When does science change a theory?

[FireGarden]

Not immediately after observations that conflict with the theory's predictions.

The orbit of Uranus wasn't exactly as predicted, but that wasn't enough to throw away Newton's theories of motion. They had a brilliant track record. They deserved to be defended. And they were vindicated with the discovery of Neptune.

Similarly, with the orbit of Mercury and Maxwell's predictions about the speed of light. Of course people tried to patch things up. Predicting planets that nobody has ever found, suggesting an ether in which the speed of light was constant. You don't immediately throw away previously succesful theories.

The obvious idea is that sometimes unexpected observations do not always suggest how a new theory should be formulated. So scientists try to stay within the framework of the old theory. A little like monkeys, perhaps. They only let go of one branch when they've grabbed hold of the next.


[In starting this thread, I'm trying to broaden and change the venue of the discussion at the end of the ID and the tapeworm thread in R and P. In that, Stamenflicker linked to this site http://members.iinet.net.au/~sejones/index.html from which he lifted some quotes on the nature of the scientific method. This wasn't one of them, but it might serve as something to base discussion around.]

"Our theory of evolution has become, as Popper described, one which cannot be refuted by any possible observations. Every conceivable observation can be fitted into it. It is thus "outside of empirical science" but not necessarily false. No one can think of ways in which to test it." Birch and Erhlich http://members.iinet.net.au/~sejones/scienc03.html

Which doesn't sound correct to me.
If studying heredity had revealed a multitude of methods (a four letter CAGT code, a five, six, X code; or other four letter codes) we'd have less evidence of common descent. In the extreme, if every lifeform had a different method, then how could evolution continue to stand in its present form? We'd have to the except the suggested alternative of micro, but no macro, evolution that some creationists insist upon. If every child was a carbon copy of its parent, we'd have to reject micro-evolution too. Evolution would never have gained its status as "dogma".


These were quotes chosen by Stamenflicker

Mathematically each of the three different formulations [for the theory of gravity] ... give exactly the same consequences. What do we do then? You will read in all the books that we cannot decide scientifically on one or the other. That is true. They are equivalent scientifically. It is impossible to make a decision, because there is no experimental way to distinguish between them if all the consequences are the same. But psychologically they are very different in two ways. First, philosophically you like them or do not like them; and training is the only way to beat that disease. Second, psychologically they are very different because they are completely un-equivalent when you are trying to guess new laws.

[R. Feynman]

"A scientist commonly professes to base his beliefs on observations, not theories. Theories, it is said, are useful in suggesting new ideas and new lines of investigation for the experimenter; but "hard facts" are the only proper ground for conclusion. I have never come across anyone who carries this profession into practice - certainly not the hard-headed experimentalist, who is the more swayed by his theories because he is less accustomed to scrutinise them. Observation is not sufficient. We do not believe our eyes unless we are first convinced that what they appear to tell us is credible. It is better to admit frankly that theory has, and is entitled to have, an important share in determining belief."

(Eddington, Sir Arthur [late Professor of Astronomy, Cambridge University], "The Expanding Universe," Penguin: Harmondsworth, Middlesex UK, 1940, p.25)

"During the period of nearly universal rejection, direct evidence for continental drift - that is, the data gathered from rocks exposed on our continents-was every bit as good as it is today. .... In the absence of a plausible mechanism, the idea of continental drift was rejected as absurd. The data that seemed to support it could always be explained away. ... The old data from continental rocks, once soundly rejected, have been exhumed and exalted as conclusive proof of drift. In short, we now accept continental drift because it is the expectation of a new orthodoxy. I regard this tale as typical of scientific progress. New facts, collected in old ways under the guidance of old theories, rarely lead to any substantial revision of thought. Facts do not `speak for themselves', they are read in the light of theory."

(Gould S.J., "The Validation of Continental Drift," in "Ever Since Darwin: Reflections in Natural History," [1978], Penguin: London, 1991, reprint, p.161)

 

[FireGarden]

Just realised,
Predicting a new planet is a change to the theory, because the old theory included the assumption of 9 planets.

But it's not a radical change. That's the kind of change I meant to address.

 

[Math]

Are you talking about theories or hypotheses?

 

[FireGarden]

How would you classify Newtonian mechanics and evolution? Either way, feel free to discuss the different attitudes to theories/hypotheses

 

[FireGarden]

Oh I see what you mean now!
Hypothesising a new planet is not the same as changing/putting forward a new theory.

