We have to announce that all modern physics is rubbish

Well, obviously it's rubbish, eh? Because as Walter Heisenberg pointed out we can't even pin point the location of a particle using physics. So, what's the use of it, eh? We can know where an electron is going, possibly even how fast, but not where it is. So, thus, obviously, we need to take an entirely different approach to the whole subject of trying to understand the physical world around us. At least, this would be so if we were to take Tim Garton Ash on economics seriously:

The Guardian recently asked nine economists whether we’re heading for another global financial crash and they gave many different answers. Yet still we turn to economists as if they were physicists, armed with scientific predictions about the behaviour of the body economic. We consumers of economics, and economists themselves, need to be more realistic about what economics can do. More modesty on both the supply and the demand side of economics will produce better results.

Which is to entirely miss the point over what economics can tell us about the timing of crashes. The physics tells us that we cannot know both velocity and location of that electron. This is a finding from the science: it's not one of those things open to negotiation nor something that we're going to solve by using a different evidential or logical approach.

And so it is with the timing of a crash in financial or other markets. We do not in fact say "Oh, economics cannot predict that". We say that "It is impossible to predict that, we have proven it". Thus the hunt for a predictive method for a crash is a odd as a hunt for the true location and also velocity of a particle. It's not that we cannot do it with the current state of the science: it's that the science has proven that we cannot do it.

Thus, if economics fails on this point then so does all of modern physics fail on the same point. And the silly thing about saying that is that nuclear bombs still go boom even if we cannot tell which particle caused it in what manner, and economics is still, even the current economics we use is still, hugely useful in describing the larger world we live in, even if not accurate to the level of detail that physics is not.

Yes, let us be realistic about what economics can do. One of the things we know it cannot do is predict a crash.