A theory is a rational type of abstract thinking about a phenomenon, or the results of such thinking. The process of contemplative and rational thinking is often associated with such processes as observational study or research. Theories may either be scientific or other than scientific (or scientific to less extent). Depending on the context, the results might, for example, include generalized explanations of how nature works. The word has its roots in ancient Greek, but in modern use it has taken on several related meanings.
In modern science, the term "theory" refers to scientific theories, a well-confirmed type of explanation of nature, made in a way consistent with scientific method, and fulfilling the criteria required by modern science. Such theories are described in such a way that scientific tests should be able to provide empirical support for it, or empirical contradiction ("falsify") of it. Scientific theories are the most reliable, rigorous, and comprehensive form of scientific knowledge, in contrast to more common uses of the word "theory" that imply that something is unproven or speculative (which in formal terms is better characterized by the word hypothesis). Scientific theories are distinguished from hypotheses, which are individual empirically testable conjectures, and from scientific laws, which are descriptive accounts of the way nature behaves under certain conditions.
Theories guide the enterprise of finding facts rather than of reaching goals, and are neutral concerning alternatives among values. A theory can be a body of knowledge, which may or may not be associated with particular explanatory models. To theorize is to develop this body of knowledge.The word theory or "in theory" is sometimes used erroneously by people to explain something which they individually did not experience or test before. In those instances, semantically, it is being substituted for another concept, a hypothesis. Instead of using the word "hypothetically", it is replaced by a phrase: "in theory". In some instances the theory's credibility could be contested by calling it "just a theory" (implying that the idea has not even been tested). Hence, that word "theory" is very often contrasted to "practice" (from Greek praxis, πρᾶξις) a Greek term for doing, which is opposed to theory. A "classical example" of the distinction between "theoretical" and "practical" uses the discipline of medicine: medical theory involves trying to understand the causes and nature of health and sickness, while the practical side of medicine is trying to make people healthy. These two things are related but can be independent, because it is possible to research health and sickness without curing specific patients, and it is possible to cure a patient without knowing how the cure worked.
Hi guys!
My question is about the diffusion coefficient of the mixture of gases. Consider two gases in thermal equilibrium (Maxwell velocity distribution) having different densities n1 and n2. Let's suppose that the molecules are rigid spheres with diameters d1 and d2 and masses M and m...
I've always read that these two theories are incompatible, and how General Relativity works for large scales while Quantum Theory represent reality in extra-small cases.
So my question is where is the limit where General relativity ceases to exist and Quantum Theory gives a better portrait of...
Homework Statement
Homework Equations
Reduce the matrix to reduced matrix by removing 1 row completely
Number of trees = determinant of [ Ar times ArT ]
The Attempt at a Solution
I removed 4th row to get Ar(reduced matrix)
Then I did Ar times Ar (transpose)
And found it's determinant but I...
What does it means for a physical theory to have hamiltonian, if it is formulated in lagrangian form? Why doesn't someone just apply the lagrangian transformation to the theory, and therefore its hamiltonian is automatically gotten?
Greg Bernhardt submitted a new PF Insights post
Mathematical Quantum Field Theory - Reduced Phase Space
Continue reading the Original PF Insights Post.
Quantum mechanics does a good job in describing the hydrogen atom. Are there any views either mathematically or conceptually in describing the hydrogen atom?
Homework Statement
In a vessel is a 5 cent coin and two 1-cent coins. If someone takes up two randomly chosen of these coins, and we let X be the total value of the coins taken, what is the probability function for X?
Homework Equations
I know that X has a value {2,6}
The Attempt at a...
Homework Statement
Spaceship A, traveling past us at 0.7c, sends a message capsule to spaceship B, which is in front of A and is traveling in the same direction as A at 0.8c relative to us. The capsule travels at 0.9c relative to us. A clock that measures the proper time between the sending and...
hi, when we talk about heavy meson, its momenta is defined as label and residual momenta. if the second quark's mass is almost comparable to heavy quark, then would the scaly of residual momenta be changed? I mean can it be lambda instead of lamda square in case of comparable mass?
This is a bit of a philosophical/conceptual question. I've done tons of reading on it, of course, but haven't found anything that makes me go 'ah ha'!
I am working steadily through the mathematical formalism of differential geometry, but am struggling to grasp how the things we say in this...
why is the general theory of relativity is so complicated
i feel that it's very simple no thing hard in it
there is a whole website to make people understand it i read the articles and i didn't found any thing complicated
knowing the i am 13 so it should be very hard to understand
Greetings,
I'm not a physicist but I have a general interest in physics and cosmology. I was
watching the following video where they were talking about how an electron behaves like
a wave and its position is not know until it is measured. Then it was explained how the
probability of the...
I would like to know where one may operate with tensor quantities in quantum field theory: Minkowski tensors, spinors, effective lagrangians (for example sigma models or models with four quark interaction), gamma matrices, Grassmann algebra, Lie algebra, fermion determinants and et cetera.
I...
I have read about general relativity, quantum mechanics, and physics is general, but I'm looking for a book that goes a little bit more in depth with the math behind the theories (I understand a lot of those equations are going to be complicated). I'm in 10th grade so I'm doing Algebra II this...
I was thinking about the immediate ways that physicists had for checking the validity of Newton's theory of gravitation in the time Newton published it. An obvious way would be to check if it predicts what is stated by Kepler's laws. Does anyone know if this was made? Do you know of other tests...
