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. A

    I Simultaneity and Reality: Construct a thought experiment similar to this one described by Einstein

    I want to construct an experiment similar to that described by Einstein in his thought experiment: https://en.wikisource.org/wiki/Relativity:_The_Special_and_General_Theory/Part_I#Section_9_-_The_Relativity_of_Simultaneity How would I design it to ensure the light from the flashes at the back...
  2. Kinker

    I Impossible probability between theoretical possibility and reality

    Boltzmann's brain, entropy reduction, Poincaré's recursion theorem, the probability of oxygen molecules in a room gathering in one place, the probability of quantum tunneling of macroscopic objects, etc. are theoretically possible. But the probability of these events is very low. Additionally...
  3. P

    I Quantum Mechanics as a Probabilistic forecast of reality

    Is Quantum Mechanics a Probabilistic Forecast of nature?Someone I know told me their interpretation of QM is that QM only a probabilistic forecast of systems like electrons around atoms. I would like someone to analyse this interpretation and say if its valid or not. According to this person we...
  4. S

    A Extended Wigner’s Friend Scenario and the existence of the reality

    https://backreaction.blogspot.com/2022/02/has-quantum-mechanics-proved-that.html It is unclear for me, why from these experiments the tabloids made the conclusion that "the reality does not exist"? Does the essence of this experiment lie in the fact that it confirmed the Wigner's friend...
  5. D

    Could reality be half simulated?

    or even a percentage of it. i know this is more of a philosophy question but could it be like a holodeck, where the gravity, floor and walls are real but the rest of it is a simulation? (this is a metaphor of course.) so space and gravity as an example are a simulation but consciousness and...
  6. nomadreid

    "Heuristics" for Casimir: how close to reality do they have to be?

    According to the dictionary, a "heuristic" is a tool to allow someone to figure out on her own the full explanation. If I say that explanation A is a heuristic for a complicated concept B, shouldn't B be at least a close, even if incorrect, explanation? Specifically, I have read (sorry about...
  7. D

    I "No objective reality" in quantum mechanics?

    As per title and the TL;DR, I'm curious if there could be some truth in these statements of the headlines I had read recently or are they just sensationalist fluff. Personally, I find these statements very hard to believe. In fact, impossible to believe. But I'm not a QM expert, not even an...
  8. Q

    Real Virtual Reality: Join the Discussion

    Does anyone know of any groups who discuss this from a scientific or even experimental standpoint? Yes I am talking about a Matrix type virtual world. I have many ideas and with the state of the world in the way it is, from my perspective - could perhaps be a very important thing to consider.
  9. Giulio Prisco

    A Can Gödel's Theorem Inform Our Understanding of Physical Reality?

    What does Gödel’s theorem say about physical reality? Does Gödel’s theorem imply that no finite mathematical model can capture physical reality? Does the nondeterminism found in quantum and chaos physics - it’s impossible to predict (prove) the future from the present and the laws of physics -...
  10. T

    Simulation vs Reality: Wind Power System

    Here is a paper on a wind power system and the paper is based on simulation. i just want to know if something in real is built based on the simulation, how close that will be in reality in comparison to the simulation results. And anybody here has experience in building things based on...
  11. W

    I Uncertainty = our ignorance or intrinsic to reality?

    I realize that it is impossible to know both the speed and position of a particle because of the uncertainty principle. I also know that this is because if you send a photon at the particle to detect its position you alter its momentum. But does that mean that when you measure position it has no...
  12. ShayanJ

    Exploring the Reality of Kids with Violent Temptations

    Summary:: Curious whether this story about this kid could be real, and if yes, is there any explanations? I just came across this reddit thread. I know, it could be fake. But I've seen a similar story before about a little girl who openly talked about wanting to kill her adoptive parents and...
  13. Lynch101

    I The Probability Distribution and 'Elements of Reality'

    The below comment by @vanhees71 is an interesting one and I would be interested in exploring its implications. I am inclined to think that we can draw certain inferences about nature based on how we interpret the probability function and what it tells us about the elements of reality of the...
  14. Giulio Prisco

    A Fundamental reality: Hilbert space

    What do you guys think of this soberly elegant proposal by Sean Carroll? Reality as a Vector in Hilbert Space Fundamental reality lives in Hilbert space and everything else (space, fields, particles...) is emergent. Seems to me a step in the right conceptual direction.
  15. Emmanuel Pil

    A Request for a review of a paper on consciousness creating reality.

    The paper I refer to, I found on the Big Think blog titled "Is human consciousness creating reality? And here is the actual link to the paper. Unfortunately, this paper is too technical for me, hence the request for a review for such a big claim.
  16. porton

    B A in A's reality, B in A's reality, A in B's reality in ....

