What critical factor influences whether you weigh more at the bottom of Death Valley or atop a peak in the Sierra Nevada?

The correct answer focuses on the proximity to Earth's center as the critical factor influencing weight differences between two locations, such as the bottom of Death Valley and the peak of the Sierra Nevada.

Weight is dependent on the local gravitational pull, which varies with distance from the Earth's center. When you are at the bottom of Death Valley, which is below sea level, you are closer to the Earth's center compared to being at a high altitude like the peak of the Sierra Nevada. The force of gravity is stronger when you are closer to the mass that generates it, which means that you would weigh slightly more in Death Valley than at the mountain peak.

In contrast, while factors like local gravitational variations and air pressure differences do have an effect on weight measurements, they are secondary influences compared to the effect of proximity to Earth’s center. The distance from the Moon has an insignificant impact on your weight in this context; while the Moon does exert a gravitational force on Earth, it does not significantly alter the measurement of one's weight based on elevation differences on Earth.