Why are there no 4D glasses?

My dad took me to see Star Trek- Into Darkness on Saturday. My mom only likes old movies with Romans in sandals or newer ones with Sean Connery in them, so we left her at home for this one. My dad's more into Star Wars than into Star Trek. But that's OK. Maybe it's because he always looks a little like Chewbacca if he doesn't shave for a while.

The film was in 3D and we had to buy a new pair of 3D glasses with our tickets (check out the Guardian's archive for an early review of its 3D quality here). I don't like 3D that much because it's always a bit darker and it feels like watching something through an aquarium. I have to wear glasses (because my parents don't trust me with contacts), so I have to wear my normal glasses under the 3D ones. And wearing two pairs of glasses for two hours makes my nose hurt.

Anyway. The film was alright, I thought. I liked Spock and Khan the most. My favourite scene was when Khan single-handedly took out a whole bunch of Klingons on Kronos. But I kept wondering why we had to watch it in 3D. I mean, there should really be a 2D alternative. Or a 4D one.

When we got home, I did a little research. I wanted to know how 3D glasses worked and if there was any way round them in a 3D film. I also wanted to know if 4D was an option for the next Star Trek film. This is what I found:

3D movies are projected onto the big screen twice, so what you see is actually two different sets of film. The glasses they give you then separate the pictures so that each eye only gets one picture each. (This is done by polarized films in the glasses. The two films are projected in a 45 and in a 135 degree angle. You can find out more about angles and on polarized films on mentalfloss.com here.) In the old days, cinemas used two different projectors to get the two pictures on screen. Nowadays, only one projector is used. The new projectors now use a system called RealD, which separates light rays in spirals. But the 3D effect itself has been around since 1936.

Check out RealD's website for a bit more information on those new projectors.

There are many different kinds of 3D glasses, but not all of them are used in the cinema. When you go to see a film in the cinema, you usually get a standard polarized set of glasses. (At home, people normally use red/green ones. You can find out more about the different kinds of glasses on this website). Normal polarized glasses work with something called 'stereoscopy'. They separate light rays so that only a few waves can reach each eye. This is then what creates the 3D effect because your brain reconstructs the depth and the distance of what you see with something called binocular vision. Binocular vision is pretty cool because it lets you figure out distance. It's what helps you catch stuff that is thrown at you. Or that makes you get hit in the face a lot if other people keep throwing stuff at you when you're not wearing your normal glasses.

So it turns out that - if a film is advertised in 3D - they can't just let you watch it in 2D because there's two images that are being projected on the screen. They also can't give you 4D glasses because the fourth dimension is time and we can't really see time.

Physicists use it for a lot of their calculations though. In our three dimensions, any given point can be localized by three coordinates, x, y, z. The fourth dimension gives it another coordinate named w. A square in 4D is called 'Tesseract' and looks like this:

There are quite a few crazy people in Physics and some of them work with up to ten dimensions. A lot of this has to do with something called 'string theory'. But I have no idea what string theory is about. And it's got nothing to do with 3D glasses, that's for sure. So if you want to know more about it, I suggest you ask your physics teacher.

I took the Tesseract image from Wikipedia. The Star Trek one came from www.totalfilm.com, the Chewbacca one from blancmaninc.com.