Question: What can escape from the inside of an event horizon of a black hole?
About the article "Black hole", section "Event horizon".

Candidate passages:
An object can cross through the event horizon of a black hole from the outside, and then fall rapidly to the central region where our understanding of physics breaks down.
Since within a black hole the forward light-cone is directed towards the center and the backward light-cone is directed outward, it is not even possible to define time-reversal in the usual manner.
The only way anything can escape from a black hole is as Hawking radiation.
The time reversal of a black hole would be a hypothetical object known as a white hole.
From the outside they appear similar.
While a black hole has a beginning and is inescapable, a white hole has an ending and cannot be entered.
The forward light-cones of a white hole are directed outward; and its backward light-cones are directed towards the center.
The event horizon of a black hole may be thought of as a surface moving outward at the local speed of light and is just on the edge between escaping and falling back.
The event horizon of a white hole is a surface moving inward at the local speed of light and is just on the edge between being swept outward and succeeding in reaching the center.
They are two different kinds of horizons—the horizon of a white hole is like the horizon of a black hole turned inside-out.
The modern view of black hole irreversibility is to relate it to the second law of thermodynamics, since black holes are viewed as thermodynamic objects.
Indeed, according to the Gauge-gravity duality conjecture, all microscopic processes in a black hole are reversible, and only the collective behavior is irreversible, as in any other macroscopic, thermal system. 
If formula_15 then there exists a Cauchy horizon between formula_16 and regions of the manifold not completely determined by information on formula_1.
A clear physical example of a Cauchy horizon is the second horizon inside a charged or rotating black hole.
The outermost horizon is an event horizon, beyond which information cannot escape, but where the future is still determined from the conditions outside.
Inside the inner horizon, the Cauchy horizon, the singularity is visible and to predict the future requires additional data about what comes out of the singularity.
Since a black hole Cauchy horizon only forms in a region where the geodesics are outgoing, in radial coordinates, in a region where the central singularity is repulsive, it is hard to imagine exactly how it forms.
For this reason, Kerr and others suggest that a Cauchy horizon never forms, instead that the inner horizon is in fact a spacelike or timelike singularity.
A homogeneous space-time with a Cauchy horizon is anti-de Sitter space. 
The Schwarzschild radius of an object is proportional to the mass.
Accordingly, the Sun has a Schwarzschild radius of approximately while the Earth's is only about 9.0 mm, the size of a peanut.
The observable universe's mass has a Schwarzschild radius of approximately 10 billion light years.
An object whose radius is smaller than its Schwarzschild radius is called a black hole.
The surface at the Schwarzschild radius acts as an event horizon in a non-rotating body (a rotating black hole operates slightly differently).
Neither light nor particles can escape through this surface from the region inside, hence the name "black hole".
The Schwarzschild radius of the supermassive black hole at our Galactic Center would be approximately 13.3 million kilometres. 
In general relativity, an absolute horizon is a boundary in spacetime, defined with respect to the external universe, inside of which events cannot affect an external observer.
Light emitted inside the horizon can never reach the observer, and anything that passes through the horizon from the observer's side is never seen again.
An absolute horizon is the boundary of a black hole by definition.
In the context of black holes, the absolute horizon is almost exclusively referred to as an event horizon, though this is often used as a more general term for all types of horizons.
The absolute horizon is just one type of horizon.
For example, important distinctions must be made between absolute horizons and apparent horizons.
See also the articles on ergosphere, Cauchy horizon, the Reissner-Nordström solution, photon sphere, Killing horizon and naked singularity; the notion of a horizon in general relativity is subtle, and depends on fine distinctions. 
The defining feature of a black hole is the appearance of an event horizon—a boundary in spacetime through which matter and light can only pass inward towards the mass of the black hole.
Nothing, not even light, can escape from inside the event horizon.
The event horizon is referred to as such because if an event occurs within the boundary, information from that event cannot reach an outside observer, making it impossible to determine if such an event occurred.
As predicted by general relativity, the presence of a mass deforms spacetime in such a way that the paths taken by particles bend towards the mass.
At the event horizon of a black hole, this deformation becomes so strong that there are no paths that lead away from the black hole.
To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole.
Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow down as it approaches the event horizon, taking an infinite time to reach it.
At the same time, all processes on this object slow down, for a fixed outside observer, causing emitted light to appear redder and dimmer, an effect known as gravitational redshift.
Eventually, at a point just before it reaches the event horizon, the falling object becomes so dim that it can no longer be seen.
On the other hand, an indestructible observer falling into a black hole does not notice any of these effects as he crosses the event horizon.
According to his own clock, which appears to him to tick normally, he crosses the event horizon after a finite time without noting any singular behaviour.
In particular, he is unable to determine exactly when he crosses it, as it is impossible to determine the location of the event horizon from local observations.
The shape of the event horizon of a black hole is always approximately spherical.
For non-rotating (static) black holes the geometry is precisely spherical, while for rotating black holes the sphere is somewhat oblate.