Black Holes

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harry
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Post by harry » Wed May 21, 2008 9:56 am

Hello Doum

The links that I post will have ideas that I may not agree with. I post them for interesting reading.

As for singularity, it does not exist in the true sense of the definition. A single infinite point.

But! a singularity where all the matter forms one unit a Nucleon, probably a Neutron Matrix, maybe the thoretical quark of preon-particles or composite forming a finite compact core is possible. This core is a plasma and thus we are able to apply plasma properties.

As for the Z-pinch, what do you know of it? It is worth researching the information.

The Z-pinch is the main process of forming the Jets.

====================================

http://ieeexplore.ieee.org/Xplore/login ... ber=199547
A new hypothesis of cosmic ray generation in plasma pinches
Trubnikov, B.A.
Plasma Science, IEEE Transactions on
Volume 20, Issue 6, Dec 1992 Page(s):898 - 904
Digital Object Identifier   10.1109/27.199547
Summary:A hypothesis for the birth of galactic cosmic rays in cosmic plasma pinches resulting from neck-type contractions that force plasma to jet outward is presented. It is shown that the accelerated particle energy, E, has a power law dependency dN/dE~ E-s with index s=1+√3=2.732 at the moment of neck breaking or pinch disruption. This value coincides with an observed galactic cosmic ray index s=2.7. This result corroborates other evidence for the existence of electric currents in cosmic plasma
==========================================


http://ieeexplore.ieee.org/Xplore/login ... pdf?temp=x
The Z-Pinch Morphology of Supernova 1987A and Electric Stars
Thornhill, W.
Plasma Science, IEEE Transactions on
Volume 35, Issue 4, Aug. 2007 Page(s):832 - 844
Digital Object Identifier   10.1109/TPS.2007.895423
Summary:Supernova 1987A (SN 1987A) is the closest supernova event since the invention of the telescope. It was first seen in February 1987 in the nearby Large Magellanic Cloud, which is a dwarf companion galaxy of the Milky Way and only 169000 light years from Earth. The Hubble images of the rings of SN 1987A are spectacular and unexpected. The ldquobeaded ringrdquo pattern of brightening is not well explained as an expanding spherical shock front into an earlier stellar ldquowind.rdquo The axial shape of SN 1987A is that of a planetary nebula. It seems that new concepts are required to explain supernovae and planetary nebulae. The new discipline of plasma cosmology provides a precise analog in the form of a Z-pinch plasma discharge. The phenomena match so accurately that the number of bright beads can be accounted for and their behavior predicted. If supernovae are a plasma discharge phenomenon, the theoretical conditions for forming neutron stars and other ldquosupercondensedrdquo objects are not fulfilled, and plasma concepts must be introduced to explain pulsar remnants of supernovae. If the bipolar Z-pinch pattern is introduced to explain supernovae and planetary nebulae, a new electrical theory of stars is required.

========================================

http://www.osti.gov/energycitations/pro ... d=15002744
US Department of Energy (US)
29 ENERGY PLANNING, POLICY AND ECONOMY; 43 PARTICLE ACCELERATORS; ACCELERATORS; ASTROPHYSICS; BLACK HOLES; CLOUDS; ENERGY DENSITY; EQUATIONS OF STATE; HYDRODYNAMICS; LASERS; MACH NUMBER; RADIATIONS; RELATIVISTIC PLASMA; SUPERNOVA REMNANTS; SUPERNOVAE
Over the past decade a new genre of laboratory astrophysics has emerged, made possible by the new high energy density (HED) experimental facilities, such as large lasers, z-pinch generators, and high current particle accelerators. (Remington, 1999; 2000; Drake, 1998; Takabe, 2001) On these facilities, macroscopic collections of matter can be created in astrophysically relevant conditions, and its collective properties measured. Examples of processes and issues that can be experimentally addressed include compressible hydrodynamic mixing, strong shock phenomena, radiative shocks, radiation flow, high Mach-number jets, complex opacities, photoionized plasmas, equations of state of highly compressed matter, and relativistic plasmas. These processes are relevant to a wide range of astrophysical phenomena, such as supernovae and supernova remnants, astrophysical jets, radiatively driven molecular clouds, accreting black holes, planetary interiors, and gamma-ray bursts. These phenomena will be discussed in the context of laboratory astrophysics experiments possible on existing and future HED facilities.

