Where were you when you had to believe the unbelievable? This side of the Atlantic, many of us were at work. On Tuesday afternoon, I was sitting at my desk writing a routine story about a forthcoming documentary on RT╔, in the features department of this newspaper. Our area abuts the sports department and their television is on all day, as it is in the newsroom.
I can't see it from where I sit, but I hear it. It never distracts me, in fact I hardly notice it. Journalists probably develop tolerance of noisy environments. Somewhere, far in my consciousness, I registered that the television was on that Tuesday afternoon.
People are always moving around our office. I didn't even notice who the woman was who hurried passed, but I caught some of what she said: "plane . . . World Trade Centre . . . television". Her tone alerted me, something urgent in the inflections.
Few people heard her, and so most stayed at their desks, focused on deadlines and page layouts. I left my desk immediately and went to stand with about eight others under the television in the sports department.
CNN was running. I saw the North Tower of the World Trade Centre smoking, but I did not understand what I was looking at. "A plane has gone into it, I think they're saying," someone said doubtfully.
We were curious, and a bit confused. It was one of those strange freak accidents, I thought, a small plane has somehow got lost.
I remembered the pictures that ran recently of a parachutist caught in the Statue of Liberty. Perhaps a small plane had been trying to land on top of the building in some similar idiot hare-brained stunt.
I work in a five-storey building: I'm not used to looking at skyscrapers. I have only been to New York once, briefly, and so I didn't realise the scale and size of the Trade Centre towers when watching those first pictures. Nor did I realise they had more than 100 floors apiece, and so did not register that what seemed a smallish fire was a huge inferno.
Later, I studied a wire picture of that part of the tower where the fireball was, counting with slow horror the floors it had enveloped, and stopping at 30 because I did not want to know any more.
It sounds bizarre, but I then went back to my desk and returned to my story. I was not able to take in what I had seen. A couple of minutes later, my colleague Kevin Courtney, who had been sitting adjacent to me, and who had stayed watching, came rushing over.
"I've just seen a plane flying into the second tower," he shouted. People don't scream in our office. There was hysteria in his voice. "It's terrorists." You what? It's what? What's happening?
Suddenly everyone was on their feet, editors, reporters, sub-editors, messenger boys, all anxious, swift, incredulous, bewildered. The television in our department snapped on. We moved to it as if magnetised to see the replay of that second plane turn and thud into the South Tower, and still I did not realise what I was seeing, even though it looked so familiar, as if I had seen it before in a movie. Seeing the images framed on television somehow made the reality more unreal, as if it had been edited or contrived, rather than being unspeakable live coverage.
I thought instantly: this is historic. This is huge. I felt shocked at that instinctive certainty, because some part of my brain was clearly working faster than the part that could not acknowledge what I was watching.
I felt both detached and transfixed, hauled into New York from the centre of Dublin.
With dread, we watched aghast and disbelieving as the skyline smoked. I have never stopped at accidents. I detest ghoulish onlookers. On Tuesday, I became one; it would have been a worse travesty not to look, as if what was happening did not matter. The journalist in me registered coldly that the commentators were struggling to get their words out, therefore it must be true.
A newspaper is the eeriest place to be when a huge story of unprecedented dimensions breaks. Running through my head also, as we watched in horror, was the knowledge that my newsroom colleagues would have to instantly begin to attempt to interpret for the next day's paper what was happening; to select images; to try to report something which already seemed as much fictional as historical.
People around me were overwhelmed for those endless terrible minutes. The last time numbers of us watched television coverage together during the working day was when Sonia O'Sullivan raced in Sydney, and even then not everybody watched. But on Tuesday, all rose to their feet and stared at the television images which none of us could believe we were seeing.
I found myself wondering stupidly if anyone on the hijacked planes could have survived. At that time, I was not processing what I was seeing.
I certainly could not process what I couldn't see: thousands and thousands of terrified people attempting to escape from doomed buildings.
Then news started breaking of more hijacked planes in the air, of the Pentagon being hit. We stared at the television screen. The cameras tried frantically to keep up, jumping from unimaginable scene to unimaginable scene.
When the first tower fell, I finally realised what I was seeing. And I understood too that I was looking at an America that had changed for ever, and that I was now living in a world that felt different from when I had sat down such a short time before to write my article about a documentary.
It felt different because it was different.