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| Milky way as seen from Earth. Our Milky Way is about 87,000 light years in diameter. Image By Steve Jurvetson – Flickr, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=23906915 | First novel to use an ansible, a fictitious device to communicate over light years within a ‘reasonable’ time. Image by http://www.fantasticfiction.co.uk/images/n5/n29016.jpg, Fair use, https://en.wikipedia.org/w/index.php?curid=8376317 |
Running your Interstellar Empire
What if future technology permitted blasting at Faster than Light (FTL) were possible? It has to be. Otherwise how could we suspend our disbelief when it comes to epics of galactic empires? Such as Asimov’s Foundation series, where a psychohistorian predicts a long dark period of about 30,000 years after the inevitable fall of an empire encompassing the entire milky way.
Or you enjoy the Star Trek series or maybe you are more of a Star Wars person. In all of these, one can communicate nearly instantly with settlements in distant star systems. One can physically travel amongst them multiple times within a person’s lifetime.
Perhaps you wish to create a story set in a similar scenario. Alas, science says no communication or physical travel can exceed the speed of light. Is this a problem? Well, let’s see. Light travels at 300,000 kilometers per second. Mighty fast, right?
Depends. Light from our closest neighbor star takes over four years to reach us. Our galaxy, the Milky Way, has 100-400 billion stars contained within a spiral cluster of 87,000 light years in diameter. Sending a message from one end to the opposite end takes 87,000 years. Physically travelling, according to science, must take longer. Only massless particles, such as photons, can travel at light speed.
Alas, the quartz mountain link misspeaks regarding massless particles having zero energy. The article should have stated zero ‘kinetic’ energy. Photons have ‘photon energy’ according to electromagnetic frequency (or wavelength).
Enough said about science. Seems light speed isn’t so fast. Does it?
What are the implications? If your hero must fight at the opposite end of our galaxy, she couldn’t. When your hero first hears about the fight, the fight began 87,000 years ago. The fight had probably ended by the time your hero first hears about it. But if FTL communications and travel were possible, your hero could join the fight.
What’s the answer to creating a story spanning a galaxy? Simple, permit FTL communications and travel. Many authors do.
“But hold on there, Mister Spoiler,” you might say, “I want to stick to the plausible.”
Could you?
Depends. Let’s find out.
Is FTL Possible?
Conventional science states the universe must have a speed limit and this happens to be the speed of light. Most accepted physics says so. To quote Why Is There a Maximum Speed Limit in the Universe?, “And so it is for the cosmic speed limit; we cannot make it speedier.”
But, wait. What about the expansion of space? Objects located 14 billion light-years away from us, recede from us at a speed of 300,000 km/s, or just about the speed of light. An object 33 billion light-years away recedes at a speed of 708,000 km/s, or more than double the speed of light. Wouldn’t this contradict the claim of light speed being the maximum possible?
The situation of our expanding universe is more subtle. The Big Think article states: “In reality, these objects aren’t moving through the Universe at that speed at all, but rather the space between bound objects is expanding. The effect on the light is equivalent — it gets stretched and redshifted by identical amounts — but the physical phenomenon causing the redshift is due to the expanding Universe, not from the object speeding away through space.”
We could interpret this to mean the speed limit only applies to moving relative to space. There is more however.
Sabine Hossenfelder, a popular science communicator and YouTuber argues extensively why FTL is possible. Warning, the argument is quite extensive. I summarized the essence of her argument below.
According to Sabine Hossenfelder, Einstein’s theories do not imply that faster than light travel is forbidden. The problem is that one cannot accelerate from below the speed of light to above the speed of light. A second issue, she claims, is that mathematical infinity for something doesn’t imply an physical impossibity. This apparently applies for mathematics regarding black holes, which most scientists say do exist. Her third point is that there is a counterexample for an object with any mass requiring an infinite amount of energy to reach the speed of light.
Her third point concerns the nature of matter and the nuclear forces holding an atomic nucleus together. People, technically, are almost entirely made of pure energy. Particles have matter only if they get dragged while moving through the Higgs field. In the early universe none of the particles had mass and could move at the speed of light. Later, they could not. Perhaps something can be done about this Higgs field? Which Sabine does not recommend.
She also discusses time paradoxes, in which she argues there’s nothing weird about you being able to deliver a message to your younger self. She states Einstein’s special relativity (where time paradoxes apply) doesn’t apply to reality because special relativity doesn’t contain gravity. Einstein’s general relativity includes gravity, however. Sabine goes on to argue why time-travel paradoxes do not apply to our universe, yet is consistent with general relativity.
Finally she argues that general relativity is incomplete because a theory of quantum gravity is yet to be developed. Sabine isn’t alone in her assertions. Astrophysicist Erik Lentz argues FTL is possible for different reasons.
Although massed particles cannot travel at FTL, space-time can. He suggests the possibility of bending space-time into a bubble of negative energy. There are too certain theoretical ways to employ negative energy for FTL. Lentz also mentions a new class of hyper-fast solitons – a kind of wave that maintains its shape and energy while moving at a constant velocity (and in this case, a velocity faster than light).
Hypothetical Methods for FTL
Here, I will quote from a Wikipedia article about FTL to list possible methods. “Speculative faster-than-light concepts include the Alcubierre drive, Krasnikov tubes, traversable wormholes, and quantum tunneling. Some of these proposals find loopholes around general relativity, such as by expanding or contracting space to make the object appear to be travelling greater than c (symbol c means speed of light). Such proposals are still widely believed to be impossible as they still violate current understandings of causality, and they all require fanciful mechanisms to work (such as requiring exotic matter)” Italics are mine.
Because many have already offered much on the topic, I list some other links I’ve found informative because they are more recent.
https://quartzmountain.org/article/could-ftl-travel-be-possible
https://quartzmountain.org/article/what-is-the-future-of-light-travel
World-Building Implications
Given that some scientists have offered the plausibility of FTL, writers, can justify using it. In my opinion, a serious writer, when choosing a particular method, must work out the implications in their particular world setting.
For instance, some paranoid cultures on Earth have been ramping up their defenses against possible alien invasion. They’ve even built in a pre-emptive strike capability. Hooray, feel safer already?
Our hero notices that a star system located 500 light years from us shows signs of civilization. “Aha,” he says, “we should launch a strike.” The fleet launches with its FTL capability and arrives at the exoplanet within a month.
When they arrive, a big surprise awaits them. No civilization exists but there are ruins of a technological civilization that must have collapsed, maybe 400 years ago. Because of the 500 light-year distance, Earth had been observing that exoplanet 500 years in the past–when the civilization used to exist.
But what if that civilization hadn’t collapsed? What if they too had already launched an invading fleet with similar FTL capability? Perhaps that fleet had already arrived? Or maybe they arrive before Earth manages to launch its fleet. In these scenarios, each party doesn’t know whether the other will attack but assumes they will. This doesn’t help with peaceful coexistence.
With FTL, one will always arrive at the destination’s past. If FTL communications became possible, there would be an odd disconnect with communicating near-present information while observing the other party’s past through astronomical observation. Strange scenarios indeed.
Peter Spasov. Last updated Thursday May 29, 2025