Tag Archives: microwave

Microwaving water really isn’t the same as heating it

Every time you make a cup of tea (or whatever hot beverage you may prefer), your cup becomes the stage of an interesting physics experiment. Even heating the liquid creates a pretty interesting mechanism. If you place a water-filled recipient on a stove, the bottom part starts to heat up. As it does, it becomes less dense, which makes it move to the top, and a cooler section of the liquid sinks to the source, where it heats up, moves up, and so on.

This process, called convection, ensures that there’s a uniform temperature throughout the water. But with microwave, it’s different.

Convection in a stove-heated recipient. Image credits: Bruce Blaus.

In a microwave, convection doesn’t take place because the heating comes from everywhere at the same time. Because the recipient itself also heats up, the hottest parts of the water rise to the surface and stay there, making the first sips much hotter than the ones at the bottom.

This helps to explain why, at least anecdotally, hot beverages just aren’t the same when you microwave or heat them with a conventional stove.

A team of researchers from the University of Electronic Science & Technology of China studied this common problem and found a way to trigger convection in microwave-heated cups as well.

The key, researchers say, is guiding the microwaves away from the surface of the liquid. They fitted a regular cup with custom-made silver plating that acts as a guide for the waves, reducing the field at the top and effectively blocking heating at the top, which creates a similar heating process to traditional approaches and results in a uniform temperature for the water.

“The experimental results show that when the modified glass cup with 7 cm metal coating is used to heat water in a microwave oven, the temperature difference between the upper and lower parts of the water is reduced from 7.8 °C to 0.5 °C.”

Naturally, placing metal plating inside a microwave oven seems like a bad idea and it almost always is — unless you really know what you’re doing. The team was able to design the metal plating in a way that’s both efficient and safe.

“After carefully designing the metal structure at the appropriate size, the metal edge, which is prone to ignition, is located at weak field strength, where it can completely avoid ignition, so it is still safe,” said Baoqing Zeng, one of the authors of the paper.

Zeng and colleagues are now working on ways to make the process scalable and cost-effective for brewing. They hope to commercialize their results soon — in which case, microwave tea could become a non-laughable option.

The team is also considering ways to do the same thing in heating solids, but the process is much more complex. For now, we’ll have to heat our leftovers the good old fashioned way.

Journal References: Multiphysics analysis for unusual heat convection in microwave heating liquid,” AIP Advances (2020). aip.scitation.org/doi/full/10.1063/5.0013295

Introduced in 1967, the Amana Radarange microwave oven would forever change the way American families prepare meals. Image: SMECC

How the microwave oven was made from WWII radar tech

Sometimes, weapons and other projects pushed by the urgency of war have been converted into civilian technology. Such is the case of nuclear power plants, the internet, but also radar tech, which inexpectedly and inadvertently led to the invention of the microwave oven — one of the most widely used home appliance in the world.

Radar and microwaves

Before and throughout the war, British ground radar technology was rather well matched by German scientific advances. Here, mid-war ground radar station FuMO 214 Würzburg-Riese [US National Archives]

Before and throughout the war, British ground radar technology was rather well matched by German scientific advances. Here, mid-war ground radar station FuMO 214 Würzburg-Riese. Credit: US National Archives.

 

In 1920, a young physicist called Albert Hull, who worked at the General Electric Research Laboratory in Schenectady, New York, invented the magnetron tube — a coaxial cylindrical anode and cathode with an axial magnetic field produced by an external coil. It was a magnet that controlled electrical current inside an evacuated electron tube, or vacuum tube. Hull believed the magnetron would be successful as an electrical converter, but 20 years later it would prove most useful in telecommunications. During WWII, the British were looking to devise a higher-frequency radar technology for the war effort. A radar locates distant objects by bouncing radio waves off of them and then analyzing the reflections. Locating the enemy from afar was crucial to the war effort.

