Anachronism literally means 'out of time'. It can be any object or event that appears out of place because it isn't appropriate for the time. If you see an Eminem poster in a film about wartime France, then you're experiencing an anachronism. The Eminem poster is an object from the future, compared to the setting of wartime France. It might be described as a regressive anachronism.

Similarly, if you wandered into Marks and Spencer and saw their Autumn Range consisted of saber-toothed tiger-skin loincloths, they would also be anachronisms, as well as incurring the wrath of the anti-fur lobby. The tiger skins are objects from the past, compared to the setting of present day M&S. They might be described as progressive anachronisms.

Time Travel

Many people have toyed with the concept of time travel and the paradoxes it presents. Time travel throws up many difficult questions: What would happen if you went back in time and killed your grandfather as a child? Where does fate fit into all this? What does it mean to have an effect without a cause? Some of these concerns can be resolved by looking to parallel universe theories or other bold new perceptions of reality, but these, in turn, spawn questions of their own. People like to play with the big picture.

Physicists tell us that while it may be possible to move forward through wrinkles in time, it may not be possible to move back. This is arguably the same thing as saying that they just don't know. Despite the dubious science, and despite (or possibly because of) the questions above, there are books, films and TV programmes galore which play with the spirals, circles and paradoxes of subverting causality by going into the past or future. These stories often include anachronisms, and the chance for actors to dress up in amusing period costume.

This Entry deals with just one of the questions of time travel: If it is possible to travel in time, why isn't there any historical evidence? This is a good question. What time traveller could resist the temptation to walk the streets of ancient Athens? What future historian would pass up the opportunity of a field trip to the Renaissance? The basis of this argument is that 'there are no anachronisms, so there never will be any travellers with time machines'.

Breadcrumb Trails and Hidden Clues

This is an argument which cuts both ways: other people take a look at history and cause and effect, and find things which appear not to have happened in a sensible chronological order. Could these anachronisms be proof that time travellers from the future have already affected our history? Some subscribers, particularly science-fiction and fantasy writers, take this further. They suggest that time travel is possible, but since there are so few anachronisms they postulate a 'Time Police'. This band of people are supposedly dedicated to correcting errors and eddies in the space time continuum, returning history to its 'pure' path as if it had not been tampered with.

Both progressive and regressive anachronisms could be the result of time travel, but regressive anachronisms tend to be much stronger proof. If, say, dinosaurs are found on a remote Pacific island, that could be the result of time travel. But it could equally be that this particular island has somehow been sheltered from whatever wiped out the rest of the dinosaurs. By contrast, if Julius Caesar is caught on film in ancient Rome wearing a pair of Levi's, that could only be a result of time travel (on two counts).

Other Explanations

So, there might be a scarcity of anachronisms either because of Time Police, or because time travel is impossible. However, there are other (less dramatic) explanations:

• Time travel may be very difficult. This would make anachronisms either very rare or non-existent. It might also limit time travel to larger organisations which would be more responsible in their uses of the technology.

• The human species may become extinct shortly after the invention of time travel, so there won't be enough time¹ to flood the past with tourists. Maybe time travel is itself a dangerous technology?

• It may not be possible to travel back in time past the creation of some specific artefact. The Tippler Method is an example of a method with this kind of limitation. In this case we'd expect to see no time travellers now, but as soon as the relevant artefact is constructed we'd expect visitors from the future to be a fact of life.

Example Anachronisms

• If the pyramids were not built by aliens, must they have been built with technology from a future civiliation? They are certainly impressive monuments in both scale and design, but then again the Egyptians were skilled masons with an almost infinite supply of labour.

• What about other feats of ancient engineering? From the solar calendar that is Stonehenge to the statues of Easter Island, there are a number of ancient monuments that have raised eyebrows over their feasibility given the technology and government of the time. Did their builders get a helping hand?

• How could Leonardo da Vinci have imagined the helicopter, centuries before it first took off? But Leonardo's helicopter could not in fact fly, and wasn't a proper helicopter anyway. Leonardo also had some tank designs: another temporal anomaly? And what was it that really sent Leonardo mad?

• How come the Greeks had a clocklike computer over 2000 years before clockwork's 'natural' development in the 18th Century, in the shape of the Antikythera Mechanism (perhaps the Time Police ensured that the secret of clockwork was hidden for long enough for technology to catch up)? After all, the last mechanism went down in a ship wrecked in the Mediterranean.

• A more fanciful suggestion is that the fabled island of Atlantis was one giant anachronism and was drowned in an attempt to hide this 'fact'.

Some people argue that these examples and others show that there have been careless time travellers and show that Temporal Secret Agents have been here on containment and damage limitation missions. These are said to be the smoking guns of the ultimate conspiracy theory.