120 years ago, people thought that experimental results on wave propagation in continuous media could be used to make statements about wave propagation in electrodynamics. That's how we ended up with ether theories, which were eventually falsified with interferometric experiments.
To my mind, we should take this as a lesson that the notion of analogue systems (e.g., using results from fluid dynamics to make statements about gravitation) is bogus. The ether episode seems to indicate that if we want to make statements about gravitational Hawking radiation, we need to do tests on a system where the gravitational dynamics are important (e.g., a black hole), not an unrelated system that just happens to be governed by an identical set of equations in some regime.
Another example of people incorrectly conflating properties of an analogue system with the real system of interest is the Nature monopole paper: http://www.nature.com/nature/journal/v505/n7485/full/nature1...
The actual result contained in the paper is that you can make a BEC whose vorticity field has regions of nonzero divergence. It is mathematically similar to (but fundamentally unrelated to) actual magnetic monopoles. Nonetheless, the paper contains the phrase "Dirac monopoles" in the title and then spends half the abstract talking about actual magnetic monopoles, as if the result is somehow relevant to actual magnetic monopole searches (which it isn't).
To my mind, we should take this as a lesson that the notion of analogue systems (e.g., using results from fluid dynamics to make statements about gravitation) is bogus. The ether episode seems to indicate that if we want to make statements about gravitational Hawking radiation, we need to do tests on a system where the gravitational dynamics are important (e.g., a black hole), not an unrelated system that just happens to be governed by an identical set of equations in some regime.
Another example of people incorrectly conflating properties of an analogue system with the real system of interest is the Nature monopole paper: http://www.nature.com/nature/journal/v505/n7485/full/nature1... The actual result contained in the paper is that you can make a BEC whose vorticity field has regions of nonzero divergence. It is mathematically similar to (but fundamentally unrelated to) actual magnetic monopoles. Nonetheless, the paper contains the phrase "Dirac monopoles" in the title and then spends half the abstract talking about actual magnetic monopoles, as if the result is somehow relevant to actual magnetic monopole searches (which it isn't).