The doldrums is a colloquial expression derived from historical maritime

Sea

A sea generally refers to a large body of salt water, but the term is used in other contexts as well. Most commonly, it means a large expanse of saline water connected with an ocean, and is commonly used as a synonym for ocean...

 usage for those parts of the Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 and the Pacific Ocean

Pacific Ocean

The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...

 affected by the Intertropical Convergence Zone

Intertropical Convergence Zone

The Intertropical Convergence Zone , known by sailors as The Doldrums, is the area encircling the earth near the equator where winds originating in the northern and southern hemispheres come together....

, a low-pressure area around the equator

Equator

An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

 where the prevailing winds

Prevailing winds

Prevailing winds are winds that blow predominantly from a single general direction over a particular point on Earth's surface. The dominant winds are the trends in direction of wind with the highest speed over a particular point on the Earth's surface. A region's prevailing and dominant winds...

 are calm. The low pressure is caused by the heat at the equator, which makes the air rise and travel north and south high in the atmosphere, until it subsides again in the horse latitudes

Horse latitudes

Horse Latitudes or Subtropical High are subtropical latitudes between 30 and 35 degrees both north and south. This region, under a ridge of high pressure called the subtropical high, is an area which receives little precipitation and has variable winds mixed with calm.The consistently warm, dry...

. Some of that air returns to the doldrums through the trade winds. This process can lead to light or variable winds and more severe weather, in the form of squalls, thunderstorms and hurricanes. The doldrums are also noted for calm periods when the winds disappear altogether, trapping sail-powered boats for periods of days or weeks.

When the winds are gone the sea actually has no swells, on a clear day the color of the sky is reflected in the water. At night the same effect, with no clouds or moon, gives one the effect of floating in space.

The term appears to arisen in the 18th century (when cross-Equator sailing voyages became more common). It is derived from dold (an archaic term meaning "stupid") and -rum(s), a noun suffix found in such words as "tantrum

Tantrum

A tantrum is an emotional outburst, usually associated with children or those in emotional distress, that is typically characterized by stubbornness, crying, screaming, yelling, shrieking, defiance, angry ranting, a resistance to attempts at pacification and, in some cases, violence...

".

Doldrums in literature

The Pacific doldrums were famously described in Samuel Taylor Coleridge

Samuel Taylor Coleridge

Samuel Taylor Coleridge was an English poet, Romantic, literary critic and philosopher who, with his friend William Wordsworth, was a founder of the Romantic Movement in England and a member of the Lake Poets. He is probably best known for his poems The Rime of the Ancient Mariner and Kubla...

's Rhyme of the Ancient Mariner in the following stanzas:

All in a hot and copper sky,

The bloody Sun, at noon,

Right up above the mast did stand,

No bigger than the Moon.


Day after day, day after day,

We stuck, nor breath nor motion;

As idle as a painted ship

Upon a painted ocean.