Dusk

Dusk is the darkest part of evening twilight, just before it is properly night. It is the time when it is too dark to read but too light to put the lamps on, so nobody does anything.^[1]

Dusk is recognised by everybody at once, which is why every house on a street switches its lights on within the same four minutes, each household believing it was first.

Official dusks

There are three official dusks: civil, nautical and astronomical, which end when the centre of the Sun is 6, 12 and 18 degrees below the horizon. Each is a little darker than the one before, and each was defined by a different group of people who were not prepared to share one.^[2] A proposal for a fourth, “domestic dusk” (when someone says “it’s getting dark, isn’t it?”), is still under review.

Dusk and dawn

Dusk is often confused with dawn, as both are dim and involve the Sun near the horizon. The difference is that at dawn it is getting lighter and people are cross because they have just started, whereas at dusk it is getting darker and people are cross because they have not finished.

Wildlife

Animals that are active mainly at dusk and dawn are called crepuscular. Rabbits and deer are examples. They have chosen the two times of day when nobody can see them properly, which zoologists consider either clever or shy.

See also

• Sun – the cause, leaving
• Time – what dusk is a part of
• Minute – dusk lasts several

References

1. Gloaming, G. (2001). Getting Darker. Twilight Press. p. 18 (of 18).
2. Committee on Dimness (1963). “Three Dusks Are Enough”. Minority report attached.