John Lindal’s Blog

Disaster Movies

Two weekends ago, I was laid low by the stomach flu, and it was my misfortune that they were showing The Core and Armageddon on TV that weekend. It’s been bugging me ever since, so I’d better just blog about it and get it out of my system.

Armageddon is by far the better of the two. Despite the wildly fluctuating value of G on the asteroid, the crazy surface topography (for an object that has presumably been knocking around in the asteroid belt for eons), and the never-before-seen metal that eats drillbits for breakfast, Armageddon at least has heart. Bruce Willis’ character does the right thing by insisting that he, rather than the guy who will marry his daughter, should sacrifice his life.

The Core sets a new, abysmal low for disaster movies. Even the writers couldn’t come up with a reason why the Earth’s core would stop generating a magnetic field, and they admitted as much in the movie. Their idea that it was the spinning of the core that generates the Earth’s magnetic field (“Moving metal generates a magnetic field. Physics 101.”) is flat wrong — moving charges generate magnetic fields, not moving metal — and Earth’s field would not last a week if all the currents truly stopped. The giant spark plug that they built as a backup system was equally idiotic — there is no relationship between restarting a heart with a defibrillator and restarting the currents in Earth’s core with an EMP. The idea that a nuclear explosion would restart the spin of the core was also wrong — pressure waves do not move mass, they only wiggle it — just like waves in the middle of the ocean. The shielding on their ship violates the basic laws of thermodynamics — nothing can stay cold when immersed in a hot environment, unless it has a huge reservoir of something cold into which to dump the incoming heat. Their depiction of Earth’s mantle was ridiculous — molten rock is not transparent and solid quartz crystals cannot exist at those temperatures.

Sigh. Makes me yearn for a Liz Taylor disaster movie…

Light bulbs

I woke up this morning wondering about light bulbs. Your standard incandescent bulb will fall over if you place it rounded side down, unless you balance it perfectly, so this is an unstable equilibrium. Your standard floodlight will not fall over, however, so this is a stable equilibrium. What makes one unstable while the other is stable? Where is the crossover point? Can we make it a neutral equilibrium, i.e., it will stay in whatever position we place it? Click here for the answers.

A Wearable Computer

The idea of a wearable computer is not new, but a tiny cell phone has many advantages over a piece of clothing, so I’m not expecting a computer to migrate from my phone to my underwear any time soon.

However, in some situations, a computer that is built into a jacket could be helpful, e.g., if the jacket is part of your work uniform. So here are my thoughts on how it might work…

If a cell phone can contain a computer, then so can a jacket collar. This distributes the weight across the shoulders and puts it in an area that we instictively protect, namely the neck.

The CPU communicates with all peripherals, e.g., the earpiece or a DVD drive, via short-range wireless, e.g., Bluetooth. The CPU communicates with the Internet via a standard cell phone channel. One cool idea would be to have a third channel similar to that provided by a wireless router, i.e., medium range, and use this for peer-to-peer communication, e.g., within a warehouse or to your friend sitting close by. By using an ssl tunnel and only allowing connections from people on a Friends list, this ought to provide a much higher bandwidth connection than that obtainable via a cell phone. The obvious extension is to a full ad-hoc network.

The best input mechanism that I can think of is the flexible computer screens currently under development. These can be rolled up like paper, but provide a 2D array of pixels for displaying images. The display could be stored rolled up around either forearm, with a spring mechanism similar to what is used for keychains. In order to keep the sleeve flexible, only the 120° covering the outer side of the forearm would be rigid. This is the area most in need of protection. The inner forearm, which we naturally protect, would be where the screen would unfold from. Since a handle would be needed to make it easy to pull the screen out, this handle could also contain a set of controls and a stylus could be stored inside the handle, along its axis. The controls would be used for whatever actions need to have shortcuts (additional controls could be placed on the collar), while the stylus would be used to interact with the display when it is pulled out. Communication with the CPU would obviously be via the short-range wireless channel.

By making the screen attach to the spring mechanism via a strip magnet, it would be easy to detach and reattach the screen, thereby allowing the screen to be placed on a table when convenient. When a table is not available, bracing could fold out from the screen’s handle and attach to the corners of the slot from which the screen emerges. This would provide at least some rigidity while using the stylus with the primary support coming from the arm, of course. For this to work, the stylus would have to have a special tip that would interact with the screen without requiring a lot of pressure.

With a special card that could plug into a laptop and communicate with the worn computer via short-range wireless, one could achieve a remote desktop solution, thereby reducing the need for the flexible screen when a normal computer is available.