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 aging process etc.) on that is 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 to be 70 years.

Explanation

To solve the problem, we need to determine the average lifespan of a human on an imaginary planet that is twice the distance from its star compared to the Earth-Sun distance. We will use Kepler's Third Law of planetary motion to find the relationship between the orbital period of the planet and its distance from the star.

### Step-by-Step Solution:

1. **Identify the parameters**:
- Let the distance between the Earth and the Sun be \( a \).
- The distance from the central star to the imaginary planet is \( a' = 2a \).
- The average lifespan of a human on Earth is \( 70 \) years.
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