Question about Black Holes and Light

[Tac-Tics]

It is said that Black Holes are regions of space so massive that even light cannot escape their intense gravitational fields.

It is also said that light propagates at a constant speed of C through a vacuum from all frames of reference.

Considering light as a photon with a velocity represented by a 3 dimentional normalized vector, consider the scenario that light moves past a black hole.

Since light always moves at a speed C, it cannot be slown down, only its direction can be changed. However, if light were to somehow be emitted from near the center of a black hole in a direction pointing perfectly the opposite direction the gravitational field would pull it, wouldn't the photon escape the black hole?

It is moving exactly the direction away from the direction it is being pulled. Thus, it is being pulled by only parallel forces. Since no perpendicular forces are applied to it, it cannot turn to the left or right. And, since its speed is constant, it can't be made to come to rest or be pulled backwards towards the black hole's center.

If this was so, wouldn't it be possible to see black holes, albiet very faintly, from certain angles?

[timeshifter]

A very good question indeed. And although I do not know the answer, I will bring up another point of remote interest to this topic.

I was always led to believe that, a black hole was, in essence, an area of space, but not just an area, but a very dense mass. Even more dense than a neutron star. This would explain the immense gravitational fields produced by these black holes, but I still do not understand.

I have read theories on black holes, and they all illustrate a black hole as being a vector in space. That I understand. What I fail to see is how this "vector" can produce such gravitational force. Is there an immense gravitational force at the tip of this vector? Or is it just a gateway to another dimension that sucks everything into it?

[budcamp]

Inside a black hole there are no photons, so one can't be traveling at the speed of light, or at any other speed. No photons no problem!

[budcamp]

Black Holes are hard to concive of. My own personal way to view them is as black spheres. A hole only has one way in. A black hole faces in all directions at once. A sphere!

You can't sneak up on it from the rear or the sides. It has eyes in the back of its head.

Bud Camp

[adren77]

Let me try to explain how it works. Thinking that a photon (a single particle of light) traveling away from black hole is attracted to black hole and sudnely sucked in like another object is not the best way to think about it because it would mean that a photon would have to slow down to 0, then accelerate again towards the black hole. We know the speed of light is constant, so...

Einstein said that closer an object at rest is to a gravitational field, the more time dialates. An example for this is, if I am floating in mid air above earth, the closer I get to the Earth, more time slows down for me. We don't notice this because Earth isn't very massive compare to some other objects, so it has a less gravity. Mass of black hole is enormous, so there is alot more gravity than on earth. Closer an object is to the black hole, more time dialates. Closer the light travels to a black hole, the time dialates more (slows down). If time slows down, but the speed of light stays the same, then its frequency must decrease, and its wavelenght must increase. If light travels so close to this very massive object (black hole) that time dialation increases to the point where it almost stops, then wavelenght would increase to infinity, and frequency would almost be infinitely small. If frequency is shifted to 0 then, there really is no light, which what makes black holes black in the first place.

I tryed to put this in the lamest terms, hope it's a little bit more clear now.

[budcamp]

adren

A much more lucid explanation than mine. But they both come down to the fact that photons do not work in black holes.

budcamp

[Tac-Tics]

Ah, I see. Thank you very much for your explanation.

[timeshifter]

So, we have established that photons do not work in a black hole. Why?

What force is keeping all photons out of a black hole? Would it be the immense gravity I talked about earlier or just some natural phenomenon we can not as of yet explain?

[budcamp]

Photons are emitted when electrons in an atom shift from one level to another. They emit a photon and a neutrino. Because of the immense gravity in black holes, there is no distance between electrons and the nucleus of the atom. They are pushed togather into one unit. No space for the electrons to move.

[budcamp]

Nothing Escapes a black hole? What about nutrinos. Does anyone know if they pass through black holes or not? They pass through everything else!

Another interesting point that I can't reason out myself: If an atom is just sucked into a black hole, and has not colapsed yet, can one of it's electrons make a quantum shift and escape. No ammount of gravity can affect the leap, since it is not passing through space when it leaps. It seems it should be able to jump right out of a black hole. I'm probaly missing something, but I don't know what.

Any answers?

[adren77]

If an atom is sucked inside a black hole, and it somehow recieves enough energy to quantum shift an electron into an outer orbit, the electron will still be trapped inside the black hole. Why? Because the space inside the black hole is streched out. When observed from the outside, a black hole might appear 1km in diameter, so you would think that if you entered it you would only have to travel 1/2 km befor reaching the center. However, the space inside a black hole is distorted so much that the actualy distance from the horizon to the singularity is much greater than observed from the outside.

At least this is what I think.

Nutrinos will be sucked and trapped inside a black hole just like anything else.

[PhysBrain]

Since I just finished reading something about this in "Indistinguishable from Magic" by Robert Forward, I'll attempt to paraphrase what he had to say about neutrinos.

