Measuring the amount of deuterium in the universe allows us to set a limit on

Question

BlackTom AI · Accepted Answer

Question restatement: Measuring the amount of deuterium in the universe allows us to set a limit on which of the following?

Option 1: the density of ordinary (baryonic) matter in the universe. This is the correct linkage. Deuterium abundance is a sensitive probe of the baryon density during Big Bang nucleosynthesis; higher baryon density would burn more deuterium into heavier elements, so precise measurements of primordial deuterium constrain the amount of ordinary matter present.

Option 2: the temperature of the universe at the end of the era of nuclei. Deuterium measurements inform nuclear processes and matter content, but they do not directly fix the thermal state or temperature of the universe at the end of nucleosynthesis stages; temperature evolution is inferred from other cosmic background signals and expansion history rather than deuterium alone.

Option 3: the total amount of mass in the universe. While baryonic matter is a component of total mass, deuterium abundance specifically constrains baryons, not non-baryonic components like dark matter. Therefore it does not determine the universe’s total mass budget.

Option 4: the expansion rate of the universe. The expansion rate is governed by the overall energy content, including dark energy and matter components. Deuterium abundance does not directly set the expansion rate; it constrains the baryon density, which is only one piece of the total dynamics influencing expansion.

In summary, deuterium serves as a precise indicator of baryonic (ordinary) matter density due to its sensitivity to nuclear processes in the early universe, while the other options involve aspects not directly determined by primordial deuterium measurements.

Measuring the amount of deuterium in the universe allows us to set a limit on单项选择题

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