It was a scientific match made if not in heaven, then in manmade conditions approaching the big bang: Brian Cox and Jeff Forshaw first met at a particle collider in Hamburg 15 years ago. They have collaborated on various scientific projects ever since and are now both professors at Manchester University's Particle Physics Group and are involved in research projects at Large Hadron Collider at Cern, Geneva.

Jeff explains their relationship thus: "Apart from Brian's pretty face, it's the fact that we both have this very direct, visceral love of physics, so we both really love what we're doing."

Their second book together, The Quantum Universe: Everything That Can Happen Does Happen, is published by Allen Lane on Thursday. It's as breezily a written accessible account of the theory of quantum mechanics as you could wish for – from the Planck constant to the Higgs particle and everything theoretically in between. Observers looking for evidence that science is the new rock'n'roll should note that the book jacket is designed by Peter Saville of Factory Records fame.

Brian's frequent TV appearances, handsome features and drainpipes have led to him being described as "something of a sex symbol" by the Daily Mail, a spoof column in New Scientist and satirical YouTube clips. Jeff, however, cuts a more conservative jib.

We asked readers to send in questions via email, theguardian.com and Twitter and you responded magnificently with queries both theoretical and practical, covering subjects from the subatomic to the infinite. Here is a selection of their replies.

Physics

Is there a centre of the universe?

Marjorie Ainsworth, via email

JF: It's a common misunderstanding of the big bang that the universe exploded into something, like a firework went off or something like that, and there was a centre that spewed out into something.

BC: That seems to imply that everything is flying away from us and we're therefore somehow in a privileged position; that isn't true. The way it's often described is if you imagine some bread with raisins in it that you're baking in the oven and as you heat it, it expands. On any particular raisin, if you look, you can see all the other raisins receding from it. So it's space that stretching, it's not that everything's flying away.

JF: It's the big stretch, not the big bang.

If everything came from a singularity, what created it?

bbmatt, via web

JF: What created the singularity? No idea. But that doesn't mean that some people haven't tried to come up with ideas. Anyway, everything coming from a singularity is a confusing line of questioning because the universe was probably infinite at the time of the big bang so it didn't really come from a singularity. It came from a singularity in the density, but I expect that the person who's asked that question imagined that the universe came from a point.

… but that's very unlikely. We don't know what happens deep inside a black hole, so when the density of the universe gets very, very large then our calculations cease to work, so the honest answer is that before we reach the singularity, our ability to calculate fails. But that's not to undermine how accurately we can calculate, because we claim to understand the behaviour of the entire visible universe winding back through the big bang to a time when it was the size of a beach ball. So that's all the billions of galaxies and all the billions of stars in the galaxies compressed to about the size of a beach ball, which is pretty impressive.

BC: General relativity, quantum mechanics, those things break down in there, so the idea that there is such a thing as a singularity in nature is unlikely. A lot of people think that if you have a proper theory of gravity that works smaller than the beach ball metaphor then you don't have these issues, but it's not known.

JF: Another misunderstanding, which stems from that question, is the idea that the universe was small at the big bang. What was small at the time of the big bang was the entire visible universe, so everything we can see now, which is about 14bn light years away, all of that was compressed to the size of a pinhead. But it was one pinhead in an infinite space, so there's an infinite amount of stuff, as far as we can tell, outside our universe. So it's right to say that it's 14bn years old, but it's wrong to say that it's 14bn light years in size because it's probably infinitely big.

However, the question that's probably been asked is what happened before the beginning and the answer to that is that nobody has a clue – so that's the honest answer.

If there exists some particle that can travel faster than light, then surely there should be a way of sending information into the past?

jamma88 via web

BC: Yes, that's true. If you don't modify Einstein's theory of relativity and you take it at face value and send something faster than light, then yes, you can send messages into the past. So, if the current result is shown to be correct, then probably what you're saying is that you want a new theory of space and time, and then, who knows?

JF: In a nutshell, if Einstein is right, then yes is the answer to the question. But you'd be very hard pressed to find a physicist who thought that Einstein is right if you find a particle travelling faster than the speed of light. What that means is that Einstein is wrong because you can't travel back into the past and so there's some new theory that comes into play, which protects the law of cause and effect. It's very hard to conceive of a logical universe in which cause and effect doesn't hold.

What does no Higgs mean for physics? What are the other theories?

