Assuming all is as has been stated and that is that a Black Holes gravity is so strong that it pulls back light and it cannot escape.

Do we really visualize light remains constant and then just stops or must it be gradually slowed under the stress of the tow of gravity?

Should that be the case does not that mean that the velocity of light is variable throughout the universe?. That is to say in deep space it would be v = c but in a dense gallaxy it would be c+/- depending on the gravity field alignment to the velocity of light.

It follows if one accepts that light bends in a gravity field that it will accelerate of decelerate as well under such influence.

Any thoughts or known answers?

I've read just a bit. General Relativity predicts that light slows down in a field of gravity proportionally to the field's strength. I'll stay away from black holes but I've read that, optically speaking, you can think of a strong field of gravity as though it was a lens, bending light. Hope this helps.:)

The spacetime inside the event horizon of a black hole is extremely curved. Light still travels at the normal speed - it is not slowed or "pulled back" by the hole. It is just that no light paths lead out of the hole.

Natural,

Thanks for your reply. What you say is true and I knew that view my point in referring to the Black Hole was to make light stop so as to emphasize gravity's affect on light to broach the issue of the constant velocity of light.

Gravity must affect it it seems to me which should introduce some variation in light speed in different regions of the universe.

You don't have a homogeneous distribution of matter hence nor gravity.

Voids
Gallaxies

Gallaxy Clusters, etc., How much does that enfluence physics and Relativity.

My suspecion is that it merely shifts Relativity to the new velocity of c. But that is the question I had in mind.

James R.,

I'll accept that in that I have no arguement against it at the moment. But it does seem strange. That is that light doesn't get out because of curved space. Space may curve but one can travel in any vector, it is not like a slot car track. Assuming that it seems that statistically some light would find a vector leading away from the gravity field. I have always seen the event horizon referred to in terms of gravity intensity but not as a closed dimensional field due to gravity.

I have also seen two different explanations for light parallax. I have seen it said that light is following curved space and I have seen it said that the light ray is being bent by gravity.

Is there a prefered view of that?

If it is bent by gravity then I think the question still stands as to the unifomity of light speed throughout the univers due to gravity enfluences.

To add to James R’s comment, the trick to grasping black holes and light is to realize that light can travel at its normal speed, yet remain in one spot. It depends on what you relate light’s motion to. Picture a boat in a river that is stationary relative to the shore. Is the boat traveling? Yes, relative to the water. Likewise, light radiating directly outward may stay precisely at a black hole’s event horizon (http://www.eclipse.net/~cmmiller/BH/blkbh.html), yet it moves at its normal speed relative to material objects crossing the event horizon from those perspective of those objects. This is why some sites/books say that the event horizon moves outward at c, the speed of light. The objects crossing the event horizon are analogous to objects freely floating with the river, past the boat and shore.

Originally posted by MacM
I have also seen two different explanations for light parallax. I have seen it said that light is following curved space and I have seen it said that the light ray is being bent by gravity. Is there a prefered view of that?

I’m not a scientist, but these viewpoints seem compatible to me. Light follows curved space, and so appears to bend; the light goes straight through space that is curved. Or light does bend, giving the appearance of curved space. Either viewpoint is fine as long as they make the same accurate predictions. Likewise, at the event horizon, light radiating directly outward moves at c but goes nowhere relative to the singularity or distant objects because it’s moving against space flowing inwards at c. Curved space and flowing space are also compatible concepts to me. Actually the latter is better for understanding methinks. Picture a Moon held in its orbit because as it moves tangentially to its orbit against space flowing towards the Earth, it ever falls from the tangent and into the arc of a circle, like how a boat aiming perpendicular to a river’s shore moves in an arc relative to the shore.

If it is bent by gravity then I think the question still stands as to the unifomity of light speed throughout the univers due to gravity enfluences.

As described above, light can be the same speed as directly measured by anyone, yet appear to move slower or even stop from a different perspective.

Assuming that it seems that statistically some light would find a vector leading away from the gravity field.

