In Mongodb, how do I first sort by score, then sort by time if there is a “tie”?

Question

results = docDB.posts.find({"active":True }).sort("pop_score", pymongo.DESCENDING)

This is my sort right now. But the problem is, some things have the same "score". In that case, if they tie, I want them to sort by "time" within the ones who tied.

How do I do that? It's possible to do that in Mysql...