I once saw a student in a metaphysics lecture ask the lecturer ‘Ah, but what if we’re all just brains in vats and this reality is virtual?’ He told her that this reality being virtual didn’t make any difference to the material we were discussing, and that the concern of whether or not it was the case was one of epistemology, and didn’t fall within his syllabus.

Scientists will normally have a similar view. Could the rules change? It’s not likely, but I can’t prove they won’t. So what are we going to do if they do? Well I can’t prove they will, I would have no idea when it would be, and I don’t know what they would change to, so it would be a complete waste of effort to try and work it out. I’ll get on with my valuable work refining our existing model and working out useful things that work within it.

So you’re right, of course: it’s just like religion. You can’t disprove each other’s viewpoints, so neither of you is wrong, but that doesn’t make either of you right, and the whole argument is probably a complete waste of time. Sounds like you just couldn’t help but try though. I tend to be the same.

Actually, reading ‘The Big Bang’, recently Adrian, I’m quite stunned by how many times science has gone through a paradigm shift, and how all the existing scientists grip, totally unreasonably, to their exisitng dogma, even when it defies reason to do so.

I generally agree that we should take existing, proven science as our theory for existence. But it’s still only a theory, waiting to be disproven. Without the sort of imaginative leaps your friend was willing to make, we’d never have come up with relativity, never known the Earth orbits the sun, never uncovered evolution, never discovered the big bang- all of which are enormous paradigm shifts which were very powerfully pushes back by the existing scientific establishment.

I agree. But we must be vigilant against scientific arrogance.

It’s a commonly perpetuated fallacy that there are situations where “Newton is right” and others where relativity/quantum mechanics are needed to refine Newton.

It gives rise to a perception that there is some kind of sharp cut-off between Newtonian objects and non-Newtonian, which just isn’t the case.

It is not true to say that Newton’s laws apply to billiard balls - they don’t. However, on the scale of billiard balls, the difference between the predictions of Newtonian mechanics and those of either relativity or of quantum mechanics are so small as to be impossible to detect.

(Therefore an engineer would say that Newton is right in these circumstances but a mathematician wouldn’t - Adrian’s error is therefore understandable)

As the objects you are observing get smaller, the quantum effects get more pronounced until the differences are measurable between Newtonian and Quantum Mechanics, but this is not a sharp cut-off.

As objects get larger/heavier/faster then relativistic effects become more pronounced until the differences are measurable between Newtonian and relativistic mechanics, but again this is not a sharp cut-off.

One of the biggest problems being tackled today is the fact that QM and relativity are incompatible with one another (although both are “compatible” with Newton in that they don’t contradict Newton at the everyday scales of which Newton is a part). This doesn’t matter most of the time as objects are typically either too large for quantum mechanics to be important or too small for relativity to be important (or, in most cases for engineers, both [exceptions being electronics/communications where QM plays a part; I can’t think of any circumstances where an engineer has to allow for relativistic effects, other than in research into such effects]).

However there are certain circumstances where you have both relativistic and quantum effects within the same scales, and at this point things become very hard to predict with either theory as they contradict one another, and this is why theoretical physicists are looking for a unified theory which doesn’t have these contradictions.

Examples of these circumstances are: -in the early universe; -near black holes; or -in particle accelerators. (And these circumstances have a lot of parallels with one another which is why particle accelerators are key to research into the early universe).

As to Dan’s point, there are paradigm shifts, but if science is beind done properly these only happen when the existing theory has been shown BY EXPERIMENT to be inaccurate.

This can arise in one of two ways:

1. An experiment shows that the existing theory isn’t right, and all other explanations (experimental error etc) have been ruled out. At this point theoreticians come up with a new theory which explains the apparently anomalous result.
2. A theoretician comes up with a new theory from pure thinking.

The first is far more common.

In either case, the next step is to find a situation in which the existing theory gives different predictions from the new one. In situation 1 this has already been found but to be rigorous one should find a different situation as the test.

Then you devise an experiment which gives rise to that situation, and see from the result of that experiment which theory gave the right prediction.

Ideally you repeat this with other situations to give more weight to the eventually adopted theory.

If the new theory does not give any different predictions than the old one then it is not really a new theory but a reformulation of the existing one. In practice, then, neither theory is “better” but usually scientists will plump for the one which is easier for them to use (possibly with the use of Occam’s Razor). For example there are a number of interpretations of Quantum mechanics and the collapse of the wavefunction [many worlds, probabilistic interpretations etc] which give the same results and are all equally valid.

However, and this is the key point, while the existing theory continues to hold for all the tests we are able to throw at it, there is no scientific basis to question its validity. Just saying it might be wrong is not a valid argument (from a scientific perspective). “Imaginative leaps” may be a good intellectual exercise but they are not science until they have been tested by experiment.

It is human nature to cling on to existing beliefs, and that is why there is often resistance to a new theory. However this is why we have a scientific method.

We will (probably) always continue to find new areas of science to explore and theories will always be overturned. But if we’re still around a billion years from now then whatever strange and wonderful scientific theories we have, I can guarantee without any doubt that they will include (for example) the fact that the gravitational attraction between 2 bodies is G x m1 x m2 / r2. We KNOW this is true. But that shouldn’t stop us continuing to test it.

so what do you say if I say that somewhere in the universe/galaxy/whatever there is another planet with ‘people’ on it.

Its called the ‘reductio ad absurdum’ - ie. reducing every argument to the absurd, so that you can never win the argument.

So say for example, i say that medical insurance is too expensive. You counter with it can never be too expensive if you die. The end of the argument….

Reductio ad absurdum (or proof by contradiction) is logical proof of a claim A by adding not A to the axioms of your system and deducing that the system is no longer valid, and hence that not A cannot be true.

While what Marl says is true as a transliteration, the use of the phrase is misleading. The Wikipedia article for reductio ad absurdum explains quite nicely its likeness to logical fallacies such as those appealed to in the above example.