How was this one particular inference made? [Death's End]

Note: I'm still only on page 503 of Death's End, so no spoilers for the last 300 pages please :)

>!My question is how the fairy tales suggested lowering the speed of light. I can clearly follow how they interpreted parts of the fairy tale as a metaphor for light (fastest, weightless and massless). But then the book goes on to say that "...capturing the bubbles from the bubble tree had two possible interpretations: collecting the power of light or lowering the speed of light". This has me baffled. The previous page contains excerpts from the fairy tale, but after re-reading several times there's nothing in there that (to me) hints at lowering the speed of light. What are they basing this interpretation on?!<

>!I carried on reading at first, figuring that it doesn't make a difference whether or not I understand what the book's characters based their inferred meaning on, but it's been bugging me as I continued reading so I've would love some help to understand. Thanks!!<