Fears that malevolent aliens will tune into this week's broadcast of The Beatles' song "Across the Universe" have been voiced by scientists. Nasa started to beam the song towards the North Star, 431 light years from Earth at midnight GMT on Monday, drawing congratulations from former Beatle Sir Paul McCartney and John Lennon's widow, Yoko Ono, who mused that it marked "the beginning of the new age in which we will communicate with billions of planets across the universe." The transmission raises questions about what we would want aliens to learn about our world But today's New Scientist asks whether such signals could expose us to the risk of attack from mean spirited aliens. Scientists considered this question at the "Sound of Silence" meeting at Arizona State University in Tempe this week. "Before sending out even symbolic messages, we need an open discussion about the potential risks," says Douglas Vakoch of the Seti (Search for ExtraTerrestrial Intelligence) Institute, Mountain View, California.