Predeterminism in Relativity

A lovely example of how predeterminism actually lurks within Relativity, taken from Kip Thorne's "Black Holes and Time Warps", Papermac, ISBN 0-333-63969-3, Chapter 12, "Black Holes Evaporate". It is strange how Thorne drops his bombshell, recognises the philosophical implications, and then continues with his story without a word about the consequences for human subjective experience.

[Penrose and Israel] especially could not conceive of jettisoning [the apparent horizon] in favor of the absolute horizon. Why? Because the absolute horizon - paradoxically it might seem - violates our cherished notion that an effect should not precede its cause. When matter falls into a black hole, the absolute horizon starts to grow ("effect") before the matter reaches it ("cause"). The horizon grows in anticipation that the matter will soon be swallowed and will increase the hole's gravitational pull.

Penrose and Israel knew the origin of this seeming paradox. The very definition of the absolute horizon depends on what will happen in the future: on whether or not signals will ultimately escape to the distant Universe. In the terminology of philosophers, it is a teleological definition (a definition that relies on "final causes"), and it forces the horizon's evolution to be teleological. Since teleological viewpoints have rarely if ever been useful in modern physics, Penrose and Israel were dubious about the merits of the absolute horizon.

Hawking is a bold thinker. He is far more willing that most physicists to take off in radical new directions, if those directions "smell" right. The absolute horizon smelled right to him, so despite its radical nature, he embraced it, and his embrace paid off. Within a few months, Hawking and James Hartle were able to derive, from Einstein's General Relativity laws, a set of elegant equations that describe how the absolute horizon continuously and smoothly expands and changes its shape, in anticipation of swallowing infalling debris or gravitational waves, or in anticipation of being pulled on by the gravity of other bodies.

In November 1970 Stephen Hawking was just beginning to reach full stride as a physicist [...]

Without wishing to over-egg it, also notice how the "gravitational waves" here - things that propagate at lightspeed and need fancy "corrections" to make them come out like Newton's instantaneous gravity - are now travelling backwards in time, but only providing they are going to intersect a black hole!