The insatiable, and mostly inspiring, efforts of Google to contain all the world on a 14-inch screen have taken another giant leap forward with the unveiling of the Google Art Project.
Working with 17 of the world's leading galleries and museums - from MoMA in New York to the Rijksmuseum in Amsterdam, from the Hermitage in St Petersburg to London's National Gallery and Tate - the project takes the corporation's street-view technology behind closed doors. It allows you not only to wander, at the touch of a mouse, the corridors and halls that contain many of the greatest masterpieces ever made, but also to view some of those paintings in finer detail than if you were standing in front of them.
The sharp focus is made possible by 14-billion-pixel photography that brings the most delicate brushstrokes into microscopic relief. So far, this headline-grabbing technology is restricted to one painting per gallery - Holbein's The Ambassadors is the National's mesmerising example, Van Gogh's Starry Night is MoMA's - but it seems inevitable that it will eventually illuminate far more of the collections.
The almost magical potential resource raises many questions, not the least of which is whether viewing online will ever be a substitute for the real thing. (Along with the not-insignificant supplementaries: if it is, what effect will this have on gallery attendance and on our idea of art?)
After spending a few hours on the site (yet another new way of digressing on a screen), the answer to the first part feels like a qualified no. Looking at a painting on screen, however vivid the detail, is wholly different in kind from standing in front of it. Though there is genuine wonder in the backlit clarity of the images - in Bellini's St Francis in the Desert from the Frick Collection in New York, for example, you can make out the artist's fingerprints in the surface of the paint - as with any reproduction, what is lost is a sense of the painting as a physical object, as a little framed force field.
Mostly absent too, therefore, is that uncanny sense of communion that great paintings sometimes provide, the feeling that you are in the human presence of something that can talk to you directly across time and space; one element of that latter feeling undoubtedly derives from the sense of effort that brought you in front of the painting in the first place (the closest many of us get to pilgrimage).
You look at the on-screen pictures, as a result, with a somewhat more academic than emotional eye. It's not a reductive experience (how could this extraordinary level of free access to some of the world's most enduring images ever be that?), but neither is it the same thing, quite.
Despite this reservation, Nicholas Serota, director of the Tate, was probably right when he claimed the Google project as "the first global art collection" and one which gives us the clearest sense yet of "the digital future for museums".
There was also, from Serota, inevitable talk of the website bringing "communities of like-minded visitors together to connect in ways that aren't always possible in the gallery", which I suppose means that visitors to the site will be able to share responses to particular paintings in a way they might feel reluctant to do while standing next to a stranger in front of a Botticelli.
The gallery directors involved in the project are of course confident that the online versions of their collections will extend curiosity rather than satisfying it; that the art project will act as an advertisement for those who can get to the galleries.
One can only assume that the museums not involved - the Louvre in Paris and the Prado in Madrid, for example - are less sure of that equation. As always, with the digitisation of culture, the answer will not be long in coming.