Short Story with Time Travel separating the user from causality

Question

I was reading a lot of Asimov, Clarke, Brown and Heinlein at the time, so I wouldn't be surprised to find it's one of them but I haven't been able to find it.

The story involves the main character (I want to say a scientist) finding/inventing a way to time-travel. He goes back in time, and screws up (I forget the details.. Squishing a bug, perhaps, or leaving a pencil behind or something), and when he comes back, expecting a 'Sound of Thunder' kind of change... nothing has happened.

Wondering what is going on, he goes back and makes a larger change. Still nothing. He keeps going, escalating the nature of his changes (I think he kills his grandfather at one point), yet nothing changes. Then, on one return, he's unable to touch the controls.. After some frustration, he exclaims aloud and is answered...by another former time-traveler.

The other explains to him that common understanding of time & causality is flawed. Each person has their own chain of history, and they don't interact. He uses the analogy of a pot of spaghetti, with each person's personal past being a strand. Our hero, in making massive changes to his own past, has basically severed it, and he has come loose. He can now see OTHER strands (and those who are like him) having become, it is explained, the Spaghetti sauce.

Any ideas?

Answer 1

“The Men Who Murdered Mohammed” by Alfred Bester. Written in 1958 and republished in many collections.

The protagonist catches his wife in the middle of adultery and decides that killing her would not be enough: he wants to erase her out of existence. So he goes back in time and kills her grandfather, then her grandmother, then George Washington, Mohammed and other historical figures. The present is unaffected. After a while, the protagonist loses the ability to affect even the past. Eventually another time traveler in the same situation contacts him, providing the explanation you remembered.

Found with the help of Jo Walton's blog post on “five short stories with useless time travel”. The other four she cites are

• “The Man Who Came Early” by Poul Anderson, where a visitor to the past utterly fails to impress his primitive hosts.
• “Thus We Frustrate Charlemagne” by R. A. Lafferty, where the characters are changed together with the rest of the world and therefore don't realize anything changed.
• “House of Bones” by Robert Silverberg.
• “Veritas” by Robert Reed.