Physicist: A kilogram of antimatter mixed with a kilogram of matter would, through their mutual annihilation, release half as much energy as all the gasoline burned in the United States in 2005. But this process will never provide a practical means of generating energy: no known natural sources of antimatter are available, and the most efficient antimatter generator now in existence would have to run for 100 trillion years to make a kilogram of antimatter.
Which of the following is an assumption required by the physicist’s argument?
- A. No other fuel could release as much energy per kilogram as antimatter when it is mixed with matter.
- B. Present physics indicates that antimatter is unlikely to exist anywhere in large enough quantities to be usable as fuel.
- C. No antimatter has yet been found in large enough quantities to be perceived by the naked eye (without magnifying instruments).
- D. We will never, in the future, build an antimatter generator efficient enough to produce, within a practical amount of time, a sufficient amount to be practical as a fuel.
- E. Making a kilogram of antimatter would take less than half as much energy as was released by all the gasoline burned in the United States in 2005.
Solution
Passage Analysis:
| Text from Passage | Analysis |
| A kilogram of antimatter mixed with a kilogram of matter would, through their mutual annihilation, release half as much energy as all the gasoline burned in the United States in 2005. | What it says: Antimatter-matter reactions create enormous amounts of energy – we’re talking about crazy amounts here What it does: Sets up how incredibly powerful this energy source could theoretically be What it is: Physicist’s factual claim about antimatter’s energy potential Visualization: 2 kg total (1 kg antimatter + 1 kg matter) ā Energy equal to 50% of ALL US gasoline used in 2005 (imagine half of every gas station, car tank, etc. in America for a whole year) |
| But this process will never provide a practical means of generating energy: no known natural sources of antimatter are available, and the most efficient antimatter generator now in existence would have to run for 100 trillion years to make a kilogram of antimatter. | What it says: Despite the huge energy potential, antimatter can’t be a practical energy source because we can’t get enough of it What it does: Completely flips from the promising setup to explain why it won’t work in reality What it is: Physicist’s main conclusion with supporting evidence Visualization: Current best generator: 100,000,000,000,000 years ā 1 kg antimatter (that’s longer than the universe has existed by thousands of times) |
Argument Flow:
“The physicist starts by acknowledging antimatter’s incredible energy potential, then immediately argues against its practicality by showing the massive obstacles to obtaining antimatter”
Main Conclusion:
“Antimatter will never provide a practical way to generate energy”
Logical Structure:
“The argument uses a ‘yes, but’ structure – admits antimatter has amazing energy potential BUT shows this doesn’t matter because we can’t get antimatter in any reasonable way (no natural sources + current production is impossibly slow)”
Prethinking:
Question type:
Assumption – We need to find what the physicist must believe to be true for their argument to work. We’re looking for unstated beliefs that, if false, would make the conclusion fall apart.
Precision of Claims
The physicist makes precise quantitative claims (100 trillion years, 1 kilogram) and an absolute conclusion (‘will never provide a practical means’). The word ‘never’ is key – this means not just impractical now, but impractical forever.
Strategy
Since this is an assumption question, we need to identify ways the conclusion could be falsified while respecting the stated facts. The physicist concludes antimatter will ‘never’ be practical based on current technology taking 100 trillion years. We need to find what unstated beliefs make this reasoning work – what must be true about future technology, alternative methods, or practical timeframes for this ‘never’ conclusion to hold?
Answer Choices Explained
A. No other fuel could release as much energy per kilogram as antimatter when it is mixed with matter.
‘No other fuel could release as much energy per kilogram as antimatter when it is mixed with matter.’ This isn’t required for the argument. The physicist’s point is that antimatter won’t be practical due to acquisition problems, not because other fuels might be more energy-dense. Even if other fuels released more energy per kilogram, antimatter could still be impractical due to the production issues the physicist describes.
B. Present physics indicates that antimatter is unlikely to exist anywhere in large enough quantities to be usable as fuel.
‘Present physics indicates that antimatter is unlikely to exist anywhere in large enough quantities to be usable as fuel.’ This is too narrow – the physicist already states ‘no known natural sources of antimatter are available,’ which covers this point. We don’t need this assumption since the physicist has already addressed natural sources explicitly.
C. No antimatter has yet been found in large enough quantities to be perceived by the naked eye (without magnifying instruments).
‘No antimatter has yet been found in large enough quantities to be perceived by the naked eye.’ This is about detection rather than practical energy generation. Whether we can see antimatter with naked eyes doesn’t affect the argument about its practicality as fuel – the issue is getting enough antimatter, not detecting what we have.
D. We will never, in the future, build an antimatter generator efficient enough to produce, within a practical amount of time, a sufficient amount to be practical as a fuel.
‘We will never, in the future, build an antimatter generator efficient enough to produce, within a practical amount of time, a sufficient amount to be practical as a fuel.’ This is exactly what the physicist must assume. The conclusion says antimatter will ‘never’ be practical, but the evidence only shows current technology is inadequate (100 trillion years). For this ‘never’ conclusion to work, the physicist must assume future technology won’t solve the efficiency problem. If future generators could produce antimatter quickly, the whole argument collapses.
E. Making a kilogram of antimatter would take less than half as much energy as was released by all the gasoline burned in the United States in 2005.
‘Making a kilogram of antimatter would take less than half as much energy as was released by all the gasoline burned in the United States in 2005.’ This would actually argue FOR antimatter’s practicality, not against it. If production required less energy than the antimatter would release, that would be energy-positive. The physicist’s argument doesn’t depend on the energy cost of production – it focuses on time constraints.
