The video circulating online of a trio of giant tusked beasts bounding through glistening white snow on a crisp day looked like something from a National Geographic documentary—except that woolly mammoths went extinct thousands of years before the invention of the video camera. OpenAI released the 10-second clip in February to introduce Sora, its new artificial intelligence software that can turn written prompts into strikingly realistic-looking videos up to about a minute in length. The new fea...