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.

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  1. T

    I Ratio of abundance of sub-atomic particles in the universe?

    I was wondering if there is a current hypothesis about the quantities of which matter particles were created? I'm not completely au fait with the standard model, but I've seen the picture...
  2. heartshapedbox

    Collision of Two Particles: Conservation of Momentum and Final Velocities

    Homework Statement A particle of mass 5.0kg travels initially with a velocity of 8.0mˆı and then interacts with a particle of mass 6.0kg which was initially at rest. After the interaction the 5.0kg mass travels at a speed of 4.0m/s along a direction which makes an angle of 53◦ with the x-axis...
  3. E

    I Energy of a number of particles

    Hello! It is sometimes useful to find the average energy of a certain number N of particles contained in a box of volume V. In order to find this quantity, the total energy is required and then divided by N. The result is E_{average} = \displaystyle \frac{1}{N} \sum_{n = 1}^{N} \left| a_n...
  4. S

    I Spin states for two identical 1/2 particles - Confused :s

    Im having trouble with my thought process for spin states of a system of two electrons Using Total Spin 'S' and Total spin mag quantum numbers 'MS' as state ket |S MS> My textbook states... " Three Symmetric Spin states Triplet spin stats for twin identical spin -1/2 particles | Up Up> = |S...
  5. LarryS

    A Is Phase Relevant for Uncharged Particles?

    Global phase invariance has been identified with the conservation of electric charge. Local phase invariance via the coupling of the wave function/field with the EM four-vector has been identified with charged particles interacting with the EM field. Am I correct in assuming that, except for...
  6. F

    I Virtual particles in Feynman diagrams and not

    I know some people here hate the subject of virtual particles. So I will try to narrow my questions. Granted, virtual particles are just attempts to describe the math and are not real in and of themselves. But there seem to be a couple of different kinds of virtual particles (in the math)...
  7. A

    Exploring Thermal Effects: What Makes Particles Vibrate?

    I've recently begun studying thermal effects. I learned that thermal energy could be transferred within an object through conduction and from a distant object through radiation. (let me know if I'm wrong here) I also learned that when matter is heated, it's particles begin to vibrate, move apart...
  8. F

    B When are particles in a quantum state?

    These are just a few quick and simple questions. When are particles in a quantum state? Are they always in a quantum state in-between interactions, or once interacted with are they never in a quantum state again? At the instant of the big bang was everything in a quantum state? If so, what...
  9. A

    I Quantum field and mediating particles

    I'm not sure if I posted this in the right category, it's something that came up just after the quantum mechanics section so I just chose this one. I've come across something that I simply can not find an answer for on my own. I'm taking Modern Physics course and the last chapter is some...
  10. F

    I Do entangled particles exist in superposition?

    Perhaps someone can show me some simple math showing two states in superposition and entanglement so I can see how entanglement relates to superposition. Thanks.
  11. EdgyWaters

    Two particles collide, COM frame, relativistic velocities.

    Homework Statement 2-body, COM frame collision a+b ---> c+d E = Ea+Eb = Ec+Ed Show that dE/dPf = Vc+Vd Show that the answer is the same when the velocities are relativistic I don''t know how to work out the relativistic aspect of the question. Homework EquationsThe Attempt at a Solution E =...
  12. E

    Particles connected with a string

    Homework Statement Two particle of mass m each are tied at the ends of a light string of length 2a. The whole system is kept on a frictionless horizontal surface with the string held tight so that each mass is at a distance ‘a’ from the center P (as shown in the figure). Now, the mid-point of...
  13. A. Neumaier

    I Particles from a thermal source

    In the following, I want to consider both photons in a sharply focussed, monochromatic beam of light (''type P'') and electrons in an electron beam (''type E'') on the same footing. In the following, X is either P or E. If we only concentrate on the internal degrees of freedom, both kinds of...
  14. bcrowell

    Why not sterile particles as dark matter?

    It seems that the most popular hypothesis is that dark matter consists of WIMPs. Can the existing data be described with sterile particles rather than ones that interact through the weak force? Is the only reason to prefer WIMPs that they are predicted by SUSY? (To me, as a nonspecialist, SUSY...
  15. S

    Giant slalom of particles in a plasma?

    The charged particles of a plasma are either strongly repelled or attracted to one another. Am I correct in saying that they do a "giant slalom" around one another? And does this mean that the transfer of momentum in a collision is much smaller than in a neutral gas where the atoms/molecules...
  16. D

    Kinetic energy of two particles

    If light of certain wavelength falls on two particles say electron and a neutron(isolated) then since they are absorbing the same amount of energy their kinetic energy must be same. But using the formula: $$ \lambda = \frac{h}{\sqrt{2mE}} $$ we get $$ E = \frac{h^2}{2m \lambda^2}$$ which states...
  17. naima

    Can very distant particles be entangled?

