Questions and Answers
Hi,
I have a question:
Suppose that outside our observable universe with radius c 46bly there is indeed the 2/3 universe mass that is conjectured.
How then do you explain how information of this mass can reach us, as the red-shift becomes infinite at c46bly from us and thus no information should reach us from outside the observable universe?
It seems that the anomalies mentioned: such as the power spectrum and the bias towards one hemisphere represent information that is reaching us, when this should not be possible.
Does this then connect with the idea that information can indeed come out of the construct known as a "black hole"? If so then the "black hole" is a non-such, if not, then the anomalies must have explanations within the observable universe.
Regards, John
Hi John,
Great question. I think it goes to the heart of the matter. It relates to one of the great recent scientific battles of our time between Susskind and Hawking - the Black Hole War.
The short answer would be that it is analogous to objects near but outside the event horizon of a black hole. No information can be communicated from the singularity to the region beyond the event horizon: the effects of the black hole, however, go beyond the event horizon, objects go into orbit around black holes.
It must be pointed out that the widely accepted flat universe model also raises the question of communication from beyond our observable universe in terms of how 'smooth' the MBR is. Cosmologists get around this problem by assuming in the early moments of the big bang the universe expanded faster than the speed of light, ergo 'inflation'. The truth is, we really have no idea what is going on at the largest scale from a gravitational or structural perspective.
A curved model of the universe does not preclude the same inflationary period for potentially getting around the communication problem. There is also some unintuitive aspects of gravity in the GR framework. For example, the sun and the earth move about a point that represents their combined center of mass. So the sun is wobbling 'back and forth' as the earth revolves around it. It takes 8 minutes for the light from the sun to reach our planet. By this notion you would think that at any point in time the sun's pull on the earth would be from a position where the sun was 8 minutes previous. Not so. The direction of the tidal forces and hence the direction of the pull of the sun on the earth turns out to be in line with the sun's current position, not where it was 8 minutes previous. The reasons for this can be calculated using GR and perhaps is not the best argument to put forward but does underscore the strangeness of things.
Using the curved model for the universe, (i.e. finite/positively curved 2/3 the mass at the south pole) - the edge of our observable universe almost (but not quite) coincides with the event horizon of the black hole at the south pole. This has the potential to bring what appear to be opposite extremities of our universe into closer proximity, thereby 'improving' (but not eliminating) the communication restrictions. It involves the same argument about how the effects of the mass of a black hole are felt outside its event horizon. The answer being that the gravitational information is smeared on the event horizon itself.
In the proposed model, the gravitational well for the black pole would have been established at the instant of the big bang. The geometry of the well therefore exists from that instant onwards. Once it is established, the well is, for all intents and purposes, static from the perspective of the balance of matter in the universe. There is no need for information to 'propagate' outwards from the singularity. All information related to matter that subsequently falls into the black pole and consequently increases its mass, after that point in time, remains on the surface of the black pole. On the other hand, if for some reason the mass at the black pole were to instantaneously vanish, (which obviously could not actually happen) we would never be able to detect this as the information related to the change in gravitational potential would not be able to escape from the gravitational well.
Cheers,
Rick
I have a question:
Suppose that outside our observable universe with radius c 46bly there is indeed the 2/3 universe mass that is conjectured.
How then do you explain how information of this mass can reach us, as the red-shift becomes infinite at c46bly from us and thus no information should reach us from outside the observable universe?
It seems that the anomalies mentioned: such as the power spectrum and the bias towards one hemisphere represent information that is reaching us, when this should not be possible.
Does this then connect with the idea that information can indeed come out of the construct known as a "black hole"? If so then the "black hole" is a non-such, if not, then the anomalies must have explanations within the observable universe.
Regards, John
Hi John,
Great question. I think it goes to the heart of the matter. It relates to one of the great recent scientific battles of our time between Susskind and Hawking - the Black Hole War.
The short answer would be that it is analogous to objects near but outside the event horizon of a black hole. No information can be communicated from the singularity to the region beyond the event horizon: the effects of the black hole, however, go beyond the event horizon, objects go into orbit around black holes.
It must be pointed out that the widely accepted flat universe model also raises the question of communication from beyond our observable universe in terms of how 'smooth' the MBR is. Cosmologists get around this problem by assuming in the early moments of the big bang the universe expanded faster than the speed of light, ergo 'inflation'. The truth is, we really have no idea what is going on at the largest scale from a gravitational or structural perspective.
A curved model of the universe does not preclude the same inflationary period for potentially getting around the communication problem. There is also some unintuitive aspects of gravity in the GR framework. For example, the sun and the earth move about a point that represents their combined center of mass. So the sun is wobbling 'back and forth' as the earth revolves around it. It takes 8 minutes for the light from the sun to reach our planet. By this notion you would think that at any point in time the sun's pull on the earth would be from a position where the sun was 8 minutes previous. Not so. The direction of the tidal forces and hence the direction of the pull of the sun on the earth turns out to be in line with the sun's current position, not where it was 8 minutes previous. The reasons for this can be calculated using GR and perhaps is not the best argument to put forward but does underscore the strangeness of things.
Using the curved model for the universe, (i.e. finite/positively curved 2/3 the mass at the south pole) - the edge of our observable universe almost (but not quite) coincides with the event horizon of the black hole at the south pole. This has the potential to bring what appear to be opposite extremities of our universe into closer proximity, thereby 'improving' (but not eliminating) the communication restrictions. It involves the same argument about how the effects of the mass of a black hole are felt outside its event horizon. The answer being that the gravitational information is smeared on the event horizon itself.
In the proposed model, the gravitational well for the black pole would have been established at the instant of the big bang. The geometry of the well therefore exists from that instant onwards. Once it is established, the well is, for all intents and purposes, static from the perspective of the balance of matter in the universe. There is no need for information to 'propagate' outwards from the singularity. All information related to matter that subsequently falls into the black pole and consequently increases its mass, after that point in time, remains on the surface of the black pole. On the other hand, if for some reason the mass at the black pole were to instantaneously vanish, (which obviously could not actually happen) we would never be able to detect this as the information related to the change in gravitational potential would not be able to escape from the gravitational well.
Cheers,
Rick
