It’s National Science Week! Woow! From the 11th to the 20th of March, the UK science community is showcasing everything science – starting with some atrocious maths skill (there’s only 7 days in a week science people!). In celebration we’re taking science as our theme this week, starting with today’s article: the science behind Doctor Who.

Let’s start with the magnificent machine that the Doctor uses to jump between periods in history or the future. Could time travel ever be possible? Well, if Einstein is right with his general theory of relativity, then no. However, let’s say that under certain circumstances we might me able to break the laws of general relativity. Now we’re talking!

For time travel to be possible, we must understand a bit about black holes. Lovely things, black holes. If they were to be graphed by their gravitational pull, the graph would look a event horizonbit like the diagram to the left. The drop is known as a gravitational well and if you’d like to find out more about that, take physics (the best science). See the part labelled ‘Event Horizon’, that is what we are interested in. It is at this point that a black hole becomes a black hole. From this point downwards you would have to travel faster than the speed of light to escape the gravitational well. As I’m sure you are aware, the speed of light in a vacuum is a constant and cannot be exceeded. However, if we were able to travel faster than the speed of light and get behind the event horizon and pop back out again, we would have travelled through time. Yes, I know, sounds completely bonkers and makes no sense whatsoever, but welcome to physics; nothing makes sense, everything works somehow.

Let’s take a look at the Doctor’s favourite tool, his sonic screwdriver. How this works, goodness knows, but that doesn’t mean there isn’t some physics behind it. Let’s start with the sonic part. This refers to sound and, in this case, very high pitched – or high sonicfrequency – sound. These high frequency sounds are known as ultrasounds and are most commonly used for sonar and ultrasound scans. These are far too high pitched for the human ear to hear so it can be deduced that that whirring noise the sonic screwdriver makes is an addition the Doctor added so he could tell it was working. How this opens a door? I have no idea. But it does mean he can do a whirring and find out where the nearest person or obstacle is. How this works is that the ultrasound travels outward from an emitter. It then bounces back off of surfaces and is collected by a receiver. The signal is then used to calculate the time taken for the wave to go out and return, thus giving you how far away things are using everyone’s favourite ‘speed = distance/time’.

So there you have it. A tiny piece of the science behind the fantastic world of Doctor Who.