Latitude 66 and a half (66.5) marks the Arctic Circle.
The Arctic Circle is an imaginary line that circles the Earth at approximately 66.5 degrees latitude, which is located in the northern hemisphere. This line marks the southernmost point at which the sun can remain continuously above or below the horizon for a full 24 hours, depending on the time of year.
Therefore, if you are at a location with latitude 66.5 degrees or higher, it means that you are within the Arctic Circle and can experience the phenomenon of the midnight sun during the summer solstice, where the sun remains above the horizon for a full 24 hours. In contrast, during the winter solstice, the sun will not rise above the horizon at all, resulting in 24 hours of darkness.
Hence, the correct answer is:
- Arctic Circle