What is Reality: Definition and 432 Discussions

Reality is the sum or aggregate of all that is real or existent within a system, as opposed to that which is only imaginary. The term is also used to refer to the ontological status of things, indicating their existence. In physical terms, reality is the totality of a system, known and unknown. Philosophical questions about the nature of reality or existence or being are considered under the rubric of ontology, which is a major branch of metaphysics in the Western philosophical tradition. Ontological questions also feature in diverse branches of philosophy, including the philosophy of science, philosophy of religion, philosophy of mathematics, and philosophical logic. These include questions about whether only physical objects are real (i.e., Physicalism), whether reality is fundamentally immaterial (e.g., Idealism), whether hypothetical unobservable entities posited by scientific theories exist, whether God exists, whether numbers and other abstract objects exist, and whether possible worlds exist.

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  1. T

    I Simulated Reality: Proving Our Universe Is Real?

    As you might know, the simulated reality idea says that our universe is a simulation by some higher order beings. Some scientists and philosophers taken it quite seriously while others dismissed it. Is there anyway to prove whether our universe is simulated or not for sure? And will our...
  2. C

    Applied Book Recommendation: Math textbooks for physics that tie things back to reality

    Sorry if this is the wrong thread but subject wise it seemed the most appropriate. Are there any books available that take a deep dive into the heady mathematics you guys use here BUT that take the time to tie things back to reality? And I'm talking about something for interested laymen like...
  3. M

    I How do I show a skeptic that atoms/molecules actually exist?

    This might be a stupid question so please bear with me. I am having a debate with a friend of mine over the Internet. It is about science. His argument is that although science works (that is the technology part), science cannot actually tell anything about "reality". He sites for example...
  4. facenian

    I Is Superdeterminism a Plausible Explanation for Quantum Mechanics?

    Hello, I would like to hear some comments on this: Recently a paper has been published(Sánchez-Kuntz, N. & Nahmad-Achar, E. Found Phys (2018) 48: 27. https://doi.org/10.1007/s10701-017-0126-z) claiming tha QM has a local realist interpretaion. In this paper it is asserted that: "The wave nature...
  5. hideelo

    A Reality conditions on representations of classical groups

    I'm reading "Division Algebras and Quantum Theory" by John Baez https://arxiv.org/abs/1101.5690 In the last paragraph of section 5 (Applications) he says the following "SU(2) is not the only compact Lie group with the property that all its irreducible continuous unitary representations on...
  6. Luigi Fortunati

    Appearence and reality -- centripetal and centrifugal forces....

    For each action there is an equal and opposite reaction (third principle), and no one would ever think to say that the action is "real" and the reaction is "apparent". Also the centripetal force is an "action" to which (as it happens for all the actions) it corresponds *always* an equal and...
  7. E

    I Railgun: Problems with reality check

    So I was doing some calculations last night on railguns for fun, and I got some very surprising results which seams like they must be wrong. The calculations are simple and I must have overlooked something. So we all know that F = B * I * L when all are orthogonal, a capacitor discharge is I =...
  8. hugo_faurand

    B What is the reality of the scalar product?

    Hi everyone ! I would like to know the real meaning of scalar product. So, I know scalar product is defined as : ||a||.||b||.cos(a;b) = k But what k is ? (Sorry for my english, I am french). Regards :)
  9. F

    Proof of irrationality of sqrt2 in Penroses Road to Reality

    Hello Everybody, I hope that I've picked the right sub-forum for my question. The problem is as follows: I understand perfectly well the proof by contradiction of the irrationality of the square root of 2, where we prove that if we assume that it is rational, then the integers of which the...
  10. G

    Lens engineering for virtual reality

    What type of lens/prism would be needed to allow a image sensor to see 180 degrees, so the sensor could see a hemisphere. It doesn't matter if the input is distorted. I thought that a glass pyramid with a square base might work.
  11. B

    Virtual Reality Headset Resolutions

    Before I tried VR headset. I thought it was just looking at screen closeup. but no.. it's more than that. I mean.. it's like you are really immersed in the surrounding and there is 3D effect I haven't foreseen. Most of those who haven't tried it wouldn't appreciate the experience. To those who...
  12. M

    What are the Benefits of a Holistic Approach in Science?

    Hi, my Name is Markus and I'm from Germany, I have more a lingustic & IT background with basics in physics from school times (some years ago, I have to say). I have a couple of more holistic questions, hope that is ok, please let me know, Have a great day!
  13. E

    I Relativism & Reality: Finding Length in Space

    Do you regard relativistic effects to be physically real or just apparent (kind of like optical illusion caused by distorted information one is receiving)? To prevent endless entanglement in "define physically real" arguments imagine this: two spaceships moving inertially relative to each...
  14. T

    I Does reality really exist when not measured?

    In 2015, the Australian National University conducted an experiment that showed that reality does not exist when not measured. But how is it that things exists on the macroscopic scale even when they are not measured? http://www.anu.edu.au/news/all-news/experiment-confirms-quantum-theory-weirdness
  15. MattRob

    B WSU Shows Negative Mass Exists: Implications for Faster-Than-Light Travel?

