[insert witty title]

Earlier this evening I was feeling a bit guilty and catching up with a bit of reading at arXiv. For those of you who aren’t familiar with arXiv, wikipedia comes to the rescue:

arXiv is an archive for electronic preprints of scientific papers in the fields of physics, mathematics, computer science and quantitative biology which can be accessed via the Internet. In many fields of mathematics and physics, almost all scientific papers are placed on the arXiv. As of June 2007, arXiv.org contains over 423,000 e-prints, with roughly four thousand new e-prints added every month.

arXiv is broken down by subject area, and I usually confine my reading to astro-ph, where pretty much every single scientific paper in astronomy is released, for free, to the community. Today, for some reason I took a look through the category list and found physics.pop-ph, the repository of articles about popular physics. One title in particular stood out, and I couldn’t resist having a read:

Hollywood Blockbusters: Unlimited Fun but Limited Science Literacy

I’m really not sure what to make of the article, it is all very po faced and hyper-serious, but I just can’t help laughing at the indepth analysis given to some films. For example, there is a scene in The Core where the heroes go deep underground and get out of their vehicle.

We could discuss many questionable issues with this scene: (a) Could a cave exist at such depths? (b) Could the crew afford to open and close the door of the vehicle in such a depth? This would mean the loss of breathable air from the vehicle and changes in the air pressure and temperature of the vehicle. (c) Could the flexible suits that the crew is wearing really protect them at that depth? Many more questions could be added in this list. The reader can reflect on these issues on his own. We will only discuss the sinking of a human body in lava

I can’t even tell if the authors are being serious, or wrote this whole thing for a laugh in the pub. Don’t even get them started on why time would probably not go backwards when superman flew around the earth, or why in X-Men: The Last Stand the bit where Magneto moves the golden gate bridge is not feasable (unless Magneto is powered, like the sun, by fusion).

The relocation of the bridge gave to the director an opportunity for great special effects. However, even with the acceptance of Magneto’s special powers, it is an unrealistic scene given the physical laws in our universe

The whole paper is absolutely brilliant and I urge everybody to read it.

I really like the idea of doing some movie reviews focused entirely on movie physics, think Angry Nintendo Nerd but with graphs and equations and foul language.

Finally, as a single word of advice. If you’re ever in a situation where either of the authors of this paper ask you to watch a movie with them you should respectfully decline.

Recently the Guardian asked three writers, three scientists and two broadcasters to answer six basic scientific questions. Their results do seem to indicate that the writers and broadcasters aren’t exactly scientifically literate. Here are the six questions they asked, see how many you can get right:

Q: Why does salt dissolve in water?
Q: Roughly how old is the earth?
Q: What happens when you turn on a light?
Q: Is a clone the same as a twin?
Q: Why is the sky blue?
Q: What is the Second Law of Thermodynamics?

You can check you answers (and read other people’s) at the article Here.

I’m happy enough with my attempts (I didn’t quite get the saltwater question correct, but was very close. Also the clone/twin question was more of an educated guess than knowledge).

This is probably my favourite answer in the whole article, by Newsnight presenter Kirsty Wark on why the sky is blue:

Because it’s a reflection of the oceans on the planet. No idea apart from that. I think the sky is blue because… the rain clouds obscure the blue, and the blue is a reflection… because of the sunshine. Fuck! I don’t know! Why is the sky blue?

My mind has been blown today! I learnt about a NASA experiment called GRACE (Gravity Recovery and Climate Experiment). Grace is mapping the gravitational field of the Earth with an unprecedented level of detail.

The experiment operates with the use of two satellites. Each is on exactly the same orbital path but always on opposite sides of the Earth. When they are passing over a region where the gravitational field is strong they are pulled slightly closer together; when the field is weak they move apart. In this way the two satellites have been dancing around the earth, gradually building up a map of its gravity:

Red patches mark out where there is a lot of mass under the Earth’s surface. Grace is sensitive enough to show all sorts of crazy stuff and alongside all the obvious applications like making pretty maps of the earth’s gravitational field and testing relatavistic frame dragging it has:

• found that Antarctica’s ice mass had decreased by 36 cubic miles a year, helping prove that global warming and melting polar ice play a role in rising sea levels.
• discovered the 480 km (300 miles) wide Wilkes Land crater in Antarctica, which probably formed about 250 million years ago
• made maps of how the flooding of the amazon affects gravity!

