Black holes Definition and 1000 Threads

so i had this idea for a while now, if you would take a black hole, and put a laser next to the event horizon, facing away from the black hole, the gravity from the black hole would pull the photons in right? I was thinking that the force that it takes must be bigger than the power from the...

This paper relies heavily of LQG self-dual black holes ; I saw an old thread here about didn't find the answer there so here's my question : On the face of it this looks like a somewhat bizarre/exotic theoretical solution, especially with the description referring to wormholes. However, since...

I'm curious about what others think. As I believe that you fall indefinitely in a black hole, and since you don't feel the gravity when falling, you fall until your incinerated by faster moving electromagnetic radiation falling on you. But you can only see what is above you, assuming your eyes...

For example a black hole is stable. As in Ts=Tu then what would be the uses of the BLACKHOLE. Would it have any such use ?

is a dark matter black hole possible, and what would it be like ?

this is the idea...

Hi PF I am reading an old Rovelli paper http://arxiv.org/abs/gr-qc/9603063 Rovelli computes the entropy of a black hole. He says two things. a) A state is described with an equivalence class of s-knots. b) the entropy of a black hole can be computed by counting the number of the intersection of...

The early universe would appear to be contain more material per unit volume than now.This would then gve rise to a first generation big stars and an early develoment of supernova. My interest lies in the inevitable momentum that would be transferred by slingshot from pairs or groups of black-...

Suppose you have a source of electron antineutrinos, and you arrange your apparatus so that a billion billion billion of them collide directly with a black hole. In principle, you could measure the change in momentum and energy from that occurrence. Suppose you did that the next day. According...

I recently saw "Interstellar", a pretty good movie with well done depictions of worm holes and black holes. This inspired me to dig out my book on black holes (thinking it was written by John Wheeler). I've had the book for years and had read the first couple hundred pages about 10 years ago...

Can anyone tell me how energy created via the Penrose process can be extracted and converted into useable energy? What kind of infrastructure would we need on Earth, in space, etc.? Many articles talk about how energy can be created through the Penrose / Blandford–Znajek process, but none...

This might be well known or even discussed here, though I couldn't find a thread about it, but the questions is what are the possible topologies of a black hole i.e. the topology of a spatial slice of the event horizon. I know there is a result of Hawking that says the topology has to be that of...

If photons have no mass, why would black holes attract light? I was told that photons have no mass. However I thought that black holes are called "black" because no light can go escape the gravity force in their vicinity. I somehow think that, if light is just photons, then it should not be...

I recently viewed a video with Richard Carrier, who apparently was using information he derived from Lee Smolin. He said that 99.9999% of the matter in the universe goes to making black holes. Is this true? What percentage of matter does go to the making of black holes, is it even something we...

Black Holes Inch Ahead To Violent Cosmic Union -- Dennis Overby NY Times article today on merging black holes. Describes possible observation, implications of a pair of merging black holes. Suggests lots of research possibilities for gravitational wave astronomy. Some specific research is...

This is wild speculation but wild speculation is fun; Do micro black holes bend space and time like their bigger siblings? Could you then use the curvature of time of such a micro black hole and a radio transmitter to send a message back through time? Regards, JDM

So I understand that as a star begins to die, and begins fusion of H, He, C, O... it eventually reaches Fe which cannot be fused to create energy. Then the stars own gravity overcomes it's outward radiation and the star implodes, and eventually a black hole is created. How can the star's...

What exactly is this mass inflation instability phenomenon that is said to happen near the inner horizon of black holes? http://jila.colorado.edu/~ajsh/insidebh/realistic.html I got the nutshell of it, but I think I need someone to really explain this.

If you had a planet with the exact same mass and radius as the Earth, and adjusted the gravity constant to some value five-hundred million times larger, the schwarzschild radius should become considerably big, right? Instead of being about 8 millimeters, it would now be about 60 to 70 percent...

I have a problem with the concept of a singularity, defined as something that has a property which is infinite. Infinities do not belong in our reality, and in my opinion are just hints that our understanding of the phenomenon is incomplete or wrong. From my understanding, during the collapse...

Hello. If at the event horizon..the escape velocity exceeds the speed of light..or time at that 'point' comes to a halt..how can anything get past or thru the horizon and make the journey to the center of a black hole? Thanks for any and all your responses. Bye SC

I was thinking of the conditions exerted at the center of our Earth. If a man let's say in America falls toward the Center of the Earth and a man on the opposite side of the Earth falls, where would they meet? I read that the gravitation force at the center of the Earth is at 0. If they both...

I was wondering if the run away gravity in a super massive black hole could cause a lock up of sorts, and stop (nearly) all atomic movement? Packing the matter at it's core so tightly, that it would paralyze it at an atomic level. Could this possibly mean that near the center of these monsters...

So in 2009 there was this paper which described what was known back then based on observational data and the final sentence in the conclusion read as follows: Now for you astrophysicists here, has anything changed? It is my understanding, and please correct me if I'm wrong, that as of 2013...

I have always wondered various questions, out of which these 3 below are on the priority list including a previous topic I questioned here ofcourse without any answer to it. I am no science guy by the way, just curious! So the questions are: 1. Can a black hole contain a wormhole inside of it...

I have a question about equation 10.21 in "Exact Space-times in Einstein's General Relativity" by Griffiths and Podolski. The equation is the well know standard metric for multiple extreme Reissner Nordstrom black holes. It has the below term: (1+ sigma(mi/ri)) The point ri = 0 is of course...