    Entangled particles give no interference. What happens in the Fraunhofer approximation when the source of entangled pairs is far away? If it depends on distance what about the apparent collapse?
  18. avorobey

    Work and forces in systems of many particles

    I'm reading Goldstein's "Classical Mechanics", first chapter, and am confused about what's going on in equations of forces and work in systems of particles. For example, Goldstein calculates work done by all the forces, external and internal, in evolving the system from state ##1## to state...
  19. acdurbin953

    Determine the number of particles transmitted by S-G analyzer

    Homework Statement A beam of identical neutral particles with spin 1/2 travels along the y-axis. The beam passes through a series of two Stern-Gerlach spin analyzing magnets, each of which is designed to analyze the spin projection along the z-axis. The first Stern-Gerlach analyzer only allows...
  20. A. Neumaier

    Are tracks in collision experiments proof of particles?

    I'd like to discuss the question in the title, following up on my remark quoted below. Note that I don't want to repeat the discussion in https://www.physicsforums.com/threads/tracks-in-particle-detectors-and-quantum-paths.758778 so maybe reread that one first! The traditional analysis is...
  21. G

    A Creating mass (particles) from light

    As far as I know both mass and energy affects space-time. Mass creates a "sphere like zone of distortion", the space-time is less altered as we move away from the center. Photons on the other hand alter the space-time rather wave like, along the propagation trajectory and not "locally". Could...
  22. S

    Pathria page 2 -- total energy for mutually interacting particles

    In page 2 of Pathria's textbook on 'Statistical Mechanics,' it is mentioned that Consider the total energy ##E## of the system. If the particles comprising the system could be regarded as noninteracting, the total energy ##E## would be equal to the sum of the energies ##\epsilon_i## of the...
  23. R

    What evidence is there for electrons being particles?

    We know electrons can act as waves because of Young's Double split experiment, but what evidence is there to suggest they are particles?
  24. sciencejournalist00

    Can you name a few interactions that entangle particles

    It says everywhere that particle decay is not the only thing that creates entangled particles. "Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described...
  25. N

    Transverse waves and the movement of particles

    Homework Statement Alright, this problem has been driving me into a confused rage. The wave is moving in an upward direction so particle A should be moving up as well, right? But every single website I've used to study claims that it's moving in a downward direction. How? Homework...
  26. F

    Can particles be absorbed into a field?

    I am told that if an electric field is strong enough that it can polarize the vacuum enough to created positrons and electrons. Also, if quarks are separated enough, then the potential energy creates other quarks. My question is can the reverse happen, are particles ever absorbed back into a...
  27. A. Neumaier

    A Particles in quantum field theory

    In this thread, I want to discuss the implications of quantum field theory for the interpretation of quantum mechanics. To set the stage I'll import in the next few posts a number of posts from other threads. The latest of these is the following: Only if it is the sole particle in the whole...
  28. ayush solanki

    Does the mass of subatomic particles differ on different planets?

    Does the gravitational force of different planets affect it? I know about the higgs boson and so is that what gives a particle mass?
  29. sciencejournalist00

    The phase between 2 waves describing 2 entangled particles?

    Each particle has a wave associated to it according to the principle of wave-particle duality. Between two waves there is a phase difference. What is this phase difference in the case of entangled particles? 0 degrees? 90 degrees? 180 degrees? Somewhere in between?
  30. TristanJones

    Two Particles Collide - Momentum and Energy

    Homework Statement Q: A 3.000u object moving to the right through a laboratory at 0.8c collides with a 4.000u object to the left of the laboratory at 0.6c. Afterward, there are two objects, one of which is a 6.000u mass at rest. A) what are the mass and speed of the other object? B) determine...
  31. CivilSigma

    Separation of Particles in a fluid flow?

    Hello, I'm doing some online research on fluid flow in waste water treatment. One of the problem I'm trying to find information about is how can visible particulate matter be separated within a liquid. I saw the following picture: What fluid concepts are going here that allow the grit to...
  32. LarryS

    SR Kinetic Energy Mass Increase for Uncharged Particles?

    The mass of a particle will increase as its velocity increases according to special relativity. This has been confirmed in countless experiments in which particle accelerators accelerate charged particles. What type of experiments have confirmed this for uncharged particles? Thanks in advance.
  33. S

    Perturbation theory, Intermediate states, Virtual particles

    The following is taken from page 13 of Peskin and Schroeder. Any relativistic process cannot be assumed to be explained in terms of a single particle, since ##E=mc^{2}## allows for the creation of particle-antiparticle pairs. Even when there is not enough energy for pair creation, multiparticle...
  34. A

    Conserved quantities for massless particles (Schwarzschild)

    If a metric admits a Killing vector field ##V ## it is possible to define conserved quantities: ## V^{\mu} u_{\mu}=const## where ## u^{\mu}## is the 4 velocity of a particle. For example, Schwarzschild metric admits a timelike Killing vector field. This means that the quantity ##g_{\mu 0}...
  35. J

    Particles with electric charges visible to the human eye?

