Physics

[LiamOS]

A lesser purpose of this thread is to allow members to ask questions about physics which they need clarification on or want an explanation on.

In my time spent here, I've been told many a time how conventional science fails and falls short in areas. As such, I decided to make this thread. However, as there are many on the subject of Biology and its many branches, I felt one to address the issues in physics would be appropriate.
For the purposes of this thread, physics covers Nuclear Physics, Particle Physics, Astronomy, Cosmology, Relativity, Quantum Mechanics(QCD, QED...), Electromagnetism, Optics and Thermodynamics.
The conventional theories in each field will be taken, in the context of this thread, as the best explanation currently available:
The Big Bang, the Standard Model(Particle physics), etc.

Questions for debate:
-Other than that which we do not yet know(Higgs Boson, etc.), are there any significant shortcomings in the conventional physics of the day? If so, where and why?
-Some theories are based on underlying assumptions. Are any of these assumptions flawed or not necessarily true?

With our current knowledge of the universe from a physicists point of view, is it logical to infer than a deity is a necessity? Why or why not?

On a final note, this is a physics thread, so don't hold back on using mathematics as support for your hypotheses.

[Crazee]

I've hypothesized that black holes are gateways to other dimensions due to very similar reasons. That doesn't mean that we would be able to physically survive a trip through one. I think that if more research was done on Out-of-Body experiences and Astral Projection, than we could plausibly send someone's consciousness through a black hole in the future.

Sorry, but I can't see any connection between Black Holes and Out of Body Experiences. Do you suggest there is one?

My idea is that since our current understanding of physics says that no matter can maintain its shape when it travels into a black hole, than if we want to explore the interior of a black hold, we would need to find a non-physical way to travel into it.

Non-physical methods of travel are usually referred to as OBE's when they are involuntary, and astral projection when they are induced voluntarily. If certain people that are very good at traveling outside of the body could be recruited by science, than maybe they could attempt to see the inside of a black hole in an out of body state.

Just a theory of mine.

[mich]

From what I see, we did indeed leave the rest mass energy for the photon as being 0; and we are left with pc. But it seems that pc would then be equal to
mc ^2 , wouldn't it? In other words, mc ^ 2 = p * c + rest mass energy, which, in this case is 0 ?

Andre

pc mc², since m = 0 in the case of the photon.

For photons, it follows from
E² = p²c² + m²c⁴
and
E =
by setting m = 0, that
p = /c

Hope this helps.

Hello Aki; thanks for responding. Now, as I mentioned 100%, I am only trying to visualize what I don't understand and am not arguing against any theories. So don't take this as something I don't agree with, but simply as something I don't understand well enough.

My problem with the above is that while you claim that e = m c ^2 cannot hold for the photon as it doesn't have any mass, we are still left with the photon having momentum in the case of p = h f / c, and momentum does include the existance of mass.
The way I understand it, the photon could well have a mass due to the energy/mass equivalence eventhough it's rest mass is 0.

Andre

[LiamOS]

Hello Aki; thanks for responding. Now, as I mentioned 100%, I am only trying to visualize what I don't understand and am not arguing against any theories. So don't take this as something I don't agree with, but simply as something I don't understand well enough.

My problem with the above is that while you claim that e = m c ^2 cannot hold for the photon as it doesn't have any mass, we are still left with the photon having momentum in the case of p = h f / c, and momentum does include the existance of mass.
The way I understand it, the photon could well have a mass due to the energy/mass equivalence eventhough it's rest mass is 0.

Andre

Momentum only necessitates the existence of mass in the classical ideas of physics.
Consider two of Maxwell's equations:


and then consider a coherent, monochromatic beam of electromagnetic radiation incident on a conductive surface.
The electric field will induce an oscillating current, and the magnetic field causes a force on these currents, which by the above equations is in the same direction as the beam of light. The existence of this force is indicative of light having momentum, since otherwise we could be witnessing the creation of momentum(Which is just stupid in non-quantum physics. ).

[100%atheist]

My idea is that since our current understanding of physics says that no matter can maintain its shape when it travels into a black hole, than if we want to explore the interior of a black hold, we would need to find a non-physical way to travel into it.

