Cambridge mathematician Timothy Gowers used an unreleased ChatGPT 5.5 Pro to solve a long-standing open problem in combinatorial number theory within an hour. The AI independently constructed an original proof for improving the upper bound of sumsets, a result praised as ingenious by experts. This breakthrough challenges skepticism about AI's mathematical reasoning and raises new ethical questions for academia, including the publication of AI-generated research and the redefinition of advanced mathematical training.