What is Dust: Definition and 181 Discussions

Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes is composed of about 50% dead skin cells. The rest, and in offices, and other human environments is composed of small amounts of plant pollen, human hairs, animal fur, textile fibers, paper fibers, minerals from outdoor soil, burnt meteorite particles, and many other materials which may be found in the local environment.

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  1. R

    Mystery Generation of Dust Patterns from Grinding Wheels -- I can't explain it

    I'm not sure where to post this, but I wanted to show this just because of the incredible nature of the phenomenon. It's just the dust from a slow running wet grindstone. I assume just vibration, but the more carefully you look the more unbelievable it becomes. As the grindstone ran, some of...
  2. Evo

    And another one bites the dust

    Mysteries at the museum, on the Travel Channel started out discussing the history of items at museums. It was interesting and supposedly factual. Last year they added "Mysteries at the Castle" which had interesting stories/myths about old castles. Ok, now they added "Mysteries at the National...
  3. slatts

    Is the Multiverse of Cantor Dust a Viable Solution to Olbers' Paradox?

    At my Wikipedia-minus-math level of understanding, the problem with any resolution of "Olbers' Paradox" through a fractal distribution (such as the "Cantor set" depicted in the Wikipedia article of that name) of stars or star clusters, rather than the alternative of a beginning of our multiverse...
  4. S

    Scattering on dust particle

    Homework Statement We scatter a roentgen light with ##\lambda =\frac{2a}{\sqrt 7}## on a particle of dust of a crystal, with cubic crystal lattice as shown in the attached image. a) Calculate geometric structure factor. Calculate with cubic primitive cell. b) At which scattering angles do we...
  5. nsaspook

    Is Radio Shack's Liquidation Sale a Sign of Corporate Dominance in America?

    http://www.wsj.com/articles/radioshack-store-closings-to-jolt-some-developers-1423095564
  6. Heisenberg1993

    Event Horizon in a closed, matter (dust) dominated universe

    Hi! It is stated in V. Mukhanov's book "Physical foundations of Cosmology" the following (page 44, after equation 2.25): "In contrast, for the dust dominated universe, where ηmax=2π, the event horizon exists only during the contraction phase when η>π." could someone please explain why is this...
  7. T

    A speck of dust that carries charge in a electric field?

    A speck of dust has a mass of 1 x 10-18 kg and carries a charge equal to that of one electron. Near to the Earth's surface it experiences a uniform downward electric field od strength 100NC-1 and a uniform gravitational field of strength 9.8Nkg-1. Draw a diagram which shows the electric field...
  8. AotrsCommander

    Magnetosphere and space dust problems

    (I am of two minds about posting this here or in the main satrophytsics forum, but I think it's probably better to go here.) So, I have a tide-locked planet at approximately 104AU out around a clone of R Coronae Borealis, with has a carefully designed , bright shiny silvery moon (small and...
  9. Chronos

    Planck dust modeling and BICEP2

    Planck dust modeling has been released [re: http://arxiv.org/abs/1409.2495] . It appears to be consistent with the assumptions of BICEP2, but, that is an unsupported assumption. I expected an immediate reaction from the BICEP2 team, or other interested parties. Perhaps I am merely impatient, or...
  10. Chronos

    Andromeda vs Milky Way dust emissions

    As many are aware, the announced detection of primordial gravity waves by BICEP 2 was heavily criticized based on dust emission modeling. Today, Planck XXV was released which mapped out the dust emissions of Andromeda. Assuming Andromeda is representative of the Milky Way in most relevant ways...
  11. MTd2

    BICEP & Planck: Estimating Polarized Galactic Dust Emission

    To estimate polarized emission from the galactic dust, BICEP digitized an unpublished 353 GHz map shown by the Planck collaboration at a conference. However, it seems they misinterpreted the Planck results: that map shows the polarization fraction for all foregrounds, not for the galactic dust...
  12. M

    How do you solve a non-linear ODE involving a variable mass dust particle?

