Written by OC Wanderer, author of Destiny Among the Stars, a LitRPG sci-fi series set in the real stellar neighborhood. Published September 2, 2026.
A wave's crest can outrun light while a fresh message on the wave keeps us waiting. Add the sweeping shadow from our earlier exploration, and “faster than light” is already starting to sound like a phrase that needs more questions attached to it.
I imagine an engineer covering a whiteboard with every speed in physics that comes out above c. Somewhere among the moving patterns, galactic jets, entangled particles and expanding space, could there be a lead for a ship? I want to keep that question alive while looking closely at what each speed actually measures. Beyond those patterns, a telescope image that seems to show matter outrunning light is a particularly irresistible lead.
A fast pattern is tempting bait
The imagined laser sweep across the Moon in the shadow post reached 1.3 times the speed of light: a different ray landed on each spot, without light running sideways between them. A crest likewise marks a repeating position in a wave; the phase velocity post explored why fresh information needs a change. These patterns are wonderful bait for a would-be starship designer. Before drawing an engine around one, though, I would want to see something aboard it that actually made the journey.
A galactic jet seems to race its own light
The M87 galaxy's jet offers something much harder to dismiss than a swept dot: bright features in a stream of plasma appear to shift across the sky at four to six times the speed of light. Hubble Space Telescope pictures from 1994 to 1998 caught those shifts, and the galaxy's known distance lets astronomers convert them to apparent speeds.1 In a radio survey of 295 jets, the distribution of maximum apparent speeds peaked below five times light speed, while the fastest reached about 50 times.2 Imagine trying to reconcile that sequence of images with the familiar speed limit. This time there really is material out there, so where does the extra speed come from?
Think of a runner sprinting toward you while shouting at steady intervals: the shouts reach you bunched close together. A blob traveling at 99 percent of light speed, aimed 10 degrees off straight at us, plays a similar trick with its light. A flash it emits a year into the journey has much less distance to cover than the first flash, so they reach us only nine days apart. Squeeze a year's sideways motion into that short arrival interval and the apparent speed becomes about 6.9 times the speed of light. A faster blob, at 99.5 percent of light speed and aimed as favorably as possible, would appear to cross the sky at nearly ten times light speed.3
Working backward from the M87 speeds, the Hubble team concluded that the plasma moves at 98.6 percent of light speed or more, in a jet pointed close to our line of sight.4 I find that almost as exciting as the apparent speed: real plasma rushing along so close to c that our view compresses its journey into a startling sprint. The blob still trails its light, and a flash sent from its starting point reaches us first; the telescope's viewpoint supplies the extra apparent speed.
Entanglement offers agreement across the distance
Entanglement takes us from a trick of perspective to something stranger: two particles prepared together can produce linked results even when measured far apart. Send one to Alice and one to Bob. Each measures their particle with an instrument setting they choose and gets a string of results that looks like coin flips. Lay the lists side by side and a pattern of agreement emerges, depending on both settings. I can see why a pair of entangled particles might look so tempting to a crew waiting for news from Earth.
The remarkable part is that the agreement goes beyond a locally pre-arranged answer, like a pair of gloves sent to two cities. John Bell showed in the 1960s that such local explanations impose a ceiling, and quantum theory predicts that entangled particles can exceed it. In 2015 a team in Delft measured electron spins 1.3 kilometers apart, closing the detection and locality loopholes of earlier tests, and the agreement went over that ceiling.5 A 2013 experiment asked how fast a hypothetical influence between the two ends would have to act. Its lower limit was about 10,000 times the speed of light, under the assumption that Earth's speed in the inertial reference frame considered was below one-thousandth of c.6
The awkward question for that hopeful crew is what Bob can read while he is still waiting for Alice's list. Whatever setting she picks, and whether she measures at all, his results look like fair coin flips. He needs her record, sent by radio or another route at c or slower, to reveal the agreement. Quantum theory's measurement rules rule out a message sent through entanglement alone, a result proved in 1980.7 The correlation remains astonishing; turning it into a chosen greeting from home is where the scheme runs into trouble.
What if the distance itself is changing?
There is a way for galaxies to recede faster than light without playing the jet's perspective trick: let the space between them grow. Hubble's 1929 finding was that galaxies recede from us faster the farther away they are, in proportion to distance.8 Using a present-day expansion rate of about 70 kilometers per second for each 3.26 million light-years of distance puts the light-speed crossing at roughly 14 billion light-years, with more distant galaxies receding faster.9 That is a wonderfully unsettling scale: the distance can grow faster than a light beam locally travels through it.
In the expanding-universe picture, a galaxy can be at rest relative to its local surroundings while the space between it and us stretches. Special relativity still governs nearby measurements: a beam of light passing the galaxy travels locally at c. Yet we can see galaxies whose recession was already faster than light when they emitted the light now reaching us. In the standard cosmological model used for this calculation, the region that emitted the cosmic microwave background, the oldest light we can see, was receding at about 58 times the speed of light at that moment.10 I love the apparent contradiction: how does light ever make it here from something receding that fast? It initially loses ground, even while traveling toward us locally. As expansion evolves, some photons enter a region where recession is below light speed and finally begin closing the distance.
