"The Wow! signal recorded on August 15, 1977. The ones, twos and threes indicate weak background noise. Letters, especially those closer to the end of the alphabet, represent stronger signals. The ""6EQUJ5"" is read from top to bottom (see graph below) and shows the signal rising from ""6"" to ""U"" before dropping back down to ""5"". Credit: Big Ear Radio Observatory and North American AstroPhysical Observatory (NAAPO)"