So, 800,000 years to reach Alpha Centauri by sail ship.
At the half way mark, wouldn’t the photons from AC work against the solar photons? I guess we’ll have to wait 400,000 years to find out
That would suck, wouldn’t it?
Photons from AC are negligible in comparison to the impetus from the massive laser beam from earth. Those photons from AC may indeed work against the photons from the sun, and in fact would overpower the sun's puny output since there are three stars (they think) associated with AC vs. only one star on this end. As the article says, "Once the sail is in orbit, a massive array of ground-based lasers would train their beams on it, providing a light intensity millions of times greater than the sun's," and vastly greater than AC's. Secondly, the cup of the antenna (or sail) is oriented toward earth, not AC. So only all that intense laser light from earth has any chance of pushing the "starchip."