The light doesn’t escape beyond the event horizon because at the horizon space flows inward at c, and within the horizon at > c. Light can’t beat that. So there is no escape vector, and the odds are zero.

zanket,

Your description makes some sense. But it also generates a view of time-space (aether) flowing inward in that light isn't being propagated by material flowing inward.

The difference in viewing light following curved space and curving under the enfluence of gravity is that of mass. It loses me just a bit in that the normal reference to the parallaxing of light refers to light having mass but then they turn around and say that space is curved.

If space is curved no mass would be required. The curve in UniKEF is physically a straight line. That is a path of least resistance. Any motion not in such a path becomes acceleration with those associated forces and consequences.

There are a couple of other interpretations, too. Maybe space stretches to infinite length at the event horizon, and light continues travelling at c but never gets to the horizon. Or - I don't like this explanation - the wavelength approaches infinity and the frequency approaches zero, in effect the black hole absorbs all the energy of the photons and they cease to exist.

Guys it is a matter of excape velocity.
If you fire a cannon ball into orbit it must exceed the excape velocity of the gravity well it is in.
The excape velocity for a black hole is simply > c, so light simply falls back to the hole in a nice parabolic path.
Nothing strange here.

Synergy,

I don't like this explanation - the wavelength approaches infinity and the frequency approaches zero, in effect the black hole absorbs all the energy of the photons and they cease to exist.

This is a good description of what I envisioned.


hlreed,


Your description actually fits well with the synergy post above.

Light always follows geodesic curves in spacetime. Inside a black hole, all geodesics remain inside the black hole. Light doesn't get to choose its path.

A material body may choose its path, by using fuel to accelerate itself. However, to escape the black hole event horizon would require that the spacecraft follow a space-like interval (move faster than light) which isn't allowed.

The statement "inside a black hole, all geodesics remain inside the hole" is therefore not strong enough. It is better said "inside a black hole, all worldlines remain inside the hole."

No matter what you do, there are no time-like or null (allowable) worldlines from any point inside the black hole to any point outside.

- Warren

chroot,

I again accept that view; which sugggest tightly curved space.

But I also consider it one of several possibilities, not necessarily the correct one but I have no evidence that any of the concepts offered are the correct one.

Originally posted by MacM
But I also consider it one of several possibilities, not necessarily the correct one but I have no evidence that any of the concepts offered are the correct one.
Who cares?

- Warren

Is it possible, mathemetically, for a perfect black hole (following the math perfectly) to have a photon in orbit? It would seem to me that there would be some distance from the center of the black hole (even horizon?) where the photon would follow a perfect circular orbit. Is this possible? If it is...would the photon simple orbit forever (given a perfect model)?

-AntonK

AntonK,

Your post reminded me of this article. It has nothing to do with Black Holes but the circular orbiting of photons.


Microtoroids Store Light Energy on a Silicon Chip




SEM micrograph of a toroid-shaped silica microcavity. The quality factor of this toroid was measured to be 1.00x108. Image courtesy: Prof. Vahala, Caltech.
In an advance that holds promise for integrating previously disparate functions on a chip, applied physicists at the California Institute of Technology have created a disk smaller than the diameter of a human hair that can store light energy at extremely high efficiency. The disk, called a "microtoroid" because of its doughnut shape, can be integrated into microchips for a number of potential applications.
Reporting in the February 27, 2003, issue of the journal Nature, the Caltech team describes the optical resonator, which has a "Q factor," or quality factor, more than 10,000 times better than any previous chip-based device of similar function. Q is a figure-of-merit used to characterize resonators, approximately the number of oscillations of light within the storage time of the device.

The devices store optical energy by resonant recirculation at the exterior boundary of the toroid and achieve Q factors in excess of 100 million. In general, resonators whether mechanical, electronic, or optical have many applications. TV tuners and quartz crystals in a wristwatch are examples of resonators at radio frequencies; at optical frequencies, resonators are used in filters, sensors, and quantum optics.

