> I'm curious to what degree Unruh radiation (and the resulting consequences this idea relies on) 'established physics'? Most theorists think Hawking–Unruh rad

> I'm curious to what degree Unruh radiation (and the resulting consequences this idea relies on) 'established physics'? Most theorists think Hawking–Unruh radiation has to exist, I guess because the calculation is relatively straightforward. You just need special relativity and some basic field theory. Hawking–Unruh radiation has never been observed in a gravitational system, and doing so would be very difficult because it requires a truly enormous acceleration in order to produce a horizon with a temperature that is an appreciable fraction of 1 K. There are certain regimes in fluid mechanics where the mathematics governing the fluid looks like the mathematics governing relativity. Some people have produced phenomena in those systems that look like Hawking–Unruh radiation. Some people further claim that this demonstrates the existence of Hawking–Unruh radiation for gravitational systems, but I find that reasoning to be specious.