Virtually
everything astronomers known about objects outside the solar system is based on
the detection of photons—quanta of electromagnetic radiation. Yet there is
another form of radiation that permeates the universe: neutrinos. With (as its
name implies) no electric charge, and negligible mass, the neutrino interacts
with other particles so rarely that a neutrino can cross the entire universe,
even traversing substantial aggregations of matter, without being absorbed or
even deflected. Neutrinos can thus escape from regions of space where light and
other kinds of electromagnetic radiation are blocked by matter. Furthermore,
neutrinos carry with them information about the site and circumstances of their
production: therefore, the detection of cosmic neutrinos could provide new
information about a wide variety of cosmic phenomena and about the history of
the universe.
But how can
scientists detect a particle that interacts so infrequently with other matter?
Twenty-five years passed between Pauli’s hypothesis that the neutrino existed
and its actual detection: since then virtually all research with neutrinos has
been with neutrinos created artificially in large particle accelerators and
studied under neutrino microscopes. But a neutrino telescope, capable of
detecting cosmic neutrinos, is difficult to construct. No apparatus can detect
neutrinos unless it is extremely massive, because great mass is synonymous with
huge numbers of nucleons (neutrons and protons), and the more massive the
detector, the greater the probability of one of its nucleon’s reacting with a
neutrino. In addition, the apparatus must be sufficiently shielded from the
interfering effects of other particles.
Fortunately, a
group of astrophysicists has proposed a means of detecting cosmic neutrinos by
harnessing the mass of the ocean. Named DUMAND, for Deep Underwater Muon and
Neutrino Detector, the project calls for placing an array of light sensors at a
depth of five kilometers under the ocean surface. The detecting medium is the
seawater itself: when a neutrino interacts with a particle in an atom of
seawater, the result is a cascade of electrically charged particles and a flash
of light that can be detected by the sensors. The five kilometers of seawater
above the sensors will shield them from the interfering effects of other
high-energy particles raining down through the atmosphere.
The strongest
motivation for the DUMAND project is that it will exploit an important source
of information about the universe. The extension of astronomy from visible
light to radio waves to x-rays and gamma rays never failed to lead to the
discovery of unusual objects such as radio galaxies, quasars, and pulsars. Each
of these discoveries came as a surprise. Neutrino astronomy will doubtless
bring its own share of surprises.
Questions:
1. Which
of the following titles best summarizes the passage as a whole?
(A) At the
Threshold of Neutrino Astronomy
(B) Neutrinos
and the History of the Universe
(C) The
Creation and Study of Neutrinos
(D) The DUMAND
System and How It Works
(E) The
Properties of the Neutrino
2. With
which of the following statements regarding neutrino astronomy would the author
be most likely to agree?
(A) Neutrino
astronomy will supersede all present forms of astronomy.
(B) Neutrino
astronomy will be abandoned if the DUMAND project fails.
(C) Neutrino
astronomy can be expected to lead to major breakthroughs in astronomy.
(D) Neutrino
astronomy will disclose phenomena that will be more surprising than past
discoveries.
(E) Neutrino
astronomy will always be characterized by a large time lag between hypothesis
and experimental confirmation.
3. In
the last paragraph, the author describes the development of astronomy in order
to
(A) suggest
that the potential findings of neutrino astronomy can be seen as part of a
series of astronomical successes
(B) illustrate
the role of surprise in scientific discovery
(C) demonstrate
the effectiveness of the DUMAND apparatus in detecting neutrinos
(D) name some
cosmic phenomena that neutrino astronomy will illuminate
(E) contrast
the motivation of earlier astronomers with that of the astrophysicists working
on the DUMAND project
4. According
to the passage, one advantage that neutrinos have for studies in astronomy is
that they
(A) have been
detected for the last twenty-five years
(B) possess a
variable electric charge
(C) are usually
extremely massive
(D) carry
information about their history with them
(E) are very
similar to other electromagnetic particles
5. According
to the passage, the primary use of the apparatus mentioned in lines 24-32 would
be to
(A) increase
the mass of a neutrino
(B) interpret
the information neutrinos carry with them
(C) study the
internal structure of a neutrino
(D) see
neutrinos in distant regions of space
(E) detect the
presence of cosmic neutrinos
6. The
passage states that interactions between neutrinos and other matter are
(A) rare
(B) artificial
(C)
undetectable
(D)
unpredictable
(E) hazardous
7. The
passage mentions which of the following as a reason that neutrinos are hard to
detect?
(A) Their
pervasiveness in the universe
(B) Their
ability to escape from different regions of space
(C) Their
inability to penetrate dense matter
(D) The
similarity of their structure to that of nucleons
(E) The
infrequency of their interaction with other matter
8. According
to the passage, the interaction of a neutrino with other matter can produce
(A) particles
that are neutral and massive
(B) a form of
radiation that permeates the universe
(C) inaccurate
information about the site and circumstances of the neutrino’s production
(D) charged
particles and light
(E) a situation
in which light and other forms of electromagnetic radiation are blocked
9. According
to the passage, one of the methods used to establish the properties of
neutrinos was
(A) detection
of photons
(B) observation
of the interaction of neutrinos with gamma rays
(C) observation
of neutrinos that were artificially created
(D) measurement
of neutrinos that interacted with particles of seawater
(E) experiments
with electromagnetic radiation
Answers:
|
1.
A
|
2.
C
|
3.
A
|
4.
D
|
5.
E
|
|
6.
A
|
7.
E
|
8.
D
|
9.
C
|
|
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