PRESENT TENSE:THE WORLD probably doesn't need another piece gasping at how awesome the internet is. But here we go again .

On Wednesday night, while I was looking for a distraction from real work, a chat got going among a few of us on Twitter. It was inspired by With Love from Me . . . to Me, an engaging new book in which well-known Irish people write letters to their 16-year-old selves.

But if you could send your 16-year-old self a tweet – a message of no more than 140 characters – what would you say?

The response was fascinating, insightful, affecting, funny and mind-dizzyingly huge: first in Ireland, then, the next morning, in the UK. Then the US woke up, and by Thursday afternoon it was the most talked about thing on Twitter worldwide.

But the experience was fascinating on a few levels.

Primarily, it was a first-hand insight into how a person can flap their wings in Dublin and watch that ripple grow.

Why did it catch on? Timing and mood, perhaps; or the interjections of a couple of Twitter heavyweights with hundreds of thousands, or millions, of followers. The actor Simon Pegg was one, referring to his future success with: “You are not going to f**king believe this.”

Although one US blog suggested that “at the end of a tumultuous election cycle, the twittersphere happily turned to lighter issues”.

It would be nice to think that a few Irish tweeters gave the US a chance to escape its political trauma. Perhaps it could reciprocate by sending us some jokes. Wrapped in money.

As a topic it was a curious, pithy opportunity for self-assessment, nostalgia and a few jokes. For the original Irish contributors these time-travelling tweets addressed self-consciousness, impending exams, bad haircuts and just how much more respect was due to their suffering parents.

A lot of people advised their younger selves to buy property or bank shares but sell them by 2007. Some mentioned Lotto numbers. A lot of them referred to the opposite sex. Some to the same sex.

Gay tweeters addressing their confused 16-year-old selves employed hard-won wisdom, as summed up perfectly by one tweet: “It’s her brother you actually fancy.”

And occasionally someone would pop up and exclaim, “Hold on, I’m 16 now!”

Trendsmap.com, an online map, tracks these things and it was like that scene in Outbreak where they say, “this is the virus after one hour, six hours, 24 hours”, and the map just coagulates into a single infected blob. That is just what it was like for the #tweetyour16yearoldself – the lead hashtag for the conversation – with its peak coming at 7pm GMT, a time when almost the entire English-speaking tweeting world is babbling.

Having caught on in the UK on Monday morning, it continued to rise with the sun, so that five hours later it was engaging the east coast of the US.

On trendsmap.com you could watch it spread westwards, through the United States, across east Asia and Australia.

In Mexico it became #tuitealeatuyode and beat other top-trending topics, which included “snorkel” and “viv Cristo”.

The meme had also spread eastwards into Europe during the day, but I’m not sure how much to trust its statistics. The site claimed several people in Omsk, in Russia, had tweeted about it, but I actually know one of them, and he doesn’t live any farther east than Clontarf.

(As an aside, the evolution of its hashtag was curious too. The original #tweet16yroldself was picked to allow extra space. It gradually stretched out until Twitter’s hive mind settled for #tweetyour16yearoldself. Longer, but straightforward.

I loved a suggestion by Gareth O’Connor of RTÉ that it be called #tweetsixteen.) Frankly, it is a little giddying to see a random thought take on such mammoth proportions.

It happened to some English tweeters too on Wednesday when they made the Everton workhorse Phil Neville a global star – as an antidote to the hype about Tottenham Hotspur winger Gareth Bale – by tweeting hilariously exaggerated tributes to his talents.

But a top tweet is a bit of Chinese lantern, dropping as quickly as it soared, until it falls to the ground all burnt out.

But if those of us who had had the initial conversation perhaps weren’t too surprised when a good few others joined in, to see it spin off into a global discussion was a thrill that every tweeter surely hopes to experience.

It’s a viral world. Just once, it’s fun to be at the site of the original infection.

But now it’s time for something fresh and totally different that might capture the world’s imagination.

So if you were to send a tweet to your 17-year-old self, what would it be?