Future of Computation Is Finite

By Roland Piquepaille

According to PhysicsWeb, two cosmologists from Case Western Reserve University have shown that the acceleration of the expansion of our universe leads to physical limits on the total amount of information that can be stored and processed in the future. They also determined a time limit for Moore's law which will still be valid for the next 600 years. Finally, they calculated that the total number of computer bits that could be processed in the future will not exceed the 10¹²⁰ range. In a previous story, "Universe is a computer," another physicist estimated that the number of calculations the Universe would have performed since the Big Bang -- if it was a computer -- and also came with a10¹²⁰ number. I'm not sure if both studies are speaking about the same exact things. But if they are, does this mean that we are exactly at the midlife point of our Universe?

The acceleration of the expansion of the universe places limits on future developments in technology according to two US cosmologists. Lawrence Krauss and Glenn Starkman of Case Western Reserve University have shown that the acceleration could put a fundamental limit on the total amout of information that can be stored and processed in the future. They also calculate that Moore's Law will remain valid for no more than 600 years -- although workers in the semiconductor industry are more pessimistic and think that the famous law will break down in the next decade or two.

They also found other physical limitations.

The duo calculated that the total number of computer bits that could be processed in the future would be less than 1.35¹²⁰. This means that the effective information available to any observer within the event horizon of an expanding universe will be significantly less than the total so-called Hawking-Beckenstein entropy -- the entropy that is associated with a black hole -- in the universe. Many cosmologists predict that an accelerating universe will ultimately contain nothing but black holes, which will then eventually disappear themselves.

Right or wrong, the physicists seem to enjoy their work.

"It is remarkable that results from cosmology can provide such definite limits on the nature of technology," Krauss told PhysicsWeb. "In addition, it is also remarkable that simple laws of physics put such robust constraints on life, and technology, even when we don't know what that technology will be like."

For more information, the research paper has been published by ArXiv in its astrophysics section under the name "Universal Limits on Computation" on April 26, 2004. Here are the links to the abstract and to the full text (PDF format, 3 pages, 89 KB).

And as I wrote above, you can read a previous story, "Universe is a computer," about a theory from Seth Lloyd, a physicist at the Massachusetts Institute of Technology in Cambridge, who estimated how many calculations the Universe would have performed since the Big Bang -- if it was a computer.

To simulate the Universe in every detail since time began, the computer would have to have 10⁹⁰ bits and it would have to perform 10¹²⁰ manipulations of those bits. Unfortunately there are probably only around 10⁸⁰ elementary particles in the Universe.

I think it's time to stop here before getting a headache. This kind of science is going slightly above my head.

Source: Belle Dumé, PhysicsWeb, May 7, 2004; and various websites