I believe that it is assumed that the 'laws of physics', as we know them, apply throughout the universe. Is this a reasonable assumption or is our concept of cosmic reality an error?

On one interpretation of what you say, I don't think your belief is correct. I would wager that most scientists believe rather that the laws of physics, as they are presently formulated, are not quite (or in some cases, not even close to being) correct. Our experience of trying to know what the laws of physics are and then finding ourselves surprised to learn that they aren't quite what we thought gives us some reason to believe that our best theories now don't quite get things right either.

But perhaps your question is rather about the scope of the laws of physics. Perhaps you're wondering whether certain laws hold in this corner of the universe and other laws hold in other areas of the universe. That's an empirical question, of course, and we'd have to ask the physicists. But there is something about inquiry that would make it hard for us to accept this, I think. One goal that regulates inquiry is to find an account that unifies a vast range of phenomena. The more a scientific theory can relate seemingly unconnected phenomena to one another and show that they all result from the workings of a small number of very general principles, the more highly prized that theory is. This might make it very difficult for scientists to settle on a bifurcated account along the lines of "These are the laws for over here, and these are the ones for over there." Built into our conception of a successful account is the notion of generality. I suppose that if we're wrong about that and can't let go of that goal, then we'll always be hankering after something we cannot have.

I agree with Alex that our best hypotheses may well not capture the actual laws of nature, and that physicists strive for unification, and I think there is a third aspect to this question. In spite of what the 20th century philosopher of science Karl Popper maintained, science depends on induction, on making inferences about the unobserved on the basis of the observed. And as the great eighteenth century philosopher David Hume observed, this depends on some kind of assumption of the uniformity of nature. Hume notoriously argued that we can have no good reason for this assumption, and that is very close to the point that we have no good reason for assuming that the laws of physics are the same in those parts of the universe we have observed as they are in those parts we have not observed. But without making something like that assumption, science would be impossible.

To put it differently, to leave open the possibility that laws might be different elsewhere is, if taken to an extreme, not just to abandon science's preference for unity: it is to abandon science. As the great physicist James Clerk Maxwell put it, we had better hope that nature is more like a book than a magazine.

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