Črna luknja mora imeti maso in ta masa mora imeti premer. Mene zanima, ali je premer horizonta dogodkov pri črni luknji vačji ali manjši od premera črne luknje.
Če je premer horizonta dogodkov večji, ali bi se dalo krožiti znotraj njega okoli črne luknje po krožnicah kot okoli navadne zvezde?
Kroženje znotraj dogodkovnega horizonta
Lahko bi padal kot astronavti v orbiti, torej ne bi nikoli dosegel črne luknje (seveda tudi uiti ne bi mogel). 1. kozmična hitrost (hitrost kroženja) je manjša kot 2. kozmična hitrost (hitrost, potrebna da uideš). Če je 1. kozmična hitrost črne luknje manjša od c, potem bi lahko krožil.Krožiti v premeru ni možno, saj predmet ki pride v horizont pada proti črni luknji(ne vem s kakšno hitrostjo).
Tudi v članku piše, da se zate čas ne ustavi, ampak te samo drugi ne morejo videti.
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Gost
Pentium: povezava, ki sem ti jo napisal je FAQ o črnih luknjah in predlagam, da pozorno prebereš članke v njem.
Da pa ne boš predolgo iskal evo še tukaj definicija:
event horizon
The distance from a black hole within which nothing can escape. In addition, nothing can prevent a particle from hitting the singularity in a very short amount of proper time once it has entered the horizon. In this sense, the event horizon is a "point of no return".
Z drugimi besedami: zunaj horizonta lahko krožiš, znotraj pa ne.
Kar je pa zame pri črni luknji najbolj zanimivo je njen volumen. Kakšen volumen ima črna luknja, da lahko posrka na tisoče zvezd?
Odgovor je več kot fascinanten in pravi:
Our intuitive sense of volume breaks down in the strong gravitational region in a black hole. So while the "size" of a black hole is given by the radius of its event horizon, it's volume is not determined by the usual 4/3*pi*r3. Instead, relativity makes it more complicated than that. As you pass the event horizon, the spatial direction 'inwards' becomes 'towards the future'-- you WILL reach the center, it's as inevitable as next Monday. The direction outsiders think of as their future becomes a spatial dimension once you are inside. The volume of a black hole, therefore, is its surface area times the length of time the hole exists (using the speed of light to convert from seconds to meters). Since a black hole last practically forever, the black hole's volume is almost infinite. (This is also a way of explaining the fact that you can pour stuff into a black hole forever and never fill it up. Another reason why black holes never fill up is that the radius of the event horizon increases as the mass of the black hole increases.)
MP002
Da pa ne boš predolgo iskal evo še tukaj definicija:
event horizon
The distance from a black hole within which nothing can escape. In addition, nothing can prevent a particle from hitting the singularity in a very short amount of proper time once it has entered the horizon. In this sense, the event horizon is a "point of no return".
Z drugimi besedami: zunaj horizonta lahko krožiš, znotraj pa ne.
Kar je pa zame pri črni luknji najbolj zanimivo je njen volumen. Kakšen volumen ima črna luknja, da lahko posrka na tisoče zvezd?
Odgovor je več kot fascinanten in pravi:
Our intuitive sense of volume breaks down in the strong gravitational region in a black hole. So while the "size" of a black hole is given by the radius of its event horizon, it's volume is not determined by the usual 4/3*pi*r3. Instead, relativity makes it more complicated than that. As you pass the event horizon, the spatial direction 'inwards' becomes 'towards the future'-- you WILL reach the center, it's as inevitable as next Monday. The direction outsiders think of as their future becomes a spatial dimension once you are inside. The volume of a black hole, therefore, is its surface area times the length of time the hole exists (using the speed of light to convert from seconds to meters). Since a black hole last practically forever, the black hole's volume is almost infinite. (This is also a way of explaining the fact that you can pour stuff into a black hole forever and never fill it up. Another reason why black holes never fill up is that the radius of the event horizon increases as the mass of the black hole increases.)
MP002
Jst američanom vedno manj verjamem. Tudi uradni odgovori nase so včasih preveč "zavrti".
Če lahko delci uidejo iz Črne luknje (hawkingovo sevanje), se vse to podre. Če bi hitro dosegli singularnost, kot pravi članek, ne bi mogli uiti. Pravi Point of no return je pravzaprav singularnost.
Ne trdim niti da lahko delci uidejo, ampak da imajo črne luknje lahko tudi podsvetlobne 1. kozmične hitrosti.
Če lahko delci uidejo iz Črne luknje (hawkingovo sevanje), se vse to podre. Če bi hitro dosegli singularnost, kot pravi članek, ne bi mogli uiti. Pravi Point of no return je pravzaprav singularnost.
Ne trdim niti da lahko delci uidejo, ampak da imajo črne luknje lahko tudi podsvetlobne 1. kozmične hitrosti.