    While the title may seem to overblow it, showing that negative mass exists may be just that big. After all, as I understand, the primary obstacle to the reality of the Alcubierre Drive or Krasnikov Tubes is the negative energy density requirements. This of course violates certain energy...
  16. D

    B Are Events in Reality Defined by Causes?

    Are there any events in reality, or is everything a continuous process? If events exist, do they have precise beginnings and ends? When a photon hits an electron, is that an event? Does that "event" have a beginning and an end? Could the big bang be considered the only event? Can there be any...
  17. T

    I How does observation affect reality

    In quantum physics, one can change a system just by observing it, such as wave function collapse and quantum Zeno effect. I don't quite get how observation affects them, unless we are interacting with them when observing them.
  18. chasrob

    Reality check on superhero power

    My story has a Superman analogue as the protagonist. His talents include the basic “flying brick” goodies, but no other powers. Early in the story, soon after he was “transformed”, he’s flying in for a landing in his current, drug-ridden, residential neighborhood at night. He happens to look...
  19. J

    Courses Intro to Philosophy: Knowledge and Reality or Philosophy: Practical Logic?

    Which course do you guys think would be more interesting/helpful for a physics major? They are both 100 level, Intro consists of two lectures and a seminar a week, and Practical Logic consists of a three hour lecture once a week.
  20. victor94

    I Exploring the EPR Paradox: What Does "Simultaneous Reality" Mean?

    I'm reading the paper of the EPR paradox and I'm confused in the meaning of this: "The elements of the physical reality cannot be determined by a priori philosophical considerations, but must be found by an appeal to results of experiments and measurements......when the operators corresponding...
  21. bohm2

    A Experimental tests on the reality of the quantum state

    Does this mean that we will one day have an answer to the old age question on the ontology of the wave function: Towards optimal experimental tests on the reality of the quantum state http://iopscience.iop.org/article/10.1088/1367-2630/aa54ab
  22. N

    A Hologram theory and quantum physics = existential crisis

    Hello, here there are 2 things (one about hologramic universe and the other about a quantum physics test similar to the slit lamp. The first one is about the Bohm and Pibram as well as one about Alain Aspect 1982 study: articles about their theories...
  23. J

    Visualizing a 3D Configurator in Reality

    Hi, i want visualize a 3D configurator like this in reality. I have print the configurator in 3D but the result was not very good. How I can visualize the 3D configurator in reality in best. Thanks.
  24. BillTre

    Cool Optical Illusion and Our Created Reality

    I found this optical illusion today on the internet. This posting is accompanied by an explanation of how it works, that invokes lateral inhibition among neurons in the visual system. There is another version of this available on the internet where they show two versions. one version has red...
  25. M

    I Psi-epistemic arguments against reality of quantum states

    I was just reading a paper <predatory publisher reference deleted> There is an argument (originally by Spekkens), in Section 2.1, that is supposed to be against psi-ontic interpretations. As I understand it, it's that if someone hands you a particle in state x+ or y+ you cannot tell the...
  26. Cobalt101

    I Underlying reality re deBroglie equation

    While the mathematics and the experimental results of de Broglie's equation are clear, what is the best understood explanation as to what is happening in underlying reality of why wavelength varies (inversely) with momentum for all energy and matter ?
  27. Clever Penguin

    I Quantum Mechanics is not a description of reality?

    Consider a cat in a box in a room. The box also contains some radioactive isotope. A geiger counter detects if the atom decays, and if it does, it sends a signal to some sort of computer, which causes a hammer to fall and smash open a bottle of poisonous gas. So, if the atom decays, the cat is...
  28. J

    B Why did Bohr & Company hold quantum reality to be indeterminate?

    QM declares reality to be inherently indeterminate. Another hypothesis is that it is in fact determinate, but due to measurement uncertainty appears to be indeterminate. Why did Bohr, Heisenberg & Co adopt the first hypothesis and reject the equally valid second, when the two are experimentally...
  29. Gosutag

    I The Road to Reality by Roger Penrose

    Just started reading this book as an introduction to physics with a background of electrical engineering. It is absolutely fascinating and being new to the forum I'd appreciate it if anyone had any suggestions for further general learning. Thank you all for inspiring me to learn more physics...
  30. Etienne

    I How can I prove this from Roger Penrose's Road to Reality?

    Hi, I've been reading Roger Penrose's Road to Reality during my free time, and I am trying to do all the proofs I possibly can, although I am quickly reaching my limit. Would somebody help me prove this? h(x)=0 if x ≤ 0 h(x) = e-1/x if x > 0 Thank you in advance :)
  31. G

    Reality check on SF action scenes

    People are free to post here their ideas and watched scenes involving SF actions, whether they can be realistic or not.
  32. Jackie CH Liu

    A A Quantum Theory of Spacetime, the Physical Reality of Cross

    I just want to share my paper I recently wrote. I am trying to submit for publication: [Reference to unpublished paper deleted]
  33. newrd

    B Who was the observer for the first 10 billion years?

