COSMIC PERSPECTIVE LL FD
9th Edition
ISBN: 9780135877074
Author: Bennett
Publisher: PEARSON
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Chapter 24, Problem 55EAP
SETI Signal. Consider a civilization broadcasting a signal with a power of 10,000 watts. The Arecibo radio telescope, which is about 300 meters in diameter, could detect this signal if it was coming from as far away as 100 light-years. Suppose instead that the signal is being broadcast from the other side of the Milky Way Galaxy, about 70,000 light-years away. How large a radio telescope would we need to detect this signal? (Hint: Use the inverse square law for light.)
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In a globular cluster, astronomers (someday) discover a star with the same mass as our Sun, but consisting entirely of hydrogen and helium. Is this star a good place to point our SETI antennas and search for radio signals from an advanced civilization?
Group of answer choices
No, because such a star (and any planets around it) would not have the heavier elements (carbon, nitrogen, oxygen, etc.) that we believe are necessary to start life as we know it.
Yes, because globular clusters are among the closest star clusters to us, so that they would be easy to search for radio signals.
Yes, because we have already found radio signals from another civilization living near a star in a globular cluster.
No, because such a star would most likely not have a stable (main-sequence) stage that is long enough for a technological civilization to develop.
Yes, because such a star is probably old and a technological civilization will have had a long time to evolve and develop there.
When Mars is 90 million km (9 x 10^10 m) from Earth, a) How long would it take for a radio wave from a video camera mounted on the back of a Mars Rover to tell ground control on earth that the Rover is about to go over a cliff? b) How long would it take for a radio signal from Earth to reach the Rover saying "STOP". c) Why do our Mars Rovers have to be "intelligent" enough to figure out how to deal with obstacles themselves?
The Apollo program (not the lunar missions with astronauts) being conducted at the Apache Point Observatory uses a 3.5 - m telescope to direct lasers at retro-reflectors left on the Moon by the Apollo astronauts. the Moon is 384, 472 km away approximately how long do the operators need to wait to see the laser light return to Earth? (Hint: The speed of light is 300,000 km/s.]
Chapter 24 Solutions
COSMIC PERSPECTIVE LL FD
Ch. 24 - Prob. 1VSCCh. 24 - Prob. 2VSCCh. 24 - Prob. 3VSCCh. 24 - Prob. 4VSCCh. 24 - Prob. 5VSCCh. 24 - Prob. 6VSCCh. 24 - Prob. 1EAPCh. 24 - Prob. 2EAPCh. 24 - Prob. 3EAPCh. 24 - Prob. 4EAP
Ch. 24 - How are laboratory experiments helping us study...Ch. 24 - Prob. 6EAPCh. 24 - Prob. 7EAPCh. 24 - Prob. 8EAPCh. 24 - Prob. 9EAPCh. 24 - Prob. 10EAPCh. 24 - Prob. 11EAPCh. 24 - Prob. 12EAPCh. 24 - Prob. 13EAPCh. 24 - Prob. 14EAPCh. 24 - Prob. 15EAPCh. 24 - Prob. 16EAPCh. 24 - Prob. 17EAPCh. 24 - For each of the following futuristic scenarios,...Ch. 24 - Prob. 19EAPCh. 24 - Prob. 20EAPCh. 24 - Prob. 21EAPCh. 24 - Prob. 22EAPCh. 24 - Prob. 23EAPCh. 24 - Prob. 24EAPCh. 24 - Prob. 25EAPCh. 24 - Prob. 26EAPCh. 24 - Choose the best answer to each of the following....Ch. 24 - Choose the best answer to each of the following....Ch. 24 - Choose the best answer to each of the following....Ch. 24 - Choose the best answer to each of the following....Ch. 24 - Choose the best answer to each of the following....Ch. 24 - Prob. 32EAPCh. 24 - Choose the best answer to each of the following....Ch. 24 - Prob. 34EAPCh. 24 - Choose the best answer to each of the following....Ch. 24 - Prob. 36EAPCh. 24 - The Turning Point. The end of this chapter...Ch. 24 - Prob. 39EAPCh. 24 - Prob. 43EAPCh. 24 - Prob. 45EAPCh. 24 - Prob. 46EAPCh. 24 - Prob. 47EAPCh. 24 - Prob. 48EAPCh. 24 - Prob. 49EAPCh. 24 - Prob. 50EAPCh. 24 - What’s Wrong with This Picture? Many science...Ch. 24 - Nearest Civilization. Suppose there are 10,000...Ch. 24 - SETI Search. Suppose there are 10,000...Ch. 24 - SETI Signal. Consider a civilization broadcasting...Ch. 24 - Prob. 56EAPCh. 24 - Prob. 57EAP
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- Think of our Milky Way Galaxy as a flat circular disk of diameter 100,000 light-years. Suppose we are one of 1000 civilizations, randomly distributed through the disk, interested in communicating via radio waves. How far away in light years would the nearest such civilization be from us on average? Show your working. (Hint: Begin by calculating the area of the disk. Find the area of one of a 1,000 squares. Consider the separation of the centres of two adjacent squares.)arrow_forwardSuppose there are 9000.0 civilizations broadcasting radio signals in the Milky Way Galaxy at the moment. On average, how many stars would have to be searched before a signal is heard? Assume that there are 8 × 1011 stars in the Galaxy and one civilization per star.arrow_forwardTutorial A radio broadcast left Earth in 1925. How far in light years has it traveled? If there is, on average, 1 star system per 400 cubic light years, how many star systems has this broadcast reached? Assume that the fraction of these star systems that have planets is 0.30 and that, in a given planetary system, the average number of planets that have orbited in the habitable zone for 4 billion years is 0.85. How many possible planets with life could have heard this signal? Part 1 of 3 To figure out how many light years a signal has traveled we need to know how long since the signal left Earth. If the signal left in 1925, distance in light years = time since broadcast left Earth. d = tnow - tbroadcast d = light years Submit Skip (you cannot come back)arrow_forward