Engineers planned to build a new radar system based on electromagnetic waves in the microwave region of the radio spectrum. Such a system would require smaller antennas and detect smaller objects than lower-frequency, longer-wavelength radars.  Microwaves correspond to a region in the EM spectrum defined by having wavelengths between approximately 1 meter and 1 millimeter, corresponding to frequencies between 300 MHz (Mega = 106 Hz = 106 sec-1) and 300 GHz (Giga = 109 Hz). Today, microwaves are often used to transmit data from satellites in space to radio dishes on Earth, but back then building a high-power source of microwave radiation proved to be a challenge.

In 1940, John Turton Randall and Harry Boot, two young physicists working in England at the University of Birmingham, found a way to modify Hull’s original magnetron tube to make it produce microwaves with high enough power. The improved design was called a cavity magnetron tube, and shortly after its first test runs it became the heart of the Allies’ advanced radar systems that were so essential — perhaps decisive — to the overall Allied victory in World War II.

From spotting Luftwaffe fighters to popcorn

During the war, one of the leading suppliers of cavity magnetron tubes was the Massachusetts-based Raytheon Manufacturing Company. Working there was a self-taught engineer by the name of Percy Spencer. One day, in 1946, while testing a new magnetron unit, Spencer felt a strange tingling sensation and suddenly noticed that the candy bar in his pocket had melted. He then placed popcorn, eggs, and other foods in front of the device and they all cooked — actually the egg exploded all over his friend’s face!

Shortly after the accidental discovery, engineers at Raytheon went to work on Spencer’s new idea, developing and refining it to be of practical use. A year later, the first commercial product hit the market. After a few decades of turmoil, myths and legends regarding microwave use, public demand began to swell with acceptance until the sales of microwave ovens eventually surpassed those of gas ranges in 1975. Furthermore, in 1976 the microwave became a more common household appliance than the dishwasher as it found its home in nearly fifty-two million U.S. households, or 60% of U.S. homes at the time.

Introduced in 1967, the Amana Radarange microwave oven would forever change the way American families prepare meals. Image: SMECC

Introduced in 1967, the Amana Radarange microwave oven would forever change the way American families prepare meals. Image: MECC.

Although microwave ovens today have advanced since the very first designs, at their core they still use the same cavity magnetron tube that was harnessed so effectively for WWII radar.

How a microwave oven works

Inside the Magnetron: Large magnets impose a field that causes the outward-flowing cloud to revolve (left). As it does, it forms spokes that pass each cavity between the plates (right). A passing spoke provides negative charge to the cavity, which then falls off until the next spoke arrives. The rise and fall creates an electromagnetic field in the cavities that oscillates at 2.45 gigahertz. Image: GEORGE RETSECK

Inside the Magnetron: Large magnets impose a field that causes the outward-flowing cloud to revolve (left). As it does, it forms spokes that pass each cavity between the plates (right). A passing spoke provides a negative charge to the cavity, which then falls off until the next spoke arrives. The rise and fall create an electromagnetic field in the cavities that oscillates at 2.45 gigahertz. Image: GEORGE RETSECK.

The microwave oven is quite a feat of physics and engineering. At its core, the oven exploits the polarity of water molecules which tend to rotate themselves into alignment with their positive ends in the direction of an electric field. With each rotation, the water molecule’s electrostatic potential energy is transferred into thermal energy. An analogy would be a very crowded room, in which everyone is told to turn and face the stage. In doing so, people brush up against one another as they turn and friction causes the conversion of some of their energy into thermal energy. The magnetron reverses its electric field very fast, so water molecules flip back and forth at a rate of billions of times per second.

Magnetron High voltage is sent to the cathode filament. After it heats up, it emits electrons that the positively charged anode plates attract. The attached antenna resonates at 2.45 gigahertz and emits microwaves from its tip--just like a radio-transmission antenna. Image: GEORGE RETSECK

Magnetron High voltage is sent to the cathode filament. After it heats up, it emits electrons that the positively charged anode plates attract. The attached antenna resonates at 2.45 gigahertz and emits microwaves from its tip–just like a radio-transmission antenna. Image: GEORGE RETSECK.

