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Do we study the true nature of the universe or reality or just create a model(mathematical) to get approximation close enough to our use? whether they have to do any thing with reality or not. I have few statements that i have seen from other answers which confuses me more. i do not know whether i have wrong concept of physics in my mind or not. please clarify this concept in intuitive way and use simple worlds that a high school student can understand and below are those statements.

  1. Don't be surprised that physics has a lot of definitions that are circular. Ultimately, we are just describing the universe.

    Work and energy have been defined in a certain way in newtonian physics to explain a kinematic model of reality. This is a model, not reality - you will find no such thing in reality. However, in many scenarios, it is close enough to reality to be useful. and

  2. Physics is limited in offering only mathematical descriptions of the universe. The models which are created are dependent on the math and offer a sort of intuition behind the phenomena

Qmechanic
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Remy
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    What does "true nature" mean? – probably_someone Apr 11 '18 at 07:27
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    A former manager used to say "your perception is your reality." So all physics can try to do is create a consistent and complete model. To prove that the model is really "the truth" is impossible. For example physics can't explain dark matter or dark energy. So the model must be incomplete. – MaxW Apr 11 '18 at 07:29
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    How would you describe your house/apartment? – Hot Licks Apr 11 '18 at 12:23

2 Answers2

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Any description of anything ever is nothing more than a model. Describing an event of this World in words, sign language, pictures or mathematics can all be considered different types of modeling methods. Each type of model has different benefits and drawbacks and are usable for different purposes.

The goal with all such methods is to be as close to the actual reality as possible. But although they may be very accurate in certain cases, they will never be more than models.

When you make a model and don't have all data, then you might use a method for filling up missing data points. Maybe by recognizing a pattern in the already known data and extrapolate this pattern into the unknown territory.

Your brain does this constantly, filling up the space in the visual model acquired from your eye sight that your eyes actually haven't seen or aren't focusing on or things that don't make sense. You have blind spots that you never notice (they are not "black" because the brain fills them out) and largely unfocused areas along the peripheral vision that blend in without thinking, and you easily get tricked by optical illusions because your brain tries to make something that looks odd make sense.

In physics a mathematical model simply describes a specific phenomenon, such as Newton's law $\sum F=ma$. You may measure the acceleration at many forces and thereby verify this law for these data points. But what about all the other forces there you haven't measured for? When discovering that there is a pattern (that acceleration turns out to be proportional to force) in all your many measurements, then you start trusting that this pattern also is the case in all the cases that you haven't measured. And this is how a physicist will use a mathematical model: to understand what is going on where an exact measurement has not been or cannot be done.

Steeven
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  • when we say that point particles which make axis of rotation does not rotate in reality there is nothing like point particles so then why we are using point particles to explain things which does not exist in reality? – Remy Apr 11 '18 at 07:45
  • Who knows if point particles don't exist? But then again, how do you define a particle in that respect? – Yuzuriha Inori Apr 11 '18 at 08:11
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    Just a nitpick: I wouldn't say our brain "gets tricked", I would say this is how it works. If all representation is illusion, we do not really "fall for illusion", because there is nowhere from falling from. – Stéphane Rollandin Apr 11 '18 at 08:31
  • @YuzurihaInori if point particle exist then hoorah if not then so called good tool for approximation i think this science am i right? – Remy Apr 11 '18 at 08:41
  • Yes, this is science. Making models, checking them against experiments, refining the models and iterating from the second step, again and again, is what is science! – Yuzuriha Inori Apr 11 '18 at 08:43
  • @Remy there is also a different justification.for using point particles. If you have a 1/r^2 force law and a spherical particle you can show it behaves like a point particle. – lalala Apr 11 '18 at 10:46
  • @Remy The reason for point particles in models is just to make things simple. Imagine making a 3D mode of a blue whale and a beetle. At such scale, the beetle fills as good as nothing in comparison. It's size has no practical influence. So instead of spending computer modelling power, time and effort on modelling something practically useless, we can just model it as a point. A point particle is just an object that has been simplified because it's size is not important. If you use Newton's linear laws, then you can ... – Steeven Apr 11 '18 at 12:14
  • @Remy ... actually simplify a large box as a point particle, because it's size is not important for these laws. But when doing rotational mechanics for instance, the size matters (it matters where different forces act and where an object is hinged etc.) so there you would never simply the box as a point-particle. – Steeven Apr 11 '18 at 12:14
  • @Steeven please explain when a high school teacher says that a rotating body has (for example a ball) an axis of rotation and on that axis no particle is rotating and all the particles other than those are rotating around the axis .about which particles is he talking? just assumptions or are there particles in reality with o dimensions then how a physical thing with o dimensions is possible except in abstract discipline like math. – Remy Apr 11 '18 at 15:21
  • @Remy As I tried to explain, point particles of 0 dimensions are only simplifications of objects that are in reality not 0 dimensional. Yes, it is an abstract concept that simplifies our way of modeling the world. Point particles don't actually exist in this world (as far as I know). – Steeven Apr 11 '18 at 17:24
  • @Remy I am not fully clear on your rotation example. Would you mind clarifying that? – Steeven Apr 11 '18 at 17:25
  • @Steeven i am talking about simple rotational motion and the definition the teacher gave of axis of rotation is "locus of the center of the circles around which all the particles of the body or a system of particles rotate but particle which make the axis does not rotate" – Remy Apr 12 '18 at 04:55
  • Okay @Remy, I now understand the situation described by the teacher. If a point is infinitely small and has no size then it doesn't really make sense to talk about it rotating - what does rotation even mean for such a particle? Or maybe a better argument is: Of what use is it to talk about it rotating? I guess this is what your teacher was trying to get to. – Steeven Apr 12 '18 at 08:02
  • @Steeven But he (Teacher) used word particles are there particles possible with no extent at all or in other words 0 dimensional. in math it is ok because math is abstract universe but we are talking about physical universe if 0+0+0........+0=0 then how can a system or object which is consist of 0 dimentional points particles has any spatial extent. in concrete sesnse Does not make sense in abstract mathematical universe it is ok but in reality a big ? – Remy Apr 13 '18 at 14:01
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The answer of Steeven describes how a part of physicists ( usually experimentalists) view what physics theories mean : they are mathematical models with extra laws and postulates chosen so that the mathematical solutions fit the present data and successfully predict new phenomena. For example the Higgs was predicted from the theory of the standard model many years ago, and was recently discovered. This is considered a validation of a physics theoretical model.

I have found though that people who are theoretically inclined tend to be platonists: Plato posited ideals, as molds which nature fulfilled. I have observed that people who are very good in manipulating mathematics tend to believe that it is mathematics which creates reality. In this sense the ultimate reality is mathematics. This of course is a philosophical debate, not a physics one.

anna v
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