=====================================

http://www.thunderbolts.info/tpod/2006/ ... mpinch.htm

Nov 06, 2006
Pinch Yourself!

Simple experiments can demonstrate the principle of the “z-pinch” that electrical theorists say is the best explanation of the hourglass shape of many bipolar nebulas.

=====================================

Plasma
The Fundamental State of Matter
http://www.electric-cosmos.org/electricplasma.htm
Quote:
The Z-Pinch
Electric current, passing through a plasma, will take on the corkscrew (spiral) shape discovered by Birkeland. These Birkeland currents most often occur in pairs. There is a tendency for these pairs to compress between them any material (ionized or not) in the plasma. This is called the "z-pinch" effect. The ability of Birkeland currents to accrete and compress even non-ionized material is called "Marklund convection".


Quote:
Double Layers
One of the most important properties of any electrical plasma is its ability to "self-organize" - that is, to electrically isolate one section of itself from another. The isolating wall is called a double layer (DL). When a plasma is studied in the lab, it is usually contained in a closed cylindrical glass tube. Electrodes are inserted into the ends of the tube - one electrode (called the anode) is maintained at a higher voltage than the electrode at the other end (the cathode). If such a voltage difference is applied, then ionization will be initiated and current will start to flow through the plasma. Positive ions (atoms with one or more electrons stripped off) will migrate away from the anode, and negative ions (atoms carrying one or more extra electrons) will move toward the anode. The mathematical sum of these two oppositely directed flows constitutes the total current in the plasma.
Harry : Smile and live another day.

Doum
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Post by Doum » Thu May 22, 2008 12:35 am

Hi Harry,

You said: "As for the Z-pinch, what do you know of it? It is worth researching the information."

Well what i know is about the trying for humankind to produce a control nuclear fusion reactor to produce energy for all mankind. But the way you ask me what i know is like i should not read about those Z pinches. Is it bad to learn how the Z pinches can be use by human. They discover the Z pinches for nuclear fusion. That's what i know. Now that may apply for astronomy of course. But i dont know. So i ask. Does it apply for an accretion disc aroud a black hole.

Here is a link i found for Z pinches in astronomy:

http://www.newscientist.com/article/dn6 ... -jets.html

And here are many scenario writen in it about the jet.

"The jets are thought to be powered by black holes with masses of a billion Suns. But astronomers cannot agree on how the jets form.

In one leading theory, the jets begin in an accretion disk of ionised gas, or plasma, around the black hole. The plasma's charged particles create magnetic fields as the disk rotates, and those fields push gas and radiation out at the poles of the black hole.

In a competing theory, the jets begin closer to the black hole – and are caused by the wild spinning of the black hole itself. Black holes are so massive that if they rotate, they are thought to drag the surrounding space and time along with them. This blurred region at the edge of the spinning behemoths also twists the magnetic fields generated in the accretion disk as the gas in the disk falls toward a black hole.

It is this confused region of twisting which is believed to spew out the jets."

"The spinning twists up the magnetic field like a barber pole and the plasma is lifted out along the rotational axis," says David Meier, an astrophysicist at NASA's Jet Propulsion Lab in Pasadena, California, who has worked on previous simulations

But other researchers say the jets' source is still up for debate.

He calls the new work "interesting" but says he has identified seven different scenarios for magnetic fields - some of which cross into the black hole itself - that could cause the jets. "I honestly don't know what the answer is

So there is at least 7 differents scenario for the jet to be create. Hmm then only time will tell wich one is the correct one or how many of them work together to do the jet. Cya!

