Why can't you see a laser bolt flying past?

The full story

The episode's narration, word for word. Numbers link to the sources below; timestamps play that moment.

Bolts you can dodge 0:00

In a lot of science fiction, a ray gun doesn't fire a beam. It fires a bolt ¹: a short, glowing streak you can watch cross the room. In the official Star Wars lore, a Jedi, using the Force, can predict incoming blaster bolts and deflect them with a lightsaber ². It looks fantastic. But if that bolt were made of laser light, you couldn't watch it fly at all ^3,4. So why not?

Malibu, 1960 0:28

In May 1960, at Hughes Research Laboratories in Malibu, California, Theodore Maiman built and ran the first working laser ⁵. Its heart was a rod of ruby, pumped by a flash lamp ⁵. In the journal Nature he reported that it emitted light at a wavelength of 694.3 nanometres ⁶. That's a deep red, just inside the range of colours your eyes can see ^7,6. So the very first laser was a visible one ^7,6.

How fast is light? 1:00

Now, the speed. Light in a vacuum travels at exactly 299,792,458 metres per second, a number that is now fixed by definition ³. That's almost three hundred thousand kilometres every second ³. Across a five-metre room, light takes about seventeen billionths of a second ³. Across a kilometre of battlefield, it takes just over three millionths of a second ³.

How fast is your eye? 1:33

Now your eye. It gathers light over a short window of time and adds it up ⁴. Vision scientists call this temporal summation ⁴. For the cones you see with in daylight, that window lasts about ten to fifteen thousandths of a second ⁴. For the rods you rely on in the dark, it can stretch to a tenth of a second ⁴. It's why, in bright light, a lamp flickering faster than about sixty times a second looks perfectly steady ⁴. Anything that begins and ends inside one window is merged into a single moment ⁴.

Three thousand laps 2:09

In a hundredth of a second, ten milliseconds, the shortest window we'll give your eye, light covers about three thousand kilometres ^3,4. It could cross that kilometre of battlefield about three thousand times, or your room about six hundred thousand times ^3,4. Even an eye ten times quicker would see light make three hundred crossings in a single glimpse ^3,4. For you to watch a bolt cross the room over, say, a tenth of a second, it would have to dawdle along at fifty metres a second ³. That's about six million times slower than light ³.

The slowest fastest camera 2:46

So has anyone ever watched light move? In 2011, researchers at the MIT Media Lab, among them Andreas Velten and Ramesh Raskar, built a system that records one trillion exposures per second ⁸. With it they made a slow-motion video of a burst of light travelling the length of a one-litre bottle and bouncing off the cap ⁸. The whole event lasts about a nanosecond, a billionth of a second ⁸. Yet gathering the data took about an hour, because the same flash had to be repeated over and over ⁸. Raskar called it the world's slowest fastest camera ⁸.

A bolt becomes a line 3:26

So suppose a weapon fired a short flash instead of a steady beam. A flash lasting one billionth of a second is about thirty centimetres long in flight, about the length of a school ruler ³. But it crosses the kilometre in about three millionths of a second ³. Every bit of light it sends your way arrives inside a single window of your eye ^3,4. At best, you'd see a faint line appear along the whole path at once, never a bolt in motion ^3,4.

A beam you can't see 3:57

And even a steady beam has a second problem. Your eye can only see light that actually reaches it ⁹. A laser's light heads forward, so if you're standing off to the side in clean air, almost none of it comes your way ^9,10. You'd see the bright spot where it lands, but not the path in between ⁹. For the path to show, something along it has to knock some light sideways, toward you ⁹.

Smoke, dust and searchlights 4:24

That's why searchlight beams show up in fog and smoke: the particles scatter light toward you, an effect called the Tyndall effect ⁹. Even the molecules of the air scatter a little, much more for blue than red: that's Rayleigh scattering, and it's why the sky is blue ¹⁰. Blue light at 450 nanometres is scattered almost six times more strongly than red at 700 ¹⁰. Bigger particles, like smoke, dust and water droplets, scatter strongly and fairly evenly across colours: that's Mie scattering ¹⁰. So a beam is faint in clean air, and shows up clearly in a smoky room ^9,10.

A laser goes to sea 5:06

Real laser weapons now exist ^11,12. In 2014, the US Navy installed one called LaWS aboard USS Ponce in the Persian Gulf, with a reported beam power of about thirty kilowatts ¹². Between September and November it hit targets mounted on a speeding small boat and shot a ScanEagle drone out of the sky ¹¹. The Navy's chief of research put the cost at less than a dollar a shot ¹¹. By December, the Navy had declared it operational ¹².

Light past red 5:39

Here's the third problem. Your eyes detect light only from about 380 to 700 nanometres, violet to red ⁷. Maiman's ruby sat just inside the red end ^7,6. Many powerful modern lasers sit just outside it ^13,14. A common type, the neodymium YAG laser, emits infrared light at 1,064 nanometres, about one and a half times the longest wavelength you can see ^13,7. Lasers built from glass fibres doped with ytterbium typically work around one micrometre, also infrared ¹⁴. To your eye, that light simply isn't there ⁷.

Invisible to the naked eye 6:21

In February 2022, at White Sands Missile Range in New Mexico, the Navy tested a laser built by Lockheed Martin against a drone standing in for a cruise missile ¹⁵. The Navy said its laser shot a high-energy beam invisible to the naked eye ¹⁵. Then a fiery orange glow flared on the drone, and smoke poured from its engine ¹⁵. In the Navy's own telling, what showed was the glow on the target, not the beam ¹⁵.

