M.-A. Lemburg
2^64 = 18446744073709551616, which is roughly 10 ^ 22. Let's assume a memory density, of, say 2^20 machine words or roughly 8 megabytes per cubic centimeter (much, *much* better than we'll be able to do for the forseeable future -- remember power distribution and heat dissipation).
Where did you get those numbers from ? There are memory sticks with 128 MB around and these measure about 2.5 cm^2 * 1 mm.
Remember power distribution and heat dissipation. You can't just figure volume of the memory ICs, you have to include power and cooling and structural support too. I eyeballed some DRAM modules I had lying around. In any case, my figures aren't that sensitive to memory density. If I'm off by a factor of 64 the diameter of the memory sphere unly drops by a factor of four (it's that cube-root relationship between volume and radius). So it's only half the radius of the Sun. That's still way, *way* more mass than all the planets in the Solar System put together.
Just you wait... someday marketing people will probably invent the world memory facility and start assigning a few hundred Terabytes for everyone on this planet to use for his/her data storage -- store once, use everywhere ;-)
Let's assume we have 12e9 people on this planet by that time, then we'll need 12e9*100e12 = 1.2e24 bytes of central storage... or roughly 2^80 bytes per civilization.
Nah. Individual storage requirements would never get that large. Bill Joy did a study on this once and figured out that human beings can generate about 14GB of text during their lifetimes, max. In a system like the Web-on-steroids one you're supposing, higher-volume stuff like streaming video or Linux-kernel archives would be stored *once* with URLs pointing at them from peoples' individual stores. One terabyte (2^40) per person leaves plenty of headroom (two orders of magnitude larger). We could still handle a world population of 2^24 or roughly 16 billion people. (I think the size of the Library of Congress has been estimated at several thousand terabytes.) -- <a href="http://www.tuxedo.org/~esr/">Eric S. Raymond</a> I don't like the idea that the police department seems bent on keeping a pool of unarmed victims available for the predations of the criminal class. -- David Mohler, 1989, on being denied a carry permit in NYC