How long would it take a spacecraft traveling at the speed of light to safely make a u-turn, g forces on body?

Question

Considering the G-forces on the human body and a spacecraft traveling at the SPEED OF LIGHT, it would take a very long time to make a U TURN in outer space without the spacetravelers suffering any ill effects.

So...how long would it take (hours?...days?...weeks?...years ?) to safely make a U TURN in outer space?

Answer 1

There are two ways of answering this question....

One way would be to merely say that no object with mass can ever obtain a speed equal to or greater than the speed of light since doing so would require an infinite amount of energy (and in the entire universe, there is not an infinite amount of energy). Additionally, your question asks about the "time" it would take to accomplish this maneuver...but time is relative to the observer, especially when it comes to relativistic speeds. So the question is entirely impractical in its current form.

Another way to answer this question would be to entertain the idea of light speed travel and assume some type of universal time frame...purely for the novelty purposes of the question with the disclaimer I have already stated above.

Now the question comes down to just how many "g"s the person in the space ship is willing to take? 1 "g" (equivalent to the acceleration experiences standing still on the surface of Earth), or how about 7 or 8 "g"s (accelerations more common to fighter pilots and astronauts blasting off into space.
How about we assume a nice around number of 10 "g" (an we will round g up to 10 m/s^2)...making the acceleration experiences by the people in the space ship equal to 100 m/s^2 [not a small value to be sure].

Also, remember that the speed of light is about 3 E8 m/s.

So if the space ship was to execute a U turn where it was originally traveling at the speed of light (c) in one direction and at the end of the turn the space ship was traveling at c in the opposite direction, this comes out to an overall change in velocity of 2 * c or about 6 E8 m/s.

Change in velocity = acceleration * time
We know that the change in velocity = 2c and we have previously defined our acceleration to be 100 m/s^2. All that is left is to solve for the time.
time = 2c / 100 m/s^2
time = 6 E6 seconds,
or a little less than 70 days!

But again, I must remind you of the severe limitations of this answer; it was more an exercise in algebra than a solution to your question.

Answer 2

You'd never reach the speed of light, or even get close to it alive.

I would also think it would be impossible to turn the craft at such a speed. If you were going amazingly fast, there would be very little turning. Your route is preplanned very carefully for this reason.

You could slow down dramatically to make the turn, but you would also require a gravitational body like a planet/moon/star/massive asteroid to make the slingshot around. Without that the shuttle just isn't going to be able to turn (not without some special kind of booster).

In this case the gforce would probably be extreme. In order to make the slingshot without being pulled in by the bodies gravity you would have to accelerate very quickly. I would say the gforce would exceed 10 g's. You could kill everyone on board without planning such an event.

Answer 3

not sure but I think even the strongest of humans can only sustain g forces no stronger than 4 g's for a log period of time

Answer 4

ha, silly human, you can't go the speed of light. By that point you'd be nothing but pure energy.