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ultrasonics

(Encyclopedia)ultrasonics, study and application of the energy of sound waves vibrating at frequencies greater than 20,000 cycles per second, i.e., beyond the range of human hearing. The application of sound energy...

almanac

(Encyclopedia)almanac, originally, a calendar with notations of astronomical and other data. Almanacs have been known in simple form almost since the invention of writing, for they served to record religious feasts...

Neptune, in astronomy

(Encyclopedia)Neptune, in astronomy, 8th planet from the sun at a mean distance of about 2.8 billion mi (4.5 billion km) with an orbit lying between those of Uranus and the dwarf planet Pluto; its period of revolut...

firefly

(Encyclopedia)firefly or lightning bug, small, luminescent, carnivorous beetle of the family Lampyridae. Fireflies are well represented in temperate regions, although the majority of species are tropical and subtro...

Theresa, Saint (Theresa of Lisieux)

(Encyclopedia)Theresa or Thérèse, Saint (Theresa of Lisieux), 1873–97, French Carmelite nun, one of the most widely loved saints of the Roman Catholic Church, b. Alençon. Her original name was Marie-Françoise...

acoustics

(Encyclopedia)acoustics əko͞oˈstĭks [key] [Gr.,=the facts about hearing], the science of sound, including its production, propagation, and effects. Various branches of acoustics that deal with different aspects...

Mercury, in astronomy

(Encyclopedia)Mercury, in astronomy, nearest planet to the sun, at a mean distance of 36 million mi (58 million km); its period of revolution is 88 days. Mercury passes through phases similar to those of the moon a...

heresy

(Encyclopedia)heresy, in religion, especially in Christianity, beliefs or views held by a member of a church that contradict its orthodoxy, or core doctrines. It is distinguished from apostasy, which is a complete ...

meteor

(Encyclopedia)meteor, appearance of a small particle flying through space that interacts with the earth's upper atmosphere. While still outside the atmosphere, the particle is known as a meteoroid. Countless meteor...

aurora borealis

(Encyclopedia)aurora borealis ôstrāˈlĭs [key], luminous display of various forms and colors seen in the night sky. The aurora borealis of the Northern Hemisphere is often called the northern lights, and the aur...