Cosmic Censorship and Your Non-Existent Grandfather

The weak cosmic censorship hypothesis states something to the effect that we are insulated from the effects of the breakdown of our scientific theory's ability to predict events.  Where events are in (scientific) principle unpredictable, they are locally confined so that they can have no effect upon us whatsoever.  The hypothesis is weak because it permits such confined local breakdowns of predictability to occur at any time.  The strong cosmic censorship hypothesis states that such unpredictable - though utterly isolated - events can only occur at the beginning and end of time.  See this post (and you might note the circularity) for what it means, in science, to say that time has a beginning and an end.

Regarding the cosmic censorship hypothesis, my second favorite Lucasian Professor of Mathematics has some very funny (and equally ridiculous) stuff to say.  Here at Scottish Nous we don't like censorship, cosmic or otherwise, but Hawking argues that we should root for it.  To wit, he expresses his hope that either strong or weak cosmic censorship holds because, due to the possibility of time travel near naked singularities, someone could murder your great-great-grandfather if they survived a close approach to an unclothed object of infinite density.  Let's hear him on the matter:

It is greatly to be hoped that some version of the censorship hypothesis holds because close to naked singularities it may be possible to travel into the past.  While this would be fine for writer's of science fiction, it would mean that no one's life would ever be safe: someone might go into the past and kill your father or mother before you were conceived! -Hawking, A Brief History of Time

That is truly terrifying (mostly just because the infinitely dense should keep their clothes on).  So the idea is this:  I should hope for cosmic censorship so I don't have to avoid personally instantiating, as a victim, the grandfather paradox.  Only if the cosmos violates certain event's rights to free expression can I be saved from the dreadful prospect of something travelling back in time to kill my ancestors!  How about this instead: the events described by the grandfather paradox are logically impossible!  Then, since it is not possible to travel back in time, I don't have to worry about someone presently altering the past.  Whew.  Big sigh of relief.  I suppose that now I should be ambivalent with respect to cosmic censorship.  (N.B. Science fictions writers do not care whether or not time travel is logically possible.)  Finally, what the hell is a naked singularity?

Eddington thought it was simply not possible that a star could collapse to a point.  This was the view of most scientists:  Einstein himself wrote a paper in which he claimed that stars would not shrink to zero size. -Hawking, Op. cit.

Good for Einstein and Eddington.  It doesn't seem at all reasonble to suppose that you could line up, next to one another, infintely many naked singularities of infinite density (ignoring the alleged gravitational effects of point-"sized" objects) and there still not be some distance between any two of them.  The problem is not the naked singularity.  After all, if it were possible to line up infinitely many naked singularities in the manner described, then a naked singularity would just be a point.  But points do not have infinite density.  In fact, points do not have a density.  Points do not possess gravitational fields, nor float in a liquids with higher specific gravities.  I believe the appropriate response to talk of the specific gravity of a point involves the two words "category error" - although "$%@*   )!!&#(@" might be included for ad hominem emphasis.  Physics, like philosophy, has gone off the deep end.

Comments

[Scott Hagaman]

Ok, so perhaps the more general point is that, if weak or strong cosmic censorship doesn't hold, then almost anything could happen. If nothing contains or restricts the range of effect of the in principle unpredictable events, all manner of disorder could arise. And this is enough to be really, really bad for our scientific theories. Something like this is what Hawking *should* have said.

[Tapas Bhattacharyya]

If time reversal occurs,These are some variables of classical physics would have no effect and have effects.

Classical variables which do not change upon time reversal include:

the position of a particle in three-space
the acceleration of the particle
the force on the particle
the energy of the particle
the electric potential (voltage)
the electric field
the electric displacement
the density of electric charge
the electric polarization
the Energy density of the electromagnetic field
the Maxwell stress tensor
All masses, charges, coupling constants, and other physical constants, except those associated with the weak force

Classical variables which are negated(shall be effected)by time reversal include:

the time when an event occurs
the velocity of a particle
the linear momentum of a particle
the angular momentum of a particle (both orbital and spin)
the electromagnetic vector potential
the magnetic induction
the magnetic field
the density of electric current
the magnetization
the Poynting vector
the Power (rate of work done)

But I dont care!!!