All we have to do is look at the elements used in CC to find out that physics is different in the Chrono Series. Heck, even in the FF series. Aslong as a game has magic, physics will be different. Spekkio said something relatiev that Shadow, Fire, Lightning and Water magic were the primary bases of the universe, and kept everything in order.
In CC, we see ultranova's and black holes. They're all contained. Heck, even Lavos' portal in Magus' Castle caused the whole castle to dissapear, even thought it was supposedly a gate. But whatever happened, it wasn't just Crono and co and Magus that got displaced. To suck in a whole castle... Now that sounds more like a job of a black hole to me. But it's not, or is it?