Computronium universe – computation limits of computronium and limits to the universe

Ray Kurzweil discusses having a universe filled with Computronium.

He discusses this happening within 200 years if wormholes or some other means allow faster than light travel.

What would the computation limits of computronium be?

There are several physical and practical limits to the amount of computation or data storage that can be performed with a given amount of mass, volume, or energy:

* The Bekenstein bound limits the amount of information that can be stored within a spherical volume to the entropy of a black hole with the same surface area.
* Thermodynamics limit the data storage of a system based on its energy, number of particles and particle modes. In practice it is a stronger bound than Bekenstein bound.
* Landauer’s principle defines a lower theoretical limit for energy consumption: kT ln 2 joules consumed per irreversible state change, where k is the Boltzmann constant and T is the operating temperature of the computer * Reversible computing is not subject to this lower bound. T cannot, even in theory, be made lower than 3 kelvins, the approximate temperature of the cosmic microwave background radiation, without spending more energy on cooling than is saved in computation.
* Bremermann’s limit is the maximum computational speed of a self-contained system in the material universe, and is based on mass-energy versus quantum uncertainty constraints.
* The Margolus–Levitin theorem sets a bound on the maximum computational speed per unit of energy: 6 × 10 ³³ operations per second per joule. This bound, however, can be avoided if there is access to quantum memory. Computational algorithms can then be designed that require arbitrarily small amount of energy/time per one elementary computation step.

It is unclear what the computational limits are for quantum computers.

In The Singularity is Near, Ray Kurzweil cites the calculations of Seth Lloyd that a universal-scale computer is capable of 10 ⁹⁰ operations per second. This would likely be for the observable universe reachable at near light speed. The mass of the universe can be estimated at 3 × 10 ⁵² kilograms. If all matter in the universe was turned into a black hole it would have a lifetime of 2.8 × 10 ¹³⁹ seconds before evaporating due to Hawking radiation. During that lifetime such a universal-scale black hole computer would perform 2.8 × 10 ²²⁹ operations.

The universe itself is vastly bigger than the observable universe. If the speed of light is not a limit, then travel throughout the multiverse may also not be limited.

If faster than light is possible can we go to limits of this universe or the multiverse?

The limit on our observation universe is not the age of the universe and the speed of light which would be 13.799 billion light-years for two reasons.

This article is selected material from the Observable Universe entry in Wikipedia.

1. Space itself is expanding, so we can actually detect light from objects that were once close, but are now up to around 45.7 billion light-years away (rather than up to 13.799 billion light-years away as might be expected).

2. before the recombination epoch, about 378,000 years after the Big Bang, the Universe was filled with a plasma that was opaque to light, and photons were quickly re-absorbed by other particles, so we cannot see objects from before that time using light or any other electromagnetic radiation. Gravitational waves and neutrino background would have been unaffected by this, and may be detectable from earlier times.

There are at least 2 trillion galaxies in the observable universe, containing more stars than all the grains of sand on planet Earth. Assuming the Universe is isotropic, the distance to the edge of the observable universe is roughly the same in every direction. That is, the observable universe is a spherical volume (a ball) centered on the observer. Every location in the Universe has its own observable universe, which may or may not overlap with the one centered on Earth.

Alan Guth explains how eternal cosmic inflation explains the multiverse. Guth says that there is a lot of evidence for inflation. Also, the multiverse would explain the low number for the energy density of vaccuum.

Leonard Susskind explains that string theory proposes that there are 10⁵⁰⁰ kinds of universes. Not just 10 ⁵⁰⁰ universes but ⁵⁰⁰ possible kinds of universes.

Inflation results from repulsive gravity existing in the early universe.

A quantum computronium multiversal computer could have 10⁶⁰⁰ operations per second.