Intelligence helps Universes Reproduce…

K-State math professor looking to mathematical theories for clues on origins and future of life in the universe; Suggests artificial black holes play a big part.

Louis Crane has been working on an extension of Lee Smolin’s suggestion that black-holes are the birthing events of Universes, and Universes are “fine-tuned” to enhance that reproduction via a Cosmic Selection process. The above news-bite and link is a more recent piece, but here’s two more…

Building a Better Black-Hole (October 2007)

Ad Astra Kansas News (Fall 2006)

…all saying much of the same thing: Intelligent Life will learn to make black-holes for interstellar travel, and thus ‘mid-wife’ the creation of Universes (if Smolin & Crane are right.)

But what good is a black-hole? Actually it’s an incredibly efficient way of turning mass into energy. So long as you do it the right way. So what’s the wrong way? Accretion, but for an interesting reason.

Arthur C. Clarke used a black-hole as the heart of his fictional “Asymptotic Drive” in his 1975 novel, Imperial Earth. An accreting black-hole can convert 5% of the rest-mass energy of infalling matter. Thus it’s capable of an exhaust velocity of 0.33 c, which it uses to good effect doing a continuous boost between Saturn and Earth at 0.2 gee. Black-holes have also appeared as fictional power-sources in all sorts of odd places, including “Star Trek”. Black-holes can also store energy as rotational energy, controlled by giving the hole a large electromagnetic charge and subjecting them to a rotating field. Charles Sheffield uses them like so in his “McAndrews Chronicles”.

A question is: just how mass-efficient is energy release via black-hole accretion? A limiting process for all accreting systems is the Eddington Limit, which is when radiation pressure is sufficient to blow away infalling matter from an object. Plugging in the usual numbers that means the energy output is about 6.4 W/kg of black-hole… worse than an RTG! Not a starship drive. But some accreting systems can be above that Limit via ‘dirty tricks’ i.e. opacity effects.

Consider the Sun. It puts out about 4E+26 joules per second. And it masses 2E+30 kilograms. That’s a power-to-mass ratio of just 0.0002 watts per kilogram – far less than a battery. A bit higher if we factor in the fraction of the Sun that actually produces power (0.08) thus 0.0025 watts per kilogram. Not much better. We’re used to hearing about quasars, which are powered by black-hole accretion, having power outputs of a 100 galaxies or so. How much is that? A galaxy, like our Milky Way, shines with a light of about 30 billion Suns. Thus a quasar putting out 100 Galaxies of power is shining with about 3 trillion Suns of light. How big a black-hole is needed? At 6.4 watts per kilogram at the Eddington limit it’s massing ~100 million Suns. That’s big, but consider the monster at the heart of M87, recently measured at 6.4 BILLION solar masses.

Yet all with a piddling 6.4 watt per kilogram power-output.

Not the way to power a starship. However black-holes also turn their mass into energy via Hawking Radiation and that’s a bit more power dense – with a caveat. Old school semi-Classical quantum mechanics applied to General Relativity means a black-hole drags virtual particles out of the vacuum, making them real. In doing so it loses energy/mass. A black-hole is a very simple astrophysical object, defined by its mass, spin and charge and its ‘size’ is really the size of the Event Horizon it wraps around itself. The size of the horizon determines the temperature of the Hawking Radiation that it radiates as well as how much energy it then radiates over its whole Event Horizon area – but the two are at odds i.e. the inverse of the radius determines temperature, while the radius to the 2nd power is the area. Thus once you do the sums the black-hole gets brighter to the inverse of the 2nd power of the radius, and thus the mass (Rs = 2GM/c2.) The energy is being radiated away so quickly for lower masses that the last 228 tons of mass-energy is radiated away in the last second! That’s an explosion of 4.9 million megatons of TNT equivalent energy as very hard gamma-rays.

A heftier hole, about 1 million tons, radiates at about 356,200 W/kg – better than any current power-plant. But for a really high performance starship we want megawatts per kg. A hole massing 100,000 tons is putting out 356.2 MW/kg… except it’s mostly as hard gamma-rays. A gamma-ray reflecting material would be a big plus.

Back to Louis Crane’s work. He’s using a quantum gravity theory to analyse the behaviour of black holes at such extremes, so the figures I quote will be different to what his analysis derives. Hopefully he’ll figure out the gamma-ray problem for us too 🙂