Water, water all around, but does it make you think?

There was the sun. There was the crack. And now there's the rain. The sun, which was actually made up of hundreds of little lamps in a semi-circular disc, was part of something called The Weather Project at Tate Modern. The crack, which looked like the kind of crack you might get if there'd been an earthquake, was called Shibboleth, and was also at Tate Modern. The rain, which is real water, in real drops, is part of a project called Rain Room, and you can see it at the The Curve gallery at London's Barbican now.

The sun, which lit up the Turbine Hall of the Tate in 2003, was meant, said its creator, Olafur Eliasson, to explore the ways "we have grown accustomed to the weather as mediated by the city". The crack, which split the floor, or what looked like the floor, of the Turbine Hall of the Tate in 2007, was meant, said its creator, Doris Salcedo, to make you think about "the experience of racial hatred". The rain, which falls from a ceiling in the Barbican, is meant, say its creators, who call themselves Random International, to make you think about the "growing scarcity of this vital resource on our planet".

The sun, as far as I can remember, made me think about how much I longed for the summer. The crack, as far as I can remember, made me think about earthquakes, and drought. And the rain? Well, I was damned if anyone was going to tell me what to think about the rain. I'm used to rain. I live in England. But still, I thought I'd find out.

There are queues. There are, in fact, long queues. And then when you walk in, and down a dark passageway that feels like the night, you're hit by the sound. It's the sound of the tropics, the sound of the monsoon, the sound of beating, bouncing, driving rain. And when you see it, and the light shining through it, a mass of silver drops in a big, dark, space, you almost gasp.

You almost gasp, too, when you walk into it, and the rain is all around you, but you're dry. You know that it must have something to do with sensors, and cameras, and valves, but it still feels like a miracle. It makes you feel like a god because you can, for the first time in your life, control the rain. It makes you feel like a god, too, because you almost feel that you're in a world that you created. It's a world where a clear liquid can sometimes look pink, or green, or gold, and where you can suddenly see a rainbow.

Gods fail. At one point, I got quite wet. But I didn't want to leave it. I didn't think about the "growing scarcity of this vital resource on our planet", but I did think about what lovely patterns there were in the light and the water. I thought of the fountains in Moorish gardens, and of how water often made you think of peace. And I thought that the people who had made this thing had made something that was clever, and beautiful.

But it also made me think that the thing about art, if you call it art, is that it can make you feel all kinds of things, and it can make you think all kinds of things, but the one thing it can't do is tell you what those thoughts and feelings should be.

'Rain Room', The Curve, Barbican, London EC2 (barbican.org.uk) every day from 11am-8pm, and until 10pm on Thursdays, admission free