Tomorrow, April 29, as the royal wedding draws to an end and Prince William kisses Her Royal Highness Kate Middleton on the balcony of Buckingham Palace, 2.5 billion people — a third of the world’s population — will be watching. It will be the largest royal wedding in history, beating out the 750 million who watched Prince Charles and Princess Diana marry in 1981, and possibly making it the largest televised event of all time.

It is estimated that over 2 billion people will watch the royal wedding on television, a further 400 million viewers are expected to watch the event live on YouTube, and yet more will watch live internet streams provided by broadcasters like the BBC and CNN. While large televised events are nothing new — large sports events like the Olympics regularly pull in audiences of more than a billion — there has never been a live, internet-streamed event like the royal wedding. The Winter Olympics saw 130,000 concurrent online viewers, and YouTube’s biggest live event to date was a U2 concert that ‘only’ pulled in 10 million streamers.

The fact is, no one really knows whether YouTube will be able to handle 400 million live streams. Google is no stranger to large amounts of traffic — it handles billions of search queries a day — but that’s just text and static images, with each search totalling maybe a few hundred kilobytes. Streaming video and audio is another beast entirely: a streamed 720p video uses somewhere in the region of 2Mbps, or around 200 kilobytes per second.

What, then, is the total bandwidth requirement for 400 million concurrent YouTube streams of the royal wedding? If we assume that Google will provide a 720p stream — anything less, and you wouldn’t be able to make out the elated faces of royalist revelers — then the starting point for the total, peak bandwidth is 2Mbps multiplied by 400,000,000, for a total of 800,000,000Mbps. That number, in case you were wondering, is massive; it’s 800,000Gbps, for a total of 100,000GB of data transferred every second, or 6,000,000GB per minute. Your computer’s hard drive probably has a capacity of around 1,000GB.

While nothing on the internet even comes close in terms of bandwidth or raw data transferred, we can attempt to draw some feeble comparisons. The average home internet connection is around 10Mbps, some 80 million times smaller than YouTube’s requirement. A single DVD movie, which is around 4GB, could be transferred 1.5 million times per minute using the same connection.

The truth is, while no one knows the exact capacity of the internet’s fiber backbone, 800 million megabits per second will represent the biggest stress test the internet has ever had to face. At the very least, the internet will slow down as smaller links and routers become saturated — but it’s also possible that YouTube will simply max out its capacity long before 400 million viewers can tune in to the stream. Routers might crash, however, and YouTube might become inaccessible for those seeking sneezing pandas or giggling penguins. The other alternative is that Google might provide a lower-quality stream, but even at 320p or 480p the total bandwidth requirement would still be utterly insane.

And yet we’ve only looked at the internet bandwidth requirements of YouTube. If you take a glance at the bigger picture — the 2 billion people who will be watching on TV — it’s safe to say that, come the fairytale kiss on the balcony, every one of the world’s digital networks, internet, satellite, cable, and radio, will undergo its greatest ever trial by fire.