The universe is huge. Travelling at light speed to the nearest star would take more than four years. Venturing to the other side of the galaxy? More than 100,000 years. So what's an intrepid space traveller to do?

One option is a cosmic shortcut called a wormhole, a tunnel through the fabric of space and time that can connect far-flung corners of the universe. It’s the chosen route of many fictional space travellers, including the characters in the upcoming film Interstellar, directed by Christopher Nolan.

Hopping through a wormhole would be incredibly difficult, say scientists, but they have yet to rule it out. So, what would it take in reality, and what exactly is stopping us now?

To picture a wormhole, imagine that the universe is a two-dimensional sheet. Poke two holes and curve the sheet around them to form two funnels. Stitch the ends of the funnels together, and you get a wormhole-like tube (see below).