Matter Definition and 1000 Threads

Homework Statement so my friend asked this question: "what's the atomic radius ratio between He-3 and He-4?" 2. Homework Equations all i know is this equation : r =nh/mv 3. The Attempt at a Solution i thought the ratio will be same because both He-3 and He-4 have only two electrons. Correct...

In Dodelson's book, the equation for a scattering process ## a + b \Leftrightarrow c + d ## is given as ##a^{-3} \frac{ d (n_a a^3)}{d t}=-n^{\text{eq}}_a n^{\text{eq}}_b<\sigma v>(\frac{n_a n_b}{n^{\text{eq}}_a n^{\text{eq}}_b} - \frac{n_c n_d}{n^{\text{eq}}_c n^{\text{eq}}_d}) = - <\sigma...

Dear PF Forum, In less than 1 second after big bang, baryons were created. And there's asymmetry in it. Can anyone help me? 1. Is it physically possible for a galaxy made entirely from anti matter? 2. If it's true, is it statistically possible for a galaxy made entirely from anti matter? If...

Hi PF Family, I'm a rising junior majoring in physics. I plan to enroll and be accepted into graduate school(s) such as UIUC, Princeton, and MIT. I know that requires much work and hard work. However, my problem is in choosing the right program. I want to be able to integrate CMP and Materials...

Q1.In school, we were learning about the magnetic properties of solids, and my teacher mentioned this, a spinning electrons create magnetic field. I cannot understand how. Like earlier we were told if a charge is in motion, it creates magnetic field, but in spinning, it does not have...

Hi all again, I started a post earlier and it was buried somewhere by now. I really need more input and information and hope you all can help. How are admission process different, CM vs MS&E? CM belongs to Physics department while MS&E is usually on the engineering side. I got my Physics...

Hey! I need some help please! Anyone know how I can calculate the quantity of matter, the mass concentration and the molar concentration? It is for a physics exercise! Thanks :)

OK so I currently attend The University of North Texas, which is by no means a prestigious school for physics. I am a physics major with 72 hours of coursework under my belt. I plan to attend graduate school and would like to get into a good school for something in the realm of theoretical...

Hello everyone, I would like to ask a couple of questions related with the interaction mechanisms of photons and electrons with matter. Through searching about this subject, I have concluded that they both have different penetration depth and different interaction mechanisms. But apart from...

I want to know Universe density according to this equation( ##k=-1##) ? ##H^2(t)-8πρG/3=-k/a^2(t)## ##ρ_U=ρ_m+p_r## ##ρ_U##=Universe density ##ρ_m##=Matter density ##p_r##=Radiation density

Hey, I'm trying to look for a single test set-up for a dark matter-only simulation I and my friend are building. It's currently based on a particle-in-cell approach and we are calculating the Poisson equation and particle trajectories in a co-moving frame (so expansion of the Universe is taken...

Does anybody know where I could find worksheet to practice naming the state of matter in chemical reactions (with answers in the worksheet to check) as I have problems with that. Especially deciding when it is aqueous. I know (well at least i am right) that when you have acid as reactants it has...

Hi, I have some problem in deriving \Delta m_M^2 as given in eq.35 here: http://www.slac.stanford.edu/econf/C040802/papers/L004.PDF When I tried to derive the eigenvalues of H_M (eq.33) I got: m^2 = (\cos 2 \theta -x)^2 + \sin^2 2 \theta which is only one eigenvalue. Any help? In...

Homework Statement http://pastebin.com/aS3vTR2V Homework Equations N/A The Attempt at a Solution I'm confused about what I need to do for the BlobFinder constructor. Someone told me that I should “initialize the ArrayList blobs”, then “create a 2D array of booleans called marked, having the...

Hi everyone! I was admitted as an undergraduate transfer student to MIT and Harvard College for Fall 2015. I am now stuck deciding between the two. Which one do you think is better for studying experimental condensed matter physics or just physics in general?

Hi there, I've been reading a textbook on Physics as applied to nuclear medicine, in particular focusing on how photons interact with matter. The textbook states (without reference) that "there are nine possible interactions between photons and matter, of which only four are of significance to...

So, I am an incoming MS student interested in going into condensed matter theory. I have always been more comfortable running C++ or FORTRAN simulations or crunching contour integrals than doing math proofs. I only gained the interest in CMT relatively late in my undergraduate career when I...

Hello to all ! I wanted to ask a question in this forum. I am french, and I have discussed this topic in a french physics forum, but with no clear conclusion. I hope I'll have another insights in this forum, which seems very well frequented. I know the underlying subject has been discussed in...

The main evidence for the existence of dark matter is the flat rotation curve of galaxies, and high peculiar velocities of galaxies in galaxy clusters. The mass eclosed in a radius R is derived from the Keplerian equation M(R) = v2R/G . Also we know about the existence of gravitational...

This paper seems to be saying so. can the universe be logotripic, whatever that is? arXiv:1504.08355 [pdf, other] Is the Universe logotropic? Pierre-Henri Chavanis Comments: Submitted to EPJPlus Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); General Relativity and Quantum...

Wouldn't this explain why galaxies with no black holes are so small?

Im working on deriving the final expression on the attached picture. The problem is that of a particle in a potential coupled to a "bath" of harmonic oscillators but I'm not sure how you arrive at the final expression. First of all, why are you allowed to assume that q is periodic on the...

if velocity of a huge particle is made zero what will happen?? will the particle spread out into the universe aka complete delocalization??

I know this is the Physics Forums and not the Biology Forums, but I feel that this question is more on the physics side of the spectrum than the biology side. What potential effects could the existence of a hypothetical, unusually warped spacetime, where there were naturally-occurring curves...

