h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

"Proposition: Any theory that explains a given set of physical observations is as valid as any other that explains the same set of observations."

Hmm, I think something is missing here.
A theory saying "Something is caused by thing" can't be valid if a theory saing "Something is caused by another thing" is valid.

an exsampel.
Theory 1: "The apple that hit my head did so due to the effects of gravity"
Theory 2: "The apple that hit my head did so due to the unmeasurable little green elfs that does everything you claim gravity does"
(Theory 3: "No, they are blue")

Ofcourse, the guy saying theory 1 might reply to the guy with theory 2 saying "That's what I said; gravity"

Hmm, again. Is that the point your trying to get across?

I've just removed this proposition, since it was giving me an amount of hassle disproportionate to its importance. Although I firmly believe that what I have in my mind is true, converting this idea into words that others can understand has proved to be a problem.

The key lies in the phrase "that explains a given set of observations".
If you had no data on the existence of gravity or of elves, green or blue, then each of your theories would explain the observations you had, and each would be valid within that set of observations.

Given a wider set of observations, you may be able to refine your theories and/or eliminate some.

Dry.

I think I get your point.

As long as a explanation covers the facts, it doesn't matter what that explantion is? Its all good

Or, Any theory not disproved is as valid as any other theory not disproved.

That opens up for alot of "crackpot" theories. aliens, gods, elvis, elves etc etc. But it doesn't matter as long as it works out.

So basicaly, "don't argue unprovable theories".

The way you put it, it does sound crackpot.

However, it is important to remember that some theories that were at first rejected as crackpot were later accepted on the grounds that they provide a better model of reality than the common sense alternatives.

Both quantum mechanics and relativity were at first opposed by people who said they were contrary to common sense. In fact, some people still say this, despite overwhelming evidence to support these theories. The same was true of the ideas of Copernicus, Galileo, Newton and Darwin/Wallace.

So you can't always say that, if a theory looks crackpot, it therefore is.

In practice, all else being equal (an important point), we normally apply Occam's razor and select for our models those theories that don't involve supernatural forces or other agents (e.g. elves or multiple universes) whose existence seems doubtful or unnecessary.

Dry.

I assume that means I got your point.

You say that theories should not contain "other agents". Isn't gravity just a descriptive label we have agreed upon to explain a given set of observations? " A rose by any other name would smell as sweet". What "realy" causes those effects is unknown It is something that follows a given set of rules. Look at how one would explain gravity: It does this and causes that. It is the force that cause movment, and acts upon bodies of differing mass. The explantion of gravity is based on what it does not what it is. Could not therefor any other explanation be as good (no, because people won't agree upon it) as long as it follows the given set of rules?

Ochrams razor is a very good principle, but it is not nesessarily right. I use it myself, but I have not seen it as an absolute. It is a practical rule to follow, but must the simplest explantation be right?

The best model for gravity (at present, as far as I know; please correct me if I'm wrong) is Einstein's General Relativity. This theory posits that any massive object, or concentration of energy, (these being equivalent), causes space-time to curve. Any other body will follow a geodesic, that is, a path of minimum distance within space-time. An observer will see the object move as if attracted to the massive object. This theory has been tested many times and has always given results closely matching observation.

Newton's law of gravity gives good results in most cases, but it is inferior to General Relativity when the gravitational field (or space-time curvature) is high.

I agree with your last paragraph: Occam's razor is a practical guide, not an absolute rule.

Dry.

True, Einstein's theory is the most accepted one. But as with most science we se only the effects and thus speculate about the cause. My point was simply that we, currently, can not see space-time curvation (is that a valid word?)but we can see the results of it. Object do move. So we cannot say the theory is an absolute, as few things outside pure math are, and since its not nessecarily true (althrough most, if not all, experiments say it is) one can not absolutly validate it. Thus, as Shakespeare put it, "would not a rose by any other name smell as sweet". I also was under the impresion that this was the reasoning behind your proposition "Any theory that explains a given set of physical observations is as valid as any other that explains the same set of observations."

I have the impression that we speak a little past each other. This is undubtably due to my lack of a propper education in physics and math, and the fact that english is not my mother toung.

I agree with your preposition, or rather what I think is the reasoning behind it. The validity of almost any theory is impossible to absolutly validate, therefore any (non disproved) theory explaining the same observations can also be valid. Thus the absolute validity of a theory is irrelevant as long as it produces the same results.
To give an exsample. If you see the result 5 and know that it is the product of a + operation it doesn't matter what you theorise that prosses to be (0+5,1+4,2+3) because they all fit the given observations and explain the result.

Or have I misunderstood totaly?