During cooling most migrants would be expected to travel toward Africa, which is near the equator, since this is the direction dictated by habitat changes on a cooling Earth.
That's about how high an object would have to be orbiting straight up from the equator to constantly remain directly above the exact same spot on the rotating planet Earth.
这大约是一个物体从赤道沿轨道垂直向上运行的高度，这样它就可以一直保持在地球同一地点的正上方。
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Our planet Earth is comparatively small, with only about 24,902miles around the equator.