Re: A Sad Asimov fan

Keith Thompson <kst-u@xxxxxxx> wrote:
> The problem with a proton decaying into a positron and a photon is
> that it violates the conservation of baryon number and of lepton
> number. But those conservation laws aren't absolute; for example,
> black hole evaporation can also violate them.

That's unproven. Very little is known about black holes. In fact,
it's still (barely) possible to reasonably doubt their very existence.

But it is worth keeping in mind that the only reason we think that
baryon number and lepton number are conserved is that we've never seen
them *not* conserved. And there is precedent, sort of. There's a law
of conservation of strangeness, but it only operates on a nanosecond
timescale. If you watch your strange particles for a full microsecond,
you'll see that strangeness can be created and destryoed. This
conservation law was originated to "explain" why strange particles
lasted much longer than expected. Most particles last less than a
billionth of a nanosecond, after all. When one hangs around for a
whole nanosecond, that's all but absolutely permanent.

Maybe baryon number and lepton number are the same, except that
instead of a nanosecond timescale, they operate over a trillion
trillion trillion eon timescale.

The same could be true of even more beloved conservation laws, such
as momentum, mass-energy, and charge.

> (The only quantities conserved when a black hole forms are
> mass-energy, spin, and charge.)

Unproven.

> So if a random quantum gravitational fluctuation happens to form a
> short-lived black hole, and a proton happens to fall into it before
> it decays, that should do the trick. This is staggeringly unlikely
> to happen; thus the long half-life.

Yes and no. That would give a finite half-life, but the currently
popular supersymmetry theories give an enormously shorter proton
half-life, though one that's still staggeringly long in human terms.
Or even in geological terms.

> Much of this information is probably several years out of date;
> in particular, I think there have been some recent theoretical
> developments involving black holes that I'm not sufficiently
> familiar with.

It's all angels and pinheads until someone gets ahold of an actual
quantum black hole. You reach one conclusion if you push general
relativity a few dozen orders of magnitude beyond the experimental
evidence, and a quite different conclusion if you push quantum
mechanics a few dozen orders of magnitude beyond the experimental
evidence. They don't meet in the middle. Nobody knows where
the truth lies. Curled up higher dimensions? M-branes? Maybe.
Maybe something even weirder, that nobody has thought of yet.
--
Keith F. Lynch - http://keithlynch.net/
Please see http://keithlynch.net/email.html before emailing me.
.

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