Attaining ultrahigh-Q and fabricating the resonators on a chip have so far been mutually exclusive. Only rather exotic structures, like droplets or microspheres, have exhibited the atomically smooth surfaces needed for ultrahigh-Q. Due to a novel fabrication step, it is now possible to achieve both high Q and atomically smooth surfaces at the same time and to bring two worlds together.

The fabrication procedure uses lithography and etching techniques on a silicon wafer in a manner similar to process steps used for making microprocessors and memories. Thus, the resonators can be integrated with the circuitry of a chip, with lab-on-a-chip functions, or even with other optical components. Wafer-scale processing methods also enable their production in large quantities, an important feature in many applications, like biosensing, where low-cost, field deployable sensors are envisioned.

The microtoroids were fabricated in the lab of Kerry Vahala, who is Jenkins Professor of Information Science and Technology and professor of applied physics at Caltech. Vahala is co-inventor of the device, along with his graduate students Deniz Armani, Tobias Kippenberg, and Sean Spillane.

"This is the first time an optically resonant device with an ultrahigh-Q has been fabricated on a chip," says Vahala.

Vahala says his group is exploring ways to further increase the Q value of these devices as well as to further reduce their size. He believes Q values in excess of 1 billion in even more compact toroids will soon be possible. Last year, in the February 7, 2002, issue of Nature, the Vahala group reported an efficient nonlinear wavelength source using ultrahigh-Q resonators. His group is now investigating microchip-toroid versions of these nonlinear sources that may one day be used in communications systems.

The work was supported by Caltech's Lee Center for Advanced Networking and DARPA.

Click here for more information on the Vahala group.



News Story Origin: Caltech
Click here for the original news release.

Originally posted by AntonK
Is it possible, mathemetically, for a perfect black hole (following the math perfectly) to have a photon in orbit? It would seem to me that there would be some distance from the center of the black hole (even horizon?) where the photon would follow a perfect circular orbit. Is this possible? If it is...would the photon simple orbit forever (given a perfect model)?

-AntonK

yes, this is possible. any photon traveling along the horizon will remain in circular orbit at the horizon.

It is often said that if you were to stand right at the event horizon, you could see the back of your own head.

- Warren

chroot,

I have heard the exact same stated for relativity and curved space in the Universe.

What is your position on that issue?

If you go far enough in a given vector will you return to your origin? Or see the back of your head if you look far enough?

Wow...seems then that would be an extremely powerful laser (though not really a laser since the narrow beam of photons wouldn't be coherent). If the blackhole were suddenly and magically (since this can't really happen) shut off then an intense burst of light should radiate out. Interesting...

Anyone have any idea how much energy could actually orbit a blackhole? Is there anything about a realworld blackhole that prevents large amounts of energy from doing this? If not, seems like the perfect storage.

-AntonK

Originally posted by AntonK
Anyone have any idea how much energy could actually orbit a blackhole? Is there anything about a realworld blackhole that prevents large amounts of energy from doing this? If not, seems like the perfect storage.
Photons are bosons, and as such there is no limit to how many you can cram into one place.

However, the orbit is unstable, so I don't think it's the perfect storage... plus all of the ah, engineering challenges.

- Warren

Originally posted by MacM
Your description makes some sense. But it also generates a view of time-space (aether) flowing inward in that light isn't being propagated by material flowing inward.

Light would still be propagated by material flowing inward. I’m not sure what you mean here.

The difference in viewing light following curved space and curving under the enfluence of gravity is that of mass. It loses me just a bit in that the normal reference to the parallaxing of light refers to light having mass but then they turn around and say that space is curved.

I see it like this: light has mass when it’s moving (which it always is), and so, like other mass, it naturally moves in a straight line within the curved (or flowing) space.

Originally posted by hlreed
The excape velocity for a black hole is simply > c, so light simply falls back to the hole in a nice parabolic path.
Nothing strange here.

