“The message is just 210 bytes of information organized onto a grid of 1679 binary digits. That particular number was chosen because it’s semiprime, meaning it is the product of two prime numbers, in this case 23 and 73. That means any civilization that received the message would know the grid would have to be 23 by 73, and only one of the two possible arrangements presents intelligible information.”
(via This is the binary message we sent out to aliens 38 years ago)


