the longest period of daylight.

(N hemisphere - June. 21)

the shortest period of daylight.

(N hemisphere - Dec. 21)

in the fall

(N hemisphere - Sept. 22)

in the spring.

(N hemisphere - Mar. 21)

-discover by Aristotle

-earth was the center of universe

-discovered by Copernicus

-sun was the center of the universe.

-device developed by Ancient Egyptians

-invented to chart astronomical position and predict the movement of stars.

-also invented by the Ancient Egyptians.

-to measure the star's height above the horizon.

-was invented in the 14th century (Levi ben Gurson)

-to measure the angle between the Moon and any given star.

-was invented in the late 16th century

-revealed details about the Earth's closest planetary neighbours, and showed the existence of the other neighbours in our solar system.

-used for measuring "local" distances, inside our solar system.

-AU is ewual to the average distance of distance from the centre of the Earth to the centre of the Sun (149 599 000 km).

-it equals the distance that light travels in one year.

-used to measure the distances between stars and galaxies.

-when you look into space at an object yuou are seeing it as it was at an earlier time.

-it takes time for the light from the object to travel to Earth across the great distance in space.