does drag exist?
Yes, but it won’t much affect the motion of the Earth. The so-called Poynting-Robertson effect causes sunlight to exert a drag on any orbiting object. However, it is mainly effective on small particles. It may help clear the solar system of dust particles from comets–the ones large enough not to be blown away by sunlight pressure. In addition, the solar wind will also exert a drag. The reason is that as sensed by Earth, it does not come straight from the Sun (in which case momentum absorbed from it by the Earth would only modify the attraction of the Sun). Because the motion of the Earth at 30 km/sec is vectorially combined with the radial motion of the solar wind at about 400 km/s, that wind appears to us to come from a direction displaced about 4 degrees from the direction of sunlight. The momentum absorbed from the solar wind as it encounters the magnetosphere therefore produces a certain drag, but it is too small to significantly affect the Earth’s orbital motion. The force is tra
