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.

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  1. M

    Visualization of uncertainty principle [graphs]

    Homework Statement I'm looking for graphs or other sources of uncertainty principle visualization (I'm suppose to use a Fourier transform to solve it and present visualization in MS Excel... but one thing at a time). Homework Equations The Attempt at a Solution Digged google in 3 languages. I...
  2. T

    Carrying Uncertainty in Math: A Paradox?

    Ok so my textbook explains all the rules to carry the inherent uncertainty in measurements through mathematic calculations (the result of an addition must have as many decimal places as the term with the least decimal places, etc, it also explains significant figures etc...) and at the very end...
  3. S

    Find moles of MNo4; % uncertainty and % error

    My group messed this experiment up and now i have to get a good grade(i receive 50% on all of my labs!). I would highly appreciate your input. Our teacher gave us a procedure sheet, which we "accurate followed" This is what we did:(If this is not enough i have a few more steps that were done...
  4. D

    Heisenberg Uncertainty Principle - find minimum uncertainty in position

    Homework Statement Assume speed of 435g football is known with 1mm/s uncertainty. What is the minimum uncertainty in its position? Homework Equations I'm not quite sure... I know p=mv, and I know that Heisenberg's uncertainty principle states that certain parameters of quantum...
  5. C

    Finding the uncertainty of this problem

    Homework Statement When a mass of 166.5 ± 3.0 g is added to a spring the spring extends 7.20 ± 0.16 cm. What is the uncertainty in the spring constant, k? You may assume g is known precisely with no uncertainty. Homework Equations The Attempt at a Solution I just converted...
  6. G

    Uncertainty in Mean Value: How Many Decimal Places?

    hi i have some measured values that refer to a simple experiment where a stone was thrown along a fixed length and now i have these values for the time the stone needed time 13.8 13.7 13.9 13.5 14.4 14.6 14.1 14.3 13.9 14.7 i was asked to explain how many decimal places one would write...
  7. B

    What is the uncertainty speed of a hydrogen atom inside a virus?

    What is the uncertainty speed of a hydrogen atom inside a virus? Even though the vaue of uncertainty in position is not given. Any help on this would be greatly appreciated. Thanks!
  8. D

    Why is heisenberg uncertainty not a limit of technology?

    How do we know that the uncertainty principle is a property of an electron and not a limit of our measuring ability? I understand that photons striking an electron alter its momentum, but imagine an electron that is not being observed. Couldn't it have both a position and a momentum at a given...
  9. M

    Uncertainty Principle Examples in Solid State Physics

    Hi, I'm working on a homework for my solid state physics class and I'm having trouble with this question: Homework Statement "We have seen many cases in solid state physics in which you can apply the concept of uncertainty principle to estimate some quantity. Describe two examples of a...
  10. spacecadet11

    Can someone explain the Heisenberg Uncertainty Principle?

    Hello...sorry about the vague nature of the question..but I am trying to learn in an 'economical' sort of way. That is asking almost redundant questions..but answers I can work with in a 'free style' way...and gain understanding in the process or be able to ask another question. Can someone...
  11. D

    Estimating with uncertainty principle

    http://quantummechanics.ucsd.edu/ph130a/130_notes/node98.html Can someone help me understand what's going on here? He says "The idea is that the radius must be larger than the spread in position, and the momentum must be larger than the spread in momentum." which I suppose must be true in...
  12. T

    Heisenburg Uncertainty Principle - Seems like an easy question?