Supposing a man named Bob falls into a black hole, an instant of Bob's perceived time would be a nearly infinite amount of time to the rest of the universe due to relativity and the effects it has in and near black holes. Okay sure, but we also know (to my knowledge) that black holes "evaporate"...

Smolin has a theory that black holes in our Universe result in new Universes. He says Universes that are capable of creating black holes get to produce more Universes etc. http://www.space.com/21335-black-holes-time-universe-creation.html I was reminded of Smolin's ideas by this recent...

Hello anyone who can answer. I have a question concerning dark energy (Please realize that my knowledge is limited on this subject) It is known that the universe is expanding at an accelerating rate, scientists say this is due to the mysterious dark energy. It seems to go against our...

If the star's mass supposedly collapses into a single point, and it ends up having "said" zero volume, then how can people say that the hole has a specific spin or that it can have an angular momentum? Does it mean that the singularity is somehow still spinning, or maybe the spacetime around it...

If you only knew the temperature of the black hole, like, if for example, the temperature of a 4 solar mass black hole being around 1.5e-8 kelvin, how could you possibly be able to calculate what wavelengths of radiation the black hole would give off? Would a black hole like this really only...

As a writer, light is as crucial as it is to physicists. But I'm struggling with some conceptual understanding surrounding light. If you could supply any answers to this science layman I would be very grateful. 1) Without light there is no way of observing and measuring. So light is both itself...

Hi there! After giving a thought about this phenomena I came with some doubts and I thought that maybe it was a good idea to put them all together in one thread so I don’t star many discussions simultaneously and also because maybe their answers are related. So here I go: a) As they...

Homework Statement Show that from (*) that for a nonrelativistic Maxwell-Boltzmann gas, n=g\bigg(\frac{nkT}{2\pi\hbar^2}\bigg)^{\frac{3}{2}}e^{\frac{\mu-mc^2}{kT}} P=nkT e=nmc^2+\frac{3}{2}nkT Homework Equations (*): f(E)=e^{\frac{\mu-E}{kT}} E=\sqrt{p^2c^2+m^2c^4} n=\frac{g}{h^3}\int...

Homework Statement Hello, I try to recompute all exercises in this book and sometime I hit the snag :) One of the first is: Exercise 2.6 (page 28) Show that mean kinetic energy of an electron in a degenerate gas is \frac{3}{5}E'_f in the nonrelativistic limit and \frac{4}{5}E_f in...

Homework Statement Exercise 2.6 (page 28) Consider completely ionized matter consisting of hydrogen, helium, and heavier atomic species i>2. Let X and Y denote the fractions by mass of hydrogen and helium, respectively. Show that \mu_e=\frac{2}{1+X}. Approximate m_i=A_i m_u for all i, and...

i understand that a black hole occurs because the atoms are not strong enough to hold back gravity after a certain point. is the matter continually collapsing on itself or does it stop after the atoms have been crushed? like is it a runaway effect? my next question is why does a large mass in...

Hi i have a few questions about black holes. Are black holes just stars that are so big, and have so much mass that no light can escape them? Do black grow in size, or are they just an infinite small point of space?¨ Can black holes die? are they actual holes, or are they spherical? can you...

Can an observer, freely falling into a black hole observe another black hole, falling with him, after crossing horizon? I assume one should be, as for freely falling observer nothing special happens, when he crosses horizon. But just wanted to double-check.

Is it possible for our solar system to be located inside a black hole which is our galactic centre?

I recently read a few articles that contradict Einstein's Singularity theorem. The idea being that black holes are wormholes to other universes; with a white hole on the other side of the black hole (Poplawski's theory). What if instead of being a portal to another universe, the Event Horizon of...

I was reading "Black Holes and Time Warps" by Kip Thorne, and right around p.442-443 it talks about how the quantum vacuum fluctuations that give rise to Hawking radiation from an infalling frame of reference give rise to an "atmosphere" of real, non-virtual particles in an accelerated frame...

Seriously, a 5 year old asked me whether entanglement information survives/escapes a black hole. Specifically, he asked me (in only slight paraphrase) whether if one of the particles (headed in different directions) fall into black holes on either end, does the other one know it?

As I understand it, the Hawking radiation is produced when a pair particle-antiparticle are produced at a place close to the event horizon of a black hole, so that one of them, energy-negative for a distant observer, is swallowed by the hole, and the other appears as 'black hole radiation'. I...

I'm a bit confused about the derivation of the Schwarzschild radius. I can do it quite easily using Newton's Law of gravitation, but this law is only an approximation, so I am wondering whether the result I obtain, r_{s}=\frac{2GM}{c^{2}}, is an approximation or not. It seems to me that it...

I was thinking about this and either I have a misunderstanding of black holes or they are simply not how the standard model proposes them to be. Lets start out by setting a few a statements from the standard model that you agree with. If you disagree about any of these points please comment so...

I have for you a simple proof that black holes do not destroy information, since wikipedia seems to be stating that it's an unsolved problem. http://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics 1. The second law of thermodynamics states that entropy must always increase. 2. If...

Why we talk and discuss about effects on light cones by black holes though we know there is no light left after a star dies and become a black hole? there should be no light and so no light cones...

Has there been any evidence of black holes converging? What would we expect to see , if anything?

I'm only a freshman in college, but I am always thinking about the future. I plan to earn my Bachelor's in Physics or Astrophysics, and then continue onto graduate school. I'm at Penn State University, so I plan to stay here for all of my degrees unless a better, more valuable opportunity...