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Gost
The Question
(Submitted June 30, 1997)
How is it possible for to emit matter even if their gravity field is so intense?
The Answer
Black holes emit matter because their gravity field is so intense.
Specifically, black holes emit particles by a process known as Hawking radiation.
What is ordinarily considered empty space is full of 'virtual pairs' which are particle-antiparticle pairs which pop into existence, separate a very short distance, come back together, and disappear a very short time later. This happens so quickly that the Universe doesn't notice that for a short while there was extra mass-energy. The law of conservation of energy only holds over sufficiently long periods of time, and can be briefly violated.
In the neighborhood of a black hole, the virtual pair can pop into existence, and when they separate, one can go so deeply into the black hole that its falling releases enough energy that the other particle can continue to exist, outside the hole, with the total energy of the virtual pair being zero.
It takes a huge gravitational field to release such a large amount of energy when the particle falls such a very short distance. Such huge fields are found only around black holes.
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The Question
(Submitted November 25, 2001)
I have a little bit of a problem understanding Hawking radiation and evaporation. So far I have heard two different explanations for hawking radiation. One being the seperation of particle/antiparticle pairs due to the intense gravitational field of a black hole. The other being the escape of some particles because of quantum uncertainties in the velocity of subatomic particles which can allow a particle to briefly travel faster than light.
Also, my current understanding of black hole evaporation is that due to Hawking radiation black holes actually emit energy and will evetually evaporate away due to this loss of energy. This doesn't make sense in the context of the partricle/antiparticle type of Hawking radiation. It seems the black hole should actually increase in size because it is actually gaining matter/energy through this process. The particle/antiparticle pair is not actually part of the black hole but borrowed energy. Can you please make sense of all this for me?
The Answer
Thanks for your question. You are correct that there are multiple ways to visualize the generation of Hawking radiation. The first is indeed the separation of virtual matter/antimatter pairs by the intense gravitational force exerted by the black hole and the other is the quantum tunneling of a particle, such as a photon out of the black hole event horizon.
Both cases describe black hole evaporation. The best way to think of why indeed the black hole is losing energy in the matter/antimatter scenario is that particles are actually created at the expense of gravitational energy (which is then related to the properties of space-time). Consider the following example. Say there's a particle moving toward a large mass --the particle feels the gravitational pull of the mass. The gravitational field exerts a potential energy on the particle which in turn is converted to kinetic energy of the moving particle. To conserve total energy the potential energy of the mass gets more negative. Indeed, the mass experiences a loss of potential energy as the particle experiences a gain in kinetic energy. So in the same way, at the black hole event horizon, two virtual particles --say photons --separate due to the gravitational force of the black hole; one adds negative energy as it falls into the black hole, the other (now a real particle) escapes.
Mah.. jst mal dvomim, da američani kujejo kake zarote s črnimi luknjami
MP002
(Submitted June 30, 1997)
How is it possible for to emit matter even if their gravity field is so intense?
The Answer
Black holes emit matter because their gravity field is so intense.
Specifically, black holes emit particles by a process known as Hawking radiation.
What is ordinarily considered empty space is full of 'virtual pairs' which are particle-antiparticle pairs which pop into existence, separate a very short distance, come back together, and disappear a very short time later. This happens so quickly that the Universe doesn't notice that for a short while there was extra mass-energy. The law of conservation of energy only holds over sufficiently long periods of time, and can be briefly violated.
In the neighborhood of a black hole, the virtual pair can pop into existence, and when they separate, one can go so deeply into the black hole that its falling releases enough energy that the other particle can continue to exist, outside the hole, with the total energy of the virtual pair being zero.
It takes a huge gravitational field to release such a large amount of energy when the particle falls such a very short distance. Such huge fields are found only around black holes.
################
The Question
(Submitted November 25, 2001)
I have a little bit of a problem understanding Hawking radiation and evaporation. So far I have heard two different explanations for hawking radiation. One being the seperation of particle/antiparticle pairs due to the intense gravitational field of a black hole. The other being the escape of some particles because of quantum uncertainties in the velocity of subatomic particles which can allow a particle to briefly travel faster than light.
Also, my current understanding of black hole evaporation is that due to Hawking radiation black holes actually emit energy and will evetually evaporate away due to this loss of energy. This doesn't make sense in the context of the partricle/antiparticle type of Hawking radiation. It seems the black hole should actually increase in size because it is actually gaining matter/energy through this process. The particle/antiparticle pair is not actually part of the black hole but borrowed energy. Can you please make sense of all this for me?
The Answer
Thanks for your question. You are correct that there are multiple ways to visualize the generation of Hawking radiation. The first is indeed the separation of virtual matter/antimatter pairs by the intense gravitational force exerted by the black hole and the other is the quantum tunneling of a particle, such as a photon out of the black hole event horizon.