Oups it is not about Z pinches. :shock: :lol:

Yea Harry Z pinches might apply. I just dunno. So i do read about it. But it is far from being the only one scenario.

harry
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Post by harry » Thu May 22, 2008 8:28 am

Harry : Smile and live another day.

Doum
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Re: Black Holes

Post by Doum » Mon Nov 24, 2008 6:19 pm


harry
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Re: Black Holes

Post by harry » Tue Nov 25, 2008 10:27 am

Hello Doum

oops I did not see your comment, it must be the new layout.

The link is very interesting and because of the intrinsic property it opens the debate on redshift data.

As for black holes it will alway be theoretcial and data and mechanisms disputed. Thats life.
Z-pinch is one process but not the only one.

Talking of black holes.
I came across these links: If I repeat any links,its because of reading them again.

http://arxiv.org/abs/0810.3007
Super-horizon cosmic string correlations

Authors: Arttu Rajantie
(Submitted on 16 Oct 2008)
Abstract: When gauged cosmic strings form in a symmetry-breaking phase transition, the gauge field configuration at the time becomes imprinted in the spatial string distribution by the flux trapping mechanism. It is shown that quantum and thermal gauge field fluctuations give rise to long-range superhorizon correlations in the string network. Numerical simulations in the Abelian Higgs model confirm this finding. In contrast, the Kibble-Zurek mechanism, which most cosmic string studies are based on, only gives rise to short-distance subhorizon correlations. The potential observable effects of the correlations are discussed.
and

http://arxiv.org/abs/0810.0923
Dynamics of black holes

Authors: Sean A. Hayward
(Submitted on 6 Oct 2008)
Abstract: This is a review of current theory of black-hole dynamics, concentrating on the framework in terms of trapping horizons. Summaries are given of the history, the classical theory of black holes, the defining ideas of dynamical black holes, the basic laws, conservation laws for energy and angular momentum, other physical quantities and the limit of local equilibrium. Some new material concerns how processes such as black-hole evaporation and coalescence might be described by a single trapping horizon which manifests temporally as separate horizons.


as for Z-pinch try to get a video on sun spots and the pinching of the magnetic fields it is so explosive.
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Re: Black Holes

Post by Doum » Tue Nov 25, 2008 9:30 pm

Just to remember you that those powerfull jet from black hole dont necessarly need "z pinch" to be explain.

http://www.space.com/scienceastronomy/0 ... lazar.html

Extract from the article: "It turns out that the model matches the data. We can actually see the particles gaining velocity as they are accelerated along this magnetic field."

harry
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Re: Black Holes

Post by harry » Wed Nov 26, 2008 8:15 am

G'day Doum

I agree with what you say. Z-pinch may not be the answer. But! the billions of dollars spend on experiments indicate a possible mechanism that is a property of plasma when two magnetic fields connect a jet is formed and degenerate matter and its compaction.


But! what created the jet, what triggered the motion?

I still think we have many more years of research.

Sheared Flow as a Stabilizing Mechanism in Astrophysical Jets
http://adsabs.harvard.edu/abs/2007Ap%26SS.307...83W


Plasma Jet Studies via the Flow Z-Pinch
http://adsabs.harvard.edu/abs/2007Ap%26SS.307...41S

Spectral diagnostics of transient X-ray plasmas
http://adsabs.harvard.edu/abs/2003APS..DMP.D1081O

Magnetic tower outflows from a radial wire array Z-pinch
http://adsabs.harvard.edu/abs/2005MNRAS.361...97L


Frontiers for discovery in high energy density physics
http://adsabs.harvard.edu/abs/2005APS..SHK.A1001D


If I repeat any links,,,,,,,,,,its an oops.
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Re: Black Holes

Post by Doum » Fri Nov 28, 2008 5:11 am

Hmmm i can not discard the z pinch but i cannot support it neither. I need more result from those study. And light or anything else still cant escape a black hole event horizon. May be later something new will come out. But not yet.

harry
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Re: Black Holes

Post by harry » Fri Nov 28, 2008 5:38 am

G'day doum

You said

And light or anything else still cant escape a black hole event horizon
You can study papers on arXiv and ADS on Z-pinch and also

Event Horizon has been the talking poing for some time and has stopped many scientists in their tracks.

