Final answer:
Half of Earth's atmosphere's mass is located within 5.6 kilometers above the Earth's surface. A person's weight would decrease by a factor of three if Earth had only a third of its mass. If Earth had eight times its volume but the same mass, a person's weight would also be lower.
Step-by-step explanation:
The question you've asked relates to the weight and distribution of the Earth's atmosphere. Approximately half of the Earth's atmosphere's mass is located within 5.6 kilometers (3.5 miles) above the Earth's surface. This is within the lowest part of the atmosphere, known as the troposphere, which extends from the Earth’s surface up to about 10 kilometers (6.2 miles) depending on geographic location and weather patterns.
In regards to how weight changes with mass and volume alterations of Earth, if the Earth had its current size but only a third of its present mass, a person's weight on the surface would also decrease by a factor of three, as weight is directly proportional to the mass causing the gravitational attraction. Similarly, if Earth had its current mass but eight times the volume, gravity at the Earth's surface would be weaker due to the increased radius, resulting in a lower weight for a person standing on the surface.