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Prof Jeff Forshaw

The author of over one hundred scientific papers, Jeff Forshaw is a Professor of particle physics at the University of Manchester.  His key areas of study include quantum and particle physics as well as the Theory of Relativity.  He has written two popular science books on the subject, both with Professor Brian Cox, ‘Why Does E=MC²’ and ‘The Quantum Universe’.


We’re pretty sure that we understand the universe from the point when it was compressed to about the size of a beach ball.

On becoming interested in science

I was late coming into science.  So I had a…I think part of the reason why I like to try and popularise science and explain science to people is because I had a rubbish teacher at school.  I had no idea what physics was about and I’m not being facetious when I say that – is that right word? –   when I say that it was my worst subject at school.  Physics was my worst subject.  It was out of desperation that my dad got one of his colleagues to come and try and help me with my homework.  And I remember when he came round, it was, where should you balance a ruler on your finger in order that it would balance.  Where should you put your finger under the ruler to make it balance.  So a really simple question like, if you start loading weights at one end of the ruler, where should you move your finger to make it balance.  And the penny dropped at that point that you could actually work it out.  You could actually do a bit of maths and work that out.  You didn’t have to do it by trial and error and that meant that I could start to…I suddenly realised that there was this way to explain how things operate and work using simple ideas and maths.  So that kind of intrigued me that you could do that, that you could explain simple things around you using mathematics and so I started to get an interest in  physics then.  Unfortunately, I was towards the end of my O-levels and I went off and had a brilliant teacher at A-level who really ignited my enthusiasm to learn more about how things work.  So I didn’t really…I wasn’t really very much interested in things like cosmology or astronomy, I was more interested in things like, what’s light, how does a magnet work, what’s electricity, how do things work, and it’s addictive.  Once you start to get involved with that game to understand more and more, you start to learn a little more, you start to calculate and assimilate even more.  It’s a case of the more you know the more interesting it becomes.  So it was like a snowball.  It gathered a lot of momentum from the point where I started my A-levels, so by the time I started university I knew that I didn’t want to do anything else except physics.

On the job of a particle physicist

I’m a particle physicist, a theoretical particle physicist, which means I’m trying to understand what matter is made of at its most elemental level, so I’m trying to understand how the quarks, which make up the protons, which make up the nuclei, which live in the middle of every atom, how they behave, how those quarks behave and trying to understand what was happening, for example, at the very birth of the universe, so trying to understand how those particles behaved and how that then led to things like the structure of the universe at large and the structure of the galaxies that we see.  How it is that this understanding of these tiny things and how tiny things operate can pan out and describe pretty much everything that we see in the natural world.

On our understanding of the universe

We’re pretty sure that we understand the universe from the point when it was…when the entire visible universe – so that’s billions of galaxies, each galaxy with billions of stars – was compressed to about the size of a beach ball.  So that’s mind blowing as it is, right.  So from then on we can take the universe in that sort of primeval beach ball state and evolve it and get the structure of galaxies in the night sky and we get behaviours which we can probe using experiments like those at the Large Hadron Collider.  So, beach ball size up, we’re OK.  Before then it starts getting increasingly speculative.  But we dare to go back to a time when that beach ball was compressed down further to something like…many orders of magnitude smaller than the size of a single proton.  We dare to go back that far even, and at that point we start to lose our ability to calculate, but only then.  At that point we start to absolutely need to face a problem, which is called the problem of Quantum Gravity.  We need a theory of gravity, we need to change, or understand how to interpret, Einstein’s Theory of Gravity, which has been around since 1915, and how that is affected by the laws of quantum physics.  Until that point we can kind of duck that issue, but no more, so all the way back to then if we’re being hopeful.  Now the time of that, gosh, it’s something like ten to the minus forty seconds so it’s too small to get your head around, it’s, ten to the minus twenty seconds is too small to get your head around but ten to the minus forty is another twenty orders of magnitude.  So, the end of inflation is supposed to be around ten to the minus twenty six seconds or something like that.  

On furthering our understanding of physics

It’s such a difficult problem that it’s not really at the, um…we don’t have a good way of getting a handle on it using experiments, so one of the best ways might be through observing the universe at large, but even then we’re not directly probing the universe, not probing the theory of quantum gravity in any direct way, so it’s largely theoretical speculation at the moment, which is not a good situation to be in because physics, and all science, relies totally on experiment otherwise it descends into a mess.  It’s so easy to dream up a wrong theory and make things up.  It’s very, very, very hard to be right.  Most of the time scientists are doing things, they’re wrong, and it’s experiments more than anything that remind you of that and we don’t have good experiments that can test our theories of quantum gravity.  There is a theory of quantum gravity which people have formulated called string theory which supposes that actually the universe is not made of tiny particles, which is the situation that we understand at the moment, but if we could look small enough then we would be seeing tiny filaments of energy like little loops or string and that everything is made out of these tiny filaments of energy, not tiny particles, and that way of formulating the behaviour of all the elementary particles naturally includes gravity, but the problem is we can’t really calculate that theory such that we can make predictions that we could test in experiments, so our problem is probably one of the biggest unsolved problems in fundamental science but my guess is we’re quite a way off being able to answer it yet.  We have to be more patient.  But there are all sorts of other questions that we don’t know the answers to.  I don’t work directly on that problem because I think it’s too hard. 

So the ratio of the size of a proton, to a football, say, the corresponding step down to go to a string is much greater.  It’s many more orders of magnitude even.  So a string is to a proton what a proton is to something very large, much bigger than, I don’t know…maybe even the size of our solar system.  We’ve only got to the point with experiments at the Large Hadron Collider where we’re probing what’s happening inside protons at the level of about one thousandth of the size of a proton.  So we’re, ah, as far as getting down to the sizes involved in string theory we’re so far off that, you know, there’s no hope of building an experiment that can directly get that.  Microscopes are never going to be that good.

On not being scared to be wrong

Being frightened is a big hindrance to doing good physics.  Being frightened of asking questions or being frightened of seeming stupid or being frightened of getting something wrong.  So I think that fear of being wrong stops people from doing things.  You sort of stick to things you feel safe with and you don’t want to fail.  You don’t want to do something and get it wrong.  But to be a scientist you have to get it wrong all the time.  There’s a great quote by a friend of mine who says he loves it when he doesn’t understand something because it means he’s at the point of learning something new.  That’s a strange way…to embrace uncertainty like that is a really important quality I think of being a scientist.

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