# In science, what is theory and law? What is better between the two?

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• A theory is a proposed explanation for something that we cannot directly measure or observe. It has to be based on scientific knowledge, it has to fit whatever evidence has been collected so far, and there must be ways in which we COULD prove it wrong, if only the right instruments existed.

If it is "just an idea", then it is a hypothesis IF it does not go against known scientific principles. Scientists usually begin with a hypothesis (a "what if" statement). Then they look at how it could represent how things really work, thus moving towards the establishment of a theory.

All theories contain suppositions and (often) incomplete or imprecise knowledge of the whole "thing". A theory is rarely "proven" true. A theory - as a tool of understanding - is usually classed as "useful" or not. For example, Newton's theory that helps us measure forces through mass and acceleration, for example

F = m a

is now known to be "false", especially where relativistic speeds are concerned (speeds close to the speed of light, relative to the observer).

If we had sufficiently precise instruments, you could even detect the difference in everyday events. However, the difference is so small (tenth decimal, for example) that we don't care. That pound of ground beef still weighs a pound even when it sits in your car, at 60 miles per hour; we don't care that, relative to an observer on the sidewalk, it now weighs an extra millionth of an ounce.

Newton's theory of gravity - although known to be "false" - is still useful.

Einstein's theory of Relativity (General Relativity, when applied to gravity) is more precise, but it would be difficult to convince the butcher to use tensors and vector calculus when selling you a pound of ground beef.

A law is something which seems to work, but we do not know why. Titius-Bode's law (for distance of main planets from the Sun) "works" sufficiently well that it helped astronomers to discover minor planets between Mars and Jupiter (Ceres, Vesta, Juno, Pallas, etc.) in the early 1800s. However, it breaks down when used with the outer planets Neptune, Pluto...).

It is even possible that there is no link between the mathematical formula and whatever excuse nature used to put the planets at those distances. After all, mathematicians know that given a small set of number (small could still mean hundreds), you can always come up with a formula to "explain" them. A "law" is such a formula, where we do not understand why it works.

Unfortunately, when something exists for a long time as a "law", it can continue to be called a law, even when a reasonable theory and explanation exists for it. Hence some confusion. There are no strict definition that partition them.

(partition = if it is one, then it cannot be the other)

Both of them (law and theory) are only valid under specific conditions - which are usually stated in "the fine print" which few people bother to read. For example, the law of conservation of mass only works in chemical reactions, not in nuclear reactions. Since, in everyday life, we are always dealing with chemical reactions, then it would appear to always work. However, the very few of us involved in nuclear interactions know better. Some of the mass COULD be transformed into energy, and vice versa. (E = m c^2)

• Anonymous
1 year ago

Law is our interpretation of what we have observed and measured more or less precisely ; theory is what we imagine about a possible event without any previous observation and/or measurement

• Sorry, but Laws are just common Theories.

Even the "Law" of gravity is now being contested!!!

• A theory may break the law assuming that the law is viable.

All laws are ruled by a Judge.

There are many theories and many of them is just a shot in the dark.

For example the theory of light was misreprented by a photon which has no mass or volume as opposed to a massive light particle moving in an oscillatory manner.

• I think the line is very fuzzy. It's just that laws have generally been around longer, and time-tested. I don't know why we still call it the Theory of Special Relativity, as I think it's withstood the test of time.

Laws don't need to work in every situation, they only need to work within the reasonable conditions defined for them. The laws of motion are an example - they don't work exactly in relativistic cases.

Outside of pure science, the word "law" is used more loosely. Moore's, Murphy's, and Cole's law.

• Simple:

Laws are the numerical or mathematical representations of theories or human-defined maths.

(With theories, in the cases such a thing is possible - not all can be stated as formula so do not have "laws").

eg. The "law" of gravity is the formula to predict gravitational attraction.

https://en.wikipedia.org/wiki/Newton%27s_law_of_un...

"Log law" (or the law of logarithms) is mathematical relationships between numbers when using logarithms.

Note that a "theory" in science has already been accepted as fact by the scientific community, laws are not related to "proof" - if it was not proven it would still be a hypothesis.

There is no "better", they are different things that have some overlap.

• A law is a phenomenon that we have observed to be true. But it gives no explanation or deeper insights. (Ohm's Law)

A theory is a well defined set of facts that gives a logical explanation of a phenomenon. (Theory of relativity)

In science, neither is ever completely proven because you never know if some new observation will someday falsify the theory or law.

• There is a hierarchy in the degree of validity or confidence of knowledge. [See source.] It goes like this starting with the least confident level and working up:

Educated guess--we have preliminary observations and tests used to create a model

Hypothesis--we rigorously test a more concrete guess (the hypothesis) using the model and scientific method

Theory--if the test results support the hypothesis, it becomes a theory; otherwise, it does not (back to the drawing board)

Law--in some cases, when a theory survives the test of time and multiple testing, it will morph into a law (this is very iffy so it doesn't always happen this way)

NOTE: There are lots of misnomers in the scientific community, which is not noted for using good terminology. For example, String Theory. It's hardly a theory by any criterion; in fact it isn't even a hypothesis as it cannot be tested. There is no model to test it by.

Source(s): I taught the design and analysis of experiments at the MS level, this course dealt with hypothesis testing and the scientific method.
• a law is demonstrable (as in you can demonstrate it) a theory just has strong evidence

• A law has been proven, a theory hasn't.