HUMANITY+

Bringing you tomorrow, today

FUTUROLOGY, SPACE

THE ALCUBIERRE WARP DRIVE: SCIENCE FICTION VS SCIENCE FACT

IN BRIEF

Science fiction often serves as a curiosity catalyst for a lot of technological innovation. One such example is this Alcubierre Warp Drive, that would absolutely revolutionize the capability of humans to traverse the stars.

It’s always a welcome thing to learn that ideas that are commonplace in science fiction have a basis in science fact. Cryogenic freezers, laser guns, robots, silicate implants… and let’s not forget the warp drive! Believe it or not, this concept – alternately known as FTL (Faster-Than-Light) travel, Hyperspace, Lightspeed, etc. – actually has one foot in the world of real science.

In physics, it is what is known as the Alcubierre Warp Drive. On paper, it is a highly speculative, but possibly valid, solution of the Einstein field equations, specifically how space, time and energy interact. In this particular mathematical model of spacetime, there are features that are apparently reminiscent of the fictional “warp drive” or “hyperspace” from notable science fiction franchises, hence the association.

WHAT IS WARP DRIVE?

In 1994, physicist Miguel Alcubierre proposed a new kind of technology that would allow us to travel 10 times faster than the speed of light…without actually breaking the speed of light. Sound confusing? Well here’s the key: The Alcubierre drive does not actually propel the ship to speeds exceeding light; instead, it uses the deformation of spacetime permitted by General Relativity to warp the universe around the vessel.

Essentially, when the drive is activated, spacetime behind the vessel expands, and spacetime in front of the vessel contracts (if you are having a problem envisioning this, think about the inflation of the universe: Space itself is expanding). In this respect, the path taken becomes a time-like free-fall. In a way, you step out of space and time or jump through it. The ship hums along in a little bubble of space, and neither the passengers nor the vessel encounter inertial effects.

This form of travel would make space flight significantly faster. For example, a trip to the nearest star (Proxima Centauri), which rests some four light-years from Earth, would ordinarily take thousands of years. However, with the Alcubierre drive, it would take a little under five months. For those of us who have a mental breakdown on 10 hour plane flights, 5 months might still seem like quite a bit of travel time; however, when we are talking about the vast cosmic distances between Earth and Proxima Centauri, a 5 month trip would be an achievement of monumental proportions (keep in mind, it took Curiosity 8 months just to reach Mars, which is in our own solar system).

Most notably, this method of travel does not involve time dilation. Ordinarily, time slows down as you come closer to the speed of light. So a person traveling really fast might only age 5 months, while the rest of the universe ages 5 million years. But this doesn’t happen with the Alcubierre drive. Since time is also warped, it passes the same for both the traveler and those left behind on Earth.

Of course, there are some problems we’ll need to overcome first.

BACKGROUND:

Since Einstein first proposed the Special Theory of Relativity in 1905, scientists have been operating under the restrictions imposed by a relativistic universe. One of these restrictions is the belief that the speed of light is unbreakable and hence, that there will never be such a thing as FTL space travel or exploration.

Visualization of a warp field, according to the Alcubierre Drive. Credit: AllenMcC
Visualization of a warp field, according to the Alcubierre Drive. Credit: AllenMcC

Even though subsequent generations of scientists and engineers managed to break the sound barrier and defeat the pull of the Earth’s gravity, the speed of light appeared to be one barrier that was destined to hold. But then, in 1994, a Mexican physicist by the name of Miguel Alcubierre came along with proposed method for stretching the fabric of space-time in a way which would, in theory, allow FTL travel to take pace.

CONCEPT:

To put it simply, this method of space travel involves stretching the fabric of space-time in a wave which would (in theory) cause the space ahead of an object to contract while the space behind it would expand. An object inside this wave (i.e. a spaceship) would then be able to ride this region, known as a “warp bubble” of flat space.

This is what is known as the “Alcubierre Metric.” Interpreted in the context of General Relativity, the metric allows a warp bubble to appear in a previously flat region of spacetime and move away, effectively at speeds that exceed the speed of light. The interior of the bubble is the inertial reference frame for any object inhabiting it.

Since the ship is not moving within this bubble but is being carried along as the region itself moves, conventional relativistic effects such as time dilation would not apply. Hence, the rules of space-time and the laws of relativity would not be violated in the conventional sense.

Artist’s concept of a spacecraft using an Alcubierre Warp Drive. Credit: NASA
Artist’s concept of a spacecraft using an Alcubierre Warp Drive. Credit: NASA

One of the reasons for this is because this method would not rely on moving faster than light in the local sense, since a light beam within this bubble would still always move faster than the ship. It is only “faster than light” in the sense that the ship could reach its destination faster than a beam of light that was traveling outside the warp bubble.

DIFFICULTIES:

However, there is are few problems with this theory. For one, there are no known methods to create such a warp bubble in a region of space that would not already contain one. Second, assuming there was a way to create such a bubble, there is not yet any known way of leaving once inside it. As a result, the Alcubierre drive (or metric) remains in the category of theory at this time.

