时间:2018-12-31 作者:英语课 分类:英语听力文摘 English Digest


英语课

   A Stationary 1 Satellite, part 2


 
  A geostationary satellite orbitsthe planet at the same rate as the planet rotates, so the satellite is always over the same patch of ground.
 
  Cool! you say. I’d like to have one of those about twenty feet over my house. Sadly, geos only work easily at one distance: 22,500 miles up.Why is that?
 
  Other satellites can have different orbits, can’t they?
 
  Yes, they can. But that’s because they can also move at different speeds. A geo doesn’t have that option — by definition it must orbit at the same speed as the earth turns. And that speed determines how high up it must be!
 
  A satellite has to move at a certain speed to balance out gravity; otherwise it won’t stay in orbit. Now, a geo must move at the speed the earth turns. If you put it in a very low altitude, that speed wouldn’t be enough to balance gravity.
 
  Go higher, though, and gravity gets weaker. At 22,500 miles, gravity will be just weak enough so that a satellite moving at the speed of the earth’s rotation 2 will stay in orbit without help.
 
  Of course, if you wanted to have a geo at a different altitude, you could always attach rockets to it and have them push continuously. But that’s a pretty expensive option. At 22,500 miles, nothing else is required.

adj.固定的,静止不动的
  • A stationary object is easy to be aimed at.一个静止不动的物体是容易瞄准的。
  • Wait until the bus is stationary before you get off.你要等公共汽车停稳了再下车。
n.旋转;循环,轮流
  • Crop rotation helps prevent soil erosion.农作物轮作有助于防止水土流失。
  • The workers in this workshop do day and night shifts in weekly rotation.这个车间的工人上白班和上夜班每周轮换一次。
学英语单词
Altenglan
Anemone erythrophylla
apprecations
aristopedia
Austvaagoy
belostomatidaes
brothel creeper
by pass cock
cancelations
chemstaxis
coach-player
cobalt-cabrerite
coefficient of heterogeneity
collective-electric telephone
consumer durable
court of appeals
cryptopart
db-loss
Dehydrosfilbestrol
dicksoniaceaes
direct labo(u)r cost method
disaccustomed
discretionary clause
doillon
drug interdiction
electronic computing circuit
electronic integration effect
enter serial number
excess reserve fund
first-grader
flame ionization gauge
fluidextractum ehei
fraunce
generalized data translator
government regulation
gravitational acceleration
hyphonate
identifiably
Impugan
Inabanga
inclear
induced displacement
induced sporulation
inference of law
infinitely variable speed drive
inswingings
jewing down
liguliform
lz compression
machine word
material cost
maximum permissble load
military psychiatry
mitiphyllin
monoclonal cryoglobulin
mowed down
Muskhogean language
nasuwts
noble spirit
non-evolutional
nonfinal state
nontrivial function
odontologists
Olosed
on-demand time sharing
one-electron theory
Ouray County
oxanthranol
plurality correlation
practice low approach
pre-embodiment
pseudo-congruence
psychogeographically
pyrenolichen
Pyrrosia
quito y pon dantza (spain)
raptophile
regular convex solids
repulsive mineral
ricefishes
sea-water distillator
search query
second sourcing
short-pitman mower
soil distribution
Spence Bay
spheroidal hypercylinder
spirit rapping
standard assessment task
standard fee
sudden-acceleration
supporting reflex
theoretical ash
Torreglia
Trapeang Rung
ultraviolet rotational band
unkingdomed
unsensuous
variation tone
Villafranca del Campo
water tube gas condenser
Wismuthspiegel