Laws vs. theories...?

Question

I was watching a great debate (more of a slaughter) on evolution one day, and the creationist brought up the 2nd law of thermodynamics. To which his opponent explained that Earth is of course not a closed system. But, he also said that, in science, if a law and a theory contradict each other, it is the LAW that is thrown out, not the theory.

Is this true?

And if so, are there any examples of this happening in the past?

Answer 1

No this is not correct!

A law in scientific terms is just a concise statement or mathematical expression

A theory in scientific terms is a well tested explanation of observed phenomenon

A theory and a Law should never condradict one another. If they ever do it is the one which has been proved incorrect which is disgarded. It doesn't matter if it is the theory or the law, but whatever one has been proven to be false by experimentation.

Also as a side note the second Law of thermodynamics in no way condradicts evolution

Also this has happened many times before. It is the way science progresses. It learns by experimentation and never accepts that what is known today is 100% correct.

Answer 2

Sure.  Newton's law of gravity.  A law is an observation of something that appears to be true - an equation to predict what will happen.  Newton's laws of gravity worked very well at the time they were conceived, but not so much after we started observing the universe in detail.  Einstein's theory of general relativity not only told us WHAT would happen but also WHY it happened, which a law can't do - which makes a theory superior to a law.  And although Newton's laws still work very well on the scales we encounter on the Earth, we through them out when working on GPS systems or black holes.

Answer 3

Laws and Theories are entirely different animals, as far as science is concerned.

In science, a Law is an OBSERVATION. So the Law of Gravity states that "things fall down" (or, more accurately, that "all matter attracts all other matter in a manner proportionate to their masses and inversely proportionate to their relative distance")

This is simple phenomenology - an observation without any explanation of how or why it happens.

A scientific Theory is that EXPLANATION. So there are several competing Theories of Gravity: perhaps all matter emits gravitons (Graviton Theory), massless particles with negative momentum; or perhaps all matter somehow "curves" space/time (Relativity); or perhaps all matter is actually composed of subatomic "superstrings", vibrating and interacting in higher spatial dimensions (Superstring Theory). Obviously, these cannot all be true, and perhaps none of them is true.

In an instance where a law and a theory conflict (or, more commonly, where two theories conflict), you need to examine the evidence and decide which fits the evidence best; the one that does not fit is modified or discarded.

For gravity, as has previously been pointed out, Relativity explains some phenomena of gravitation that conflict with the initial Newton's Law. The Law has been shown to not be as universally true as once supposed, but it is still useful for many things, so it has not been discarded entirely.

However, it is the theory that is the highest ideal of science. Science does not just seek to find out what happens, but (more importantly) seeks to explain why and how it happens.

Answer 4

Not sure if this is what you're looking for (I'm not a proper scientist, so double-check me if you doubt), but a couple of things spring to mind:

First there's a matter of adding velocities: If you're on a train going at 50mph, and you walk from back to front at 4mph, you will be going at 54mph relative to the outside.

The idea that you can simply add velocities like this  was treated as an obvious mathematical law for a long, long time. However the speed of light is an absolute, so there is no difference in the speed it moves through the train compared to the ground. As moving objects get closer to the speed of light, which they can't reach anyway, some of the extra speed gets 'lost'. This is completely negligible for most speeds we work with, but the effect becomes more noticeable the bigger the velocities involved are. So the (useful, elegant) law turns out to have been inadequate and in need of replacement with a better law, but we only notice this once the theory has been corrected.

There's another example I can't quite remember. I'll edit if I do.

Edit: I was thinking of Wien's law for black-body radiation, (which was generated without much theory) being useful, yet proving to be inaccurate at low frequencies. As Planck made a theoretical breakthrough a substantially different law was generated which reduced to Wien's law at higher frequencies.

Unfortunately

a) It doesn't seems to have happened like that.

b) I don't really understand it.