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Information about information

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We live in a golden age of information. Never has so much of it been available so easily to so many of us. Information is power, it's money and, given how much of our life is lived online, defines part of our reality.

But what exactly is information? We tend to think of it as human made, but since we're all a result of our DNA sequence, perhaps we should think of humans as being made of information. We like to think of it as abstract, but there's no information without physical manifestation, be it in the neurons in our brains, the pages of a book, or the electrical circuits in a computer. We like to think of it as floating on top of reality like a cork on an ocean, but insights from quantum physics suggest that reality might itself be made up of it. Perhaps we do live in a matrix after all.

In this project, brought to you in collaboration with FQXi, we'd like to take you on a journey through the fascinating world of information. But we'd like you to tell us what you'd like to know about information. To start you off we've chosen a few key questions philosophers, physicists and mathematicians are currently thinking about. There's a little background on each of them below, and a poll on the right in which you can choose your favourite one. At regular time periods we'll put the most popular question to the world's leading experts and come back to you with their answers. If you've got a question that's not on our list then please let us know by posting a comment below.

The question that won the first poll is "Can information be turned into energy?". Here is the answer, based on an interview with MIT physicist Seth Lloyd.

Is there a universal language of information?

When NASA launched the Pioneer spacecrafts in the 1970s it equipped them with plaques showing the nude figures of a man and a woman, a schematic representation of the solar system, as well as other drawings designed to impart information to aliens that might intercept the crafts. Whether or not alien life forms could actually make sense of these is debatable. Is it possible at all to develop a language that every intelligent being is sure to understand?

Are there fundamental laws of information processing?

It seems that computers double their processing power roughly every two years. So reliable is that rate of increase that it's got its own name: Moore's law, named after Gordon Moore, a co-founder of Intel. Of course, Moore's law is not a law in the same way as, say, Newton's laws of motion are. The latter are a features of reality, while Moore's law is just an accidental pattern in human made activity. Or is it? More generally, is information processing subject to fundamental laws that can't be broken? Are there ultimate limits on information storage and processing power? Could such laws be used to predict the future or figure out what super-advanced civilisations might be doing elsewhere in the galaxy?

Is the world made up of information?

It's tempting to think of information as something that describes the physical world around us. However, since the end of the nineteenth century we have known that that physical world is not as solid as it may seem. Tiny particles of matter, such as electrons, can be in several places at once, they behave like waves in some situations and like particles in others, and they can also exhibit a range of other properties we'd normally deem mutually exclusive. The reason why we never see this superposition happening is that as soon as we perform an experiment to measure, for example, where an electron is, this strange superposition of states seems to collapse to give just one definite outcome. We can't say with certainty which outcome that will be, although we can compute the probabilities that we'll observe a particular one (see this article for more information).

This is the central message, as well as riddle, of quantum mechanics. It suggests a new way of looking at reality: since what we actually experience depends on us observing the world (via our measuring devices), reality is shaped by answers to yes/no questions. For example, is the electron here or is it not? Is its spin pointing up or pointing down? Answers to questions are information — the yes and no in English language correspond to the 0 and 1 in computer language. Thus, information is fundamental to physical reality. As the famous physicist John Archibald Wheeler put it, the "It" we observe around us comes from the "Bit" that encodes information: "It from bit". Is this really true?

What is quantum information?

The conventional computer you're looking at right now works with bits: little units of information that can be either 0 or 1. In the murky world of quantum mechanics, however, information could be held in systems that are in superposition, taking several values simultaneously. How exactly do we define such quantum information? What are the rules that govern it? And what light does it shed on the power and scope of quantum computing?

Can information be destroyed?

What happens to a book when you burn it? For all practical purposes its content is lost to the world. In theory, though, it is possible to reconstruct the book from its ashes and smoke — it's not impossible for the burning process to be reversed, it's just highly unlikely. In that sense information is never lost. That's indeed one of the basic tenets of quantum mechanics. In the 1970s, however, Stephen Hawking and Jacob Bekenstein came up with an argument which suggested that information can be gobbled up by black holes. Their prediction split the physics community and led to the "black hole war" between Hawking and his colleagues. So what exactly is this black hole information paradox and can it be resolved?
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