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. S

    Dust Particle Moving with Air Drag

    Hello everyone, This question isn't exactly a homework problem, but it's a problem I need to solve for my senior project, which is a particle image velocimetry system. I'm running into a nasty differential equation which is what I'm having trouble with. Homework Statement A 30 micron...
  2. M

    How can the electric potential of a dust grain in Saturn's rings be determined?

    Homework Statement Much of the material making up Saturn's rings is in the form of tiny dust grains having radii on the order of 10^-6 these grains are located in a region containing a dilute ionized gas, and they pick up excess electrons. As an approximation suppose each grain is sphereical...
  3. P

    Displacement of zigzaging dust particle

    Homework Statement A particle of dust is bombarded by air molecules and follows a zigzag path at constant speed v. (a)Assuming each step has a length d, find the distance traveled by the dust particle in time t. (b)What is the length of the displacement vector after N steps where N is large...
  4. S

    Could Dust Be Responsible for the Pioneer Anomaly?

    I have looked through the on-line documentation of the Pioneer Anomaly, and have a simple question: Could the apparent additional acceleration toward the Sun be due to an additional mass of dust which adhered to the spacecraft ? I notice that the authors of the main papers (...
  5. C

    Dust vs Suns: Exploring the Abundance of Dark Matter in Space

    I guess dark matter is the most abundant matter. But which contributes next to the most, intersteller dust or suns?
  6. B

    Force on Planet Moving in Interstellar Dust

    Homework Statement A uniform, spherical planet of mass M and radius R moves SLOWLY with an essentially uniform speed v through a cloud of interstellar dust particles, whose density is ρ. The dust particles are attracted towards the planet, and some of them would eventually fall onto its...
  7. A

    Astronomy - interstellar dust grains

    Homework Statement A typical dust grain has a radius of 10-7 m and a mass of 10-14 g. How many dust particles are there in a molecular cloud containing 1000*Masssun of dusty gas if 1% of the cloud's mass is in the form of dust grains? Homework Equations The Attempt at a Solution...
  8. L

    Momentum conservation of asteroid in a dust cloud

    Note: this is one of the suggested practice problems for my second-year classical mechanics course. Homework Statement A spherical asteroid of mass m_{0} and radius R, initially moving at speed v_{0}, encounters a stationary cloud of dust. As the asteroid moves through the cloud, it collects...
  9. K

    Spherical asteroid moving through a dust cloud

    Homework Statement A spherical asteroid of mass m0 and radius, R, initially moving at speed v0, encounters a stationary cloud of dust. As the asteroid moves through the cloud, it collects all the dust that it hits, and slows down as a result. Ignore the increase in radius of the asteroid...
  10. A

    Gravitational Conditions: Dust Cloud vs Black Hole

    I am sure to those of you who know GR this will be a simplistic question. I can only hope there will be a simplistic and definitive answer :-) Assume a dust cloud of radius=5 and a mass =mc ANother equivalent mass of condenced matter md=mc with a radius=1 What would be the...
  11. S

    Dust Collection Foot Air Flow Help

    Please move to the right place if I have posted in the wrong location. I want to improve the performance of my dust collection foot on my CNC machine. I am using a dust collector that has a 2 HP, 120 volt, 60 Hz, 20 amp peak, single-phase motor. It generates 1550 CFM air suction capacity...
  12. R

    Entropy and Dust: Uncovering the Mystery of Dust in Vacation Home

    Entropy and Dust! I don't know if this goes here or in the Chemestry forum, I Want to Know Why a Closed House gets Filled with Dust...i have an Apartment in another state for vacation, we had´nt been there since 3 month ago...this past weekend we went and the Apartament which we left completely...
  13. D

    What Should I Use For Solar Cell Dust Testing

    Hello! Right now I am trying to figure out how much of an affect dust has on the power production of some solar cells that I have. I was just searching for a possible material to use for dust testing. Anyone have any bright ideas?
  14. I

    BRS: The FRW Dust with E^3 Hyperslices - Discussion

    Ok, I've looked a bit into your Posts. The problem is, I suck at math (i.e. differential geometry). So please tell me if I got the basics right (your post #6): The Minkowski basis vetors are \partial_t,\partial_r,\partial_\theta,\partial_\phi, with length 1,1,r,r \, \sin(\theta)...
  15. N

    What determines shape of dust nucleus?

    Is a dust nucleus, dust attached to air? If water vapor molecules, attach themselves to dust nucleus in building visible [to the eye] snowflake, I'm supposing flake takes on shape of the dust. Does this mean "air" is shaped too? Don't laugh; I'm most confused!
  16. C

    BRS: The FRW Dust with E^3 Hyperslices

    The simplest frame Ansatz consistent with Hubble's discovery is: \begin{array}{rcl} \vec{e}_1 & = & \partial_t - f \, \left( x \, \partial_x + y \, \partial_y + z \, \partial_z \right) \\ \vec{e}_2 & = & \partial_x \\ \vec{e}_3 & = & \partial_y \\ \vec{e}_4 & = & \partial_z \end{array}...
  17. T

    Infinite universe filled with uniform dust

    If you had an infinite universe filled with a static, homogeneous, electrically neutral dust, the same in all directions, so that there are no forces to consider other than gravity, what would happen? Would it remain in that static state? I have two ways of thinking about it that lead to...
  18. K

    Calculating Charge and Electron Count of Dust Particle in Electric Field

    Homework Statement A small piece of dust of mass m = 1.6 g travels horizontally through an electric air cleaner in which the electric field is 508 N/C. The electric force on the particle is equal to the weight of the particle. a)What is the charge on the dust particle? b)If this charge is...
  19. Spinnor

    Dust filled universe, is there a type of tension defined?

