microwave background radiation. This radiation, which fills the entire Universe, is believed to be a clue to it's beginning, known as the Big Bang.
The image above is a Cosmic Background Explorer (COBE) image of the cosmic microwave background, the pink and blue colors showing the tiny fluctuations in it.
Text and images via NASA and Wikipedia

How Safe is Your Microwave Oven?

By Matthew Kadey
How Safe is Your Microwave?
Today's kitchens are increasingly filled with conveniences that help get food on the table fast. Bagged salad greens. Rotisserie chickens. Single-serving instant oatmeal. Grated cheese. And when it comes to appliances, nothing beats the ubiquitous microwave for quick and easy cooking.
Most of us use our microwaves without giving it another thought: Pop in a frozen dinner or last night's leftovers, and lickety-split it’s a hot meal. Despite worrisome terminology such as "radiation" and slang expressions like "nuking," microwave ovens have worked their way into most kitchens and practically every break room in this country. They're a staple of our lives.
But does anyone really know what's going on inside the oven once you shut the door? How healthy or unhealthy is "nuking" your food? And if we can't live without our microwave ovens, what's the best way to live with them?

Know Your Nuker

Let's start with some history: Around the end of World War II, an engineer discovered that the radar waves used to detect planes could also heat food. The first beastly microwave oven, called the Radarange, debuted in the late 1940s. A more user-friendly consumer countertop model hit store shelves two decades later. Soon afterward, the microwave became a miracle, must-have household appliance.
People often say they are going to "nuke" their food, which is based on the common belief that microwaves reheat food by releasing radioactive energy. This is not, however, the case. Microwaves work by using a magnetron that converts electric power into waves of oscillating electromagnetic energy, often referred to as microwaves, that are similar to radio waves, explains Juming Tang, PhD, professor of food engineering at Washington State University in Pullman, WA. "These waves permeate food, causing the agitation of water molecules and charged salt ions, which produces friction and a quick rise in temperature to warm the food rapidly," he says.
Tang goes on to say this is why the cooking times with microwave ovens are shorter than with conventional ovens: The latter oven sends heat through food relatively slowly, moving radiant heat inward from the outside.
"In a microwave oven," says Tang, "the air in the appliance is at room temperature, so the temperature of the food surface is cooler to the touch than food placed in a conventional oven, where the items are heated by hot air or by radiative heat." For this reason, to the angst and disappointment of many a home cook, food cooked in a microwave doesn't generally become brown and crispy. The bigger concern about microwaves, though, is that while they are heating your food, they are also zapping valuable nutrients.

Where Nutrients Go to Die

According to microwave skeptics, the intermolecular friction created by the appliance reduces the bioavailability of essential vitamins and minerals, such as B vitamins and vitamin C. And it can even change the chemical composition of foods, including animal proteins and dairy.
"When food, including baby formula, is microwaved, it has been demonstrated that certain amino acids, which are the building blocks of protein, are converted from their natural, active forms into biologically inactive forms," says Lita Lee, PhD, a chemist and enzyme therapist in Portland, Oregon. Beyond the vitamins and minerals, she explains, foods contain a plethora of delicate and complex compounds, including antioxidants and enzymes, which could be negatively affected by microwaving.
Skeptics like Lee are buttressed by a number of studies suggesting the nutritional impacts of microwaving food are not entirely rosy. Japanese researchers determined that microwaving may convert vitamin B12 - a vitamin vital to proper neurological functioning, among many other things - in meat, pork and milk into its inactive form, rendering it somewhat useless.
Studies also show that heart-healthy phenolic compounds found in extra-virgin and virgin olive oils can lose some of their antioxidant capacities when exposed to microwaving, and that microwaving garlic can destroy its most powerful medicinal compound, allicin.