    Homework Statement At time t=0 a dust particle of mass m_0 starts to fall from rest through a cloud. Its mass grows exponentially with the distance fallen, so that after falling through a distance x its mass is m_0exp[αx] where α is constant. Show that at time t the velocity of the particle...
  13. Averagesupernova

    Dealing with Dust Mite Allergy: Questions Answered

    Just found out I am allergic to dust mites. This news explains a lot in my health as of the last several years. Does anyone deal with this? I would appreciate any input on how to deal with what would seem like a losing battle concerning bedding. I can deal with getting rid of all the carpet...
  14. tom.stoer

    E.o.m. for a particle in a sphere of dust

    I am looking for the e.o.m. of a particle moving inside a sphere of homogeneous dust with density ρ. I start with the Lagrangian (in cartesian coordinates with i=1,2,3) L = \frac{m}{2}\dot{x}_i^2 - \frac{4\pi}{3}Gm\rho x_i^2 The e.o.m. and their solution are given by the harmonic...
  15. S

    Mars rocks covered with uniformly thick dust layer?

    Hello all, I need your help. (I believe this si the correct forum) Between 2011 and 2013, i read a news in internet, that the dust that coveres rocks in Mars seem to be very uniform, like all rocks that was drilled by Mars science laboratory twin rovers, seem to have the same thickness of...
  16. B

    A dust particle through an electric field

    Homework Statement A small piece of dust of mass m = 3.8 mu or micro g (micrograms) travels through an electric air cleaner in which the electric field is 526 N/C. The electric force on the dust particle is equal to the weight of the particle. (a) What is the charge on the dust particle...
  17. S

    Dust Off Your Resume: Tips, Formats & More

    I have found myself back in the unemployment pool recently. I realized that it was time to dust off my resume and start the job hunt once again. It has been a few years since I have been in the need of employment, but off I go once again. Since I have to get get back in the game and dust off my...
  18. OmCheeto

    News Yay Another Xmas bomber bites the dust.

    I just heard this on the radio. We had a local try and do this a few years ago. I, for one, am glad someone is watching the crazies.
  19. Y

    Spherical GR dust shell with vacuum inside and outside

    In various other threads we have been kicking around various equations for a spherical shell and discussing the implications. In this thread I would like to present what (I think) I have worked out about how the shell metric relates to the vacuum metric inside and outside the shell. I hope to...
  20. Y

    Clocks inside a cavity inside a collapsing dust shell

    Consider a perfectly spherical dust shell with a large internal cavity. Imagine there is a moment when the dust is momentarily stationary and there is a string of clocks strung out along a radial axis. At this instant, I will assume that the spacetime inside the cavity is flat and all the clocks...
  21. A

    Coal Dust Contamination: Environmental Concerns and Impact on Waterways

    First I'm hoping this is in the right section. There is a big debate in the high plains of the Rockies and the Pacific Northwest about coal being transported by rail in open top hopper cars. The debate seems to center on coal dust and bits of coal making its way into the water ways. As far as...
  22. Z

    Magnetic sphere moving through iron dust; find velocity & other things

    Homework Statement A small magnetic sphere of initial mass Mo and initial radius Ro is moving through a space filled with iron dust. During its motion, 5% of displaced dust is deposited uniformly onto the surface of sphere. Given the density of dust to be ρ, find: 1. relation rate of increase...
  23. jhae2.718

    Lunar Atmosphere Dust Environment Explorer

    LADEE, the Lunar Atmosphere Dust Environment Explorer, is set to launch tomorrow from NASA Wallops Flight Facility on an Orbital Sciences Minotaur V launch vehicle. It's a neat mission with some good science on it. Launch is scheduled for tomorrow, Sept. 6, and will be shown on NASA TV...
  24. WannabeNewton

    Mass conservation charged dust

    Hi guys! This is related to a recent thread but since that thread became cluttered, I figured it would be more coherent to just ask the question here. Say we have a congruence of charged dust particles in some space-time with tangent field ##\xi^a##. The energy-momentum of the charged dust is...
  25. tom.stoer

    Spherical symmetric collapse of pressureless dust

    Is there an exact solution for the spherical symmetric collaps of pressureless dust? Can one see a Schwarzschild solution for r > Rdust with shrinking Rdust(t) ?
  26. A

    Is there an intrinsically safe combustible dust monitor for wood pellets?