Jason Mickler via email

JF: No Higgs would be very exciting.

BC: It could be more exciting than finding it. The favoured candidate for the something new that we know must exist at the Large Hadron Collider is the Higgs, but it could be something else.

We've written several papers together and our most cited one is what would happen if there isn't a Higgs particle at the Large Hadron Collider and how we might explore the physics that must be there if there isn't one. It's very rare that you get to build an experiment in science where you're guaranteed to discover something new. The Large Hadron Collider is such an experiment, in that the standard model of particle physics predicts that there's going to be a Higgs particle. But it's not necessarily going to be there and if you take away the Higgs particle out of our standard theory, you take away all the maths and throw it in the bin and see what's left… and what's left is a theory that doesn't make sense.

JF: Something will show up sooner rather than later. If the Higgs particle is relatively light, there's a range of masses we expect it to have and we should see it very soon, we could even see it before Christmas. If it's heavy or if the alternative to it is heavy, then it could take a few more years before we find it. We're closing in on it fast now though – the machine is working absolutely wonderfully, it really is.

How do you feel about scientists who blog their research rather than waiting to publish their final results?

Stephen Marks via email

BC: The peer review process works and I'm an enormous supporter of it. If you try to circumvent the process, that's a recipe for disaster. Often, it's based on a suspicion of the scientific community and the scientific method. They often see themselves as the hero outside of science, cutting through the jungle of bureaucracy. That's nonsense: science is a very open pursuit, but peer review is there to ensure some kind of minimal standard of professionalism.

JF: I think it's unfair for people to blog. People have overstepped the mark and leaked results, and that's just not fair on their collaborators who are working to get the result into a publishable form.

Scientists use supernova explosions to measure how far away supernovas are. The distance depends on how bright they appear against how bright they really are. How do scientists know how bright the supernova explosions should be?

Bas Bouma via email

JF: When stars explode in a particular way (called Type Ia supernovae) they do so in a remarkably consistent manner – that is to say one such explosion looks pretty much the same as any other. That means that if we can measure the distance to a "nearby" supernova using some other method (and not its brightness) then we can use that to calibrate things and determine the distance to more distant supernovae using only their brightness. Incidentally, these supernovae are remarkable events. White dwarf stars are small dead stars and they survive purely as a consequence of quantum mechanics but only if they weigh less than 1.4 times the mass of the Sun. If this thing accretes matter and sneaks past the magic 1.4 solar masses then the electrons within the star start to move close to the speed of light and that triggers a catastrophic collapse – the supernova.

If question-asking is so fundamental to science, why has there been no research into how we might improve question-asking for learners in our places of education?

Laurence Smith via email

BC: I think, for example, quantum mechanics should be taught in schools for this reason. One of the reasons is that it's a great way of seeing how the data from experiments can drive you to a rather counterintuitive picture of the world. For example, the rules of quantum physics are not by themselves complicated, but they are philosophically challenging. I think the scientific method is more important to teach than facts. I'm not that bothered if people know about the structure of the atom or whatever but I want people to understand how you get to these conclusions about the world.

Mathematics

My question is: I cannot perceive or understand infinity. For man, everything has a beginning and an end. Answer, please!

Harry, via web

JF: The reality is that we don't know for certain what's outside the 14 billion years' worth of what we can see, so there could be an edge to the universe, it's possible, but there's no evidence in any of the data.

BC: The universe was opaque about 380,000 years after the big bang and at that point became diffuse enough that light could travel through it. And we can see that light, people measure it in great detail, and you could see if the universe had an edge in that data, but there's no sign of it.

The physics behind the current understanding of the universe isn't complete, but do you think that a new kind of mathematics will be needed, and what kind of mathematics might that be?

John Read, via email

JF: There isn't a Nobel prize for mathematics, its equivalent is called the Fields Medal and people who are working on fundamental questions in physics, string theory in particular, have won that prize in recent times, so it already is the case that physicists are breaking new ground within mathematics. People are trying to understand the universe at its birth – the behaviour of phenomena down to mind-bogglingly small scales – we're talking like 10-40cm. So new mathematics may well be needed and people are inventing new mathematics.

But it should be stressed that the known physics, the physics that we've measured in experiments, none of that really has mandated in any particularly significant way our theories of mathematics. There are exceptions, such as the idea that numbers have the property of commutativity, which means that 2x3 is equal to 3x2, but the theory of elementary particles used, for example, at the Large Hadron Collider utilises a mathematics where in the product of two numbers the order matters, so X times Y doesn't equal Y times X.

