So, say we want to go live on Kepler-438b. It’s 1,400 light years away, so that means it would take a spacecraft that could travel very near the speed of light over 1,400 years to get there. Prohibitive, right?
Well, yes and no.
Indeed, watching from our vantage point on earth, it would appear to take our brave colonists that long to reach the planet. But how long would the trip seem to the colonists themselves? Thanks to Einstein’s time dilation, things would be very different from their perspective.
Since Kepler-438b has 2x the Earth’s gravity (2 Gs), let’s say we start the acceleration of the spacecraft at 1G, and gradually dial it up to 2Gs by the end of the trip. You know, to help them get used to their new, heavier life. That acceleration would seem indistinguishable from the sensation of gravity.
Then, at the halfway point of the trip, the ship turns its thrusters around, and decelerates at the same gradually increasing G force, finally coming to a complete stop at Earth 2.0.
The duration of the trip from the traveller’s perspective? Just a hair under 10 years. Not so bad, right?
Now, going that fast isn’t the hard part. You just… keep accelerating. But the energy required to pull this off is kind of hard to conceive.
Let’s try. I’m certainly not smart enough to do the math myself (the above was done with an online calculator) but I read once that the energy required to move a modestly sized ship only 20 light years would take 3 million years to collect — if the entire Earth was covered in solar panels.
So, there’s that part to figure out.