Page 348 - NS-2 Textbook

344 GLOSSARY

pulse to make a round trip to the sea bottom and KEEL-central longitudinal beam of a ship from which
back. the frames and hull plating rise.
ECLIPSE-the cutting off of light from one celestial KILOGRAM -51 unit of mass.
body by another. LIGHT YEAR-the distance light travels in a year.
ECOSYSTEM -a system of plants and animals and their MACH NUMBER-the ratio of the speed of an object to
environment. the speed of sotmd in the surrounding medium.
ELECTRIC CIRCUIT -a continuous path through which MAGNETIC FIELD-a region of space near a magne-
electricity can flow. tized body where magnetic forces can be detected.
ELECTRIC CURRENT -a flow of charged particles. MAGNETOSPHERE-an asymmetric region surround-
ELECTROMAGNETIC WAVE-nonmaterial wave con- ing a planet in which charged particles are trapped by
sisting of oscillating electric and magnetic fields that the planet's magnetic field.
move at the speed of light through space. MASS-quantity of material present, measured in kilo-
ELECTRONIC COUNTERMEASURES-the use of elec- grams in the 51 system.
tronics to reduce the effectiveness of enemy electronic MECHANICAL WAVE-wave consisting of periodic
equipment. Now often called electronic attack (EA) motion of matter.
measures. MEDIUM-the environment or substance through
ELECTRONIC WARFARE-aspect of warfare concerned which a vvave travels.
with the use of electronic equipment and sensors.
MESOSPHERE-the portion of Earth's atmosphere from
ELLIPSE-a closed curve that is formed from two foci or
about 20 to 50 miles above the surface.
points in which the sum of the distances from any
METEOR-the luminous phenomenon seen when a me-
point on the curve to the two foci is a constant.
teoroid enters the atmosphere, commonly known as a
ESTUARY -an area of the sea that extends inland to
shooting star.
meet the mouth of a river.
METEORITE-a part of a meteoroid that survives
FATHOM-unit of depth equal to 6 feet.
through Earth's atmosphere.
FLUID-a material that flows: liquid, gases, and plasmas.
METEOROID-a small rock in space.
FREE FALL-the unconstrained motion of a body sub-
MILLIBAR-I/I,OOO of a bar; the standard sea-level
ject only to a gravitational force.
pressure is about 1,013 millibars.
FREQUENCY-number of occurrences or cycles per
NEBULA -a diffuse mass of interstellar gas or dust.
unit time.
NET FORCE-vector sum of forces on an object.
GEOSYNCHRONOUS SATELLITE-a satellite whose
NEWTON-51 unit of force, equal to about a fifth of a
orbital velocity is matched to the rotational velocity
pOlmd.
of the planet; it appears to hang motionless above one
NOVA-an exploding star that increases in brightness
position over the planet's surface.
due to internal explosions.
G FORCE-an apparent force generated by an accelera-
OHM-51 unit of electrical resistance.
tion maneuver" either lineal' or in a curved pathl mea-
OHMMETER-an instrument to measure electrical re-
sured in g's, or multiples of the force of Earth's grav-
sistance.
ity at sea level (9.S m/s2 or 32 ft/s2).
ORBIT -the path of an object that is moving around a
GRADIENT -a rate of inclination or slope.
second object or point.
GULF-a large body of salt water, almost surrounded by
land. OZONE LAYER-a layer of Earth's atmosphere be-
GYRE-a circular pattern of ocean current. tween 10 and 20 miles in altitude that contains a high
HERTZ (Hz)-unit of frequency equal to one cycle per concentration of solar radiation-absorbing ozone.
second. PERIOD-time required for one complete cycle of an
HULL-the body or shell of a ship or seaplane. event to occur.
ICBM -intercontinental ballistic missile. PHOTOELECTRIC -electrical effects caused by illumi-
IGNEOUS ROCK-rock formed by solidification from a nation.
molten state. PHOTOSPHERE-the visible surface of the Stm.
INSULATOR-a material through which the flow of PITCH -the frequency of a sOlmd.
electrical charge is greatly impeded. PLANE OF THE ECLIPTIC-the plane containing
IONOSPHERE-an electrically conducting set of layers Earth's orbit around the Sun.
of Earth's atmosphere, extending from about 30 to POWER -the rate of doing work, expressed in watts in
more than 250 miles above the surface. the 51 system.
JET STREAM-a high-speed wind near the upper tro- PPI SCOPE-plan position indicator radar scope; a
posphere, generally moving from a westerly direction radar screen that presents a chartlike picture of the
at speeds above 200 mph. surrounding land and sea.