Cosmic Horizons

Everyone loves black holes. Immense gravity, a one-way space-time membrane, the possibility of links to other universes. All lovely stuff. A little trawl of the internets reveals an awful lot of web pages discussing black holes, and discussions about spaghettification, firewalls, lost information, and many other things. Actually, a lot of the stuff out there on the web is nonsense, hand-waving, partly informed guesswork. And one of the questions that gets asked is "What would you see looking out into the universe?" Some (incorrectly) say that you would never cross the event horizon, a significant mis-understanding of the coordinates of relativity. Other (incorrectly) conclude from this that you actually see the entire future history of the universe play out in front of your eyes. What we have to remember, of course, is that relativity is a mathematical theory, and instead of hand waving, we can use mathematics to work out what we will see. And that's what I did. ...

So, my plans for my blog through 2017 have not quite gone to plan, but things have been horrendously busy, and it seems like the rest of the year is likely to continue this way. But I did get a chance to do some recreational mathematics, spurred on my a story in the news. It's to do with a problem presented at the  2017 Raytheon MATHCOUNTS® National Competition  and reported in the  New York Times.  Here's the question as presented in the press: Kudos to 13 year old Texan, Luke Robitialle, who got this right. With a little thought, you should be able to realise that the answer is 25. For any particular chick, there are four potential out comes, each with equal probability. Either the chick is pecked from the left pecked from the right pecked from left and right not pecked at all Only one of these options results in the chick being unpecked, and so the expected number of chicks unpecked in a circle of 100 is one quarter of this number, or 25. AB...

There was a movie, in the old days, Journey to the Far-Side of the Sun  (also known as Doppleganger) which (spoiler alert) posits that there is a mirror version of the Earth hidden on the other side of the Sun, sharing the orbit with our Earth. The idea is that this planet would always be hidden behind the Sun, and so we would not know it there there. This idea comes up a lot, over and over again. In fact, it came up again last week on twitter. But there's a problem. It assumes the Earth is on a circular orbit. I won't go into the details here, but one of the greatest insights in astronomy was the discovery of Kepler's laws of planetary motion , telling us that planets move on elliptical orbits. With this, there was the realisation that planets can't move at uniform speeds, but travel quickly when closer to the Sun, while slowing down as their orbits carry them to larger distance.  There has been a lot of work examining orbits in the Solar System, and you can  s...

A long time ago, I wrote a post about the  Physics of Rendezvous with Rama , a science fiction story by  Arthur C. Clarke  set on an immense alien spaceship. The spaceship rotates, providing the occupants with  artificial gravity , a staple of science fiction. I mentioned in the article that I am not an immense fan of a lot of science fiction, as much of it relies on simple "magic", but Clarke knew his physics and so he knew that the "gravity" experienced in the rotating ship will differ to that on Earth, and previously I wrote about what happens if you jump off a cliff. In the last week, there was a question on twitter (it's an internet thing) about the movie  Elysium  which has a spectacular rotating spacecraft with the Earth's rich abroad. While it's a shame that the plot was not as spectacular, the question was how can such a station keep it's atmosphere. This is an interesting question, as you might think that it would all simply zip off...

Wow. It's been a while since I have written a blog post. Much of this is because of work and travels, and book writing (more news on that in the near future). But I'd like to get into blog writing, so here's a little science musing. Is an elephant heavier than a mouse? Now, you are probably saying "well, of course". Surely event the heaviest mouse weighs less than the newest born baby elephant, so why am I asking such a stupid question. Well, because science can never really  prove that an elephant is heavier than a mouse. I know, I've gone and put that word in, and I've written about how  proof has no place in science.  But let's examine this in a little more detail. I've stressed many times before that while measurements are important in science, without an uncertainty  such measurements are useless. And while professional scientists pour over papers focused on the error bars in figures, errors and uncertainties are typically waived ov...

Still struggling with grant writing season, so another post which has resulted in my random musings about the Universe (which actually happens quite a lot). In second semester, I am teaching  electricity and magnetism to our First Year Advanced Class . I really enjoy teaching this class as the kids are on the ball and can ask some deep and meaningful questions. But the course is not ideal. Why? Because we teach from a textbook and the problem is that virtually all modern text books are almost the same. Science is trotted out in an almost historical progression. But it does not have to be taught that way. In fact, it would be great if we could start with  Hamiltonian and Lagrangian  approaches, and derive physics from a top down approach. We're told that it's mathematically too challenging, but it really isn't. In fact, I would start with a book like  The Theoretical Minimum , not some multicoloured compendium of physics. We have to work with what we have! ...

I need to take a breather from grant writing, which is consuming almost every waking hour in between all of the other things that I still need to do. So see this post as a cathartic exercise. What makes a scientist? Is it the qualification? What you do day-to-day? The association and societies to which you belong? I think a unique definition may be impossible as there is a continuum of properties of scientists. This makes it a little tricky for the lay-person to identify "real science" from "fringe science" (but, in all honesty, the distinction between these two is often not particularly clear cut). One thing that science (and many other fields) do is have meetings, conferences and workshops to discuss their latest results. Some people seem to spend their lives flitting between exotic locations essentially presenting the same talk to almost the same audience, but all scientists probably attend a conference or two per year. In one of my own fields, namely cosm...