    Heisenburg Uncertainty Principle - Seems like an easy question?? Homework Statement The position of a 900 kg boulder's center of mass has been determined to within an uncertainty of 1.0 nm. (a) What is the minimum uncertainty in the boulder's velocity? (b) Repeat the calculation, but for a...
  13. G

    De Broglie-Bohm and the uncertainty principle

    According to the De Broglie-Bohm theory, is the universe, in its current state, the only one that could have evolved from its early conditions? In other words, because in the theory, each particle actually possesses well-defined position/momentum/trajectory, does the theory imply that the...
  14. J

    Basic:applying uncertainty principle for confined particle

    i tried to apply uncertainty principle to an electron confined in a 3d box of size 1fm. i got uncertainty in velocity Δv to be of the order 1010 m/sec.so i thought maybe i should have taken relativistic mass instead of rest mass. but i realized that for calculating relativistic mass we...
  15. H

    Calculating percentage uncertainty for young's modulus

    Homework Statement I cannot work out how to calculate my percentage uncertainty for my coursework, i need to show that my second method has a reduced uncertainty than my first, could anybody please enlighten me as to how to work it out. My table for one of the practicals is attached Homework...
  16. E

    Vacuum energy and principle of uncertainty

    Let us assume that harmonic oscilator has the lowest energy level equals 0, (and next one \hbar \omega and so on). Does this harmonic oscilator violates the principle of uncertainty? Let us assume that energy of vacuum equals 0 and not \hbar \omega/2. Does such vacuum violates the principle...
  17. Y

    Heiseinbeg's Uncertainty Priciple and Schrodinger's eqt

    Can somebody please explain the basis for the Heiseinberg's Uncertainty Principle and the Schrodinger's Theory or me? I m confused with the movement of electron in the orbitals and i think these 2 theories are the key. Thanks
  18. B

    Question on uncertainty Principle

    I had a quick question on the uncertainty principle. I'm not a physicist but I'm familiar with the basic theories. I've never had anyone explain it to me like this, but this seems to be an intuitive way to look at it. So I need to know if I'm framing this right. In classical, you start...
  19. G

    Does the uncertainty relation apply to the past?

    Can anybody clear this up for me? In his Chicago lectures in 1930, Heisenberg is quoted as saying “The uncertainty relation does not hold for the past…If the velocity of the electron is at first known, and the position then exactly measured, the position of the electron for times previous...
  20. fluidistic

    Angular momentum and its uncertainty

    [L_x,L_y]=i \hbar L_z \neq 0. In fact it seems we can know only the modulus squared of the angular momentum and one component, at a same time. However if I take an electron say in the fundamental state in the hydrogen atom, L=0. Since the modulus squared is equal to 0, it means that all...
  21. K

    Uncertainty Propagation for the Slope of a Line of Best Fit

    Hi guys, So I'm writing up a physics lab and I have a bunch of data points. All of these data points have both x and y error bars. The relationship between x and y is linear and so I've made a line of best fit using Python passing through the data. Now the slope of that line of best fit...
  22. B

    The Heisenberg Uncertainty Principle

    The general definition is that we cannot determine the location and velocity of a particle at any given moment. However, my intuition is to assume this is due to shortcomings in technology and measurement, but apparently that's false. This is a rule of nature. Can you explain what exactly the...
  23. M

    Significant figures and uncertainty

    Let’s say I have a class A 25ml pipet with an uncertainty of +/- 0.24ml. If I want to express the volume of the pipet to the correct number of sig figs to say determine the sig figs in a final answer - what is it? Is it 25 ie two, because that is the marking? Or 25.00 ie four...
  24. 2

    Quantum Physics: Heinsburg Uncertainty

    Homework Statement A laser produces light of wavelength 540 nm in an ultrashort pulse. What is the minimum duration of the pulse if the minimum uncertainty in the energy of the photons is 1.0%? Homework Equations ΔEΔt ≥ hbar / 2 The Attempt at a Solution Now I tried a couple ways...
  25. P

    Uncertainty values for non-Gaussian functions

    Uncertainty values for non-Gaussian wave packet functions Homework Statement \phi(k)= \left\{ \begin{array}{cc} \sqrt{\frac{3}{2a^3}}(a-|k|), & |k| \leq a \\ 0, & |k|>a \end{array} \right. \psi(x)= \frac{4}{x^2}sin^2 (\frac{ax}{2}) Calculate the uncertainties \Delta x and \Delta p and check...
  26. Z

    Uncertainty in radioactive half-life experiment

    Homework Statement I have conducted an experiment and found the gradient λ of a graph to be (2.15x10^-4) +- (0.15x10^-4) The graph being ln(A) i.e. the number of disintegrations/unit time - dN/dt against time t The half-life is T(1/2) = ln(2)/λ = -3223.9 How do I find the...
  27. J

    What is the uncertainty of Δx for the given wavefunction?