This heat is what actually cooks food in the oven. Because all particles in the food are vibrating and generating heat at the same time, food cooked in the microwave cooks much more swiftly than food cooked in a conventional oven where heat must slowly travel from the outside surface of the food inward. The same radio waves that cook your food pass harmlessly through plastics, glass, and ceramics. It is this characteristic that keeps plastic plates from melting and glasses from exploding. It is also this feature of microwaves that makes them so energy efficient; they heat only the food and nothing more.

As you might have learned from experience (ouch!), metals reflect microwaves which is why they line the walls of the microwave such that no waves escape and cook anyone in the kitchen!

Microwave oven.

Europe’s microwave ovens release as much CO2 as 6.8 million cars

Microwave ovens could be one of the EU’s largest polluters, new research has found.

Microwave oven.

Image credits peapod labs / Flickr.

Researchers at the University of Manchester say that microwave ovens have a much darker side than you’d first believe — these little appliances account for CO2 emissions comparable to those of nearly seven million cars, in the EU alone. The team carried out the first-ever comprehensive study of the environmental impact of microwaves from “cradle to grave”.

The study relied on life cycle assessment (LCA), a technique used to assess the environmental impacts of a product, summed up over all the stages of its life from raw material extraction to disposal or recycling. All in all, the team looked at 12 different factors which play into a commodity’s environmental impact, including ecological toxicity, depletion of natural resources, and contribution to climate change. Some highlights of their results include:

  • Microwaves emit 7.7 million tonnes of carbon dioxide per year in the EU — equivalent to the annual emissions of 6.8 million cars.
  • Microwaves across the EU consume an estimated 9.4 terawatts per hour (TWh) of electricity every year — roughly the amount generated by three large gas power plants.

The main environmental impacts identified by the researchers are raw material exraction and processing, the manufacturing process for the ovens, and end-of-life waste management. Manufacturing alone, the team reports, accounts for more than 20% of the total impact in the natural resource depletion and contribution to climate change brackets.

However, electricity consumption has the single largest impact on the environment among all the factors analyzed in the study. This included all energy used in the ovens’ life cycle, from fuels used in manufacturing to energy generation in power plants. All in all, the EU’s microwave ovens consume an estimated 9.4 TWh of electricity per year. Your average oven will thus burn through roughly 573-kilowatt-hour (kWh) of electricity over an eight-year lifetime. The team notes that this is equivalent to an LED turned on for almost nine years straight, despite the fact that microwave ovens spend 90% of their lifetime in idle, standby mode.

Disposable ovens

Electrical and electronic waste.

Electrical and electronic waste.
Image credits far closer / Flickr.

Another source of environmental damage stems from consumer habits in regards to the devices. In 2005, the EU as a whole generated 184,000 tones of electrical and electronic (EE) waste solely from discarded microwaves. By 2025, this quantity is estimated to reach 195,000 tonnes — roughly 16 million units thrown away in a single year.

“Rapid technological developments and falling prices are driving the purchase of electrical and electronic appliances in Europe,” says lead author Dr Alejandro Gallego-Schmid. “Consumers now tend to buy new appliances before the existing ones reach the end of their useful life as electronic goods have become fashionable and ‘status’ items.”

“As a result, discarded electrical equipment, such as microwaves, is one of the fastest growing waste streams worldwide.”

Overall, the lifespan of these ovens has dropped by nearly 7 years in the past two decades, the team adds, going from around 10 to 15 years in the late 90s to around 6 to 8 years today. Shorter lifespans have helped to increase the amount of EE generated from microwave ovens.

The authors show that existing regulation is not sufficient to address the environmental impact of these devices, and believe we’ll have to develop specific regulation targeting their design. Such measures should aim to reduce the quantity of resources that go into making the ovens, and recycling as much as possible from them at the end of their life cycle.

Efforts to reduce consumption should focus on improving consumer awareness and on teaching them to use these appliances more efficiently. For example, electricity consumption can be reduced by adjusting the time of cooking to each type of food.

