While watching the 1902 film A Trip to the Moon I became curious why there is such a long period in movie history where there was just no sound. I know this sounds like a strange question along the lines of 'Why were the first photographs only black and white?' And it may be just that the technology didn't exist, but I feel like it would have been so easy just to record the audio of the film onto gramophone records (which were already popular) and play it over speakers in the theatre, syncing the speeds of the video and audio.
I know there would be an issue with starting the audio and video at the right time so it wouldn't get 'off,' and you would have to change records throughout the movie, but it doesn't seem like those issues are big enough to mean that there couldn't be sound at all.
Thanks for the help!
They tried exactly that, and it didn't work, even with dedicated techs trying their best (remember, somebody still has to switch between projectors on a two-reeler). The same system in the hands of a lone operator who was easily confused or didn't care that much would have been a disaster, so no one wasted money on it.
You also need to realise that talkie technology wasn't 100% approved as it was. Lilian Gish hated it, not because she had a bad voice, but because she thought silents were a special art form in themselves. If she couldn't do that anymore, why, she'd just do Chekov in live theatre (Life and Lilian Gish a bio).
There was an economic factor, too. With silents, you could distribute all over the world just by changing the language of the title cards. With talkies you had to reshoot or dub the whole thing with good foreign voice actors. A talkie system had to be very good, simple, and reliable for studios to buy sound recorders and build sound stages, and add musical soundtracks, and theatre owners to put in sound systems with speakers and sound-reading projectors.
And you do know that the electrical microphone for sound recording wasn't invented until c.1927 IIRC? It led directly to the invention of the crooner. Before that, the acoustic mike was kind of like bellowing down the horn of an early Victrola - getting all the sound off actors performing for the camera would have been very patchy.
You had a good guess - the technology wasn't up to it!
And it may be just that the technology didn't exist
Bingo! And although the suggestion of recording the sound onto a separate medium was not unheard of it would have been far too difficult to achieve. You'd have to ensure the timings were perfect, that the sound was edited perfectly and was only recorded as needed (near impossible) and it would have been expensive. Not only that, there was no where in making recordings that were that long in the early 20th century.
Adding to what others have said, we are spoiled by digital media to think that something that is 4'21" in length is always exactly that long. On analog media, that's not the case - whether you're dealing with tape or records, you basically have motors going around and around as consistently as they can. A very slight fluctuation - caused by something as simple as materials expanding or contracting due to temperature, or minute warping - can cause changes in time. Until we had the technology to print the audio directly to the same reel that the film was on, synchronization was a total crapshoot. Have you ever seen a YouTube video where the audio and visual are off by a split second? It's so jarring and bizarre. Imagine a thousand little imperfections adding split seconds to split seconds. The process you describe could have the audio and video off by nearly a minute by the end if enough common mishaps ocurred.