Comparative Cooking

A batch of other studies show, however, that the news surrounding microwaving and nutrient retention may not be so unappetizing after all, at least when compared with some other cooking methods - particularly boiling.
United Kingdom researchers reported in the journal Food and Chemical Toxicology that cooking a range of cruciferous vegetables like broccoli by steaming, stir-frying and microwaving did not produce a significant loss of glucosinolates, which are powerful disease-thwarting antioxidants. But when researchers boiled these same kinds of vegetables, they reported major glucosinolate losses through leaching into cooking water.
A 2009 Journal of Food Science study tested the antioxidant capacity of 20 vegetables, including Swiss chard and zucchini, when exposed to different cooking methods. Researchers found that microwaving drained antioxidant power less than pressure cooking and boiling.
"It's clear that water is not a cook's best friend when it comes to nutrient retention, whether in the microwave or on the stovetop," says Barry Swanson, PhD, a food science professor at Washington State University. This could be why a much-publicized 2003 European study found that microwaving decimated broccoli's flavonoid antioxidant levels. "The study authors added way too much water and cooked the vegetable for longer than what would occur in a normal household situation," notes Swanson.
He says that compared with more destructive methods like boiling, the relatively mild temperatures and short cooking times associated with microwaving can do a good job at retaining nutrients in produce - as long as you use little, if any, water and don't cook the life out of them. "High amounts of water provide a sea into which nutrients can get washed away," Swanson says.
"There are many factors and conditions such as time and amount of added liquid that affect the nutritional value of food when cooked in the microwave," says Samer Koutoubi, MD, PhD, a professor in the Department of Nutrition and Exercise Science at Bastyr University in Kenmore, Washington. "Many of the reported losses of nutrients, including vitamin C, were mainly due to excess cooking water and spending too much time at the highest heat setting."
Lee disagrees that excess water or cooking time is mainly to blame for nutrient loss. "Microwaving four seconds or longer will destroy nutrients - by changing them to biologically inactive forms - and create toxins and carcinogens. Stovetop cooking cannot compare to the damage of microwaving."
Given the conflicting evidence, it's clear that a consensus on the nutritional impacts of microwaving is probably anything but imminent. So for now, it is up to individual cooks and eaters to decide whether they want to ditch their nuker, or embrace it with cautious enthusiasm. If you decide on the latter, stay tuned for future posts on safe microwaving. And if you decide on the former, think not just of the antioxidants you might save, but also of the valuable counter space you stand to reclaim.

Text and images via Care2

Seven surprising facts and myths 

about microwave ovens

By Brian Clark Howard
Search the Internet for "are microwave ovens safe," and you'll get a barrage of hits from concerned parents and others who are worried that the handy device might have a dark, even dangerous side.Of course, the prevailing consensus among scientists, public health experts, government agencies, and the general populace is that microwave ovens are overwhelmingly safe when used as directed. However, it's also true that there may be some legitimate questions about the safety of certain aspects of the technology.
Let's take a closer look at some myths, facts, and misconceptions about microwave ovens, which are estimated to be used in at least 90% of American homes.
tv dinner 

Heating plastics in a microwave oven can be dangerous

Status: Fact
The safest course of action is to avoid putting any plastics in the microwave.
When the Milwaukee Journal Sentinel tested plastics labeled microwave-safe and advertised for infants, even those were found to release "toxic doses" of Bisphenol A when heated in a microwave. "The amounts detected were at levels that scientists have found cause neurological and developmental damage in laboratory animals," the paper reports.
In fact, the term "microwave safe" is not regulated by the government, so it has no verifiable meaning. According to the Journal Sentinel's testing, BPA "is present in frozen food trays, microwaveable soup containers, and plastic baby food packaging."
It is often found in plastics marked No. 7, but may also be present in some plastics labeled with Nos. 1, 2, and 5 as well, according to the report. Better to stick to glass or ceramics.

Metals get dangerously hot in microwaves

Status: Myth
Metals reflect microwaves, whereas plastic, glass, and ceramics allow them to pass through. That means metals don't appreciably heat up in a microwave oven.
However, thin pieces of metal, such as foils or the tines of a fork, can act as antenna, and the microwaves can arc off them, forming dramatic sparks.

