Jun 27, 2004 5:00 AMNov 12, 2019 6:37 AM


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Man vs. the Machine

I am very disappointed by your conclusion that we need manned spacecraft going to Mars [“Time to Put a Foot Down,” Letter From Discover, April]. Do the arithmetic: It costs $400 million for a robot versus as much as $400 billion for a person. That means one manned flight could cost the equivalent of 1,000 robotic flights! We now lose two out of three robotic crafts due to accidents and engineering flaws. If you put a human on board, the luxury of losing two out of three crafts disappears. So does the luxury of mostly disregarding the near vacuum and the subzero working conditions and not having to transport life-support equipment. If you think that maneuvering a robot on Mars is difficult, don’t even think about manned flights to Mars. The complexity goes up by orders of magnitude, and your bang for the buck goes straight down the toilet. I once designed automatic flight-control systems for commercial aircraft. Ninety-nine percent of the engineering and testing went into keeping passengers alive and comfortable. That left 1 percent to fly the plane. The day will come when the technology exists to make manned flight to Mars economically viable. For now, just sit back and be patient.


Phoenix, Arizona

Morality in the Balance

The article on philosopher Joshua Greene [“Whose Life Would You Save?” April] asked, “If right and wrong are nothing more than the instinctive firing of neurons, why bother being good?” The more relevant question is, If right and wrong are nothing more than the instinctive firing of neurons, then does good even exist? The direction of Greene’s research seems to be saying that it makes no difference how we respond to moral dilemmas: “Evil doesn’t exist on a neuronal level,” he says. If evil does not exist, then it is impossible to say that something is wrong. But then we have also eliminated the possibility of valuing anything as good. The question of good and evil includes a great deal of conceptual content that is not subject to physical investigation. If the answer is not found through science, it does not mean there is nothing more to be said about it; it simply means that scientific methods have reached their limit and that other disciplines are more appropriate for the topic.


Yorktown, Virginia

Greene’s research has led him to the conclusion that “once you understand someone’s behavior on a sufficiently mechanical level, it’s very hard to look at them as evil.” Although Greene may be far from a comprehensive understanding of practical ethical decision making, his challenge to our society’s base assumption of free will merits consideration. If Greene does indeed prove that there is a deterministic manner in which we make ethical decisions, would it not follow that our jails should be replaced by medical treatment facilities to rehabilitate criminals? How would we deal with criminals whose ethical decision-making dysfunction cannot be “cured” by contemporary medicine? After all, they are not to blame for their poor decisions.


South Bend, Indiana

The morality questions posed in “Whose Life Would You Save?” are interesting, but I believe they have a serious flaw. Morality is heavily influenced by one’s perception of future uncertainty. Joshua Greene hypothesizes that people would be uncomfortable with pushing the large man into the path of the oncoming trolley because it would seem more like murder than flipping a switch. This may be true, but people may be equally uncomfortable with this because attacking a large man involves too many unknowns. What if he fends off your attack? What if he pushes you in front of the train? What if his body fails to stop the trolley, and now six people are dead? Greene’s dilemmas ignore these questions, but his test subjects may not. Any tough moral question involves weighing many potential outcomes, none of which can be certain in advance.


Chicago, Illinois

Armor All

The article “Glassy Metal” [April] makes these materials sound virtually indestructible, which gives rise to the question: What can be done with the stuff after it has done its job on a specific application? Can it be recycled? Reused? Reconstituted? Or will we be stuck trying to find places to dump it?


Seal Cove, Maine

Joseph Poon, a materials physicist at the University of Virginia who is developing amorphous steel, responds: Amorphous metals are like regular metals; the only difference is that the elements in them have a different structural shape. Therefore, they can be remelted and recast just as conventional metals can.

What’s in Your Tank?

The calculations by biologist Jeffrey Dukes [“What’s in a Gallon of Gas?” R&D, April] are replete with grand assumptions that lead to even grander conclusions about energy usage and carbon dioxide generation. It is not clear from this article how the yield of 20 pounds of carbon dioxide from burning a gallon of gasoline was calculated. Further calculations of energy consumption that venture into billions and trillions are eye-opening but of suspect significance. Dukes’s concern that people must face up to the energy problem is correct. We must develop new sources of renewable energy that are environmentally friendly. However, gee-whiz calculations based on suspect assumptions and ignoring the multitude of factors that affect energy generation, consumption, and the resultant climatic consequences do not serve the public appropriately.


Parker, Colorado

The editors respond: We thought the numbers in Dukes’s study were fascinating for what they reveal about the amount of raw biomass needed to create a gallon of gasoline; however, due to space constraints, we could not go into greater detail about fossil-fuel production and energy usage. Here’s how we got the weight of CO2: Gasoline is made up of short-chain hydrocarbons, molecules that are around 87 percent carbon by weight. That fraction means there are about 5.4 pounds of carbon in 6.2 pounds of gas (the weight of one gallon). Combine that carbon with two parts oxygen from the atmosphere and you get 19.8 pounds of CO2.

To read more letters (all Web-exclusive) on this month’s features and departments, see www.discover.com/letters.


In April’s Bogglers: For “Gauss’s Shortcut,” problem 4, the sum of the odd numbers from 1 to 1,001 is 5012, or 251,001. For “Adding Backward,” problem 2: A 15 percent tip on a bill of $26.14 is $3.92. To multiply by 5 using the shortcut, multiply by 10 and divide by 2. In “The Cryptography of . . . Voting Machines” (May), the percentage of lost votes using optical-scan-card ballots and punch-card ballots should have been 2.7 and 6.3, respectively.

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