Yuri Milner is spending $100 million on a probe that could travel to Alpha Centauri within a generation—and he's recruited Mark Zuckerberg and Stephen Hawking to help. In an interview with The Atlantic, Milner makes his case for star travel.
There are so many unknown gravitational sources along the way, and human cannot hope to steer the direction of the space probe in real time in order to avoid them all. Assuming that you want to change the course of the probe when it's halfway through ( about 2 light years from the earth), your signal will have to travel at least 2 years before reaching the probe, but by then the probe might already have collided with a planet. It's too late. The remote control cannot be done in real time.
So how can scientists and engineers ensure that this probe actually reaches Alpha Centauri-- a galaxy that is a few light years away from earth-- instead of colliding with or being sucked into stars, planets, comets and other unknown gravity sources ( like dark matter perhaps)?