drawing of microwaves in microwave oven 

Microwaves leak unsafe levels of electromagnetic radiation

Status: Myth (at least most of the time)
For decades, scientists and consumers have debated the possible effects of non-ionizing electromagnetic radiation on living tissue. It's very difficult to sort out the various risks we might get from fields emitted from power lines, cell phones, airplane flights, computers, clock radios, and, of course, microwave ovens. We know strong fields raise cancer rates and other problems, but what about the cumulative effect of small exposure or the effects on children?
No one knows, although we can take heart that theFDA limits the amount of microwaves that can leak from an oven throughout its lifetime to levels "far below the level known to harm people."
The federal standard also requires all ovens to have two independent interlock systems that stop the production of microwaves the moment the latch is released or the door opened. It's also true that microwave energy decreases dramatically as you move away from the source of radiation. So, if you are concerned, you can simply step away from the microwave when in use.
In an interview with TDG, mechanical engineer Mark Connelly, the deputy technical director of Consumer Reports, said that the vast majority of microwave ovens his group has tested have shown "very little leakage of radiation."
Asked if people should avoid looking into a working microwave, since the eyes are known to be the most sensitive to that form of radiation and are known to develop cataracts at high field strengths, Connelly said he didn't think it mattered, "since the window is shielded, and there shouldn't be leakage through that."
"If you are concerned, then go out and spend $20 on a testing kit to reassure yourself that there isn't any radiation leaking from your microwave," Connelly added. He said his testing of consumer-grade kits has shown them to be reasonably reliable, despite some press accounts to the contrary. "Microwaves can wear over time, with gaskets wearing or trouble developing in the door. So I think it's prudent to spend a little money to test them," he said.

Boiling a cup of water in a microwave can cause it to explode

Status: Fact
One potential danger of microwave ovens is getting scalded by over-heated water. When plain water is heated in a microwave in a clean ceramic or glass container for too long, it can prevent bubbles from forming, which normally cool the water down. So the water becomes superheated, past its boiling point. When it is disturbed, say by moving it or dropping something in it, the heat is released violently, erupting boiling water out of the cup.
To avoid this risk, heat water only the minimum amount of time needed. Or place a wooden spoon or stick in it.
brussels sprouts in microwave 

Microwave ovens cook food from the inside outside

Status: Myth
Although many people believe this to be the case, microwaves actually work on the outer layers of food, heating it by exciting the water molecules there. The inner parts of food are warmed as heat transfers from the outer layers inward. This is why a microwave can only cook a big hunk of meat to a depth of about one inch inward.

You can't heat oils in a microwave

Status: Fact
Oils such as olive oil do not heat well in microwaves because their molecules lack the polarity found in water. It's also true that frozen butter is hard to thaw in a microwave, because the bulk of the substance is oil, and the portion of water present is in the form of ice, which keeps the molecules locked up in crystal form, making oscillation more difficult.

Microwaves alter food in undesirable, possibly unsafe, ways

Status: Undetermined but unlikely
It's a fact of life that any type of cooking changes the chemistry of food. Cooking can reduce the levels of some nutrients, just as it can increase the levels of others or make them more or less available to the body for use. (Raw food anyone?)
The prevailing view is that microwaves do not alter foods in ways that are any more deleterious or harmful than other types of cooking. In fact, some have argued that the faster cooking time may actually preserve more nutrients versus other methods.
Still, we know sufficiently little about nutrition and the cumulative effects of food science so some people aren't convinced. E Magazine pointed out that popular holistic health expert Dr. Andrew Weil has written, "There may be dangers associated with microwaving food ... there is a question as to whether microwaving alters protein chemistry in ways that might be harmful."
The conclusion made by government agencies and mainstream organizations is that microwaved food is safe, as well as convenient. There are a limited number of studies that may suggest otherwise, but given the lack of large-scale or compelling evidence it's hard to feel that tossing out your microwave is a particularly smart step.
Everyone interviewed for this piece pointed to other issues as more pressing, from ubiquitous exposure to cell phones to more serious threats from radon or bigger energy users like heating and cooling. That doesn't mean microwaves aren't worth thinking about, however

Text and images via Yahoo Green

What lies beneath...

Whirlpool's concept TV microwave

Whirlpool's concept TV microwave
Every time something like this crops up you start hearing us talk "convergence" here on Engadget, but we rarely pinpoint exactly what we mean. Well, we'll tell you what we mean. We mean exactly the kind of convergence you see in Whirlpool's TV-microwave oven that makes it easier on yourself in combining your two laziest habits: idly watching TV while nuking leftover food. Where do we sign up? It better be online because we're not getting up to go to the freaking store, not for food, and not for devices to cook 'em.                 Text and image via Engadget

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