What is Particles: Definition and 1000 Discussions

In the physical sciences, a particle (or corpuscule in older texts) is a small localized object to which can be ascribed several physical or chemical properties such as volume, density or mass. They vary greatly in size or quantity, from subatomic particles like the electron, to microscopic particles like atoms and molecules, to macroscopic particles like powders and other granular materials. Particles can also be used to create scientific models of even larger objects depending on their density, such as humans moving in a crowd or celestial bodies in motion.
The term 'particle' is rather general in meaning, and is refined as needed by various scientific fields. Anything that is composed of particles may be referred to as being particulate. However, the noun 'particulate' is most frequently used to refer to pollutants in the Earth's atmosphere, which are a suspension of unconnected particles, rather than a connected particle aggregation.

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

    Kinematics Problem -- 3 particles at the vertices of an equilateral triangle

    Here's the question: Three particles A, B and C are situated at the vertices of an equilateral triangle ABC of side d at time t = 0. Each of the particles moves with constant speed v. The particle at A always has its velocity along AB, B along BC and C along CA. At what time will the particles...
  2. P

    Forces between charged particles

    Homework Statement Suppose the magnitude of the proton charge differs from the magnitude of the electron charge by a mere 1 part in 109.What would be the force between two 1.7-mm-diameter copper spheres 1.7cm apart? Assume that each copper atom has an equal number of electrons and protons...
  3. arivero

    Continuous symmetries as particles

    I am not sure if I recall all the ways for a symmetry to appear as some particle in a Quantum Field Theory. - The Lagrangian and the vacuum is invariant under the generators of a global symmetry/gauge group. Then the particles in the theory are classified according representations of such...
  4. 7

    Particles as the quanta of fields

    Quantum field theory deals with the quantization of the electro-magnetic field, and finds its quantum: the photon. Electric and magnetic fields are classical fields. Can QFT quantize also them, and find their quanta? It is often said the electrons are field quanta (particles are quanta)...
  5. DivergentSpectrum

    Determining "boundedness" of particles in an n body simulation

    is there a numerical method to determine whether two bodies will stay bounded forever in an n body simulation? i know if the energy of a particle orbitting the origin is negative, then it is bounded, where -∫(force)dr+(dr/dt)2/2=energy. but I am curious about a genereral case, where there are...
  6. M

    Photons interacting with multiple matter particles

    Everyone learns the picture associated with e.g. the Balmer series in Hydrogen: a photon with a precise energy flies in and is absorbed by an electron which is excited into a higher energy state, which then decays to the ground state, re-radiating a photon of that precise frequency. If we...
  7. arivero

    Sum of spin for chiral particles?

    How does the spin of a pair of particles work if both particles are known to be chiral? generically if I sum the spins of two different (EDIT: spin 1/2, indeed ;-) particles I expect to get a triplet with S=1 \uparrow\uparrow, \uparrow\downarrow+\downarrow\uparrow, \downarrow\downarrow and...
  8. T

    Particles on the surface of an atom?

    There are many particles inside an atom. What particles make up the surface of an atom? When we see graphical illustrations of spherical atoms, what are we actually seeing?
  9. J

    Connection between particles a field in string theory

    Im a trying to understand how the string entity relates to its underlying field. Is the field a brane and the string the partice?
  10. S

    How do virtual particles mediate?

    As far as I know, forces are supposed to be mediated by virtual particles. Let's take the example of a magnetic field, mediated by photons. This seems to be a good idea, because it sort of eliminates the nasty concept of a field, which is just an abstract concept. This has been bothering me...
  11. stevendaryl

    Free Fractionally Charged Particles

    It is intriguing (to me) that while fractionally charged particles exist in the standard model, they are always bound into composite particles of integer charge. The standard model explains this by QCD: fractionally charged particles all have nonzero color charge, and so can't be free. But I'm...
  12. Delta2

    What is the mathematical basis for understanding the wave property of particles?

    The wave property of particles (like electrons) is due to : 1) The wave function 2) The underlying fermionic field 3) Just because of the existence of de broglie waves? Or maybe someshow the above three cases are unified ?
  13. P

    Interaction of photons with charged particles

    Can someone please tell me the name of the theory describing the interaction of photons with charged particles eg electrons, protons? Can you also suggest a good introductory web page describing that theory at First Year University level for self study? Better still, a good VIDEO lecture on...
  14. A

    Are composite particles, like atoms, identical bosons/fermions?

