What is a Scientific Theory?

[RSLancastr]

Can anyone explain, or point me to a site which explains, in simple layman's terms, what a "theory" is to a scientist, and how it differs from a hypothesis, etc.?

I am starting a discussion at work regarding ID vs. Evolution, and want to lay the groundwork very carefully, as I don't have the education in science to know my stuff here.

Again, this needs to be in very simple layman's terms, since the explanations I am finding on the web are not clear to me.

[Shalamar]

http://www.notjustatheory.com/index.html

That may help..

[Hindmost]

Paul Hewitt is one of the best at answering such questions...his conceptual physics book probably has a great outline...but I don't have one anymore since I no longer teach. However, asking the question online may help with this website.

http://www.phschool.com/forms/cpsurf_hewitt.cfm

I will refrain from trying my definition...

glenn

[fuelair]

Quick and dirty textbook version: A Theory is an explanation of how something works based on observation and experiment. It is subject to change if better observations/experiments come along, but it is the best explanation we have at this time.
(A Law is not an explanation of how, it is a statement of what has been observed to occur by lots of people observing/experimenting many times. The Law of Gravity describes gravity but does not explain it, The Laws of Thermodynamics describe how heat moves but do not explain it. And the Theory of Evolution explains how evolution occurs - to the best of our current knowledge/observation/experiment.)

[Chupacabras]

Probably your concern is about scientific, instead of "theory". IMHO this is the central issue - perhaps the only issue - in ID disputes.

In that regard, for a theory to be "scientific", it must be based on evidence, and this evidence to be considered as such, must be observable and measurable. Very important: a theory has to be falsifiable.

Take gravity: we don't know what makes it work (gravitons or some sort of magnetism), but we know that objects fall to the center of Earth no matter what. In vacuum, in this planet (related to its mass), objects fall at 9.8 m/s squared ("squared" means it is not constant speed, but that it accelerates in each passing second). A rock or a feather respond equally. Since we know other planets' mass, we can put gadgets in orbit or even land a rover or two safely.

It I "drop" two objects in vacuum and they don't both fall to the center of Earth at 9.8 m/s squared, then its false, and I'd have to devise a new theory altogether.

HTH

[Olowkow]

My best shot:
In science, a theory is a generally accepted testable "model" based on factual observations of how natural phenomena interact. It predicts similar future occurrences and can be proven to be incorrect if its predictions are false.

[sol invictus]

According to wiki:

Quote:

In science a theory is a testable model of the manner of interaction of a set of natural phenomena, capable of predicting future occurrences or observations of the same kind, and capable of being tested through experiment or otherwise verified through empirical observation. It follows from this that for scientists "theory" and "fact" do not necessarily stand in opposition. For example, it is a fact that an apple dropped on earth has been observed to fall towards the center of the planet, and the theories commonly used to describe and explain this behavior are Newton's theory of universal gravitation (see also gravitation), and the theory of general relativity.

According to Britannica:

Quote:

systematic ideational structure of broad scope, conceived by the human imagination, that encompasses a family of empirical (experiential) laws regarding regularities existing in objects and events, both observed and posited. A scientific theory is a structure suggested by these laws and is devised to explain them in a scientifically rational manner.

Wiki's is better.

[rockoon]

The first law of motion.

Nobody can answer why objects in motion tend to stay in motion. Nobody knows! Just the same, objects in motion do tend to stay in motion, a fact that we regularly take advantage of. We might theorize about why, but we still don't know!

A successfull theory fits observation. There is a clear seperation between explanations and observations.

These explanations (theories) are neither right nor wrong, as it is not their purpose to be either. Their purpose is to predict observation! They either show skill at predicting future observations, or they do not. Theories that do not show skill are worthless trash, however theories that do show skill are neither "correct" nor "right." They just happen to fit observation.

A law is an observation which can be predicted with such great accuracy that it has become unimaginable to expect to observe any differently.

[Mojo]

Originally Posted by RSLancastr

Can anyone explain, or point me to a site which explains, in simple layman's terms, what a "theory" is to a scientist, and how it differs from a hypothesis, etc.?

Very briefly: a hypothesis is an idea, based on observations, to explain those observations (what is meant by "theory" in layman's usage). A scientific theory is a hypothesis that has been tested and is backed up by a large body of evidence.

All theories start as hypotheses, but not all hypotheses make it to theory status - many have to be abandoned when tested because they don't fit all the facts.