    I read somewhere in Quanta magazine that (if I understood correctly): When A and B watch C, then C in A's reality may be different than C in B's reality (as B is seen by A?) What if A and B watch each other? We could make chain: A in A's reality, B in A's reality, A in B's reality in A's...
  17. iosman001

    Other The Road to Reality by Penrose?

    Hello, i live in the US and decided to get this book off of amazon i was wondering if anyone has read, or atleast skimmed (its pretty big) through it and would mind telling me if its a good buy(although if it isnt, its a little late now :tongue2:). also, I am pretty new to most of the...
  18. H

    I A quick question regarding the application of Aleph numbers to reality

    Hi everyone, I have a quick question about Aleph numbers. Are they even possible? By containing infinity to a finite set, isn’t that essentially disproving the infinity in the first place? Can they be used in an actual scenario’s, or are they just purely hypothetical? Can they be used to...
  19. E

    Other Anyone read 'Road to Reality'?

    Someone mentioned this book to me, and when I searched for it I saw some people describing it as a 'pop-sci' sort of book. But looking at the contents would suggest it's definitely not introductory, and in fact, quite the opposite (I don't know of any 'pop-sci books' that decide to launch into...
  20. Hacker Jack

    What is the reality of being a physicist?

    Who are the people that work on the ground breaking theories and the major discoveries, the big stuff! Why aren't most physicists the next Einstein or "Insert famous scientist here" and what do they work on for their day to day work? I wonder this because a lot of people who don't know much...
  21. C

    What features in today's sci-fi do you think will become reality?

    Following Clarke's thinking “Magic's just science that we don't understand yet.”, I am quite switched off with today's sci-fi it is basically 'magic' but dressed up to be technological. It seems to me (maybe just my POV) that decades ago there was a more balanced mix of stuff that was at the...
  22. Hacker Jack

    B Do you think quantified things exist in reality?

    For example, measurements and how we have set points of measurements, and an infinite amount of increments in between them. Do you this measuring system exists in reality? What is an alternative way of looking at the world in a quantified way (or non quantified way) other than the current...
  23. Macoleco

    How long until Full Dive Virtual Reality?

    I am obsessed with the development of the Full Dive Virtual Reality (transporting your consciousness to a virtual world, such as Sword Art Online). I believe this technology may be available at around 200 to 300 years. How long do you think it will take us, if at all?
  24. Mayan Fung

    How to get maximal power output from solar panels in reality

    I learned that solar panels have their maximal power output at a particular voltage and current level. If we want to get the max power, we have to connect a load with a specific resistance. However, in reality, how does the solar plants solve this problem? I guess they won't allow the power...
  25. A

    Centrifugal forces don't exist in reality?

    We can often hear that centrifugal force don't exist in reality...Helicopter mi-26 can lift 56tons ,it has 8 blades,so each blade hold 7 tons of force! Do you know if you put 7tons at blade when blade is not rotating(static) ,bending moment will be way too much and blade will broke at root...
  26. T

    A Is physical reality more than the sum of its parts?

    There is a paper here: https://www.mdpi.com/1099-4300/19/5/188 And a lengthy article here: https://www.quantamagazine.org/a-theory-of-reality-as-more-than-the-sum-of-its-parts-20170601/ The general argument concerns causal emergence and whether all causal agency arises directly from the micro...
  27. E

    The maximum length that a spring can stretch in reality

    In detail, I came up with 424m for the stretched length of a spring in order to change the mass of an object by 10^-9kg which originally was 1 kg. Problem said, "is it feasible?" In my opinion, there is no spring that can be stretched for this long, so it is not feasible. However, I'm not sure...
  28. Jaffer2020

    Refraction of Light: Myth or Reality?

    In my latest 10th grade physics lesson, we were learning about the refraction of light. I decided to share what I knew about why light slows down in a vacuum, which is, in short, because the electric field of the electromagnetic wave exerts a force on the charged electrons of a medium, which in...
  29. S

    A Algorithmic information theory's QM view of reality

    Where can I learn more about this conception of reality?
  30. S

    I Understanding algorithmic information theory's reality

    Where and how could a layperson begin to understand algorithmic information theory and its proposed version of reality? I just read some "bits" (pun intended) about its strings of events and how it proposes algorithms can predicts how subjective timelines will continue, and I want to learn more!
  31. Quantum Alchemy

    I Questions about QFT and the reality of subatomic particles

    I've been reading about Quantum Field Theory and what it says about subatomic particles. I've read that QFT regards particles as excited states of underlying quantum fields. If this is the case, how can particles be regarded as objective? It seems to me that this also removes some of the...
  32. S

    I Did Schrödinger himself take his "Cat Experiment" seriously?

