What is Uncertainty: Definition and 1000 Discussions

Uncertainty refers to epistemic situations involving imperfect or unknown information. It applies to predictions of future events, to physical measurements that are already made, or to the unknown. Uncertainty arises in partially observable or stochastic environments, as well as due to ignorance, indolence, or both. It arises in any number of fields, including insurance, philosophy, physics, statistics, economics, finance, psychology, sociology, engineering, metrology, meteorology, ecology and information science.

View More On Wikipedia.org
Recent contents Top users
  1. N

    How to appropriately assign sigma values (uncertainty)

    First let me preface this by saying, I'm not a native english speaker. I'm not sure "uncertainty" is the word I'm looking for it might also be deviation, however it is the translation of what its called in Danish, my native tongue. I'm doing a lab report about rolling objects on a slope, for my...
  2. H

    How do I find the uncertainty in this specific scenario?

    Homework Statement The task is to find the uncertainty of the magnetic field, B. The magnetic force is plotted against current, so that the slope of the resulting line of best fit is LB, where L is the length of the conductor and theta is constant at 90 degrees (thus sin(theta) = 1). The...
  3. C

    What is the uncertainty in the derivative of a function?

    Hey, Homework Statement I was working on a kinematics experiment using Tracker to do a video analysis. I obtained a graph of displacement against time for the body under constant acceleration and the software also gives me the rms error between the parabolic trend line and the data points...
  4. R

    B Possible Loophole in the uncertainty principle

    The uncertainty principle states that anyone given person who knows a lot about a given particles velocity will know less about the location, but if then they try to observe the location, the less they will know about the velocity. What if two scientists observed one particle though. One...
  5. S

    Problem about momentum uncertainty

    Homework Statement According to the Big Bang model of cosmology, the universe has been expanding since some initial time (call it t = 0) when the temperature was infinite. At early times, the temperature T scales as t^1/2 . The current temperature is about 3K. Consider the part of space which...
  6. S

    Measuring uncertainty spec for an oscilloscope?

    I just started learning about oscilloscopes and I am confused on how to calculate the uncertainty. The uncertainty measurement on the device says '1/2 the smallest division'. I am unsure which 'division' this refers to since there are horizontal scales and vertical scales. In my experiment I...
  7. L

    I How is uncertainty affected by absolute numbers?

    Example: Say I want to calculate the evaporation rate of water and so I record the mass of some amount of water every 30 seconds for 5 minutes. The uncertainty in the scale is inherently .0001g and so that would be the uncertainty in the mass of any individual measurement, but how would I...
  8. D

    I The uncertainty principle and moving reference frames

    To what extent is the Heisenburg Uncertainty principle a statement about moving frames of reference? The ill-defined position of a particle seems to imply that one can never find an inertial frame of reference in which the velocity of a given particle is constant.
  9. Mrq

    What's wrong with my calculation here? (propagation of uncertainty)

    Homework Statement I have to calculate the propagation of uncertainty for my error analysis lab but I am getting a percentage error of about 22-34 percent, just because the partial derivative of gravitational acceleration with respect to time has a large value. Could somebody please help? I...
  10. H

    I Uncertainty Analysis: Understanding Errors in Quantity Measurements

    Hey, I have a question about uncertainty analysis. So my university told me that, usually a quantity has 3 types of errors, reading error, standard deviation (which comes from some repeated measurements of that quantity), and equipment accuracy (which is usually stated on the equipment). My...
  11. SJay16

    Finding the uncertainty in delta y?

    Homework Statement Find the uncertainty ∆y in y as a function of the uncertainties ∆u and ∆v in u and v for the following functions: y = 1/2(u+v) Homework Equations : Error propagation formula[/B] The Attempt at a Solution Don't know where to begin even. Help?[/B]
  12. A

    Significant Digits for Uncertainty Values

    Homework Statement Question on worksheet: What is the random uncertainty in this set of measurements? Use the instrumental uncertainty to limit the number of digits in your random uncertainty result. Data for dropping a pencil from a height of one meter using a stopwatch that measures to the...
  13. D

    B Does Heisenberg's uncertainty principle imply no free will?

