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

How many leap seconds have been added to UTC since the system began in 1972?

A) 9

B) 15

C) 22

D) 27

Answer · why

D) 27

The most recent was on 31 December 2016, and UTC now trails International Atomic Time by 37 seconds. Metrologists voted in 2022 to stop adding them by...

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) A typesetting error in 1963 was never corrected

B) The C stands for a French council that no longer exists

C) It was originally Universal Time, Coordinated

D) Standards bodies wanted one abbreviation usable in every language

Answer · why

D) Standards bodies wanted one abbreviation usable in every language

English speakers wanted CUT and French speakers TUC; UTC matched the existing pattern of UT0, UT1 and UT2 and satisfied nobody equally, which is how i...