Hole Definition and 1000 Threads

Following a Big Bang, if the Universe expanded at the speed of light, then the Laws of Physics would have come into play long before the radius of the Universe passed it's own Schwarzschild radius. Does that mean the Universe cannot keep expanding forever ? or maybe that we exist inside a...

Hello, I am new to this forum! I have only just completed my first physics class, but I like to learn about some of the more advanced topics in physics on my own time. I was watching a video about black holes and I noticed a part of the video that stated "any matter that enters this...

I have a part with a 2.5mm hole that sits inside a fixture (I need to verify hole presence), the hole can move anywhere around the slotted area due to part flexing, install force, etc. One idea I had was point an 850nm InfraRed light from the other side at the hole, then mount an IR light...

I had a discussion regarding the region of spacetime visible to an observer falling into aSchwarzschild black hole. Using Eddington-Finkelstein coordinates this is rather straightforward, at least graphically. However the situation is rather artificial b/c the BH exists externally. So my...

I think black holes are amazingly interesting and I hope we get some answers about what they are in the future. I have a question I hope someone can help me with. The Schwarzschild radius is the radius at which the gravity becomes so strong there is no going back right? Is there an equation...

I'm reading Einstein's Cosmos by Michio Kaku, and he describes Kerr black holes; which are apparently rings of matter stabilized by centrifugal force. Anyway, Kaku throws out that if you go through the event horizon of a black hole, you will be transported to another universe; he says this as if...

How do we know which one is a black hole solution(metric) or a wormhole solution(metric)? what is its feature?

Here is a set of pictures showing the ways electrons and hole move under electric field. Can anyone tell me how the hole will move after this? I mean that where the hole will move after the final image.

When a black hole is formed officially from a collapsing star (consider the simplest case of spherically symmetric collapse of non-rotating spherical star)? I see two possible answers: 1) At the moment when the radius of the star crosses the event horizon (##r_{star}=r_s##) , but the...

So I always hear that the density of a black hole is infinite, because it's volume is zero. How can this be if, in mathematics, n/0 ≠ ∞? Would it be more correct to say a black hole's density is undefined or indeterminate? I also hear that some people say that a black hole's volume is...

Homework Statement This was a problem on a test today, and it is driving me nuts that I cannot figure it out. We were told that we had a bucket 1 meter off of the ground with a 3.5 mm hole in the bottom. The water sprayed a horizontal stream 60 cm from the bucket. We are asked to find the...

Even before I had seen a Kaku documentary on black holes creating new universes, perhaps with different physics on the other side of them, I had had this image that the Big Bang was caused by a collapsing point singularity in a parent galaxy. Surely there must be something wrong with this...

For intrinsic semiconductor, the know its conductivity=2 neμ , where his the number of electron per cubic meter, e is the charge of an electron, μ is the electron mobility. But if I want to calculate the conductivity of a conductor= neμ. Why not consider the hole in? Electron leaves its...

I have been fascinated by stars and Black holes for most of my life but one of the things I can't get a satisfactory explanation on is what gives a Black Hole it's mind boggling gravity. We know that a Black Hole cannot be seen because it's gravity is so great that not even light can escape it...

I have a basic question. It is well known that according to "our" time (time measured by an observer in flat space-time), an object falling into a black hole will never cross the event horizon (though, of course, according to its "proper time" it will fall into the singularity in a finite time)...

I am currently working myself into black hole physics and I am interested in their possible quantum geometric description by means of LQG. Can anybody please tell me good sources to start with? Since black holes were studied in this framework for a longer time, what is the most recent...

I have a very simple question. If a hole is made at the center of a metal plate and it is heated to increase its temperature, will the hole increase in size or decrease?

I want to know what is the shape of a Black Hole? Is it round like a globe, or is it flat or oval shaped?

I hear that black holes evaporate, but does it all get converted into Hawkins radiation? And what role do white holes play in evaporation?

Little thought experiment. Hypothetically let's say I'm standing on the surface of an imaginary black hole and not completely crushed to death, or better yet, I'm in the center of the thing (never mind the singularity) and looking outward into deep space. Is the light coming toward me red or...

Hello All, I have a fixture that is used for lifting an engine. See attached image for the part in question. You can see in the 'front' view the hole where a pin passes through the part and the lifting lug of the engine. You can also see the loading. We want to machine the part down such...

If two stars, both slightly above their Schwarzschild radius collide, can a joint horizon form before they come in contact? What if one is matter, and the other the same amount of antimatter? Will they annihilate each other completely to pure radiation, which stays within the horizon? Would...

white hole in universe! isn't the center of universe a white hole?( i think)As the center of universe is throwing matter radially(if it is a white hole) outwards at high speed,we are moving away from the centre.This is nothing but the term "expanding universe". does this make sense? thanks.

The solution of Einstein's field equations for a simple black hole show a slowing of time as you get close to the black hole. Time stops at the event horizon. An observer in flat spacetime far from the hole would see an astronaut fall slower and slower as he approaches the event horizon. It...

