Mount Everest is the world's tallest mountain as ... It's very rare for all of these factors to line up, Butler said, and it might not have happened before the Himalayas. Moreover, on Earth ...

Foot, boot and sock believed to belong to Sandy Irvine, who disappeared in a 1924 expedition, according to National Geographic.

The discovery of the remains leads to more questions about whether two climbers succeeded in summiting Everest in 1924.