    Homework Statement Suppose that at one instant in time the wavefunction of a particle is ψ(x) = \sqrt{b}e-b|x| Estimate the uncertainty of Δx for this wavefunction. Homework Equations ΔxΔp ≥ h(bar)/2 h(bar) = h/2pi The Attempt at a Solution Do I just calculate the...
  28. M

    I dont understand how to calculate percentage uncertainty?

    I don't understand how to calculate percentage uncertainty!? I know in chem we calculate uncertainties by smallest division/the reading X 100. But in physics i am clueless. For instance here's an example The power loss P in a resistor is calculated using the formula P = V^2/R. The...
  29. M

    What experiment demonstrates Heisenberg's uncertainty principle?

    When I read about the uncertainty principle, I keep reading about these experiments where they fire electrons through a single or double slit and observe the diffraction but I can't these experiments relate to Heisenbergs uncertainty principle. So when they fire the electrons, they know their...
  30. G

    Time-energy uncertainty and virtual particles

    I have seen an argument that the time-energy uncertainty relation allows heavy particles to exist for short periods of time as virtual particles: (ΔE Δt)>h Δt>h/ΔE However, shouldn't the inequality be the other way: Δt<h/ΔE to suggest that a heavy particle with large ΔE can exist...
  31. S

    Energy-Time Uncertainty of Gaussian

    Homework Statement Check the energy-time uncertainty principle for: \Psi(x,0)=Ae^{-ax^2}e^{ilx} using the observable x. Homework Equations \Delta{E}\Delta{t}\geq\hbar/2\\ \Delta{E}=\sigma_H=\sqrt{<H^2>-<H>^2}\\ \Delta{t}=\frac{\sigma_x}{\frac{d<x>}{dt}} The Attempt at a...
  32. M

    Non-Stationary State Wavefunction - Normalized? <L^2>? Uncertainty on L^2?

    Homework Statement Consider the nonstationary state: \Psi = \sqrt{\frac{1}{3}}\Psi_{22-1} + \sqrt{\frac{2}{3}}\Psi_{110} Where \Psi_{22-1} and \Psi_{110} are normalized, orthogonal and stationary states of some radial potential. Is \Psi properly normalized? Calculate the expectation value of...
  33. K

    Percentage uncertainty and percentage difference

    Hello my teacher said that percentage uncertainty is a measure of precision and percentage difference a measure of accuracy. i thought it's the other way round?? say if i have 20% and 80% what do these values tell me in terms of precision and accuracy?
  34. nukeman

    What would my uncertainty be with these 2 values?

    Homework Statement I am doing percent difference of 2 values. value 1 = .013329 +- .001 cm value 2 = .013331 +- .001 cm So, for percent difference I do: .013331 - .013329 / ((.013331 + .013329)/2) gives me .015%, but what would my uncertainty be? I don't wuite understand...
  35. I

    Uncertainty Principle of a nonrelatavistic particle

    Homework Statement If the uncertainty in the location of a nonrelativistic particle is about equal to twice its de-Broglie wavelength, show that the uncertainty in its velocity is greater than about 4% of its velocity. Homework Equations ΔpΔx>h/4Pi p=mv Δx=2nλ The Attempt at a...
  36. Q

    Uncertainty Principle application to macroscopic particles

    1. Homework Statement The figure shows 1.0*10^-6 m diameter dust particles in a vacuum chamber. The dust particles are released from rest above a 1.0*10^-6 m diameter hole, fall through the hole (there's just barely room for the particles to go through), and land on a detector at distance d...
  37. Q

    Heisenberg Uncertainty Principle or Diffraction problem

    Homework Statement The figure shows 1.0*10^-6 m diameter dust particles in a vacuum chamber. The dust particles are released from rest above a 1.0*10^-6 m diameter hole, fall through the hole (there's just barely room for the particles to go through), and land on a detector at distance d...
  38. M