    Say we have dust filled universe. At some instant of time this universe has a mass density rho, and it evolves with time according to General Relativity. Is there a quantity in that universe that acts like tension? Can we associate something like tension in such a universe. Would its strength...
  20. Spinnor

    Dust filled universe but dust is a real field.

    Tuning the mass density of a closed dust filled universe can give us a long lived closed universe? General Relativity can tell us how that mass density changes with time? Instead of dust let us have a real field defined at each point of spacetime. Let us assume the field is such that in...
  21. Spinnor

    Uniform background dust of plank mass black holes.

    Say our early Universe had a significant fraction of its mass in the form of a uniform dust of plank mass black holes, along with the visible matter of our present universe. How might you figure such a dust would evolve in our early universe to our present epoch? Would such a dust clump just...
  22. C

    Magnitude of force on a Dust Particle

    Homework Statement A magnet produces a 0.40 T field between its poles, directed horizontally to the east. A dust particle with charge q = -8.0×10-18 C is moving vertically downwards with a speed of 0.30 cm/s in this field. Whilst it is in the magnetic field, the dust particle is also in an...
  23. Z

    Absence of dust on moon and material sciences

    Might absence of dust on moon (such as for astronauts' experience) relate to importance of material sciences? That is, might surfaces interact electronically, seeking a more stable lowest energy configuration? Imaging it as if 2 grates rubbing together, seeking best fit? Air might then disrupt...
  24. nomadreid

    In simplest terms, what is null dust?

    The links I pull up assume that the reader knows what null dust is. Which I don't. An explanation would be appreciated. The question came up when looking for an (equally absent) clear explanation of Vaidya spacetime. This, in turn, came up while looking at the article...
  25. X

    Conservation of Momentum for Asteroid in Dust Cloud

    Homework Statement A spherical asteroid of mass m_0 is moving freely in interstellar space (no external forces) with velocity v_0 . It runs into a dust cloud whose uniform density is \rho_d Assume that every particle of dust that hits the asteroid sticks to it and that the asteroid remains...
  26. D

    Are Grain Dust Particles Explosive Due to Static Electricity?

    I realize that this topic is more towards chemistry however i was wondering why grain dust particles are explosive. Is there any carbon atoms in the dust particles that fuel these explosions?
  27. sylas

    Massive dust storm in Australia

    I woke up this morning and the light was freaky! Everything seemed orange. Outside, the sky is pale orange, like fog but the wrong color. Trees a few houses across are fading into the orange ... we've got a dust storm. I live in Newcastle, a bit north of Sydney. This storm came up last night...
  28. K

    Why does Saturn's dust form a flat ring and not a sphere around it?

    Why does Saturn's dust form a flat ring and not a sphere around it?
  29. B

    Find the charge on a piece of dust

    Homework Statement A small piece of dust of mass m = 1.6 g travels horizontally through an electric air cleaner in which the electric field is 511 N/C. The electric force on the particle is equal to the weight of the particle. What is the charge on the dust particle? If this charge is...
  30. W

    Retarded Force in Space and interstellar dust

    Homework Statement A uniform, spherical planet of mass M and radius R moves SLOWLY with an essentially uniform speed v through a cloud of interstellar dust particles, whose density is ρ. The dust particles are attracted towards the planet, and some of them would eventually fall onto its...
  31. G

    Astrophysics - Accretion of Space Dust

    Homework Statement Imagine a planetesimal sweeping up small particles from a dust cloud. Suppose the planetesimal, of mass M and radius R, is moving through the cloud at a velocity v. There are nd dust particles per m3, each of mass md (a) Derive an expression for the number of collisions per...
  32. T

    Interstellar Gas & Dust, Densities & Temperatures

    Howdie. This question started from what was to be a "simple" analysis of heating the air in a room. So much for simplicity when you start to question what exactly is heat and what is happening to atoms and molecules. SOOOO...the question I have (which will have bearing on my INITIAL quest)...
  33. D

    How can I use electrostatics to collect dust in my home?

    hi, i'm trying to find a way to attract small dust particles in a household environment to a surface. i have no physics and no engineering skills whatsoever so this is all new to me, but what i am wanting to do is have a surface with a constant charge, as perhaps this is the way to achieve this...
  34. D

    Creating a Long-Lasting Static Charge to Attract Dust

    hi, i have some questions about static charges and to see if anyone is able to help me with an experiment. i am pretty naive about this stuff, so please excuse my ignorance if i ask you any silly questions in response to suggestions. i want to create some sort of charge on a surface (about...
  35. E

    Why is the dust tail of a comet a tail?

    is it also due to solar wind? if so why is it in a different direction than the gaz tail?
  36. R

    Electrostatic dust distribution

    Hi, I am more familiar with the world of biology and chemistry, however I am trying to come up with a method to evenly distribute dust over a surface area which may require a bit of Physics help. I was wondering is there any way of say, positively charging an aluminium foil surface and...
  37. O

    How much does dust affect light from high redshift quasars?

