Cosmic Horizons

There has been some noise out there in the matrix about a recent book by  Lawrence Krauss  called "A Universe from Nothing". It has been seized upon by by the atheist community (and to lay my cards on the table, I am an atheist) as another nail in the coffin for the  God Delusion . It has gone so far that  Richard Dawkins  (husband of the wonderful  Lalla Ward , one of the Doctor's greatest companions) has said in the forward "This could potentially be the most important scientific book with implications for supernaturalism since Darwin." and “Even the last remaining trump card of the theologian, ‘Why is there something rather than nothing?,’ shrivels up before your eyes as you read these pages. If ‘On the Origin of Species’ was biology’s deadliest blow to super­naturalism, we may come to see ‘A Universe From Nothing’ as the equivalent from cosmology. The title means exactly what it says. And what it says is ­devastating.” I haven't read the bo...

For someone who works in relativity, you'd think I'd know where the time goes! Things have been quite busy with grants, Easter and packing up my office as the building I am in is to be demolished. We're going to be off campus for a couple of years, in the lovely suburb of  Redfern ; at least we'll be closer to the  train station :) This has meant I've not had a lot of time to get a lot of research done, so I thought I would post a little lesson on relativity, namely what happens when you fall into a black hole. Not the painful bit where you get torn limb from limb, but what you see. I've worked on this in the past, but this post was sparked by  this article , especially this statement. "First of all, you  approach the speed of light  as you fall into the black hole. So the faster you  move through space, the slower you move through time," he said. "Furthermore, as you fall, there are things that have been falling in front of you that have...

When I was an undergraduate student, I had thought about becoming a particle physicist, but a summer school first at the Rutherford Labs (working on proton-anti-proton scattering) and then CERN (search for charged Higgs particles) beat that out of me :) There is a lot of chatter about the Higgs out there at the moment, but unfortunately I think that a lot of it illustrated the poor understanding of statistics by journalists (and even scientists). p-values make me weep. But I thought I would talk about something else, the the discovery of bottomium at the LHC. Funnily enough, it's not actually a new particle, and that's something I thought I would try and explain. Let's start with a picture - what's this? Of course, it's an atom. Well, except we know this is just a schematic picture of an atom, a nucleus with some electrons whizzing around. A real atom is more complex than this, being described by the laws of quantum mechanics. Electrons are not little ...

The German tank problem is a fav of mine. The wikipedia page on it is a little long winded, but I think it can be looked at a lot faster with a little numerical mucking about. The problem is quite simple. The enemy are producing tanks, and each has a sequential serial number (for simplicity, let's assume that the numbers are reset every month). You encounter this scene on the battle field; and we see that this is tank number, say, 15 of a particular months production. How many tanks were produced in that month? Can we even answer the question? This is the problem that faced the Allies in WWII; you really wanted to know how many panzers are out there. Intelligence officers were reporting productions of more than a 1000 tanks per month, but based on statistics, the predicted number was significantly fewer than that, in the hundreds. After the war, the numbers were checked against records and the statistical answer was amazingly correct (read the wikipedia page for more detail...

I've been interested in chaos since reading Gleick's book back in the 1980s. I was first introduced to fractals when I was a summer student at the Rutherford Labs in the late 1980s; this was when colour printers were rare and expensive and I spent a lot of time convincing the guardian of the printer that printing out large colour fractals for my bedroom wall was essential for my studies of proton-anti-proton scattering. But that's another story. A little while ago, I caught an excellent documentary called "The Secret Life of Chaos" by the equally excellent presenter, Jim Al-Khalili . This linked a lot of topics, including chaos and complex systems , which is when a group of things following simple rules results in complicated (and sometimes difficult to predict) behaviour. One of the key things I learnt was the importance of this man in some of the earliest work in the field. I'm sure a number of you recognise him as Alan Turing . I first came across...

With exam marking and committee meetings, it has been a slow week, but here's a pop quiz. What does this woman have to do with this video? (the video has a nasty crack at the end of it, and so don't watch if squeamish). The answer is not that the woman in the photograph is the girl in the video. Of course, what we are looking at here is a collision, and due to the use of the yoga balls, it is a pretty elastic collision, and so energy is almost conserved (and if you account for the energy that goes into heat and noise, it's completely conserved). But what we all remember from our high school physics is that the thing called momentum, the sum of mass times velocity, is always conserved in collisions, and so if, before the collision, we take the mass of the boy and multiply it by his velocity, and then do the same for the girl, and then add the two quantities together, this sum is the total momentum. If we do the same after the collision (assuming no external...