“Given that microwaves account for the largest percentage of sales of all type of ovens in the EU, it is increasingly important to start addressing their impact on resource use and end-of-life waste”, Gallego-Schmid explains.

The paper “Environmental assessment of microwaves and the effect of European energy efficiency and waste management legislation” has been published in the journal Science of The Total Environment.

sponge-bob2

Kitchen sponges are hotspots for bacteria. Sanitizing methods like microwaving don’t seem to work

sponge-bob2

Microbes love wet environments. They also enjoy food — any kind of nutrients will do since they’re not picky at all. This makes kitchen sponges, which stay wet for most of the time and are packed with leftover scraps, excellent breeding grounds for bacteria. This can turn into a serious health hazard seeing how sponges are supposed to clean the dishes and cutlery that we use to eat. Some studies have suggested that households can reduce the risk of hazardous bacterial infections by sanitizing kitchen sponges.

Some studies have suggested that households can reduce the risk of hazardous bacterial infections by sanitizing kitchen sponges. A new study suggests that these methods aren’t really effective — not even microwaving. Instead, households should turn to cheap sponges that they should replace weekly.

Few places, if any, in our home have more bacterial density then the kitchen sponge

German researchers at the Furtwangen University studied 14 used kitchen sponges separated into top and bottom parts. In total, across all household sponges, the scientists found these yielded 362 operational taxonomic units (OTUs), which are pragmatic proxies for bacterial ‘species’.

After sequencing the cultured bacteria, the researchers ended up with 220,000 raw DNA sequences representing  9 phyla, 17 classes, 35 orders, 73 families, and 118 genera of microbes, as reported by Ars Technica. The most prominent bacteria belonged to the Moraxellaceae family. These are typically found on the human skin and previous studies identified them on virtually every kitchen surface that people typically clean using sponges, from fridges to stoves. These are also the same ‘stinky’ bacteria that make dirty laundry smell bad.

Other notable bacterial species were those belonging to the Proteobacteria, Bacteroidetes, and Actinobacteria phyla. Some of these have been previously identified with moderate diseases.

(A) Kitchen sponges, due to their porous nature (evident under the binocular (B) and water- soaking capacity, represent ideal incubators for microorganisms. Scale bar (B): 1 mm. Credit: Scientifi Reports.

(A) Kitchen sponges, due to their porous nature (evident under the binocular (B) and water- soaking capacity, represent ideal incubators for microorganisms. Scale bar (B): 1 mm. Credit: Scientifi Reports.

In terms of raw numbers, kitchen sponges are teeming with bacteria. The team led by Markus Egert found bacterial densities as high as  5.4 x 1010 or 54 billion-bacterial cells per cubic centimeter of uncleaned kitchen sponge.

“Kitchen sponges are likely to collect, incubate and spread bacteria from and back onto kitchen surfaces, from where they might eventually find their way into the human body, e.g. via the human hands or contaminated food. In addition, direct contact of a sponge with food and/or the human hands might transfer bacteria in and onto the human body, where they might cause infections, depending on their pathogenic potential and the environmental conditions,” the authors wrote in a paper published in Scientific Reports.

Previously, researchers found sanitation through boiling or microwave treatment can significantly reduce the bacterial load of kitchen sponges. Naturally, people regarded the news as a reasonable hygiene measure, which we also covered in detail in the past. Egert argues, however, that these lab studies do not accurately reflect real use. The few sponges that he and colleagues collected from sponge owners who microwaved or hot-soaped them “did not contain fewer bacteria than uncleaned ones.”

Moreover, the bacterial species from the ‘sanitized’ sponges contained more bacteria related to diseases. That may be due to the fact the surviving bacteria are stronger and once they recolonized the sponge, the whole population was more resistant.

“This effect resembles the effect of an antibiotic therapy on the gut microbiota and might promote the establishment of higher shares of RG2-related species in the kitchen sponges. Although further analyses, including controlled sanitation experiments, are needed to substantiate these findings, our data allow careful speculation that a prolonged application of sanitation measures of kitchen sponges is not advisable,” the authors noted.

