Re: Not quite magic physics [was Re: Quantum Computers]
Mon, 23 Aug 1999 08:58:17 -0700

According to the Hawking lifetime of a black hole is (M/M_sun)^3 * 10^66 years. M_sun (mass of the sun) is about 2x10^30 kg. So this sets black hole lifetime at (M in kg)^3 * 10^-25 years or about (M in kg)^3 * 3x10^-18 seconds.

To have a life time of, say, 3 seconds would require a mass of 10^6 kg, 1000 metric tons, which would be an energy of 10^23 Joules, which is a lot, something like 10,000 years of our total current energy usage.

The real problem though is to pack this energy into the required small size. Black hole radius is proportional to mass, a 1 kg black hole being about 10^-27 meters in radius, so the 10^6 kg would have to be packed into 10^-21 meters, much smaller than the nucleus of an atom.

Also, black hole temperature is inversely proportional to mass, and according to the web page about the 10^6 kg black hole would be about 10^17 K, which is hot hot hot (although coming from a tiny area.).