And on it goes. I have never known anything like it. Think of the agony of those poor relatives. They are not only enduring the disappearance of 239 passengers and crew aboard the Malaysian airliner. They must also put up with the continuing pain of not knowing.

Never in my lifetime has there been a disaster in which we have lost so many people, for so long. At the time of writing, we don't know which ocean they may be in or which continent they may be on. They could be anywhere in a gigantic arc of thousands of nautical miles.

I don't know about you, but I have become mildly obsessed with the story. I find myself reflexively checking to see if any new fact has emerged on the web. I am not alone. Across the world, it would appear that the fate of MH370 is the subject that engrosses the planet, the most-clicked story on every news site.

It is not just the biggest whodunnit we have ever seen. It is a whydunnit and indeed a whodunwhat. This is a world in which we thought that they could see everything: whether through CCTV or looking at your internet account or tracking your movements by the signal of your mobile phone. Now we learn that it is still a world so vast that an object as unmistakeable as a Boeing 777 - 63.7 metres long, 60.9 metres broad, and six storeys high - can vanish into the wide blue yonder.

As I understand the latest developments, it would appear that we are swinging towards the theory that some form of human intervention took the plane off the screens. At a point before the pilot made his final goodnight, somebody seems to have turned off the transponders and programmed the plane to make a left turn as it left Malaysian airspace.

But even if that information is undisputed, we are still left scratching our heads. If it was indeed pilot suicide - not unknown in the past 20 years or so - then why did the plane make this extravagant diversion towards the Andaman Islands? The evidence from the ACARS (Aircraft Communications Addressing and Reporting System) would seem to be that the machine flew on, possibly for hours, after someone had disabled communications. Why bother to do that, if you were a suicidal pilot?

In any event, it does not seem - from what little we know of the two pilots - that they were the kind of men to want to take their own lives. One was married with three children; the other apparently about to get married. Some have therefore suggested that the mission was not suicide but terrorism, either by one or both of the pilots, or by one or more of the passengers, or a combination.

That analysis would certainly cohere with the data that seems to suggest the plane's course was erratic - both gaining and losing height dramatically. One could imagine some kind of struggle in the cockpit, or a deliberate attempt to murder the passengers by causing decompression of the cabin. But if there is a terrorist motive behind the disappearance, why has no group come forward - as they did so after 9/11? It is now nine days since the plane vanished; the whole world is talking about it. Surely a terrorist group would want to maximise the publicity for their outrage? If not terrorists, then who?

Someone apparently decided to close down communications and take the plane decisively off course. That would appear to rule out so many of the alternative explanations that are still being canvassed. Some say there was a catastrophic structural failure, associated with a wing tip that was recently clipped in an airport shunt and had perhaps been inadequately repaired.

Some suggest it might be straightforward pilot error, of the kind we saw in the case of the Air France flight from Brazil - where the pilot failed to understand that if he kept the joystick pulled back, the plane would stall and fall. There is even a suggestion that the plane was struck by a meteor, or lost in freak weather. None of these theories are believable if you accept the radar evidence that the plane was a long way off course; and if it stayed on the right course, there is no wreckage where you would expect it.

It is in this vacuum that the conspiracy theorists are supplying the answers. There are some who claim it was engulfed by an alien mothership, or hijacked by North Korea, or stolen by the ''Illuminati''. Much has been made, sadly, of the easily explicable fact that the mobile phones of the victims appeared to be ringing after the plane had gone. Someone has even derived significance from the numbers: Flight 370 disappeared on 3/7 at a height of 37,000 feet and on a journey that was to cover 3700 kilometres, and Luigi Maraldi, one of the men whose passports was stolen, was 37.

So what? Indeed. I can't disprove any of these hypotheses. We all know in our hearts that we will eventually find the answer, and we all suspect that the eventual answer will be little consolation to those grieving friends and family.

But in the meantime, I take something positive from the sheer volume of global speculation - because it tells me that our species is still full of hope. We yearn to believe this story will turn out like Lost, or Flight 714, or Lord of the Flies - and that somewhere, incredibly, we will find those people alive.

Even more important, this is one of the first times I can remember when the whole human race has seemed at one in their sympathy and their concern for others. This is a global edition of that staple of local or national news, the unexplained disappearance of much loved people. It has the same plot, the same false leads, the same wild hopes, the same despair.

As the story of MH370 is followed around the world we are seeing how the internet and 24-hour news are turning the 200 nations of the Earth into a single global public, in a way we have never seen before.

Boris Johnson is mayor of London. Daily Telegraph, London