Build a Levitating Disco Ball

Electromagnetism, feedback, and the power of disco keep things aloft

5 min read
Build a Levitating Disco Ball
Photo: W. Wayt Gibbs

Video: W. Wayt Gibbs

In 1979, when I was 11 and enthralled by Star Wars, magnetism held a special appeal. It was the closest thing in the real world to “the Force.” So for our fifth-grade science project, a friend and I wrapped my dad’s iron chisel with wire to make an electromagnet. When connected to a lantern battery, it grabbed, repulsed, and spun bar magnets like magic. But when we got curious and plugged it into a wall socket, the resulting pop and puff of smoke produced an unforgettable jolt.

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From WinZips to Cat GIFs, Jacob Ziv’s Algorithms Have Powered Decades of Compression

The lossless-compression pioneer received the 2021 IEEE Medal of Honor

11 min read
Photo of Jacob Ziv
Photo: Rami Shlush

Lossless data compression seems a bit like a magic trick. Its cousin, lossy compression, is easier to comprehend. Lossy algorithms are used to get music into the popular MP3 format and turn a digital image into a standard JPEG file. They do this by selectively removing bits, taking what scientists know about the way we see and hear to determine which bits we'd least miss. But no one can make the case that the resulting file is a perfect replica of the original.

Not so with lossless data compression. Bits do disappear, making the data file dramatically smaller and thus easier to store and transmit. The important difference is that the bits reappear on command. It's as if the bits are rabbits in a magician's act, disappearing and then reappearing from inside a hat at the wave of a wand.

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