Laughs aside, there's some real physics delivered here in a way that even the most disinterested watcher would surely find gripping.

Anyone wanting to build a time machine would do well to watch Greg McLaren’s startlingly imaginative one-man play first. Not only will you experience an absorbing outline of some the physics of this wondrous universe we inhabit and what space/time is all about, but the play will also make you think why you might want to travel through time in the first place.

The play has two expertly interwoven threads. One thread is a lecture given by a bright-eyed, indefatigable astrophysicist (played by McLaren himself) about the nature of universe, the problem of time travel and some possible practical solutions. The delivery of this lecture is maniacally energetic and very funny, with props and visual aids whose low-tech simplicity – cardboard, gaffer tape, chicken wire, oven gloves – adds to the humour.

Laughs aside, there's some real physics delivered here in a way that even the most disinterested watcher would surely find gripping. Our bold scientist dashes back and forth, one moment dangling precariously over the event horizon of a black hole on a length of twine or lassoing his audience’s heads with ‘cosmic strings’, the next simulating the universe with spiraling torch-lit chalk dust or demonstrating why a universal Terminator would be unable to murder his own long-dead grandmother in the past.

Yet there is more to this play than an entertaining lecture on physics. Early on the viewer begins to detect, almost imperceptibly at first, the second thread: a disturbing rift in the scientist’s past that he is half suppressing, half hurtling toward. This rift is revealed with increasingly vivid and alarming flashbacks of love, joy, pain and guilt. It is poignant stuff but never laboured, giving the play great emotional depth. Slowly, clues given early on in the play start to fall into place. The scientist’s lecture becomes increasingly frantic as his past drives him onwards to almost insane lengths of guilt and pain. And all the while, the laughs never stop coming – though more than one audience member could be seen wiping away tears. At the end, I wanted to watch the whole thing all over again.

How To Build A Time Machine is playing nearly every day at the Pleasance Below, Edinburgh, Scotland, until the end of August 2005.