What is the "water hole"? Why is so promising to radio astronomers?
What will be an ideal response?
The "water hole" is the region of the radio spectrum between 18 cm (natural wavelength of the hydroxyl, OH, molecule and 21 cm (natural wavelength of atomic hydrogen, H). Hydroxyl and hydrogen combine to form water, and the 18- to 21-cm region of the spectrum is relatively free of background noise. Thus it is believed that the so-called "water hole" is a natural band for communication between galactic civilizations.
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Induced electric and magnetic fields produce
A) stronger electric or magnetic field. B) higher voltages produced by Faraday induction. C) both of these D) none of the above
As shown in the diagram, you've just thrown a baseball toward Al at 100 km/hr, while he is moving away from you to the right at 90 km/hr. According to Al, what is the baseball doing?
A) traveling to the right at 10 km/hr B) traveling to the right at 100 km/hr C) staying stationary D) traveling to the right at 190 km/hr
The ______________ temperature scale has no negative readings
Fill in the blank(s) with correct word
Evidence that there is a considerable amount of water frozen under the surface of Mars is provided by all of the following except
A. satellite measurements of water in the polar caps. B. discovery by the Mars rovers of chemicals in surface rocks formed in the presence of large amounts of water. C. squishy-looking flow patterns around crater impact sites. D. features resembling channels cut by flowing water. E. periodic eruptions of geysers when subsurface ice is melted by volcanic activity.