River's expression turned serious and, finally, she took a step forward and leaned in just enough to give what she said next a conspiratorial feel.

"Solar cycles become irrelevant but the tendency remains," she said with a serious little nod at the end for emphasis.

Her eyebrows furrowed a bit as she leaned back. And then, because there obviously hadn't been enough allusions to people being teapots already, "Change the spout, the tea, and the whistle is at a different pitch. Inaudible but present."