Holes Definition and 1000 Threads

Simple question to ask, but probably not so simple to explain an answer: Can an object moving faster than light (I would say a tachyon, but I don't want to since there are different theories about what a tachyon might be) escape from a black hole? Obviously a black hole isn't just about...

What actually are electron holes? I have come to read that electron holes are nothing but the blank space that is left behind when an electron is missing in a crystal where it ought to have been present. I have also learned that the movement of holes are due to adjacent electrons jumping into...

Fermi Energy, Quantum mechanics Electron levels and degeneracies thereof in a system are: W1 = 0 eV, 10^23 /cm3 Valence band W2 = 0.9 eV, 5x10^20 /cm3 Donor level W3 = 1 eV, 2x10^23 /cm3 Conduction level Total number, n, of electrons in the system is (10^23 + 5 x 10^23)...

Hi all, Apologies if my understanding is a bit simplistic but even if my question turns out to be idiotic, I'm sure I'll learn from your replies. Thanks in advance! So the reason dark matter was postulated in the first place is because the observed gravitational effects in the known...

What I am posting here it is not an alternate theory nor a criticism of any accepted theory. I just have an idea born from what I know (like a non-specialist) about cosmology and I need your help to understand if it is a good idea or a wrong one. Related to expansion of Universe we can...

I would request for help in understanding why the drift speed of electrons in semiconductors is more than that of holes. Thanks.

When two black holes collide, do their singularities merge the instant their event horizons touch? Or is there a lag between the event horizons touching and the singularities merging when there are actually two singularities inside a single black hole?

Hello. I have been set a problem by a student. It appears to be fairly old, but I cannot find much info in the web. Here it is: A 1" cube has three holes drilled in it, each hole connecting the centres of opposite faces, thus forming a cavity in the centre joined to the surface by six 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...

2 black holes, 2*M --> 1 b.h., 2*M - f*2*M? For equal sized black holes of mass M, what fraction, f, of the energy typically gets lost as gravitational radiation when roughly equal sized black holes merge? If f were plotted verses mass would the function have a maximum? Thanks for any help!

Hi everyone. Does anyone know what would happen if two black holes got too close toghether? Would the merge and become a supermassive black hole?

One of the arguments for the existence of a minimum distance, the Planck distance, is (*) that in order to probe a smaller distance, you need a probe, e.g. a photon, of wavelength smaller than that distance, that is, of very high energy, and indeed such high energy that when it is localized it...

Hello all, I'm currently doing a research paper on the coalescence of two Supermassive black holes (Sagittarius A and the Supermassive black hole at the center of the Andromeda galaxy) and have come across some difficult quandaries. First since (to an outside observer) nothing ever comes...

One topic that interests me is supermassive black holes. Do you think they can exist? Also, have any been reported?

According to Wikipedia: Objects and radiation can also escape from the ergosphere. In fact the Penrose process predicts that objects will sometimes fly out of the ergosphere, obtaining the energy for this by "stealing" some of the black hole's rotational energy. If a large total mass of objects...

http://curious.astro.cornell.edu/question.php?number=760 Yep, it's an exception to the rule that "nothing can escape a black hole".

Can any 1 tell me what is the derivation for worm holes(equation)?

This question was asked by a friend recently, and I couldn't give an answer! To an observer on the Earth, when anything falls towards a black hole, it never actually crosses the event horizon. Therefore, from our observational point of view, how do black holes gain mass? As time goes by, all...

Five Star Question Of The Day: What can a greater understanding about merging black holes tell us about the nature of time?

I have some questions about black holes (BH) for which I don't find until now any answer in what I read. I appreciate all answers. 1. When an observer that is out of BH influence are measure time elapse on a falling object he observe a "time dilatation" effect. What I don't understood is if...

Does it make sense to try to combine quantum mechanics with relativity when trying to understand black holes when the mass of the black hole is so huge? In nuclear physics people use something called the liquid drop theory to model a heavy nucleus using classical physics not quantum mechanics...

I want to reduce the weight of a square aluminum tube, 36 inches long, 1 inch square, and 1/16 inch thick, while maintaining as much strength as possible. The tube will be used at the body of a radio-controlled airplane. Where should the holes be (what part of the tube), how big, and what...

Hello Let's consider a Schwarzschild BH. A photon (or a massive particle) crossing the event horizon cannot be static : the r (radial) coordinate becomes a temporal coordinate. Therefore, the photon falls towards the central singularity (r=0). There is no way for him to escape : the...

OK, this is a long one. Black holes are a singularity, right? As is, their dimensions are 0mX0mX0m? That is why their gravity is so strong, because objects can get much closer and thus make the distance between them 0 and force of gravity infinite. In order for this to be possible, there...

Homework Statement Hi all. Say we are looking at a (pure) semiconductor at T=0 K. Now we turn on the heat, so only 1 electron jumps up to the conduction band per cm3, and likewise 1 hole is created in the valence band per cm3. Does this mean that the current density of this semiconductor is...

Q: do jets from Black Holes carry away the momentum from Black holes - in any form? Is matter in these jets rotating? Or may be particles carry the same spin?