    Are there any particles known in the Physics world with an either positive or negative charge that can be viewed by the human eye under LED light illumination and have an attraction/repulsion to magnetism?
  36. irhum31

    Two colliding particles, finding ratio of M/m

    Homework Statement A particle of mass m and initial velocity v0 collides elastically with a particle of unknown mass M coming from the opposite direction as shown in the left-hand sketch on the next page. After the collision, m has velocity v0/2 at right angles to the incident direction, and M...
  37. A

    Newton's 2nd law for Massless Particles in SR

    I think I have never seen a force equation for massless particles, I wonder if such thing exist or if not why not?
  38. M

    Can radiation particles contribute to heat transfer in space?

    Freon is used every day to reduce temperature by compressing the gas then releasing the pressure. The Question is dose radiation from the sun (witch would be high pressure) steal energy from the objects it comes in contact with in space (witch is low pressure), Thus contribute to the loss of...
  39. J

    Can virtual particles exist without their counterparts?

    Hello, I was curiose as to if it is possible for a virtual particle to appear without its anti-mater/matter counter part. I posted a thread before asking about the existence and untimatly the "realness" of virtual particles. I concluded that they are real from the Casimir effect (i may have...
  40. T

    How do solute particles increase boiling point?

    The question is: Which solution listed below is going to have the highest boiling point? A. 1.5 m NaCl B. 1.5 m AgCl C. 2.0 m C6H12O6 D. 2.0 m CaCl2 E. 1.0 m Al2(SO4)3 I chose D (which was right) because in a solution, the more solute particles there is the higher the boiling point (this is...
  41. Coffee_

    When is the total C-parity of two particles the product?

    Let's say I have two particles A and B and I want to find the total charge parity of the system ##C_{AB}##. In what cases is it allowed to say ##C_{AB}=C_{A}.C_{B}##? I suspect that if A and B are their own antiparticles, then that is OK. Is this even the case when the system has a relative...
  42. G

    Light interaction with charged particles

    Does anybody know what happens when say a laser accelerates charged particles? Do photons get absorbed and the intensity of the laser drops, or do they get absorbed and scattered and there's a redshift of the photon etc
  43. D

    Materiality of elementary particles

    Do elementary particles, e.g. electron, protons, etc, have material substance in the ordinary meaning of substance? If so, what is the substance?
  44. O

    What is an elementary particle?

    When my eighth grade daughter was studying physics in her class, I watched a movie with her on the Hadron Collider (" Particle Fever "). We discussed atoms, electrons, protons, neutrons; we discussed orbits and statistics, and then down into the standard model and fermions, leptons, yadda...
  45. F

    Show particles are scattered at right angles in the CM frame

    Homework Statement Suppose that in a fixed-target proton-proton collision, the two protons are scattered with equal energies at equal angles θ/2 to the beam. Show that in the CM frame, this implies they are scattered at right angles to the direction of the beam. Calculate the energy and...
  46. LarryS

    Gauge Invariance for field of *Uncharged* particles?

    A complex classical field Φ of particles is, by itself, invariant under global phase changes but not under local phase changes. It is made gauge invariant by coupling it with the EM potential, A, by substituting the covariant derivative for the normal partial derivative in the Lagrangian. But...
  47. J

    I Are virtual particles real or just math filler

    Hello, My question on virtual particles is quite simple but I cannot find an answer. Are virtual particles just a filler for math or do they actually come into existence?
  48. S

    Understanding the Role of Degrees of Freedom in 1-Dimensional Random Walks

    Hello! I'm struggling with a probably easy physics question concerning random walks. Here I have the slide regarding this: Delta is the distance that a particle moves. Can someone explain where the n-1 initially comes from? Does it have to do wtih the concept of the degrees of freedom? Than...
  49. Islam Hassan

    Elementary Particles: Wave-Like Nature vs Travelling in Wave

    When we say that elementary particles are wave-like in nature does that encompass, lead to and necessarily imply the fact that they travel in wave-like trajectories or is wave-like displacement a separate, distinct notion from their wave-like intrinsic natures? IH
  50. B

    Why are particles in QFT assumed to be point-like?

    Why are particles in QFT assumed to be point-like? This assumption is the source of ultraviolet divergences. Does anyone know what is the source of this assumption, and what happens if you assume that particles are not point-like?
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