Q 01/05

Since 1967 the second has been defined by the radiation frequency of an atom of which element?

A) Rubidium

B) Hydrogen

C) Caesium

D) Strontium

Answer · why

C) Caesium

The definition counts 9,192,631,770 periods of caesium-133 radiation. Optical clocks based on strontium and aluminium ions are now more precise, so th...

Q 02/05

The name for the 60th division of a minute comes from the Latin pars minuta secunda, meaning what?

A) Two-part minute

B) Second hand

C) Second small part

D) Half a minute

Answer · why

C) Second small part

The minute was the pars minuta prima, the first small division of the hour into 60 parts; dividing again by 60 gave the second small part.

Q 03/05

Leap seconds are added to Coordinated Universal Time to keep it in step with what?

A) Earth's orbit of the Sun

B) Earth's rotation

C) The Moon's orbit

D) GPS satellite clocks

Answer · why

B) Earth's rotation

Earth's rotation. It varies unpredictably, and the extra second added in June 2012 locked up servers at sites including Reddit.

Q 04/05

Which year is the longest on record, at 31,622,402 seconds, because it had 366 days and two leap seconds?

A) 1996

B) 1984

C) 1972

D) 2016

Answer · why

C) 1972

1972 was the first year of leap seconds and got two of them, in June and December, on top of being a leap year.

Q 05/05

Why is Coordinated Universal Time abbreviated UTC rather than CUT?

A) It follows the French word order

B) A typo in a 1960s report stuck

C) A compromise between English and French

D) It copies a Latin phrase

Answer · why

C) A compromise between English and French

A compromise between English and French: English speakers would say CUT and French speakers TUC, so one code was chosen for every language.