What is Experiment: Definition and 1000 Discussions

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

    Experiment to determine the time period of a pendulum

    Homework Statement Homework EquationsThe Attempt at a Solution Time period of a simple pendulum is given by 2π√(L/g) . By uniform mass distribution , I am assuming density of mass of bob to be constant . I don't understand how time period depends on the mass of the bob of a simple pendulum .
  2. Phillane

    I Delayed Choice / Quantum Eraser Experiment Question?

    Hello, Disclaimer: I have read other posts and understand it is important to reference ‘sources’ and that popular science articles / videos can be a source of annoyance. However, I am struggling to: A. Find an answer to my question, and/or B. Understand if my question is even valid. I hope...
  3. ElanaC

    B Double slit experiment question

    Hi, I have two questions concerning the double slit experiment in the scenario where we fire one photon at a time and it interacts with itself to create an interference pattern over time: - Does the photon actually interact with itself or with the photons fired before/after it? - What happens...
  4. D

    B What is the result of putting a detector on both slits in the 2 slit experiment?

    In the 2 slit experiment , what would be the result if we put a dedector on both slits? would we get an interference patern?
  5. A

    Setting Up an Experiment: Force vs. Displacement

    Homework Statement I'm trying to figure out the setup of an experiment I have to complete. The experiment calls for a rubber band to be secured by rods on the sides, and for a clothespin to be attached to the rubber band. I have to figure out how far back the clothespin needs to be pulled down...
  6. A

    A Decoherence in the double slit experiment

    I have two questions about the following type of scenario: We have a laser sending photons through the usual double slit apparatus giving us the usual interference pattern, except that now we introduce some physical matter (that are not photons) that the photons will interact with before going...
  7. Alfredo Tifi

    I Why isn't the Roemer type experiment a one way measure of c?

    I can't read the tons of posts and replies about one-way light speed in this forum. I was criticised once for sustaining light speed should be equal in both outward and return trips and Einstein's method of syncing clocks as the only reasonable one. Then I studied some scientific articles gently...
  8. Kostik

    I Does measurement destroy the interference pattern in the 2-slit experiment?

    I realize the 2-slit experiment is discussed at the beginning of countless QM books and YouTube videos. I have read the excellent exposition in the first chapter of Feynman & Hibbs, and appreciate that (using Feynman & Hibbs language): A. any determination of which among various alternative...
  9. K

    B Preserving local realism in the EPR experiment

    What is wrong with the idea that the spooky correlation in the EPR experiment is simply the result of the initial difference in rotation between the two polarizers in this experiment? So if you rotate one of the polarizers relative to the other polarizer, that initial act of rotation is what...
  10. ohwilleke

    I Anomaly aggregation and confirming old paper validity

    The Particle Data Group keeps a running, subject matter organized summary of the state of the art experimental results for the experimentally measured properties of hadrons and measurements of fundamental physical constants that is updated at least annually. Is there any comparable group that...
  11. T

    Magnetic field experiment confusion with error calculations

    Homework Statement I am having a issue with calulating my errors for this particular experiment the reason I will detail below. I have also print sceend in the section of my lab report to show the experimental setup etc. Lab Script So in the lab during the experiment the tesla meter...
  12. S

    Millikan Oil Drop Experiment: Determining Elementary Charge

    Homework Statement Calculate the charge on each oil drop and determine the elementary charge on an electron given the following: Voltage (Attached) d (Distance between two charged plates) = 0.10m m (Of the droplet) = 1.57x10^-15 kg g = 9.8 kgm/s^2 Homework Equations q = mg*d / ΔV The Attempt...
  13. G

    Need help with a thought experiment about a Faraday generator

    Hi, I arrived at a paradox today which I cannot explain myself. I was watching some physics videos on youtube and among them some were about lenz law and faraday disc workings. Now I know and understand the classical examples of why there is current generated when the magnet moves together with...
  14. J

    B Kim et al, 1999 experiment and causality

    Hi everyone! Sorry for my bad English! I read old posts in this forum, googled it and still can't figure out one thing: What other explanation could there be, other than a random event in the future determined if the photon behaved as a particle or wave in the first detector? Thanks a lot! I...
  15. B

    B Do Hot and Cold Air Balloons Fall at the Same Rate?

    Certainly a wooden ball and a stone fall with the same velocity. Would a balloon of cold air fall with the same velocity as a balloon of hot air? As a corollary, why does hot air rise over cold air? If you claim that cold air is denser, then the same argument fails when you compare a wooden...
  16. O

    I Concept underlying recent Serra-Lutz cold-to-hot experiment

    Hi, I'm trying to understand in a simple, non-mathematical way the basic concept underlying why a particular, very recent experiment turned out the way it did. The experiment, by Serra and Lutz entitled 'Reversing the thermodynamic arrow of time using quantum correlations', demonstrated an...
  17. MichPod

    I Modified double-slit experiment - two photons

    On the following link https://physics.stackexchange.com/questions/183961/modified-double-slit-experiment-two-electron-sources-instead-of-two-slits there is a discussion of the modification of double-slit experiments where two electrons sources are put in place of the slits. The conclusion is -...
  18. S

    Variables in a lab (controlled, independant and dependant)

    Hi! So it's new for me to do physics lab that way and my teacher is asking us to define the independant, dependant and controlled variables of every lab we're doing. I'm not quite sure what they refer to... For example, in a moment of inertia lab (see picture), I am asked this question. The...
  19. ohwilleke

    I Is there a fine structure constant running anomaly?