No, this only means we have to find physical way to describe the black hole. And, by the way, there are some approaches to solving this problem.

Non-physical methods of travel ...

There are no non-physical methods of physical travel. You can imagine however that you travel to Bahamas but it would be another story.

are usually referred to as OBE's when they are involuntary, and astral projection when they are induced voluntarily.

And the facts supporting OBEs are .... ?
I think I saw some physiology research addressing the claims for OBE. I thought that there are some pretty good physical explanations to how our brain works in certain situations.

If certain people that are very good at traveling outside of the body could be recruited by science, than maybe they could attempt to see the inside of a black hole in an out of body state.

Just a theory of mine.

I think those people have been already recruited for science experiments in psychology and biophysics.

Please watch here:

[ThatGirlAgain]

My idea is that since our current understanding of physics says that no matter can maintain its shape when it travels into a black hole, than if we want to explore the interior of a black hold, we would need to find a non-physical way to travel into it.

Strictly speaking no matter can maintain its precise shape ever because the gravitational influences from other moving bodies are constantly changing. But if we instead talk about functional shape, like not being torn apart by tidal forces, it is not necessarily the case that crossing an event horizon results in destruction.

Tidal forces are related to the gravitational gradient, the difference in gravitational potential at different distances from the effective center of mass. An extremely massive black hole, say several galaxies worth, would be very large (relatively speaking, no pun intended) and could have a rather mild gravitational gradient. A person crossing the event horizon need not notice anything unusual but could never get out again. Such an observer could explore the interior of the black hole, up until the inevitable encounter with the singularity, but could not report on it to anyone outside.

Interestingly, to an external observer the explorer would never cross the event horizon but would continuously approach it at ever slower speeds. The image of the falling explorer would be increasingly red shifted until it became effectively undetectable. The adventures of the observer inside the black hole would be happening an infinite time in the future as far as the external observer is concerned.

[JohnPaul]

ThatGirlAgain wrote:

Interestingly, to an external observer the explorer would never cross the event horizon but would continuously approach it at ever slower speeds. The image of the falling explorer would be increasingly red shifted until it became effectively undetectable. The adventures of the observer inside the black hole would be happening an infinite time in the future as far as the external observer is concerned.

The apparent slowing and eventual stopping of time and the increasing red shift of light from an object entering a black hole is an illusion caused by the geometric properties of the universe itself in relation to light which transmits information from an object to an external observer. This can be easily seen and is obvious from a relativly simple model based on Einstein's early hypersphere model of the universe.

To simplify the model, let's reduce it to an ordinary 3-D sphere in which the surface is thought of as a 2-dimensional universe with 2-D "flatlanders" running around in their flat universe. Their universe is obviously curved to us, but they cannot perceive that. The sphere is expanding out from a center, which is the "time" origin of their universe, and the radial direction perpendicular to the surface is their "time" direction. Inside the sphere surface is the "past" and outside is the "future," where we supernatural humans reside in the 3-D universe which can't even be imagined by the flatlanders.

The "history" of each flatlander and other objects in the flat universe is a "worldline" which extends radially into the past toward the center of the sphere and outward from the surface into the future. The 2-D intersections of the worldlines with the universe surface is what the flatlanders perceive is the "present time" or the "real world."

In this universe model, a black hole can be thought of as a funnel-shaped depression in the universe-surface. Light in this 2-D universe can be thought of as being emitted perpendicularly from the worldlines of objects and thus parallel to the immediately surrounding surface, but the light travels in three dimensions, not two, and thus is not limited to the universe surface, but travels "up" into the "future" in straight lines, not in the curved universe surface. When light is emitted from a flatland object, since the universe surface is curved down away from the object, the path of the light "rises" from the "present" surface and intersects the worldline of a distant observer, which is tilted away from the worldline of the light source, sometime in the "future." Got that? It is essential to the geometric interpretation of this model.

