Space Travel: You've managed to hop a flight on a Space Craft which was able to attain a speed of 86.6% speed of light..

Question

You've managed to hop a flight on a Space Craft which was able to attain a speed of 86.6% the speed of light. You and your twin brother were both age 20 when you left. When you returned, your twin brother was age 40.

How old are you?

Hint: Lorentz Contraction Equation

Answer 1

As an object moves closer and closer to the speed of light the time that it experiences will be longer and longer for an observer in a stationary frame of reference.

Comments

Yes, 30 years old. You are correct, complete with a detailed explanation along with the Lorentz Equation.
A useful reference is simply to remember that .866 speed of light = 50% less aging.

---

I was thinking at first what's up with the velocity being such a specific value.

---

Yes, and that's what peaks curiosity. One of the reasons why cats are the preferred pet of intellectuals.  They are indifferent but yet so incredibly curious.  Just like scientists.

In order to get the reference point of 50% less aging, I needed to do several trial/error values for velocity squared.  And voila', .866 when squared gives .75 and then 1 - .75 = .25 and sq rt of that = .5 or 50% less aging.

Trial and error are the whole basis of math/science and often lead to serendipitous discoveries..  In fact those "post-its" by 3M company are the epitome of exactly that.