Laws and Theories

When I used to hear people use the phrase, “laws of physics”, I wondered why they didn’t say “laws of science” instead? I mean, why exclude chemistry and biology? Later I learnt that the reason is that physics deals with fundamental concepts. And the other sciences are built on top of physics. For example, physics talks about the basic building blocks like quarks and electrons and photons (Well, ok, they keep breaking everything further and further…but that doesn’t change the point being made). Chemistry, on the other hand, is all about how combinations of building blocks behave. And biology is one level higher still than chemistry.

Then I noticed the terminology difference. Until the 20th century, every major concept of physics was called a “law”. Like the Second Law of Thermodynamics and Newton’s Laws of Gravitation. On the other hand, the most famous physics concepts of the 21st century are called “theories”, not “laws”. Like the Theory of Quantum Mechanics and the Theory of Relativity.

The reason for that change in terminology is interesting. The word “law” implies infallibility. And as every school kid is taught, you can never prove a theory about the real world. The next observation that agrees with theory only increases your confidence in the theory. But all it takes to disprove a theory is one observation that doesn’t agree with it. In other words, it is possible to disprove a concept but impossible to prove it!

But on this terminology front, biology beat physics. The most famous law, sorry theory, in biology is evolution. And Darwin came up with that in the 1800’s. So had biologists understood proof is impossible way before the physicists did? Maybe, maybe not. I suspect the reason may have had more to do with the Church’s opposition to the concept of evolution. By calling it a theory (instead of law), which by definition could be wrong, the Church got its escape route to continue denying evolution and to continue preaching creationism. Like I said before, Shakespeare was so wrong when he wondered whether a name was important!

Comments

  1. KumarSeptember 29, 2010 at 3:27 PM

    I don't think physics has yet come around to abandoning the idea of laws. The use of the idea 'theories'is not just about 'not so sure of it all, as of now'.

    A theory is at a complex or bundled level, compared to a law, which is on a simpler focus. For example, the theory of relativity also takes a law for granted. It is the 'law of the constancy of the velocity of light'. After that, the theory goes far beyond in complexity.

    We therefore find that physics is not yet stating calling laws as hypothesis, though in a sense, we should treat all laws as hypotheses. But we don't do it. For example, till about 3 or 4 decades back, what used to be called the Avogadro Hypothesis, is currently termed as Avogadro Law, because it was realized that it deserved the identification as a law. (Avogadro law is part of the physics domain too and in the same capacity, so we cannot not say, "Oh, it is about chemistry!")

    ReplyDelete
  2. Viswanathan K.October 2, 2010 at 4:35 PM

    Yes, now that you mention it, it's true that laws are relatively "simpler" whereas theories are more "complex".

    The Avogadro Law bit was new to me...though I'd still call it chemistry :-)

    ReplyDelete

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