I understand a lot of people were moved by the death of Steve Jobs , but IMHO a gianter (if that's a word) person of the computer world also died last week. Sadly, Dennis Ritchie died on the 12th October. While Steve gave us shiny toys (and yes, I am typing this on a MacBook, and I have an iPad), Ritchie gave us (well, me) some of the vital tools of the trade. With Ken Thompson , he developed the best operating system in the world, namely Yes, UNIX . When I started my PhD, we used VMS on VAXes, but these were superseded by these beauties - Sun machines running SunOS , my first experience of UNIX. Soon after, we had the birth of penguin, and we could have real computing in the home with Linux. In the old days, we were spending a fortune on maintenance contracts for Vaxes and Sun machines, so the prospect of running a free proper operating system on cheap hardware was very appealing (and no, windows of any variety is not a proper operating system - good for games, but n...

After a weekend of great rugby (from the Welsh, the English and Australians were rather blah), I have responded to a good question posted over at The Conversation on distances in the Universe. It's a question that gets raised quite a bit and basically put it goes something like If the Universe began 13.7 billion years ago, when the distance between any pair of points was zero, how can anything be more than 13.7 billion light years away? The answer is the difference between local motions and global motions. Here's the response I posted An excellent question, and one which may not make sense to start with. We know from special relativity, nothing can travel faster than light (recent neutrino claims excepted). But in reality, special relativity says that nothing can go faster than the speed of light **locally**, so in a small box, if I try and race an electron and a photon across the box, the photon will win. With the expanding universe, the question we are a...

A quick post today, as I am running behind on a couple of things, but I have had a book review published in The Conversation . The book is The Fallacy of Fine-Tuning: Why the Universe Is Not Designed for Us by Victor Stenger, and is on a topic I have thought a lot about over the year, but never published on, namely "why are we here, in this Universe"? For those of a religious inclination, the answer is apparently obvious, the Universe was fine tuned to be habitable. For those grounded in a more scientific approach to understanding the Universe, the answer is not so clear and straight forward. If we start to play around with the fundamental physical parameters, such as the strength of forces etc, it appears we end up with mainly dead Universes. Heck, even messing with the content of the universe, in terms of the amount of matter, ends up with universes that collapse too quickly, or expand so fast that stars (and hence people) cannot form.  I think it is safe to say th...

I have a cosmological post brewing, so I thought I would touch on a slightly different topic, namely the question of "could physics predict a giraffe?" The following has the usual "buyer beware" clauses; I am a physicist, an astrophysicist at that, and not a chemist, or a biologist, and definitely no a philosopher of science, although I may end up annoying all of them. To start with, let's look at the subject, to wit, a giraffe. The reason for the post is because of an article over at The Curious Wavefunction titled Why biology (and chemistry) is not physics. The basic argument is this; Physics is a fundamental science, and identified the basic workings of the Universe. How do nuclei hold themselves together, how does the Universe expand, why do electrons flow through conductors etc etc. That's physics. Now, physics is "reductionist", in that all complex processes can be broken down into a the application of relatively simple underlying phy...

A busy weekend, so here is some weekend thoughts (and associated reading) for you. It's all to do with relativity and are linked with some blog posts. Time does not flow : To paraphrase Shakespeare, All the world is a 4D manifold, and all its players are but worldlines. Basically, General Relativity tells us that the Universe is a 4D canvas and our paths are traced out. It's all there, past, present and future (from any individual's perspective). The Universe does not unfold as we progress into the future. It's all already written out (like a path on a map). Enter the philosophers and discussions on freewill, but taking relativity at face-value, there isn't any. Heck, it doesn't even tell us which direction our experience of time flows in, we set that with a decision on dt/dτ. Energy is not conserved : In general, energy is not conserved in General Relativity. This one usually freaks out the students, but it caused Einstein a whole host of headaches as well....

It's Friday, it's pouring with rain, and time for a grumpy post. The BBC is running a story Has physics become cool again? . While the overall story is good news, that the number of people people doing A-Level physics in the UK is on the way up, it also high-lights what I see as a big problem, basically the media's portrayal of physicists. Words like "nerd" and "geek" to generically describe scientists makes my blood boil, as does their portrayal as socially inadequate, Star Trek obsessed, comic-book reading dweebs. Case in point: Apparently "smart is the new sexy". And our own Beauty and the Geek had this  bunch Not to mention Nerds FC . In fact, each year we get an email circulating around our physics department that Beauty and the Geek are looking for new contestants, but from physics they are only looking for geeks, not beauties. Harmless fun you may say. But is it? We moan about falling numbers in science, and in physics, the n...