    Does the Heisenberg uncertainty principle mean that some particles do not have law-determined properties like position and momentum, or does it mean that their properties cannot be measured accurately? In other words, do all particles have a certain position and momentum at time t? This question...
  14. J

    How to calculate the uncertainty for weight?

    Homework Statement Hello, I am calculating the uncertainty for a course I am in. I am specifically calculating the uncertainty for the weight of coins in my experiment. Homework Equations The weight of coins in my experiment is equal to the number of coins I used in the part, multipled by...
  15. Isaac0427

    B Uncertainty of a Gaussian wavepacket

    Hi, I know that a Gaussian wavepacket has minimum uncertainty. The issue is, some sources are telling me that σxσp=ħ and others are telling me that σxσp=ħ/2. I am really confused. I think the latter is correct due to what I have been taught about the uncertainty principle, but then I don't...
  16. LarryS

    I Is Entropic Uncertainty Principle taken seriously in QM?

    Is the Entropic Uncertainty Principle taken seriously by experimental physicists? For example, is it considered more accurate than the HUP that uses standard deviations? Thanks in advance.
  17. F

    I Understanding Measurement Uncertainty: Calculating Accuracy and Precision

    I have seen similar threads on here but not one with any detailed answer so I felt I would ask myself. I took a short undergrad module in measurement and uncertainty, intended to prepare for the numerous lab sessions and reports that would follow in the proceeding modules. In that particular...
  18. stevendaryl

    B Probabilities associated with temporal uncertainty

    This seems like a simple matter, but apparently it is controversial: Is it meaningful to talk about probabilities for temporal uncertainty? If I find myself in a room without a clock, I might wonder what time it is. I know that I entered the room at 9:00, so it has to be later than that. I know...
  19. Thejas15101998

    I Forms of the Uncertainty Principle

    Well, i came across the so-called both the forms of the uncertainty principle of Quantum Mechanics: the position-momentum form and the energy-time form; but i am not satisfied in one way. Here the trio: position, momentum and energy, all of them have their own operators, but time does not have...
  20. Lunct

    I What are the units for the Heisenberg Uncertainty Principle?

    To my understanding(correct me if I am wrong), one consequence of the Heisenberg Uncertainty Principle is that energy levels can fluctuate by some amount, e, for a short time, t. As long as e x t does not exceed h/4pi (where h= Planck's constant). My quarry is that what are the units for the...
  21. J

    Pulse echo technique to find the distance of the Moon

    Homework Statement [/B] Over 40 years ago, the Apollo astronauts placed reflectors on the surface of the Moon. These are still used by a number of observatories on Earth to monitor the distance to the Moon by reflecting pulses of laser light from them and detecting the reflected signal...
  22. Radiosan

    Uncertainty analysis of 2 port measurement

    I analyzed uncertainty analysis of 2 port measurement. I referenced 2 book "Transmission Reflection and Short Circuit Line Methods for Measuring Permittivity and Permeability" at pages 31 equation(2.83) "Transmission and Reflection and SCL Permittivity Measurements" at pages 44 equation(2.67)...
  23. AdrianMachin

    Height differences from relative uncertainty of gravimeters

    Homework Statement The best relative gravimeters have a relative uncertainty of 10-12, that corresponds to a height difference of 3 µm. Homework Equations g∝(1/r2) The local gravitational acceleration g outside the Earth is proportional to 1/r2, which means (Δg)/g = -2 (Δr)/r. With (Δg)/g =...
  24. A

    A Stochastic differential equations with time uncertainty....