No one is quite sure what kind of particles neutrinos really are. They cannot be directly observed. Their presence can only be inferred because of a failure in book-keeping of conserved quantities (like charge, spin, and momentum) in all of the other observable particles in a given reaction. Currently accepted theories assume the mass of the neutrino is zero, and that it acts similar to a photon in how it transports momentum and energy, but in addition, it also has spin. Some experiments which have tried to determine the mass of the neutrino have come up with a negitive number for its mass squared (the quantity which could be inferred from the experiment) which would suggest that the neutrino has an imaginary rest mass. If this is true, then it may be possible that neutrinos are actually tachyons (tachyons are particles which can only travel faster than light, luxons (ie. photons) can only travel at the speed of light, and bradyons (ie. normal matter) can only travel at less than the speed of light).

Since the event horizon of a black hole is defined as the location in the gravity well of a massive object where the escape velocity becomes greater than the speed of light, then it may be possible that neutrinos could still pass through the event horizon. Although, I am unsure how the gravity well would affect the motion of the particle since it would not be possible to slow it to the speed of light.

Anyway, this is my interpretation of Dr. Forward's discussion of neutrinos. I hope I got at least somewhat close to what might be considered the truth.

[budcamp]

How can it suck in neutrinos? They have no mass, so can not be affected by gravity. They even pass through neutron stars.

The event horizon of a black hole is the point at which there is no return. Half the diameter of the atom is enough to grab it. That leaves the atom close enough to the horizon that an electron should be able to jump. No?

[Jovian03]

Seems to be some confusion as to gravity's domain. From the Newtonian standpoint, only particles with mass can be subject to a gravitational force. From the Einsteinian standpoint (General Relativity), however, gravity is the warping of spacetime due to the presence of a massive object. This gravitational force, as we experience it, is the three-dimensional projection of a four-dimensional (spatial dimensions) phenomenon. Impossible to visualize, but pretty cool. Anyway, all of spacetime (and everything it contains) is affected. So, even photons and neutrinos are at the mercy of gravity.
NOTHING can pass through a black hole and emerge on the other side. The event horizon is effectively a boundary between OUR spacetime (everything we can observe) and THEIR spacetime (whatever freaky things go on near the black hole's singularity, assuming it exists - but that's another discussion altogether). No information can pass from within the event horizon to without it, as the escape velocity at the event horizon is equal to the velocity of light. This includes particles.
Black holes, however, CAN be seen. Vacuums aren't empty, as we've all been led to believe. Heisenberg's Uncertainty Principle has all sorts of weird implications. Among them is the fact that empty space is crawling with "virtual" particles - particle-antiparticle pairs that instantly annihilate, releasing their energy in the form of photons. The energy used to create these virtual particles is "borrowed" from the vacuum. When they annihilate, the energy is "returned." Near the surface of a black hole, however, there are massive tidal forces (differences in the strength of gravity). If the tidal forces are sufficiently powerful to overcome the attraction between the virtual particle pairs, then one particle may be sucked into the black hole, while the other roams free. Their mass-energy had to have come from somewhere (it hasn't been returned to the vacuum). It turns out that the black hole is the source. This radiation is called Hawking Radiation, after the great Stephen Hawking. It's pretty faint, though (the power of Hawking Radiation is in the octillionth-of-a-watt range).
Sorry, that was pretty long-winded. Hope I cleared up more confusion than I created.

[Grant Nockolds]

Hi guys, I'm a virgin replier and as yet no threads to speak of either, however i think i may have something useful to add both on the black hole and light sides.

My understanding of black holes is that they rotate; are sperical (but by no means perfectly so), and are extremely massive - the largest individual masses known in the universe.

This combination of; an extremely dense object, that is roughly sperical and is rotating at tremendous velocities will create massive variances of gravitational force vectors emitted from the hole and a whirlpool of directions for them to be applied.

Also, anything spinning must have an axis. Even if a black hole axis wobbles it will still have an astronomically smaller velocity around the poles compared to the particles sitting on its equator and thus super massive variances in the black holes gravitational pull is to be expected.

The jet streams of high energy photons and antiparticles that are emitted (or did they escape?) from black holes is a perfect example of the "Axis of a black hole" or "place of least resistance" that will exist with any rotating object.

The second part concerns lights - Wave Particle Duality. This duality shows that light also behaves like a particle of mass. If light/photons behave as if they have mass is it any suprise that a black holes gravitation can stop or at least diffuse lights quanta.

[Grant Nockolds]

Hi guys, I'm a virgin replier and as yet no threads to speak of either, however i think i may have something useful to add both on the black hole and light sides.

My understanding of black holes is that they rotate; are sperical (but by no means perfectly so), and are extremely massive - the largest individual masses known in the universe.

This combination of; an extremely dense object, that is roughly sperical and is rotating at tremendous velocities will create massive variances of gravitational force vectors emitted from the hole and a whirlpool of directions for them to be applied.

Also, anything spinning must have an axis. Even if a black hole axis wobbles it will still have an astronomically smaller velocity around the poles compared to the particles sitting on its equator and thus super massive variances in the black holes gravitational pull is to be expected.

The jet streams of high energy photons and antiparticles that are emitted (or did they escape?) from black holes is a perfect example of the "Axis of a black hole" or "place of least resistance" that will exist with any rotating object.

