Toothpick Surfing on Acoustic Waves and Other Levitation Implications

https://www.ethlife.ethz.ch/archive_articles/130716_schallwellenreiten_aj/index_EN

Toothpick Surfing on Acoustic Waves

Acoustic waves have allowed for many more objects and liquids to be levitated in mid-air than ever before. Such feats are usually performed with magnets, but the objects floating on the magnets needed to have magnetic properties. ETH, a group of researchers in Zurich, successfully levitated a toothpick in mid-air and controlled its movements using acoustic waves. With the same technique they also merged droplets of liquid.

The postdoctoral researcher involved in this study at the Swiss Federal Institute of Technology is Daniele Foresti. Foresti made it possible for any object, regardless of its properties, (except maybe weight which is still at the experimental stage) to levitate in mid-air through the use of acoustic waves. This allows for the study of some chemical reactions involving processes that would otherwise be compromised with the contact of a surface.

Levitation via acoustic waves allows for a vast number of objects and liquids to be experimented on. The current methods we have that allow objects to reach a levitated state are magnetic levitation, electrical fields, and suspension in liquids with the help of buoyancy. The problem with magnets is the difficulty of controlling the movement of liquids. The liquids are required to have some sort of magnetic properties. Floating liquids in another liquid requires the use of immiscible liquids (not forming a homogeneous mixture when added together) such as oil and water. Acoustic waves take care of these limitations. The only limitation is the maximum diameter of the object being levitated. It has to correspond with half the acoustic wavelength being used. Levitation is achieved when all of the acting forces (gravity and acoustic waves) reach equilibrium. The force of the acoustic waves counteracts the force of gravity, which allows this state to occur.

Making Coffee on Acoustic Waves

The scientific term used to describe this phenomenon is the acoustic radiation pressure effect. This is not a new discovery, rather an alteration to a previous one that goes back to the findings of Rayleigh. However, unlike in previous studies, we can now control movement with acoustic waves. This was done by putting together multiple modules that create the acoustic waves and by switching them on to vary their wave action. This varying process is how liquid is able to move from one module to the next. Foresti used this method to merge a water droplet and a bit of instant coffee together to form coffee!

 

Sources:

https://www.ethlife.ethz.ch/index/index_EN

https://www.ethlife.ethz.ch/archive_articles/130716_schallwellenreiten_aj/index_EN

http://en.wikipedia.org/wiki/Magnetic_levitation

http://en.wikipedia.org/wiki/Acoustic_radiation_pressure

http://www.nobelprize.org/nobel_prizes/physics/laureates/1904/strutt-bio.html

The Power of Wind Farms

Yesterday, my day both began and ended with the California sun moving through a horizon speckled with wind turbines. As humans we have only to thank Sol for our existence. We’ve come a long way in terms of mechanized energy efficiency. Seeing these two great power sources together lead me to wonder: How much power do we get from wind farms? How much power does one wind turbine produce?

To understand the energy intake of wind turbines we should take a closer look as to what is actually happening inside to harness this electricity. An anemometer gauges the speed and the direction of the wind. The wind speed information is then passed through to a controller. This device turns the turbines on, points the turbine’s blades in the most fortuitous direction, and when the wind speed is too high (over 55 mph) or too low (under 8-16 depending) it adjusts accordingly.

The turbine blades are directly connected to an electrical generator which creates electricity. A simple generator does this by spinning a magnet inside of copper wiring. The generators used in wind turbines are obviously more sophisticated though they have the same effect.

So how much electricity can one wind turbine create? Wind Energy America states that

Typically modern turbines range in size from 660 kilowatts to over 3 megawatts of capacity. They are placed in fairly windy locations with minimum wind speeds in the range of six meters per second (around 13 miles per hour). Wind turbines generally run at 30 to 40 percent capacity, so a 1 MW turbine could produce around 3 million KWh of electricity in a year.

The amount of wind in an area plays a huge role in how much energy is produced. So if you’re in a windy part of the country it is time to ask yourself: Is this a viable option for me?

Sources:

Inside a Wind Turbine

Wind Energy America FAQs

Simple Generator

Absolute Zero No Longer Absolute

Absolute zero, measured using the Kelvin scale, occurs when matter has reached the lowest possible level of entropy, when its atoms are utterly and totally ‘frozen.’ It is the coldest temperature anything in the universe can possibly reach, or so we thought.

Physicists at the Ludwig Maximilian University in Munich, Germany have done the impossible; they have created a quantum gas made up of potassium atoms that is colder than absolute zero.

Using lasers and magnetic fields, the infantile toys of researchers studying the quantum realm, the physicists were able to stabilize the atoms in a lattice arrangement. While the atoms normally repel each other at positive temperatures, the researchers decided to have some fun and abruptly alter the magnetic fields, causing all of the atoms to instantly attract. Ulrich Schneider, part of the team of physicists, explains that

This suddenly shifts the atoms from their most stable, lowest-energy state to the highest possible energy state, before they can react. It’s like walking through a valley, then instantly finding yourself on the mountain peak.

Whoa.  In the quantum world, anything goes.

Now, at a positive temperature, attraction between all of the atoms would cause the gas to become unstable and collapse in on itself, ultimately producing contempt and self loathing in already sensitive quantum physicists   Luckily, as usual for physicists, they protected the delicate balance of their emotions with trapping lasers, which were used to hold the atoms in place.  Boom! The result is:

The gas’s transition from just above absolute zero to a few billionths of a Kelvin below absolute zero.

Working with negative temperatures opens up all new realms of possibilities in the laboratory. Wolfgang Ketterle, a man with a better name than you, as well as a physicist and Nobel laureate at the Massachusetts Institute of Technology in Cambridge, reveals to us the profundity of this feat. He says that doing quantum experimentation while working with negative temperatures is like experimenting in an environment where:

you can stand a pyramid on its head and not worry about it toppling over. This may be a way to create new forms of matter in the laboratory.

By far, the weirdest part about the negative temperature gas is that it behaves identically to dark energy, the force that pushes the Universe to expand at an exponential rate despite the ever persistent pull of gravity.  The atoms in the gas also seem to want to collapse inward, but the negative temperature holds them in place.  Schneider remarks that:

It’s interesting that this weird feature pops up in the Universe and also in the lab.  This may be something that cosmologists should look at more closely.

Researchers believe negative temperatures will give rise to the creation of matter with anti-gravitational properties, rising, despite gravity throwing a temper tantrum over wanting it to fall. For all you Egyptian pyramid conspiracy theorists out there, here’s some extra fodder for the anti-gravity theories.  The Egyptians must have created negative kelvin temperatures first!

 

Sources:

http://en.wikipedia.org/wiki/Absolute_zero

http://www.sciencemag.org/content/339/6115/52