This was ok: there was at least one time-travel idea that I hadn't come across before, and I think I'll understand some things a bit better on a second reading. However, the ending is a bit weak, and I don't think the logic quite works.(view spoiler)[The characters refer to Worldline A, where Murphy works for NASA. However, he wrote his article based on reported UFOs; presumably he was therefore reacting to existing time travellers, which means that he was already living in an altered timeline.
Also, the original timetravel experiment (in Worldline B) involves sending "Herbert" back in time by 1 second. After that, the clocks don't match: "The one on the left, displaying the time as perceived by the SR-75, was 00:24:03:24. Yet the one on the right, which relayed the time as transmitted from Herbert, was 00:24:02:24." This is backwards! Herbert has now experienced the same second twice, so its clock should be 1 second later than the escort. Look at Doc Brown's original test in Back to the Future to see this logic applied correctly. (hide spoiler)]