# Who sent the message?

Arecibo Message

0000001010101000000000000101000001010000000100100010001000100101100101010101010101010010010000000000000000000000000000000100000000000000100000000000000000000000000011100000000001110000001111100000000011110100110111000000000110111001110110000000000111110000010100000000010000100111111000000000111111000000000000000000000000000000000000000000000000000000000000000000000000000011000000001000000000000100000001010000000001111110000011111100000000000000000000000000001000000010000000000000010000000100000000000000100000111110000000000001000010111010000000000000001001110010000000010111000011100000000000000000000101000000000000010000001010000010000000100000010100000100000001000001101100000000000000000000000000000000001111000000000000000000011110011000000000000000111100110111011100000001111000001110111000000000000000011101110000000111100000000000000000001111000100100010000000011110000000000000000000111100010010001000000000000000000000000000000000000001001000100000000000000000000000000000000000000000000010000000000000000000000000000000000000001111100000000000000001111111110000000000001110000000111000000000110000000000011000000011010000000001011000001100110000000110011000010001010000010100010000100010010001001000100000000100010100010000000000001000010000100000000000010000000001000000000000000000000000000000000000010010100000000000111100111110100111100

2,380 MHz

Who sent the message?

A friend of mine set me this and I enjoyed it, so thought I'd post it here :)

Edit Notes:

The answer does not have to come from real life (i.e. fiction is allowed)

With the answer of @JonathanAllan in mind, I believe the sender is

C-3PO
He is a droid so his "DNA" is made of Copper, Zinc, Iron, Silicon, Carbon and Gold.
He has an human shape and size, so that part of message is equal.
He is from Tatooine, the first of 3 planets orbiting two stars in Tatoo system.
Each dot bellow the planets in the messsage is a moon, which is consistent with the Tatoo system.

• Correct! Though I do have to give a lot of the credit to @JonathanAllan :) The Copper, Zinc, Iron, Silicon, Carbon and Gold are the elements with the largest amount inside his body, sorted by atomic number on the left and amount on the right. Below are the two common compounds that make up his body, Brass and Steel. Additionally, no-one looked at the count to the right of the humanoid figure. Anyone? – Matthew Stephenson Oct 29 '16 at 21:09
• Cool, I don't think I'd have got there... – Jonathan Allan Oct 29 '16 at 22:18
• @MatthewStephenson - population=1 (A one of a kind prototype, created by A.S.). – Jonathan Allan Oct 29 '16 at 22:23
• Yes indeed :) I found the end difficult too, down to my complete lack of knowledge of Star Wars, so that makes two of us :) – Matthew Stephenson Oct 29 '16 at 22:37
• @JonathanAllan Annakin invented C-3PO? I thought it was just a droid he repaired. – user64742 Oct 30 '16 at 5:04

The message is

$1357$ bits long, which has a prime factorisation of $23\times 59$ yielding a not so friendly looking:

The number section (the top strip) is identical.
The DNA atomic element identification has been rotated and moved to the right with another similar figure placed on the left.
It looks like "they" are from a twin-star system, from the smaller and innermost of three planets (the raised square beneath the humanoids feet)
A search seems to indicate that we only know of one such system - the stars HD 133131A and HD 133131B in Libra, hosting two and one planets respectively, if this is their origin "they" are from HD 133131A b (the others being HD 133131A c and HD 133131B b)
The height indication is the same as the original message.
The rotated DNA read in the same fashion as the original message would be
[29, 30, 26, 14, 6, 79]
That is Copper, Zinc, Iron, Silicon, Carbon, Gold;
While it's counterpart on the left would be
[6, 14, 26, 29, 30, 79]
That is Carbon, Silicon, Iron, Copper, Zinc, Gold.
Underneath this we have two "nucleotides", which might be indexed by left or right:
[0, 0, 0, 3, 2, 0] -> $\text{Cu}_3\text{Zn}_2$ (brass), and/or $\text{Si}_3\text{C}_2$; and
[1, 0, 3, 0, 0, 0] -> $\text{C}\text{Fe}_3$, and/or $\text{Cu}\text{Fe}_3$
The population reads as $1$.

So whoever "they" are there is only one of them; they have the same shape and size as an average human, they are made from metals, carbon and silicon (a humanoid robot), and are from the inner of three planets of a binary star system.

(The planetary system also shows moons, and Doguita found the solution!)

• This is true, but doesn't answer the question :) Who sent the message? – Matthew Stephenson Oct 29 '16 at 17:36
• @MatthewStephenson Users on Puzzling often post partial answers to share their progress and help other users. – user14478 Oct 29 '16 at 17:40
• I do not know who sent it, but my guess is we need to look into the spec of the original... – Jonathan Allan Oct 29 '16 at 17:41
• @Lukas Yeah sorry, I'm new here obviously I only realised after that he wan't submitting a full answer :) – Matthew Stephenson Oct 29 '16 at 17:43
• And yes, comparing the two will help – Matthew Stephenson Oct 29 '16 at 17:43