When you last used a mobile phone to access any kind of data (you may even be using one now), how was your experience? Could you read your email without any glitches? Was your web browsing experience fuss-free? Did an app tell you what you needed to know about where you were, or where you wanted to be? And how was BBM – did your colleague's snippet of information turn out to be useful?
The chances are that any of these applications actually worked, and worked properly. In fact, when you consider the atmospheric conditions that they may have gone through – walking in cities covered in tall buildings, or working on a train, or in a spot of poor mobile coverage – then it's a minor miracle that right and meaningful data got through at all.
This is because digital communications rely on error correction. Whether it regards a mobile phone or a space probe, there is reliance on the part of both the sender and receiver, that the information has to be right and delivered as it was intended. In the case of both, there is liable to be some interference on the signal, so what is received is not necessarily what was sent. Correcting the problem is undertaken by adding extra information before the signal is transmitted.
Many of us know a little bit of how this works, with the tried-and-tested formula of the Parity Check. The binary transmission is split into chunks of seven. Before the signal is transmitted at the end of each group of 7, an additional bit is added in such a way that the total number of 1s in the new chunk of 8 is an even number. When the signal arrives, if there is an even number of 1s in the group of 8 then it looks to be more acceptable – more likely of being right – than if the number of 0s is an odd number. This makes the process of spotting mistakes fairly easy to automate, in a way that most of us now don't even see.