Motus Mentis

On February 15th, the asteroid 2012 DA14 will be passing by at the rather intimate distance of 21,500 miles. That’s mighty close: it’s actually within the Clarke orbit used by geosynchronous communication satellites, which circle the planet 22,300 miles up.

It definitely will not hit us, say the boffins, and when it comes to this sort of celestial-mechanics stuff I’m inclined to trust them. (After all, we aren’t talking about climate forecasts here, or Ivy-League economic scapulomancy.)

If you are interested in this sort of thing, you may already know that there are two systems commonly used to assign collision-hazard values to “near-Earth objects”: the “Torino” scale, and the more complex “Palermo” scale. (In case you’re wondering about those names: the Torino scale got its name after it was introduced at a conference there, and the Palermo scale, which came along later, simply carried on the tradition of naming asteroid-hazard scales after populous Italian tourist destinations.) For vastly more information about the Palermo scale, have a look here.

This particular boulder, which is about 150 feet across and weighs something in the order of 130,000 metric tons — that is, roughly equal in size and mass to film-maker Michael Moore — would strike the Earth with an impact equal to a 2.4 megaton bomb. That’s actually pretty paltry compared to some of our more impressive thermonuclear ordnance, and anyway, it’s going to miss us. DA14 has been assigned a zero on the Torino scale, and gets a wimpy Palermo score of -3.19.

So, nothing to worry about, folks, at least this time around. But my sources tell me that there are more than a million of these smallish NEO’s whizzing around, and we only learned about this one just a few months ago. So keep an ear to the ground, or whatever.

From a fascinating interview with physicist David Deutsch:

There’s a notorious problem with defining information within physics, namely that on the one hand information is purely abstract, and the original theory of computation as developed by Alan Turing and others regarded computers and the information they manipulate purely abstractly as mathematical objects. Many mathematicians to this day don’t realize that information is physical and that there is no such thing as an abstract computer. Only a physical object can compute things.

On the other hand, physicists have always known that in order to do the work that the theory of information does within physics, such as informing the theory of statistical mechanics, and thereby, thermodynamics (the second law of thermodynamics), information has to be a physical quantity. And yet, information is independent of the physical object that it resides in.

I’m speaking to you now: Information starts as some kind of electrochemical signals in my brain, and then it gets converted into other signals in my nerves and then into sound waves and then into the vibrations of a microphone, mechanical vibrations, then into electricity and so on, and presumably will eventually go on the Internet. This something has been instantiated in radically different physical objects that obey different laws of physics. Yet in order to describe this process you have to refer to the thing that has remained unchanged throughout the process, which is only the information rather than any obviously physical thing like energy or momentum.

The way to get this substrate independence of information is to refer it to a level of physics that is below and more fundamental than things like laws of motion, that we have been used thinking of as near the lowest, most fundamental level of physics. Constructor theory is that deeper level of physics, physical laws and physical systems, more fundamental than the existing prevailing conception of what physics is (namely particles and waves and space and time and an initial state and laws of motion that describe the evolution of that initial state).What led to this hope for this new kind of foundation for the laws of physics was really the quantum theory of computation. I had thought for a while that the quantum theory of computation is the whole of physics. The reason why it seemed reasonable to think that was that a universal quantum computer can simulate any other finite physical object with arbitrary accuracy, and that means that the set of all possible motions, which is computations, of a universal computer, corresponds to the set of all possible motions of anything. There is a certain sense in which studying the universal quantum computer is the same thing as studying every other physical object. It contains all possible motions of all possible physical objects within its own possible diversity.

Read the rest (with video) here.

If you’re like me, you’ve been asking yourself lately: when did people first make cheese?

Here’s your answer.

Here’s a website that will appeal, I think, to at least a few of our readers, for various reasons: Retraction Watch.