Changing space is where this exploration meets my fictional crew's journey. Cosmic expansion is not an engineered drive, but it gives me something more interesting to imagine than riding a shadow or mistaking a jet's image for its journey. In Book 1, when Danny starts to call a plan impossible, Ryan answers that they are "currently traveling faster than light using technology we barely understand."
What would the engineer put a circle around?
On the whiteboard I imagined, patterns, projections and correlations have each shown us something real and fascinating, without supplying a faster-than-light journey for a ship or its chosen message. The growth of distance changes the geometry itself, which makes it the entry I would circle for another look. That circle would mark a question, not a working engine: observing expanding space has not shown us how to control it around a hull.
Still, it is a thrilling question for a science-fiction author. If distance itself can change this way, what would happen if a ship could make use of it? Could a ship use the expansion of space to “travel” faster than light?
Endnotes
John A. Biretta, William B. Sparks, and Ferdinando Macchetto, “Hubble Space Telescope Observations of Superluminal Motion in the M87 Jet,” The Astrophysical Journal 520 (1999), 621–626, DOI. Faint Object Camera images at five epochs between 1994 and 1998; eight of ten superluminal features moved at 4c to 6c, and the knot HST-1 East emitted new features at 6c. ↩
Matthew L. Lister et al., “MOJAVE. XIII. Parsec-Scale AGN Jet Kinematics Analysis Based on 19 Years of VLBA Observations at 15 GHz,” The Astronomical Journal 152 (2016), 12, DOI, arXiv. Abstract: the distribution of maximum apparent jet speeds across 295 AGNs peaks below 5c, with very few above 30c, and the fastest is about 50c in the jet of PKS 0805-07. ↩
Author calculation from the apparent transverse velocity of a moving source, β_app = β sin θ / (1 − β cos θ), first derived in M. J. Rees, “Appearance of Relativistically Expanding Radio Sources,” Nature 211 (1966), 468–470, DOI. With β = 0.99 and θ = 10°: the blob travels 0.99 light-years in a year, with β cos θ = 0.97496 light-years of motion toward us. The later flash has about 0.975 light-years less to cover. Thus 1 − β cos θ = 0.02504 years between arrivals per year of blob travel (9.1 days), sideways travel β sin θ = 0.172 light-years, ratio 6.87. The maximum over θ is βγ, reached where cos θ = β; at β = 0.99 it is 7.02, while for β = 0.995, γ = 10.01 and βγ = 9.96. ↩
Biretta, Sparks, and Macchetto (1999), as in note 1: the fastest speeds require a bulk Lorentz factor of at least 6 and an orientation within 19° of the line of sight. Author calculation: β = √(1 − 1/6²) = 0.986. ↩
B. Hensen et al., “Loophole-free Bell inequality violation using electron spins separated by 1.3 kilometres,” Nature 526 (2015), 682–686, DOI. The abstract states that the experiment is free of the additional assumptions that opened loopholes in earlier tests. ↩
Juan Yin et al., “Lower Bound on the Speed of Nonlocal Correlations without Locality and Measurement Choice Loopholes,” Physical Review Letters 110 (2013), 260407, DOI, arXiv. The abstract gives a lower bound of four orders of magnitude of the speed of light, on the condition that the Earth’s speed in any inertial frame was below 10⁻³ of c. ↩
G. C. Ghirardi, A. Rimini, and T. Weber, “A General Argument against Superluminal Transmission through the Quantum Mechanical Measurement Process,” Lettere al Nuovo Cimento 27 (1980), 293–298, DOI. ↩
Edwin Hubble, “A relation between distance and radial velocity among extra-galactic nebulae,” Proceedings of the National Academy of Sciences 15 (1929), 168–173, DOI. ↩
Author calculation, distance at which v = H₀D equals c: D = c/H₀. Planck 2018 gives H₀ = 67.4 ± 0.5 km/s/Mpc (14.5 billion light-years), Planck Collaboration, Astronomy & Astrophysics 641 (2020), A6; the local distance ladder gives 73.04 ± 1.04 (13.4 billion light-years), Riess et al., The Astrophysical Journal Letters 934 (2022), L7. The two measurements disagree, so the figure in the text is rounded to “roughly 14 billion.” ↩
Tamara M. Davis and Charles H. Lineweaver, “Expanding Confusion: Common Misconceptions of Cosmological Horizons and the Superluminal Expansion of the Universe,” Publications of the Astronomical Society of Australia 21 (2004), 97–109, DOI, arXiv, full text, section 3.3. For their model (Ω_M, Ω_Λ) = (0.3, 0.7), all galaxies beyond z = 1.46 are currently receding faster than light; the paper reports hundreds already observed above that redshift and explains their superluminal recession at emission as well. Redshift measures the stretching of light to longer wavelengths during expansion. The microwave background source region was receding at 58.1c at emission in this model. Photons locally heading toward us can initially recede in proper distance, then approach once they enter a region of subluminal recession. ↩