The paper highlights the fact that used kitchen sponges contain more bacteria than previously thought. It also shows that the “long term perspective, sponge sanitation methods appear not sufficient to effectively reduce the bacterial load in kitchen sponges.” What Egert and colleagues advise instead is to regularly replace kitchen sponges, preferably weekly.

Why you should microwave your sponges, according to science

The best way to keep your sponges clean is to microwave them. We’ll show you why you should do this, and how to do it.

Why microwave sponges

A 2006 study found that kitchen sponges, scrubbing pads, and syringes were easily cleaned of 99 to 100% of all bacteria through simple microwave radiation for only a couple of minutes.

“Basically, what we found is that we could knock out most bacteria in two minutes,” said researcher Gabriel Bitton, professor of environmental engineering at the University of Florida. “People often put their sponges and scrubbers in the dishwasher, but if they really want to decontaminate them and not just clean them, they should use the microwave.”

Kitchen sponges are often in contact with greasy organic matter, and they can get dirty really easily. You’d think that the detergent and cleaning products actually kill the germs, but they really don’t. The odds are kitchen sponges are actually full of germs. In fact, Prof. Charles P. Gerba, a microbiologist, agrees. He writes that sponges are some of the best places in the kitchen for germs, providing a damp and nurturing environment for many different bacteria.

Now, there’s no reason to panic because that’s not the most dangerous thing in the world, but if you want to ensure the cleanliness of your sponges – you should microwave them. According to the study’s results, the total bacterial count was “reduced by more that 99 percent within 1 to 2 minutes, and the sum of coliform and E. coli were totally inactivated after 30 seconds of microwave radiation.” A few more resistant spores lasted up to 4 minutes, and after 10 minutes, there were simply no surviving bacteria in the sponge.

How to microwave your sponge

Odds are, first few times you’ll be doing this you’ll feel silly, but you really shouldn’t.

The process itself is simple and fast, but there are a few basic precautions you should take:

[panel style=”panel-success” title=”Basic precautions” footer=””]- Make sure there’s nothing metallic in your sponge! This can completely ruin the microwave
– Insert the sponge wet, not dry. If it’s dry, it can melt or even catch fire.
– Two minutes kills 99.9% of all bacteria, 10 minutes is overkill and you risk melting the sponge.
– Let the sponge cool off a bit after microwaving it.[/panel]

Other than that, the process is pretty straightforward – you just microwave the sponge. There’s no rule for how often you should do this, but Bitton (the author of the study) says that once a day should be OK.

Alternatives

Kitchen sponges can get dirty and nasty.

There are other alternatives to ensure the cleanliness of your sponges. You could boil them, but that’s neither time nor energy efficient. You can also try to soak them in bleach or vinegar, which is also extremely effective at killing germs, but you need to constantly buy bleach or vinegar. All in all, microwaving is the easiest, fastest and cheapest way to keep your sponges clean.

If you don’t want to do either of the above, you can at least try to clean your sponge after washing the dishes. Then, make sure you dry it and squeeze out as much moisture as possible, and leave it on the sink, not in the sink.

Also, no matter what to do, sponges have to be changed regularly. Otherwise, no matter how hard you try to clean them, they’ll simply get dirty again and lose their qualities.

NASA confirms “Impossible” propellant-free microwave thruster works

Designs for a device called a “microwave thruster” were proposed in 2006. While the device was physically sound and followed the principles of relativity, it has been dismissed by researchers who claimed that such a functioning device would defy the law of conservation of momentum. A team from NASA set out to trial the device and see if it works; lo and behold – it did!

