Aliens vs. comet junk: Nasa scientist weighs in on Oumuamua debate

All this fails to take into account Oumuamua not only changed speed, but it also changed direction. If someone's goal is to go from A to B, you don't want a meager gravity assist that'll add a dozen light-years to the distance you travel.

So, if you are driving from Santa Clara to Sunnyvale, it's not a great idea to first drive to LA to get a faster car, and then drive to Sunnyvale. In fact, it'd be faster to walk.