Time dilation and the human body

[Ricb]

TL;DR Summary

aging at light speed

As your velocity increases time in your frame of reference slows down with respect to other frames of reference until, at the speed of light, time essentially stands still. Hypothetically, I am travelling at the speed of light and, therefore, for me, time stands still. I am travelling to a star system that is 40 light years away. Does my body clock stand still or will my body still age even though time compared to the outside universe stands still?

 

[Dale]

It is not possible for a massive object to travel at the speed of light.

If you are traveling just under the speed of light in an inertial frame then you will age slowly in that frame.

 

[russ_watters]

Does my body clock stand still or will my body still age even though time compared to the outside universe stands still?

Your body clock is a clock. It behaves like other clocks.

 

[Ibix]

As your velocity increases time in your frame of reference slows down with respect to other frames of reference until, at the speed of light, time essentially stands still.

The first part is more or less true as far as it goes. Note that there are a lot of traps for the unwary with this line of thinking. The bit about the speed of light is incorrect, however. It is not possible to define time (specifically proper time, which is what you are talking about) for things moving st light speed.

Hypothetically, I am travelling at the speed of light and, therefore, for me, time stands still.

This is impossible. "Has non-zero mass and travels slower than light" and "has zero mass and travels at the speed of light" both turn out to be tautologies in relativity, so you cannot travel at the speed of light even in principle. And, as noted above, "time stands still" isn't accurate.

I am travelling to a star system that is 40 light years away. Does my body clock stand still or will my body still age even though time compared to the outside universe stands still?

Replacing your assumption of light speed with "near light speed relative to the star systems", Russ' answer is correct: your body is a clock like any other. Given sufficient fuel (which is s horrifyingly large amount, on the order of millions of tons per kilo of payload even with the most efficient rocket possible) and resistance to acceleration, you can make the journey in arbitrarily short time by your own experience.

 

[Orodruin]

As your velocity increases time in your frame of reference slows down with respect to other frames of reference until, at the speed of light, time essentially stands still.

Just to avoid a very common pitfall: Other reference frames will see you age slower. However, you will still feel and age exactly the same in your own rest frame. By symmetry, you will see other reference frames moving at some speed and hence they will be time dilated relative to you. There is no universal rest frame that decides which frames are moving or not.