    In 1935, Austrian physicist Erwin Schrödinger was looking at a concept called a "superposition." Superposition is when two waves meet and overlap and interact, which can lead to different results based on the circumstances. The concept can be seen in the regular-sized world as well, in...
  33. S

    I Did Erwin Schrödinger propose that reality could be contradictory?

    Did Schrödinger believe that contradictory or inconsistent things could exist in reality?
  34. entropy1

    I Is Einstein Causality Proven in Preferred Frame SR?

    If MWI and collapse-theory are both possible interpretations of QM, then both of them are not a fact, right? If MWI is a fact then collapse isn't and vice versa, you could say the least. So, shut up and calculate, i.e. the minimal interpretation, makes no inference about the realness of these...
  35. entropy1

    I Is Reality Real? Examining the MWI Theory

    Could MWI signify that there are not necessarily a (near) infinite number of real worlds, but rather that officially we can't tell if, or to what degree, the world we are in is real?
  36. D

    Cosmology Is Road to Reality by Penrose Suitable for Non-Experts?

    I recently acquired the tome of Penrose's Road to Reality. I'm trying to figure who this book is intended for. It has a mix of deep mathematical physics concepts with light explanatory diagrams. I have a little bit of a mathematical background, bachelors in math, so I can follow it pretty...
  37. GuillemVS

    B But in reality, time isn't relative at all, right?

    I don't know how to make that question better, to not seem as if I'm asking why is time relative (that's not what I'm looking, I think). When we say that time is relative, we look at how many time takes light to go from one point to another, in order to be seen from another perspective. So...
  38. S

    B Is 3D reality merely an illusion?

    Hi, everyone! I read an online article, some time ago, on the Holographic Universe, and how it might operate. According to the author, quantum bits, or"qubits"of information exist on the surface of a cosmological horizon. Complex interactions between these qubits result in them becoming...
  39. entropy1

    I The (quantum) world existing AND non-existing

    Can we suppose that a quantum property (like spin, polarisation, velocity, position) becomes a potential, a probability, when we are going to measure it? Can we say that this property does not exist while remaining unmeasured, and that when measured takes on a value that depends on both the...
  40. C

    A physicist wannabe somehow doing a Master's degree

    I am a physicist wannabe but have come full circle to the realisation that average marks in physics isn't going to cut it in this field. My laziness in my critical thinking and life in general, my focus on marks (which haven't produced marks anyway), and lack of engagement with anything but...
  41. Demystifier

    A Does the Bell theorem assume reality?

    A large portion of physicists thinks that Bell's theorem shows that reality does not exist. Another large portion of physicists thinks that reality is not an assumption of Bell's theorem, so that Bell's theorem just proves nonlocality, period. A third large portion of physicists thinks that both...
  42. Cantor080

    I Existence of experience related to i

    If we have solution of an equation as x=1, it may be expressing, depending on context, 1 apple, 1 excess certain thing, etc. And, if we have solution of an equation as x=-1, it may be expressing, depending on context, 1 deficient apple, 1 deficient certain thing, etc. Is there any experience...
  43. M

    I Is Nature Non-Deterministic Due to Nonlocality in Quantum Mechanics?

    From what I understand, the most reasonable explanation of the violation of the Bell inequalities is that nature is non local. If we accept this, is there a reasonable argument that nature is not deterministic? I.e. could it be that the probabilistic predictions from QM are just averaging --...
  44. G

    I What Does Gauge Invariance Tell Us About Reality?

    This is not a technical question. I'd like to have a more conceptual discussion about what - if anything - gauge invariance tells us about reality. If we could, please try to keep the discussion at the level of undergrad or beginning grad. To focus my questions and keep things elementary, I'd...
  45. C

    B Does anybody think that there is an underlying reality?

    It seems like we keep chasing "reality", and by "reality" I think Physicists would mean the apparent rules of quantum physics which we hope would (if applied) lead to all the apparent known rules of macro-physics. However ... It seems like we have had to create a few things to do that: 1. Ideas...
  46. Russell Patterson

    Insights Orbital Mechanics in Unity Game Engine for Augmented Reality - Comments

    Greg Bernhardt submitted a new PF Insights post Orbital Mechanics in Unity Game Engine for Augmented Reality Continue reading the Original PF Insights Post.
  47. G

    The reality of photons (real vs virtual etc)

    I mean there is this division between virtual (in static situations) and real photons as the quanta of the EM field, but aren't all photons essentially "virtual" in the sense that they are purely made up by us in order to explain why we see discrete impacts of specific energy for a given EM...
  48. T

    When does a cantilever beam fail in reality?

    Hi, like the title says, how do we actually calculate when a cantilever beam fails in reality? We’ve been taught that these are absolutely fixed to the ground. However, in reality these would probably be bolted onto the ground, so how do we calculate the force trying to lift the fixed beam on...