    Uncertainty relation between number of photons in an EM field and its phase

    Derive the relation Δn.Δσ ≥ 1/2 where n is number of photons in an EM field and σ is phase Using heisenburgs uncetertainty principle? Tried subbing in frequency into heisenburgs uncertainty principle to get to the number of photons and to get rid of mometum is this the right line? Dont...
  39. ShayanJ

    Uncertainty principle in classical optics

    As you know,a pure sine wave extends infinitely in both directions and a wave which is the composition of some different frequencies,has a limited extent.Does it mean that such a wave is a pulse moving in space or it has limited range?(I know its crazy to talk about the range of light,but I've...
  40. R

    Converting Uncertainty in Millimeters to Meters for Radius Calculation

    In a lab, i used a micro-caliper to measure the diameter of an indicator; I got 3.681 mm \pm 0.005 mm. However, i need the measurement to be in meters and i need to divide the measurement by 2 (as i need the radius, not diameter) for easy calculations. I know how to convert the 3.681 mm to...
  41. M

    Understanding Uncertainty Principle

    Hello All, I want to understand uncertainty principle. I understand that when we measure x accurately we cannot measure p with that accuracy. The process of measuring x accurately might like this: some detector fires high energy photon to that small particle, and we can know x accurately. But...
  42. D

    Intermediate Physics Lab Analysis, Uncertainty and Linear Regression

    Homework Statement "You are asked to do an experiment where you will need to use a rotating blade to measure the wind speed. You measure the number of rotations of the blade at 10 different wind speeds, 10 times each and will make a linear fit to determine the wind speed as a function of...
  43. R

    Uncertainty Principle & Particles Giving Off Light

    If a particle gives off its own light, how can we never know its position as well as its momentum, as we can see it and thus measure its speed, and know its velocity? How does the Uncertainty Principle treat this circumstance?
  44. R

    Finding the Uncertainty of Vy in a Physics Equation

    Physics Uncertainty Question? Homework Statement I have Vy = 0.125tan(54) = 0.17204. I have to find the uncertainty of Vy Where 0.125 = A and tan(54) = B uncertainty of A (0.125) = 0.0005 uncertainty of B (54 degrees) = 0.5degrees Homework Equations Uncertainty for Multiplication =...
  45. StevieTNZ

    Heisenberg Uncertainty Principle

    From what I've gathered reading the scientific literature, the more precise we know a quantum system's position, the more uncertain the momentum becomes. Does the uncertainty principle place a limit on how well we can know a system's position when we measure that observable? I've read...
  46. C

    Uncertainty principle and particle accelerators

    Fairly simple question but it's been bugging me for a while: Particle accelerators such as the LHC publish some impressive images of the tracks of particles in their detectors. Can someone explain why that is possible considering the uncertainty principle?
  47. M

    Heisenberg Uncertainty principle in 3D

    Hi there, So here's my assignment: ''The velocity of a positron is measured to be: vx=(4.00±0.18)*105 m/s, vy=(0.34±0.12)*105 m/s, vz=(1.41±0.08)*105 m/s. Within what minimum volume was the positron located at the moment the measurement was carried out?'' I think I'm not wrong when I say that...
  48. J

    Uncertainty of planetary orbital period

    I've been searching all over the place, and I cannot find any data showing the error bars of orbital periods of planets. Once source estimates the uncertainty of Jupiter to be "1 arcsec per 250 years" but I cannot find anything to back this up. Does anybody have any hints as to where I should...
  49. J

    Uncertainty principle and information theory

    does the fact that there is a limit on how much can be observed on electrons location and momentum have anything to do with the finiteness and conservation of information? is the total momentum plus location of an electron unknown to us or is it also unknown to the universe? meaning, does...
  50. S

    Is uncertainty inherent in QM?

    For example let's look at a single particle, double slit experiment: we know that the particle (photon/electron) will land up on one of the fringes. however it is commonly understood that we cannot predict which of the fringes will it land up on. one could argue that since there was...
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