The "Arecibo Message" was beamed towards globular cluster M13 #OTD in 1974, during the dedication of an upgrade to the radio telescope. It was the first message sent with the intention of alerting extraterrestrials to life on earth.

Being a technological civilization is beaming "sorry for the speed-of-light delayed response!" back and forth across the cosmos with some other lonely island until one of you manages to extinct yourself.

The message was 1679 bits, arrayed into 73 rows and 23 columns. It contained depictions of the numbers 1-10, the solar system, the human form, and info about the elements and biochemical structures associated with life on Earth.

Prime numbers were chosen for the dimensions of the array in the hope that they would stand out!

The message should arrive in about 22,000 years, give or take a few hundred. So in around 44,000 years, maybe our futuristic detection network will pick up a delicate radio transmission in response. Maybe we'll still be around to decode it.

Maybe not.

But that's the thing about broadcasting: Once the message is out there, it's out there.

You can read more about the Arecibo Message and other early @SETIInstitute projects here: https://www.seti.org/seti-institute/project/details/arecibo-message

Anyway, forty six years ago today we sent a hopeful message to the stars. Properly formatted, written in 1s and 0s, it fits into just a bit more than six tweets.

00000010101010000000000
00101000001010000000100
10001000100010010110010
10101010101010100100100
00000000000000000000000
00000000000011000000000
00000000001101000000000
00000000001101000000000
00000000010101000000000
00000000011111000000000
00000000000000000000000

11000011100011000011000
10000000000000110010000
11010001100011000011010
11111011111011111011111
00000000000000000000000
00010000000000000000010
00000000000000000000000
00001000000000000000001
11111000000000000011111
00000000000000000000000
11000011000011100011000

10000000100000000010000
11010000110001110011010
11111011111011111011111
00000000000000000000000
00010000001100000000010
00000000001100000000000
00001000001100000000001
11111000001100000011111
00000000001100000000000
00100000000100000000100
00010000001100000001000

00001100001100000010000
00000011000100001100000
00000000001100110000000
00000011000100001100000
00001100001100000010000
00010000001000000001000
00100000001100000000100
01000000001100000000100
01000000000100000001000
00100000001000000010000
00010000000000001100000

00001100000000110000000
00100011101011000000000
00100000001000000000000
00100000111110000000000
00100001011101001011011
00000010011100100111111
10111000011100000110111
00000000010100000111011
00100000010100000111111
00100000010100000110000
00100000110110000000000

00000000000000000000000
00111000001000000000000
00111010100010101010101
00111000000000101010100
00000000000000101000000
00000000111110000000000
00000011111111100000000
00001110000000111000000
00011000000000001100000
00110100000000010110000
01100110000000110011000

01000101000001010001000
01000100100010010001000
00000100010100010000000
00000100001000010000000
00000100000000010000000
00000001001010000000000
01111001111101001111000

As @FakeUnicode once showed me, you can do it in two tweets if you use unicode Braille characters.

⡄⡂⡆⡁⡅⡃⡇⡠⢠⠄⡢
⠀⠀⠀⠀⠀⣤⢲
⣀⠀⠀⣀⡘⠚⣚⠀⠀⣀
⠷⠴⠄⠴⠦⠄⠶⠭⠄⠷⠴⠄
⣀⣈⡄⠀⠀⠀⠀⠀⠀⣀⣈⡄
⣖⢀⠀⠒⣄⠀⢒⣂⠀⣖⢀
⠉⠩⠁⠉⠉⣥⠉⠉⠁⠉⠩⠁
⠒⡒⠃⠀⠀⢿⠀⠀⠀⠒⡒⠃
⠀⠈⠒⠤⠀⣻⠀⣀⠤⠊
⠀⡠⠒⠉⠀⣞⠀⠀⠉⠢⡀
⠘⢄⠀⠀⠀⠝⠀⠀⣀⠔⠁
⠀⡆⠉⠒⣂⣆⡒⠉

⠄⠥⠄⠊⢸⢿⠈⠂⢱⣟⢾⡇
⠀⠇⠀⠀⠼⠸⠄⠀⠘⠋⠉⠁
⠀⠿⠇⠂⠂⠁⠂⡆⡆⠆⠆⠂
⠀⢀⡤⠖⠛⠛⠓⠦⣄
⢰⠋⢸⠢⡀⠀⡠⢺⠈⢳
⠀⠀⠸⢀⠈⡊⡀⠸
⠈⠉⠁⠈⠉⠉⠈⠀⠉⠉