Regardless

He is a paper of interest

http://arxiv.org/abs/0810.0536
Critical points in a relativistic bosonic gas induced by the quantum structure of spacetime

Authors: Elias Castellanos, Abel Camacho
(Submitted on 2 Oct 2008)
Abstract: It is well known that phase transitions arise if the interaction among particles embodies an attractive as well as a repulsive contribution. In this work it will be shown that the breakdown of Lorentz symmetry, characterized through a deformation in the relation dispersion, plus the bosonic statistics predict the emergence of critical points. In other words, in some quantum gravity models the structure of spacetime implies the emergence of critical points even when no interaction among the particle has been considered.
and

http://arxiv.org/abs/0809.5040
Dark Energy: A Missing Physical Ingredient

Authors: M. I. Wanas
(Submitted on 29 Sep 2008)
Abstract: Recent observation of supernovae type Ia show clearly that there is a large scale repulsive force in the Universe. Neither of the four known fundamental interactions can account for this repulsive force. Gravity is known to be the interaction responsible for the large scale structure and evolution of the Universe. The problem with gravity is that it gives rise to a force which is attractive only. Gravity theories, including General Relativity, deals with gravity as an attractive force. Although this is consistent with our experience in the solar system and other similar astrophysical systems, gravity theories fail to account for SN type Ia observation. So, we are in a real problem concerning the interpretation of these observation. This problem is only ten years old. In order to go out of this problematic situation, scientists have suggested the existence of a type of energy in the Universe that is responsible for the above mentioned repulsive force. They have given this type of energy the exotic term {\it "Dark Energy"}. Although this type of energy forms more than two thirds of the energetic contents of our Universe, its reasonable nature is missing in all gravity theories.
I think some form of Event or trapping Horizon can exist, in what form its still an unknown. Very theoretical.

Jets are jets and share similar properties.
But! their origins and strength are directly related to the density of the surrounding matter. You can get jets forming on the surface of our sun, within the solar envelope and the deeper the origin the stronger the jets. Thats is why the bipolar jets are more extreme that originate deep, near the core if not within the core.
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v13
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Re: Black Holes

Post by v13 » Mon Dec 01, 2008 9:32 pm

Hello there,

I've a question regarding black holes. It is said that light cannot escape from a black hole (by definition), but...

Suppose that a black hole is a sphere (this doesn't actually matters a lot but it helps understanding), no matter what its size is. This means that all or most of the mass of the blackhole is inside this sphere. Now, suppose that a photon leaves this sphere in a way that the sum of gravitational forces act exactly at the oposite direction of its path. This means that the photon will not 'prefer' left or right and since (almost by definition) it can't be slowed down, it will keep going. Since gravity will not curve the trajectory of this photon it should eventually reach the event horizon and escape the black hole. No matter what form spacetime will have near the blackhole, such a path should always exist (even if it isn't exactly a straight line) and a photon will always be able to follow this path.

Is there something wrong in the above reasoning?

I'm not a physicist so be gentle :)

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Re: Black Holes

Post by Doum » Tue Dec 02, 2008 3:22 am

Hello v13,

If i follow what you suppose then not only one photon will be able to escape an event horizon but many billions and billions . Why only one photon should be align to escape an event horizon. Since all black hole observe aint shining light, it show that light cant escape an event horizon. Since a black hole fold the fabric of spacetime into itself there aint any exit possible for any photon. I am no physicist neither but i answer you with what i understand on black hole. I too also welcome physicist answer wich may correct me and improve my understanding. I hope it help you.
Last edited by Doum on Tue Dec 02, 2008 6:21 pm, edited 1 time in total.

harry
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Re: Black Holes

Post by harry » Tue Dec 02, 2008 3:47 am

G'day from the land of ozzzzzzzz

The Jet vortex that is created by the degenerate matter forms a protected stream of electromagnetic waves that the extreme gravity of the Black hole does not effect it for some time.

