When you read Bobiverse, do you find yourself comparing it to what you know of Physics and notice when it appears to diverge? Or do you treat it like Star Wars, where we know blasters and light sabers and the Force aren't real, but enjoy the internal logic of this space fantasy all the same?

I tend to notice... but stress this doesn't take me out of the story or detract from my enjoyment of the series in any way. I don't think Bobiverse is intended to be completely hard Science Fiction, but the Bobs themselves enjoy discussing Physics, and I don't think it's intended to be completely soft either. I occasionally point out here where my suspension of disbelief is stretched, in questions such as

Other people enjoy down-voting me, or prefer to argue purely from the logic of the books, both of which is their right of course.

So that we can each have our respective fun today, I'd like to consider the Relativity of Simultaneity, and how the appear to undermine it.

The Relativity of Simultaneity is from Special Relativity, and says it is impossible to say in an absolute sense that two distinct events occur at the same time if those events are separated in space. It can be a difficult concept to get your head around. Certainly it's saying a lot more than simply if there are two supernovas, the one you see first will depend upon which is closest to you so that its light reaches you first. Some people try to cling dogmatically to the intuitive notion that there must be an absolute order to events even if it is not knowable, but that doesn't work. It's also not saying events are completely unordered - if light has had time to travel from event A to event B such that A could have caused B, then no observer is going to disagree that A was first. At least no observer traveling slower than the speed of light.

OK, so here's a quote from Heaven's River, part 2, chapter 5, which should now ring some alarm bells:

So there's the problem. There simply is no absolute ordering of activation in that scenario. To say one becomes the parent and the other the child because of the order in which they were activated is a violation of the Relativity of Simultaneity.

What do you think? That’s where I first realized Bobiverse might have a problem with the Relativity of Simultaneity. But actually I think the issue arises much sooner,