Observations >>> hypothesis >>> further observations to test the hypothesis >>> further observations all fit the hypothesis >>> theory.

[Showmeproof]

a pretty simple, straight-forward answer.

"A theory predicts events in general terms, while a hypothesis makes a specific prediction about a specified set of circumstances."

"A theory is has been extensively tested and is generally accepted, while a hypothesis is a speculative guess that has yet to be tested."

Basically, a hypothesis is an assumption and then becomes a theory when it has lived up to scientific testing. Example:

Hypothesis: I am so good looking.

I then want to test my hypothesis. So, I try to sleep with as many females as I can, and if I succeed, we can ascertain that my hypothesis is correct. If it repeatedly lives up to scientific scrutiny/testing, it becomes a theory.

[rockoon]

Originally Posted by Mojo

All theories start as hypotheses, but not all hypotheses make it to theory status - many have to be abandoned when tested because they don't fit all the facts.

Observations >>> hypothesis >>> further observations to test the hypothesis >>> further observations all fit the hypothesis >>> theory.

This is not quite accurate. Many theories cannot predict all related observations, but are successfull theories non-the-less.

For instance, there is no general method to calculate how much pressure is required to push a specific volume of water, through a pipe of a specific radius, at a specific rate.

There are special cases where we can calculate with great accuracy what pressure we will find is sufficient for the task, but there are cases where we cannot make any reasonable prediction about how much pressure is required.

This does not make the theory wrong or useless. It just means that there is more going on than is being addressed by the theory. Turbulance, and so forth.

[fls]

Originally Posted by Showmeproof

Basically, a hypothesis is an assumption and then becomes a theory when it has lived up to scientific testing. Example:

Hypothesis: I am so good looking.

I then want to test my hypothesis. So, I try to sleep with as many females as I can, and if I succeed, we can ascertain that my hypothesis is correct. If it repeatedly lives up to scientific scrutiny/testing, it becomes a theory.

Sigh.

Why does everyone forget to consider disconfirming evidence?

Have we established that females won't sleep with non-good-looking men? Or is it like the women who all agree are too ugly for sex, yet still manage to become pregnant?

Linda

[Showmeproof]

Originally Posted by fls

Sigh.

Why does everyone forget to consider disconfirming evidence?

Have we established that females won't sleep with non-good-looking men? Or is it like the women who all agree are too ugly for sex, yet still manage to become pregnant?

Linda

Well, they will sleep with non-good-looking men, as long as that man has money. Also, depends what the female looks like!

"Or is it like the women who all agree are too ugly for sex, yet still manage to become pregnant?"

Immaculate conception

[ile]

I would not dare give an answer in the context of philosophy of science. I can however give you some comment from a practitioner's point of view. In physics it is quite usual to make a _qualitative_ distinction between theory and model (rather than hypothesis).

Hypothesis are, in my view, constituents of both models and theories. I do not rightly know how to distinguish between hypothesis and principles, although I _feel_ that such a distinction exists. To give a concrete example, one could talk about the cluster decomposition principle in the context of a relativistic quantum theory as being a formalized version of the hypothesis that particles will not interact if they are very far apart. And this is a constituent of quantum field theory (which is, in Weinberg's presentation, the only quantum theory which is consistent with a number of principles).

Now, models are tools to understand or to build a theory, which will be far more encompassing than a limited model.

This, I'm afraid, is probably of no use in the discussion you intend to carry out at work (which I find extremely odd, anyhow: in Europe no one - except some clearly identified crackpots - will ever question that evolution is a scientific theory; and I know of _NO_ religious objection to evolution and its teaching currently in a European context).

I guess the real point is on the meaning of scientific proof, and the problem that many people have with the notion of certainty.

In this regard, this week I will participate in a series of conference organised by the local council (town hall / municipality) two of whose objectives are _precisely_ (I translate): explain the limitations of scientific knowledge; put forward the idea that there is usually a diversity of proposals and points of view of scientists confronted with a scientific problem.

I would have written it otherwise, because most lay people read that as meaning that anything goes, which is obviously false; but it is anyhow an important aspect of science that there is debate...which must be settled by a better theory and experiment.

Anyhow, I guess you should be stressing that scientific knowledge, be it theory or model, is _always_ provisional __and__, at the same time, __established__, if it describes all available data in the range it purports to describe.

