Great cosmic signs have traditionally been interpreted as the fulfillment of Bible prophecy and signs of the nearing Second Coming, such as the 1755 Lisbon earthquake in Portugal, New England's Dark Day of 1780, and a spectacular meteor shower in 1833. This is based on the sixth seal (Revelation 6:12–17) of the "seven seals", and Jesus' end-times sermon in Matthew 24:29 and Mark 13:24–25 (see also Luke 21). Adventists had argued the Dark Day was a supernatural sign. Critics claim that it occurred from natural causes due to forest fires. The interpretations are still commonly held by Adventist, although some have challenged the interpretations.