What's a law of nature?

Question

Scientifically, like the sky is blue...

Answer 1

A scientific law is an observed regularity and often involves quantities. Unlike a theory, a law makes no attempt to explain why the regularity should exist in that particular form rather than another. Examples would include the inverse square law for light intensity or Newton's three laws of motion or the three laws of thermodynamics:

1. Energy is neither created nor destroyed. (You can't win.)
2. Entropy of a closed system always increases. (You can't break even.)
3. Energy is at a minimum at absolute zero and increases with increasing temperature. (You must play the game.)

Answer 2

A law of nature is a short form for a vast amount of knowledge, experimental and theoretical, that forms a crucial part of a theory. Sometimes the laws are a backbone from which most of the theory can be derived, but mostly they aren't. And in order to work with a theory one has to understand under which conditions the laws have been verified and to what extent we know that they hold and in which areas we are uncertain.

I usually call that this the "fine print" of a theory and it changes all the time. Without this fine print the laws are virtually useless, except maybe as questions in high school tests.

Much of the difference between high school level and university level physics is that the fine print behind the laws is not sufficiently explained and the student is not forced to think about what the consequences of these details are. As a result most students get the wrong impression about theories as fundamental and unalterable monoliths of scientific knowledge. Nothing could be further from the truth.

Good theories carry their own demise in them and great scientists who came up with new theories were able to exploit this to derive new theories from old ones. If we had a chance to teach this in school, science would actually come alive rather than appear as this legalistic nonsense we usually teach.

Answer 3

In the practical sense, a "law of nature" is something that goes through the following stages:

1. An idea (that something is or isn't true)

2. An experiment or series of experiments to test the idea in #1 above.

3. A theory (to explain observations noted in #2 above.

4. Publication or other means of dissemination to get others to attack the theory as noted in #3 above.

5. After a while working on #4, the scientific community will have a conference at which someone will discuss the theory and all recent results testing it. Eventually someone will call it a law.

As to the conferences, trust me. There is nothing a stuffy old scientist likes to do better than go to a conference and talk techie with his/her buds. They get to eat a lot, drink a lot, talk a lot, and show off what they know to others. Sometimes they even get to say "I told you so" to their rivals. What's not to like? But of course, to give it a more formal appearance, it won't be a convention or a conference. It will be a colloquium.

Gotta have the high-falutin' name for it or you can't charge it as a business expense.

Answer 4

A law of nature is basically a theory with a bit of an ego problem.

At one point in time, the laws were thought to be absolutes... effectively facts. As we learned more, it was discovered that this isn't necessarily true.

Some laws haven't yet been shown to be wrong (for example, the zeroth law of thermodynamics). It is possible that these are, in fact, absolutes. But we can't prove or disprove it yet.

Other laws have been shown to be wrong. For example, Newton's law of gravity is incorrect. Same with the second law of thermodynamics (entropy). Both are accurate for everyday use. However, under extreme conditions, the laws fail. Newton's law fails under intense gravity (like near the surface of the sun, or near a black hole). The second law of thermodynamic has been shown to be a 'statistical law' where it's possible for it to fail, but REALLY unlikely.

Answer 5

Your example is not a law of a nature, the sky is not always blue. A law is a truism that has withstood all experiments to prove it wrong.

Answer 6

The "natural laws" are said to those that describe nature and are therefore valid throughout the world - and throughout the universe. Their opposite are laws made by society, usually to provide order.

Answer 7

Here's an example --
If you bring two objects into thermal contact, and wait, eventually they will come to a common temperature.