Space rocks1 often2 enter the Earth’s atmosphere. But they usually3 explode and burn4 before falling to the ground5. About 6 70 percent of our planet is covered with7 water. As a result8, most meteorites falling from the sky disappear9 on the oceans’ floor10. We would not know about them if it was not for an international agency.
Reporters gather around11 a piece of a
meteorite, which according to12 local authorities and
scientists, was lifted from13 the bottom14
of the Chebarkul Lake15 in Chelyabinsk,
Russia, Oct. 18, 2013.
You may16 remember the meteorite that exploded
last year 23 kilometers above17 Chelyabinsk, in
Russia.
Scientists estimate it was about
18 meters long18 before it fell to Earth19. They also think it had a mass20
of about 10,000 tons.
Many people would have died21 if the meteorite
fell in a populated area. Luckily22,
it did not. Instead23
it broke apart mid-air24 and most of the pieces fell
into Lake Chebarkul. But that is a
little too close25 for some people.
The Comprehensive26 Nuclear-Test-Ban
Treaty27 Preparatory Commission is a group based in Vienna,
Austria. It says the Earth is visited by
meteorites more often than we know.
The group records28 explosions made by
meteorites that enter Earth’s atmosphere.
Pierrick Mialle works for the commission, also known as29
the CTBTO. He is an acoustics
expert30, specializing in the study of sounds. He says since31
meteorites are sometimes32 entering the
atmosphere, they are creating loud air bursts33.
The commission controls sensors and other equipment that watch34
for possible violations of the Nuclear Test ban treaty. Some of the devices35 are
seismic, meaning36 they measure37 the
movement of the Earth. Others are
hydrostatic, meaning they measure the movement of the Earth’s water. The Commission also uses ultrasound and
radioactivity sensors.
Between38 2000 and 2013,
the CTBTO recorded 26 powerful39 explosions of large
meteorites entering the atmosphere. The B612 Foundation also studies meteorite
impacts. This group estimates at
least40 four of those 26 explosions were stronger than41
the nuclear bomb that destroyed Hiroshima.
In addition to42 loud noise43, explosions create low
frequency44 infrasound.
Sound waves45 can travel very long distances at
such46 low frequencies. But human beings47
are unable to hear them48. CTBTO stations as far
away as49 the Antarctica recorded the explosion of the Chelyabinsk
meteorite.
Mr. Mialle says listening stations50 operate anywhere
from51 four to 15 high-technology sensors. He says that the sensors work like large
microphones. “They are called micro barometer because they measure micro
fluctuations of the atmosphere. It’s
like a large microphone except52 there’s no membrane53.”
He adds that54 some of the explosions are hard
to identify55 immediately after56 they
are recorded. “For instance57, the first time we had
this, what was later called the Super Bolide of North Pacific, in the first few
weeks all that was known was a large event in the middle of the Pacific. But we didn’t know what it was.”
The commission keeps contact58 with other agencies,
such as59 the American space agency, that follow60
meteorites. Space agency
officials later confirmed that the mysterious explosion was caused by a
meteorite.
When complete, the CTBTO system will have 337 stations worldwide61. And these stations will be listening for
nuclear explosions and other loud sounds in the atmosphere. I’m Anna Matteo.
Vocabulary
- Space rocks = rochas espaciais
- often = frequentemente
- usually = normalmente
- burn = queimar
- before falling to the ground = antes de cair no chão
- About =
aproximadamente
- covered with =
coberto com
- As a result =
como resultado
- disappear =
disaparecem
- oceans’ floor
= fundo do oceano
- gather around
= reunem-se ao redor de
- according to =
de acordo com
- was lifted
from = foi erguido do
- bottom = fundo
- Lake = lago
- may = pode
(possibilidade)
- above = sobre
- long = de
comprimento
- fell to Earth
= caiu na Terra
- mass = massa
- would have
died = teriam morrido
- Luckily = por
sorte, felizmente
- Instead = ao
invés disso
- broke apart
mid-air = partiu-se no meio do ar
- too close =
perto demais
- Comprehensive
= abrangente
- Nuclear-Test-Ban
Treaty = tratado de proibição de testes nucleares
- records =
registra
- also known as
= também conhecido como
- acoustics
expert = especialista em acústica
- since = uma
vez que
- sometimes = as
vezes
- loud air
bursts = explosões de ar altas
- watch =
observam
- devices =
dispositivo
- meaning =
significando
- measure =
medir
- Between =
entre (duas coisas)
- powerful =
poderoso(a)
- at least =
pelo menos
- were stronger
than = foram mais fortes do que
- In addition to = além de
- noise = barulho
- low frequency = baixa frequencia
- Sound waves = ondas sonoras
- such = tais
- human beings = seres humanos
- unable to hear them = são incapazes de ouvi-las
- as far away as
= tão distantes quanto
- listening stations = estações de escuta
- anywhere =
algo em torno de (aproximadamente)
- except =
exceto
- there’s no
membrane = não há nenhuma membrana
- adds that =
acrescenta que
- hard to
identify = dificil de identificar
- immediately
after = imediatamente após
- For instance =
por exemplo
- keeps contact
= mantém contato
- such as = tais como
- follow = seguir
- worldwide = mundialmente