Your right, this requires some explnation.
Ok, down and dirty, You know a little bit about how a microwave oven works? Radiation excites the molcules and such, producing heat due to the friction of moving atoms.
Photons, (AKA light, laser, radio waves) contain energy, when they hit the electrons of an atom, the electrons in that atom can absorb (if “colder”) this extra energy. (BTW hot atoms spew energy out in the same form). Atoms bump against one another to try to establish equillibrium (also called Null, to spread this extra energy evenly), remember these atoms are in motion (think of billiard balls, hit the rack lightly with the cue ball, the other balls would tend to seperate, but there are other forces at work, the molecules within any rock or other solid object are bound together by specific Physical laws of combination and/or association)
Ok, now, our asteroid only needs to be steerd off by a fraction of a degree. so if we can excite the molecules on the side of an asteriod (the side we wish to push on) it will actually.. push it into that direction. It’s because of the fact that we can affect change in the energy state of the the molecules on the side we “push” on, that it works.
These changes on our “push” side will be absorbed by the rest of the asteroid as a whole. Now in our microwave oven, we cant see it, but in zero G space and powerfull nukes at exactly the right distance and position, the path of any interstellar object can changed.
I hope I did’nt confuse you more
Most asteroids are spinning in three directions on their x,y,and z axis. Detirmining a “side” to push on would be hard to do as the asteroid is twisting and tumbling as your nukes are going off!