In Terry Pratchett's book "Going Postal" he writes about the impact on the Discworld civilization of the semaphore tower. A new - but relatively basic - technology which revolutionises how people work, play, and interact. It changes the fortunes of the humble and the mighty. It is as useful for individuals as for nation states.

In our universe, the modern semaphore tower was first conceived by Robert Hooke in 1684. Yet it the optical telegraph didn't really exist until 1792 - over a hundred years later.

The basics of the optical telegraph are relatively simple. You stand in a tower and perform an action which can be seen by a person in another tower. That action is translated into a message, which can then be routed to another tower until it reaches its intended recipient.

What I find interesting is that there was nothing fundamentally to stop the Romans - or any other ancient civilization - from creating such a network. The Greeks experimented with it in 4BCE but it seems it never really caught on. Tower building is easy, as is flag waving or other mechanical forms of signalling. Their technology was certainly capable of building a proto-Internet. That would have had some profound changes to our history.

Rapid communication leads us to some interesting mathematical problems - namely encryption and compression. You want to make sure your message is secure from eavesdropping (including by the operators) and you want to send the message quickly. As a network becomes complex, you need to develop a routing protocol - explaining where the message has come from and where it needs to go. You need algorithms to determine the optimal path through a system.

Social changes come too. In Tom Standage's The Victorian Internet he talks about how the telegraph system disrupted commerce and society. The Victorian Internet was used to commit crimes, distribute suppressed information, manipulate markets, and to corrupt the youth. Not so very different from our own Internet!

Imagine what the world would be like if we'd had a 2,000 year head start on the principles of the Internet? Every day we see the efficiencies which a reliable communication network brings. Our knowledge of mathematics increases as we struggle to squeeze more information into limited channels. While rapid communication hasn't averted war - it has helped nation speak unto nation.

Consider the lonely alchemist who had to wait years to receive replies from far off lands - how much more quickly would science have progressed if people could instantly communicate their discoveries to an audience of their peers?

If the Romans had built a practical semaphore, not only would we all be speaking Latin, but our society would be a great deal more advanced. So why didn't they?

The main limiting factor, I think, is the lack of a decent telescope. Without the ability to see over great distances, communication towers have to be located relatively close to one another. That makes them more expensive - especially when a good horse can carry a message over a similar distance.

This is the story of technology in a nutshell. An amazing advancement is just beyond our grasp due to a minor inconvenience. A start-up fails because horses are cheaper and more reliable now. When Pheidippides can run 240Km in two days - why bother with the great expense of building towers and paying soldiers to staff them?

The future course of humanity delayed for want of a lens.

I'm sure history is littered with such examples. I'm not talking about the spurious claims of Ancient Egyptian flying saucers - or even strange artefacts like the Baghdad Battery. Electricity, it seems, was discovered and lost several times. In modern times, we saw the rise of powerful encryption techniques at Bletchley park - these were then suppressed by the UK Government and "lost" - they were then "invented" many years later by American mathematicians.

It is natural for people of the twentieth century to assume that our existing body of knowledge contains all the facts and processes which were within the ken of earlier men, plus the infinitely rich new content of modern science. A corollary of this assumption is that the prodigious enrichment of knowledge by the scientific research of the past three centuries-that is, since the time of Gilbert, Galileo, Harvey, and others-makes that part of knowledge which was attained by all preceding generations pale into insignificance.

But in truth both the assumption and its corollary are unwarranted. In the light of archaeology we can not doubt that the ancients knew a good many valuable and highly significant facts which nobody knows to-day. It goes without saying that the amount of this lost knowledge is beyond any one's power to estimate...

The Logical Significance of Rediscovered Knowledge
Daniel Sommer Robinson
The Journal of Philosophy
Vol. 22, No. 13 (Jun. 18, 1925), pp. 346-353

What are we missing now? What tiny changes would divert our destiny? It's hard to discover what we don't know we don't know, but there are a few that strike me as tantalizingly close. Some are mathematical, some technological, and some merely economical.

• Public Key Trust. The way we deal with trust in the PKI sphere is broken. Is there a simple way to verify the identity of a public key?
• Rapid and free transfer of money. At the moment, it's impossible to transfer a solitary cent commercially without incurring a prohibitive cost. What does the Internet look like when it's trivial to throw tuppence at a blogger?
• Waste energy capture. Humans pump out a lot of energy, we generate heat and movement which dissapates into the environment. A kinetic watch will run for as long as its owner keeps moving - can we use that energy to power something more complex?
• Self healing materials. Stronger material - like the lost Damascus Steel would be nice - but why can't our object grow and heal?
• Cold Fusion. Or, at least, a way to generate power in such a way that energy security is no longer an issue.

I would love to believe that there is an old untranslated manuscript which teaches us the secrets of anti-gravity or telepathic communication. What I think is more likely is that we'll discover just how close humanity came to a major technological breakthrough - only to have lost our way.

I look back on the Romans and wonder what the world would now look like had they persevered with their ancient Internet. I'm sure the future will look back at us and whisper "if only..."

In Terry Pratchett's book "Going Postal" he writes about the impact on the Discworld civilization of the semaphore tower. A new - but relatively basic - technology which revolutionises how...