When a flatland object moves into the funnel-shaped black hole, the surface inside the black hole, and thus the object's worldline perpendicular to the tilted surface, becomes tilted in relation to the surrounding more distant universe. Light emitted from the object as it enters the black hole thus becomes increasing tilted up from the surrounding surface and intersects the worldline of a distant observer more and more into the "future" of the distant observer. As the object approaches the neck of the funnel, the light emitted from it becomes almost perpendicular to the surrounding universe, tilted "'up" and reaches the worldline of the distant observer only in the very distant future. Thus the movement of the object seems to slow down to the observer, because light from it reaches the observer only farther and farther into the future. Remember that the universe "surface" is expanding, so the "present" time of the flatlander observer reaches the point of intersection with the light farther and farther into his future.

Likewise, the "wavelength" of the light, the distance between wave peaks in the light's 3-D path, seem to the observer to be farther and farther apart because the light's 3-D straightline path is increasing tilted in relation to the observer's worldline. This is interpretted as a "red shift,"although in the actual 3-D path of the light, no change occurs in the real 3-D wavelength.

It is not necessary that the funnel-shaped neck of the black hole actually reach a point, or singularity. All that is necessary is that the "walls" of the black hole become parallel to each other, as the neck of a real funnel often does. This in effect "stops" time inside the black hole as seen by a distant observer.

All this immediately becomes obvious simply by imagining such a model. No mathematics is necessary.

I am sure you are asleep by now, so I will quit.

John

[ThatGirlAgain]

Hi JohnPaul

I appreciate the effort that went into this description. However, there are several issues with your model.

Light in this 2-D universe can be thought of as being emitted perpendicularly from the worldlines of objects and thus parallel to the immediately surrounding surface, but the light travels in three dimensions, not two, and thus is not limited to the universe surface, but travels "up" into the "future" in straight lines, not in the curved universe surface. When light is emitted from a flatland object, since the universe surface is curved down away from the object, the path of the light "rises" from the "present" surface and intersects the worldline of a distant observer, which is tilted away from the worldline of the light source, sometime in the "future." Got that? It is essential to the geometric interpretation of this model.

The light does not travel in 3 dimensions any more than any other worldline does. That is, they all do. The light is not travelling in a straight line above the universe surface. It is following a geodesic along that expanding surface and will encounter all the world lines that also intersect that geodesic. (One consequence of that is that the light will follow a somewhat non-linear path due to nearby gravitating objects but that does not really matter for this discussion.)

The light therefore does not intersect a point on the worldline of a distant (future) observer at a tilted angle but exactly perpendicular to the surface since the light is traveling along the expanding surface. This is a natural consequence of the speed of light always being a constant when measured locally by any observer.

In this universe model, a black hole can be thought of as a funnel-shaped depression in the universe-surface.

No. A black hole will not be a depression leading back into the past (toward the center of the sphere). It will be a funnel shaped tower on the surface leading into the future. According to General Relativity, inside the event horizon space-time has become so bent that down the rabbit hole is that same as forward into the future (away from the center of the sphere).

To jump back to your introduction:

The apparent slowing and eventual stopping of time and the increasing red shift of light from an object entering a black hole is an illusion caused by the geometric properties of the universe itself in relation to light which transmits information from an object to an external observer. This can be easily seen and is obvious from a relatively simple model based on Einstein's early hypersphere model of the universe.

What is real and what is illusion is a matter of assumptions. You appear to be assuming a Euclidean super-space in which the Einsteinian non-Euclidean space is embedded. Your model seems to be a Lorentzian one in which there is an absolute spatial frame of reference but one that cannot be detected and plays no part in predictions. All it does is allow a preferred frame of reference to be defined.

In Einsteinian relativity there is no preferred frame of reference and which observations are illusions is a matter of viewpoint. To each observer, its observations are real. To say that the appearance of an explorer falling forever toward a black hole without ever crossing the event horizon is illusory implies that the explorer has really already crossed that event horizon. This assumes that there is an absolute Now. Even Special Relativity finds no meaning in the idea of simultaneity. To the external observer, the explorer will never reach the event horizon. To the explorer the event horizon has been breached in a finite span of time. Who is right? In GR they both are. There is no absolute time. Time is local and dependent on the observers frame of reference.

Speculations about the potential observability or explanatory power of an absolute frame of reference are fun and welcome. But mainstream physics has done very well without needing to assume such an entity.