    Hi all, I'm wondering if anyone is able to point me in a direction regarding an aspect of stochastic differential equations. I have a situation in which I need to propagate a stochastic DE through time using measurement updates - however, the exact time at which each measurement arrives is...
  25. G

    Uncertainty of the function? My answer is a bit different

    Homework Statement Homework EquationsThe Attempt at a Solution The answer is different though,
  26. C

    I Exploring Classical Uncertainty in Quantum Mechanics

    In Quantum Mech. we learned about classical uncertainty, and then Heisenberg's uncertainty principle which comes from it. The way it is in the book is, the preceding chapter talks about how the superposition of lots of waves ∑ gives you these groups, and things like group velocity comes from...
  27. M

    A Can a Point-Like Particle Defy the Uncertainty Principle?

    Imagine a spatial frame of reference attached to a point-like particle. It has x=0 since it is at the origin and p=0 since it is at rest. Having definite position and momentum is normally considered a violation of the uncertainty principle. How would you resolve this paradox? 1. Position frames...
  28. A

    B Can %age uncertainty in value ever be greater than 100?

    We were given an experiment in which the %age uncertainty of majority of students happened to be greater than 100?
  29. Larry

    A Non-Heisenberg Uncertainty Relations

    Simultaneous tracking of spin angle and amplitude beyond classical limits Nature 543, 525–528 (23 March 2017) www.nature.com/nature/journal/v543/n7646/abs/nature21434.html The authors remark that "because spins obey non-Heisenberg uncertainty relations, enables simultaneous precise knowledge...
  30. G

    I How to calculate the uncertainty of success rates?

    I am writing a report for my boss quoting the success rates for tests of various components. If something works 19 times out of twenty, then it's 95%. But what is the uncertainty on this? 95% +/- ? And if a component passes every test (100%), what is the lower limit on the actual rate? How many...
  31. benny91xp

    B Walter Lewin videos -- why ± 0.5 cm uncertainty why not ± 0.1?

    here is the link to walter lewin video lecture please jump to 13:13 8.01x - Lect 2 - 1D Kinematics - Speed, Velocity, Acceleration i thought that all meter ruler/ meter stick use ± 0.1 cm as uncertainty .how did he get ± 0.5 cm?
  32. Helios

    B Finite Universe vs. Uncertainty Principle

    If I have this right, when we have exact certainty of a particle's momentum, the bounds of this particle's location cannot be determined. Now there are some who believe in a universe of finite volume and so this particle has to be within this volume. So there seems to be a contradiction. Does...
  33. John Morrell

    I Understanding Double Slit interference and Uncertainty

    I've recently been doing some learning about the double slit experiment and a bit about how, qualitatively, quantum electro dynamics works. Something that I wondered about for a long time was how momentum could be conserved in these systems when we assume that a particle could land in any number...
  34. wolram

    B Scientists evade the Heisenberg uncertainty principle

    https://www.sciencedaily.com/releases/2017/03/170322143233.htmDate: March 22, 2017 Source: ICFO-The Institute of Photonic Sciences Summary: Researchers report the discovery of a new technique that could drastically improve the sensitivity of instruments such as magnetic resonance imagers (MRIs)...
  35. T

    Absolute Uncertainty of 1/d^2 Homework

    Homework Statement Given values and uncertainties of d, find the absolute uncertainty in 1/d^2 (see table attached) Homework Equations I know that if it's a square function the absolute uncertainty will be 2 (delta d) / d but I'm not sure if it's correct for an inverse function. The Attempt...
  36. R

    I Experimental Data - Error in slope

    I have conducted a tensile test on five specimens. I intend to do a linear regression for every set of data and get a value for the slope (modulus of elasticity) and its error by finding the standard deviation (using LINEST function on excel) of the slope. I will now end up with 5 slope values...
  37. M

    I Does the Uncertainty Principle restrict a particle's path?

