You haven't heard from me this last week, because I have been sick as the proverbial dog. I was felled by a virulent stomach virus which has been very common in my area, which I probably picked up at my crowded workplace. I struggled to get through three workdays, and then it got too bad for me to go to work. I will spare you gentle readers the details of this affliction, but I was not able to eat anything for two days, and even now, when I'm recovered enough to work, write, and paint, I can't eat anything but mild stuff like toast and chicken soup. It wasn't a computer virus, but it certainly wiped out my central processing unit.

It was so bad that I couldn't do any math or physics, or even read a book. I was in virus limbo for about two days. But by the weekend I was able to get out of the house and do ordinary tasks again. So I have returned to both art and physics. My current book of choice, which I will be using for some time, is the Barron's high school self-teaching text, hopefully called PHYSICS THE EASY WAY. I have commented on this condescending title in an earlier posting. But I regard myself as a perpetual beginner, so I am re-visiting the very basic things like scientific notation and concepts of measurement. After that, I'll work my way again through now-familiar territory like vectors, forces, time and distance, gravity, and of course, Newton's laws.

Newton's on Third again, and I would like to know where the equal and opposite reactions are. So I sent a message to one of my Friendly Scientists, who has been a wonderful teacher so far, asking what was really going on with Newton's Third Law. He replied with these enlightening words:

"The problem is that Newton's Third is usually stated incompletely or inaccurately….It only applies to what are called "static" situations. If the object or point of interest in a problem is not moving, then the total….force on that object must be zero….you "invent" the necessary "reaction force:" (like the floor pushing up, or the rope pulling back) such that the total comes out zero."

At which point, I finally got the notion. So THAT's what they're talking about with the equal and opposite reaction and the floor pushing up. I kept imagining inanimate objects coming to life with a will of their own, like animated cartoon characters, pushing or pulling me about.

But if I push something over, such as a styrofoam cup on the kitchen table, it is a situation with unbalanced force, which comes back into equilibrium when something falls over and comes to rest. (Like me with the virus, but its force was biological rather than Newtonian-physical.)

So I replied to the Scientist:

It seems like there is really a whole chain of things of different mass affecting each other through various forces. Earth, me, the chair, the kitchen table, the styrofoam cup, etc. It isn't as simple as it looks.

And he then replied:

"There is no action at a distance…. (this is) the key to mechanics….Forces are local, and local forces act, one point to the next and one object to the next, all the time."

Many thanks to this Friendly Scientist, who is so generous with his knowledge and time.
I must also mention another scientist, whose Website I mentioned eleven months ago, when I was just beginning to write this Weblog. This is the cosmologist Max Tegmark, whom I profiled in my entry for February 9, 2004. After I wrote that entry, I notified him by e-mail that I had written about him on my Weblog. I never got a reply from him, so I just figured that like all scientists, he was just too intensely busy to answer. Well, just a few days ago I received a reply from Max Tegmark, who had somehow found the 11-month-old e-mail and responded to it. He suggested that perhaps my e-mail had fallen through the cracks into one of his parallel universes. He was delighted that I had written about his "enchanted world" and wished me well. The blue Electron received a beam of winter sunlight that day.

An afterword to this discussion of forces and action: I say that there is at least one force that acts at a distance, though it is not a physical force. Culture and communication form their own "metaphysical" world. If there is any force that really does act at a distance, it is the force of the human imagination.

Posted at 2:52 am | link