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

I am currently in an argument on another forum about the difference between theory and proof.

As I understand it 'theory' is that which has been yet to be proven/observed and proof is what you end up with once the theory has actually been seen in action as it were.

The other person (who, frankly, is the sort who would disagree if you told him the sky was blue) is telling me that this is not the case at all and that in science 'theory' and 'proof' are pretty much the same thing as 'theory' doesn't carry the "negative best guess" connotations in science as it does for the rest of the world.

So which of us is correct?

In science, there is no such thing as proof. There's a hypothesis, which is something you suspect but don't have much evidence for, and there's a theory which is something you have lots of evidence for. So once something gets to be a theory, it is pretty much established as true.

So we have the Theory of Relativity, the Theory of Evolution, the Theory of Gravity. These are all verified by so much evidence that you would be mad to doubt them. But none of them are proved.

So basically we're both right in a way...

I would have said you're both wrong.

Harrumph!

'Proven' in its original sense means testing. For example, if you prove gold, you test it for impurities.

In this sense, in order to be a scientific theory, it must be proven. But its stll subject to being refuted by future proofs.

Amusing to mention the Theories of Gravity and Relativity, given that the latter replaces the former, which has been shown to be inaccurate.

Also, the common usage of 'theory' to mean something untested would map to the term 'hypothesis' in science.

Wait, those aren't paragraphs...(sorry for the horrible layout).

Mr D., you have mixed up "theory" and "hypothesis" - it's a common mistake.

So, "As I understand it 'theory' is that which has been yet to be proven/observed and proof is what you end up with once the theory has actually been seen in action as it were."

Should read more like

"As I understand it 'hypothesis' is that which has been yet to be **tested** and 'theory' is what you end up with once the hypothesis has actually been seen in action as it were."


There is no such thing as proof in science, as Gnomon says. You only get solid proofs in maths.

A theory in science does not mean "speculation" - as in the lay meaning of the word. It refers to an idea supported by many independent lines of empirical evidence. It's as close as you get to fact/certainty in science. Of course, creationists exploit this confusion when they say "ah, bu evolution is just a theory".


Ste

Proof was simply a bad choice of word... what I mean is something that not only has been observed and generally agreed upon, but also is unlikely to change when something new is discovered. A sort of 'theory plus'.

In the physical sciences they're generally called "laws". But in reality theory is as good as it gets.

However, some theories are more strongly supported than other, i.e., they have a lot more evidence backing them up. These are probably the ones you mean when you say "theory plus" - one bit of contradicting evidence wouldn't be enough to make people not accept the theory as 'true' anymore.



Ste

I'd slightly disagree with the Law thing. I would suggest a Law is an assumption rather than a theory.

For example the laws of thermodynamics essentially are a bunch of assumptions that limit any system. The mathematical theory surrounding thermodynamics comes from using these limits as a starting point.

I'll probably get beaten with a stick over that one though. It's probably rather a semantic thing Law v. Theory

Hits Orcus lightly with stick, as he's only half wrong.

Laws come in more than one flavour. Probably they most usually appear as statements of consistent mathematical relations between empirically measurable variables (Boyle's Law is a good example). This is different to a theory, since Boyle's Law is not an explanation, just a statement (we do, of course, have a well supported theoretical framework that does explain it).

The Laws of Thermodynamics initially appear to be the same kind of thing, but as Orcus suggests they are actually part of a framework of "assumptions" that are part of the definition of what constitutes physics. Strictly speaking, they are metaphysical (where this term is taken to include mathematics).

Noggin

One thing I will add is that it's foolish to assume anything about the truth or otherwise of something based on whether it's called "theory" or "law".

Okay, I can't stick to one thing. In pure mathematics, where things can be proven absolutely, the word "theory" very definitely applies only to things that are true. Number theory is basically everything that can be said to be true about numbers. Ditto for knot theory, graph theory and computability theory.

That is a very intersting way to think about thermo - one I'd not heard of before. Neat! And I agree with it - to a point. But now we have lots of evidence supporting these metaphysical assumptions. Are the laws of thermo now more than assumptions?

I put assumptions in quote marks for a reason.

Or to put it another way, post interruption, assumption in this usage bears the same relation to its everyday uasage as the word theory, as discussed above.

The difference between this kind of metaphysical proposition and an empirical observation is that the latter could have turned out differently.

Noggin

if anybody who is reading this lifts their mouse of the mat a few cm and then lets it go . it will immediately start heading towards the centre of the planet . before coming to an abrupt halt , when once again encountering the surface of the mat . is this not proof of the laws of gravity ?

best fishes ......tod

There are various other possible explanations for the mouse falling, such as that it is repelled by the vacuum of space.

Sort of. It doesn't help us decide if Newtonian gravity or General Relativity is the more accurate, though.

The Theory of Gravity is specific about the formula Force = GMm/d^2, where G is a constant, M and m are the two masses being attracted, and d^2 is the square of the distance between them.

Its pretty close, but it is incorrect.