Several years ago British scientist Roger Shawyer presented his EmDrive microwave thruster as an alternative to powering spacecrafts without propellant. Instead, it uses microwaves bouncing off a carefully tuned set of reflectors to achieve small amounts of force and therefore achieve propellant free thrust. Initially, the device seemed theoretically flawed; apparently, it defies the law of conservation of momentum, which states that: In a closed system (one that does not exchange any matter with the outside and is not acted on by outside forces) the total momentum is constant. Basically, if you consider a collision between two objects the forces acting between the two objects are equal in magnitude and opposite in direction. In other words, in order to push something forward, you need to push something backward. No propellant to push backwards, no forward propulsion; the device was deemed flawed, inoperable, and dismissed.

But in 2012, a team of Chinese researchers set out to test the thruster, successfully replicating Shawyer’s project step by step. Not much was published around that, and Western scientists still dismissed it. It took two years for someone to pay attention to this – and it was NASA. The thruster that NASA buikt produced 30 to 50 micronewtons of thrust, which was considerably less than the Chinese team’s reported 720 millinewtons or Shawyer’s 16 to 30 millinewtons, but the principle is the same. As they write in their report, they’re not entirely sure how or why… but it works!

“Test results indicate that the RF resonant cavity thruster design, which is unique as an electric propulsion device, is producing a force that is not attributable to any classical electromagnetic phenomenon and therefore is potentially demonstrating an interaction with the quantum vacuum virtual plasma.” I believe that translates as, “We are not entirely sure why, but it works.”

The new engine could propel space ships using microwaves instead of fuel.

The implications are incredible, and impossible to grasp at the moment – so for now, NASA chose to focus on the results, and not the method. The implications for long term space travel are amazing; we could forego the need to carry vast amounts of fuel, and instead use solar energy to generate the power to create the microwaves in the first place, meaning that the engine could run indefinitely, as long as it has access to solar energy (or any other star’s energy, if we think in the really big picture). For now however, NASA’s engine couldn’t even propel a peanut through space, but scaling shouldn’t be that much of a problem – as long as they understand why the heck it works!

Could we be dealing with a paradigm shift? Could we be reaching the new stage in space exploration? Like NASA, I have no idea

This five-cell metamaterial converts stray microwave energy, as from a WiFi hub, into more than 7 volts of electricity with an efficiency of 36.8 percent—comparable to a solar cell. (c) Duke University

Microwave harvester converts wireless energy into direct current with solar cell-like efficiency

This five-cell metamaterial converts stray microwave energy, as from a WiFi hub, into more than 7 volts of electricity with an efficiency of 36.8 percent—comparable to a solar cell. (c) Duke University

This five-cell metamaterial converts stray microwave energy, as from a WiFi hub, into more than 7 volts of electricity with an efficiency of 36.8 percent—comparable to a solar cell. (c) Duke University

Using a range of cheap materials arranged in a specific manner, researchers at Duke University have demonstrated a device that captures microwave signals, such as those relayed by WiFi or even satellites high up above in Earth’s orbit, an converts this free, lost energy into electrical current. The harvesting and conversion efficiency of the device is on par with currently photo-voltaic solar panels. In the future, such circuits could be used to always wirelessly power your phone when it’s not in use or charge a battery in your home.

It’s enough to open  your notebook just about anywhere downtown in a developed city to spot tens and tens of public WiFi hotspots. There are maybe tens of thousands of WiFi networks in a developed city, and all of these waste energy by constantly relaying microwave signals. The same applies to satellites, sound signals and other sources. What if you could harvest and cut the waste a bit?

This is what the Duke team of engineers, comprised of undergraduate engineering student Allen Hawkes, working with graduate student Alexander Katko and lead investigator Steven Cummer, set out to do. Using simple materials like five fiberglass and copper energy conductors wired together on a circuit board  to form a five-cell metamaterial array. The resulting device harnesses microwave energy and converts it into direct current 7.3V electricity. For reference, your  Universal Serial Bus (USB)  charges small electronic devices with 5V, so a system coupled with the Duke metamaterial circuit could provide free charging for your mobile devices.

“We were aiming for the highest energy efficiency we could achieve,” said Hawkes. “We had been getting energy efficiency around 6 to 10 percent, but with this design we were able to dramatically improve energy conversion to 37 percent, which is comparable to what is achieved in solar cells.”

