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Tuesday, June 09, 2009

Direct Observation

How much do we know about our world from direct observation? Consider a pretty basic law at work all around us all the time. Newton's first law of motion is that "a body at rest stays at rest, and a body in motion stays in motion, unless it is acted on by an external force." Doesn't this contradict what you have directly observe--that is, things in motion eventually come to rest.

At some point in high school you learned that when a body moves over any surface there is a force that action opposite to the direction of motion. That force, which we call friction, is different for different surfaces and proportional to the normal force against the surface. So the heavier the object, the higher the Force of Friction, but if you put the body on an incline, the Force of Friction decreases. By the way, while you are pushing on an object that doesn't move, the force of friction increases exactly to keep pace with the force you are putting on the body. (How does it know to do that?)

Anyway, friction is also why things in motion tend to come to rest; there is a force acting on them. Or so we've been told. Which is my point, do we directly observe Newton's first law, or is it a convention we learned? Do we, everyday folks, have any reason to feel any more certain about it than people from the Dark Ages had to feel certain that if you knocked on wood it would scare away the fairies that caused bad luck?

And this isn't even talking about carbon dating or evolution or red shift; it's about what really happens when we push a box across the floor.

3 comments:

Matt Dick said...

It's a good question of epistemology--How do we know what we know.

I think the answer is a combination of things:

1) For some people there is substantially no difference between their understanding of Newton's Law and a Middle Ages person's understanding of faeries. Their authorities for how to understand the world are priests, teachers, god and the weight of society at large. It's a pretty darned good way of getting through your day for the most part, so it's hard to find a god reason to spend a lot of time questioning that infrastructure.

2) A similar condition exists for all of faith, it seems to me. Faith by definition is not evidence-based, at least not externally verifiable evidence. You can know that doing certain things makes you feel a certain way, that's internal evidence--you can't verify that against a stationary standard. You can see, in a manner of speaking, a moral force moving in a community. That's observable on something approaching an objective way, but I think most people would agree that the origins of such a movement could be explained without appealing to a supernatural force. So in that sense the spiritual/faith discourse in human nature seems locked into the "direct observation but not objectively measured" paradigm.

3) Science, as it is currently and most popularly understood, is in a different category. First of all, I'm not sure there was as good a distinction 1,000 years ago between matters of faith and matters of natural science. Knocking on wood to scare the faeries might not have been seen as substantially different than boiling your water during a plague to scare the water demons (or whatever, I made that up).

The difference is that science is available to the ordinary person now (in the west, with a proper education, etc). I can go verify any article of faith I want. You're right that Newton's First Law is not intuitive in how I live my life and for the most part I take it as an article of faith. But unlike my counterpart from a thousand years ago, I can ask why and go get answers, and I can verify those answers. I can keep investigating the reasons behind each of the explanations I get until I am fundamentally testing those observations and explanations. I can eventually decide for myself through testing that friction and motion work the way they are explained to work. In fact, very unlike the received wisdom of the Middle Ages, *anyone* of any caste, class, stripe, family, or profession can *become* one of the priestly class (to use the metaphor) if they investigate the questions and answers and find a newer, better explanation for them. This meritocracy in the marketplace of ideas makes the information in the "received" wisdom of today inherently more reliable than the wisdom of the past.

Did that make sense?

JimII said...

"I can keep investigating the reasons behind each of the explanations I get until I am fundamentally testing those observations and explanations. I can eventually decide for myself through testing that friction and motion work the way they are explained to work."

You can certainly get explanations. I'm not sure about at what point you get evidence. Our explanations are certainly more layered than the explanations of the middle ages, but obviously that does not on its own make them better. And in any case, we are still generally relying on what you later call received wisdom. (Which I love.)


"In fact, very unlike the received wisdom of the Middle Ages, *anyone* of any caste, class, stripe, family, or profession can *become* one of the priestly class (to use the metaphor) if they investigate the questions and answers and find a newer, better explanation for them."

This is very interesting. We benefit by drawing from a larger pool and evaluating based on merit. I had not thought about the role this has in the quality of our science. I think you're right.

And, although I'm sure most people understand this, but I also think friction is real and wood fairies are not.

Matt Dick said...

I'm not sure about at what point you get evidence.


I think you get evidence. When you see rainbows in oil slicks and ask why, and the principle of thin film interference and destructive/constructive interference is explained to you, at that point it is received wisdom.

When you graduate with a degree in optical physics from any of a number of universities, I think you've explored the evidence enough to say it's a faith only in the properties of the universe being a constant.

We all stop somewhere between those two inclusive extremes. The extent to which we *have* to stop is the extent to which we are compelled to accept it as received wisdom, as opposed to the sober and wise deference to expertise. This is the practical answer to having to do original research into every claim in the universe/

Stated another way: You and I should accept the principle of Newton's First law based on a basic understanding of physics and an assurance from Kyle and his physics PhD that it's Newton's First Law all the way down.

The medieval farmer should *not* accept from clergy that wood faeries are doing whatever in the world wood faeries do because his expertise is based on a field of study that is closed off from that farmer.

Both "received wisdoms" are handed down from experts, but one comes from a tradition of transparency and is ultimately open to us as a field of study. The other comes from a closed system with traditions opaque to the audience.