So, the theory of evolution is most definitely scientific, therefore provisional (which is what the woo-woos try to emphasize to diminish it), but you should also stress that it will always be part of the scientific corpus since it has huge explanatory success, so it is _already_ well established.

I guess this is the real problem behind the nominalistic discussion of theory vs hypothesis.

I hope this helps, I've always wanted to thank you somehow for all the work you do classifying the evil doings of Ms Claws.

[slyjoe]

What Chupacabras said. I would emphasize the "fasifiability" of anything purporting to be a scientific theory. This is what ID/creationists have failed to do.

[blutoski]

There is another angle to consider when we say that something is a scientific theory: that there may be two or more scientific theories about a subject, but only one is considered to be the currently accepted one. Many of the older scientific theories have been supplanted by new scientific theories, so only the current ones are relevant.

An example of this is my friend who believes that relativistic models are incorrect. He believes that the universe can still be explained through a classical Newtonian cosmological model, which is certainly also a scientific model. It's just not a scientifically acceptable cosmological model because there is a better one (the relativistic model).

There are some things to consider when comparing two or more "testable" theories:

* scope - does it explain many facts, preferably in different fields
* fruitfulness - does it predict new facts, previously unthought of
* conservatism - does it require rejecting existing facts
* simplicity - does it replace several models with one

Creation Science looks appealing in terms of simplicity, but really falls down in terms of scope and fruitfulness.

The Relativistic model betters classicism in terms of scope, fruitfulness, and simplicity, but many people can't get past the challenge to some philosophical assumptions. A scientist would say that it is fairly conservative in that it actually contains most of the classical model as an approximation in the special case of low mass and low velocity, some people consider it to be not very conservative in that we have to reject assumptions about space and time being unchangeable, and mass and energy being convertable.

ETA: found a good slide show: [Criteria of Adequacy]

ETA: updated link. old link required some kind of ppt plugin;

[robinson]

Originally Posted by blutoski

ETA: found a good slide show: [Criteria of Adequacy]

http://philosophy.hku.hk/courses/200...,15,Slide%2015

HTTP Error 404 - File or directory not found.

[blutoski]

Originally Posted by slyjoe

What Chupacabras said. I would emphasize the "fasifiability" of anything purporting to be a scientific theory. This is what ID/creationists have failed to do.

Falsifiability is certainly the Popperian view regarding the "demarcation question" (meaning the demarcation between science and non-science).

Kuhn argued that a theory was scientific if the scientific community considered it to be so.

[JJM]

An important consideration is that theories are built on data; whereas, ID only has arguments (so the term theory does not apply). As one wag put it- "we have the fossils, we win!"

The ID people assert, among other things, that complex systems that don't work when a component is missing (e.g., blood clotting- think of hemophilia) could not evolve because they don't work until all the pieces are there. This is mere argument, since it could be argued that an inefficient, one-component clotting system could have evolved, stepwise (by adding components), to be more efficient. No data supporting ID, there.

As I recall, M. Behe tried to be more quantitative by calculating the odds that the blood-clotting system could have evolved by chance. His calculation used arbitrary numbers that showed it would take longer than the age of the Universe. I changed a couple of his numbers to other, reasonable values and found it would only take 30 years. No data there; just the observation that numbers (arbitrarily) chosen for the calculation can support either side.

So, two of your problems are to distinguish argument from data, and then convince the other side about that.

[Dr Adequate]

Linky.

Theory: In science, a well-substantiated explanation of some aspect of the natural world. --- US National Academy of Sciences

"Theory" means a logical, tested, well-supported explanation for a great variety of facts. --- National Center for Science Education, USA

Scientific theories, like evolution and relativity and plate tectonics, are hypotheses that have survived extensive testing and repeated verification. Scientific theories are therefore the best-substantiated statements that scientists can make to explain the organization and operation of the natural world. Thus, a scientific theory is not equal to a belief, a hunch, or an untested hypothesis. --- American Geophysical Union

A theory in science, such as the atomic theory in chemistry and the Newtonian and relativity theories in physics, is not a speculative hypothesis, but a coherent body of explanatory statements supported by evidence. --- American Intitute of Biological Science

[Spindrift]

Originally Posted by Dr Adequate

A theory in science, such as the atomic theory in chemistry and the Newtonian and relativity theories in physics, is not a speculative hypothesis, but a coherent body of explanatory statements supported by evidence. --- American Intitute of Biological Science

In layman's terms, a scientific theory is NOT a best guess as in "it's only a theory".

