？
Will the universe continue to expand infinitely?
Literal
Universe [topic-は] infinitely expanding continue-[question-のか]?
A grand scientific question. 無限に ('infinitely') is an adverb from the な-adjective 無限 (boundless). 膨張する ('to expand / to inflate') is the technical term for cosmic expansion. し続ける uses the compound verb ~続ける ('keep doing'), attached to the verb stem 膨張し. The sentence-final のか frames the question as a reflective, rhetorical inquiry rather than expecting an immediate answer — deeper and more philosophical than a bare か question.