•Radiation pressure  (pressure of light)
 –Will see present day effects in
 comets
 •Solar Wind
 –Strong solar winds from young T Tauri
 stars
 –Will see present day effects in
 comets
 •Sweeping up of debris into planets
 –Late Heavy Bombardment
 •Ejection
 of material by near misses with planets
 –Like
 “gravity assist maneuvers” with spacecraft
 –Origin
 of the comets