Really, you could watch him all day, as you might some huge, rolling surf or one of those great thoroughbreds who makes the others look as if they are standing still.
When he leans down to the blocks after the ritual entertainment - last night he crossed himself and then pointed an admonishing finger to God in the event he wasn't paying full attention - you might just hear a dog bark in some distant street.
The world remains as absorbed and fascinated by Usain Bolt as it was when he first emerged so sensationally in Beijing four years ago and then a year later in Berlin when he broke again the 100 metres record he tore to shreds in the Bird's Nest stadium.
Sunday's victory in the 100m - in the second-fastest time in history - has clearly not satisfied the audience that becomes so animated when he comes into the stadium. It has merely triggered the appetite for more of the drama he can create with a small change of pace on the beach back home in Jamaica.
In the 200m semi-final last night he was merely the fifth-fastest qualifier - running 20.18, nearly a second outside his world record - but, of course, on this occasion no one looked at the clock, only the awesome movement of the man who might well bring further stimulation to London with a record-breaking effort in tonight's final.
That is hardly fanciful when you consider the nature of last night's effort.
His opponents in the second semi-final ran 200 metres. Bolt ran 100 then waited for the others. He was followed home by Anaso Jobodwana of South Africa and Alex Quinonez of Ecuador after he took a couple of long strides to the line. What was most significant last night was that the malfunctioning mechanics of his start appeared to have disappeared. On this occasion his first strides resembled all those others he made before almost going into reverse. He came huge out of the blocks and when he did so you could not help but feel a pang of sympathy for his young countryman and training partner Yohan Blake.
Some suspected that this strong and brilliant flyer might repeat in the 100m final here his victory in the Jamaican trials - and then reproduce his triumph in the 200m. Last night it looked the remotest possibility, even though Blake had once again led in the qualifiers and had himself eased back pointedly over the last 20 metres. You couldn't help recall the time Muhammad Ali reported that his sparring partner Jimmy Ellis had dreamt that he had beaten the great man in a world title fight. However, Ali reported, "The first thing he did when he came in to work this morning was apologise."
Blake has been christened "the Beast" but it was Bolt who last night again suggested inhuman powers.
When he came off the track, Bolt looked back on the easiest of chores. "This was all about going through as easily as possible," he declared. "This was the aim and it went pretty well, so I'm happy. This is my favourite event and I'm looking forward to it. People always doubt champions but I know what I can do and I don't doubt myself."
Blake finished in 20.01 but he is not likely to draw too much encouragement from that. Before the race he was saying that Bolt had no powers to intimidate. Of course, he admired him for all his achievements but he didn't fear him. He had beaten him twice, once over this distance, and he believed he could do it again.
It is the kind of thing you have to say when you are going against someone who has moved the world, who has things beyond its imagination and there is no doubt Blake is a most formidable sprinter. He moves with a wonderful smoothness and strength and if he was against anyone else you wouldn't be able to get a bet on him. However, the reality is the big man loping in the dusk and Blake should be careful in his dreams. If, this is, he doesn't care to make an apology.