‘You built a time machine out of a DeLorean?’ The words of soon-to-be time traveller Marty McFly to eccentric scientist Emmett Brown in Back to the Future only began to touch upon the complex issues involved.
The car itself was a good choice for a time machine in 1985 – its stainless steel body was said to have a direct and influential effect on the flux dispersal, acting as protection for its passengers and allowing for a smoother transition on re-entry. Or maybe it was just that the gull wing doors looked kind of ‘futurey’!
But the device behind the time-travelling bit wasn’t actually the DeLorean, it was Doc Brown’s flux capacitor, a gizmo which could supposedly create a gateway through time (flux). But could it really work?
The flux capacitor
The film itself is a little sketchy on the details, but one theory is that the flux capacitor could make time travel possible by using its place of origin as a point of reference to translate what the driver wants into something that the universe can understand.
To do that, it uses a colossal amount of power channelled through its three glowing rods, which could create a brace of wormholes accelerating at different velocities relative to each other, through which the DeLorean (or steam train, or other vehicle of your choice) can travel at 88mph or more, to reach a different point in time.
According to this particular theory, the space-time continuum is shown to be essentially spherical, allowing the traveller to enter the wormhole in one location in space, but emerge from it in a new location which is exactly the same in space, but entirely different in time. So you travel through time, but remain in the same relative place.
This is actually trickier than it sounds, since nothing really stays in place. We’re all constantly moving through space on this great big onion we call the world, so even a slight displacement in time would be extremely difficult to link up exactly with a particular point in space.
How much energy to power the DeLorean?
But leaving that aside, one of the key problems for the flux capacitor is energy.
Even theoretically, the amount of power needed to create a wormhole (as yet, still only a concept rather than a reality) is barely conceivable. In the film, it’s defined as 1.21 gigawatts (pronounced ‘jigawatts’ in the film) and equivalent to 1,210,000,000 watts of power. That’s an awful lot of watts, the kind you can only get from a plutonium-powered nuclear reactor (whether or not that plutonium has been liberated from terrorists), a couple of seriously huge gas turbines or, say, a bolt of lightning.
To put it into context, the nuclear power reactors in a Nimitz Class Aircraft Carrier produce 194 megawatts.
How much fuel?
So how could that work? Let’s get technical for a second. If the reactor uses (for example) Plutonium-239 (dangerously radioactive by the way), then each atom of the stuff could theoretically produce 200MeV (mega electron volts) during the fission process, equivalent to 3.2×10-11 joules of energy. With each Plutonium-239 atom having a mass of 3.29×10-25kg, you would only need a fuel mass of 1.2×10-5kg, which could conceivably fit in the boot of a DeLorean.
So long as it didn’t explode, and 1.21 gigawatts is all the power you needed, then you could conceivably power a time-travelling car. Then all you’d have to worry about are the complexities of relativity, space-time paradoxes and the impossibility of altering the future by changing history to make time travel by DeLorean a reality.