    Background The chart above, via Lubos Motl's blog which is standard in any textbook talking about supersymmetry, illustrates the running of the the inverse of the Standard Model (SM) and Minimal Supersymmetric Model (MSSM) coupling constants with energy scale for the electromagnetic force...
  20. MathematicalPhysicist

    A A technical question about the Joule-Thomson Experiment

    It's written in Kubo's textbook: I tried getting (2) from (1), but I get something different, I get: ##T\partial V / \partial T - V = TR/p+TRB+RT^2dB/dT-RT/p-RTB = RT^2dB/dT##, how to resolve this conundrum? Thanks.
  21. P

    B Geiger's Gold Foil Experiment: Exploring Atom Structure

    Hi, I'm confused a little about the gold foil experiment. I tried to put myself in Geiger's shoes, the author of the experiment. I'm firing alpha particles at a gold film, given that the plum pudding model is the pinnacle of human understanding of the atom, meaning I believe matter is made of...
  22. nomadreid

    I Exploring Malament-Hogarth Spacetime: Simplified Alice/Bob Experiment

    The article https://en.wikipedia.org/wiki/Malament%E2%80%93Hogarth_spacetime, the possibility of a space with a "worldline λ and an event p such that all events along λ are a finite interval in the past of p, but the proper time along λ is infinite" is discussed, and the suggestion is made that...
  23. Frenchies

    Help replicating Eratosthenes' experiment

    Hello, we are Maylis, Clara and Hélèna. We are students from a french high school in a class of «première scientific» (french equivalent of 11th grade) This year we have to be marked on Science more precisely on Physics. As a subjet we choose «the roundness of the earth: how Science is used to...
  24. K

    Why Does My E/M Experiment Graph Have an Unexpected Y-Intercept?

    So I am doing the charge to mass experiment and determining the relationship between: 1. accelerating voltage and radius formed by the electron beam 2. magnetic field strength and radius formed by electron beam Theoretically I should obtain an equation of the form: r = (1/B) *sqrt(2mV/e) where...
  25. J

    B Alain Aspect's experiment setting

    Hi everyone! Sorry for the bad english. I'm a psychologist from Brazil, so I don't know much of physics nor English. I'm having a hard time understanding his setting. In a very simple way, he made two entangled photons, each went to a polarization analyzer, that was set to random positions...
  26. S

    Fraunhofer diffraction experiment- neural density filters

    I'm currently carrying out an experiment with Fraunhofer diffraction. It involves shining a laser beam through neural density filters, a lens and a diffraction grating, to create a diffraction pattern which is then picked up with a CCD camera, to find the intensity of the maximal peaks. However...
  27. F

    I Confusion with the Photoelectric Experiment

    I've always struggled with circuits and never got a firm handle (hence the very basic questions...please bear with me). What I understand of Lenard's Experiment: Light hits the emitter plate and some electrons fly off. ...lol yeah that's about it. Here is one major confusion that I have: Not...
  28. T

    Millikan's experiment -- data confusion

    Homework Statement Hi guy I am having a real issue trying to find the fundamental charge from my data. So here is the background. Basically I carried out and experiment where we measured an oil droplet the was floating a specific voltage by taking the measurement of 12 oil droplets and...
  29. esha

    Penny on a card experiment.... explanation

    A card kept on a glass with a penny is jerked. The coin falls in the glass while the card moves away. why is that? My attempt at an explanation A force acts on the card which is greater than the static friction acting between the card and the coin. Hence the coin is able to overcome that...
  30. DaTario

    Fringes in a One Slit Experiment with a water tank

    Hello All, I would like to know why it´s so difficult to find information about the generation of fringes in a one slit interference experiment in a water tank. Best Regards, DaTario
  31. Z

    What errors did Rutherford encounter in his experiment

    Homework Statement What errors did Rutherford encounter in his experiment and how did he account for them. Homework Equations I believe there is an equation to find (b) but I don't know what it is.
  32. M

    Relativity: Initial velocity and e/m of Thomson's experiment

    Homework Statement In an experiment similar to Thomson’s, we use deflecting plates 5 cm in length with an electric field of 1.0×10^4 V/m. Without the magnetic field, we find an angular deflection of 30°, and with a magnetic field of 8×10^-4 T we find no deflection. What is the initial velocity...
  33. R

    I Two slit experiment w baseballs

    Would it be theoretically possible to perform a two slit experiment with, say, baseballs? How would such an experiment need be set up?
  34. K_Physics

    Relative Intensity of Various Light Sources - Lab Experiment

    Homework Statement I've linked my data table down below. My problem is the relative intensity column. From the table, the units of relative intensity are w/m/s. I'm assuming this is power/velocity, where velocity is the speed of light. However, nowhere in the lab manual did it mention the...
  35. B

    I Concerning concioussnes and the double slit experiment.