Hi everyone,
I am working on a second bachelor's degree in Computer Science, and am hoping to enter a Phd program in fall of 2019. Recently, I have taken an interest in Chaos Theory and was wondering if it is possible to do research in the field in the Computer Science department, or if it is...
The Scientific Method says that if a theory disagrees with observations, it has been falsified (according to Karl Popper). String theory predicts that spacetime is 10-D, but it is observed to be 4-D. This is a wrong prediction by the theory. So string theory is falsified.
String theorists then...
bosonic string theory requires 26 dimensions
superstring theory requires 10, 9 spatial 1 dimension of time
Witten has researched twistor string theory
has there been any serious research with (super) string theory written on 4 complex -valued dimensions of spacetime?
the additional dimensions...
"... quantum mechanics isn’t a complete physical theory in its own right, but rather a framework for the construction of physical theories."
I found this in Michael Nielsen's blog and elsewhere. I am perplexed. In what fundamental way does it differ from Newtonian Mechanics (Theory) in not...
I am reading "Introduction to Set Theory" (Third Edition, Revised and Expanded) by Karel Hrbacek and Thomas Jech (H&J) ... ...
I am currently focused on Chapter 1: Sets and, in particular on Section 3: The Axioms where Hrbacek and Jech set up an axiomatic systems (which they do NOT call ZFC ...
Hi pf,
I was wondering about a bubble moving with constant velocity in a liquid, and how the motion affects the mass transfer. Since the viscosity of the gas is significantly smaller than the viscosity of the liquid, the condition ## \tau_{gas} = \tau_{liquid} ## tells me that
$$ \mu_{gas} (...
What do MHB members think are the best books at an undergraduate or senior undergraduate level on set theory ...
Further what are the best books on set theory at a graduate level ... ...
Peter
Hi! Sorry for my bad English!
I don't know much of physics, I know some experiments that show that relativity is real, quantum entanglement, particle and wave duality and so on...
So, the only theory that explain all of it mathematically is M theory and the strings, but we can never test it to...
Hey,
Theory: The voltage of a thundercloud is too low to ionize air particles and to produce a thunder.
Particles of cosmic radiation are the trigger.
I calculated whether the voltage of a thundercloud is enough to ionize air particles but the voltage was always to low. So I wanted to know...
Homework Statement
I have the following definition of the space-time coordinates
Homework Equations
Working in a certain gauge we can also do:
From which we can find:
Where ##N_{lc} ## sums over the transverse oscillation modes only.
The Attempt at a Solution
[/B]
MY QUESTION:
I...
How is chaos incorporated into quantum gravity theories, or in theories that incorporate all the known 4 interactions?
I don't believe I've seen a thread where chaos theory is discussed in relation to superstring theories or LQG.
I've seen some papers and dissertations on quantum chaos and...
I understand that in group theory, a group consists of a set and a binary operation for the elements in the set, and of course all the group axioms. But if we move away from set theory into category theory, is a group defined on a category?
https://www.ma.utexas.edu/users/dafr/OldTQFTLectures.pdf
I'm reading the paper linked above (page 10) and have a simple question about notation and another that's more of a sanity check. Given a space ##Y## and a spacetime ##X## the author talks about the associated Quantum Hilbert Spaces...
I am retired from a major railroad co. where I worked on electronic weighing equipment. I have an associate of applied science degree from a local university. I have a basic understanding of dc and ac electricity but the explanation I recently read on this forum was the easiest to understand...
I asked my question in overflow, so far with no answers.
Perhaps here, I'll get an answer.
https://mathoverflow.net/questions/282048/a-lemma-on-convex-domain-which-is-a-lipschitz-domain
[admin edit: Below is the actual question posted, so our community doesn't have to follow multiple links:]...
Why there must be a way of including gravity into a quantum theory? What leads scientists to believe that ultimately all the interactions must be subjected to quantisation?
Would that be because we describe all other interactions in quantum theory and so we must include gravity on this...
latest paper
Ghirardi-Rimini-Weber model with massive flashes
Antoine Tilloy
(Submitted on 12 Sep 2017)
We introduce a modification of the Ghirardi-Rimini-Weber (GRW) model in which the flashes (or collapse space-time events) source a classical gravitational field. The resulting semi-classical...
Homework Statement
Anyone know anything about queueing theory? would really appreciate some help.
the question goes as follows:
The annual S&C Christmas sale is so popular that it is necessary to limit the number of customers who can be inside the store simultaneously; this limit is set at 60...
So Heisenberg's Uncertainty says that we can't know both the position and the velocity of a particle accurately, because measuring one will disturb the particle enough that it's no longer possible to accurately measure the other as it was. So one or the other has to remain unknown to us.
This...
I need good books on Molecular Orbital Theory. The book(s) should have the basics, and the level should not be less than graduation.
I have Quantum mechanics books, but they don't throw any light on this. My course books are rubbish, only mentioning the name of the theory and some illogical...
This question is more about the maths than the physics.
So I am reading the textbook by Bergersen and Plischke, and they get the following:
$$m= \tanh [ \beta (qJm+h)]$$
where ##m## is the magnetization, ##q## is the number of nearest neighbours of site ##0##, ##J## and ##h##are the...