Why it is built this way
The letters come simplest first, not alphabetically. E is one dot because E is the commonest letter in English, and Morse counted the letters in a printer's type case to decide. The commonest letters got the shortest codes, which is the same idea as a resistor band. Save the sender's time.
A dash lasts three times as long as a dot. The gap inside a letter is one dot, between letters three, between words seven. Get the rhythm right and it works by sound, by light, by tapping on a pipe, or by squeezing somebody's hand.
A code that became a voice
Tania Finlayson, who has cerebral palsy, communicates through morse: a device reads her head movements, turns them into short and long signals, and speaks the result aloud. She then worked with Google to put a morse keyboard into phones, so anyone who can make two signals can write.
Two sounds is the smallest code that can carry a language. That is why it survives.
Now use it
A torch at a window, a spoon on a radiator, a finger on somebody's arm. Send a word, and see if they can send one back.
Back to signals Try the challengesWhere it comes from
Samuel Morse and Alfred Vail did not guess which letters to make short. They walked into a newspaper office and counted the type in the compositor's case: the more of a letter a printer kept, the commoner it must be. E had the biggest pile, so E became a single dot. The alphabet is a piece of measured English, not an invention.
Try it away from the screen
Take a torch into a dark garden with the morse card in your pocket and send your name. Then try tapping it on a radiator, or squeezing it into somebody's hand.