    I have been tasked with what seems an almost impossible feat. It sounds simple but for some reason it is not. I am looking for a device that can monitor combustible dust, in this case wood dust from pellets. It must be able to handle concentrations of 50g/m^3. The area to be monitored is a...
  27. A

    Lorentz, simultan, radar finds dust grain, inconsistencies

    Hi all, Here is the problem. I want to try to do some calculations with seeing how much time a relativistic ship has before it can dodge a dust grain. I am having some trouble applying the Lorentz Contraction Equations to get consistent results. Take two frames, the coordinates of the...
  28. WannabeNewton

    Dust generated static space-time implications on fluid 4-velocity

    Imagine we have a perfect fluid with zero pressure (dust), which generates a solution to Einstein's equations. Show that the metric can be static only if the fluid four-velocity is parallel to the time-like (and hypersurface orthogonal) Killing vector characterizing the static metric. So, I...
  29. Spinnor

    Expanding/Collapsing Universe vs Bouncing Ball: Kinetic & Potential Energy?

    I think in a piece by John Baez we learn that the physics of an expanding and collapsing dust filled universe is the same as the physics of a bouncing ball, Radius, R, verses time and height, h, verses time? If so are there counterparts to the kinetic and potential energy of a bouncing ball...
  30. R

    How Does Particle Size Influence Emissivity in Circumstellar Dust?

    In this 1984 paper on circumstellar dust, the author says, speaking of the emissivity/absorption of dust grains at visual and infrared wavelengths: My question is: where did the expression ##\lambda_p / 2\pi## come from, and what is the physical justification for it? I understand that small...
  31. N

    On the formation of larger bodies in space after dust attraction.

    When a (say 50 meters) asteroid 'A' strikes a larger (say 500 meters) ‘equally hard’ asteroid 'B' at a small angle to the asteroid 'B' would have two vectors, one large vector parallel to the asteroid 'B', another second small vector perpendicular to the asteroid 'B'. ...
  32. M

    Charge for a Grain of Dust on the Moon?

    Homework Statement How much charge in Coulombs is required to levitate a motionless grain of dust 10 cm above the surface of the moon? Assume the dust grain is a point mass with mg = 1*10^-9g. The gravitational acceleration at the surface of the moon is 1.6m/s^2. Assume charge on the surface...
  33. M

    Two Unrelated Questions about GR: Light Cones and VS Dust

    Question 1: How does the metric relate to the light cone at a particular point? Obviously, the metric should determine the shape of the light cone, but is the converse true? Does the orientation and width of the light cone tell you everything about the metric? I'm guessing not due to the...
  34. R

    Solar system space dust avg density[kg/m^3]

    What avg density [kg/m^3] may I attribute to solar system space dust? Halliday & Resnick give E-18 to E-21 [kg/^3]. This will allow me to compute solar system density, if I know solar system radius[m], ie, distance from edge of solar system to centre-of-mass of our Sun. By 'space dust' I mean...
  35. N

    Find the rms speed of a dust particle.

    Homework Statement Dust particles are 13.0 micrometers in diameter. They are pulverized rock, with ρ=2540 kg/m3 . If you treat dust as an ideal gas, what is the rms speed of a dust particle at 18.0 C? Homework Equations ρ=m/v V=4/3∏r2 vrms=√(3kT/m) The Attempt at a Solution...
  36. Saladsamurai

    Recommendations to Clean Brake Dust from Wheels?

    I'm not talking about caked on or burnt on brake dust due to years of neglect. I'm talking my car has 5000 miles on it and came out from an oil change with greasy brake dust all over my alloy wheels. I am not the type to scrub my wheels all weekend, so I want to nip this in the bud before it...
  37. A

    A spacecraft encounters a stationary dust cloud of density rho.

