Theoretical question

[isee]

Was thinking about ion propulsion and it kind of snowballed.

So given no other forces at work (no gravity or photons), let's imagine an ISS floating in space. and then have a fly that can survive and even fly in space is trying to push the ISS in one direction, given infinite time, will it push the ISS off the spot?

Yes?

what about a stead stream of snowflakes hitting the same spot?

what about one molecule hitting the same spot?

What I am trying to ask I guess, is there such a thing as a force too small or mass too big to make a difference?

[isee]

Eric Mc said:

Yes.

Even light can exert a pressure on an object.

Comets and asteroids are always having their trajectories altered by small impacts or even by light pressure.

Eric I understand that, I was asking if there is a force too small to do anything (yet never the less still a measurable force). Let's say, ISS is stationary and gets hit by a single photon. Will that one photon hitting the station translate into it being shifted say 1 metre a 1000 years later?

[isee]

Galileo said:

I've just been watching about the NASA Dawn mission. It has a Xenon Ion propulsion system that pushes the craft with the same pressure as a piece of A4 paper held in your hand. Given several years that pressure pushed the craft upto 75000 km/h.

i always wondered what that ion thrust is actually like in comparable terms. Never realised it was that small.