Daytime TV: Time and emotions

The impossibly youthful Professor Brian Cox asks a simple question, "What time is it?" (Horizon, BBC Two, Tuesday 9pm), but there is no simple answer. The Mayans thought they could tell the time. They knew, for instance, that there were 365 days in a year. But they also thought that the Sun required human sacrifices to keep it moving through the sky.

We have always looked to the heavens. And we have always been disappointed. We couldn't find God there, and now we learn that we can't even set our clocks by the stars. You'd think a pulse of light from a quasar would help us to be punctual, but not a bit of it. The spin of the Earth and the speed of the wind mean radio telescopes detect the signal at slightly different times.

For greater accuracy we must look into the atom, where a fuzz of electrons swarm around the nucleus. They emit light each time they leap from one level to another, which is 9 billion times a second. And there you have the principle of atomic clocks. But, says Brian, that still does not answer the question, "What time is it?"

Why don't we just look at our watches? Because what we think of as the present is really the past. It takes the light from the Sun about eight minutes to reach us. So if the Sun blew up we would not see the explosion for about the length of time it takes to have a cup of coffee and a Kit-Kat.

It is light that allows us to look back to the beginning of the Universe. Or nearly. We can't see beyond about 11 billion years. The consensus is that the cosmos is about 13 and a half billion years old. If we knew the moment that time began we could answer the question, "What time is it?" But we don't. It's amazing to think, reflected Brian, that "the first day of the Universe had no yesterday".

Unless, of course, it has always existed. And yet that still doesn't answer the question. No one seems know what time it is. Especially in our house. But watching Brian explain why we don't know made ignorance seem like knowledge. I am still grappling with the proposition that we move slowly through space, but at the speed of light through time.

Looking for the time of her life was Barbara (Man Hunters, Channel 4, Tuesday 10pm). Sixty-seven years old, she is one of an increasing number of women going on holiday to the Dominican Republic in search of, er, romance. "I look at men my age," said Barbara, "and think, 'No, no.'"

Fifty-four-year-old Joanne is similarly disappointed with the British male. "The old are boring, the young ones drink too much and none of them can dance," she sighed.

Barbara has a boyfriend called Luis who is 30 years her junior. "He is besotted with me," she beams, paying for another round of drinks. Joanne's boyfriend is nicknamed Spaghetti and has the figure to match. "He's really nice," she says, as we see him embracing a young blonde a few yards away. "Have you any pesos?" he asks her later. The women are lonely, the boys are broke. Neither party was really happy with the bargain, especially Joanne, who was several times close to tears.

In After Rome (BBC Two, Saturday 8pm) Boris Johnson gave a breezy history of Islam and Christianity. An imam, Mohammed Habash, stated that God is one but His names are many. History would have been more pleasant but less interesting if He'd been known to us all as Bob.

Boris spent a lot of time trying to stop his hair flying off his head. He should stop using Wash & Go. As he gushed about the splendours of Cordoba, his blond locks behaved like those people who always wave to the camera behind the reporter. Compared with Cordoba, London in the 10th century looked "frankly barbaric". Things haven't changed much since then, so, as Mayor of the capital, Boris has his work cut out.

The theme of civilisation looms large in Survivors (BBC One, Tuesday 9pm). Ninety-nine per cent of the population has been wiped out by the flu virus and only the most irritating are left. They talk of building a future but have difficulty constructing a chicken coop. Driving looks to be a pleasant experience. The roads are clear, apart from the odd maniac with a shotgun. And no one seems to bother much about time.