Hover or tap underlined Spanish terms to see their translation and exam tip.
El Tiempo Universal es:Universal Time (UT) is defined astronomically as:
Show the answer
Correct answer: c) The Greenwich hour angle of the mean Sun, expressed in hours, plus 12 hours.
Why it is correct
Because the Greenwich hour angle of the mean Sun (GHAm) is reckoned from mean noon (upper transit at Greenwich) whereas the civil/UT day begins at midnight (lower transit, 12 hours earlier), Universal Time is UT = GHAm (in hours) + 12 h.
Why the others are not
- a) Sidereal hour angle is measured from Aries, not from the Greenwich meridian.
- b) GHAm without adding 12 hours is mean solar time reckoned from noon.
- d) UT is governed by the fictitious mean Sun (uniform motion), not the true Sun.
How to work it out in the exam
- Universal Time: UT = Greenwich hour angle of the mean Sun (in hours) + 12 h.
Where this question comes from
- Junta de Andalucía · 2016 · 1ª convocatoria · CY Módulo de navegación · question 2 Official paper · Official answer key
Pending instructor review. Machine translation, not reviewed.