If you can research the properties of Jet you will self discover maybe the mechanism or an understanding.



Black hole tunnelling entropy and the spectrum of gravity.
http://adsabs.harvard.edu/abs/1993CQGra..10.2479C


Black hole explosions
http://adsabs.harvard.edu/abs/1982coas.conf...83S


Some Simple Black Hole Thermodynamics
http://adsabs.harvard.edu/abs/2003PhTea..41..299L
May-03
In his recent popular book The Universe in a Nutshell, Steven Hawking gives expressions for the entropy1 and temperature (often referred to as the ``Hawking temperature''2 ) of a black hole:3 S = kc34ℏG A T = ℏc38πkGM, where A is the area of the event horizon, M is the mass, k is Boltzmann's constant, ℏ = h2π (h being Planck's constant), c is the speed of light, and G is the universal gravitational constant. These expressions can be used as starting points for some interesting approximations on the thermodynamics of a Schwarzschild black hole, of mass M, which by definition is nonrotating and spherical with an event horizon of radius R = 2GMc2.4,5
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Re: Black Holes

Post by Chris Peterson » Tue Dec 02, 2008 4:30 am

v13 wrote:Suppose that a black hole is a sphere (this doesn't actually matters a lot but it helps understanding), no matter what its size is. This means that all or most of the mass of the blackhole is inside this sphere. Now, suppose that a photon leaves this sphere in a way that the sum of gravitational forces act exactly at the oposite direction of its path. This means that the photon will not 'prefer' left or right and since (almost by definition) it can't be slowed down, it will keep going. Since gravity will not curve the trajectory of this photon it should eventually reach the event horizon and escape the black hole. No matter what form spacetime will have near the blackhole, such a path should always exist (even if it isn't exactly a straight line) and a photon will always be able to follow this path.
I'd answer this a couple of ways. The standard answer is that we don't really know the rules of physics inside a black hole. It is probably incorrect to think that a photon can't "slow down"; the interior of a black hole is so extreme in terms of the state of both space and time that we can't even define what "slow down" means. Also, keep in mind that from our reference frame, nothing ever actually falls into a black hole, it just gets closer and closer to the event horizon.

A more intuitive, but less correct answer, would be that you might never have a photon traveling directly away from the center of a black hole. Just imagining photons as billiard balls, how would anything falling into a black hole ever have a trajectory that would be perfectly opposite the gravitational force?
Chris

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Re: Black Holes

Post by Qev » Tue Dec 02, 2008 9:10 am

My understanding of a black hole is something along the lines of space-time being so distorted beyond the event horizon that the direction in space that points toward the singularity stops being a direction in space, and instead becomes a direction in time (ie. the future). So, for any photon inside the event horizon to avoid the singularity, it would have to travel in the same sort of direction that someone driving a car would need to travel in order to avoid tomorrow. :lol:
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harry
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Re: Black Holes

Post by harry » Tue Dec 02, 2008 1:01 pm

G'day from the land of ozzzzzzzz

Sounds like we are at the movies.

Black Hole Core Density
SAO/NASA Astrophysics Data System (ADS)
http://www.adsabs.harvard.edu/

Maybe a bit of research on black holes and compact matter.

Search ADS
http://www.adsabs.harvard.edu/
Degenerate matter black holes
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Re: Black Holes

Post by Doum » Thu Dec 04, 2008 2:18 am

harry wrote:G'day from the land of ozzzzzzzz

The Jet vortex that is created by the degenerate matter forms a protected stream of electromagnetic waves that the extreme gravity of the Black hole does not effect it for some time.
If you can research the properties of Jet you will self discover maybe the mechanism or an understanding.
Black hole tunnelling entropy and the spectrum of gravity.
http://adsabs.harvard.edu/abs/1993CQGra..10.2479C
Black hole explosions
http://adsabs.harvard.edu/abs/1982coas.conf...83S
Some Simple Black Hole Thermodynamics
http://adsabs.harvard.edu/abs/2003PhTea..41..299L
May-03
Harry none of those link are related to "The Jet vortex that is created by the degenerate matter forms a protected stream of electromagnetic waves that the extreme gravity of the Black hole does not effect it for some time." that you talk about.

