Question

In an imaginary planetary system, the central star has the same mass as our sun, but is much brighter so that only a planet twice the distance between the earth and the sun can support life. Assuming biological evolution (including ageing process etc.) on that planet similar to ours, what would be the average life-span of "human" on that planet in terms of its natural year? The average life span of a human on the earth may be taken to be 70 years.

Answer 1

The natural year of a planet means the time taken by the planet to complete one revolution around the sun.

If R1 is the semi-major axis of the earth'* orbit, then the semi-major axis of the imaginary planet is:

R2 = 2R1

If T1 and T2 are the time-periods of the earth and the planet, then,

Therefore, one natural year of the imaginary planet corresponds to 2.828 years on earth. Hence, average life span of 70 years of human on earth in terms of the natural years of the imaginary planet

= 70/2.828 = 24.75 years