The fastest speed a human body can withstand in space is difficult to determine precisely, as it depends on various factors such as acceleration, duration, and physiological tolerance. However, it is generally accepted that sustained acceleration above 5-10 times the force of gravity (5-10 g) can be dangerous or even fatal to the human body.
Assuming we consider a more conservative acceleration of 5 g, which is five times the force of Earth's gravity, we can calculate the time it would take to travel a light-year:
The speed of light is approximately 299,792 kilometers per second. To convert this into a more convenient unit, we can multiply it by the number of seconds in a year (which is approximately 31,536,000 seconds) to get the speed of light per year:
299,792 km/s * 31,536,000 s/year = 9.461 trillion kilometers per year.
If we could sustain an acceleration of 5 g, which is roughly 49.05 meters per second squared, we can calculate the time it would take to reach the speed of light:
v = at
where: v is the final velocity, a is the acceleration, t is the time.
Let's solve for time:
299,792 km/s = (49.05 m/s^2) * t
Converting km/s to m/s:
299,792 km/s = 299,792,000 m/s
Solving for t:
299,792,000 m/s = (49.05 m/s^2) * t
t = 6,113,244 seconds
Dividing by the number of seconds in a year:
6,113,244 seconds / 31,536,000 seconds/year ≈ 0.194 years
So, at an acceleration of 5 g, it would take approximately 0.194 years (or about 71 days) to reach the speed of light.
However, it's important to note that this calculation is for reaching the speed of light, not for traveling a light-year distance. Traveling a light-year at the speed of light would take precisely one year, as a light-year is defined as the distance light travels in one year.