Collapse Definition and 466 Threads

I am having trouble understanding a building collapse. According to NIST, on 9/11 WTC7 collapsed after fire weakened its structural steel. They have however admitted that WTC7 fell for 2.25 seconds at free fall. (http://wtc.nist.gov/NCSTAR1/PDF/NCSTAR%201A.pdf) However isn't all the...

http://www.bottomlayer.com/bottom/reality/chap2.html#difference The beginning part of this source is cursory, scroll all the way down to the bullet points labeled with numbers 1., 2., 3., 4. and read them.

Let's consider the following desitegration \pi^0 \rightarrow e^+ + e^- . If measure the spin of electron we know the spin of positron but what if particles are far away. Is it still true. Does anyone measure the correlation of spins if the particles are really far off. Maybe we observe the...

Fact 1.From relativity we have come to view the universe as 4 Dimensional. That is 3 Dimensions of space and 1 of time. As such I have the following questions. Questions 1. Given the universe is 4D, does it not follow that all objects within the universe is 4D? 2. If 1 is true, does it mean...

Hey everyone, I'm not a math or physics major. I've just read a bit about quantum physics and find it interesting. If i understand it correctly, with the two slit experiment, when you send one particle at a time through without a particle detector by the slit, it results in an interference...

Hi I read an article on this about a year ago or so which outlined the issues and the possible causes. Aside from cellphone radiation, it seemed like none of the other proposed causes had been conclusively ruled out. I'm just wondering if anyone could give me a bit of an update on this...

Let's say you have some quantum particle whose eigenvalues for some observable Q are either degenerate or non-degenerate. If you measure the observable and find it to be in a non-degenerate state, then you know that the wave function has collapsed onto this state. Now if you measure the...

I have a sphere or a box with ideally reflecting sufraces (inside). I open a cover, catch 1 photon, and close a cover. Photon is infinitely reflected back and forth inside. I can open a cover later and analyze it. Now say I can a 'superposition' with 50% of the chance that I have a photon and...

hi, I have a question. Is it a reasonable assumption that there is no force that will prevent collapse to a singularity? Without knowledge of the physics involved, and with the impossiblity of singularities in nature (which again might be suspect reasoning), why are black holes considered...

I often hear that stars form when giant clouds of hydrogen start to collapse under gravitational forces, so I started thinking about this. Gravity depends on the masses and distances of objects. So how many atoms of hydrogen would you need, and at what average distance would the atoms need to...

Homework Statement Hi, i want to do a science fair project on the Tacoma Narrows Bridge Collapse. I want to do a research on the Tacoma Narrows Bridge collapse and how it taught us what structures stabilize a bridge against wind forces. I also want to build something that would demonstrate the...

I saw this question posted in a Yahoo forum. I would be interested in the answers from the people here: "We can all agree that the more massive a black hole is the smaller the circumference of the black hole's event horizon will be. Therefore, can a black hole ever have enough mass to where...

This is a story that just came out today (Nov. 16, 2009): Here's the story: http://www.nationalpost.com/todays-paper/story.html?id=2228018 Here's the paper: http://cat.inist.fr/?aModele=afficheN&cpsidt=20683217 Of course, its all Canada's fault again. :-p

Sorry for a (maybe) dumb question, but... I understand that according to QM, the description of the situation for a particle or system is described by a linear superposition of the wave functions of all the possible states (eigenstates) of the system. When a measurement is made, the wave...

Ok this makes sense but pressure inside an airway is determined by hydrostatic pressure and when air moves fast hydrostaic pressure is decreased and converted to kinetic energy. So this collapses the airway. My question is doesn't kinetic energy of moving molecules exert a pressure on the walls...

Let's say you are an observer on the surface of a massive object that is collapsing to form an eventual black hole. As the object's surface approaches its own Schwarzschild radius, light from the object is increasingly redshifted, as seen by distant observers, approaching infinite redshift as...

Is it possible to describe the measurement process in QM simply as a perturbation to the system (either a small one or a very large one) so that effectively the eigenstates of the Hamiltonian evolve into eigenstates of an additional measuring operator? So at t=0 the Hamiltonian H turns into...

One year ago this week, the failure of the banking and investment systems turned the global economy upside down. Apparently we define the beginning of the collapse to be the failure of Lehman Brothers. IIRC, by this time, Fannie and Freddie had already been bailed out. Late edit: Okay...

If a neutron star accumulate materials from its companion star ,then it's mass exceeded Tolman–Oppenheimer–Volkoff limit, it will collapse into a black hole! My question is ,in this case ,it will produce "gamma-ray burst"?

http://www.nytimes.com/2009/08/26/business/economy/26deficit.html http://www.americanbankingnews.com/2009/08/25/white-house-predicts-1-6-trillion-dollar-deficit-in-2009/ If you need more stories then google it. (I posted the New York Times article because they're notorious for liberal spin and...

Sorry people but some quantum mysteries look quite trivial to me. Wave function collapse for photons is actually subsampling of whole sample of photons. That way wave function collapse can happen instantaneously in the whole experimental setup or even backwards in time. Photon entanglement...

What about the act of observation actually causes a particle to break the superpostion and "decide" what its state is? What property does the observer posses that changes the the way particles behaves?

Ok so if we have some matter(a star or whatever) and under classical laws of gravity(GR) this matter is going to form a black hole. If we're in the frame A of the collapsing matter then there will come a time(measured in that frame) that the matter crosses the event horizon after which no events...

