Sound waves put levitation on the move

Scientists have known for years how to use sound waves to hoist particles in the air, a process known as acoustic levitation. But moving the lifted bits around was more challenging. The sound waves tend to trap a levitated object in a fixed pocket of space.

The new technique moves the pockets around by deforming a field of sound waves, letting researchers transport trapped objects several centimeters

There’s a cool slow-motion video of a small blob of sodium and a drop of water being moved together and reacting when they touch. Presumably much easier to film when you know where the low-speed collision is going to take place.

Why Are Human Powered Helicopters So Big?

Rhett has the breakdown, but if you want the basic idea, here it is: helicopter thrust requires throwing air down with a certain momentum (mv), but less air moved quickly requires more energy than lots of air moved slowly, and since this is human-powered, you opt for the almost-surreal, slowly moving, huge rotors.

Great video about how transistors work.

A transistor is based on semiconductor material, usually silicon, which is ‘doped’ with impurities to carefully change its electrical properties. These n and p-type semiconductors are then put together in different configurations to achieve a desired electrical result. And in the case of the transistor, this is to make a tiny electrical switch. These switches are then connected together to perform computations, store information, and basically make everything electrical work intelligently.

[T]hree years of the sun at a pace of two images per day.
SDO’s Atmospheric Imaging Assembly (AIA) captures a shot of the sun every 12 seconds in 10 different wavelengths. The images shown here are based on a wavelength of 171 Angstroms, which is in the extreme ultraviolet range and shows solar material at around 600,000 Kelvin. In this wavelength it is easy to see the sun’s 25-day rotation as well as how solar activity has increased over three years.

During the course of the video, the sun subtly increases and decreases in apparent size. This is because the distance between the SDO spacecraft and the sun varies over time. The image is, however, remarkably consistent and stable despite the fact that SDO orbits the Earth at 6,876 miles per hour and the Earth orbits the sun at 67,062 miles per hour.

Self-siphoning beads is more mesmerizing in slow-motion

The “cornering ability” of the beads seems to depend on the tension. Makes for an interesting effect.

MIT video (embedding is disabled) doing the famous “monkey drop”experiment — a monkey in a tree drops when a shot is fired. Because the bullet and the monkey both accelerate at g, you should aim straight at the monkey. I remember doing this in the basement of my neighbor’s house, with a blow-gun and a solenoid dropping a metal target.