In general relativity, the event horizon is an area within the spacetime outside which events can not influence the outside observer. In layman's terms, it is defined as the "can not return" shell, that is, the boundary at which the gravitational pull of a large object becomes so large that it is impossible to escape. Horizon events are most commonly associated with black holes. The light emitted from within the event horizon can never reach out to the outside observer. Similarly, any object that approaches the horizon from the viewer's side appears to be slowing and never passing through the horizon, with its image becoming more and more redshifted as time passes. This means that the wavelength is longer because the object moves away from the observer. However, the object of the journey, did not experience any strange effects and, in fact, passed through the horizon in a fairly limited time.
Specific horizon types include absolute and clear related horizons but are found around black holes. There are still many different ideas including the Cauchy and Killing horizons; photon and ergospheres fields of Kerr solutions; the particle and cosmological horizons relevant to cosmology; and an isolated and dynamic horizon are vital in current black hole research.
Video Event horizon
Horison black hole event
One of the most notable examples of the event horizon comes from the description of general relativity about black holes, the celestial object so large that no matter or the nearest radiation can escape its gravitational field. Often, this is described as the limit at which the black off-hole velocity is greater than the speed of light. However, a more accurate description is that within this horizon, all paths like light (the path of light it can take) and hence all the paths in the cone of light to the front of the particle in the horizon, which curve so that it falls further into the hole. Once the particles are inside the horizon, moving into the hole is as inevitable as it moves forward in time, and can actually be considered the same as doing it, depending on the coordinate system of the time space used.
The surface of the Schwarzschild radius acts as an event horizon in a non-rotating body that fits within this radius (although the spinning black hole operates slightly differently). The Schwarzschild radius of an object is proportional to its mass. Theoretically, any amount of matter will be a black hole if it is compressed into a suitable space within the appropriate Schwarzschild radius. For the Sun mass this radius is approximately 3 kilometers and for Earth about 9 millimeters. In practice, however, neither the Earth nor the Sun has the required mass and therefore the necessary gravitational force, to overcome the degeneration pressure of electrons and neutrons. The minimal mass required for a star to collapse beyond this pressure is the Tolman-Oppenheimer-Volkoff boundary, which is roughly three solar masses.
The black hole event hole is widely misunderstood. Common, though erroneous, is the idea that black holes "vacuum" matter in their environment, where in reality they are no more capable of finding materials to consume than any other gravitational pull. Like the mass of the universe, matter must be within its gravitational scope for possible arrest or consolidation with other masses. Equally common is the idea that matter can be observed falling into a black hole. This is not possible. Astronomers can only detect the accretion of disks around the black hole, where the material travels at such speed that friction creates a detectable high-energy radiation (similarly, some matter from the accretion disk is forced out along the spin axis of the black hole, creating a jet visible when the flow this interacts with matter like interstellar gas or when they happen to be directed directly to Earth). In addition, distant observers will never really see anything across the horizon. On the contrary, when approaching the hole, the object will appear slower, while the emitted light will further and redshift.
Maps Event horizon
Cosmic event horizon
In cosmology, the observed universe event horizon is the greatest distance from which the emitted light now can reach the observer of the future. This is different from the concept of particle horizon, which represents the greatest moving distance from the light jets in the past the past can reach the observer at any given time. For events beyond that distance, the light has not yet reached our location, even if it is transmitted by the time the Universe begins. How the particle's horizon changes over time depends on the nature of the expansion of the Universe. If the expansion has certain characteristics, there are parts of the universe that can never be observed, no matter how long the observer waits for the light from these areas to arrive. The boundary of the past in which events can not be observed is the event horizon, and it represents the maximum limit of the particle's horizon.
Kriteria untuk menentukan apakah cakrawala partikel untuk alam semesta ada adalah sebagai berikut. Tentukan jarak yang mendekat d p sebagai
In this equation, a is a scale factor, c is the speed of light, and t 0 is the age of the universe. If d p ->? (ie, pointing arbitrarily as far as can be observed), then there is no event horizon. If d p ? ? , the horizon is present.
Examples of cosmological models with no event horizon are universes that are dominated by matter or by radiation. An example of a cosmological model with an event horizon is a universe dominated by cosmological constants (the de Sitter universe).
Calculations of the velocity of cosmological events and the particle horizon are given in papers on the FLRW cosmological model, which approximates the universe as being composed of uninterrupted constituents, each of which is a perfect fluid.
A clear horizon of accelerated particles
If a particle is moving at a constant velocity in a universe that does not progress freely from the gravitational field, any event occurring in the universe will eventually be observable by particles, since the cone of light ahead of this event cuts the particle's world line. On the other hand, if the particle accelerates, in some situations the cone light of some event never cuts the particle's world line. Under these conditions, the visible horizon is present in the frame of reference (acceleration) of the particle, representing the boundary beyond which events can not be observed.
For example, this happens with unilaterally accelerated particles. The timezone diagram of this situation is shown in the picture on the right. When the particle accelerates, it approaches, but never reaches, the speed of light with respect to its original frame of reference. In the space-time diagram, the path is hyperbole, which asymptotically approaches a 45-degree line (light ray path). An event whose conical edge is the asymptote or further away from the asymptote can never be observed by acceleration particles. Within the frame of reference of particles, there appears to be a limit behind which no signal can escape (clear horizon).