Its about hawkins degeneration of a black hole wich will take infinity to reach.
So why putting it there?
I have the book here and it does say that it took infinity for a black hole to degenerate. No explosion or jet. ????

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Re: Black Holes

Post by harry » Fri Dec 05, 2008 7:39 am

G'day Doum

Mate if you are interested in understanding black holes, you need to read about their properties.

As for the properties of Jets

Mate you can get that from google.

Papers on plasma jets

http://arxiv.org/find/all/1/all:+AND+20 ... /0/all/0/1

Mechanism for astrophysical jets arXiv
http://arxiv.org/find/all/1/all:+AND+je ... /0/all/0/1


If I have repeated these links,,,,,,,,,I'm sorry
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Re: Black Holes

Post by harry » Sat Dec 20, 2008 8:14 am

G'day

These links are interesting, although they are BBT related.

http://arxiv.org/abs/gr-qc/0309044
Holeum,enigmas of cosmology and gravitational waves

Authors: L.K.Chavda, Abhijit L.Chavda
(Submitted on 8 Sep 2003 (v1), last revised 24 Jun 2004 (this version, v3))
Abstract: The principle of nuclear democracy is invoked to prove the formation of stable quantized gravitational bound states of primordial black holes called Holeums. The latter come in four varieties: ordinary Holeums H, Black Holeums BH, Hyper Holeums HH and the massless Lux Holeums LH.These Holeums are invisible because the gravitational radiation emitted by their quantum transitions is undetectable now. The copiously produced Holeums form an important component of the dark matter and the Lux Holeums an important component of the dark energy in the universe. A segregation property puts the Holeums mainly in the galactic haloes (GH) and the domain walls (DW) explaining the latters' invisibility now. Cosmic rays (CR) are produced by two exploding black holes created in a pressure-ionization of a stable Holeum. Our prediction that more CRs will be emitted by the haloes than by the discs of galaxies already has a strong empirical support. The concentration of the Hs and the HHs in the GHs and the DWs lead to the formation of Holeum-stars emitting the CRs and the gravitational waves(GW).Innumerable explosions of BHs at the time of decoupling of gravity from the other interactions lead to inflation and baryon asymmetry. A substantial cosmic back ground of matter and GWs and an infra-quantum gravity (infra-QG) band and an ultra-QG band of GWs and their emission frequencies are predicted. A unique quantum system containing matter-energy oscillations is found.

and

http://arxiv.org/abs/gr-qc/0308054
Dark matter and stable bound states of primordial black holes

Authors: L.K.Chavda, Abhijit L.Chavda
(Submitted on 17 Aug 2003)
Abstract: We present three reasons for the formation of gravitational bound states of primordial black holes,called holeums,in the early universe.Using Newtonian gravity and nonrelativistic quantum mechanics we find a purely quantum mechanical mass-dependant exclusion property for the nonoverlap of the constituent black holes in a holeum.This ensures that the holeum occupies space just like ordinary matter.A holeum emits only gravitational radiation whose spectrum is an exact analogue of that of a hydrogen atom. A part of this spectrum lies in the region accessible to the detectors being built.The holeums would form haloes around the galaxies and would be an important component of the dark matter in the universe today.They may also be the constituents of the invisible domain walls in the universe.
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Re: Black Holes

Post by jesusfreak16 » Sat Dec 20, 2008 2:38 pm

I'm going to go a little different direction from where this topic is going (just consider it a small detour :wink:). I just wanted to ask that if light can be pulled in by a black hole,does that suggest that light is matter (if it can be pulled in at all)?

