Q 01/05

In which US state can a sundial's upright pointer cast no shadow at noon on two days a year?

A) Florida

B) Hawaii

C) Texas

D) Arizona

Answer · why

B) Hawaii

Hawaii is the only state south of the Tropic of Cancer, so the noon Sun can stand straight overhead there twice a year, a moment named Lahaina Noon.

Q 02/05

By what angle does the Sun appear to swing around the sky each hour?

A) 1.5°

B) 5°

C) 15°

D) 45°

Answer · why

C) 15°

15°, near enough: a full 360° circuit takes 24 hours, which is also why each ideal time zone spans 15 degrees of longitude.

Q 03/05

For a sundial to be accurate all year, its style must be parallel to what?

A) The local horizon

B) Earth's rotational axis

C) The line to magnetic north

D) The plane of the ecliptic

Answer · why

B) Earth's rotational axis

Earth's rotational axis: set that way, the style's shadow turns at the same rate in every season, so the dial can mark equal hours all year.

Q 04/05

What must a horizontal sundial's style angle above the horizontal equal?

A) The Sun's declination

B) The axial tilt of 23.5°

C) The local longitude

D) The local latitude

Answer · why

D) The local latitude

The local latitude, so a dial built for London keeps poor time in Cairo until it is tilted by the difference between the two latitudes.

Q 05/05

What is a sundial's single time-telling point, such as a style's tip, called?

A) Dial centre

B) Nodus

C) Substyle

D) Meridian

Answer · why

B) Nodus

Nodus: its shadow falls on a different curve in each season, so a dial with one can show the date as well as the hour.