© Edinburgh News
Surgeon Liza McLornan was driving home from work at Dunfermline's Queen Margaret Hospital on Friday afternoon when the freak accident occurred.
The 40-year-old Murrayfield resident was halfway over the bridge at 3.45pm when the unidentified object landed on her Mercedes Benz 320 saloon, shattering the passenger side of the windscreen and spraying glass shards across the front seat and her lap.
Ms McLornan said she had spotted the "white, silver" object falling from the air a fraction of a second before it hit her vehicle.
That brief sighting of the missile was the only glimpse she got.
"I thought initially it could have been a bird," she said. "There was a real crack. When I pulled in to look at the car, it was like a bolt had hit it. There was a big divot in the windscreen.
"It was something metal and something hard that just literally flew straight down from on high."
© Edinburgh News
She has ruled out the debris coming from another vehicle, saying there had been no lorries on the northbound route at the moment the incident happened.
"It's not about me having to pay to fix the windscreen or compensation," she said. "It's more about the principle. This would have killed somebody if it had hit their skull as they walked along the bridge. If it'd hit my side of the windscreen, I would have caused a Friday afternoon pile-up on the bridge.
"I was told they'd stopped working on the bridge at midday and there was no men up there that might have dropped a hammer, that kind of thing. Whatever this was fell from a very great height."
But what could the object have been? CCTV cameras positioned 100 feet up on the bridge failed to pick up the missile, while the Forth Estuary Transport Authority [FETA], which manages the crossing, has investigated and said there was no evidence of an object falling off the structure.
That leaves the possibility that it came from much higher up, although astronomer and former Royal Observatory Edinburgh employee Alan Pickup ruled out the flying object being part of a satellite, saying none had re-entered Earth's orbit at the time.
He said: "The vast majority of objects that reach the ground from space are not satellites - they're meteorites - but it's also very rare they reach the ground.
"I'd be very sceptical if this were anything from orbit, any re-entering space junk, as some people like to call it.
"She would be extremely lucky to be hit by a meteorite because before when cars have been hit by meteorites, it's been so rare that it's immediately added thousands to the value of the car. If it was a meteorite that did the damage and they can prove it, then their car is suddenly worth a lot more than it was."
Mr Pickup said a much more likely explanation was the object had come off a passing plane.
He said: "That area of Edinburgh - the Forth Road Bridge and so on - gets a lot of traffic from aircraft. It's much more likely that what they experienced was something falling off an aircraft."
A FETA spokesman said a woman had called the organisation's offices to report a smashed windscreen suffered on the bridge.
The spokesman said: "We checked the carriageway. There was no debris on the carriageway and no evidence on any CCTV cameras."
I got a nervy feeling once following a VW microbus. I decided to drop back then noticed its back wheel wobbling. Suddenly a white-silver object flew backwards, up through the air, and through my headlight. It was a wheelnut.
It would likely have gone through the windscreen if I had been closer. This was about 40mph and yet the nut flew 40-50 yeards.