Mathematically, it can be represented by the following equation: ds2= – (a2 – BiBi) dt2 + 2Bi dxi dt + gijdxi dxj, where a is the lapse function that gives the interval of proper time between nearby hypersurfaces, Bi is the shift vector that relates the spatial coordinate systems on different hypersurfaces and gij is a positive definite metric on each of the hypersurfaces.

ATTEMPTS AT DEVELOPMENT:

In 1996, NASA founded a research project known as the Breakthrough Propulsion Physics Project (BPP) to study various spacecraft proposals and technologies. In 2002, the project’s funding was discontinued, which prompted the founder – Marc G. Millis – and several members to create the Tau Zero Foundation. Named after the famous novel of the same name by Poul Anderson, this organization is dedicated to researching interstellar travel.

 

In 2012, NASA’s Advanced Propulsion Physics Laboratory (aka. Eagleworks) announced that they had begun conducting experiments to see if a “warp drive” was, in fact, possible. This included developing an interferometer to detect the spatial distortions produced by the expanding and contracting space-time of the Alcubierre metric.

The team lead – Dr. Harold Sonny White – described their work in a NASA paper titled Warp Field Mechanics 101. He also explained their work in NASA’s 2012 Roundup publication:

“We’ve initiated an interferometer test bed in this lab, where we’re going to go through and try and generate a microscopic instance of a little warp bubble. And although this is just a microscopic instance of the phenomena, we’re perturbing space time, one part in 10 million, a very tiny amount… The math would allow you to go to Alpha Centauri in two weeks as measured by clocks here on Earth. So somebody’s clock onboard the spacecraft has the same rate of time as somebody in mission control here in Houston might have. There are no tidal forces, no undue issues, and the proper acceleration is zero. When you turn the field on, everybody doesn’t go slamming against the bulkhead, (which) would be a very short and sad trip.”

In 2013, Dr. White and members of Eagleworks published the results of their 19.6-second warp field test under vacuum conditions. These results, which were deemed to be inconclusive, were presented at the 2013 Icarus Interstellar Starship Congress held in Dallas, Texas.

 

When it comes to the future of space exploration, some very tough questions seem unavoidable. And questions like “how long will it take us to get the nearest star?” seem rather troubling when we don’t make allowances for some kind of hypervelocity or faster-than-light transit method. How can we expect to become an interstellar species when all available methods with either take centuries (or longer), or will involve sending a nanocraft instead?

At present, such a thing just doesn’t seem to be entirely within the realm of possibility. And attempts to prove otherwise remain unsuccessful or inconclusive. But as history has taught us, what is considered to be impossible changes over time. Someday, who knows what we might be able to accomplish? But until then, we’ll just have to be patient and wait for future research.

Warp drive. It is a technology that humanity has dreamed about for years; however, in reality, it is more than just a dream—a number of scientists have long speculated about how such devices would actually work. Unfortunately, the ideas are largely just thought experiments, and most experts don’t think that this technology is likely to develop anytime soon (if at all).

But before I start raining on anyone’s parade, let’s break this technology down a bit.

 

LET’S DO THE WARP DRIVE

nb
Hypothetically, this device could propel a ship to speeds exceeding the speed-of-light. Image: Harold White

The first problem is that this Drive requires prohibitive amounts of energy (a ball of negative energy densities the size of Jupiter, to be exact). However, scientists reworked Alcubierre’s equations and concluded that, by oscillating the warp bubble and altering the shape of the vessel, the amount needed to create a warp bubble is reduced to a mere 500 kilograms, which is about the size of the Voyager spacecraft (NASA’s Voyager spacecraft…not Captain Janeway’s). This is still a lot.

Also, any people or objects at the destination point will be gamma ray and high energy particle blasted into oblivion. And we don’t just mean people; we’re talking about the complete and utter annihilation of whole star systems…yeah, a bit of a minor hang-up.

A visualization of a warp field. The ship rests in a bubble of normal space.
A visualization of a warp field. The ship rests in a bubble of normal space. Source

There are a plethora of high-energy particles flying throughout the cosmic void, and research indicates that some of these particles would get swept up in the craft’s warp field (bubble of space) and remain trapped. When the ship reenters normal space, the particles would be released. Relativity indicates that there is no upper limit to the amount of energy an Alcubierre drive could pick up. So travelers on their way to Proxima Centauri could annihilate the system upon their arrival. Even worse, re-positioning the vessel won’t help, as this death ray might be projected in all directions simultaneously.

However, don’t be too upset. Scientists are still crunching the numbers to see if this technology is really as dangerous as feared. And even if it is super dangerous, it doesn’t mean that we can’t use it to seek out new life and new civilizations…it just means that we might accidentally destroy said new life and new civilizations when we get there.

So there we are. We’d need a huge amount of a energy (a kind of energy that may or may not exist), and we might kill everything. All the same, Alcuberrie’s thought experiment has lead to a number of interesting other thought experiments in quantum field theory, and scientists will likely be producing papers addressing these idea for some time. We’ll continue to cover them as they come out, and though things may look painfully dismal for this technology, who knows what the future may hold.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: