

I don’t think this is something we have to worry about in the near future and I don’t think it will happen under Trump. What concerns me is the way the “system” is being set up so that alternative points of view or other parties just won’t have a chance to win an election or survive a lawsuit.
The groundwork is being laid so that people way more extreme than what we are seeing now can come into power and then stay in power without any way of removing them.
The current administration is setting things up where in order to “count” you have to be 1) loyal to Trump and 2) loyal to the republican party (don’t want any RINOs!). Heck, you can subscribe to typically republican principals (lower taxes, lower spending, right to bear arms, strong military, etc…) but you aren’t a “real” republican unless you un-waveringly support Trump.
But a true patriot is loyal to the Constitution. But now, you can’t be a republican and be loyal to the constitution, you have to be loyal to Trump. And that is setting things up to go very badly.
It kind of depends how far away they go. There is this concept called a “light cone” and it’s basically the information that could possibly reach you as you go through space/time. If they land inside your light cone, they could possibly reach earth with a signal. It may take a long time and they are long gone, but it could be possible.
If they are outside the Earth’s light cone, there is no possible way for their signal to reach earth.
https://en.wikipedia.org/wiki/Light_cone