Homework Statement What mass of mater would be converted to energy to provide 3200W of Power for 3 days? Homework Equations P=E/t E=mc2 The Attempt at a Solution [/B] E=P*t Subbing mc2 for energy I get mc2=P*t m=P*t/c2 m=(3200W*3Days)/(9X1016m2/s2) m= 1.066X10-13kg This answer is...

I am curious about mass of a galaxy without dark matter and with dark matter.I searched but I couldn't found.I ll be happy If you help me. Thanks

"Why do so many physicists believe there has to be a structure to the vast voids in space" ? Surely, Their thinking defies the basic principles of physics, i.e. in order to have something there has to be nothing ! to have a positive there also has to be a negative, so as for the positive to...

I need someone with more experience in the field who has knowledge of excel to check over my work. Given the gravitational attraction between two bodies is F = (GMm)/r^2, and the centripetal force required to keep a body in orbit is F = (mv^2)/r, therefore (mv^2)/r = (GMm)/r^2 therefore...

Hello! What would be the theoretical properties of a particle, that moves perpetually and infinitely inside an object, bouncing from side to side inside the object walls, hardly being objected to collisions with other particles and which changes its path of movement inside the object, only when...

Homework Statement An electromagnetic wave with frequency 65.0Hz travels in an insulating magnetic material that has dielectric constant 3.64 and relative permeability 5.18 at this frequency. The electric field has amplitude 7.20×10−3V/m. What is the intensity of the wave? Homework Equations...

Ismatter wave travel faster than velocity of light?:oldsurprised:

When discussing doing theory for grad school with one of my professors, he mentioned not having a 4.0 would be detrimental for top schools in theory. Currently, I have a 3.94/3.95 in physics and will have a 3.9-3.92 in math by the end of my college career. Is there any truth in my professors...

From what dark matter in space consist of?

http://phys.org/news/2015-04-potential-interacting-dark.html An international team of scientists, led by researchers at Durham University, UK, made the discovery using the Hubble Space Telescope and the European Southern Observatory's Very Large Telescope to view the simultaneous collision of...

Looking for textbook recommendations for condensed matter physics at both undergrad and graduate level. Preferably to self teach with, and including questions/answers.

This question straddles this forum and the "Beyond the Standard Model" one a bit, so if a mentor thinks it belongs better elsewhere, please feel free to move it. I've seen references in the "popular science" press about the possibility of indirectly detecting dark matter by looking for gamma...

Homework Statement Imagine a hypothetical process in which the methane molecule, CH4, is "expanded," by simultaneously extending all four C−H bonds to infinity. We then have the process: CH4 (g) → C(g) + 4H(g) Compare the reaction for the "expansion" of methane with the reverse of the reaction...

Let me start of with this first: I'm not a physicist, I'm a software engineer, so my knowledge about this is pretty much nihil. Anyway, my question is, why is it assumed that matter causes gravity? Is there any proof or logic behind it? What if matter and gravity are two separate things that...

Suppose a change of basis from basis ##B## to basis ##C## is represented by the matrix ##S##. That is, ##S## is the transformation matrix from ##B## to ##C##. Now if ##t## is a given linear transformation, ##t:~V\rightarrow V##, with eigenvectors ##\epsilon_i##, say, and ##T## is the...

Is there a non hypothetical particle [aka axion] that can be the make up of Dark Matter?

Wikipedia define EM field as "a physical field produced by electrically charged objects" But there are no electrically charged objects in between cosmic entities and yet Wiki states "The electromagnetic field extends indefinitely throughout space". What am I missing here?

Hello, For a future development, Me and a friend of mine were talking about some thruster technology and we wondered if it was possible to transform electricity to matter to create some sort of chemical thruster or using the matter to create an ion and use it as the thrust. well at least...

Here's a video that claims that gravity can be derived from the Standard Model. See the Video. The video is by Frederic P Schuller. Isn't this exactly what Einstein was trying to accomplish in the last 30 years of his life - to unite EM and GR? Or isn't this exactly what quantum gravity...

I know very little about physics, but I have a question. What are the effects of turning an off road snorkel head backwards (facing the rear of the vehicle)? We on the FJ Cruiser forums are debating, and I thought I would ask the experts :) Some of the concerns/debates include: reduced air...

http://www.nasa.gov/press/2015/march/nasa-s-hubble-chandra-find-clues-that-may-help-identify-dark-matter/index.html The take away seems to be that some ideas about dark matter may have problems. The possibilities checklist of dark matter interactions has been shortened. There are some really...

Hello It is my understanding that the matter originally contained in a dying star which formed a black hole has been entirely converted to energy in the form of space time curvature. In other words the matter no longer exists and all that is left is the curvature of spacetime. Aside from my...

I've got a homework question that I'm particularly stuck on: Suppose that the halo, assumed spherical, of non-baryonic dark matter surrounding our galaxy has mass ~ 5 x10^12 M solar and radius 0.1 Mpc. What it its average density in Kg m-3? I think that I need to use the formula...

Given sufficient energy a proton/antiproton pair can be created from photons in the laboratory. Does the (apparently) slight bias exhibited in the big bang apply to the laboratory? In other words, the universe is seemingly not made of antimatter, only "matter." Pushing this idea further, is...

Supersymmetry interachanges bosons and fermions and can make bosons transform into fermions and vice versa... is there equivalent in quantum gravity where spacetime and matter can transform to each other and spacetime can become matter and matter can become spacetime.. isn't something akin to...

Imagine an axe going through a sheet of metal, both made of the same probe. On the basic level of language - the axe goes through the sheet. On the next level of language - due to pressure, delivered by the edge of the blade, the bonds between the molecules of the metal sheet begin to tear. But...