[fuelair]

Originally Posted by Chupacabras

Probably your concern is about scientific, instead of "theory". IMHO this is the central issue - perhaps the only issue - in ID disputes.

In that regard, for a theory to be "scientific", it must be based on evidence, and this evidence to be considered as such, must be observable and measurable. Very important: a theory has to be falsifiable.

Take gravity: we don't know what makes it work (gravitons or some sort of magnetism), but we know that objects fall to the center of Earth no matter what. In vacuum, in this planet (related to its mass), objects fall at 9.8 m/s squared ("squared" means it is not constant speed, but that it accelerates in each passing second). A rock or a feather respond equally. Since we know other planets' mass, we can put gadgets in orbit or even land a rover or two safely.

It I "drop" two objects in vacuum and they don't both fall to the center of Earth at 9.8 m/s squared, then its false, and I'd have to devise a new theory altogether.

HTH

Not a new theory - we do not have a theory of gravity - we only have a Law of Gravity. In your example, we would have to revise the Law of gravity if something did not fall toward the center of the earth at that rate (or we would have to prove that one was somehow not subject to gravity - by observation/experimentation). Laws (Scientific) state what has been observed to happen. Theories (Scientific) explain what happens. Both based on observation/experimentation.

[Shalamar]

Originally Posted by fuelair

Not a new theory - we do not have a theory of gravity - we only have a Law of Gravity. In your example, we would have to revise the Law of gravity if something did not fall toward the center of the earth at that rate (or we would have to prove that one was somehow not subject to gravity - by observation/experimentation). Laws (Scientific) state what has been observed to happen. Theories (Scientific) explain what happens. Both based on observation/experimentation.

Not true. In a nutshell, the law of gravity says that if you let go of an object, it will fall. The theory of gravity explains why it falls. Theories are more important than laws.

[fls]

I will admit that when it comes to Gravity, I've always been confused about which part is descriptive and which part is explanatory. I realize that it often gets used as the example to illustrate the difference between a Law and a Theory, but I don't understand the characteristics that distinguish the two in this case. It seems a poor example to me, but I seem to be alone in this opinion.

Linda

[fuelair]

Originally Posted by Shalamar

Not true. In a nutshell, the law of gravity says that if you let go of an object, it will fall. The theory of gravity explains why it falls. Theories are more important than laws.

And what in my statement was in any way different from that? There is no Scientific theory of gravity at this point*. There are people working on same, but there is not one - it is possible you are trying to use the outside meaning of theory, but if two objects are dropped in a vacuum on Earth and one falls toward the center of the Earth but the other does not, It is the law of gravity (which states both will at a specific acceleration rate) that will be affected). Though if a theory does later come out, it will have to take into account the change in the Law.



*a possible graviton is being looked at as well as some other ideas, but no gravitons have been identified so far. If any are, then the theory of gravity will assumably include gravitons. Rght now, again, there is no Scientific Theory of Gravity.

[rockoon]

Originally Posted by Shalamar

The theory of gravity explains why it falls.

No it doesn't.

The theory of gravity explains THAT it falls, but does not explain WHY.

You will be chasing your tail if you try to explain why. Try it.

[sol invictus]

Originally Posted by fls

I will admit that when it comes to Gravity, I've always been confused about which part is descriptive and which part is explanatory.

Can you give a better example, then? Personally, I don't see the difference between description and explanation (i.e. I don't think there is one).

Originally Posted by fuelair

There is no Scientific theory of gravity at this point*.

How interesting. So what would you call general relativity, if not a theory of gravity?

[fls]

Originally Posted by sol invictus

Can you give a better example, then? Personally, I don't see the difference between description and explanation (i.e. I don't think there is one).

The Theory of Evolution Through Natural Selection serves as an example, I think. The description of Evolution is "change over time in the heritable characteristics, or traits, of a population of organisms". The explanation for this change is Natural Selection. One can use the idea to make novel predictions (the direction the frequency of a particular mutation might take) and to tie together previously unrelated observations (the tail of the peacock and bacterial anti-biotic resistance).

Quote:

How interesting. So what would you call general relativity, if not a theory of gravity?

I realize that this wasn't directed at me, but it represents my confusion. Doesn't general relativity describe (albeit in greater detail that Newtonian Gravity) the relationship between the motion of bodies? Does it provide an explanation beyond 'geometry has physical significance'? What would you consider a novel prediction (that isn't a result of performing calculations in novel situations) or what previously unrelated observations are tied together due to general relativity?

