Who can resist the lure of journeying back to the dawn of time, to the centre of the Earth, to the very beginning? Obsession with our origins and with the primeval question “Why?” has led us in two directions. On the one hand, we have science fiction and Hollywood blockbusters with their monsters and erupting volcanoes; on the other hand, we have palaeontologists toiling in labs. Yet in real life the two areas have always been split. You could either go to the cinema to gawp, or stare at the labels in museums to analyse, not both. Until now, that is. The Natural History Museum, in its pound;12 million transformation of the former Geological Museum into the Earth Galleries, has produced a blockbuster of its own.

You get to the Earth Galleries (two completed a couple of years ago, the final four completed this summer) through the renovated atrium in the Exhibition Road entrance; past the memorials to great scientists and Creation myths, up the giant escalator which pours you through the innards of a tormented iron Earth-globe into the centre of the Earth.

Ignore the display on volcanoes and earthquakes and its companion on surface erosion. Wonderful though they are, you need all the time you’ve got to get the best from this visit. The place to start is downstairs in the From the Beginning gallery.

So, there you are, back at the dawn of time and pretty wonderful it is. Expanding rapidly from the Big Bang outwards, this gallery uses film, sound and beautiful design to explore the vastness of time and the hugeness of space.

Museums these days have to have a built-in a “wow!” factor. In From the Beginning, whether you are watching the video loop on the formation of the Earth, or following the interactive video panels on the composition of the planets, or even musing on what came before the Big Bang, every remarkable sight is geared to affecting how you feel as well as what you think. This is no mean feat when it comes to the movements of tectonic plates and the infinitely slow rendering of the primeval landmass into today’s continents.

As well as rendering visitors speechless, From the Beginning has also to match each individual visit of say, an hour, with the passage of 4.5 billion years. Lighting, colossal ultraviolet graphics, inlaid marble on the floor and careful selection of extraordinary specimens give the visitor a feeling of really moving through aeons of time.

The basic linking device in the gallery - a steel time-line - cleverly uses this most familiar of classroom maths strategies to impart a sense of the shifting “now”, with every 25 million years marked out. You move through snapshots of geological history, illustrated by panels, rock and fossil specimens and interactive question boxes, each of which crystallises our sense of the ancient past, which is lying, literally, beneath our feet.

One of the gallery’s most fascinating displays is on mass extinctions. We all know about the dinosaurs - and there is a marvellous toothy Bradysaurus looming in a glass cage to remind us - but less well-known is the Burgess Shale. The subject of American palaeontologist Stephen Jay Gould’s prize-winning book, Wonderful Life, the Burgess Shale holds a whole non-vertebrate family of life genera, which was buried in its entirety beneath a mudslide some 500 million years ago, leaving no descendants. Here you can see one of these strange, never-before-seen creatures lurking on a wall panel. It looks like nothing now on Earth - because, of course, there is nothing now on Earth that looks like it. The museum has reconstructed this and other stories of doomed life-forms, pointing out that it is only by chance that we have any fossil records at all: most fleshy bodies with their bones would have been slowly eaten away by bacteria.The gallery’s foreshortened perspective line draws you on to the final display on the emergence of homo sapiens, tracing out some of the complex relations between our various hominid ancestors and Neanderthals. A large crystal ball twinkles at the far end and you can merge the story so far with the unknown future...

Or you can continue the journey, into the Earth’s Treasury section. This houses most of the former Geological Museum’s display of minerals and gems. Some - mainly specimens which represent the geological diversity of the British Isles - remain catalogued and shelved in modernised versions of the old-style glass cases. Here in the small Earth laboratory gallery above the shop you can quiz computers about geological finds and distributions. But in the main Earth’s Treasury gallery, science seems suspended for a while as the wow-factor takes over. Gems of all shapes and sizes glitter seductively beneath their cases.

These exhibits tend to have a marked gender-stereotypical effect on visitors: the female of the species gazes with rapt attention, whether at the cut and polished peridot or the big chunks of amethyst. Males, on the other hand, make for something a little more macho, like information on the weights and properties of precious and base metals and a display of fluorescence in uncut minerals.

It is slightly better for boys when the gallery moves on to minerals and the formation and uses of clays and fossil fuels, but even the final case showing the prevalence of silica and the amazing number of uses to which we put its derivatives (computer chips, anyone?) signally failed to re-engage the attention of most boys on our visit. Although a demonstration of the formation of different rocks was popular with both genders, perhaps more could have been made of the nature of crystals, and limestone cave-formations, for instance, might have been better sited here than in the Surface gallery upstairs.

Within the Earth’s Treasury gallery, there is a distinction which the curators have not made explicit - between the substances themselves and their uses. Diamond, for example, is the hardest substance on Earth by far, but that is not why we call it a gem. It’s a gem because of its “gemminescence”, that is its quality of holding and diffracting light. So prettiness, jewellery and personal adornment are part of the meaning of gems for human beings, though not of mineral substances themselves. The display does no more than hint at this aspect, typically showing a collection of rings on some glass rods. Weren’t rings designed for fingers? Isn’t treasure supposed to be ogled over?

A final gripe concerns the Earth Galleries Globe cafe, which shuts at 4.30pm. An extension to nearer the closing time of the museum would significantly add to the pleasure of the day as well as enable visitors to disentangle going back to the beginning of time from primeval rumblings in the stomach and gaspings of thirst.

The Earth Galleries at the Natural History Museum, London SW7 5BD, tel: 0171 938 9123. Opening times: Monday to Saturday 10am-5.50pm, Sunday 11am-5.50pm. Entrance fee: pound;6 for adults, pound;3 for children, pound;3.20 concessions. Pre-booked school parties are free, as are education packs, tel: 0171 938 9090