Grace can supposedly even see ocean currents! On my list of satellites named after ladies it surely sits near the top

I’m sure most of us are familiar with Moore’s Law, the observation that the transistor density of circuits doubles every 24 months

One thing that I have always been a little curious about with Moore’s Law is exactly how long it can go on for, surely we can only etch on integrated circuits down to a certain size before further miniturisation becomes impossible. One clue for how Moore’s law can continue far into the future comes from this wonderful graph

in which Ray Kurzweil has expanded the standard Moore’s law plot back in time by considering all sorts of different technologies. As each technology is pushed to its limits a new one replaces it, allowing more growth. In this picture Moore’s law is actually the fifth in a series of exponential computer growth laws.

I have no idea how long computational power can continue to grow at its present rate using integrated circuits, or whether or not a sixth technology will be found that can replace them (see e.g. timeline of quantum computing). Perhaps we will never find another significant improvement, and be stuck with slightly improved versions of current technology forever.

As an interesting aside there was a paper on astro-ph sometime last year (here) about the theoretical maximum size of a computer, taking into account all of the information available in the Universe. Turns out that Moore’s Law can hold for an absolute maximum of 600 more years.

late edit: interesting note about quantum computing in the comments

Back in the 50s and 60s film makers decided that it might be pretty cool to start making 3D films. So they did- and everyone started to go the the movies and wear funky multi-coloured glasses and get freaked out by monsters jumping out at them. But, then, the film-makers stopped making 3D films. I guess it was because colour films were more popular than 3D films, and its pretty tricky to get Glorious Technicolor(R) when all your lines are surrounded by a red and blue haze. Or, it could be that you ended up looking like these freaks.

What a shame.

I imagine, 50 years ago, when TVs first started getting popular, that people thought that by 2006 we’d be immersed in spectacular triple dimesional virtual realities like the holodeck on StarTrek. Instead the best that the BBC (or Sky, for that matter) can do is offer us hundreds of David Dickinson in something called ‘High Definition’. I feel robbed.

So, what happened to our fantastic 3D experiences?? Well, I remember, in the 80’s and early 90s those huge helmets with 2 screens in them were pretty popular. But it turned out that, not only did they let immerse you in 3D-VR, they also had a tendency to immerse your feet in the last meal you ate.

But, wait, do not give up all hopes. Ladies and gentlemen, I bring you Integral Imaging, and this shit is clever (even Craig didn’t believe me on this one!).

The key to getting realistic 3D images is getting as many cues right as possible- basically, tricking the brain into thinking something is true. There’s a number of cues for 3D vision, but the main ones are:

• Size: This model cow is close by, that real one is far away. Nearby…Far away.
• Occlusion: If something is in front of another object, it tends to block it out.
• Perspective: Parallel lines meet at the horizon.
• Stereopsis: Our two eyes see 3D objects from slightly different angles.

Usually, our clever brain takes all this info, and constructs a 3D ‘map’ of the world around us.
Of course, TVs and movies use the top 3 cues very well. But on that last one, they are pretty weak. So, the trick is to get different images to the two eyes at the same time (hence the glasses and the headsets). This is what Integral Imaging (II) is good at.

II uses lots of lenses. Shine light from a distant object (so distant that the light waves are effectively parrallel) through a lens and you will get an image of that distant object on the focal plane of the lens. Conversely, put an image on the focal plane of a lens, and you will get parallel light rays coming out. When your eyes look at the light from the lens, that light will come from a single point of the image. Move your eye a little, and you will see light from a slightly different point of the same image. So, your two eyes, if open at the same time will see two very slightly different points of the original image. If you are really clever about how you make the original image (and these guys are) then you can send your two eyes exactly the right combination of light, that your brain will think that its coming from a 3D object.

Now, this is pretty crap if you only use 1 lens. But, if you use thousand upon thousands of lenses, you can effectively make up a whole ‘3D painting’ from these lens-image combinations. Even better, all you have to do is make the thousands of images moveable, and hey presto we’ve got 3D TV that doesn’t require fancy glasses or makes you feel sick.

Clearly, it would be great if I could show you the effect of II, but, with your crappy 2D screens, it just ain’t gunna work. I did see a movie once where the camera moved around the image giving the impression it was 3D, and that looked pretty cool, but google doesn’t want to find it for me again. So, sorry about that. I’m just looking forward to walking into Dixons one day and seeing a kick-ass 60″ 3D screen showing the latest release.

This is all kinds of awesome. I mean it. All. Kinds. Of. Awesome.

It is also nice to see science applied in a practical and useful way.