Linda

[fuelair]

Originally Posted by sol invictus

Can you give a better example, then? Personally, I don't see the difference between description and explanation (i.e. I don't think there is one).



How interesting. So what would you call general relativity, if not a theory of gravity?

A theory of the difference of observation relative to the observer/observer's position/motion for the short part.

Description (Law): Things fall (Observation). Things move towards each other at a rate dependant on a mathmatical formula (describing that rate) based on Mass of each and distance from center of mass of each. (determined by experiment)

Neither the basic or the mathmatical Law of Gravity explains how gravity works - the Law mere says it does and tells you how to measure it.

Theory (explanation): ?

There is no current accepted theory of gravity because we do not know how or why gravity works. The fact that Einstein can discuss gravity relative to motion and it's effects on moving photons, etc. in no way explains how gravity works. The fact that scientists are looking for a potential thing called a graviton does not in any way explain gravity. If gravitons are found, or something else is found that is proven to cause gravity anmd it is tested and proven within our limits of proving to cause gravity we will have a Theory of Gravity. We do not know how/why gravity works yet, so we do not have a theory of gravity (we do know how evolution works so we have a Theory of Evolution). We know that gravity exists so we have a Law of gravity( we know evolution exists but we do not technically have or need a Law of Evolution. If someone wrote it out it would be something like : living things change to meet change in their environment or they die out.)

[fuelair]

I think the problem is the same one that creationists and IDers have - some people posting are treating theory as if the non-science definition was the same as the scientific definition. In the non-science world, a theory is defined as a conjecture (I think the crime was commited by a left handed, red haired transvestite) (I think a god exists who is perfect in every way and will always protect me ). In the world of science, a theory is not a conjecture, it is a specific tested (by many people, many times) explanation of how something works> It is NOT a guess, not even an Educated guess. It is proven to our full ability to PROVE, though changes in data can cause it to change.

[Eos of the Eons]

You need to learn the term "hypothesis" and "law" as well, and know what those are compared to a theory.

http://www.talkorigins.org/origins/postmonth/oct05.html
http://chemistry.about.com/od/chemis.../lawtheory.htm
http://www.essortment.com/all/scientificresea_rqce.htm
http://sci.waikato.ac.nz/evolution/Theories.shtml

[JJM]

Originally Posted by Chupacabras

{snip} In that regard, for a theory to be "scientific", it must be based on evidence, and this evidence to be considered as such, must be observable and measurable. Very important: a theory has to be falsifiable. {snip}

A hypothesis/theory should be observable, measurable and falsifiable in principle. Ideas are often advanced before the ability to test them.

For example, when I was a student I learned that certain aspects of chemical reactions could not be studied; yet we accepted them. In the 1980s, technology developed to the point where we could study those aspects. Were the original theories unscientific? Did new tech make them scientific? They were always in the realm of science since their study was conceivable.

A valid, scientific hypothesis may be a challenge to the experimentalist.

Invalid would-be-scientific ideas include those that are defined as undetectable. For example, "Qi is an energy that cannot be detected which influences health." If it cannot be detected, it cannot be studied scientifically.

[robinson]

This is always a fascinating topic. Web sites that confuse the terms don't really help.

Furthermore, the terms sometimes are used in different ways, depending on the branch of science being discussed.

[Eos of the Eons]

Some evidence leads to a hypothesis... if you cross a tall pea plant with a short pea plant and still get a tall pea plant, then you can hypothesize that the tall pea plant genes are dominant. You can repeat the experiments until you come up with enough evidence to put the hypothesis forward as a theory. After a while, when all others repreat and validate the experimentation, then you can accept that dominant genes exist, and which one/s in this case. You may even discover the gene or set of genes that are dominant. This makes the theory a fact.

It could happen that you find you made a mistake, and that means another hypothesis needs to be formulated and tested. Maybe the short plant had genes for tallnes, meaning it it came from a ancestors of many short and some small plants, and that the genes just came together at that one time to make a tall plant, but there is no one dominant gene or set of genes.

Science is figuring things out and coming up with why things happen. There could be any number of reasons why something happens, so you need to experiment to see which one reason is the actual cause of something happening.

There are many theories and facts within Biology, and many of these show how evolution actually works. It takes years to learn just some of things that can give you an accurate picture of what evolution is about.

Best of luck, and kudos to anyone who embarks on this learning journey in a serious way.