The ghost bush on the bus!

No really! Riding on bus recently I saw a bush straight ahead through the front window. The bush was obviously not in the road it was beside it and the bus was on a bend so it looked straight ahead momentarily. As the bus turned right with the curve the bush entered the bus and travelled in straight line down the aisle before stopping and then vanishing! So a ghost bush! On a bus!

I was amazed when I saw this. It looked like the bus had run straight into a stationary ghost bush which appeared to travel down the aisle as a consequence of the motion of the bus. I've never seen anything like it. It rapidly became obvious that the ghost was actually an afterimage. The motion of the 'bush' was caused by me moving my eyes to follow its expected trajectory. The effect was astonishingly realistic. The 'bush' stopped because my eyes stopped moving at which point the afterimage faded away. Although it felt real at the time, it clearly wasn't. For the bush to have gone down the aisle the bus would have had to mount the pavement and run over it, which thankfully it didn't.

But would anyone really think such an effect was a real ghost? Until this incident I would have said no. After all, you can see the image moves with your eye movement so it can’t be real. When demonstrated in a book or computer screen everyone can see an afterimage is just a perception trick. But in a real life situation, like the bus, it may not be so obvious. And if the afterimage was of a human figure it could feel very much like a ghost. Such a report would probably not stand up to a critical analysis, just as this one didn't. It is worth noting that the persistence and strength of afterimages varies between people.