Blue-white and shapely, an ice sculpture occupies the centre of a room filled with images of polar bears and penguins and the haunting calls of humpback whales. It attracts the pupils from Uddingston primary school, South Lanarkshire, like a chilly white magnet and all of them leave some trace of themselves on its surface - the shape of a hand, a fingerprint, a few crystals of frozen breath. "Why doesn't the ice melt?" Craig wonders.
"It does but it also grows, like a living thing," replies Dee Davison, education manager at Dynamic Earth in Edinburgh. "Water in the air freezes on to it and makes it bigger. And the heat of the room and people stroking it make it shrink. So it's changing all the time."
Polar Regions is one of 11 "earthscapes" at this most spectacular of millennium projects, where visitors take a voyage around our planet and back in time. The journey begins with the Big Bang. The children watch in awe as blazing star fields pass before their eyes.
In the next gallery they encounter the natural processes that shaped our planet: volcanoes, earthquakes and the steady creep of tectonic plates. Without warning the floor judders - and the children squeal. There follows a flight among mountains, one moment skimming the waters of a fast-flowing river, the next soaring over the topmost peaks, as the narrator describes the ice-ages: "Glaciers carve deep valleys, leaving mountain ridges as signposts of their passing."
So far the children have only been able to see and hear but now, as life appears on Eath, they get the chance to touch. They cross a pond of slimy green liquid - the primordial soup. "I'm definitely not eating that," says Max. Interactive displays show the immense variety of life on Earth and explain natural selection and extinction.
The children wander past stromatolites, trilobites, wiw-axia and cooksonia, the ancestor of all Earth plants. They meet tyrannosaurs, pterodactyls, sabre-toothed tigers and a hairy, ape-like creature most refuse to believe could be their ancestor. Then one or two notice a resemblance to certain classmates, especially when the hominid's nether regions emit a loud rasping noise. "Early humans had a high-fibre diet," explains Ms Davison.
The tour continues with a trip on a yellow submarine to study life in the oceans. A periscope provides a preview of the polar regions, after which frozen hands are warmed in a tropical rainforest, where spiders dart up and down the trees and butterflies flutter.
The journey ends with everyone seated in a circle gazing upwards, faces lit from below like early humans round a campfire, as earthquakes, tidal waves, lightning bolts, hurricanes and floods fill the sky. "The natural resources of our planet have been strained - have we the will to do something about it?" Sound and pictures fade, leaving a lonesome electronic beep and the small voice of a child asking "why?". The mood quickly lifts as the children descend on the gift shop.
Dynamic Earth, Edinburgh, is open all year. School parties should book in advance. Workshops available.Tel: 0131 550 7800.www.dynamicearth.co.uk