When does an echo stop being an echo?

[David Johnston2]

Every time Homeliners and Centrum wrestle over "changing history" to try to break or preserve the echo's status they are in fact changing history. They're only fighting over how much it will be changed. If none of those changes would alter recorded history directly or indirectly, it's definitely still an echo. If it changes nothing more than a single footnote then it's still an echo. If Lincoln visit to the theatre is delayed by one day but everything else plays out the same, still an echo.

But let's say that a reality storm plucks the St Louis out of the ocean in a 1939 echo, sending the crew and nearly a thousand refugees elsewhere is it still an echo?

[Stormcrow]

Infinite Worlds is the most handwavy of all campaign settings. These things are set by the GM's whim; no specific logic is given.

In the realm of pure mumbo-jumbo, I would say that timeline variations are not completely chaotic: there exists a physical threshold beyond which the timeline's inertia no longer keeps it in historical sync with Homeline but spins it off chaotically into its own parallel. But since such a threshold is set by the GM according to the needs of the narrative, I can't tell you what the in-game threshold would be.

[Anthony]

This is similar to the classic "A language is a dialect with an army and a navy". Fundamentally, the classification is a political question.

[Stormcrow]

It is not a political classification: echo timelines that cease to be echoes change their quantum levels. They cease to be unstable thereafter.

[TGLS]

Here's how I'd handle it: Most timelines are echoes, the only real question being, "Echoes of what?" Echo-1887 and Britannica-6 can both be shifted between Quantum levels, but Centrum and Infinity have the advantage in knowing where Echo-1887 "should" be going, while they have no idea where Britannica-6 should be going. So, in Echo-1887 Centrum agents can plot to stop the invention of Coca-Cola to kneecap prohibition, where as they have no clue what to do on Brittanica-6 to shift it around.