[agere_contra]

The asteroid is in free fall, unchecked by frictional forces. Any mass that impacts on it and/or accretes to it will have an effect (though perhaps not a measurable one).

Also: Apophis will be moving immense distances along an elliptical orbit before it gets close to Earth again. A one mm difference in its trajectory now might well make a significant difference in 20 years - significant enough to miss us. Or steer the rock into us.

[wolfcreek]

“Or steer the rock into us.”

That’s my issue.

[LevinFan]

I don’t have the math on me right now, but the kinetic energy of a satellite going 6 miles per second is enormous. It would be like using a nuclear weapon.