While estimates of this type of situation can occur in the real world (in particle accelerators, for example), actual event horizons never exist, because this requires particles to accelerate indefinitely (requiring large amounts of large arbitrary enormous energies). apparatus).
Interact with event horizon
The misconception about the event horizon, especially the horizon of black hole events, is that they represent an irreversible surface that destroys the object that is approaching it. In practice, all of the event horizons appear to be somewhat distant from any observer, and objects sent to the event horizon never seem to cross them from the viewpoint of the sender observer (since the event's horizon-crossing cone never cuts the observer's world line). Trying to make the object near the horizon remains silent by observing the observer requires the application of a force whose magnitude increases infinitely (becomes infinite) closer.
For the case of the horizon felt by the observer accelerating evenly in the empty space, the horizon seems to remain a fixed distance from the observer no matter how the environment moves. Varying the accelerator acceleration may cause the horizon to appear to move over time, or it may prevent the event horizon from being present, depending on the selected acceleration function. The observer never touches the horizon and never passes the location where it seems.
For the case of the horizon perceived by the inhabitants of the de Sitter universe, the horizon always appears as a fixed distance for the non-accelerating observer. It was never contacted, even by a quick observer.
For the case of the horizon around a black hole, stationary observers with respect to distant objects will all agree on where the horizon resides. While this seems to allow the observer down to the hole on the rope (or rod) to contact the horizon, in practice this can not be done. The exact distance to the horizon is limited, so the length of the required rope will be limited too, but if the rope is lowered slowly (so any point on the rope is approximately at rest in Schwarzschild's coordinates), the precise acceleration (G power) experienced by the point on the rope closer and closer to the horizon will be close to infinity, so the rope will be torn. If the rope is lowered quickly (perhaps even in free fall), then indeed the observer at the bottom of the rope can touch and even cross the event horizon. But once this happens it is impossible to pull the bottom of the rope back out of the event horizon, because if the rope is pulled tight, the power along the rope increases without being tied as they approach the event horizon and at some point the rope should break. Furthermore, the break should occur not on the event horizon, but at the point where the second observer can observe it.
Observers who cross the horizon of black hole events can count when they have crossed it, but will not really see or feel anything special happening at that time. In terms of visual appearance, observers who fall into the hole see the black areas that form the horizon as lying at some clear distance beneath them, and have never experienced across this visual horizon. This apparent paradox can be overcome by using the Newton Dynamic Newton Gravity (DNAg), which does not result in an unlimited time span on the event horizon. Another object that has entered the horizon along the same radial path but at a previous time will appear under the observer but still above the visual position of the horizon, and if they have just fallen, the observer can exchange messages with them before one of them. destroyed by a singularity of gravity. Improving tidal forces (and the ultimate impact with hole singularities) is the only visible effect locally. Tidal forces are a function of the mass of black holes. In a realistic black star hole, spaghettification occurs early: the tidal force separates the material well before the event horizon. However, in supermassive black holes, found in galactic centers, spaghettification occurs within the event horizon. A human astronaut will survive the fall through the event horizon only in black holes with a mass of about 10,000 solar masses or larger.
Beyond general relativity
The description of the event horizon given by general relativity is considered incomplete. When conditions in which event horizons occur are modeled using a more comprehensive picture of the workings of the Universe, which includes relativity and quantum mechanics, the event horizon is expected to have properties that are different from those predicted using general relativity alone.
Currently, it is expected that the main impact of quantum effects is for the event horizon to have temperature and radiate emission. For black holes, this manifests as Hawking radiation, and a bigger question about how black holes have temperatures is part of the thermodynamic topic of black holes. To accelerate particles, it manifests as the Unruh effect, which causes the space around the particles to appear to be filled with matter and radiation.
According to the controversial black hole firewall hypothesis, the material that falls into the black hole will be burned to a crisp by the high energy "firewalls" in the event horizon.
An alternative is provided by the principle of complementarity, which, in his opinion, in the remote observer chart, the vaporized matter is capitalized on the horizon and revived as Hawking radiation, while in the infalling observer chart it continues uninterrupted through the inner region and is destroyed in the singularity. This hypothesis does not violate the non-cloned theorem because there is one copy of the information according to the observer given. The black hole of complementarity is actually suggested by the law of string scales approaching the event horizon, indicating that in the Schwarzschild charts they stretch to cover the horizon and thermalizer into the long Planck thick membrane.
The full explanation of the event horizon is expected, at least, to require the theory of quantum gravity. One such candidate theory is M-theory. Another candidate theory is a quantum gravity loop.
The recently published candidate is DNAg who predicts the dynamic increase in gravitational forces near and on the event horizon. DNAg can also easily be translated into a quantum form of gravity, known as advanced quintessence gravity (AQG).
See also
- Acoustic metrics
- Cosmic sensor hypothesis
- Dynamic horizons
- Horizon Events Telescope
- Hawking Radiation
- Rindler coordinates
Note
References
Further reading
- The Universe in a Nutshell by Stephen Hawking
- Kip Thorne (1994). Black Hole and Time Warps . WW Norton. Ã,
- Abhay Ashtekar and Badri Krishnan, "Remote and Dynamic Horizons and Their Applications", Living Rev. Relativity, 7, (2004), 10; Article Online, quoted Feb.2009.
Source of the article : Wikipedia
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