    In the classical definition, velocity is the time derivative of the particles position curve (trajectory). The Uncertainty principle restricts the particles velocity from ever being zero. Doesn't this imply that a particles path is restricted to paths that do not have a zero time derivative at...
  38. H

    Single slit with minimum uncertainty

    Homework Statement A horizontal beam of laser light of wavelength 474 nm passes through a narrow slit that has width 5.80×10−2 mm . The intensity of the light is measured on a vertical screen that is 2.40 m from the slit. Use the result of part A to estimate the width of the central diffraction...
  39. H

    A Uncertainty Propagation of Complex Functions

    Suppose I have some observables \alpha, \beta, \gamma whose central values and uncertainties \sigma_{\alpha}, \sigma_{\beta}, \sigma_{\gamma} are known. Define a function f(\alpha, \beta, \gamma) which has both real and complex parts. How do I do standard error propagation when imaginary...
  40. H

    A Uncertainty Propagation in Coupled Oscillator

    I am a senior physics and mathematics major, and this is my last semester. As a result, I am taking advanced physics lab, which feels more like a grad school experiment than an undergrad. One of the labs deals with the modal analysis of three spring-mass systems placed vertically as shown in the...
  41. J

    I Heisenberg's Uncertainty Principle common misconceptions

    Hi pf, Please help me, the more I read about HUP, the more discrepancies I find between different sources. I found a good article that Zapper made on HUP (https://www.physicsforums.com/insights/misconception-of-the-heisenberg-uncertainty-principle/). My confusion is about the way it is...
  42. T

    Calculate uncertainty in pressure, temperature and time?

    Homework Statement [/B] After doing a lab on air compressors, we were asked to calculate Error in Pressure, Temperature and time measurements taken (all at 30 second intervals). We took pressure and temperature values at time = 0,30,60,90,120,150 and 180 seconds. We repeated the experiment 5...
  43. Diana Moceiparisi

    Uncertainty in Fluid Viscosity Measurement: Improving Result Presentation

    Homework Statement a) The equation governing the flow rate, , of a fluid under streamline conditions through a horizontal pipe of length l and radius r is: where p is the pressure difference across the pipe and ƞ is the viscosity of the fluid. Thus, a student conducted an...
  44. C

    B Uncertainty Calculations for Electrical Measurements

    I know the rules to experimental uncertainties with addition and subtraction, but what about division? For instance here The light bulb was measured to have 1.27 ±.05V by the DMM in parallel. Using the DMM in series, its current drawn was .202 ±1A. As a result its resistance was approximately...
  45. A. Neumaier

    I On the Heisenberg uncertainty relation

    Are there fundamental limits on the accuracy for measuring both position ##q## at time ##t## and momentum ##p## at time ##t+\Delta t##, with tiny ##\Delta t##? If yes, why? If no, why can't one then measure (in principle) both ##q## and ##p## arbitrarily well at the same time ##p## (which is...
  46. R

    How Is Fractional Uncertainty Defined When the Measured Value Is Zero?

    <Moderator note: Thread moved from General Physics hence no formatting template shown> The fractional uncertainty is defined as: uncertainty/measured value. So for 2 cm +/- 1 cm we have 50%. For 9 cm +/- 1 cm we have 11.1%. My question is what if the measured value is 0 cm? How is the...
  47. zexxa

    Calculating uncertainty with a set of angles

    Homework Statement Hi there, the issue I'm having right now is finding the right way to calculate uncertainties when trigonometric terms come in play. The question goes like this, we're given 2 sets of 5 angles in degrees, the incident angle (10.0, 20.0, 30.0, 40.0, 50.0) and the other is the...
  48. P

    Finding Absolute Zero Values from Best Fit Lines with & w/o Uncertainty

    In one of my problems, I have this set of data. I have to create two best fit lines, and find a value of absolute zero for both. The first best fit line is to be made assuming there is NO uncertainty in P. This is rather straightforward, just use the normal linear regression, find a slope...
  49. Sunil Simha

    I Computing uncertainties in histogram bin counts

    I am working on astrophysical data and I have a large number of redshift values of quasars. Now, each redshift estimate comes with its estimated standard error naturally. If I plot a histogram of these redshifts, I would expect the bins counts to also have some sort of uncertainty. I am unable...
  50. DoobleD

    B Average Value Uncertainty: How to Compute?

    I have a set of values I got from measurements, and each of these value has an uncertainty associated to it. I compute the average of my values. How can I average the uncertainty associated to my average value ? Do I simply take the average of all uncertainties ?
Back
Top