Contrast the difficulty in contacting extraterrestrial life using space flight and radio communication. How might each be done? What are the advantages and limitations of each?
What will be an ideal response?
Space flight to the nearest star would take thousands of years with current technology. Without some major breakthrough, interstellar space flight is totally impractical. Radio communication is possible and marginally feasible. Earth has been broadcasting at radio wavelengths since the 1920s. If another civilization is both nearby and listening, a response could already be on the way. The limitation is that conversations would be very slow with a turnaround time of decades or even centuries.
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Optical density is directly proportional to
A) mass density. B) light speed. C) index of refraction. D) index of reflection.
As a radio source, the period of "pulsar Earth" is
A) 30 minutes. B) 23 hours, 56 minutes. C) 24 hours. D) 29.5 days. E) 365.25 days.
In a completely inelastic collision between two objects where the mass of one is double that of the other, which of the following statements is always true?
a. The larger mass will always lose kinetic energy. b. The smaller mass will always gain kinetic energy. c. The momentum of the smaller mass will have a larger magnitude change than that of the larger mass. d. Not even one of the above statements is true.
Drumlins are made of
A) bedrock. B) ice. C) drift. D) striations.