There’s nothing physically blocking the atoms from flying right through the channel– in fact, an atom that enters the channel will always exit the other side without slowing down along the way. This is termed “ballistic,” a term that will always have a special place in my heart thanks to an incident at my Ph.D. defense.
Daily Archives: September 14, 2012
After This We Hypnotize the Drops
Acoustic Levitation of Liquids Looks Like Magic
No magic show: Real-world levitation to inspire better pharmaceuticals
The acoustic levitator uses two small speakers to generate sound waves at frequencies slightly above the audible range – roughly 22 kilohertz. When the top and bottom speakers are precisely aligned, they create two sets of sound waves that perfectly interfere with each other, setting up a phenomenon known as a standing wave.
The speed of sound is about 340 m/s, so a 22 kHz wave has a wavelength of about 1.5 cm; the nodes would thus be half that distance apart, but you wouldn’t have to fill every node. Notice the effect at 0:30, where the standing wave is adjusted — you can see the drops move up and down, in tandem.
This seems to be analogous to a dipole force trap in atomic physics. If that’s so, you’d have a radial pressure gradient also giving confinement, which might account for the somewhat strange look to the speakers.
A Robot Called Horse
This video depicts field testing of the DARPA Legged Squad Support System (LS3). The goal of the LS3 program is to demonstrate that a legged robot can unburden dismounted squad members by carrying their gear, autonomously following them through rugged terrain, and interpreting verbal and visual commands.