Astronomy

How do we know what shape the Milky Way is? I've seen many illustrations of our galaxy as a spiral, but how can we tell what it looks like when we're deeply embedded inside it?

Chris Muggleton, via email

JF: If you lived in an omelette, and you lived on the edge of that omelette, you could measure the distance between all the pieces of mushroom in the omelette. If you were clever enough to work out how far it was to all the different parts of the omelette, you'd be able to reconstruct it. So it's all a question of measuring the distance between the stars. Because they don't move any significant distance in the time you're measuring them [relatively speaking], to get the shape of it, all you need to know is the distance.

How do you feel about amateur astronomers, in today's hi-tech society?

Duncan Jones, via email

JF: Years ago, amateurs played a big part in the understanding of the cosmos, with observations and the recording of events. Unfortunately, with the advent of modern technology, the role of the amateur has been left far behind.

BC: In things such as astronomy, there's always been a place for amateur observers because there's a lot of sky. Certainly in searching for things such as new comets, they do make a contribution.

In particle physics, it's impossible for amateurs to be involved in the data because there's too much infrastructure required. In theoretical physics, Jeff might want to comment, and in theory the amateur could make a contribution because you don't have to be an academic to submit to a academic journal. If the paper makes sense then it can be published.

JF: I get a lot of papers sent to me by amateur scientists. But they've usually not got the scientific background or the training to make a contribution in theoretical physics, so it's very hard unless you've got that training.

Politics and economics

How likely is it that we'll be able to harness fusion power before we run out of fossil fuels?

@craighitchings via Twitter

BC: If we were to invest in it properly, then I'd say very likely, because the technology has been proved. In fact, the most effective fusion reactor at the moment is still in Oxford, which is where it's been for more than 30 years – and it works.

The problem is that it's not a very good commercial option at the moment because no one's demonstrated that you can build a commercially viable reactor. That's why government money has always been needed – because it's a 20- to 30-year investment. That's not the way you do things in private companies but governments can certainly help; we're talking single-figure billions, not going to the moon. So in my view, the technology has been demonstrated and it's simply a question of working out how to build industrial-scale plants that can return profit.

The real problem is that you have to contain plasma that's at a very high temperature – dismembered gas, basically. So it's very difficult to model and there are real engineering challenges. We need to understand what happens to this plasma.

Is the €75bn spent on the Large Hadron Collider worth the investment?

Oliver Gerrard via email

BC: The UK spends about £70m a year on the LHC. We spend less in Britain each year on Cern than we do on peanuts, literally, so it's a very tiny amount of money. A lot of that money funds PhD students and a lot of it pays for academics in universities – the bulk of the money actually stays in Britain. So breaking it down, it costs very little.

The other thing to understand is that the LHC is often portrayed as the search for another esoteric particle and that's nonsense. It's been built to solve a specific problem in our understanding of three of the four forces of nature. And there are all sorts of theories about how that might work, the Higgs being one of them. To portray it as some kind of esoteric hunt for an elusive particle is nonsense: it's the mainline of physics, which has arguably created wealth beyond anyone's wildest dreams and will continue to do so.

Can science save the economy?

Andrea via email

Both: Yes!

BC: It's the foundation of the economy for a start, so it'll have to! Nothing else will save it. The modern world is based on science, so that's it – there is nothing else.

JF: Yes, I'd be that definitive. For example, a significant fraction of the global economy relies upon the existence of a transistor – the world has been revolutionised by fundamental research into quantum physics done 60 years ago and now there are billions of transistors inside very home computer. They are a key ingredient of the microchip.

BC: It's science and engineering, you've got to put them together. Science and engineering together are the economy. Earlier this month, George Osborne announced the funding for science projects, including £50m for research into graphene, a material that has the potential to revolutionise the 21st century. More powerful electronics, stronger aeroplanes… pretty much anything you can think of, graphene can improve.

We are one of the world's leading scientific nations and it's my view that we should aspire to be the best.

Actually, George Osborne and this government are beginning to show signs of believing that. I think a lot of credit goes to the science minister, David Willetts, for making his point over and over again. I think it's beginning to bear fruit and we're starting to invest even at this difficult time – in fact especially at this difficult time, as that's what you need to do.