In 1994, physicist Miguel Alcubierre proposed a radical technology that would allow faster travel than light: the warp unit, a hypothetical way to circumvent the final speed limit of the universe by bending the fabric of reality.
It was an interesting idea – even NASA researched it at the Eagleworks lab – but Alcubierre’s proposal contained issues that seemed insurmountable. Now, a recent paper by American physicists Alexey Bobrick and Gianni Martire has solved many of these problems and generated a lot of buzz.
But while Bobrick and the Martyr have managed to substantially demystify warp technology, their work actually suggests that a journey faster than light will remain within the reach of beings like us, at least for the time being.
There is, however, a silver lining: warp technology can have radical applications beyond space travel.
Throughout the universe?
The story of warp impulses begins with Einstein’s crowned realization: general relativity. The equations of general relativity capture how space-time – the very fabric of reality – bends in response to the presence of matter and energy, which in turn explains how matter and energy move.
General relativity places two constraints on interstellar travel. First, nothing can be accelerated by the speed of light (around 300,000 km per second). Even traveling at this dizzying speed would take us another four years to reach Proxima Centauri, the closest star to our Sun.
Second, the clock of a spacecraft traveling close to the speed of light would slow down compared to a clock on Earth (this is known as time dilation). Assuming a constant state of acceleration, this makes it possible to travel with the stars. One can reach a distant star 150 light-years away in life. However, the catch is that when someone returns, more than 300 years will have passed over the Earth.
A new hope
This is where Alcubierre came in. He argued that the mathematics of general relativity allows “warp bubbles” – regions where matter and energy were arranged in such a way as to bend space-time in front of the bubble and extend it backwards in a way that allowed an area ” planes ”inside the balloon to move faster than light.
Read more: Don’t stop me now! Superluminal journey into Einstein’s universe
To have an understanding of what “flat” means in this context, keep in mind that space-time is like a kind of rubber mat. The carpet curves in the presence of matter and energy (think about putting a bowling ball on the mattress). Gravity is nothing more than the tendency of objects to roll into the depths created by things like stars and planets. A flat region is like a part of the carpet with nothing on it.
Such action would also avoid the uncomfortable consequences of time dilation. One could make a round trip in the deep space and still be greeted by the closest and dearest home.
A strange space-time
How does the Alcubierre device work? Here the discussion is often based on analogies, because mathematics is so complex.
Imagine a rug with a cup on it. You’re on the carpet and you want to get to the cup. You can cross the carpet or pull the carpet towards you. The warp unit is like dragging space-time to get closer to your destination.
But the analogies have their limits: a warp unit doesn’t really pull your destiny towards you. It contracts space-time to make your journey shorter. There is only less carpet between you and the cup when you turn on the unit.
Alcubierre’s suggestion, although mathematically rigorous, is difficult to understand on an intuitive level. Bobrick and the Martyr’s work is ready to change all that.
Ship’s blunders
Bobrick and Martyr show that any warp unit must be a shell of material in a constant state of motion, encompassing a flat region of space-time. The energy of the shell modifies the properties of the space-time region inside it.
This may not sound like much of a discovery, but until now it wasn’t clear what warp units might be, physically speaking. Their work tells us that a warp unit is, somewhat surprisingly, like a machine. A machine is also an energy shell (in the form of matter) that comprises a flat region of space-time. The difference is that getting into a car doesn’t make you grow old faster. However, this is the kind of work a warp unit could do.
Using their simple description, Bobrick and Martyr demonstrate a method for using Einstein’s general relativity equations to find space times that allow for arrangements of matter and energy that would act as warp bubbles. This gives us a mathematical key to finding and classifying warp technologies.
Their work manages to address one of the basic problems for warp units. To balance the equations, Alcubierre’s device works on “negative energy” – but we have not yet discovered viable sources of negative energy in the real world.
Applied Physics
Worse, the negative energy requirements of Alcubierre’s device are huge. According to some estimates, all the energy in the known universe would be needed (although subsequent works decrease the number slightly).
Bobrick and Martyr show that a warp impulse could be made from positive energy (ie “normal” energy) or from a mixture of negative and positive energy. That being said, the energy requirements would still be huge.
If Bobrick and the Martyr are right, then a warp unit is just like any other moving object. Finally, it would be subject to the universal speed limit imposed by general relativity and would need some sort of conventional propulsion system to accelerate it.
The news is getting worse. Many types of warp units can change the space-time inside only in a certain way: slowing down the passenger’s clock exactly the way it makes a trip into deep space a problem.
Bobrick and Martyr show that some warp units could travel faster than light, but only if they are already created by traveling at this speed – which is not helpful for any ordinary person hoping for a little interstellar tourism.
The final game
Remember that a warp unit can change the flat space-time region it encloses. It can, in particular, speed up or slow down a clock inside the unit.
Consider what it would mean to have such an object available. Do you want to put someone with a terminal illness on the ice? Put them in a warp unit and slow down their watch. From their perspective, a few years will pass, while a hundred years will pass on Earth – enough time to find a cure.
Read more: The art and beauty of general relativity
Do you want to grow your crops overnight? Put them in a warp unit and speed up the clock. It will take a few days for you and a few weeks for your seedlings.
There are even more exotic possibilities: by rotating space-time inside a unit, a battery capable of retaining huge amounts of energy can be produced.
Traveling faster than light remains a distant dream. But warp technology would be revolutionary in itself.