Manuel Castells, in his new book The Information Age, refers to the Net and the Self. The relationship is a funny one - and I suspect that we're only just beginning to half-understand it. 

Before the Net became more or less universal, only three or four years ago, you and I had a special relationship with various places: one (maybe two) where you lived, one (maybe two, possibly three) where you worked, and a number of other places like hotels or conference centres. You moved in a time-space matrix between these places; twenty years ago, Torsten H@gerstrand and Tommy Carlstein began to map those movements, showing how complex they were. Phones helped bridge the gaps, but they wern't a true substitute. As John Goddard showed in his earliest work, as often as not they were used to make a preliminary approach to a face-to-face meeting; they created the need to meet just as much as (or even more than) they substituted for meetings.

Now, everything has changed - and is just about to change some more. I just bought one of the first Palmtop PCs with Windows software. It fits in my inside jacket pocket. With it came a catalogue showing all the things I could connect it to. Most were credit card connections to mobile phones. One picture showed a satisfied customer picking up his e-mail on what appeared to be the top of the Californian Sierras. (I hope it was important). Others showed delighted people having teleconferences on the web. I suspect all this is going to become commonplace within a couple of years.

As observers like Nicholas Negroponte and William Mitchell are always telling us, cyberspace is not Euclidian space. I just e-mailed Manuel Castells who was in Barcelona, but his address was in California; for I know, he may reply from Taiwan or Novosibirsk. I got a copy of a chapter from an Australian colleague that looked as if it had been written on the plane on the way back from our conference, and e-mailed from a transit lounge. We no longer know, or care, where anyone or anything is. Personalized lifetime phone numbers will symbolically complete that process.

And yet, and yet. The conferences are still happening; people are still finding that need to meet, and talk place to place, and even schmooze. The conference industry is one of the fastest-growing sectors of the new global economy. But in a sense, conferences are a part of the new spacelessness. Increasing numbers of us live in a transient world: work at home, work in a series of different meeting rooms which could be in offices but could equally be hotel rooms or airport lounges, work in hot-desk offices booked by the hour.

So a new geography of the information economy is emerging; in a world where most of the old spatial constraints have fallen away, the question is whether traditional city centres will maintain their attractiveness, or whether they will be supplanted by new edge-city concentrations where the key means of personal movement - the private car, the airplane and (increasingly, in Europe and Japan) the high-speed train - interchange with each other. The new 21st century centres could be places like Charles de Gaulle and Schiphol and Kansai International: edger cities on the metropolitan peripheries, competing with the downtowns. Or, perhaps, in-between places, those the Dutch planners call B-locations: Amsterdam South, Stockholm South, Ebbsfleet. One thing only is certain, and that is uncertainty: the future city region, lacking a fixed structure, is likely to be in constant flux.

Peter Hall is Professor of Planning at the Bartlett Faculty of the Built Environment, University College London.