What is it like inside a black hole??

Question

My 7 year old son would like to know.

Answer 1

Black holes require the general relativistic concept of a curved spacetime: their most striking properties rely on a distortion of the geometry of the space surrounding them. One of the most intriguing predictions regarding black holes implies the existence of a final singularity where the lorentzian signature of the metric (+++-) becomes euclidean (++++).

Event horizon
The "surface" of a black hole is the so-called event horizon, an imaginary surface surrounding the mass of the black hole. Stephen Hawking proved that the topology of the event horizon of a non-spinning black hole is a sphere. At the event horizon, the escape velocity is equal to the speed of light. Thus, anything inside the event horizon, including a photon, is prevented from escaping across the event horizon by the extremely strong gravitational field. Particles from outside this region can fall in, cross the event horizon, and will never be able to leave.

Since external observers cannot probe the interior of a black hole, according to classical general relativity, black holes can be entirely characterised according to three parameters: mass, angular momentum, and electric charge. This principle is summarised by the saying, coined by John Wheeler, "black holes have no hair" meaning that there are no features that distinguish one black hole from another, other than mass, charge, and angular momentum

Space-time distortion and frame of reference
Objects in a gravitational field experience a slowing down of time, called time dilation. This phenomenon has been verified experimentally in the Scout rocket experiment of 1976,[10] and is, for example, taken into account in the Global Positioning System (GPS). Near the event horizon, the time dilation increases rapidly. To the distant observer, a falling object's movement slows down, approaches but never reaches the event horizon. Any escaping photons do not slow down when escaping the gravity well but experience redshifting. From the falling object's frame of reference, it will cross the event horizon and reach the singularity at the center of the black hole within a finite amount of time.

Inside the event horizon
Spacetime inside the event horizon of an uncharged non-rotating black hole is peculiar in that the singularity is in every observer's future, so all particles within the event horizon move inexorably towards it (Penrose and Hawking). This means that there is a conceptual inaccuracy in the non-relativistic concept of a black hole as originally proposed by John Michell in 1783. In Michell's theory, the escape velocity equals the speed of light, but it would still, for example, be theoretically possible to hoist an object out of a black hole using a rope. General relativity eliminates such loopholes, because once an object is inside the event horizon, its time-line contains an end-point to time itself, and no possible world-lines come back out through the event horizon. A consequence of this is that a pilot in a powerful rocket ship that had just crossed the event horizon who tried to accelerate away from the singularity would reach it sooner in his frame, since geodesics (unaccelerated paths) are paths that maximise proper time.[11]

As the object continues to approach the singularity, it will be stretched radially with respect to the black hole and compressed in directions perpendicular to this axis. This phenomenon, called spaghettification, occurs as a result of tidal forces: the parts of the object closer to the singularity feel a stronger pull towards it (causing stretching along the axis), and all parts are pulled in the direction of the singularity, which is only aligned with the object's average motion along the axis of the object (causing compression towards the axis).

Singularity
At the centre of the black hole, well inside the event horizon, general relativity predicts a singularity, a place where the curvature of spacetime becomes infinite and gravitational forces become infinitely strong.

It is expected that future refinements or generalisations of general relativity (in particular quantum gravity) will change what is thought about the nature of black hole interiors. Most theorists interpret the mathematical singularity of the equations as indicating that the current theory is not complete, and that new phenomena must come into play as one approaches the singularity.[12]

The cosmic censorship hypothesis asserts that there are no naked singularities in general relativity. This hypothesis is that every singularity is hidden behind an event horizon and cannot be probed. Whether this hypothesis be true remains an active area of theoretical research.

Another school of thought holds that no singularity occurs, because of a bubble-like local inflation in the interior of the collapsing star.[13] Radii stop converging as they approach the event horizon, are parallel at the horizon, and begin diverging in the interior. The solution resembles a wormhole (from the exterior to the interior) in a neighborhood of the horizon, with the horizon as the neck.

Answer 2

Well, it isn't that they are inside one another, but that they combine to make a bigger one. Because of the nature of a black hole we cannot be in one, it is basically where a super giant star supernovas, and the core of the star is what makes the black hole, the core of the star is so tightly compacted that a teaspoon of the material would weigh as much as the Earth. This makes for extremely high gravity, and, there are billions of black holes in the Universe, so i am assuming that question two is that we have black holes in our Galaxy, which is true, they believe there is a massive one in the center of the Milky Way,a nd most black holes do reside in the centers of all galaxies. That is to say we are not in a black hole, because not much is known about them, as the closest one to us is 30,000 light years away, they have some understanding but do not know all the answers. However, I think if we were in one it would be tearing the Sun apart, so we would be able to see the gas stream from the black hole pulling off the layers of gas from the Sun. Another reason is that there are not too many double stars, which would be close enough to both supernova at the same time to make two black holes within each others grasp, now this isn't to say that two colliding Galaxies may eventually end up with their black holes nearing each other, but the distance between stars is too great for this to happen.

Answer 3

What a great question. You must have an extremely gifted 7 year old son. While I won't pretend to have the knowledge to answer his question, I do know of a website that is geared for kids his age. Take him to http://imagine.gsfc.nasa.gov/docs/ask_astro/black_holes.html and help guide him through the various answers they offer.

Thank you so much for reminding me of that special time in my son's life. He is so fortunate to have a parent that takes time to help him understand this vast world we live in. Who knows, he might be one of the first astronauts to experience travel through a black hole.

Peace.

Answer 4

There is no answer, but scientists believe information cannot be destroyed and a Black Hole has absorbed a lot. So one answer would be 'full of tiny men searching for something that they know is there, but it is too small to find'. Especially as someone has turned the light off.

How do we know this is not so until we have seen it is not so.

Answer 5

The gravity is so strong that everything is condensed into a single point of infinite density and will be infinitely small. This point is called singularity. The gravity is so strong that nothing, not even light, can escape.

Answer 6

Claustrophobic.

Answer 7

1. It's very dark.

2. It's very small.

3. You're very dead.

Answer 8

It doesn't matter, the pressure would crush us to death before we could see anything.

Answer 9

a cork