Chapter 1: Section 7: Page 64: Line 154 (1136)

 As a mechanic he respected any straightforward chain of cause and effect you could see or handle, but chemical reactions like this went on down in some region too far out of anyone's control, they were something you had to stand around and just let happen, which was about as interesting as waiting for corn to grow.

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Pynchon forces the reader to contemplate two vastly different aspects of our universe: things in which we can observe directly the way they work and those things we observe through evidence and experiment alone. Is he hinting at the stark difference between general relativity and quantum mechanics? Is he making a sly joke by identifying a "mechanic" with the big trappings of the universe who is mystified by the unseen that he can't get his hands on?

"any straightforward chain of cause and effect you could see or handle"
This feels like an excellent summation of the kind of "common sense" that mediocre people pride themselves in having. It also seems, in the context of the current discussion on light and Æther, a bit of irony in the use of the term "straightforward". Only perhaps in the machines Merle builds and repairs can one look at the universe in this straightforward chain of cause and effect. You can see what moves when you turn a crank. You can follow the path of a belt to see how it causes movement within a structure. In the same way, people might think their observations of the universe can be interpreted just as straightforward. But as Merle goes on to explain, much of the world takes place "in some region too far out of anyone's control."
    But let's get even further into the subtext. Could Pynchon be speaking about writing here? Merle respects plot which happens right on the surface where you can follow characters' actions and motivations which move the story forward. But the subtext, the chemical reactions, need deeper thinking to see and understand. Maybe Pynchon's even hinting at how the author sometimes loses control of the subtext ("too far out of anyone's control"), seeing as how much can be brought to the text by the reader that wasn't intended by the author. Sort of like 85% of what I've written on this blog.

"about as interesting as waiting for corn to grow"
But to the layman, subtext is boring. Just get to Merle fucking Erlys already and don't make me think about how that means Merle's fallen in love with light itself!