I'm not trying to change the direction of the thread, I just didn't want to start a whole new thread for one of my amateur questions (as before,just consider it a small detour).
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Re: Black Holes

Post by Chris Peterson » Sat Dec 20, 2008 3:09 pm

jesusfreak16 wrote:I just wanted to ask that if light can be pulled in by a black hole,does that suggest that light is matter (if it can be pulled in at all)?
The particle carrier of light (and electromagnetic radiation in general) is the photon. As a massless particle, it does not meet any common definition of "matter".

It is important to recognize, however, that "matter" is somewhat arbitrarily defined. There is really only one thing: energy. What we call matter is simply a form of energy, and at the level of elementary particles there may be some confusion distinguishing these states. The most commonly accepted scientific definition of matter is something made up of fermions. Basically, that means neutrons and protons (and anything else made up of quarks), and electrons. And for the most part, it means particles which have mass, although there are some exceptions (any particle of matter has mass, but there are a few non-matter particles that also have mass; all massless particles are left out of the "matter" category).
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Re: Black Holes

Post by bystander » Sat Dec 20, 2008 4:53 pm

Chris Peterson wrote:The particle carrier of light (and electromagnetic radiation in general) is the photon. As a massless particle, it does not meet any common definition of "matter".
I realize that it's commonly accepted that photons have no mass, but if that's the case, how can light be affected by gravity? How do "light sails" work? I think I remember seeing somewhere (Nova maybe?) something about research into the mass properties of light. Although the mass couldn't be measured directly, some of the experimental results could only be explained if the photons had mass.

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Re: Black Holes

Post by apodman » Sat Dec 20, 2008 4:59 pm

Chris Peterson wrote:... any particle of matter has mass ... all massless particles are left out of the "matter" category
I'm unclear where the neutrino fits. Does the standard model still say it is massless? Do some current views say it has a small mass? Is it not a constituent of matter, and therefore matter? What non-matter particles are there besides photons? Does matter have non-matter constituents?

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Re: Black Holes

Post by bystander » Sat Dec 20, 2008 5:18 pm

apodman wrote:I'm unclear where the neutrino fits. Does the standard model still say it is massless? Do some current views say it has a small mass? Is it not a constituent of matter, and therefore matter? What non-matter particles are there besides photons? Does matter have non-matter constituents?
After reading apodman's post, I think what I remember seeing was a Nova program on the Japanese research on neutinos, not photons. :oops:

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Re: Black Holes

Post by Chris Peterson » Sat Dec 20, 2008 5:19 pm

bystander wrote:I realize that it's commonly accepted that photons have no mass, but if that's the case, how can light be affected by gravity? How do "light sails" work? I think I remember seeing somewhere (Nova maybe?) something about research into the mass properties of light. Although the mass couldn't be measured directly, some of the experimental results could only be explained if the photons had mass.
Saying light is affected by gravity is really the wrong way of expressing things, since it leads to confusion. Under GR, it would be better to say that mass affects the curvature of space, producing the effect we call gravity. It is the curvature of space that affects the path of a photon, and that does not require that the photon have mass.

Strictly speaking, you can say that a photon in motion behaves as if it has a finite mass. That allows for a classical approximation of the behavior of light in a gravitational field. The rest mass of a photon is zero (even though a photon is never actually at rest); any particle with a rest mass of zero falls outside the definition of "matter".

Light sails depend on radiation pressure, which exists because photons have momentum. Conservation of momentum requires a transfer of momentum when light is absorbed or reflected. Massless particles do have momentum.
Chris

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Chris Peterson
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Re: Black Holes

Post by Chris Peterson » Sat Dec 20, 2008 5:26 pm

apodman wrote:
Chris Peterson wrote:... any particle of matter has mass ... all massless particles are left out of the "matter" category
I'm unclear where the neutrino fits. Does the standard model still say it is massless? Do some current views say it has a small mass? Is it not a constituent of matter, and therefore matter? What non-matter particles are there besides photons? Does matter have non-matter constituents?
Neutrinos are not massless. They are fermions (specifically, leptons), and as such, are considered to be "matter".

There are some bosons that have mass, but are not made of fermions and are therefore not considered to be matter.
Chris

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