Some music science to start: Billboard has revamped its “Hot 100” formula, which will now count YouTube plays as a measure of popularity. This means, naturally, that Baauer’s “Harlem Shake” — the soundtrack to the mistitled dance craze sweeping the Internet — catapults to No. 1 on this week’s chart. (The Verge has an interesting breakdown of the financial maneuvering behind “Harlem Shake”; read this New York Times piece for some thoughts on “Harlem Shake,” “Thrift Shop,” rapper turned nuisance Azealia Banks and hip-hop authenticity.) “Thrift Shop” falls to No. 2; Rihanna’s “Stay” (co-signed by Vin Diesel); Will.i.am and Britney Spears’s “Scream and Shout”; and Taylor Swift’s “I Knew You Were Trouble” round out the new top five. In conclusion, expect many more over-the-top videos from your favorite musicians in the near future. It’s a “Gangnam Style” world out there.