Additional comment:

It is not necessary that the funnel-shaped neck of the black hole actually reach a point, or singularity. All that is necessary is that the "walls" of the black hole become parallel to each other, as the neck of a real funnel often does. This in effect "stops" time inside the black hole as seen by a distant observer.

True. It appears that for a Schwarzschild (non-rotating, uncharged) black hole, there is necessarily an unavoidable singularity in store for any intrepid explorers. For rotating and/or charged black holes this may not be the case. Since any actual black holes are almost certainly rotating, singularities may not be common.

[JohnPaul]

Hi JohnPaul

I appreciate the effort that went into this description. However, there are several issues with your model.

Light in this 2-D universe can be thought of as being emitted perpendicularly from the worldlines of objects and thus parallel to the immediately surrounding surface, but the light travels in three dimensions, not two, and thus is not limited to the universe surface, but travels "up" into the "future" in straight lines, not in the curved universe surface. When light is emitted from a flatland object, since the universe surface is curved down away from the object, the path of the light "rises" from the "present" surface and intersects the worldline of a distant observer, which is tilted away from the worldline of the light source, sometime in the "future." Got that? It is essential to the geometric interpretation of this model.

The light does not travel in 3 dimensions any more than any other worldline does. That is, they all do. The light is not travelling in a straight line above the universe surface. It is following a geodesic along that expanding surface and will encounter all the world lines that also intersect that geodesic. (One consequence of that is that the light will follow a somewhat non-linear path due to nearby gravitating objects but that does not really matter for this discussion.)

The light therefore does not intersect a point on the worldline of a distant (future) observer at a tilted angle but exactly perpendicular to the surface since the light is traveling along the expanding surface. This is a natural consequence of the speed of light always being a constant when measured locally by any observer.

In this universe model, a black hole can be thought of as a funnel-shaped depression in the universe-surface.

No. A black hole will not be a depression leading back into the past (toward the center of the sphere). It will be a funnel shaped tower on the surface leading into the future. According to General Relativity, inside the event horizon space-time has become so bent that down the rabbit hole is that same as forward into the future (away from the center of the sphere).

To jump back to your introduction:

The apparent slowing and eventual stopping of time and the increasing red shift of light from an object entering a black hole is an illusion caused by the geometric properties of the universe itself in relation to light which transmits information from an object to an external observer. This can be easily seen and is obvious from a relatively simple model based on Einstein's early hypersphere model of the universe.

What is real and what is illusion is a matter of assumptions. You appear to be assuming a Euclidean super-space in which the Einsteinian non-Euclidean space is embedded. Your model seems to be a Lorentzian one in which there is an absolute spatial frame of reference but one that cannot be detected and plays no part in predictions. All it does is allow a preferred frame of reference to be defined.

In Einsteinian relativity there is no preferred frame of reference and which observations are illusions is a matter of viewpoint. To each observer, its observations are real. To say that the appearance of an explorer falling forever toward a black hole without ever crossing the event horizon is illusory implies that the explorer has really already crossed that event horizon. This assumes that there is an absolute Now. Even Special Relativity finds no meaning in the idea of simultaneity. To the external observer, the explorer will never reach the event horizon. To the explorer the event horizon has been breached in a finite span of time. Who is right? In GR they both are. There is no absolute time. Time is local and dependent on the observers frame of reference.

Speculations about the potential observability or explanatory power of an absolute frame of reference are fun and welcome. But mainstream physics has done very well without needing to assume such an entity.


Additional comment:

It is not necessary that the funnel-shaped neck of the black hole actually reach a point, or singularity. All that is necessary is that the "walls" of the black hole become parallel to each other, as the neck of a real funnel often does. This in effect "stops" time inside the black hole as seen by a distant observer.

True. It appears that for a Schwarzschild (non-rotating, uncharged) black hole, there is necessarily an unavoidable singularity in store for any intrepid explorers. For rotating and/or charged black holes this may not be the case. Since any actual black holes are almost certainly rotating, singularities may not be common.

Thanks. Your comments have certainly given me something to think about. My model was a consensus of ideas I have picked up over the years at a very amateur level. I am sure there are more than a few problems with it. Its only advantage that I can see, however wrong, is that it does provide a simple intuitive visualization of the slowing of time and red shift of light from a black hole.

