There is no way to tell that something is made by ‘intelligence’ merely by looking at it—it takes an extensive collection of knowledge about its environment to determine whether something is likely to have arisen through simple processes.
A pile of garbage seems obviously unnatural to us only because we know a lot about Earth nature. Even so, it’s not a machine. Aliens concluding that it is a machine with an unknown purpose would be mistaken.
In order to figure out if it’s made by intelligence, you need to figure out how likely it is that natural processes would result in it, and how likely it is that intelligence would result in it. Working out the former, though far from trivial, isn’t as interesting and isn’t what he’s wondering about. He’s wondering about how to do the latter.
There is no way to tell that something is made by ‘intelligence’ merely by looking at it—it takes an extensive collection of knowledge about its environment to determine whether something is likely to have arisen through simple processes.
A pile of garbage seems obviously unnatural to us only because we know a lot about Earth nature. Even so, it’s not a machine. Aliens concluding that it is a machine with an unknown purpose would be mistaken.
In order to figure out if it’s made by intelligence, you need to figure out how likely it is that natural processes would result in it, and how likely it is that intelligence would result in it. Working out the former, though far from trivial, isn’t as interesting and isn’t what he’s wondering about. He’s wondering about how to do the latter.