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

Answer

25

Explanation

According to Kepler.s law of periods,
`((T_(1))/(T_(2)))^(2)=((R_(1))/(R_(2)))^(3)`
Here, `T_(1)` = Average life span of a human on the earth = 70 years.
`T_(2)` = Average life span of a human on the planet = ?
`R_(1)` = Distance between the earth and the planet `=2R_(2)`
`R_(2)` = Distance between the earth and the sun.
`therefore ((70)/(T_(2)))^(2)=((2R_(2))/(R_(2)))^(3)`
or `(70xx70)/(T_(2)^(2))=8orT_(2)^(2)=(70xx70)/(8)`
`thereforeT_(2)=(70)/(sqrt(8))=25` Planet years.