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R. Barrett and P. P. Delsanto
The very natures of time and space become intermingled here, as in the plot
of a far-fetched science fiction movie. However, as we shall see later in this
Chapter, black holes have been detected by astronomers, and are now an
accepted consequence of the theory of General Relativity.
The possibility of creating a mini black hole on earth in an accelerator, such
as the Large Hadron Collider in Geneva, has been raised, with some concern
that it might escape and devour the earth. At first it was thought that the
accelerator had insufficient energy for black hole production. More recent
work shows that such an event is a real possibility. Luckily the calculations
indicate that such tiny black holes would pose no danger, since they would
soon shrink and disappear before being able to gobble up any matter [4, 5].
The second solution of the Field Equations that we wish to consider here is
the one for a homogeneous, isotropic universe. This is just physicists’ jargon
for a universe that is not “lumpy”, and looks the same in all directions. One
might well argue that our universe, comprising, as it does, stars, galaxies of
stars and clusters of galaxies, is indeed “lumpy”. From our perspective here on
earth, it most certainly is. However, by moving far enough away and taking
a big picture, these inhomogeneities merge into each other in the same way
that the pixels on a TV screen merge together, unless one sits too close. They
should not affect the results of the model too much. 7
Solutions for this model of the universe were developed independently by
Alexander Friedmann, Georges Lemaître, Howard P. Robertson and Arthur
Geoffrey Walker in the 1920s and 1930s. The model is generally known,
rather unimaginatively, as the FLRW model, and is discussed in detail later
in Chap. 10. One of its characteristics is the presence of a singularity which
is identified with the big bang at the origin of the universe.
A third important solution for the Field Equations was developed for
rotating massive objects, including black holes, by New Zealand mathematician, Roy Kerr, in 1963. His work inspired a flurry of activity on the physics
of black holes by Stephen Hawking, and others. One of the unusual effects
arising from Kerr’s solution is frame-dragging. Objects in the vicinity of a
rotating black hole become caught up in the rotation because of the curvature of space–time that the rotation generates. At close enough distances, even
light itself must rotate with the black hole.
As we have already remarked, exact solutions of the Field Equations are
hard to find. However, even in classical physics, not all problems that appear
on the surface to be simple, can be solved precisely. The three-body gravitational problem, where the earth, sun and moon interact with each other, is
7 Optimism is the faith that leads to achievement. Nothing can be done without hope and confidence:
Helen Keller.
R. Barrett and P. P. Delsanto
The very natures of time and space become intermingled here, as in the plot
of a far-fetched science fiction movie. However, as we shall see later in this
Chapter, black holes have been detected by astronomers, and are now an
accepted consequence of the theory of General Relativity.
The possibility of creating a mini black hole on earth in an accelerator, such
as the Large Hadron Collider in Geneva, has been raised, with some concern
that it might escape and devour the earth. At first it was thought that the
accelerator had insufficient energy for black hole production. More recent
work shows that such an event is a real possibility. Luckily the calculations
indicate that such tiny black holes would pose no danger, since they would
soon shrink and disappear before being able to gobble up any matter [4, 5].
The second solution of the Field Equations that we wish to consider here is
the one for a homogeneous, isotropic universe. This is just physicists’ jargon
for a universe that is not “lumpy”, and looks the same in all directions. One
might well argue that our universe, comprising, as it does, stars, galaxies of
stars and clusters of galaxies, is indeed “lumpy”. From our perspective here on
earth, it most certainly is. However, by moving far enough away and taking
a big picture, these inhomogeneities merge into each other in the same way
that the pixels on a TV screen merge together, unless one sits too close. They
should not affect the results of the model too much. 7
Solutions for this model of the universe were developed independently by
Alexander Friedmann, Georges Lemaître, Howard P. Robertson and Arthur
Geoffrey Walker in the 1920s and 1930s. The model is generally known,
rather unimaginatively, as the FLRW model, and is discussed in detail later
in Chap. 10. One of its characteristics is the presence of a singularity which
is identified with the big bang at the origin of the universe.
A third important solution for the Field Equations was developed for
rotating massive objects, including black holes, by New Zealand mathematician, Roy Kerr, in 1963. His work inspired a flurry of activity on the physics
of black holes by Stephen Hawking, and others. One of the unusual effects
arising from Kerr’s solution is frame-dragging. Objects in the vicinity of a
rotating black hole become caught up in the rotation because of the curvature of space–time that the rotation generates. At close enough distances, even
light itself must rotate with the black hole.
As we have already remarked, exact solutions of the Field Equations are
hard to find. However, even in classical physics, not all problems that appear
on the surface to be simple, can be solved precisely. The three-body gravitational problem, where the earth, sun and moon interact with each other, is
7 Optimism is the faith that leads to achievement. Nothing can be done without hope and confidence:
Helen Keller.