Re: Not quite magic physics [was Re: Quantum Computers]

Eugene Leitl (
Mon, 23 Aug 1999 01:01:07 -0700 (PDT)

Doug Jones writes:

> Not protons, photons- 1 AU is 150E6 km = 1.5E11 m, sunlight is 1350 W/m2 at

Not photons, protons. Solar wind is mostly speeding protons and a bit of helium nuclei (this is exerting pressure on NASAs new wonderdog magnetic plasma sail propulsion technology). I thought the 2 Mt/s figure relies to total Sun mass loss, and solar wind should contribute the bulk of loss by mass.

> earth, so total power out = 4piR^2(1350) = 3.8E26 W. E=MC^2, so
> P = MdotC^2 and Mdot = P/C^2 = 4.2E9 kg/s = 4.2 MT/s

Ok, so the energy in question *was* referring to the photonic output. With current technology can count on trapping maximally ~30% of the 1.3 kW/m^2. Assuming a FEL efficiency of (very good) %50...

> Four million tonnes of energy per second is one hell of a lot of power.

Relatively. Unfortunately it is not a lot of energy to effect a lot of spacetime curvature if we consider that it must be focused. It is roughly two-three orders of magnitude off a usable microsingularity size I believe.

> Current total human power usage is around 10 terawatts, give or take an
> order of magnitude... or about 0.01 g/s.
> Total insolation on Earth is about 1.7E17 W, or about 1.9 kg/s.
> Four million tonnes of energy per second is one HELL of a lot of power.
> With a really *big* chirped diffraction grating (tens of lightseconds on a
> side) you could create attosecond pulses with megatonne mass. Colliding

If we can do structures that large, a circumsolar proton/antiproton twin accelerator ring might be a better investment. Here you can be sure to achieve lots of energy density without all the nasty opaque vacuum radiative losses. Would make awfully small holes, though.

> these pulses[*] should create tidy little black holes. It may require
> hundreds or thousands of seconds of the sun's output to make black holes
> that have evaporative lifetimes of at least a few years, so that they can

That's a bit too brief. You need to feed a hole, and you can't feed a hole that small radiating that furiously (apart from letting it fall into a star, letting a large sphere of osmium falling on it is probably about as efficient as it gets). It is much too blue to be used for anything anyway. It would fry anything. Before it drowns in quantum foam you'd get luminosity several times of the Sun (assuming we trapped 1-10 s of total Solar output in the hole) in ultrahard gamma dissipated somewhere in deep submicron volumes. This is not something I'd like to witness from somewhere closer than a good number of light minutes distance, and a lot of attenuating matter in between.

> be trapped and used. The energy in the beams must all reach the target
> volume in less time than it takes for a photon to traverse the "width" of
> the hole. Yoctosecond timing?

Can we count of a superciv being able to focus the entire solar output in a volume of a few cubic microns (or however it takes to make a hole), possibly the entire solar output of a few 10 seconds? Methinks there are very real physical limits at work here. Sufficiently advanced maybe, but real magic?

> About the best use of black holes is the fact that they don't conserve
> baryon number, so you can turn any old mass (even iron) into energy. The
> very high temperature of a black hole would allow very high carnot
> efficiency.

A purely theoretical result. Extremely blue radiation does not even attenuate well. It will just cut through everything, ultrahard gammas ripping massive swaths of destruction into anything they deign to interact with. One would want to keep the hole temperature somewhen below 200 MK, which allows the xRays to be relatively easy attenuated by a manageable layer of gas.

Once again, I think the chiefest problem of making holes with photon flux is avoiding the vacuum to become opaque by pumping virtual particle pairs into reality. Preparative creatio ex nihile is neat, but no hole.

> --
> Doug Jones, Freelance Rocket Plumber
> [*] to avoid the circular firing squad's dilemma, more than two beams are
> needed so that missed pulses don't fry the opposite launch optics. Four
> beams originating at the corners of a tetrahedron should work... but more
> would produce a smoother implosion. Asymmetries in the implosion will
> cause the resultant hole the shoot off in the opposite direction. Thus two
> beams meeting at right angles could create a hole shooting off at .7 c

For energy containment reasons alone it is very obvious one need to fire a very large amount of circumsolar units simultaneously into a very precise quadrant of space. Because of the distances involved one needs not fear to hit any opposite firing stations. The drift velocity of the resulting hole might be near zero. Oops, just don't let it fall back into the star. (Unless you want to experiment with a DIY GRB from *real close*, that is).