I am imagining the collision between two subatomic particles. For the particles to have collided, do we say that the spatial wave functions for each particle must have collapsed to the same point? Or do we say that the particles are just in a very close vicinity, and the wave functions need not...

What happens when a neutron star collapses into a black hole and it's no longer obeying the Pauli exclusion principle? In terms of quantum mechanics? Say it collapses because it gets more massive. A "neutron degeneracy pressure" can be calculated, which is what keeps the neutron star from...

I want to hear your opinion on this: Let's say that the universe in time zero consists just of a cloud of matter. Now as the time progresses, and the matter interacts gravitationally, it will gradually collapse into a sphere. Will the entropy of the universe really increase?

For example, in the double slit experiment, is momentum transferred to say, the wall in between the slits even when the particle manifests on the wall behind the slits? In other words: Is momentum transferred to places where the particle does not manifest? Thanks! Jake

Homework Statement Suppose that the stars in a disk galaxy have a constant orbital speed v out to the edge of its spherical dark halo, at a distance R_{halo} from the center of the galaxy. 1. What is the average density \rho for the galaxy, including its dark halo? 2. If a bound structure...

http://www.guardian.co.uk/world/2009/apr/05/ice-shelf-wilkins-antarctic"

In NMR for molecules, one can collapse the nuclear spin wavefunction \psi_{nucspin} by applying the magnetic moment operator \mu. That is, \psi_{nucspin} becomes one of the eigenfunctions of \mu. This physically corresponds to hitting the nuclei with photons in the radiofrequency range. In...

If we solve the Schrodinger Equation for hydrogen atom, we get discrete energy levels that agree with experiment. But no where we need the wave function collapse. So my question is where the wave function come from and why do we need it?

Hi folks, I'm not sure if it's best to ask this question here, or in the Special & General Relativity section - it's probably more appropriate for this forum. I've been wondering about the following question: what effect does wavefunction collapse have on space-time? For example, if we...

I just started learning QM. I was wondering, if a wavefunction can only collapse onto a few eigenstates, how come the probability distribution graph is a usually continuous one? :S

this is a question that has been bugging me from the beginning of my learning of quantum mechanics. why does the the wavefunction collapse when we do a measurement? since we have no concrete idea about collapse, we use probability theory to understand quantum phenomenon. but at least from...

Could it be that the universe is collapsing upon us without us yet knowing since the nearest star to us is about four light years away and therefore we have no present way of knowing what has happened during the last four years beyond that nearest star?

One thing I’ve always found a bit of a curiosity is how a rapidly rotating star might collapse to a ring singularity relative to the speed of light and what the final parameters of the ring singularity might be (i.e. reduced circumference considering r=0 at the ring edge). Due to the...

http://arxiv.org/abs/0902.1464 Does wave function collapse cause gravity? Authors: Lajos Diósi (Submitted on 9 Feb 2009) Abstract: We give a twist to the assumption - discussed in various earlier works - that gravity plays a role in the collapse of the wave function. This time we discuss...

My question is, when a compact star collapses to form a black hole, how does it manage to dispose of the heat necessary to make this transition? Naively, it would seem that the object can never cool itself fast enough due to increasing gravitational redshift of its thermal radiation. Each...

Poor title. Actually I have a whole bunch of wave function questions. I don’t know the boundaries of this concept. Assuming a correct wave function, can a particle have more than one? Can 2 observers each have their own wave function? The moment a particle encounters another particle, does one...

http://www.ft.com/cms/s/0/7a03e5b6-c541-11dd-b516-000077b07658.html?nclick_check=1 This is something that Astro and I were talking about recently. I suspect that one ramification of the current economic crisis is that nations are being forced to work together in ways that we've never seen on...

Consider a system of two bosons with spin, say photons. The wave function must be symmetric under the exchange of the two particles. For example, |psi> = |up> |down> + |down> |up> So far, so good. Now let us measure the spin of the particles, and let the outcome of the measurement be that...

As far as I understand it, an electron exists as a probability cloud around an atom, representing all the possible places it could be. Then when we make an observation the wave function collapses to one point where we see the electron. So what happens if we keep looking at it? Does the elctron...

http://news.bbc.co.uk/2/hi/business/7659086.stm I was wondering how this will affect the humans' migration and global culture (authority too) etc. It seems like China is getting ahead and migration flow will be reversed. I don't have enough data and knowledge to make any predictions but for...

Hello, I would like to define (calculate/plot) the radius of collapsing interstellar cloud as a function of temperature, density and presure of the star. I would like to describe the collapse calculations of an originally homogenous cloud of one solar mas, with low initial presure and...

What would life be like with no intraweb, may be caused by some super virus, how would the world carry on?

If waves collapse upon detection, how is it that the Friis transmission equation yields accurate results? Regards, Bill

Proof of state "collapse? Maybe I don't even have the terminology correct for this... I'm a quantum physics noob :) My question is this: take the EPR experiment for example. What I've heard is that each electron in the pair is in an indefinite state of spin (either + or - with respect to a...

In QM we have the postulate of measure giving rise to the notion of wave function collapse throught measurement. Is there an analog description of collapse in QFT (even an effective one) ? And what is then collapsing ? The field ? What would that mean ? I'm interested for references on the...

Society in general, human beings, etc...? Will something non-human one day rule the Earth again?

A certain radio tower was stabilized at the top with guy wires, and at the bottom with a concrete foundation. So, it was stable at the bottom and at the top. In windstorms, it wobbled violently in the middle. Eventually the tower collapsed. Using wave theory, explain why this happened and...