Humans as Particles, Particles as Humans?

I was wondering if you took a group of atoms and a group of people and told them to move around a defined space would it be as hard to predict each person path through out that space as it would to predict the path of the atoms? With this in mind could you say that atoms are like a human being or anything capable of through? In this sense can and atom think?
- Sara Huggins (age 22)
Margate, Kent, UK

Hi Sara,

Your specific question is very difficult to answer, because once you get a huge number of particles, their interactions become very complicated, and even our best computers can't find their exact motions. Furthermore, we don't know how to predict how humans will move, since to do this we would either have to read their mind, or know the exact quantum state of their body.

However, your question raises two interesting concepts. 

1) To deal with huge collections of particles, physicists have developed the fields of thermodynamics and statistical physics, which allow us to calculate macroscopic properties (like temperature, pressure, energy) of a system without knowing everything about its parts. In your case, we might not know the motion of all the atoms, but we could predict, for example, how many atoms on average would be in the top half of their container each second.

Similarly, some physicists have applied these ideas to model human behavior. If you have enough humans that an individual's actions can be considered probabilistically, then you might be able to make a simple model which predicts some important results. I don't know much about this field, but if you are interested, you could start by checking out the work of Victor Yakovenko (http://www2.physics.umd.edu/~yakovenk/econophysics/). Earlier this year, I saw an interesting talk he gave on applying these laws of physics to economics.

2) You also asked whether atoms can be thought of as thinking. To the best of our knowledge, atoms are made of relatively simple constituents (like quarks and electrons), and certainly are not capable of anything as complicated as thinking.

Even if they can't think, atoms can be used to do calculations— IF we arrange them just right. Physicists are working to build the first quantum computers, which harness particles (like atoms or photons) to do specific calculations. For example, if you arrange the state of a system into a very specific state, let it evolve, and then look at where all the particles are at a later time, you might be able to extract some information. (This information is useful only if you are clever about your initial state, and the interactions which influence your system's evolution.) 

Of course an ordinary classical computer is also made out of the same sort of quantum particles, but not arranged in a way that relies on the weirder parts of quantum behavior.

So, even if atoms can't think, they certainly can store information, and interactions can change the information they contain.

Hope that makes sense,

David Schmid

(published on 10/26/2013)