The observed velocity shift of BALs are explained by several possible causes 1The actual acceleration or deceleration of the outflowing material in the direction of the observers line of sight 2 the o

Some researchers suggest that a combination of these factors may contribute to the observed velocity shifts. For example, changes in the physical properties of the outflowing material may cause some of the observed velocity shifts, while others may be caused by the material passing through the observer's line of sight in a circular motion.

One promising avenue of research involves studying the variability of BALs over time. By monitoring the changes in the velocity shifts and other properties of BALs over weeks, months, or even years, researchers may be able to gain insights into the physical mechanisms that cause these shifts.

Overall, the study of BALs remains an active area of research in the field of astrophysics, with many unanswered questions and potential avenues for future exploration