    Hello there, I have a question about the double-slit experiment and conscioussnes. Excuse me if I don't formulate things right and might come over as a total fool for asking this (English is not my native language and i don't study physics). I just saw this video: <Moderator's note: link...
  36. I

    Limitations of Young's double slit experiment

    Homework Statement From a procedure standpoint, our experiment consisted of a laser pointer on a retort stand with a holder, shining through a piece of sheet with slit measurements (I believe it's acetate) and measuring the height of the maxima on a whiteboard. What could be improved with this...
  37. I

    B What are some limitations to Young's Double Slit Experiment?

    From a procedure standpoint, our experiment consisted of a laser pointer on a retort stand with a holder, shining through a piece of sheet with slit measurements (I believe it's acetate) and measuring the height of the maxima on a whiteboard. What could be improved with this experiment?
  38. I

    B Slit Distance - Young's Double Slit Experiment

    I understand Young's Double Slit Experiment, which basically consists of pointing a laser through two slits and seeing the maxima with different brightness, caused by constructive and destructive interference respectively. Through the experiment, I know that increasing the distance between the...
  39. R

    B Some very basic questions around the double slit experiment

    I have a few basic questions about the double slit experiment and was hoping someone might be able to answer them. 1) How far apart from each other would have I have to make the slits so effectively no detection took place? E.g. is there a limit to how far the wave function can spread and a...
  40. C

    B How Does Detector Placement Affect Ratios in the Double Slit Experiment?

    Here is a setup that only uses fixed detectors. Will the ratio between the number of detections at D0 and the sum of the numbers detected on D1 and D2 be close to 1? For this question instead of the coincidence counter, 3 simple counters are needed. Also the detectors D1 and D2 need some lenses...
  41. Mason Smith

    Millikan's Oil-Drop Experiment: Is my reasoning correct?

    Homework Statement Show that the electric field needed to make the rise time of the oil drop equal to the its field free time is ε = (2mg)/q Homework Equations Newton's second law F = ma The force of gravity FG = mg, where g = 9.8 ms-2 The force of buoyancy Fb = bv The force of an electric...
  42. J

    I Find a calculation of Schrödinger's cat experiment?

    Hello, does someone know where to find a calculation of Schrödinger's cat experiment? (like psi(cat)=|dead> + |alive>...)
  43. Alexander350

    Significant figures in a results table

    Homework Statement Basically there is a results table for the time taken for 20 oscillations. Three examples are 9.90, 11.16 and 12.68. I need to work out the time period to the correct number of significant figures. Homework EquationsThe Attempt at a Solution I divide by 20 to get the time...
  44. arpon

    I Experiment: Spin Rotation Operator

    How do we experimentally apply the operator ## \exp{\left(-i\phi\frac{ S_z}{\hbar}\right)}## on a quantum mechanical system? (Here ##S_z## is the spin angular momentum operator along the z-axis) For example, on a beam of electrons?
  45. C

    I Michelson Morley experiment: relativistic explanation

    I don't uderstand how, using special relativity theory (time dilatation and length contraction), one can explain why in the Michelson interferometer there is no delay between the two rays in the reference frame where the interferometer is moving. Consider the picture ##2.## Setting...
  46. K

    B Photon detection in the EPR experiment

    In the photon version of the EPR experiment, how is the final polarization state of the photon detected? I have read a number of high level descriptions of the EPR experiment, but I am having trouble with understanding the detection part. Here is my understanding, please correct me where I am...
  47. Buzz Bloom

    I Models of accretion disc emissions contradicted by experiment

    Ref: http://www.spaceref.com/news/viewpr.html?pid=51416 I would be very interested to see comments from knowledgeable people about this. My impression is that this is one more example of a need to remain at least somewhat skeptical about theoretical models that have not yet been validated by...
  48. J

    Why does my experimental value of g differ greatly?

    Homework Statement Hi, I did an experiment where I launched a soccer ball into projectile motion with my hand and took a video the situation. I uploaded it into the Tracker software to analyze it. The tracker software gave me a x-t graph, a y-t graph, and a y-x graph. From the y-t graph...
  49. U

    I Local, non-realistic description of the EPR-Bohm experiment

    I propose for your consideration the following version of this experiment: We have a source, S that produce pairs of spin 1/2 entangled particles and two detectors, A and B that measure the spin of those particles. The detectors are oriented on the same direction, say X and they are fixed. As...
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