[ghein]

The second part of your analogy is off.

It's not billiard physics to general relativity, it's billiard physics to fluid dynamics and predicting the exact route of a stick through a set of rapids.

In economics our biggest complaints are around failure to determine that we're near a singularity and failure to predict behaviour through singularities (in a signal processing sense). It's understandable, as we all strongly care about the path of the stick, yet still unreasonable.

Macro is a decent enough tool most of the time, as are traditional fluid mechanics approaches. What we don't have are ultra precise CFD tools but in our arguments we act like we should/do. Sometimes traders think that they do have a great CFD solution and that's how we get LTCM crashes!

[dv_dt]

Fluids is a pretty good metaphor, but I would say that today we have sufficiently good reproducible physical understanding of fluids that we can generally fly airplanes at a high level of certainty (e.g. turbulence on the wings is both predictable and controlled in the correct ways that the plane does not crash). In comparison we crash the economy and even sub portions of markets periodically (and the last general crash was worse than many previous recessions) - we don't even have a complete picture of which turbulent areas to be wary of economically.

Or to maybe to a more human point, we can carry humans around on airplanes just fine, but don't know how to carry a payload of a nation of humans on a stable and healthy economic vehicle.