    I'm currently preparing for a prelim and just wondering if my solution to this problem is correct. I did a plot of v(t) and it looked reasonable. You can find the question and solution both at http://oi50.tinypic.com/2e3v4e8.jpg. The Problem states: A spacecraft of mass m_0 and...
  38. S

    Why are Dust Particles Moving in a Specific Direction in a Sunlit Car?

    I am a curious (or perhaps bored!) fellow, and as such I noticed something peculiar recently. I was sitting in a car in a garage. The car was stationary and off, and it was facing the east. The sun was beginning to set in the west and a light shone through the back window shield. In the rays of...
  39. S

    Unraveling the Mystery of ISM Dust: Origins & Categories

    Hi can anyone help : Are there different categories of ISM dust ? Where is the dust thought to have come from? Many thanks
  40. F

    NASA NASA's Stardust Mission - Interplanetary Dust Particles

    NASA's Stardust Mission -- Interplanetary Dust Particles Hello all, I'm currently working on a research paper about IDPs, and I'd like to spend some time discussing NASA's Stardust Mission. I'm wondering if anyone might know of some links to some scholarly articles concerning the matter...
  41. C

    The mass of all interstellar gas and dust in our solar system

    I am a 17 year old high school student in Alabama, and after my astronomy test today, I decided to calculate the mass of all interstellar gas and dust in our solar system (under the assumption that the solar system extends to 55,000 AU in all directions) and I calculated the mass to be a...
  42. L

    Superconductor dust levitation in the Earth's magnetic field

    In the wake of recent metallic hydrogen news, and the fact that metallic has long been thought to be a room temperature superconductor, I began to ponder about the age old question of superconductor levitation. Now that we are no longer restricted by temperature requirements, perhaps levitation...
  43. L

    Dust aluminium atracted to magnet

    Hi Sorry I'm not good in physics at all. I have the following dust problem becoming attached to Nickel coatings. from what i know Nickel can become magnetic but aluminium should not be attracted to magnets. I did an experiment to confirm if the nickel coat is acting as magnet in...
  44. P

    Vacuum and non-vacuum regions, dust and fluids

    In GR there is made a clear distinction between a vacuum region and a non-vacuum region as one is handled by the Ricci tensor and the other by the Weyl tensor. But is reality so black and white? And when do we realistically talk about dust and when about fluid? So the inside of an average...
  45. T

    Detecting Cosmic Dust: The Challenges and Solutions

    What kind of observation can be made to verify the existence of cosmic dust (space dust)?
  46. Dotini

    Simple Supersymmetry Bites the Dust

    http://www.bbc.co.uk/news/science-environment-14680570 Results from the Large Hadron Collider (LHC) have all but killed the simplest version of an enticing theory of sub-atomic physics. Researchers failed to find evidence of so-called "supersymmetric" particles, which many physicists had hoped...
  47. Evo

    Did a Recent Dust Storm in Arizona Cause Disruptions for Airline Flights?

    Did this affect any of our members? http://www.weather.com/outlook/videos/time-lapse-amazing-phoenix-dust-storm-21209
  48. A

    I had a funny thought when i was vacuuming. I was vacuuming dust

    I had a funny thought when i was vacuuming. I was vacuuming dust around the multy plug and I decided to vacuum inside. Would electricity go in the tube?
  49. tom.stoer

    Dynamics of self-gravitating dust

    I have a problem with the following scenario: A friend of mine claims that it's possible to start with equations for a compressible fluid or dust and to derive an expanding solution in Newtonian mechanics (!) He claims that this expansion is homogeneous and isotropic (I understand his...
  50. A

    Star absorbed by spherical dust cloud - find effective temp

    problem: The radiation from an old evolved star of radius 10^6km is obsorbed by a spherical dust and gas cloud, ejected previously by the star, of radius 4*10^8km. If all the radiation from the star is re-emitted by the cloud, which is observed to have a temperature of 500K, what is the...
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