There is one situation where the light may not fall back. As a star collapses to punch through its event horizon (that is, where the circumference of the horizon and star are equal), photons emitted directly outwards from the star at that moment remain forever at the horizon, in principle of course. It’s easier for me to visualize this happening as a result of flowing space rather than curved space. The photons move at c against space flowing inwards at c.

And light that is subsequently emitted directly outwards, below the event horizon but before the star becomes a singularity, moves inwards not outwards. No sooner is the photon emitted than it moves towards the center. The surface falls away from the photon at c initially.

Originally posted by synergy
There are a couple of other interpretations, too. Maybe space stretches to infinite length at the event horizon, and light continues travelling at c but never gets to the horizon.

I think this is a valid interpretation except that the space stretches to infinite length (rate of stretch = infinite) at the singularity at the center. It stretches at a rate of c across the horizon.

Or - I don't like this explanation - the wavelength approaches infinity and the frequency approaches zero, in effect the black hole absorbs all the energy of the photons and they cease to exist.

Yeah I haven’t liked that explanation either. It may be valid but it’s sure easier to visualize stretching or flowing space.

zanket,

There seem to be several plausible concepts for what physically is taking place.


quote:
--------------------------------------------------------------------------------
Originally posted by MacM
Your description makes some sense. But it also generates a view of time-space (aether) flowing inward in that light isn't being propagated by material flowing inward.
--------------------------------------------------------------------------------


Light would still be propagated by material flowing inward. I’m not sure what you mean here.

*********************

That response was in regard to a suggestion that material was flowing into the Black Hole. The link to light wasn't made clear.

The propagation of light is independant of such mass flow. It propagates differently. My view is along the lines of light energy (mass) being drawn in much as the view of other mass or material being drawn in. That suggests to me that either the velocity is restrained then brought to "0" such that the energy is drained (tired light syndrome) to where there is nolonger any photon mass. It effectively gets absorbed.

But there seems to be an alternative view that the light merely remains light and enters a closed loop and circulates via curved space around the Black Hole.

It seems in that case that other material would necessiarily also
follow a curved horizon. That doesn't make as much sense to me.

I don’t follow everything you said but let me expand on my metaphor, which to me makes black holes simple, so that there is no tired light or absorption or loss of photon mass. I’ll cover just the highlights.

Imagine a river called Space. The river Space accelerates past an imaginary line across the river called the Event Horizon. At this line the speed of Space relative to the shore is 20 knots, a speed we’ll call c. Upstream from the Event Horizon, Space moves at < c, and downstream from the Event Horizon at > c.

A ship is anchored upstream of Event Horizon. This ship can fire a Photon torpedo in any direction. A unique property of the Photon is that anyone who directly measures its speed always finds it is c. Let the ship’s crew fire a Photon upstream. Naturally the crew measures the Photon depart the ship at c. But an observer on the shore, who we’ll call a bystander, measures the Photon moving upstream at < c, for the river’s flow is canceling some of the Photon’s speed, and the bystander is not directly measuring the Photon’s speed, so nothing enforces that the speed be c.

Now if the crew measures the Photon moving faster than the bystander measures, then the ship’s clock must be running slow relative to the bystander’s clock. Say the bystander measures the Photon leave the ship at 0.5c, or 50% of c. Then the Photon’s speed is 10 knots. If the ship’s clock is running at the same discount, 50% of the bystander’s clock, then for every hour that elapses on the bystander’s clock, half an hour elapses on the ship’s clock. Then the crew measures the Photon depart at 10 nautical miles per half hour, which is 20 knots, which is c, as expected.

Let the ship raise anchor and freely float in Space towards the Event Horizon. At the moment the ship reaches the Event Horizon, the crew fires a Photon directly upstream. Naturally the crew measures the Photon depart the ship at c. But the Photon stays at the Event Horizon, because it moves upstream at c while Space moves downstream at c to exactly cancel the Photon’s movement. Meanwhile the ship moves downstream from the Event Horizon initially at c. What does the bystander measure? Nothing! From the bystander’s perspective the ship’s clock would slow as the ship approached the Event Horizon, and stop altogether as the ship crossed it, for the reasoning given above.

