How fast does a T Rex run?

From my Guardian column:—

 'How fast does a T Rex run? 20 years ago, the technicians at George Lucas’s effects house, Industrial Light and Magic, laboring to finish Jurassic Park in time for its June 11th release date, made a decision whose effects would reverberate for decades to come. “We had a zillion arguments about it,”said animator Steve Williams.  Some argued, based on the animals estimated mass, that it ran slower than a jeep, the only problem being that a jeep was precisely what it was required to chase in Spielberg’s film.  Others argued that it ran more like a lion: never unless it had to, and if it ran, only for a very short period of time, moving very fast. “Using that logic,” said Williams. “I had to throw physics out the window and create a T Rex that moved at 60mph, even thought its hollow bones would have busted if it ran that fast.” 

That decision — cheating mass to achieve the desired velocity — set the pattern for the bendy new laws of physics that were about to unfurl. The eighties had been about nothing if not mass, when roid-head heroes came on like one-man biological armies, wiping out whole buildings, neighbourhoods, villages, with one clench of  oily pectoral. “He fills the space, and you have to go with that,” said James Cameron of Arnold Schwarzenegger when casting The Terminator, originally a lithe assassin with a   buzz cut, upturned trench-coat, capable of disappearing into a crowd. What he got was 220 pounds of Austrian bodybuilder, who could no more disappear into a crowd than he could perform a pas de deux. As the eighties boomed, so too did the biceps of its movie heroes. ”I always believed the mind is the bestweapon”  insisted John Rambo, before strapping some beefy rocket launchers to his forearms, in case his mind wandered. 

That all changed in 1993. “Lizard eats Arnie’s lunch,” ran Variety’s headline, after Jurassic Park smushed Arnie’s appropriately titled Last Action Hero at the box office, ushering in a brave new world of computer-generated effects in which the bulk of Arnie, Sly, Bruce and the gang was suddenly a drag —  un-aerodynamic. As The New Yorker’s David Denby wrote in his review of X-Men United (2003):—

“Gravity has given up its remorseless pull; one person’s flesh can turn into another’s, or melt, of become waxy, claylike, or metallic; the ground is not so much terra firma as a launching pad for the true cinematic space, the air, where bodies zoom like projectiles and actual projectiles (bullets say) sometimes move slowly enough to be inspected by the naked eye. Roll over Newton, computer imagery has altered the integrity of time and space.”

This brave New post-Newtonian universe would belong instead to   swift, svelte, low-cal metrosexuals like Keanu Reeves, Matt Damon, Leonardo di Caprio, Joseph Gordon-Leavitt and Andrew Garfield  — buff but not ripped, able to cling to a window ledge by their fingertips, or run upside down a corridor, or wrap their tonsils around the gobblydegook of a script like Inception, whose   exposition levels alone rendered it a no-fly zone to monosyllabic grunters like Sly and Arnie, whose eloquence at best stretched to a gruff “screw you” as he plunged a power drill into a man’s chest. Jurassic Park put paid to all that — it put machismo on the extinction list.'