I have a tube with a rod inserted into it at a set depth. The rod is held in place by a round pin that passes through a hole in the side of the tube and into the rod. Assuming the pin and hole are the same diameter or very close, I'd like to know how to calculate the stress area on the edge of...

When the sun is collapsed will it form a black hole?

How can a black hole have a high entropy state if the matter inside it is in a supercondensed form with maximum density,which means less degrees of freedom therefore less entropy than normal matter.Like in neutron stars we have low entropy with the neutron degenerate matter and yet a black hole...

Is there any such thing? Or is it unphysical? If it's physical, would making contact with a matter black hole result in E=mc^2? Thanks.

How can two Black holes fusion and consist a supermassive Black Hole ?!

Homework Statement Determine the reaction force from water flowing through a clean 0.02cm (Diamater assumed) hole in tank depth 3m Homework Equations P = rho.g.h A = Pi.R^2 P=F/A The Attempt at a Solution P = rho.g.h = 29400 Pa A = Pi.R^2 = 0.00031415 m^2 P = F/A -> F = PA =...

Could intraband transition (in metals) of an electron in the conduction band produce a hole there?

In a recent lecture by Stephen Hawking he mentions that our universe started as a singularity. Can this singularity be caused by energy from a Black hole in another space and time? This in turn would mean that an infinite number of universes can be and are created.

Hi I just listened to Leonard Süsskind Lecture 7 on youtube about General Relativity in the following link. At 1:28:00 he mentioned, that if a object is very close to the surface of a black hole, then the matter at this point would bulge out until it get completely absorbed. I don't...

Hey, before people start throwing rotten vegetables at me, I'm not any good in general relativity! So my question is: are black holes transparent to electromagnetic waves of wavelengths on the same order as the Schwarzschild radius of the BH?

I assume people much more knowledgeable then me must have already thought this through, but the following line of thought has me very curious. I'm making a lot of intuitive leaps here though, so I am sure there is a lot of places I could have gone drastically wrong. Hawking radiation is...

What blue shift of distant light would you observe, while free falling into a black hole. It seems that hovering at the horizon (which is not possible), would result in infinite blue shift. But what about the observed blue shift in free fall, as a function of the radial Schwarzschild coordinate?

What is the maximum approximate black hole size that would have negative growth rate as a function of average local mass density (and/or any other relevant parameters)? In other words, when does an evaporating black hole become a growing black hole and vice-versa? Cheers Eric

If a small round black hole is traveling normal to the center of the major plane of a larger toroidal black hole, is it possible any energy will "get thru" to the other side of the toroid? . It's said that once you wander into a BH, you can't get out. It's like a tar pit but worse. Maybe...

This scenario is described by Lenard Susskind in a lecture on general relativity starting at time stamp 44:23 in the following video. The scenario is that a spherical shell of radiation is directed inward to a point. The shell contains enough energy to form a black hole. He states that...

Most explanations of doping, coupled with the simple definition of hole as positive charge carrier, and reinforced by classic graphic illustrations of P- and N-doped regions full of little plus and minus signs respectively, makes for a common point of confusion when learning basic semiconductor...

i heard when 3 black hole crash one which come latter will pushed away and two wil become one big black hole here, why black hole pushed away?? im korean so i cannot write exactly sorry

Gravity on Earth is 9.8m/s² and on the moon I believe it's 1.6m/s² so I'm wondering how much gravity a black hole has? What is the minimum force of gravity needed to bend space-time, do we know? Is there a formula? Also how far from the black hole would you have to be before you no longer feel...

Now what I'm about to say may sound like a sort of speculation but not in the typical bad way. Now we have a black hole in universe somewhere.(Doesn't matter where for my theoretical purposes) Now we know that once a big star looses all or most it's fusion elements and some of it's mass that...

I watched this documentary about an argument involving information loss in a black hole, Stephen Hawking managed to wind everybody up by claiming information was lost and therefore broke existing laws of physics. Its an old recording so it may not be relevant anymore but one part of this...

Challenge: Can anyone tell me how to cut a hole in a sheet of normal Book paper the size through which even an elephant can pass...?

Hey I heard from a couple differnt places on the internet that there's a possibility that a black hole hypothetically could be formed by the LHC. I thought that black holes were formed by the implosion of a huge star that keeps going in on itself due to gravity. Is it true that this could happen...

A clump of matter does not need to be extraordinarily dense in order to have an escape velocity greater than the speed of light, as long as its mass is large enough. You can use the formula for the Schwarzschild radius Rs to calculate the volume 4/3piRs^3 inside the event horizon of a black hole...

I found this extremely handy reference on Black hole calculations and models to measure black hole accretion disk/jets. The article also covers several types of BH non rotating and rotating. Methodologies that can be used to distinquish between Neutron and black hole event horizons...

Is there some material that could withstand relatively high voltages before it starts to conduct electrons,but in the same time a good hole conductor? Could such material be obtained by doping some dielectric similar to SiO2?

If black holes crush things into infinite density, shouldn't they all be the same size?