AST 105IN ANSWERS TO ASSIGNMENT 7Chapter 4, “The Habitability of Earth”Does it Make Sense?21. Not sensible. The fossil record and our understanding of the fossilization process make it clear that very,very few plants and animals leave fossils.22. Nearly all? I’m not sure I get the authors here, but I expect they mean this to be sensible. All the rocks of aformer lava flow should be igneous, unless the is so very old that erosion might have led to somesedimentary rock in lower areas. But the Hawaiian Islands are not that old. On the other hand, I’ve neverbeen there. Perhaps I’m splitting hairs, but I am writing down my thoughts for you to follow along mythinking and realize that life may seem obvious to us, but not when one begins to pay closer attention. Thewillingness to look for the details is what separates the critical thinker from the ideologue.23. Sensible. They are sedimentary, simply put. Near the top of the North Rim one can readily discern thewhite limestone layer. Limestone is a sedimentary rock made in former sea and ocean bottoms.24. This is not sensible. Like learning that up is up and down is down, but in other planetary systems up isdown and down is up...What!? This brings out a further point, not so metaphorical/rhetorical as my first.An important inference we have learned from our studies of the universe is that the laws of physics areuniversal. They work here and everywhere else, we have no reason to doubt this. The authors’ statementimplies otherwise, making it an extraordinary claim requiring you-should-know-what.25. Not sensible. While bombardment over the long term was severe by today’s standards, the rate ofbombardment was not nearly so high as implied by this statement. However, there is fuzziness here. Thereis a finite chance that a person dropped on the surface at this time period would die prematurely by theeffects of an impact some years or decades later.28. Makes complete sense. More greenhouse gas; more heat trapping. It’s the basic logic behind globalwarming. The only relevant change of any extent over the past couple centuries is the great increase in CO2released by humans since the onset of the Industrial Revolution in the early 1800's. Makes you wonder whyglobal warming deniers exist. Where does the science pertaining to global warming escape their grasp?Quick Quiz31. c32. c33. b34. b35. a36. c37. a38. c40. aQuantitative Problems49. a. 25,000 y vs. 100,000 y; therefore the second time frame is 75,000 years longer than the firstb. 4 million y vs. 0.05 billion years, the latter translating to 50 million years (50,000,000); thereforethe second time frame 46 million years (46,000,000) longer than the first. More help: million is athousand x thousand; billion is a thousand times a million. So, just substitute 1000 million for theword billion and 0.05 billion is 0.05 x 1,000 million, or 50 million years.c. 0.1 billion vs. 1 million years...Once again, we use the fact that one billion is 1000 million, so atenth of a 1000 million is 100 million, which is 99 million years (99,000,000) more than 1 millionyears50. From the Cosmic Calculation 4.1 section, the age, t, equals the half-life of the isotope used to date therock times the log (to the base 10) of the current-to-original-amount ratio divided by the log of the half-lifeamount of isotopes compared to the original amount, or ½. 10a. We are given the current-to-original-amount ratio to be 55/100. Take the log of 0.55 to get -10-0.2596 and divide it by the log 0.5 (= -0.3010) to get the portion or number of half-lives. In thiscase, you get 0.8625 half-lives. With one half-life equaling 4.5 billion years, then the age of thisrock from the lunar highlands is 3.9 billion years (3,900,000,000 years).51. Same math here, too. Different isotope with a half-life of 5,700 years. C-14 is probably the most famousisotope since it is so convenient for measuring the ages of plant, animal, and human remains over the past50,000 years.10a. First, we obtain the log of 0.77, which yields -0.1135, divide by log 0.5, (= -0.3010) to get 0.38 ofone half-life or 2,150 years age.1052. Identical methodology of Problems 50 thru 51b. The log of 0.94 is -0.0269, which, when divided by -0.3010equals 0.0893 of one half-life, (=14 billion years). This results in 1.25 billion