Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Can a theory become a fact?

  1. Apr 29, 2004 #1
    Through reading many threads in this forum and many books I understand that a good theory makes many predictions that come true during experiments. And the more predictions a theory makes that experiments agree with the more sound that theory becomes. Yet one contradictory experiment of a theory can disprove it altogether.

    My question is, will famous theories we talk about ever become factual?

    Is it a theory that the moon orbits the earth and the earth orbits the sun or is that a fact?

    If the moon orbiting the Earth is a fact, then what would have to happen in order for the Theory of Relativity to become a fact?
  2. jcsd
  3. Apr 29, 2004 #2


    User Avatar
    Science Advisor

    I don't think any theory is ever 'a fact'. There is always some (perhaps infinitisemally small) chance in principle that an experiment will disprove it. The apple might fly upward one day, who is to say it can't.

    For instance, perhaps nature has setup a timescale, such that after 13.8777777777 billion years, the laws of physics change.

    Still, I think most people will say, well there is something objective and 'factual' at the heart of it.. Its just that we can never identically know for sure if it is b/c of human ignorance.

    Newtonian physics, and other semi classical theories (like special and general relativity) have passed hundreds of thousands of experimental data points. We are nearly, but not quite, sure that they are indeed factual.

    GR for instance, is probably correct at most scales, but even today, amongst active scientists there is some fiddling room at large extra galactic scales for some modifications. But if I was a betting man, I would put my money on the tried and true.
  4. Apr 29, 2004 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    'Facts' aren't; they're just shorthand for ... what? Over in the Philosophy of Science and Mathematics sub-forum you may find some discussion of this. In particular, the way we use the 'fact' isn't at all consistent ... taking Newton, apples, and falling, which of these are 'facts'?
    - 'apples fall'
    - 'an apple fell on Newton's head'
    - 'Newton came to the realisation that gravity is universal while sitting under an apple tree and noticed the Moon in the sky'
    - 'an apple fell from my apple tree last night'

    It can seem incredibly pedantic to even pose some of these questions, let alone discuss them at great length and in all seriousness ... but some would say it goes to the heart of what science is really all about.
  5. Apr 29, 2004 #4
    "Theory" usually means "imperfect fact"--part of a hierarchy of confidence running downhill from fact, law, to theory to hypothesis to guess.

    A guess could be the first attempt to explain some phenomenon, whilst a hypothesis could be a more elaborated guess, with the math done and some predictions formulated. A theory is supposed to have several predictions fulfilled. There is some consensus that it could be factual, however as remarked before, there is always a trace of doubt. Facts are the everyday data as we observe them, directly or indirectly. Theories are elaborate ideas that explain and interpret facts. Facts don't go away when explaining theories are refuted. Then we need other theories to explain them

    Theories will probably never become as factual as Pythagoras law for instance although the universal law of Gravity seems to have it’s problems. There are most entertaining discussions about the status quo of Anthropogenic Global Warning, Evolution, the ice age, the weather forecast models. Fact, theory or hypothesis, what is correct theory, what is refuted?
  6. Apr 29, 2004 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Andre, why don't you start a thread in Philosophy of Science and Mathematics? I think it's a great topic (and I've a lot to say about it!). Given the scope - physics, GR, maths (you mentioned Pythagoras), evolution, ... - a discussion here in General Physics would be out of place (IMVHO).
  7. Apr 29, 2004 #6


    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    I have posted this before in another string, but it requires repeating here. One needs to be aware of the different usage of the word "theory" as applied in Science/Physics, and in the typical pedestrian way. In physics, the word "theory" isn't used to associate an idea that isn't tested or unverified. It is simply to distinguish the dichotomy between theoretical work and experimental work. Therefore, a theory simply means a set of ideas formulated in mathematical form that has some degree of logical derivation.

    This means that a theory doesn't "graduate" into a law or a principle. Even what we called "laws" in physics are part of a theoretical description based on this dichotomy. So names like "laws", "principles", and "theory" are actually irrelevant - they are just labels! Physicists tend to care very little about what things are called since they care more about the CONTENT of those labels. Unfortunately, this often leads to sloppiness in using such terms and people who don't know any better (and to whom labels are all they conclude from about the subject matter) latch on to those names and draw out their own deductions.

    What you need to keep in mind is that various ideas in physics tend to have a specific range of parameters and conditions in which those ideas are VALID. We do not demote Newtonian physics from "laws" to "hypothesis" just because we have discovered where it doesn't work. It is a useless exercise since the label means nothing. The knowledge of what it is and where it works are the most important thing. When we know something works, we try to test it out and find out if there are any boundaries to the validity of that idea - it is a major many of us in this field are employed. When we find those, then we can say that such-and-such theory or idea are valid, but only within so-and-so conditions. Never was there a situation where we "upgrade" a theory into "fact". Such thing hasn't happen in physics, at least.

  8. Apr 29, 2004 #7


    User Avatar

    Staff: Mentor

    Data is factual. Theories (explanations of data) are not.
  9. Apr 30, 2004 #8
    Thanks for the responses.

    To triple check I am thinking of this correctly… If I am talking to someone else about something and if they ask if what I am saying is a fact, I can respond telling them only data is a fact. Even saying something like “Our planet orbits the Sun” is a theory. But saying “our planet orbited the sun last year” is a fact…. Correct?
  10. May 1, 2004 #9
    "Our planet orbits the sun because of gravity" is closer to the theory. "Our planet will contnue to orbit the sun" is a prediction of that theory. Our planet has orbited the sun is, as you point out, a fact.
  11. May 2, 2004 #10
    It seems to me that "facts" are "certainties" by human interpretation. Certainties, of any form, can only be expressed probalistically, so in a sense nothing is certain but a great deal can be considered 99.9% certain, or factual, but in some cases certainty can be 100%.

    For example, you and I exist. I am 100% certain of my current existance, therfore I consider it a fact.
    On the same token, I am certain that I will die someday. But, I am not 100% certain of that, instead perhaps 99.9% because who knows what might happen, medically and technologically within my lifespan. Even still, I am fairly certain that I will die at some point.

    In short, the only certainty I perceive is the "now", and aspects of my past.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook