Experimental Definition and 527 Threads

An experiment is a procedure carried out to support or refute a hypothesis. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated. Experiments vary greatly in goal and scale, but always rely on repeatable procedure and logical analysis of the results. There also exists natural experimental studies.
A child may carry out basic experiments to understand how things fall to the ground, while teams of scientists may take years of systematic investigation to advance their understanding of a phenomenon. Experiments and other types of hands-on activities are very important to student learning in the science classroom. Experiments can raise test scores and help a student become more engaged and interested in the material they are learning, especially when used over time. Experiments can vary from personal and informal natural comparisons (e.g. tasting a range of chocolates to find a favorite), to highly controlled (e.g. tests requiring complex apparatus overseen by many scientists that hope to discover information about subatomic particles). Uses of experiments vary considerably between the natural and human sciences.
Experiments typically include controls, which are designed to minimize the effects of variables other than the single independent variable. This increases the reliability of the results, often through a comparison between control measurements and the other measurements. Scientific controls are a part of the scientific method. Ideally, all variables in an experiment are controlled (accounted for by the control measurements) and none are uncontrolled. In such an experiment, if all controls work as expected, it is possible to conclude that the experiment works as intended, and that results are due to the effect of the tested variables.

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  1. J

    Where can I find chemistry experiments that are accurately described with the Dirac equation?

    Let's say we can solve the Dirac equation numerically with a powerful computer. What experiments do you recommend to take a look at to compare the result of the simulations with the real data. Maybe chemical reactions?
  2. AW3Rgo0l

    Studying How much chemistry do I need to know as a theoretical physicist?

    How much chemistry do I need to know as a theoretical physicist in order for this knowledge to be sufficient for research in any field of theoretical physics? It is also interesting to know how difficult the transition from theoretical to experimental physics is? Do experimental physics require...
  3. Dario56

    What determines the pressure inside this experimental setup?

    I have two gas tanks of nitrogen and oxygen. Mixture of gases is created and used in the system of interest. Let's say I want to create an atmospheric conditions in my system, mass ratio of oxygen to nitrogen is 0.3 and total pressure of 1 bar (oxygen partial pressure 0.21 bar). Therefore, mass...
  4. Ibix

    B What is the Experimental Basis of Special Relativity?

    The Experimental basis of SR FAQ (https://www.physicsforums.com/threads/faq-experimental-basis-of-special-relativity.229034/) no longer seems to be stickied at the top of this forum. Perhaps five stickies would be too many, in which case I think it's worth adding to the FAQ list...
  5. B

    A Learning about other experimental areas of physics

    Hello! My research is mainly in atomic and molecular physics but from time to time I come across nice experimental setups, that show promise for my work, from other fields, like chemistry or even high energy physics. I was wondering if there is a more organized way to explore experimental setups...
  6. R

    Computational, Theoretical, and Experimental Research: A Comparison

    Hi, I understand there is computational research as well as completely theoretical research compared to experimental research. I was curious about what they are like. Could anyone point out some good papers? Thanks.
  7. Y

    A Experimental nucleon form factors from electron-nucleus scattering

    I am looking for experimental nucleon form factors from electron-nucleus scattering. Is there any compliations or tables? In 'The proton charge radius ', H. Gao and M. Vanderhaeghen, Rev. Mod. Phys. 94, 015002 (2022), p. 24, there is 'world data on the proton and also the neutron'. In 'Form...
  8. uSee2

    Experimental Design: Pulley and Mass Hangers

    ^ This is my personal drawing of the diagram, I couldn't take a picture of the actual one. The setup is a pulley wrapped with a cord and mass hangers attached to each end. My first thought when approaching this problem was to first determine the rotational inertia of the pulley, then use some...
  9. M

    I Method for experimental results analysis

    Hello guys, I have conducted an experiment and got some results. I have 3 variables to vary, for example, five x1, five x2, and two x3 and 2 observation results, like y1, y2 I already make y1 y2 and x1 x2 x3 dimensionless since plot is 2D, what I am doing now is just plot when x3=1, x2=1, plot...
  10. J

    Can a Wing Truly Feel the Effective Airflow?

    Question is indeed very short and clear, but answer will eliminate many doubts and misleading conclusions. Theory predict downwash that will cause reduction in airflow angle,this we call effective airflow(airflow with lower angle compare at geometric AoA). Does wing of aircraft during flight...
  11. VVS2000

    I Wave packet experimental detection

    I know the wave function "collapses" when a measurement is made but still not satisfied with it
  12. Bastion

    B Experimental evidence for effective mass increasing with speed

    I am new to this forum and in line with its rules I am trying not to repeat a question already asked. I find that Jeremyfiennes original question I.e Experimental evidence for effective mass increasing with speed” is the question I want to ask but I am not satisfied with the answers given so...
  13. AJSayad

    Engineering Experimental Fluid Mechanics Vs. Computational Fluid Mechanics

    Hi everyone, I just started graduate school and I've been working in an experimental fluid mechanics lab. We have a shock tube and run tests on studying supersonic and hypersonic airflow under different conditions. We use Schileren imaging and transducers to take measurements during tests. We...
  14. N

    A Experimental Semiconductor Bandgap Databases

    I'm looking for experimental bandgap information to compare it to DFT calculations from Materials Project and OQMD. Could anyone recommend some?
  15. e2m2a

    I A Report on the Experimental Results of Inertial Effects

    I have attached [Mentors note: the attachment has been deleted] a paper (patent application number was 63/191,323 confirmation number 2211 filing date 5/20/21) that reports on an experiment that I did that strongly suggests that inertial effects can impact the speed of the center of mass of a...
  16. M

    A Experimental Studies of the Internal Energy of a real fluid

    https://www.nature.com/articles/s41598-022-11093-z In this new 2 May 2022 publication, an experimental effort was made to measure directly the internal energy changes of non-ideal CO2, from the decrease in temperature as the liquid-gas expanded from one cylinder into two. With the empirical...
  17. D

    I Experimental demonstration of an absorption spectrum

    Hello, is there a convincing experiment to visualize absorption spectra? At disposal I have: - Halogen lamps - Lenses - Straight view prism - transmission grating - slit, iris, screen - Sodium vapor lamp and mercury vapor lamp Unfortunately, I do not have a sodium vapor cell or anything...
  18. zrek

    B Experimental evidence on cosmological redshift

    The space expands due the dark energy, so the light wavelength also stretches during its journey between galaxies, causing a measurable redshift. How can I argue that this is the right reasoning for the measured redshift? What if someone states that the photon maybe simple loses its energy over...
  19. billyt_

    Experimental investigation of Faraday's Law of Induction

    Looking at how the induced EMF is proportional to the rate of change of magnetic flux, intuitively it seems that if I increase the velocity of the magnet through the solenoid, i.e. drop it from a higher height, the EMF should increase as well. However, I am unsure if this is true and can't seem...
  20. G

    I How to Experimentally Measure the MTF of a Lens?

    Hi all, I will like to measure the MTF of a lens experimentally. In the set-up, I have my light - target - lens - camera. When my object (target) is at the focus of the lens, I took an image. My question now is, to I move my object across one pixel or few pixels or to move my object across...
  21. L

    I Experimental average lifetime of particles

    My professor said that if I take 10^24 particles, for example, and I observe them for 1 years, I can say that their average lifetime is at least 10^24 years. I am not able to understand why, I though the law of decay is N(t) = N0*e^(-ta), so if after 1 year N(t) = N0, I can say ta ~ 0 , so tau...
  22. A

    B It works but why? (Matching experimental data to a random equation)

    Hey guys, I've about a week left to submit my final paper for my trade degree in transportation. The paper is about an analysis of potential implementation of an electric car for direct deliveries in my area where I live. In part of it, I try to analyze how many possible trips a car like...
  23. N

    A Probability Density Function: Converting Experimental Observations to PDF

    Hi All I am currently doing Master in data science. I came across the function PDF probability density function which is used to find cumulative probability(range) of a continuous random variable. The PDF probability density function is plotted against probability density in y-axis and...
  24. I

    Bubbles in buret experimental error

    When bubbles are not removed from a buret before a titration, the measured volume of titrant used is more than the actual volume used. Then the analyte concentration will be greater than the actual concentration, and the mass of the analyte will be greater as well. Instead, it will actually...
  25. Twigg

    Challenge Experimental Physics Challenge, June 2021

    Trying this out for fun, and seeing if people find this stimulating or not. Feedback appreciated! There's only 3 problems, but I hope you'll get a kick out of them. Have fun!1. Springey Thingies: Two damped, unforced springs are weakly coupled and obey the following equations of motion...
  26. T

    Experimental proof of Venturi Effect

    Venturi effect is known for centuries. And most probably that's why experimental proofs are rare because it's already accepted. But, I want to know how close real results are in case of experiments regarding Venturi Effect. I am especially interested in results of experiment regarding velocity...
  27. J

    B Experimental evidence for effective mass increasing with speed

    What is the best recent experimental evidence for effective mass increase (momentum/velocity) with speed, with experimental details? Searching the web all I find is either very old ones (early 1900s). Or vague generalized statements like (Wikipedia) "Many additional experiments concerning the...
  28. V

    Experimental Analysis: Forced Harmonic Motion and Resonance

  29. nicholas_eng

    I Experimental realizatoin of sequential Stern-Gerlach's

    So, an usual introduction to Quantum Mechanics (like the one given by Sakurai) is to refer to sequential Stern-Gerlach (SG) experiments. For example, a first one aligned to the z axis, a second one aligned to the x axis, and a third one aligned to the z axis again (with no relevant dynamical...
  30. Llukis

    A Experimental point of view of this Hamiltonian

    Dear everybody, I am involved with a system of two spins and I ended up with the following Hamiltonian: $$H_c(t) = W\sin(2J_+ t) \big( \mathbb{1} \otimes \sigma_z - \sigma_z \otimes \mathbb{1}\big) + W \cos(2J_+ t) \big( \sigma_y \otimes \sigma_x - \sigma_x \otimes \sigma_y \big) \: ,$$ where...
  31. J

    Michelson interferometer -- Plotting experimental data to determine t

    See attached images.
  32. G

    B Light Speed Invariance: Experiments, Difficulties & Clarification

    Let me clarify my question, is there any experiment directly proved the invariance of light speed to observers? Let's not get to the argument of equivalence between source and observer. SR was based on the postulate that the light speed is constant and independent of both the motions of source...
  33. R

    I How does this experimental result show photon emission?

    First I'll explain my understanding, because I'm not very confident in it. The main point is that the electrons are ejected and then accelerated to a very high kinetic energy. Then they start smashing into the anode. Most will go through a series of collisions before completely stopping, so that...
  34. J

    I Constrains on experimental space and parameters

    There is this argument that any new forces of nature or any new interactions would have very small gap of space left in the experimental space or parameter. The argument being that for every force, there is a particle and a field, and virtual particles. And the virtual particles can affect...
  35. davidbenari

    A Which condensed matter experiment PhD group is the most fun?

    This is going to be controversial and might even be taken down, but I think what I will say is absolutely true, and I'm sorry if it offends people. I'm applying for the second time to condensed matter PhDs. I was in a group that did a lot of device fabrication as part of their experiments and...
  36. phoenix-anna

    B First Experimental Confirmation of GR

    Trying to understand how Einstein predicted the appearance of stars during the solar eclipse around the turn of the 20th century (the first experimental confirmation of General Relativity, I believe). My impression, which is not physically correct, is that the sun attracts the photons as they...
  37. J

    B Experimental Confirmation Length Contraction Velocity Addition

    What if any is the experimental confirmation for length contraction and the velocity addition formula?
  38. quantumCircuit

    Lotka Volterra estimate parameters from experimental data

    Namely, in the system, I have obtained the value of parameters L, M, A and D, because I treat the other organism as equal to zero, i.e., it doesn't exist, but I am struggling about the values of B and C, that are coupled with the product of x and y. Can anyone help me how to obtain those values...
  39. Philip Koeck

    I Experimental test of the Mixing Paradox

    Can anybody point to an experiment that shows that the total entropy increases if two different gas mix at constant pressure and temperature, whereas if two volumes of identical gases mix the total entropy doesn't change?
  40. Judah_Idris

    Classical Physics from a Rigorous, Experimental Perspective

    I have a physics B.S. It seems like I learned little more than how to solve math problems as an undergrad. I want to know how the physical world works in concrete physical terms as much as is possible, so a big problem I have with physics is that concepts are very often explained in terms of...
  41. J

    A Experimental test of shrinking matter theory?

    Prof Wetterich has proposed that atoms are shrinking rather than the Universe is expanding. Here is a 2013 Nature News article describing his theory: https://www.nature.com/news/cosmologist-claims-universe-may-not-be-expanding-1.13379 Here is his 2013 paper "A Universe without expansion"...
  42. H

    B Newton's experimental law -- Questions about the collision of two spheres

    The following is from the 2018 AQA AS Further Maths/Mechanics Paper 2 exam: 'Two smooth spheres A and B of equal radius are free to move on a smooth horizontal surface. The masses of A and B are m and 4m respectively. The coefficient of restitution between the spheres is e. The spheres are...
  43. Dadface

    I Experimental confirmation of the Born rule

    If we assume that a particle can be detected at a particular location, how can we do the detecting?
  44. G

    Plotting experimental results on resonant frequencies

    These are the questions that I can't figure out how to do. I have been assigned a lab report based on resonating frequencies on a string and am having trouble completing some of the questions in the report. This is what i currently have from the previous steps required. A bit of info...
  45. C

    I Low p_t cuts in experimental measurements

    Just few questions based on experimental presentation of results: In (semi-)inclusive measurements (say, p + p -> Y + X), producing some well defined state Y and the rest, X, summed over, is there typically a minimum cut made on the p_t of the state Y? If so why? What is the reason of...
  46. Admiralibr123

    I Looking for Experimental Data on Isotopes (Nuclear Physics and Engineering)

    So, a website in which I just enter an element or an Isotope and it just lists all the relevant experimental data like mass, mass-defect binding energy etc. Also resources for the absorption data, resources to explore Monte-Carlo simulations, and other calculation tools would be awesome. Just a...
  47. I

    Significant Figures with Experimental Values

    I was thinking of choosing 0.740, because it looks the most consistent with the other numbers because they all have a trailing zero. But then, in accordance with sig figs, 0.74 is the right answer. Which one should I choose? Thank you so much!
  48. C

    I Find Experimental Results for Physics Project

    I'm a physics student in undergrad. For a project in our class in which we propose an experiment (which we will not actually perform and we can use resources we don't have access too for the "experiment") and base it on existing research for that topic. I am searching on ads and arxiv, so far I...
  49. S

    Measuring Agreement Between Experimental Values of Constant k

    Hello folks, Not strictly a homework question, but thought this might be the best place for it. If I determine (experimentally) two values for some constant k, is there a simple meaningful way to state their (percentage) agreement. For example, imagine I carry out two different experiments and...
  50. L

    B How does the double slit experimental apparatus actually work?

    So when explaining the results of quantum double slit experiments that have evolved from the classical wave double slit experiment, popular lecturers of quantum mechanics often show an animation of an electron gun or photon source shooting a lot of particles towards a double slit. The effect is...
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