I have a rather simple question. Dark matter was first proposed because galaxies appeared to have more mass than was observable. That's fine. But then later, supermassive black holes were discovered to be at the center of every galaxy. That's billions of solar masses more in each galaxy than...

Homework Statement A square loop with resistance 15 ohms is placed perpendicular to a time-varying magnetic field; the loop is 8.2 cm on a side. The magnetic field is changing with a rate of 3.4 x 10^-1 T/s. (a) calculate the rate at which the magnetic flux threading the loop changes...

I have a question about black holes and energy but have no idea what to do. if someone could just point me in the right direction. the question asks to consider a mass spiraling into a black hole, starting with energy E=0 at infinity. I have to determine E of the object when orbiting the...

Homework Statement I have a question about black holes and energy but have no idea what to do. if someone could just point me in the right direction. the question asks to consider a mass spiraling into a black hole, starting with energy E=0 at infinity. I have to determine E of the...

I was reading an article about retrieving information from black holes when I came up with an idea. Please bear with me, as I am not a scientist (or even close) and know little physics vocabulary. A theory/hypothesis I read involves Hawking radiation retrieving information from the black...

I read an interesting article which asserts that the existence of black holes cannot be falsified, and therefore they do not qualify as science. Has anybody heard this argument before? Any comments?

I was wondering, novice that I am, whether there is any theoretical limit to the size of a black hole. I know there are supermassive black holes that are equivalent in mass to billions of stars. Could a black hole ever encompass a mass the size of our universe or perhaps even more mass? Could...

As I was reading Stephen Hawking's "The Universe in a Nutshell," I came across a discussion of Strominger and Vafa's p-brane model of black holes. Hawking describes that for certain classes of black holes, the p-brane model predicts that information that falls into the black holes will be...

I have a computer science background, so I don't know about this. Can somebody give me some recommendations on good introductory books about -String Theory - Wormholes -Black holes etc. I'm looking something for academics, not for general public. So maybe books for 1st year graduate...

Black Holes Relation To "Time" Hello All, Thanks for fielding my first question here. It looks as though "Physics Forums" will be a tremendous resource for me. This is not a homework question. Rather, I am working on a broadcast documentary. Is the concept of "time" (in the Newtonian...

second law of thermodynamics and black holes ?! I am having a hard time thinking about the perservation of the second law of thermodynamics in black holes. If we throw a mass that have some level of disorder (entropy) into a black hole, it will disappear and that will appear to us as violating...

I have been thinking about this for a few weeks and can not come up with an answer. As I understand it a black hole is essentially a gravitational field so powerful not even light can escape it. The last part is what I don't understand. I thought light(photons) was massless. If light has no mass...

if black holes are supposed to suck everything how come gravitons are emitted. cause to attract something gravitons should come in contact with it.

Hello. Let me start off by saying that I am new here and that I am not actually a physics major. Still, this stuff interests me. So, I was watching this clip of that good ol' documentary about Stephen Hawking, And when Hawking was talking about how the image of something falling into...

In the perception of General Relativity a Black hole can form in which anything (including light) is trapped inside the horizon of the Black hole and can never escape, because nothing can exceed light speed. However, still something escapes the Black hole, which is the presence of the...

The limit of "Ultramassive" Black Holes. There is no limit, is there? Both these links show not a limit, but a regulation that slows the growth of a black hole, due to radiating most of its food away: http://www.newscientist.com/article/dn14653-how-big-can-a-black-hole-grow.html...

I don't have a formal education in physics so please excuse my ignorance. I had an idea and was wondering if as matter gets stretched and spun toward the event horizon is it possible that as it is consumed the weak force is repelled while everything else gets consumed? I hope that makes sense...

I am a horticulturist not a physicist, hence the reason I am seeking your help. I am currently drilling holes in a certain species of tree using a regular electric drill. (I do this to insert a special treatment - to explain why I do this would take many more words!). The density of the...

Well, I'll start off by admitting to having no formal education in this field, though advanced concepts across all scientific disciplines are a hobby of mine. I will also point out that others have observed that I have a knack for thinking outside of the box, especially when it comes to...

My question is threefold, the second is based on the premise that the first is true, and the third is based on the other two. 1. As relative velocity increases, mass also increases, correct? In this case, could you accelerate away from an object to a velocity fast enough to make its...

Hi, The way I understand it (and correct me if I'm wrong). Sometimes a star collapses on itself and forms a black hole. Floating around in space getting bigger as it pulls in whatever gets too close to esacpe it's gravitational field. What I don't understand is why a black hole is so...

Alright, According to the law of Conversation of Energy states that, Energy in a system may take on various forms (e.g. kinetic, potential, heat, light). The law of conservation of energy states that energy may neither be created nor destroyed. Therefore the sum of all the energies in the system...

Black holes and dark energy. which has more control over the other?

I apologize i do not know if this question makes practical sense i am only a person interested in physics, Is it possible to calculate a rough estimate of all of the matter being absorbed by all known black holes in existence , and than to even more generally estimate the amount of UNKNOWN black...