First of all, let me point out that you will never travel at the speed of light (see this for details). But that doesn’t mean that it wouldn’t be fun to speculate about what would happen if you were going at light speed. As you approach the speed of light (with respect to O), this time dilation effect becomes more and more pronounced. As you approach the speed of light, this effect becomes increasingly pronounced, and at at the speed of light itself O will have zero length in the direction you are traveling. Another consequence of light speed travel is that you’d become the most dangerous thing imaginable (move over, Chuck).