Both cases describe black hole evaporation. The best way to think of why indeed the black hole is losing energy in the matter/antimatter scenario is that particles are actually created at the expense of gravitational energy (which is then related to the properties of space-time). Consider the following example. Say there's a particle moving toward a large mass --the particle feels the gravitational pull of the mass. The gravitational field exerts a potential energy on the particle which in turn is converted to kinetic energy of the moving particle. To conserve total energy the potential energy of the mass gets more negative. Indeed, the mass experiences a loss of potential energy as the particle experiences a gain in kinetic energy. So in the same way, at the black hole event horizon, two virtual particles --say photons --separate due to the gravitational force of the black hole; one adds negative energy as it falls into the black hole, the other (now a real particle) escapes.
Mah.. jst mal dvomim, da američani kujejo kake zarote s črnimi luknjami
MP002
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Gost
Ma Pentium, ti si majstor!
No, a vidiš, da ni zarot?
Mimgrede: kot "point of no return" je mišljen event horizon...
Preden dosežeš singularnost si že dezintegriran...
(Vsaj jst tko razumem to stvar...)
BTW: Ej, svaka čast, če si osnovnošolec... Jst sm se lotu zdej tuhtat mal te stvari in moram priznat, da se že pri 3D prostoru (+čas) zgubljam...
Še dobro, da imam Romana, da mi mal pomaga v tej zagati...
Nč, grem v toplice čez vikend, ker to me že dela mal bolanga...
No, a vidiš, da ni zarot?
Mimgrede: kot "point of no return" je mišljen event horizon...
Preden dosežeš singularnost si že dezintegriran...
(Vsaj jst tko razumem to stvar...)
BTW: Ej, svaka čast, če si osnovnošolec... Jst sm se lotu zdej tuhtat mal te stvari in moram priznat, da se že pri 3D prostoru (+čas) zgubljam...
Še dobro, da imam Romana, da mi mal pomaga v tej zagati...
Nč, grem v toplice čez vikend, ker to me že dela mal bolanga...
Ne, tu ni nobenih zarot, kot so bile pri GRB. Nasa vse pojasnjuje s SM, jaz se pa z njim ne strinjam in iščem druge poti. Če je Point of no return v resnici horizont, potem se ne bi dalo priti iz njega. Seveda živ ne moreš priti noter, ker te plimska sila raztrga, ampak če lahko uide foton, lahko karkoli. Kolikor vem se v singularnosti čas povem ustavi, na horizontu pa postaneš neviden le za zunanje opazovalce in zate čas še teče.
Pa še ena zares drzna domneva: Ni nujno, da je v vsaki črni luknji singularnost.
Pa še ena zares drzna domneva: Ni nujno, da je v vsaki črni luknji singularnost.
Singularnost
Kdo pravi, da velja v črni luknji singularnost?Pentium napisal/-a: Pa še ena zares drzna domneva: Ni nujno, da je v vsaki črni luknji singularnost.
Singularnost velja samo za skrajni rob črne luknje! Na drugi strani tega robu zopet vlada čas.
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Saj je čisto preprosto!Pentium napisal/-a:Ker je singularnost v samem središču črne luknje, "Na drugi strani tega robu" enostavno sploh ni ne prostora ne časa, torej ni nič.
1)Če pade nekaj v črno luknjo se masa črne luknje poveča.
2)Torej se masa črne lukne po času spreminja.
3)Torej čas za črno luknjo obstaja saj se njena masa po času spreminja.
4)Masa oziroma energija, ki prileti v črno luknjo se mora po njej nekako prorazporediti, kar pa je zopet dinamičen proces, ki upliva na samo ukrivljenost prostora. Iz česar sledi, da obstaja čas tudi znotraj črne luknje.
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Pentium še enkrat:
Nič je abstrakten pojem in nima z realnostjo nič skupnega. Nič v realnem svetu ne obstaja. Nič obstaja zgolj v abstraktnem svetu.
Dobra ideja 
, to je eden od dokazov o pravilnosti moje domneve. Če noter obstaja čas, potem obstaja tudi prostor in nedoločnosti v njem.
Ja, tisto s singularnostjo si imel prav, samo ni "na drugi strani", ampak "okoli" singularnosti. Singularnot ne velja za skrajni rob črne luknje, ampak za skrajno središče, mogoče za rob prostor-časa (če upoštevaš našo predstavo prostor-časa, v kateri drugi je mogoče tudi na drugi strani kaj).
, to je eden od dokazov o pravilnosti moje domneve. Če noter obstaja čas, potem obstaja tudi prostor in nedoločnosti v njem. Ja, tisto s singularnostjo si imel prav, samo ni "na drugi strani", ampak "okoli" singularnosti. Singularnot ne velja za skrajni rob črne luknje, ampak za skrajno središče, mogoče za rob prostor-časa (če upoštevaš našo predstavo prostor-časa, v kateri drugi je mogoče tudi na drugi strani kaj).