If we could build a spaceship that could accelerate at a constant 1G, could we leverage time dilation to reach the nearest galaxy within the lifetime of human on the spaceship? No. But you can definitely, if you could accelerate at 1G and that way you can walk around in the spaceship as though you're on Earth because you have a 1G acceleration, that would be cool. We can go ahead and do that. Go to the nearest stars and come back and yes, time dilation, you'll eventually reach near the speed of light. Time dilation will allow you to not age very much, but people on Earth will continue to age and when you come back, everyone will