It is a thought experiment and based on time dilation. It goes like.. consider a cab moving with a speed close to light.Also the cab has been divide into two equal halves by a glass wall. there are two individuals in cab one in each part of the cab divided by the glass wall.One is very old man and the other is a normal guy which will serve as observer 'A'. And we have a ground observer 'B' (at rest). Now the portion in which i have the old man i put a clock and a cylinder of cyanide and made certain arrangements that if the clock slows down from its normal rate then a electronic system will start say a counter which will open the cyanide cylinder and the old man will die. *see the arrangements can be mechanical also using gears and hammers. since for the observer 'B' the cab is moving with a speed close to light.He sees the clock in cab to be dilated i.e. for him the cyanide cylinder will burst and the man will die but for the observer A,for him the clock is in rest thus no time dilation and hence no death of the old man. my problem is that... Life and Death are absolute truth(what i believe) so these shouldn't change from frame to frame that i am alive in respect with one frame and dead in another.