I'd been invited along by the amazing comedy-geek-songstress Helen Arney to kick off the evening with some science demonstrations. I decided to pull together the work of some inspirational women in science and my own research (somehow!?) into a demo-packed journey through my view of some of the joys of science.
In preparation for the event the BBC paid a visit to my lab (STFC Rutherford Appleton Lab) to ask me a bit about being a woman in accelerator physics. They also interviewed three of the other speakers - you can see the video and associated article on the BBC website here.
Since I had to fit my talk into ten minutes I actually had to write it out (this is quite an unusual occurrence for me), but it does mean I have a nice record of what I said (or meant to say!) - so I thought I'd share it with you all here. I've edited it somewhat so it works better as a 'written' rather than 'spoken' piece. Enjoy!
|Presenting the first diffraction pattern using a human hair. Photo: Andrew Steele (2012)|
Good evening everyone. Tonight I’d like to share with you some of what I like to call the joys of science. To start with, I want to show you a simple demonstration that has to do with figuring out the structure of objects – objects which are too small to measure with a ruler, and often, too small to see with the human eye.
Let’s say that I want to figure out the width of a human hair. Measuring it with a ruler would be pretty tough, so it’s clear I need something smaller... I’m going to use light. The wavelength of the green light from this laser pointer is 532nm. If I shine it directly on the hair, it will cause a diffraction pattern – that is the light going round either side of the hair will interfere and produce a very distinct pattern of light and dark fringes. From the distance between the fringes, the wavelength of the light and the distance to the screen you can figure out how thick the hair is. (See photo above).
What if we want to look at something more complex? For example, a spring? What pattern will that make? Here is an image of the diffraction pattern the spring from a clicky pen makes:
If you think about it, when held side on, the spring looks like a wave. In this case the size of my beam is small, so when I shine it on the spring it only really sees one up part and one down part of the wave. That’s like two strands of hair at an angle to each other, and it produces a distinctive pattern.
I hope you can see that pattern, it’s actually a cross shape, and each of the arms of the cross also has light and dark fringes.
What’s remarkable about this pattern is that it’s almost exactly the same as the pattern that Rosalind Franklin would have seen in 1951 when she used X-rays to image a sample of DNA to capture her famous Photograph 51 - which was so instrumental in developing an understanding of the helical structure of DNA.
|Photo 51: courtesy of PBS/NOVA who also give a great explanation here|
It’s worth remembering that she would never have seen this demonstration, as the laser pointer wasn’t invented for another ten years. DNA is actually a double helix which makes the pattern a little more complex, but the cross shape is a distinctive indication that what we’re observing is a helix.
When I first tried this demonstration it reminded me that even though I wasn’t trying to understand DNA at the time, that by trying things out, by exploring something as simple as a spring, we can gather information that could revolutionise our understanding in a completely different area.
To me, there is an innate joy in that - in exploring the universe, and in trying to further human understanding. To understand or discover something new for the first time, to take something that confounds us and make sense out of it, to have the power to use what we learn to change people’s lives, that is what I mean by the joy of science.
That joy isn’t constrained by the colour of your skin, your age, your upbringing and certainly not by whether you’re a man or a woman.
I was surprised to realize that Rosalind Franklin’s work is linked to mine because these same diffraction techniques are used today with beams of light and also with beams of particles. Today we can see structures right down to the atomic scale, but first we have to produce the very well defined beams that are needed. To do that, we use a particle accelerator – and that’s where my work in designing accelerators comes in.
This isn’t a real accelerator, but it’s a very simple model of one – but it works on the same basic principles as a real one. If you take a positively charged particle and put it in an electric potential (or a voltage) it will move away from the positive side and towards the negative side – it gets accelerated.
(Note: you can see the same demo with more explanation in the Ri Channel's Demojam series pilot, embedded above).
So I’ve used a Van de Graff generator to provide the voltage in this bowl I have strips of metal, half of which are connected to the VdG and half to ground. So when the particle – a ping pong ball crosses a charged strip it picks up the charge and gets repelled. It hits the next strip and all that charge then goes to ground – the ball becomes neutral again. It then rolls around to the next positive strip, gets another kick and the process continues.
In this version my ping pong ball particle actually changes charge as it goes around, but that means that with each strip it gets an accelerating kick from the high voltage. In reality, protons don’t change charge – but we change the voltage very rapidly in time with the speed of the particles.
When they reach a high enough energy, pretty close to the speed of light, we extract the protons and we can use them for all sorts of different things.
One of the things people might use accelerators for in the future is to drive a safer kind of nuclear reactor called an ‘accelerator driven sub-critical reactor’. This takes us back to 1898 when Marie Curie discovered that a silvery-white metallic element called Thorium is radioactive. But she had no idea of what I’m about to suggest we do with it.
Unlike the Uranium fuel of a normal fission reactor, Thorium is what we call a ‘fertile’ material, rather than a ‘fissile’ one, which means that it can’t sustain a chain reaction on it’s own – it needs an external source of neutrons. That’s where the particle accelerator comes in – we could use it to create neutrons which then drive the reaction. If you switch off the accelerator you can switch off the reaction.
You need an incredibly powerful particle accelerator to do that – and that’s what I’m working on. I think this is such an elegant idea that even if it’s a BIG challenge, I think it’s an amazing thing that we can take the technology developed to explore fundamental physics, to find the Higgs Boson, and then use it to help solve the energy crisis. To me, that is an amazing part of doing science.
And I honestly can’t understand why any woman, man or dog on the entire planet wouldn’t want to be a part of that!
To finish my talk with a bit of a bang I though I’d get [the audience] to help me create a nuclear chain reaction. [The audience] were the nuclear fuel and when they walked in they each got two coloured balls – they were the neutrons. In the demonstration I supplied the external neutrons to get the reaction going. The idea is simple: if a ball hits you, you have to throw both of yours up in the air – they’ll hit someone else and they’ll throw theirs in the air and hopefully we’ll manage to create a chain reaction.
Hopefully I'll get a photo or video of that demo soon & I'll add it when it arrives!