Decoding an Interstellar Message Did you manage to "decode" the message to the right? If not, here is the solution. BLUE: The binary numbers. On the top left the numbers 0 to 9 working down from the top. RED: Them! GREEN: Measuring limits, with the blue binary numbers giving the measurement. We are 9 units high. But what does a unit mean? They will not have foot or metre rulers. But we DO both have a common unit of length - that of the wavelength of the radio waves that carried the message - in this case 21 cm. (The wavelength of a 1400 MHz radio wave, emitted by hydrogen.) So our alien is 9 x 21cm = 1.89 metres tall. YELLOW: A solar system with smaller planets near the Sun and larger ones further out. It looks as though they live on the third planet out from their Sun. BLACK: The antenna that sent the message. It is 1449 units of length across: 1449 x 21cm = 304.29 metres - the size of our largest antenna here on Earth. Isn't it amazing! In only 667 bits of information this message has told us a lot about those aliens. It is in fact a much simplified version of a message that was sent in 1974 by the Arecibo telescope towards the star cluster Messier 13 in the constellation Hercules. That signal which was the most powerful signal ever deliberately beamed into space will not arrive there for about 21 to 25 thousand years!