Constant Speed, Sadler's Wells, London

This is Einstein's centenary year, and the Institute of Physics had the bright idea of commissioning a new work from Rambert Dance Company for the celebrations. Mark Baldwin's Constant Speed, his first new dance as director of Rambert, starts with scientific theory and comes out light and fluffy. That mirrorball may illustrate the concept that light arrives in packets, but it's still a mirrorball.

Much of the sparkle comes from the music. Looking at the music of Einstein's Vienna, Baldwin plumped for the operetta composer Franz Lehar. Ben Pope's lively arrangement is full of lilting tunes.

Michael Howells' costumes come in every shade, but they can be unflattering. The women's pleated dresses suggest 1930s chorus girls, but their skirts ride up awkwardly. And it's hard to see faces under frilled or pompom headdresses.

Starting with the idea of Brownian motion, Baldwin casts his dancers as molecules moving in space. Blocks of dancers charge about the stage, arms solemnly pumping. They'll stop, plunge into dance steps, and sprint on again. The timing is nicely comic, and there's some throwaway virtuosity, casual handstands or cartwheels.

Solo dances are effortful. Baldwin is fond of shoulderstands, kicks and wriggles, and he often sets them hard against the music. He likes to move in and out of his scores; the dance will suddenly relax when it's allowed to go with the musical flow. The sense of release is striking, but there's some strenuously deliberate choreography. Even so, the Rambert dancers look sleek and bold throughout.

Company dancer Mikaela Polley made Momenta for this year's choreography workshop. The new score, by Patrick Nunn from the Royal Academy of Music, is full of rippling piano, flute and violin lines. Polley uses her dancers fluently, especially in corps work, and she creates clear stage pictures.

Polley also danced Minerva in Antony Tudor's 1938 Judgement of Paris, which shows the three goddesses as weary prostitutes in a sleazy bar. The women, walking as if their high heels are giving them blisters, do their best to conserve energy as they bump and grind. One slides almost into the splits; another waves two hoops with anything but a flourish.

Dark Elegies is major Tudor, one of his most celebrated works. Ashley Holland sings Mahler's "Kindertötenlieder", songs for the death of children, from the side of the stage. The dancers, in peasant costume, mourn an unnamed tragedy. Lucila Alves dances with weighted grief in the third song. This is an honourable revival, but it doesn't have that weight all the way through. The men, especially, are too light, too balletic. Tudor's choreography is still impressive, the dancers flowing in and out of circles, or sitting in quiet grief as others dance. Paul Hoskins conducted a fine performance from London Musici.

To 28 May (0870 737 7737)