# The next big thing: the universe as a computer

A casual conversation with one of my neighbors, Edwin Taylor, who has taught mechanical engineering at MIT for many years, recently led me to a quite startling book by one of his younger colleagues, Seth Lloyd.

A casual conversation with one of my neighbors, Edwin Taylor, who has taught mechanical engineering at MIT for many years, recently led me to a quite startling book by one of his younger colleagues, Seth Lloyd. The book is “Programming the Universe: a Quantum Computer Scientist Takes on the Cosmos,” (Knopf, New York, NY). In his just-published book, Professor Lloyd poses a “really big question”-“Is the universe really a very big computer and can it be programmed?”

That’s actually a two-part question, of course, and Lloyd appears to feel strongly that the answer to both parts is “yes!” He may be right. In little more than a couple of hundred densely written pages, Lloyd makes a convincing case for the universe as a computer but he has not yet reached a definitive position on the latter half of his big question, in my view. When and if he does, there may be a Nobel Prize in the offing, I suspect.

However, Lloyd is definitely not some Johnny-come-lately computer nerd. Check out his extensive 20-page curriculum vitae on his personal web site (www-me.mit.edu/people/personal/slloyd.htm). And he is undeniably well versed in theoretical physics, despite some youthful flippancy here and there. “Nothing is certain in life except death, taxes, and the second law of thermodynamics,” says Lloyd, his tongue firmly in his cheek. Indeed, starting with the concept of entropy, Lloyd makes a comprehensible case for the universe as a computer without having to revert to complex math. Thank goodness for that!

Entropy has never been easy to understand, except in an intuitive way. For example, when our bathwater cools down, it’s fairly easy to comprehend that entropy increases as the heat dissipates into the cooler atmosphere. That’s clear enough, but just where does entropy come from? And must entropy always increase? Is Maxwell’s Demon possible theoretically or otherwise? Lloyd attempts to answer these questions in the language of the informed layman, mostly with some success.

Lloyd then draws some parallels with the physical world as we know it today. The first law of thermodynamics relates to the conservation of energy when it is transformed from mechanical energy into heat. This conservation can be easily observed empirically or calculated with some reasonable degree of precision and repeatability. The second law of thermodynamics, says Lloyd, is more of a statement about information and how it is processed at the microscopic scale.

In the language of the quantum computer scientist, each physical system contains a certain number of bits of information that are never decreased by the processing and transforming that goes on. In fact, claims Lloyd, the view of the universe as a computer can explain why the second law of thermodynamics is true, something that scientists have struggled over for more than a century and a half.

Lloyd even manages to develop his concept of a computing universe sufficiently to put some numbers on the “ultimate laptop” (a computer with a mass of one kilogram and a volume of one liter where every elementary particle would be put to computational use). Such a laptop would be able to perform ten million billion billion billion billion billion operations per second on ten thousand billion billion billion bits. Phew!

And if you think those are really big numbers, wait until you read Lloyd’s take on the computational power of the universe. How about claiming, as Lloyd brazenly does, that, since its beginning, the universe may have performed 10122 operations on 1092 bits. A billion here and a billion there and soon we’re talking really, really big numbers! As Lloyd further claims, “The information-processing power of the universe grows steadily with time. The future looks rosy.”

I hope you are serious, Mr. Lloyd.

Jeffrey Bairstow

Contributing Editor

jnbairstow@verizon.net