Why is Doctor Who always a Time Lord and not a Lady? Journeys to the centre of the Earth; The meaning of a hiding to nothing

Why is Doctor Who always regenerated as a Time Lord, not a Time Lady?

In Doctor Who the process of regeneration is the renewing of every cell in a Time Lord's dying, damaged or unwanted body. Since Time Lords (and Time Ladies, and perhaps even Time Tots, as the children of Gallifrey are known) can change species when they regenerate, there is presumably no reason why they can't also swap sex. There's certainly nothing in the TV series' history to contradict this theory and indeed no way of telling whether the Master, the Doctor's sworn enemy, spent one or more of his 13 wasted lives as a femme fatale called the Mistress.

Kieran Grant, London N22

Time Lords can be male or female. One of Tom Baker's companions was actually a female Time Lord called Romana who regenerated between seasons and I also understand that one of his recurring enemies was another female of the species called The Rani.

Apparently, the only way a Time Lord can regenerate as a member of the opposite sex is to commit suicide. This has happened at least once to my knowledge, in a Doctor Who Unbound audiobook called Exile, where he commits suicide and becomes Arabella Weir in order to hide from pursuers.

Guy Thomas, Canterbury

Why the Doctor has never managed to exchange his Y chromosome for a second X is one of the universe's great unsolved mysteries. Had he managed to do so, we might have been fortunate enough to experience the doctorly delights of the likes of Honor Blackman, Judi Dench, Sheila Hancock, Maggie Smith or Kathy Burke. Whatever the reasons for such rigid gender typecasting, lack of available talent isn't one of them.

Sheila Kirby, Esbjerg V, Denmark

The world's tallest building is the 828m Burj Dubai, but what is the world's deepest man-made structure?

Various mines and deep geological repositories for nuclear waste approach one kilometre. At 24.5km, Norway's Laerdal tunnel is the longest road tunnel in the world, and also up to 1400 metres deep. However, the record for the deepest hole is held by the Russians, who started drilling the Kola Superdeep Borehole in 1970 and reached the depth of 12,261 metres in 1989. The purpose of this hole is to study the continental crust. However, this represents only about 0.2% of the journey to the centre of the Earth.

In a tongue-in-cheek paper published in the science journal Nature, David Stevenson, professor of planetary science at Caltech, explains how a grapefruit-sized unmanned probe could reach the centre of the earth in a week or so. The first step would be to detonate a nuclear bomb to generate a crack in the Earth's crust 30cm wide and several hundred metres long and deep. Molten iron containing the probe would need to be poured into the crack the instant it formed. Being denser, the iron would sink, which would lead to the release of gravitational potential energy, melting the underlying rock. Once the glob of iron had passed, the rock would close up again. Data would be sent to the surface as vibrations. But the £6.5bn price tag means it will not be happening any time soon.

Mike Follows, Willenhall, W Midlands

"A hiding to nothing" – I know what it implies but it doesn't make sense. Can anyone explain?

It refers to a situation where one has everything to lose and nothing to gain. It is used (often in football) to describe a contest against supposedly inferior opposition where winning would be expected and produce little credit, while losing would be a calamity. The hiding refers not so much to the other team's performance but to the public outcry and humiliation.

The meaning of "hiding" is from the association of corporal punishment with the tanning of skins. Hence, "I'll tan your hide" and "give you a good hiding". So winning the uneven contest would be "nothing", while losing would be a "hiding".

Martin Skinner, Leamington Spa, Warks

Why are there no female Formula One drivers?

Due to their ancestors' roles as (respectively) hunters and nurturers, men's and women's brains evolved different pathways to help them make decisions. Women specialised in more nuanced, longer-term decisions, while men learned how to make good instant decisions. It's a bit of a generalisation, and there are obviously exceptions – the female Red Arrow, for instance, and the men who work in caring professions – but together with their numerical advantage, it explains why men become (and want to become) racing drivers and fighter pilots.

Nick Marsh, Sutton-at-Hone, Kent

Any answers

In folklore werewolves look like real wolves. That's the whole point – you don't know which is real and which is supernatural until it's too late. So why in films and TV do they look like very hairy people?

Susan Deal, Sheffield

What is the origin of the mortarboard as an item of academic dress? Why is it worn by graduates at some universities but not at others?

Lilian Dunlop, Manchester

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