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Witnesses to a meteor in Australia in 1978 claimed to have heard strange noises as it streaked overhead. Yet, given that the meteor was 30 kilometers up, if these sounds had come directly from the meteor, people on the ground could not have heard them until almost a minute after the meteor had disappeared. Physicist Colin Keay hypothesized that the light given off by a meteor’s trail must be accompanied by invisible electromagnetic radiation in the form of very low frequency (VLF) radio waves. Such waves, which travel at the speed of light, would reach the observer when the meteor itself came into view.
Subsequent experiments in a soundproof chamber showed that many things can act as transducers to convert VLF waves into audible vibrations. Aluminum foil, thin wires, pine needles, or dry hair all responded to a VLF field. VLF waves induce small charges in such objects, thereby causing them to vibrate in time with the waves’ oscillation. This transducer effect would explain why some people heard the noises while others close by heard nothing. Those who heard sounds were simply nearer to transducers. It could also explain why attempts to record meteor sounds have failed: scientists carefully place their microphones away from possible sources of interference.
[数学 ]猴哥112 -8832
WEATHER FORECAST FOR NOVEMBER 24
[阅读&逻辑 ]经典真题260篇 -8830
Which of the following statements best describes the function of the highlighted sentence in the context of the passage as a whole?
[阅读&逻辑 ]经典真题260篇 -8831
In the context in which it appears, “formula” most nearly means
[阅读&逻辑 ]经典真题260篇 -8829
The passage implies which of the following about the introduction of floral-patterned rugs in Timurid royal courts?
[阅读&逻辑 ]经典真题260篇 -8828
According to the passage, after the 1440s, Timurid paintings of court scenes
[阅读&逻辑 ]经典真题260篇 -8827
Which of the following, if true, provides the most support for the argument?
[阅读&逻辑 ]经典真题260篇 -8826
Which of the following, if true, most strengthens the argument?
[阅读&逻辑 ]经典真题260篇 -8825
With which of the following statements about Impressionist painting would the author of the passage be most likely to agree?
[阅读&逻辑 ]经典真题260篇 -8824
The “tradition” refers to the
[阅读&逻辑 ]经典真题260篇 -8823
The primary purpose of the passage is to
[阅读&逻辑 ]经典真题260篇 -8822
The passage is primarily concerned with
[阅读&逻辑 ]经典真题260篇 -8821
The “hypothesis” implies that compared to marine invertebrate larvae that subsist on stored nutrients, marine invertebrate larvae that feed are less likely to
[阅读&逻辑 ]经典真题260篇 -8820
The passage suggests that the “bryozoan,” the “barnacle species,” and “Capitella worms” all share which of the following characteristics?
[阅读&逻辑 ]经典真题260篇 -8819
It can be inferred from the passage that if Keay’s proposed explanation of meteor sounds is correct, it is true that
[阅读&逻辑 ]经典真题260篇 -8818
The passage suggests that Keay formulated his hypothesis in response to
[阅读&逻辑 ]经典真题260篇 -8817
Which of the following best describes the function of the highlighted sentence?
[阅读&逻辑 ]经典真题260篇 -8816
According to the passage, the disappearance after 1993 of known evening bat roosts in buildings suggests which of the following?
[阅读&逻辑 ]经典真题260篇 -8815
The author mentions the fact that evening bats radio-tracked since 1993 have roosted in trees primarily in order to
[阅读&逻辑 ]经典真题260篇 -8814
According to the passage, payments to wage laborers in the early United States were
[阅读&逻辑 ]经典真题260篇 -8813
The passage suggests which of the following about records of payments for outwork?