CDS (II) 2020 General Knowledge · Question 59 of 120

Correct — D, Uruguay. The Tropic of Capricorn lies at about 23 degrees 26 minutes south — its exact latitude is currently 23°26'09", and it is creeping north by roughly fifteen metres a year. Travelling eastward round the world it crosses Namibia, Botswana, South Africa, Mozambique, Madagascar, Australia and then, in South America, Chile, Argentina, Paraguay and Brazil. Uruguay is not on it. In fact Uruguay is one of only four countries in the world that lie wholly to the south of the Tropic of Capricorn, the others being Eswatini, Lesotho and New Zealand — so the country is not merely off the line, it is entirely outside the tropics.

• (a)Chile — The line crosses northern Chile, in the Atacama country inland from Antofagasta. It is on the Tropic, so it cannot be the answer to a question asking which is not.
• (b)Brazil — The Tropic crosses Brazil in the south-east, passing north of São Paulo, and Brazil is the last landmass it meets before the Atlantic.
• (c)Paraguay — The line runs through Paraguay between Chile-Argentina and Brazil, which is why the country is often described as half tropical and half subtropical.

The Tropic of Capricorn marks the southern limit at which the Sun can be directly overhead, which happens once a year at the December solstice. Its latitude is set by the tilt of the Earth's axis, and because that tilt varies slowly the line itself drifts — presently northward at about 0.47 arcseconds, or fifteen metres, a year. Together with the Tropic of Cancer it bounds the torrid zone; the belts between the tropics and the polar circles are the temperate zones.

Elimination on this item is a matter of latitude, not of country knowledge. Buenos Aires sits near 34 degrees south and Montevideo faces it across the Plate, so Uruguay's whole territory lies well south of 23 and a half degrees. Chile, Argentina, Paraguay and Brazil all stretch far enough north to be crossed. The strongest single fact to carry away is the four-country list — Eswatini, Lesotho, New Zealand and Uruguay lie entirely south of the Tropic — because it converts a map question into a recalled set.

• The Tropic of Capricorn currently lies at 23°26'09" south and is moving north at about fifteen metres a year.
• Going eastward it crosses Namibia, Botswana, South Africa, Mozambique, Madagascar, Australia, Chile, Argentina, Paraguay and Brazil.
• Uruguay, Eswatini, Lesotho and New Zealand are the only four countries lying wholly south of it.
• The Sun is overhead at the Tropic of Capricorn at the December solstice.
• The tropics are set by the tilt of the Earth's axis, which is why the line's position slowly changes.

• Assuming every South American country south of the Equator is crossed by the Tropic; Uruguay is not.
• Confusing the Tropic of Capricorn with the Tropic of Cancer when a question is set in the southern hemisphere.
• Treating the tropics as fixed lines; they move slowly with the Earth's tilt.

As a which-country-is-not item like this one, as a list of countries a tropic passes through, or through solstice geometry.

• practice — not a real PYQ

  On which date is the Sun directly overhead at the Tropic of Capricorn?

  • (a)21 March
  • (b)21 June
  • (c)23 September
  • (d)22 December

  Answer(d) 22 December — the December solstice, when the southern hemisphere has its longest day.

• practice — not a real PYQ

  Which one of the following African countries is crossed by the Tropic of Capricorn?

  • (a)Kenya
  • (b)Namibia
  • (c)Nigeria
  • (d)Ethiopia

  Answer(b) Namibia — the line also crosses Botswana, South Africa, Mozambique and Madagascar.