    I have seen only two arguments for the fact that composite particles, like protons, nuclei, or even Helium-4 atoms, are identical and can be considered bosons or fermions according to their total spin. The first, in Feyman's lectures [third volume, 4-2]. It is said that if the composite...
  15. M

    Center of mass for two small particles

    1. Two small particles of mass m1 and mass m2 attract each other with a force that varies with the inverse cube of their separation. At time t0 , m1 has velocity v directed towards m2 , which is at rest a distance d away. At time t1 , the particles collide. How far does m1 travel in the time...
  16. T

    Identical particles and Feynman diagrams

    In Introduction to QFT (peskin) 4.5, he writes: The computation for M, of course, will be quite different when identical particles are present. However, I have finished reading the first part of the book and found no special treatment for identical particles. Can anybody tell me how to...
  17. J

    What happens to particles in synchrotron accel. if weak magentic field

    Homework Statement "Describe what might happen to the particles in the accelerator if the magnetic field was too weak." Homework Equations N/A The Attempt at a Solution I am merely guessing here. I am looking on the internet for info regarding this but I can't find anything...
  18. atyy

    Are Particles or Fields More Fundamental in Quantum Mechanics?

    This thread continues the discussion at https://www.physicsforums.com/showthread.php?t=767018
  19. LarryS

    Spin Direction for Massless Particles

    Mass-less particles travel at the speed of light. If such a particle has an intrinsic spin, the DIRECTION of the spin angular momentum vector must be in the same direction as the linear motion of the particle. Why exactly is that? Thanks in advance.
  20. S

    Erwin Schrödinger Ghost Particles & Energy of Molecules & Atoms?

    Hello there. I did research on some of Schrodinger work. My question is the transfer of Energy between the Atoms and Molecule. Schrodinger made an analogy with the Cat/Atom Scenario but the real particle in question is the NH2 Mole & H-Atoms with ghost energy being observed. The reason I read...
  21. M

    Can we "fill" an atom with alpha particles?

    The following passage has been extracted from the book "Modern's abc of Chemistry": Lets fill an isolated atom by subatomic "Rutherford projectiles"-alpha particles. I hope it is possible. This doesn't seem to be a limit of our technology. Isn't it? If we are successful in...
  22. T

    Are subatomic particles spherical?

    We are very used to see diagrams of atoms as being composed by little spheres each one with their own characteristics, such as mass, electrical charge, etc. I have also read and heard in many different scientific divulgation media about the scale of the nucleus’ dimension and the size of...
  23. T

    Gravitational effect of virtual particles

    If virtual particles are constantly popping in and out of existence all around us, what gravitational effect does this have? Even if they are here for the briefest of moments they should be effected by gravity and have their own gravitational effect on other matter...shouldn't they?
  24. J

    "Natural" vs. Laboratory Particles

    Of the 61 known elementary or fundamental particles, which ones exist in the everyday, "natural" world of the Earth, and which have been created or only found among laboratory experiments? The 61: red/blue/green up/down/strange/charm/top/bottom quarks and their antiparticles make 36...
  25. T

    The formation of shockwaves and the role of Alpha particles in ICF

    I have three questions about ICF, in the explanations i have read on the internet about ICF they all explain that the top layer of the pellet or the ablator is heated till it explodes and produces a reaction force which compress the D+T fuel. They then say shock waves are formed due to the...
  26. M

    What is <x_1-x_2> for two particles in a 1-D harmonic oscillator

    if we have two non-interacting particles of mass M in a one-dimensional harmonic oscillator potential of frequency ω, with the wavefunction defined as: $$\Psi\left(x_1,x_2\right) = \psi_n\left(x_1\right) \psi_m\left(x_2\right)$$ where x_1 and x_2 are two particle co-ordinates. and ψ_n is the...
  27. Greg Bernhardt

    What are Virtual Particles? A 10 Minute Introduction

    Continue reading...
  28. A

    What is meant by moment of particles?

    What is meant by moment of particles ? Why the algebraic sum of moments of all particles about centre of mass must be zero ?
  29. ShayanJ

    How composite particles have definite spin?

    Consider a composite particle. Its spin is determined by the spins of its constituent particles. But the constituent particles are in a superposition of different spin states and so don't have a definite spin. So it seems it shouldn't be possible to ascribe a definite spin to the composite...
  30. H

    A Little Question On Identical Particles

    I am learning identical particles recently, but I have some problem interpreting what I am writing down. So if we have two distinguishable particles, absolute value of ψ(x_1, x_2) tells the prob. density of finding the first particle at x_1 and the second at x_2. But for identical particles, it...
  31. Prashasti

    Colloidal Particles and their size

    Suppose we have a cube, of length 1 metre. It is cut in all the three directions so that 8 cubes, each having 0.5 m as its length. Then, these cubes are again subdivided in the same manner to get cubes with length 0.25m and so on. HOW MANY OF THESE SUCCESSIVE SUBDIVISIONS ARE REQUIRED BEFORE...
  32. DiracPool

    Relative velocities of particles and photons

    According to my understanding of SR, a light photon traveling at c, of course, relative to me "experiences" no time. In other words, it is not traveling through, at least, the time dimension I am traveling through. A neutrino, say, moving close to c does, but it is traveling very slowly...
  33. C

    Three charged particles, finding the net force on each particle

    Homework Statement Three charged particles are placed at the corners of an equilateral triangle of side 1.20 m (see figure). The charges are Q1 = +3.5 µC, Q2 = -7.2 µC, and Q3 = -5.1 µC. Calculate the magnitude and direction of the net force on each due to the other two. (Assume the +x axis...
  34. B

