“Reality can be beaten with enough imagination.”
– Mark Twain
In previous articles I've mentioned parallel realities that various theories point toward, but if they really do exist is there some way you could travel between them? 

As it happens we may be in luck. In 1935 Albert Einstein and Nathan Rosen working together on the theory of gravity, came me out with the esoteric concept of a wormhole. To explain the principle of what this is, if you think of our universe as a flat plane and another reality on a plane below it, the wormhole is an effectively a tunnel that can directly link these otherwise separate realities. Now before you get too excited at the idea of an intergalactic tunnel between parallel dimensions, there are some serious technical problems that need to be addressed. 

Also, it isn’t only Einstein and Rosen who have theorised about the existence of wormholes. They crop up in quantum mechanics (the study of the very small) and scientists like Stephen Hawking have proposed that we are actually surrounded by them. Now before you started glancing nervously around worried that you may be about to be sucked into a parallel reality, let me reassure you. These sort of wormholes are infinitesimally small, tinier than even atoms, constantly forming in something called quantum foam, to link different places and even different times, before disappearing again. Now obviously these tunnels are far too small for a human to pass through (you can stop looking nervously over your shoulder now), but some scientists believe it might be possible to expand one so we could.

Another idea is that we could build huge wormhole generators in space. If the entrance was placed near the Earth, the exit could be placed next to far off stars, allowing a spaceship entering to be instantly transported to the far flung point. Alternatively, if the exit was in the same place but at a different time, it would allow instant time travel between the two gates for our space ship.

So how could we build ourselves a viable machine to create a traversable wormhole that remains stable? 

The first issue is that the wormholes are inherently unstable, try to pass through one and you are going to ripped apart when they collapse. So how could we prevent this? The answer is we need to use something that hasn’t been discovered yet and it’s been labelled negative energy. With this magic missing ingredient we could keep the walls open. Simple!

The second serious hurdle to overcome is to that to get anywhere close to a useable wormhole, an incredible amount of energy is required. How much? We are talking the power of harnessed stars. That’s quite a power bill.

So unfortunately for now in practical terms creating useable wormholes seems a way off. In the meantime we’ll just have to rely on science fiction to fire our imaginations about the possibilities of travel between parallel realities and time travel.

This excellent short video with Michio Kaku and narrated by no less than Morgan Freeman, explains wormholes further.