    As I understand it, the conclusion that our spatially flat universe is expanding at an accelerating rate is supported by observations of 'standard candles' (type S1a supernovae) which appear less bright than expected when their z exceeds about 0.3 --- . Robert Kirschner has discussed these...
  38. L

    News Jindal - Another one bites the dust?

    http://www.cnn.com/2009/POLITICS/02/25/jindal.reaction/?iref=mpstoryview Is this the best the Republicans can offer? That was a train wreck last night. I think his sing-song condescending response was dreadful. Sara Palin has pretty much soiled herself after getting demolished in the General...
  39. Astronuc

    Dust storm in our neighborhood

    Fountain of Mysterious Space Dust Found http://news.yahoo.com/s/space/fountainofmysteriousspacedustfound Mystery of Red Space Glow Solved (06 April 2007) http://www.space.com/scienceastronomy/070406_red_rectangle.html Dying Star (HD 44179, "Red Rectangle") Sculpts Rungs of Gas and...
  40. S

    How Does Light Expand in a Ring Around a Dusty Star?

    Homework Statement A star surrounded by a sphere of dust with a radius R. The star emits a short bright flash of light, it is absorbed and re-emitted by the dust. Someone much further away than R sees the light, first at a point on the shell and then in an expanding ring. A)Show that the...
  41. D

    Dust Particles: RMS Speed Calculation (3*10^13 mm/s)

    calculate the rms (root-mean-square) speed v_rms of these particles, assuming them to be spheres of diameter 5 \; \mu {\rm m} and density 2 \; {\rm g}/{\rm cm}^3 = 2000 \; {\rm kg}/{\rm m^3}. The mass of such a dust particle is 1.31 \times 10^{-13} \; \rm kg. Express your answer in millimeters...
  42. N

    Why do dust particles stay suspended in the gas?

    A diagram shows many very small dust particles suspended in the gas in a closed transparent glass. Question: Explain why dust particles stay suspended in the gas and do not fall to the bottom of the syringe. My answer: Dust particles are constantly being bombarded by free moving gas...
  43. R

    Floating speck of dust with charge

    So this is a problem my friend was doing. I don't remember the specific values for the variables, but it should be ok. There is a speck of dust floating above an infinite plane. The speck of dust has a charge q1. The plane has a charge density of sigma= xC/m^2. What is the mass of the speck of...
  44. B

    Airborne dust, water vapour and global warming

    More dust in the air presumably means that there are more nuclei on which water molecules can condense to form liquid water.Water vapour is a greenhouse gas so can the current trend in global warming be attributed to less dust in the air than usual resulting in more water vapour and higher...
  45. A

    Unveiling the Mysteries of Dust: Composition, Properties and More

    What is ...Dust? I know this is quite ackward and may not be the right place to ask such a question but I am a bit curious to know something good about it: Earth is composed of soil; Soil is a mixture of elements and compounds; But we don't use the soil around us to extract those compounds...
  46. N

    Depletion of an element on dust

    Hey there Could anybody answer the following question on dust grains and depletion of Silicon and Carbon on dust: If D(Si)=-3, D(C)=-0.5, and the logarithmic cosmic abundances of Silicon and carbon relative to H as 12 are 7.5 and 8.5 respectively, what is the ratio of the number of atoms of...
  47. B

    Dust accumulation and change of weight (or mass, or gravitation field)

    I was wondering what is happening with Earth accumulating dust and other debris from outer space? This must change earth’s weight? What is the rate of this accumulation of weight? The same thing must be happening to the sun, surely in proportion to the gravity field of the sun, so probably all...
  48. C

    Force on Particle in Dust Cloud

    [SOLVED] Force on Particle in Dust Cloud The following problem is from Thorton & Marion's Classical Dynamics, Ch. 5 Problem 5-13 (p. 205 in the 5th edition of the text) Homework Statement A planet of density \rho_{1} (spherical core, radius R_{1}) with a thick spherical cloud of dust (density...
  49. S

    Carbon dust mistaken for Dark Energy all this time?

    http://www.ciw.edu/news/dirty_space_and_supernovae
  50. S

    Energy-mom tensor of charged dust (homogeneous and isotropic)

    You have charged dust (pressure = 0, charge density/mass density = given constant). I suppose the total energy-momentum tensor of that system (including the rest energy and the EM field) cannot be expressed simply in terms of the arbitrary 4-velocity of the dust like for example the case of...
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