Malam kutub

Malam kutub terjadi ketika keadaan malam hari berlangsung lebih dari 24 jam. Peristiwa ini hanya terjadi di lingkaran kutub.^[1]

• Hansen, V.; Lund, E.; Smith-Sivertsen, T. (March 1998). "Self-reported mental distress under the shifting daylight in the high north". Psychological Medicine. 28 (2): 447–452. doi:10.1017/S0033291797006326. PMID 9572101. 

• The polar night and polar darkness Diarsipkan 2012-09-04 di Wayback Machine.
• Many years' of webcam pictures from Tromsø, Norway. These clearly show the progression into and away from winter at a latitude within the Arctic Circle.