But the bystander will never note such a clock stoppage, because of some information I kept back until now, which is that the bystander can make measurements about the ship only by receiving data about the ship by Photon. The Photon is not a torpedo, but a data transfer device. And the Photon is staying in place at the Event Horizon, so the bystander will never receive it. Nor will the bystander receive any Photon fired downstream of the Event Horizon; those Photons will move downstream the moment they are fired, for Space moves at > c there.

This metaphor has worked for me to figure out the major workings of black holes that books describe in much more technical or mathematical terms. The metaphor is accurate too. For example, you can use simple acceleration equations like these ( http://id.mind.net/~zona/mstm/physics/mechanics/kinematics/EquationsForAcceleratedMotion/EquationsForAcceleratedMotion.htm) to calculate gravitational time dilation.

For the curved space around a non-rotating black hole, rather than a river you can imagine a sinkhole (or non-swirling whirlpool), where the water flows in from all directions. Then make the sinkhole 3-dimensional. The event horizon is where the speed of inflowing space equals c relative to either the center of the black hole (its singularity) or a free-falling object so distant that its speed towards the sinkhole is negligible.

Zanket,

Correct or not, this view is easiest to visualize and best describes my thoughts as well.

I had considered that the energy could be lost, hence mass until the photo ceased to exist and became absorbed into the total.
But that isn't necessary.

Thanks.

<i>Space may curve but one can travel in any vector, it is not like a slot car track.</i>

Inside a black hole, it is not possible to travel in any direction. In fact, inside the event horizon all travel is towards the singularity. You can't stop, and you can't go backwards.

James R.,

Is that not due to the inward flow? So would not photons flowing inwards, frist need to be slowed, stopped and then sucked in, or do they spiral in as some have suggested?

MacM:

I'm not sure what you mean by "inward flow".

The spacetime inside a black hole is very strange. The time and space coordinates kind of get swapped, so that what was forwards in time outside the hole becomes towards the singularity inside the hole. Just as you can't travel backwards in time outside a black hole, you can't travel away from the singularity inside the hole.

Spirals are possible.

James R.,

I can accept that as an analog view but it is more difficult to think in terms of physical reality.


Thanks.

Originally posted by James R
Inside a black hole, it is not possible to travel in any direction. In fact, inside the event horizon all travel is towards the singularity. You can't stop, and you can't go backwards.

That would be relative to the singularity. But you could travel in other directions relative to other stuff falling in. That’s how a spaceship could cross an event horizon without the ship’s crew noticing anything unusual.

Originally posted by zanket
That would be relative to the singularity. But you could travel in other directions relative to other stuff falling in. That’s how a spaceship could cross an event horizon without the ship’s crew noticing anything unusual. Wouldn't you have to travel faster then the speed of light to move away from the singularity? It would seem that if you were sitting just inside the horizon and looking along the horizon (with singularity on left and outisde on right), no information would be able to travel from left to right, because it would have to have v>c?

Maybe I'm missing something.

Yes, you’d have to travel faster then the speed of light to move away from the singularity, but not to move in a direction away from the singularity relative to other falling objects. Picture a tumbling spaceship; it doesn’t stop tumbling just because it crossed an event horizon. Once it crosses, though, every atom of it must move towards the singularity and no amount of rocket power will change that.

Using the river-of-gravity metaphor (as described more fully above), just picture a boat running at its maximum speed of 20 knots in a river flowing past the shore at > 20 knots. This boat is not restricted in its movements except that it cannot move upstream.

I didnt read the rest of the posts so i do not know if this has been adressed, In a magazine i get, based on science in general it was stated that einsteins theory may have actually been flawed, or that if it isnt, that matter simply stop moving at the endge of a black hole, i will have to find it and reread through the article and get back to you on it