Travel to the past is probably impossible. But to the future? That's a different story. Cathal O'Connell considers the feasibility of physics. In 2009 the British physicist Stephen Hawking held a party for time travellers – the twist was he sent out the invites a year later. (No guests showed up.) Travel into the past is probably impossible. Even if it were possible, Hawking and others have argued that you could never travel back before the moment your time machine was built. But travel to the future? That's a different story. Of course, we are all time travellers as we are swept along in the current of time, from past to future, at a rate of one hour per hour. But, as with a river, the current flows at different speeds in different places. Science as we know it allows for several methods to take the fast-track into the future. Here's a rundown. 1. Speed This is the easiest and most practical way to get to the far future – go really fast. According to Einstein's theory of special