Could you be Doctor Who?

When you're watching Doctor Whothis Christmas, you might wonder if there really could be such a thing as a two-hearted, 500-year-old alien who can regenerate every time he dies. Claire O'Connellfinds out if such things could be possible

Regeneration

Eleven people have played Doctor Who. The story goes that the Time Lord can regenerate when close to death, and so he changes in appearance – which explains the situation when a new actor is ushered in.

This whole-body regeneration is something that humans can’t do in reality, although some tissues and cells within our bodies can renew after damage, particularly when we are younger.

Some animals are able to regenerate body parts though. If an adult salamander loses an arm or leg, it can regrow that limb: it’s thought to be the only back-boned animal that can pull off this trick. But if you look in other areas of the animal kingdom, some species have even more amazing powers of regeneration. One marine animal, Hydractinia echinata, can even regrow a lost head.

Understanding regeneration in real life (rather than Doctor Who-style morphing) could help us find better ways to help humans heal after serious injuries or illness.

Age

Doctor Who is a mysterious character – even his age is uncertain, but he could possibly be between 500 and 900 years old. Could humans ever live that long? One of the oldest humans on record was Frenchwoman Jeanne Calment, who lived to be 122, and today reaching the age of 100 is becoming less rare.

Scientists try to understand how the ageing process works by looking at various “models” in the lab, and one of the supermodels is a tiny roundworm. Studies of this creature show that factors including the amount of food it eats and particular changes, or mutations, in its DNA, can affect its life span, and research is looking at how this works.

Mice may also offer clues about ageing, and scientists are looking at how quieting down a process called inflammation in mice could lengthen their lives. In another experiment that has just been published in the scientific journal Nature, researchers switched off an enzyme called telomerase, which helps to protect the ends of DNA strands in cells as they get older. The mice aged quickly but when the telomerase was turned back on, the mice appeared younger, even inside their cells.

It’s a long way from getting a human to 500 and beyond but scientists are hopeful that by understanding how we age we can do it more healthily.

Time travel

When the Doctor climbs into the Tardis he gets transported through time. It makes for great plot lines but is time travel really possible? To a certain extent it might be but not quite on the scale that Dr Who does it. In theory, time is relative – it speeds up or slows down depending on how fast we are moving relative to an observer, and also on our mass, which is affected by the gravity we are subjected to.

Experiments that use extremely accurate atomic clocks bear this out: clocks on satellites that whizz around our planet move at a different rate than those on Earth. These time differences are tiny though and while they mean that special calculations are needed to keep services like GPS accurate, it would hardly be enough to excite a Time Lord in search of adventure.

As an aside though, here’s a thought: on clear nights you can get a glimpse way back in time just by looking at the sky. The light you see from the North Star took over 400 years to reach your eyes.

Evil aliens

Could other planets really be teeming with sophisticated beings who are hell-bent on making our lives difficult? So far the evidence is much less dramatic. Research has discovered molecules in places other than Earth that would be needed for any life to evolve in a form that we are familiar with – these include water on Mars and oxygen in the atmosphere of one of Saturn’s moons. And the search is hotting up among planets that orbit stars other than our Sun. We know of over 500 such “exoplanets” and just this month scientists published details of a possibly cloudy atmosphere on one that is 40 light years from Earth.

Strange anatomy

We humans have just the one heart each, and Doctor Who has two but did you know that an octopus trumps both of us by having three hearts? Two of them pump blood through the animal’s gills, while another pumps blood around the rest of the body.