“It’s possible to use this design for a lot of different frequencies and types of energy, including vibration and sound energy harvesting,” Katko said. “Until now, a lot of work with metamaterials has been theoretical. We are showing that with a little work, these materials can be useful for consumer applications.”

Microwave harvester

Another application could be to improve the energy efficiency of appliances by wirelessly recovering power that is now lost during use.

“The properties of metamaterials allow for design flexibility not possible with ordinary devices like antennas,” said Katko. “When traditional antennas are close to each other in space they talk to each other and interfere with each other’s operation. The design process used to create our metamaterial array takes these effects into account, allowing the cells to work together.”

A metamaterial coating could be applied to the ceiling of your living room, for instance, to harvest free energy from microwaves that litter space all around us. A more interesting, and maybe more practical, application might be coating smartphones with a thin layer of mematerial directly, so your phone charges constantly with significant benefits for your battery life. It’s unclear though how much voltage a thin and small surface metamaterial circuit might provide.

“Our work demonstrates a simple and inexpensive approach to electromagnetic power harvesting,” said Cummer.  “The beauty of the design is that the basic building blocks are self-contained and additive. One can simply assemble more blocks to increase the scavenged power.”

In remote locations, like in the desert or the middle of the wilderness, a series of power-harvesting blocks could be assembled to capture the signal from a known set of satellites passing overhead. The generated power would be far from impressive, of course, but it might still be enough to power a small array of sensors, the researchers believe.

Their device and findings were reported in the journal Applied Physics Letters

 

Universe may be curved, not flat

It is currently believed that we live in a lopsided Universe: cosmologists reached this conclusion by examining the detailed structure of the left over radiation from the Big Bang. Now, two cosmologists presented data which seems to suggest that our Universe is actually curved slightly, in a saddle-like fashion; if correct, their model would invalidate the long standing idea that the cosmos is flat.

universe curved

Cosmic microwave background (CMB) is the thermal radiation left over from the “Big Bang” of cosmology. It is fundamentally important for measurements, because it is the oldest light in the universe, dating to what is called the epoch of recombination (the period during which charged electrons and protons first became bound to form electrically neutral hydrogen atoms – so REALLY early). NASA’s Wilkinson Microwave Anisotropy Probe provided the first hints of an Universal asymmetry in 2004, but some believed that was a technological error, and hoped that NASA probe’s successor, the European Space Agency’s Planck spacecraft would fix that error. But as it turns out, the Planck spacecraft confirmed the anomaly.

To explain those results, Andrew Liddle and Marina Cortês, both at the University of Edinburgh, UK, have taken on the gargantuan task of proposing a new model of cosmic inflation – a theoretized period in which the Universe expanded dramatically, growing by a few orders of magnitude in a fraction of a second.

In their paper, published this week in Physical Review Letters, Liddle and Cortês toy with the idea that aside from the initial quantum field (the inflation), there was also a secondary quantum field which caused the curvation of the Universe. The authors’ work is the first to explain the lopsidedness from first principles.

However, the problem is that numerous different measurements suggest that the Universe is flat, some of which can’t be fully explained with this new, curved model. Future improved measurements will likely show which hypothesis is right.

Scientific source: Nature doi:10.1038/nature.2013.13776

Via Nature.

Microwaves can be seen being blocked and scattered without (l), and "reconstructed" (r) with the cloak

Scientists cloak 3D object in microwave spectrum

The much dreamed off invisibility cloak is just a few tiny steps away, after remarkable research in the field, many backed by military interests, have sparked some amazing advances. In the last few years alone, scientists have managed to successfully cloak various objects either using meta-materials that bent light around an object to conceal it or electrically stimulated nanotubes which cause the human eye to perceive a mirage-like effect and thus conceal the object. Just a few weeks ago, scientists manage to hide an event in time after they developed a time cloak.