The second part concerns lights - Wave Particle Duality. This duality shows that light also behaves like a particle of mass. If light/photons behave as if they have mass is it any suprise that a black holes gravitation can stop or at least diffuse lights quanta.

[PhysBrain]

According to Hawking's theory, the power radiated by a black hole is actually inversely proportional to its mass. In other words, the smaller the black hole, the hotter it radiates. This has been proposed to be at least part of the reason why we don't observe small black holes that are below a certain mass that might have been formed in the earlier, hotter universe: they simply evaporate too quickly. Given that radiated energy is produced at the expense of disappearing mass (E=mc^2), then the more energy they loose to radiation, the less mass they have, the faster they radiate. This is an exponentially increaseing trend in mass loss due to radiation.

Just to make a clarification, photons do not have mass, but they do possess momentum and energy. So another overly simplistic way of thinking about light inside of black holes is to imagine that a photon must have sufficient momentum as it is leaving the surface of a black hole to overcome the gravitational attraction. This view may help shed some light on the inverse relationship between mass and radiation power mentioned above. In a less massive black hole, the cut-off limit for the minimum energy/momentum a photon must possess in order to escape is somewhat low. However, in a much more massive black hole, this cut-off limit whould be much higher. So, as one can see, from an energetics standpoint, the amount of radiation that can leave an small black hole is greater than that which can leave a larger black hole. The main question left unanswered then is: What is the energy/momentum/frequency spectrum of internal radiation of a black hole, and to what degree is the spectrum dependent upon the mass, charge, and spin characteristics of the matter in the singularity?

[rocker]

The Pauli Exclusion principle. This diverts light particles away from each other since a particle cannot be too close near another particle unless under extremes such as plasma, where the protons have been stripped from their electrons.
Black Holes can be perfectly smooth and nonrotating, which is a rarity, but again the Pauli Exclusion principle diverts all light rays to the side thus bending space time so great that the only way forward is back.

[tcampione]

Black Holes are hard to concive of. My own personal way to view them is as black spheres. A hole only has one way in. A black hole faces in all directions at once. A sphere!
Extremely interesting perception. Is there some indication that matter is pulled from multiple planes? I'm not questioning the validity, I really don't know.

[raptor]

I hear that due to some quantum phenomena that i'd rather not go into, particles and anti-particles spontaneously appear in space and annihilate all the time. as energy cant just be created, one particle has negative energy. in the presence of a black hole however, the particles dont always annihilate-some of the -ve energy particles fall past the event horison.

the -ve particles gradually decrease the mass of the black hole, while their partners fly away into space.

This creates the illusion of the black hole slowly radiating particles into space from above the event horison until it radiates the last of its energy in a massive explosion.

[PhysBrain]

The Pauli Exclusion principle. This diverts light particles away from each other since a particle cannot be too close near another particle unless under extremes such as plasma, where the protons have been stripped from their electrons.
Black Holes can be perfectly smooth and nonrotating, which is a rarity, but again the Pauli Exclusion principle diverts all light rays to the side thus bending space time so great that the only way forward is back.

The Pauli exclusion principle only applies to massive particles. At least I've never heard of it being applied to photons or electromagnetic radiation. Photons in close proximity are only subject to the superposition principle (i.e. the amplitudes of the EM fields just add up). So, the exclusion principle applies to the particles composing the singularity (if individual particles still exist there), but not to the photons since they will quite happily overlap via the superposition principle.

As far as plasmas go, the exclusion principle still applies. Even though the electrons are stripped from their atoms, they are still prevented from occupying the same space at the same time in the same spin state.

[Yazoo]

It order to understand a black hole, we need to first understand gravity. Gravity is always described as an attractive force that pulls on matter, photons, etc. That's one way to describe how matter behaves in the presence of gravity, but something more important is the relationship between gravity and space-time. Gravity is the pulling or stretching of space-time itself. I'm not sure it's correct to say light cannot escape the pull of gravity in a black hole, but rather space-time is being pulled in at a rate faster than the photon can move, therefore the photon will never reach us. So a black hole is not just a great concentration mass, it is also a space-time vacuum cleaner. Does all that space-time still exist in the black hole, or does it get destroyed, or does it just disappear? Can gravity be measured as the density of space-time? Does space-time exist at different densities in a black hole? How does matter behave at different space-time densities?

[neil]

My guess is adren gave the main stream explanation. Photons may be destroyed near the event horizon of one solar mass black holes, but billion solar mass black holes are quite gentle near the event horizon, so you would not notice anything (except a gradually rising radiation hazzard) as the spacecraft you were in crossed the event horizon. The photons from your flashlight would behave much like they did when your spacecraft was back home. While your fuel remained you could fly in and out of the event horizon repeatedly as long as you stayed reasonably close to the event horizon. If you traveled far toward the center of the event horizon sphere, your craft and flashlight would be destroyed by the gravity gradient, but up to that point the photons from your flashlight (inside your craft) would not behave strangely IMHO. Neil