- Tutorial A radio broadcast left Earth in 1923. How far in light years has it traveled? If there is, on average, 1 star system per 400 cubic light years, how many star systems has this broadcast reached? Assume that the fraction of these star systems that have planets is 0.50 and that, in a given planetary system, the average number of planets that have orbited in the habitable zone for 4 billion years is 0.40. How many possible planets with life could have heard this signal? Part 1 of 3 To figure out how many light years a signal has traveled we need to know how long since the signal left Earth. If the signal left in 1923, distance in light years = time since broadcast left Earth. d = tnow - broadcast d = 97 97 light years Part 2 of 3 Since the radio signal travels in all directions, it expanded as a sphere with a radius equal to the distance it has traveled so far. To determine the number of star systems this signal has reached, we need to determine the volume of that sphere. V, = Vb…arrow_forwardIf you could search for life in the galaxy shown in this image, would you look among stars in the disk, in the central bulge, in the halo, or in all of those places? Discuss the factors that influence your decision.arrow_forwardSuppose astronomers discover a radio message from a civilization whose planet orbits a star 35 lightyears away. Their message encourages us to send a radio answer, which we decide to do. Suppose our governing bodies take 2 years to decide whether and how to answer. When our answer arrives there, their governing bodies also take two of our years to frame an answer to us. How long after we get their first message can we hope to get their reply to ours? (A question for further thinking: Once communication gets going, should we continue to wait for a reply before we send the next message?)arrow_forward
- Would a human have been possible during the first generation of stars that formed right after the Big Bang? Why or why not?arrow_forwardMost of the stars we can see with the unaided eye in our night sky are hundreds or even thousands of lightyears away from Earth. (The very closest ones are only a few dozen lightyears away, but most are much further.) The vast majority of stars in our galaxy are many tens of thousands of lightyears away. IF intelligent life existed on planets orbiting some of these stars – and that’s a huge IF! – comment on the likelihood and practicality of (a) visiting, (b) communicating with, or (c) verifying the existence of those life forms. Describe how you might go about approaching EACH of these three tasks, or if you think they are even possible. (One or two sentences for each part would be appropriate.)arrow_forwardYou record the spectrum of a distant star using a telescope on the ground on Earth. Upon analysing the spectrum, you discover absorption lines spaced at intervals typical of oxygen atoms. Which of the following are possible interpretations of this evidence? Select all that apply. The width of the spectral lines gives the diameter of the star The star is likely orbited by habitable planets with breathable atmospheres. The height of the spectral lines above the star's general blackbody spectral curve tells us how much oxygen is in the star The atmosphere of Earth contains oxygen The red or blueshift of the set of lines can tell us the speed of the star's motion toward or away from usarrow_forward
- If you detected radio signals with an average wavelength of 37 cm and suspected that they came from a civilization on a distant Earth-like exoplanet, roughly how much of a change in wavelength (in cm) should you expect to detect as a result of the orbital motion of the distant exoplanet? (Hint: Use the Doppler shift formula.) (Note: Earth's orbital velocity is 30 km/s.) cmarrow_forwardSuppose that stars were born at random times over the last 1010 years. The rate of star formation is simply the number of stars divided by 1010 years. The fraction of stars with detected extrasolar planets is at least 11 %. The rate of star formation can be multiplied by this fraction to find the rate planet formation. How often (in years) does a planetary system form in our galaxy? Assume the Milky Way contains 3 × 1011 stars.arrow_forwardPlanetary Nebula Age. Suppose a planetary nebula is 1 pc in radius. If the Doppler shifts in its spectrum show it is expanding at 20 km/s, how old is it? (Note that 1 pc equals 3.1x1013 km, and 1 year equals 3.2x107 seconds, to two significant figures.) Please round your answer to two significant digits. At = yearsarrow_forward
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