Today I gave a presentation on matter for the American Studies colloquim. It is currently focused on material culture. Below is the text of the handout I put together for class. Since some of my Facebook friends asked for it I thought I’d just go-ahead and make it publicy available. I’ll try to put up a .pdf version tomorrow.
Some Thoughts on Matter
1. Matter is weird and complicated. It can behave in counter-intuitive ways. What physics gives us is different models for understanding matter. These models help us predict how it will behave in different circumstances. Remember: a model of the universe is not the same thing as the universe. Also, as evidenced by the search for dark energy and dark matter, there is still an awful lot that we don’t understand (together they make up 95% of the observable universe).
2. How physics models the behavior of matter depends on speed, scale and frame of reference. There are three overlapping models: Newtonian Mechanics, Quantum Mechanics and Relativity.
3. Two things to remember before turning to these models:
A. e = mc^2 or mass and energy are different forms of the same thing;
B. The First Law of Thermodynamics says that the total amount of energy (and therefore mass) in a closed system must be conserved;
4. Newtonian Mechanics:
A. Describes the world that we can see with the naked eye: largish objects (i.e. larger than a molecule) moving at slow speeds (i.e. significantly less than the speed of light).
B. Essentially deterministic: I can write an equation predicting where a ball I throw will land.
5. Quantum Mechanics (i.e. the Standard Model and whatever comes after it):
A. Describes the world that we can’t see with the naked eye: atomic and subatomic particles.
B. Counter-intuitive and essentially probabilistic: I can write an equation predicting the probability of a particle arriving at a particular place. (Einstein said: “God does not play dice.”)
C. Is predicated on the idea that particles have fixed values or quanta associated with them (i.e. an electron has a charge of -1).
D. At this scale matter has a dual particle wave nature (an electron behaves like both a particle and a wave form).
E. Places limits on knowledge (i.e. Heisenberg’s uncertainty principle: we can only know so much about the position and momentum of a particle. The more we know about one, the less we know about the other).
F. Matter itself is made up two families of particles: fundamental particles (fermions) and radiation or force carrying particles (bosons). Asif Hassan, a physicist at University of Texas at Austin, says: “no two fundamental particles (electrons, neutrinos, quarks) can be at the same place with the same properties. The other kind of particle is bosonic (commuting), so that this kind of particle (photons, W and Z particles, gluons, and the Higgs) can be at the same place with the same properties. So photons for instance can constructively interfere at the fundamental level and lots of them can be in the same quantum state at the same time – this is what is arranged to happen in a laser. There is no such thing as a neutrino laser, or an electron laser for example. So with bosons you can see the quantum behavior at an energy and size scale that we consider normal, but with fermions the quantum behavior mostly shows up at tiny scales. You have to be careful though about the idea of material things corresponding to fermions… because we usually think of those things as things we can touch, and neutrinos are fermions but they are so weakly interacting that we don’t even notice them. Intuitively we associate “stuff” with things we can touch, and most of that is fermions – electrons and quarks (which make neutrons and protons.)”
G. There are lots of amazing phenomena observed at the quantum level that we don’t have time to go into: entanglement, quantum tunneling, virtual particles…
H. Satisfactorily accounts for three of the four fundamental forces: electromagnetic, and the weak and strong nuclear forces.
6. Relativity:
A. General relativity accounts for gravity and how mass and energy distort space.
B. Special relativity says:
1. There is no universal frame of reference;
2. The laws of physics are the same for all frames of reference;
3. The experience of time depends upon the frame of reference.
C. Relativity is useful for understanding things that are either very large or are moving very fast. That doesn’t mean it can’t show up in our everyday life. Asif Hassan says, “the gravitational field of the earth changes the speed of clocks, so GPS satellite clocks run at a different rate than they do here on Earth. GPS has to account for this correction to work properly. Most of us don’t realize it but we are carrying around an application of general relativity in our pockets.”
Suggested Resources
Scientific American (www.scientificamerican.com)
Albert Einstein, Relativity: The Special and General Theory
Richard P. Feynman, QED: The Strange Theory of Light and Matter
Stephen Hawking, A Brief History of Time
Stephen Hawking, Black Holes and Baby Universes
Brian Greene, The Fabric of the Cosmos
Leon Lederman, If the Universe is the Answer: What is the Question?
Acknowledgement
Asif Hassan commented on a draft of this handout.
