Comment by qbolec on So You Want To Colonize The Universe Part 3: Dust · 2019-03-01T07:29:37.331Z · score: 5 (4 votes) · LW · GW

I was afraid my questions might get ridiculed or ignored, but instead I've got a very gentle and simply expressed explanations helping me get out of confusion. Thank you for taking your time for writing your answer so clearly :)

Comment by qbolec on So You Want To Colonize The Universe Part 3: Dust · 2019-02-28T19:49:59.545Z · score: 7 (6 votes) · LW · GW

I suspect my following questions demonstrate such high level of confusion, that I am not sure if they even mean what I think they mean, but still I think this is the best place to ask them:

  1. My mental model of something very small hitting with very high energy something big is "Warner Bros cartoon"-like: one fast billard ball very quickly makes a hole in the big object by dislocating just one or a few more billard balls accelerating them all in the same direction without much effect to the integrity of the rest of the big object. I recall XKCD What If series explicitly addresing this mental model as flawed. Still, what if the big object is very flat, like a sail, and very loosely connected like a net? In general: is there any hope to make a spacecraft which simply doesn't care about being hit, because (due to some "error codes" or "nanobots/regeneration") can tolerate holes and holes are the only thing caused by impacts to it?
  2. If there are particles which penetrate (almost) everything, why not make spacecraft from them? (Are neutrinos alien's network?:))
  3. If photons are so low mass, why not use something more massive to shoot the sail with?
  4. Are there any "repulsive" / "potential energy" phenomena one could use to decelerate - I mean things like buouyancy, where (obviously in this example I am talking about very small velocities) a vehicle entering atmosphere could perhaps use a big balloon to covert kinetic energy to potential energy of buoyancy (with added benefit of being able to reuse some of this energy for going back home)? For another example, could a sufficiently advanced civilisation aim in between two stars so that the net force of their gravity pulled the spacecraft backwards till it (briefly) stops? I know this examples are silly, I just try to explain what would count as "this kind of solution".