    If reality requires an observer, and life on Earth is only 3.8 billion years old- yet the universe is 13.8 billion years old, who was the observer for the first 10 billion years?
  34. C

    I Operational Reality of E field? (Bridgman)

    I'm reading The Logic of Modern Physics by P.W. Bridgman (1927). He states an operational definition of reality: something is a "good construct" if it has a one to one correspondence with a physical situation defined by observations, but it isn't "real" until it has multiple...
  35. C

    The Internal Consistency of Collapsing Realities

    Currently I am working on a manga/comic of mine which imvolves science, especially stuff related to quantum mechanics. The theme of my manga is based on the 'collapsing of realities'...i.e, realities from different timescales would collapse at one place and try to exist at once, which would...
  36. raphalbatros

    B How is it that mathematics describe reality so well?

    Humans created that tool, that language, that consists of axioms and their implications. Mathematics do a good job of communicating the behavior of physical phenomena. In some instances, pure mathematical areas have been found to describe some aspect of reality, only years after having been...
  37. B

    Will Brian Greene make a "The Hidden Reality" documentary?

    Brian Greene made excellent documentaries on his first two books: The Elegant Universe and The Fabric of the Cosmos. Has Brian Greene ever said whether or not he will make a documentary out of The Hidden Reality? I googled it and didn't find anything saying yay or nay.
  38. CrackerMcGinger

    How would virtual reality devices really work?

    I have thought about virtual reality headsets and other futuristic devices for a month now, but now I it has peaked my interest enough to ask about it on the forum. My idea for a safe virtual reality headset would be a device that is able to use a method similar to that of dreams. I thought of...
  39. Toxis

    I VR/AR big bang model (Virtual Reality Simulation)

    Hi, I have a silly question, Could one, in theory make a accurate model of the life of our universe that one could look at from within. Let's say I put on my VR/AR goggles, 'there' Iam elevated from the earth, then I remain static, and the time begins to rewind. At some point I maybe hear...
  40. 9

    Automotive Understanding Gear Ratios: Inputs vs Reality

    The gear ratio is the ratio of angular displacement, angular velocity, angular acceleration, torque etc of the input with respect to output. However, I would like to know that which of these variables will be scaled exactly to the gear ratio in reality, as there might be some friction in the...
  41. atyy

    I Wilsonian viewpoint and wave function reality

    In the Wilsonian viewpoint, quantum electrodynamics is an effective theory, where the low energy predictions are obtained by coarse graining eg. some form of lattice QED where the lattice is taken very finely. In the Copenhagen interpretation, we are agnostic as to whether the wave function is...
  42. Imran Makhdoom

    B Quantum mechanics and reality of matter

    Hi Do Quantum Mechanics negates the reality of matter and proves un-reality of matter ?
  43. DrClaude

    Quantum state vector and physical state

    Interesting new work on the link between quantum state vectors are physical states: Can different quantum state vectors correspond to the same physical state? An experimental test Daniel Nigg et al 2016 New J. Phys. 18 013007 Abstract A century after the development of quantum theory, the...
  44. adfreeman

    Mind over matter reality or myth?

    Hi, I’m new to the forum and I would like to ask some questions. I’m not a physicist –for some reason that I’ll always regret I chose Business Studies- and my knowledge of physics is limited to high school, physics books and documentaries; which I must have watched them all by now. Anyway, for...
  45. N

    I Why teleportation, time travel, virtual reality haven't happened yet?

    (I apologize beforehand if I'm asking such an 'amateur' question , I admit that I'm not a physics student / physicist nor scientist / science student ,.. but , as just a 'normal ordinary' person, at least I am very interested in these things ,. and how I deeply wish Humanity / Mankind can 'leap...
  46. DoobleD

    B Is spacetime just a mathematical trick or is it the actual physical reality?

    While learning about SR, I encountered the famous Minkowski spacetime. At first I thought it was just a useful mathematical trick, with no particular physical meaning. But reading more about it, it seems that this notion of spacetime is often (always?) regarded as the actual physical reality...
  47. N

    I How the standard spacetime model relates to reality

    As I understand it, the standard spacetime model is a 4-dimensional geometric object, and that my personal history is just a particular curve in the model. Reality as I experience it though is that I move through time, and thus I have the concept of the present in which "now" corresponds to the...
  48. K

    Did Lord Kelvin Say "If You Can't Measure It, It Isn't Real!"?

    The other day, in conversation, I attributed the dictum, "If you can't measure it, it isn't real!" to Lord Kelvin. However, when I chanced to look it up in Wiki, I could find no confirmation of this attribution. Was I mistaken? Did Lord Kelvin ever say anything to this effect? If not, is...
  49. Q

    B Does Observation Create Reality in Quantum Physics?

    According to quantum physics, things don't exist until being observed/measured. If this is the case why can we predict the same reality being generated? For example, if the moon doesn't exist when it is not looked at, then why does the moon keep appearing when we do look at it. Is "reality"...
  50. Rectifier

    Bode plot for first order high pass (RL) - reality vs theory

    Hey there! So I have this circuit: with R= 1kOhm and L=10mH and for some reason the theoretical and real values differ drasticly for lower frequencies Brown lines are representing the asymptotic and approximation lines. Blue lines are connecting my measured values. Amplitude is the amplitude...
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