The Feynman Lectures is one of the most popular lecture series in physics. It’s a great resource for science enthusiasts, students, and teachers, and each lecture is just fantastic in general. Now, Caltech and The Feynman Lectures website have collaborated to put these lectures online completely free of cost.
The lectures themselves were first presented at Caltech in the 1960s by the legendary physicist Richard Feynman. The lectures have since been combined into a three-volume book. To date, about 1.5 million English copies have been sold, but now that it’s free, that number will probably stagnate.
This is also how the smartphone app Shazam can recognize a song. It splits the music into chunks, then uses Fourier’s trick to figure out the ingredient notes that make up each chunk. It then searches a database to see if this “fingerprint” of notes matches that of a song they have on file. Speech recognition uses the same Fourier-fingerprinting idea to compare the notes in your speech to that of a known list of words.