Microwaves can be seen being blocked and scattered without (l), and "reconstructed" (r) with the cloak

Microwaves can be seen being blocked and scattered without (l), and "reconstructed" (r) with the cloak

However, we’re still in a highly incipient state as far as a full-on invisibility cloak in its all rightful manner is concerned. You see, these devices are only capable of rending a particular object only in 2D, from a particular angle, which although doesn’t seem particularly useful, it’s still been a remarkable progress. Now, in a recently published paper, University of Texas scientists describe how they’ve been able to use plasmonic meta-materials to make an 18-inch cylindrical tube invisible – a full 3-D cloak.

What we actually perceive with our eyes is actually information transmitted by light which bounces off objects in our surroundings, as its constituent atoms absorb, transmit or reflect electric and magnetic fields. One might say that the world around us, as we visually see it, is not the real one, but its reflection. Bearing in mind this, if one can manipulate or stop light from bouncing off an object altogether, than that object would become invisible.

” That means the object is invisible, from any angle of observation.

“This object’s invisibility is independent of where the observer is,” Professor Andrea Alu, the study’s co-author, tells Danger Room. “So you’d walk right around it, and never see it.”

Plasmonic materials can be designed to have effects on the fields that are precisely opposed to those of the object, and thus cancel out the light scattering from an object. When the plasmonic shell was coated on a cylinder, the two cancelled each other out, and became invisible in the high-frequency wavelengths, like the microwave spectrum – it remained perceivable as always in the visual wavelength spectrum, however.

The plasmonic material shell is, in essence, a photo-negative of the object being cloaked, so for this to work the shell needs to be tailored specifically for the object to be cloaked. Cloaking in visible light, hiding more complex shapes and materials, is still extremely distant, however these recent advances, with this latest one to bolster as well, proves that it’s far from being impossible.

“We have some ideas to make it work,” Alu says. “But the human eye is not our priority. Right now, we’re focused on improving biomedical imaging.”

 

The study was presented in a recent edition of the New Journal of Physics.

The science behind crop circles

Crop circles have always been an important weapon in any conspiracy theorist’s arsenal, certain to be mentioned alongside UFOs, green aliens or reptilians. Since 1970, tens of thousands of crop circles have been reported around the world, most amateur hoaxes, while some are so intricately built that they even baffle scientists.

In this month’s edition of Physics World, Richard Taylor, director of the Materials Science Institute at the University of Oregon, takes a new look at the mysterious crop circle phenomenon, detailing a bit in his piece how science applies to them. He notes how physics and the arts are coming together to produce more impressive and spectacular crop-circle patterns that still manage to maintain their mystery.

“Crop-circle artists are not going to give up their secrets easily,” Taylor wrote.

“This summer, unknown artists will venture into the countryside close to your homes and carry out their craft, safe in the knowledge that they are continuing the legacy of the most science-oriented art movement in history.”

While it’s unanimously recognized that crop circles are man-made objects, and not UFO formations, some are so incredibly complex and precise, all cut out in an extremely short time, that they still baffle scientists as to how the artists actually managed them. Some of today’s designs are so complex, with some featuring up to 2000 different shapes, that there has to be more going into their production than just boards.

In the past, crop circle enthusiasts would use ropes, boards and even bar stools to form the deceiving patterns, however with the advancement in technology along the year the tools of trade have greatly diversified. Modern crop circle are now precisely drawn to the most complex shape using GPS plotting, lasers and microwaves.

Taylor suggests that microwaves could be used to make crop stalks fall over and cool in a horizontal position – a technique that could explain the speed and efficiency of the artists and the incredible detail in the patterns. In previous experiments, researchers were able to exactly replicate some of the complex crop-circles from around the world using a simple handheld magnetron, readily available from microwave ovens, and using a 12-volt battery.

Matin Durrani, Editor of Physics World, says, “It may seem odd for a physicist such as Taylor to be studying crop circles, but then he is merely trying to act like any good scientist – examining the evidence for the design and construction of crop circles without getting carried away by the side-show of UFOs, hoaxes and aliens