In science fiction, like the show Star Trek, warp drives move spacecraft across galaxies very quickly. While many things that were once in science fiction are now real — like submarines, touchscreens, bionic limbs, and credit cards — warp drives still seem like something that may be possible in the future. The idea relies on traveling faster than light, but everyone knows that “nothing can travel faster than light” even if they don't know much about physics.
But some determined physicists are not put off by things that seem impossible. A group of researchers in the US have now released a study that has shown through calculations that “classic warp drive spacetimes can be made to satisfy the energy conditions” in certain situations. Basically, if the math is correct, the physicists argue that a warp drive could be possible. However, we don't have the technology right now to make this theory a reality.
“This study changes the conversation about warp drives,” said lead author Dr. Jared Fuchs, a physicist at the University of Alabama, Huntsville. “By demonstrating a first-of-its-kind model, we’ve shown that warp drives might not be relegated to science fiction.”
Is a warp drive more than just a dream?
Warp drive technology involves the control of spacetime, a concept foreseen by Albert Einstein’s theory of relativity. Rather than going faster than light — which is still impossible according to current laws of physics — warp drives theoretically allow for the expansion and contraction of spacetime itself. A spacecraft with a warp drive would create a bubble of flat spacetime around itself, contracting space in front and expanding space behind, essentially moving the ship through space at superluminal (faster-than-light) speeds.
The idea became popular in 1994 when physicist Miguel Alcubierre suggested what is now called the Alcubierre Drive. Alcubierre’s model proposed that a spacecraft could create and ride a wave of spacetime to achieve apparent faster-than-light travel without breaking the principles of relativity. However, the main difficulty lies in the energy requirements and exotic matter needed to create such a space-time bubble. Currently, both of these are beyond our technological capabilities.
For instance, an Alcubierre Drive needs negative energy, a concept that goes against conventional physics as we know it. This refers to a hypothetical type of energy that would have unusual (and completely impossible) properties, including a negative mass. With negative mass, if you push something, it accelerates toward you. If that seems like it makes no sense, that’s because it doesn't.
The existence of negative energy would go against several established principles. One of these is the weak energy condition, which says that the energy density in any frame of reference must be non-negative. Einstein’s general relativity specifically prohibits negative mass.
A new warp drive
In their new study, the researchers propose a new model for a warp drive, one that doesn’t use Alcubierre’s complicated ideas. Even more importantly, it does not disobey general relativity.
The researchers used a new computer tool, Warp Factory, to investigate and create the spacetime metrics needed for the warp drive. They start their design with a Minkowski background (which is flat spacetime with no gravity or curvature) and then add a stable matter shell (a layer of regular, non-exotic matter arranged in a specific way around the spaceship) with a carefully distributed shift vector (a mathematical device used in the description of spacetime that determines how spacetime is being “shifted” or modified around the spacecraft). Minkowski background (flat spacetime with no gravity or curvature) and adds a stable matter shell (a layer of regular, non-exotic matter arranged in a specific way around the spaceship) with a carefully distributed shift vector (a mathematical device used in the description of spacetime that dictates how spacetime is being “shifted” or modified around the spacecraft).
Together, this framework enables the warp bubble necessary for the spacetime modification. This bubble encloses the so-called “passenger region,” which is free from local spacetime curvature, allowing for motion without local acceleration. Essentially, it creates a shortcut through spacetime. Inside this bubble, spacetime is curved in a way that allows the spacecraft to move from one point to another faster than light would in normal (flat) spacetime, without the spacecraft itself having to travel at such speeds locally. geodesic motion without local acceleration. Essentially, it creates a shortcut through spacetime. Inside this bubble, spacetime is curved in a way that allows the spacecraft to move from one point to another faster than light would in normal (flat) spacetime, without the spacecraft itself having to travel at such speeds locally.
Unlike previous models, this new model adheres to all energy conditions by incorporating a regular matter shell with a positive ADM (Arnowitt-Deser-Misner) mass. This approach ensures the physical viability of the warp drive by using only known and theoretically feasible materials and mechanisms. The authors emphasize the importance of the shift vector distribution in achieving these conditions, differentiating their model from others that rely heavily on negative energy densities or superluminal speeds.
Practical considerations
The practicality of this warp drive in real-world applications remains speculative. It faces monumental engineering and technological challenges. The theoretical model, while robust within the confines of general relativity and classical physics, relies on a highly sophisticated and untested arrangement of matter and energy distributions. Achieving this on a practical scale — not to mention the enormous energy requirements and the creation of a stable warp bubble — remains far beyond our current technological ability.
“Although such a design would still require a considerable amount of energy, it demonstrates that warp effects can be achieved without exotic forms of matter,” added Dr. Christopher Helmerich, co-author of the study. “These findings pave the way for future reductions in warp drive energy requirements.”
Still, this model pushes the field forward by providing a potential roadmap for faster-than-light travel within the framework of known physics. This work could be a valuable blueprint for future research in spacetime engineering.
The findings appeared in the journal Classical and Quantum Gravity.
