Watty's been Tate Moderning again:

I rewarded myself for attaining the unlikely age of 41 by extending and renewing my membership of Tate (this year I'll get to St Ives!), but that has pretty much nothing to do with why we went there on Saturday. In truth, we wanted to take the boys on the boat trip between the two Tates, and everything else was just a bonus.

Like the current installation at Tate Modern. Every year, an artist is given the whole of the vast interior of the Turbine Hall to play with, and each of the four installations so far has been intriguing and interesting in its own way. This year's, an installation by the Icelandic artist Olafur Eliasson, is spectacular. The Weather Project is, on the face of it, quite simple, and from the descriptions of it in the papers during the week, intriguing but hardly spectacular. But it's one of those things you can't explain. You have to go and see it. Naturally, I'm not going to be prevented from trying to explain it just because it's impossible.

We entered from the south door - I really ought to know by now that these installations need to be experienced from the west, coming down the slope, but never mind - and it was immediately clear that there was something odd about the quality of light. As we went further, we could see that clouds appeared to be forming inside the hall, and everything was suffused by an orange glow. Further in, and we can see the promised sun-like object hung on the wall at the eastern end. It's very impressive, and seems somehow to shimmer, as if its upper half was reflected in water, which is, of course, impossible. The picture does not, I'm afraid, do it justice:

I would have needed some fairly sophisticated camera technology to capture it properly, but that should give an idea.

Gradually, slowly, I became aware of people craning their necks and looking up, and when that happens, you can't help but join in. Whereupon the astonishing realisation that the entire hall has gained a mirrored ceiling. Hung halfway up the 'sun', and also halfway up the hall, the strips of mirror don't alter the shape of the buillding, but alter utterly the way you look at it. They also provide fantastic entertainment, because you can lie on the floor and take pictures of yourself:

(that would be No. 2 Son making like a freefall skydiver in the middle there)

It's something which needs to be seen to properly understand it. I liked the way that you can go behind and above it, and see how it works, and that it was gently forming clouds as the day went on, and that everything was bathed in sodium lighting, so that we all looked a sort of muddy orange. And I liked the way it did what good art should do; it made me think, and it provoked a sense of wonder.

After that, we went to see Finding Nemo, which was just about the perfect end to the day. I quite like the birthdays I'm having at the moment...