nongravitational

The sad thing about it is that small nongravitational forces and astrometric errors make an accurate collision prediction very hard to do more than a few years out.

Asteroid Threat Conference Underway - NASA Watch 2009

Indeed, this duality between ordinary refraction and gravitational lensing is one of the fascinating maps between gravitation and nongravitational physics that are implied by the duality.

Guest Blogger: Joe Polchinski on the String Debates Sean 2006