You've seen those time travel movies. Somebody goes back into the past and changes one thing, one 'contingency moment'. Two people meet – or don't meet. A boat doesn't sail. Somebody misses a train. . . Suddenly, the future looks a lot brighter. Or darker. . . Don't step on any butterflies.

You know the rules: you can't kill Hitler. Or Napoleon. Or Donald Trump. You can't go back and become your own father or mother, even if Douglas Adams did point out that 'There is no problem in becoming your own father or mother that a broad-minded and well-adjusted family can't cope with.'

What we want you to do is to change one thing about the past. Then figure out how the world would be different from the one we're living in. The one thing you changed could be:

• A migrational trend: What if nobody moved to America back in the 1600s, 1700s, 1800s? What if the Vikings had moved in and stayed? What if the Chinese had got there first?
• An invention: What if computers got there before telephones? Or cars? What if Europe had had better health care in the 14th Century?
• A social development: Gay rights in the Middle Ages? Witchcraft as an official religion?
• A plausible historical change: Lady Jane Grey stays queen, Wycliffe's followers take over the English church, the revolutions of 1848 actually succeed. The mind reels, and the imagination works overtime.
• Anything else you can think of. Would the world be a lot different if they'd had hula hoops at the Court of Versailles?

You can:

• Write an essay, poem, short story or carefully laid out rant. Send it to the Post.
• Draw us a picture, map, sketch. We'll publish anything original that doesn't violate international treaties.
• Photoshop your way to alternate paradise/some fresh hell.
• Write a Guide Entry. This novel suggestion comes at the urgent insistence of the Guide Editors. In this case, pick a real contingency event/invention/innovation/trend, etc. Tell us about it. Explain why it changed the world.

Put your links and announcements of 'It's in the gmail!' in the Submissions thread below. Don't put your entry itself in there, it just makes the Create Team cross, because they're too lazy to copy and paste.

This is your chance to be an armchair historian. Change the world – one detail at a time!

Create