What is the radio window astronomers use to search for alien transmitted communication? What is this window nicknamed?
What will be an ideal response?
Between 1cm to 30 cm wavelengths is a radio window that is open for communication. Even this restricted window contains millions of possible radio-frequency bands and is too wide to monitor easily, but astronomers may have thought of a way to narrow the search. Within this broad radio window lie the 21-cm spectral line of neutral hydrogen and the 18-cm line of OH. The interval between those lines has especially low background interference and is named the water hole because H plus OH yields water.
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If a fish looks upward at 45° to a pond's water's surface, it will see
A) the pond's bottom. B) the sky and possibly some tall surroundings. C) only the water's surface. D) none of the above
A 50-kg satellite circles planet Cruton every 5.6 h in an orbit with a radius of 12 × 10^6 m. What is the magnitude of the gravitational force on the satellite by planet Cruton?
a. 63 N b. 58 N c. 68 N d. 73 N e. 50 N
Radioactive Decay: Today, uranium contains 0.72% 235U (half-life = 0.70 billion years) and 99.28% 238U (half-life = 4.5 billion years). At a time 1.9 billion years ago, what was the fraction of 235U in uranium?
A. 3.53% B. 4.72% C. 4.90% D. 6.75%
The type of nuclear reactor used in the United States was originally developed
A) during the Manhattan project. B) in Canada. C) as part of the H-bomb program. D) by private industry. E) for submarines.