A pound coin at a kilometre 6:51

In January 2024, Britain's Ministry of Defence announced that its DragonFire laser had made the UK's first high-power firing of a laser weapon against aerial targets, at the Hebrides Range in Scotland ¹⁶. It said the precision needed is like hitting a one-pound coin from a kilometre away, at typically under ten pounds a shot ¹⁶. DragonFire is built from bundles of doped glass fibres, and its range is classified ^16,17. There's an Australian thread to this story too ¹⁸. In March 2025, QinetiQ announced that it and Australia's Defence Science and Technology Group had demonstrated an Australian-first prototype of a high-power laser optical chain in Adelaide, drawing on its British colleagues' DragonFire expertise ¹⁸.

What a laser fight really looks like 7:43

So a real laser fight in clear air would look like almost nothing: no bolts, just a target that heats, glows and fails ^12,15. Because the light arrives almost instantly, there's no need to aim ahead of a moving target the way a missile has to ¹². Dust, smoke, salt and water vapour in the air absorb and scatter a laser's light, and that cuts its range ¹². If the beam were visible, the very haze that would let you see it would be stealing its power ^9,12.

What the films say they are 8:14

So why do films use bolts? A beam you can't see, crossing faster than you can blink, makes for a baffling fight scene. And the official Star Wars Databank, written from inside the story, isn't entirely sure what blasters fire ^1,19. It calls blaster-pistol fire cohesive bursts of light-based energy called bolts ¹. Yet it calls the stormtroopers' rifle shot a red plasma blast ¹⁹. If a bolt is plasma rather than light, it doesn't have to move at the speed of light, and that's the films' own escape hatch ^1,19.

A film that did its homework 8:50

Some films do their homework. In 1987, chemists Mario Fajardo and V A Apkarian, at the University of California, Irvine, published a paper measuring laser gain in solid xenon laced with chlorine ²⁰. They wrote that such crystals might promote this kind of laser from the realm of science fiction to that of science fact ²⁰. Their footnote for science fiction was the 1985 film Real Genius, through its scientific consultant, Martin Gundersen ^20,21.

A word on safety 9:27

Real lasers deserve respect. Your blink reflex, the eye's defence against bright light, takes about a quarter of a second ¹³. In that time, light travels about seventy-five thousand kilometres ^3,13. The US workplace safety regulator is blunt: direct exposure of the eye to a laser beam should always be avoided, no matter how low the power ¹³. In the US, laser products that emit light you can't see must be labelled with a warning for invisible radiation ¹³.

So, why can't you see it? 10:00

So why can't you see a laser bolt flying past? Because light could cross a battlefield thousands of times while your eye gathers a single moment ^3,4. Because a beam only shows where something scatters it toward you ^9,10. And because the beams of real weapon lasers can be invisible to the naked eye anyway ^14,15. Films give us bolts because a story needs something to watch, and that's a fair trade. Next time: can anything travel faster than light?

Sources

Every factual claim in the episode is tied to one of these. Spotted an error? Tell us.

1. StarWars.com Databank, "Blaster Pistol" (Lucasfilm) — starwars.com
2. StarWars.com Databank, "Lightsaber" (Lucasfilm) — starwars.com
3. NIST, CODATA Value: speed of light in vacuum (2022 CODATA recommended values) — physics.nist.gov
4. Michael Kalloniatis and Charles Luu, "Temporal Resolution", Webvision: The… — webvision.med.utah.edu
5. IEEE Milestone, "First Working Laser, 1960", Engineering and Technology History Wiki — ethw.org
6. T. H. Maiman, "Stimulated Optical Radiation in Ruby", Nature 187, 493–494 (6 August… — nature.com
7. NASA Science, "Visible Light" (Tour of the Electromagnetic Spectrum) — science.nasa.gov
8. Larry Hardesty, "Trillion-frame-per-second video", MIT News, 13 December 2011 — news.mit.edu
9. OpenStax, Chemistry 2e, section 11.5 "Colloids" (Tyndall effect, Figure 11.30) — openstax.org
10. R. Nave, HyperPhysics, "Blue Sky and Rayleigh Scattering" (with Mie scattering),… — hyperphysics.phy-astr.gsu.edu
11. David Smalley, "Historic Leap: Navy Shipboard Laser Operates in Persian Gulf", Office… — onr.navy.mil
12. Ronald O'Rourke, "Navy Shipboard Lasers: Background and Issues for Congress",… — everycrsreport.com
13. OSHA Technical Manual, Section III, Chapter 6, "Laser Hazards", US Occupational Safety… — osha.gov
14. RP Photonics Encyclopedia, "Ytterbium-doped Laser Gain Media" — rp-photonics.com
15. Warren Duffie, "Laser Trailblazer: Navy Conducts Historic Test of New Laser Weapon… — onr.navy.mil
16. UK Ministry of Defence and Dstl, "Advanced future military laser achieves UK first",… — gov.uk
17. David Szondy, "Declassified video shows DragonFire laser weapon in action", New Atlas,… — newatlas.com
18. QinetiQ, "QinetiQ demonstrates Australian-first laser technology to enhance sovereign… — qinetiq.com
19. StarWars.com Databank, "E-11 Blaster Rifle" (Lucasfilm) — starwars.com
20. Mario E. Fajardo and V. A. Apkarian, "Stimulated Radiative Dissociation and Gain… — chem.ps.uci.edu
21. USC Viterbi School of Engineering, faculty directory, "Martin A Gundersen" (Professor… — viterbi.usc.edu

Researched and scripted with AI assistance, fact-checked claim by claim, with synthetic narration and diagrams drawn in code. How we make episodes.