Artificial planets

David Hume famously defined a miracle as “a violation of the laws of nature.”... Richard Swinburne (1970) has suggested that a miracle might be defined as a non-repeatable counter-instance to a law of nature. If a putative law has broad scope, great explanatory power, and appealing simplicity, it may be more reasonable, Swinburne argues, to retain the law (defined as a regularity that virtually invariably holds) and to accept that the event in question is a non-repeatable counter-instance of that law than to throw out the law and create a vastly more complex law that accommodates the event. 

https://plato.stanford.edu/entries/miracles/#MirVioLawNat

What these definitions share in common is the principle that a miracle is a relational concept. A miracle stands in contrast to regular, law-like phenomena. That's what makes a miracle miraculous rather than natural. Put another way, something can only be extraordinary in comparison to what is ordinary. That's the gist of the idea.

Let's put that to the test. Among the furniture of science fiction are artificial planets. If you were living on an artificial planet, how could you detect its artificiality? Or could you?

That depends. In some cases it might be clearly unnatural in one or more respects. But in other cases, the difference might be subtle or perhaps indistinguishable. 

Suppose a planet had climate control. It rains once a day between 2-4 AM. That's ideal because it keeps everything well-watered and lush, yet it doesn't interfere with human activity. It's always sunny and dry in the daytime. 

The rainfall would be utterly regular, as if it was scheduled to rain between 2-4 AM once a day. As if there was a timer. 

Suppose there's nothing manifestly artificial about the climate control. There's no machinery that produces that phenomena. To all appearances, the planet has a natural water cycle. The nightly rainfall violates no physical laws. 

Ironically, what's suspiciously unnatural about the rainfall is the mechanical regularity of the rainfall. The very thing that defines what is not miraculous, on the conventional definition I'm using, is the same thing that in this case points to the fact that the planet must have been engineered. Not only is the  pattern repeatable, but exactly repeatable. Yet there's no tangible explanation beyond its convenience for the inhabitants.