A professor in Cambridge University has showed his proof that the sum of natural number was equal to -1/12. The video can be found on the internet. Well, although the way to proof I think is really ridiculous, it could be a good way to building a new math model. Since we think the sum of natural number is infinity, but that professor proved it equal to a finite number, so maybe this model can express infinity in finite way. Finally, a lot of modern problems about physics and many other fields.