At what latitude(s) on Earth will the Sun never set when it is at the summer solstice?

Question

At what latitude(s) on Earth will the Sun never set when it is at the summer solstice? Is there any latitude on Earth that the Sun will never set when it is at the vernal equinox?

Answer 1

All latitudes from the arctic circle to the pole.  If you're talking about the northern hemisphere, that would be anything north of approx. 66.5 degrees.

There is no latitude where the sun will not set at the vernal equinox unless you consider right at the poles (90 degrees), where the sun wwould just run all the way around the horizon.  If you get up to 1/2 degree away from the pole, you will be able to see some part of the sun during the whole rotation, but this is where the definition of "set" has to be established.  Are we talking about the whole sun or just a point at the center?