In cult film trilogy Back To The Future, Marty McFly and inventor Dr Emmett Brown use a DeLorean to travel through time to 21 October 2015. Of course that date is almost upon us, and IBTimes UK thought it would settle it once and for all – does anything Doc Brown say about time travel in the films make sense?

In Back To The Future II, Brown claims that if Marty's girlfriend Jennifer comes face-to-face with her future self, it could be disastrous: "I foresee two possibilities. One, coming face-to-face with herself 30 years older would put her into shock and she'd simply pass out. Or two, the encounter could create a time paradox, the results of which could cause a chain reaction that would unravel the very fabric of the space-time continuum, and destroy the entire universe!

"Granted, that's a worst-case scenario. The destruction might in fact be very localised, limited to merely our own galaxy."

### So what exactly is a space-time continuum?

Throughout the course of the movies Doc Brown feverishly speaks to Marty about a space-time continuum. He even draws a nice chalk diagram of how it affects their past and future realities. In our reality, the space-time continuum (also known as the spacetime continuum) has nothing to do with time travel. Instead it's the curvature between space and time, which is part of Einstein's theory of general relativity.

We're sorry to break this news to you BTTF fans but Einstein's theory describes a curvature between space and time, which is the stage in which things occur. Curvature causes things to move in a way that makes it look like there's a gravitational force between them, as opposed to Newton's theory, which claims that there is a force between objects.

### Space-time continuum is about gravity, not time travel

"Einstein's theory of general relativity is our best theory of gravity. Think of a flat rubber sheet. If you put a heavy weight like a shot put in the middle of the sheet, it curves, so if you then put a marble on it, it would get curved due to the dimple in the rubber sheet caused by the shot-put," Professor Jerome Gauntlett, chair in theoretical physics at Imperial College and theoretical physics consultant on the film The Theory Of Everything, told IBTimes UK.

"The space-time continuum is the rubber sheet – it is the language of gravity. They're just using those words in the movie but it has nothing to do with time travel."

However, this is not to say that physicists do not discuss the possibility of time travel – they just spend considerably more time trying to figure out how to deal with paradoxes that would make it a bad idea.

For example, the Grandfather Paradox, as touched on in BTTF, claims if you go into the past and then kill one of your ancestors, this will prevent you from being born in the future, so paradoxes do exist, but they have to do with time travel, not the space-time continuum.

Now that we've managed to completely shatter the scientific magic behind the famous films, is there anything else the experts identify as being a load of manure? Cover your eyes...

### Does the 'flux capacitor' exist?

Anyone who knows their Biffs from their Goldie Wilsons will know Doc Brown used his family fortune to fund his life's work of building a time machine, which all began in 1955 when he hit his head on a sink while hanging a clock in his bathroom.

When Doc Brown woke up, he had the idea for the "flux capacitor", a box that activates "flux compression". In 1985, Doc Brown's research enabled him to create the flux capacitor drive, thus enabling the DeLorean to travel through time upon hitting 88mph and achieve 1.21 gigawatts of power generated by plutonium, casually stolen from some Libyan terrorists he promised to build a bomb for.

Sadly, the flux capacitor doesn't exist and neither does flux compression. As Doc Brown conveniently gets interrupted while explaining how it works, this is never elaborated on in the films. Prominent physicists we spoke to also had no idea either exactly such a device could work, so your guess is as good as ours.

"You could hypothetically use plutonium to fuel a vehicle that moves incredibly fast, but this is not what we use plutonium for, as it produces electricity," Dr Christian Boehmer, who researches Einstein's equations and dark energy models for University College London (UCL)'s Department of Mathematics tells IBTimes UK.

Despite not being exactly scientifically correct about time travel the movies have done a wonderful job at predicting what life in 2015 would be like. We've looked at everything it got right – from hoverboards to drones – to the things it missed out.

Professor Jerome Gauntlett and Imperial College will be celebrating 100 years of Einstein's theory of General Relativity with physicists around the world in November.

Are you celebrating Back To The Future Day on Wednesday 21 October 2015? Let us know what you're getting up to by tweeting us @IBTimesUKTech