One problem I can immediately see in my model of a 2-D universe is that if light is emitted perpendicular to a worldline, that means it is parallel to the surrounding expanding universe and therefore its velocity is infinite at the instant of emission and slows down as time "passes." What the flatlander sees as the "path" of the light is merely the intersection of the 3-D light with his 2-D universe, which seems to move as his universe expands. I am suspicious of anything infinite! However, in our "real world," light does not "accelerate" to the velocity of light when emitted, but already has the velocity of light at the instant of emission. This "infinite" acceleration bothers me, even with no mass involved.

To a 3-D observer, the entire past and future of the 2-D flatlanders would exist simultaneously. The "time" of the 3-D observer would necessarily be a higher-dimensional kind of time very different from that experienced by the flatlanders, but not necessarily an absolute frame of reference. There are many more dimensions to go!

Thanks again.

John

[JohnPaul]

ThatGirlAgain wrote:

The light therefore does not intersect a point on the worldline of a distant (future) observer at a tilted angle but exactly perpendicular to the surface since the light is traveling along the expanding surface. This is a natural consequence of the speed of light always being a constant when measured locally by any observer.

No. Neither the worldlines nor the light are "moving," but simply exist staticly in the larger 3-D space. What the flatlanders perceive as the moving light is simply the intersection of the 3-D light with their expanding 2-D universe. All motion in this model is due only to the motion of expansion of the universe "surface" itself.

No. A black hole will not be a depression leading back into the past (toward the center of the sphere). It will be a funnel shaped tower on the surface leading into the future. According to General Relativity, inside the event horizon space-time has become so bent that down the rabbit hole is that same as forward into the future (away from the center of the sphere).

If the expanding 2-D surface is thought of as the "present" time, then it can be imagined that the 3-D worldlines "drag" the surface as it expands over them and cause the surface to curve slightly "down" near them. This would explain gravity. When a star collapses, the dragging curvature becomes extreme and can actually cause the curvature to become perpendicular to the surrounding universe at the singularity. In this sense, the singularity might be in the future in an absolute sense, but would be closer to the center of the model. This peculiar behavior of time in a black hole is a little too mind-boggling for me to visualize, even in a simplified 2-D midel, so I will leave it to you.

John

[mich]

Hello Aki; thanks for responding. Now, as I mentioned 100%, I am only trying to visualize what I don't understand and am not arguing against any theories. So don't take this as something I don't agree with, but simply as something I don't understand well enough.

My problem with the above is that while you claim that e = m c ^2 cannot hold for the photon as it doesn't have any mass, we are still left with the photon having momentum in the case of p = h f / c, and momentum does include the existance of mass.
The way I understand it, the photon could well have a mass due to the energy/mass equivalence eventhough it's rest mass is 0.

Andre

Momentum only necessitates the existence of mass in the classical ideas of physics.
Consider two of Maxwell's equations:


and then consider a coherent, monochromatic beam of electromagnetic radiation incident on a conductive surface.
The electric field will induce an oscillating current, and the magnetic field causes a force on these currents, which by the above equations is in the same direction as the beam of light. The existence of this force is indicative of light having momentum, since otherwise we could be witnessing the creation of momentum(Which is just stupid in non-quantum physics. ).

Again,my intent is not in arguing against your explanation but showing where I get confused. Would not this force explained in terms of momentum due to our explanation of the photon in terms of a particle though? Would Maxwell have used the description of momentum or wouldn't he rather have explained it in terms of pressures coming from the light medium (ether) such as the qualities of permeability and permittivity?

Here is an explanation taken from wikipedia ( so I understand that it might not be accurate) about the relativistic mass of a photon.

http://en.wikipedia.org/wiki/Mass%E2%80 ... quivalence
Massless particles
Massless particles have zero rest mass. Their relativistic mass is simply their relativistic energy, divided by c2, or m(relativistic) = E/c2.[8][9] The energy for photons is E = hf where h is Planck's constant and f is the photon frequency. This frequency and thus the relativistic energy are frame-dependent

Andre