Science-fiction settings with coherent physics

Which science-fiction universe has the most coherent physics and technology tree?

The choices include Worlds of the First World War, a qualified endorsement of BattleTech, and Stewart's novels. The answers distinguish consistent fictional rules from compatibility with modern physics.

Worlds of the First World War is nominated for tracing military spacecraft back to Martian equipment salvaged after the 1897 invasion. BattleTech receives a more qualified endorsement: its rules are broadly consistent, but the low weight of giant walking machines and its loosely explained faster-than-light travel attract objections. The disappearance of space warships prompts a separate argument about whether industrial decline explains the loss of a technology that the setting's physics still permits. A claim that a naval particle cannon appears on a BattleMech raises another scale problem, although the participant making it cannot immediately identify the source. Dr. Clarke's own choice is Stewart's novels, praised for attention to both internal consistency and modern physics, with the explicitly magical stories excluded from the latter comparison.