Still,
Feel free to discuss from any angle you like.

I'll learn to think before I post, one day.

 

[Dr Adequate]

"Our theory of evolution has become, as Popper described, one which cannot be refuted by any possible observations. Every conceivable observation can be fitted into it. It is thus "outside of empirical science" but not necessarily false. No one can think of ways in which to test it." Birch and Erhlich

Not only is this nonsense (who are these people?) but they also take Karl Popper as their authority.

One example, in particular, of near-correct quotation involves philosopher Sir Karl Popper. In 1976 Popper said, "Darwinism is not a testable scientific theory but a metaphysical research program." But Popper is not an expert in the biological sciences or their history. Furthermore, he is not the only philosopher of science in the world with anything to say on the subject of evolution. Philosophers often disagree with each other more than scientists do. And, to top if off, Popper has recently changed his mind on his earlier pronouncement against evolution. In 1978 he wrote, "I have changed my mind about the testability and logical status of the theory of natural selection, and I am glad to have the opportunity to make a recantation."

Yes, this was the man who originated the whole "survival of the fittest is a tautology" nonsense, he publicly admitted his mistake in 1978, and here were are in 2005 and the creationists are still using him as an authority. Well, what else have they got?

 

[roger]

It's trivial to falsify evolution. All we would have to do, for example, is show evidence of Lamarkian adaptation. You know, a species needs feature X, and so the descendents receive that trait without evolving it through mutatation and selection. Tada, falsified.

In essense, show any kind of change to a species that occured not due to selective descent.

 

[Paracelsus]

Hasn't modern physics showed flaws in the Newtonian physics? If they have found flaws why do we teach our children Newtons work?

Maybe it is because Newtons work still gives us a valid approximation to the observable world where Newtons theory doesn't break down.

To my knowledge the case is the same with Darwins concept of Evolution, modern biology has had some progress with the concept and have a revised Evolutionary theory derived from Darwins work.

 

[Jeff Corey]

Well, my last physics course was in college decades ago. But Newton's laws worked well enough for peole to walk on the Moon and send robots to explore Mars.
But that's at relatively pun slow velocities. Approach c, things get weird.
And when things get weird, the weird turn pro.

 

[Dr Adequate]

To my knowledge the case is the same with Darwins concept of Evolution, modern biology has had some progress with the concept and have a revised Evolutionary theory derived from Darwins work.

Where Darwin could only say "inheritance with variation plus the law of natural selection", we can say "the laws of genetics plus the law of natural selection".

 

[Eos of the Eons]

I think "survival of the fittest" should be changed to "survival with the traits that are most fit for the conditions that exist at that point in time" or something to that effect.

 

[FireGarden]

Here's a talkorigins piece on what science is.
http://www.talkorigins.org/faqs/evolphil/falsify.html

I guess I'm a pragmatist

Pragmatism, the only philosophy to have originated in North America, holds that the truth or value of a statement like a theory or hypothesis lies in its practical outcomes. Pragmatists say that being scientific is a retroactive label given to what survives testing and makes a real practical difference, like a theory about a cancer affecting how that cancer is treated, more successfully. Progress in science is the accumulation of theories that work out [Laudan 1977].

Plus perhaps an attitude of science being models that are adequate rather than theorems that are true/false. Which is consistent with Newton still being used.


Observations that are not in line with predictions will tell us that there is something wrong with our understanding. Some people will try to iron things out from within the current system (EG: hypothesising the existence of a new planet to explain Mercury's orbit. If such a planet is observed it becomes an observation that is fed back into the original theory - so nothing is really changed in the sense I'm talking about). Other people will look for a new theory that doesn't require unobserved objects - such as a new planet.

Scientists can be from either group. But science itself is built from the ideas that are confirmed from some observation - ie: not simply from the hypotheses of scientists.

 

[Paracelsus]

Scientists can be from either group. But science itself is built from the ideas that are confirmed from some observation - ie: not simply from the hypotheses of scientists.

Well as I see it science is also prediction of future observations, by explaining past observations. But I guess I'm a positivst.

positivism: theoretical position that explanations must be empirically verifiable, that there are universal laws in the structure and transformation of human institutions, and that theories which incorporate individualistic elements, such as minds, are not verifiable.