However, the vertical downward distance should be at least thousands of miles away. The underground temperature here is extremely low, and all around is white. The gap in the path is larger. Because it is very close to the source, it is not necessary to walk with your head down now.

now they are walking in such a big dark hole in a football field. Not far ahead, there are several such holes.

because the temperature here is extremely low, now it's all under the ground, at least thousands of miles away. Such a low ground, let alone light, has no air here.

and because the temperature here is low,...