    Parity of a system composed by 2 particles

    I have read that for a system of 2 particles, the total parity is given by: P=P_1 P_2 (-1)^L where - P_1, P_2= insisec parity of particle 1, 2 - L= relative angular moment what's the meaning of "relative angular moment"? Do I have to add the l numbers of the two particles? And what if I...
  35. J

    Dynamics of a system of particles all influencing eachother

    Take a closed system of particles. Each has it's own mass, but that's really about it for the sakes of this argument. Now suppose there is some standard force law that applies between particles, whatever it may be. (In general it will depend only on the separation between particles and thus be...
  36. M

    Poynting's theorem and escaping particles

    I was thinking the other day and it looks like I need feedback if I am being stupid or crazy. My question is quite simple - does Poynting's theorem cover the situation of charged particles escaping through surface (just like radiation part does) of the volume over which we calculate? I...
  37. T

    Electrostatics Problem -Two moving charged particles

    Two small particles have electric charges of equal magnitude and opposite signs. The masses of the particles are m and 2m. Initially, the distance between the particles is d, and the velocities of the particles have equal magnitude v. However, the velocity of particle 2m is directed away from...
  38. F

    Density of particles outside a constant point source

    Hi, I'm having a strangely hard time imagining how the distribution of particles would look around a constant point source in some scenarios. I came up wiith something that sounds reasonable to me, but would like a logic check. The easy one for me to grasp is distribution when the source...
  39. B

    Do Quantum Particles Generate Gravity Waves?

    when anything moves it displaces space and generates gravity waves, So does this also happen at the quantum level? quarks giggering about due to uncertainty in there possition (at least I think that what uncertainty does acording to explanations in popular science books.) gluons zapping about...
  40. U

    Effusion of particles from one box to another - pressure calculation

    Homework Statement Suppose we have a container divided into equal halves. Right half is fixed at temperature ##T##, volume ##V_2##. Initially it has pressure ##P_0##, a hole of area ##A## is opened between them. Part (a): Show that the pressure in the right half is: p =...
  41. S

    Synchrotrons and accelerating particles

    [b]1. in synchrotrons; as i understand, particles are only accelerated along the straight sections by an electric field established by electrodes. in my textbook, it says "a high frequency alternating voltage is applied between electrodes positioned around the ring which accelerates the charged...
  42. A

    Crystal Lattice of Spin-1 Particles: Chemical Potential?

    Homework Statement A crystal lattice consists of a spin 1 particle at each lattice point. Spin 1 particles can have z-components of magnetic moment that take on the values +μZ, 0, and -μZ. In an external magnetic field B, each spin can have an energy U = -μZB, so the possible energies are...
  43. E

    Can subatomic particles be PROVED to exist?

    I know that it can be proved that it works perfectly to assume that subatomic particles exist, but that's not really proof that they actually exist. Thank you.
  44. A

    Probability of a state containing n particles (Maxwell-Boltzmann)

    Homework Statement For a system of particles at room temperature (use kT = 0.026 eV), the energy of a single particle state is 0.01 eV greater than its chemical potential, so that ε-μ = 0.01 eV. Computer the average occupancy of this single particle state, as well as the probability of the...
  45. C

    What kinds of particles can decay to Lambda hyperons?

    Such as ##\Sigma^0 \to \bar{\Lambda}\gamma\gamma##. I want to make a complete collection of all these decay modes, i.e. ##X \to \Lambda / \bar{\Lambda} + \cdots##. At least some major channels.
  46. C

    Electric & Magnetic Fields: Charged Particles Difference

    What's the difference between electric and magnetic fields, specifically I someone was to send a charged particle into them? Are there any similarities?
  47. Islam Hassan

    Virtual Particles in Inter-Quark Space

    This oft-referenced picture depicts a simulation of virtual particles popping into and out of existence in the empty space inside a proton, ie between the quarks: http://bsturge93.files.wordpress.com/2014/02/empty-space.jpg?w=300&h=242 My question is whether the intensity of this popping...
  48. R

    Color of Microscopic Particles?

    Do molecules, atoms, and subatomic particles have color? If so, what? Is it even possible to determine if they do or not (Can electron microscopes see electrons?)? Is color even relevant at lengths this small? I would elaborate more but these questions are fairly straightforward.
  49. J

    Find the mean number density of particles in the stellar atmosphere.

    Homework Statement The atmosphere of a star has a mean radiation pressure of 0.33 N m-2and a mean gas pressure of 8300 N m-2. Calculate: a) the mean number density of particles in the stellar atmosphere, and b) the radiation pressure in a stellar atmosphere with twice the effective...
  50. W

    How particles interact with the Higgs Field?

    Reading around gives me some idea of WHY particles interact with the Higgs field but not How! I am looking for a model that I can use to explain the process to my High school students. Can anyone help please. John
Back
Top