‘Dark Water’: a bit of science

Hang on a minute, I appear to be on schedule… Well, my Master’s study (no pun intended) has officially restarted – so naturally procrastination has begun again too!

I did spend a lot of ‘Dark Water’ reeling – and truly freaked out about the “three words”… But my sciencey bit is going to focus on one of the many reveals of this episode: the eponymous ‘dark water’. So, basically, x-rays.

What is an x-ray then? It’s a type of radiation, on the same spectrum as the visible light we all know and love: the ‘electromagnetic’ spectrum. Only it is a higher frequency and energy (so it’s on the purpley side of the rainbow, just past UV radiation). A high frequency means a short wavelength – consequently, astronomers measure X-rays by their energy instead (in electron volts; eV). Typically X-ray radiation falls in the band of 100-100,000 eV.

We know of x-rays from machines in hospitals and dental surgeries, but actually some stars and nebulae give off the radiation naturally.

X-rays were first discovered almost 120 years ago, in 1895, by a German scientist called Wilhelm Roentgen – he conducted systematic experiments and eventually found that by passing x-rays through the body the bones got highlighted in great detail. Bones and metal (things like fillings) appear white, anything made up of muscle/fat/fluid turns out various shades of grey, and air-filled parts show up black.

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And for good measure:

Sounds great, right? Well, it is. And it isn’t. As with anything, x-ray use has its downsides. It is high-frequency ionising radiation, after all, so there is a slight risk of cancer – a higher risk for children or foetuses (which is why expectant mothers are not given x-rays). The risk is only slight because single DNA mutations most often come to nothing. There are mechanisms in place to either repair, remove or tolerate mutations – it’s very unlikely (and unlucky) for a single mutation to develop into cancer at the x-ray site. People operating various x-ray machines only take measures to protect themselves as otherwise they would easily build up a dangerous amount of exposure time in a single day.

But could we have the ‘dark water’ of Doctor Who? I’m a biologist, how would I know?!

So, the next shall be the last for a while. ‘Death in Heaven’ and then, possibly, Christmas…


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