Hourwiz Explains · video notes
What If You Could Stop Time? Could You Even See?
The short answer: probably not. If you froze everything except yourself, light would freeze too, and you only see what travels into your eyes. Physicist Sean Carroll told Live Science that a time-stopping character would likely be unable to see anything, because light would no longer reach their eyes. In our light simulation, 0 of 100,000 photons reach the eye once the world is stopped.
The rule of the story
A thought experiment. This isn't a lab result. It's a “what if” with one rule, taken from physicist Sean Carroll in Live Science: if time stopped, all motion would stop too. In the video, everything freezes (air, sound, light) except the wizard.
- Why everything stops: Carroll told Live Science, “Motion is change with respect to time, so time itself can't move.”
- Why the wizard doesn't: that's the story's one cheat. Everything below follows from it.
The real thing: Harvard stopped a pulse of light
- In 2001, a Harvard team led by physicist Lene Hau stopped a pulse of light inside a small cloud of ultracold sodium atoms, using two laser beams (Harvard Gazette; Nature, 2001).
- For about a thousandth of a second. The Gazette: “Hau's team stopped light for one-thousandth of a second.”
- The light stopped when a second laser beam, aimed at right angles to the cloud of atoms, was cut off (Harvard Gazette).
- That's a trick with light inside a cloud of atoms, not a way to stop time (our note).
The lab scene in the video is our own illustration, not a photo.
Problem 1: your snap makes no sound
- Sound is moving air. NASA: “Disturbances are transmitted through a gas as a result of collisions between the randomly moving molecules in the gas.”
- Frozen air can't carry it. If the molecules can't move, they can't bump into each other, so no sound reaches you (our reasoning from NASA's explanation and the story's rule).
- Normally sound covers about 1,100 feet per second at sea level (NASA Glenn), so a friend's “hi” from 6 feet away reaches you in about 5 thousandths of a second (our math: 5.45 ms).
Problem 2: the air traps you
- On sci-fi characters who pause time for everyone else, Carroll asked: “Are you stopping the air from moving? Because if so, then you're imprisoned by the air.” (Live Science, 2021)
- In the video, the wizard walks into the frozen air like a wall.
Problem 3: could you even see?
- Seeing needs light to travel into your eye. The National Eye Institute: light passes through the cornea, “Some of this light enters the eye through an opening called the pupil”, and then the light hits the retina, at the back of the eye.
- So everything you see has to travel to you. Freeze the light between you and the world, and nothing new arrives.
- Carroll's view: a time-stopping character would also likely be unable to see anything, because light rays would no longer reach their eyes (Live Science, 2021; the magazine's paraphrase of Carroll, not a direct quote).
- Your eyes would still work. There'd just be no light reaching them.
Our take: stopping time isn't a superpower. It's a trap.
Our light simulation
Our simulation. A toy model we wrote (one small Node script, no outside libraries, run with Node v24.21.0 on Oct 18, 2026). At the moment of the freeze, 100,000 photons are already flying from a lamp to an eye 1 foot away, evenly spaced. The world then runs at a fraction of its normal speed, and the script counts how many photons reach the eye during 1 second of the wizard's own time. There's no randomness, so a rerun gives the same numbers.
| The world runs at | Photons that reach the eye |
|---|---|
| Normal speed | 100,000 of 100,000 |
| A billion times slower | 98,357 of 100,000 |
| A trillion times slower | 98 of 100,000 |
| Stopped | 0 of 100,000 |
Our simulation: slow the world down and a few photons still trickle in. Stop it, and none arrive.
The core of our script
// 3. Toy freeze simulation (deterministic): photons already in flight between a lamp and an eye 1 ft away.
// Count arrivals during 1 s of the wizard's own time at world speed s.
function freezeSim(s, nInFlight = 100000, waitS = 1) {
const d = FT;
let arrived = 0;
for (let i = 0; i < nInFlight; i++) {
const x = (i + 0.5) / nInFlight * d; // evenly spaced positions at the freeze moment
if (x + C * s * waitS >= d) arrived++;
}
return { arrived, of: nInFlight };
}An excerpt from our script. The full file is in the download below.
The slow-time ladder
Our math. The same script times two everyday trips on the wizard's own clock while the world runs slower and slower: light from a phone 1 foot from your eyes, and sound from a friend 6 feet away. Light moves at 299,792,458 meters per second (NIST); sound at about 1,100 feet per second (NASA Glenn). Rounded to 3 significant figures.
| The world runs at | Light, 1 foot | Sound, 6 feet |
|---|---|---|
| Normal speed | 1.02 billionths of a second | 5.45 thousandths of a second |
| 1,000 times slower | 1.02 millionths of a second | 5.45 seconds |
| A million times slower | 1.02 thousandths of a second | 1.52 hours |
| A billion times slower | 1.02 seconds | 63.1 days |
| Stopped | never | never |
Slow the world down a billion times, and a friend's “hi” takes about two months to cross 6 feet. Stop it, and nothing ever arrives.
What our simulation assumes
- Everything stops except you. That's the story's rule, not physics anyone can test.
- Light travels in a straight line from the lamp to the eye, at a steady speed.
- 1 foot and 100,000 photons are our choices. They make the counting easy to follow. Real light isn't 100,000 evenly spaced dots.
- It's a toy model to show the idea, not a model of how real eyes or lamps work.
Download our math
- Our script (.mjs, 4 KB): the travel times, the slow-time ladder and the freeze simulation. Run it with Node (
node stop-time-calc.mjs); it needs no outside libraries. - The script's run log (.txt, 1 KB): its own printout from Oct 18, 2026.
Edited for the web. In the script we shortened the “run from” comment and fixed one comment that described a feature the code doesn't have. The code and its output are unchanged.
The script prints a few extra lines we don't use on this page.
Images in the video
No outside photos or footage. Everything in the video, including the Harvard lab illustration, is drawn in code by Hourwiz.
Sources
Every fact on this page comes from these pages, opened on Oct 19, 2026. Things change: check the live page before you rely on it.
- Harvard Gazette, William J. Cromie (Jan. 24, 2001): Lene Hau's team stops light “Hau's team stopped light for one-thousandth of a second”; sodium atoms, two laser beams; Hau, a professor of physics at Harvard.
- Liu, Dutton, Behroozi & Hau, “Observation of coherent optical information storage in an atomic medium using halted light pulses”, Nature 409, 490–493 (2001) The paper behind the Gazette story.
- Adam Mann, “Can we stop time?”, Live Science (June 5, 2021) Sean Carroll, then a theoretical physicist at Caltech: “you're imprisoned by the air”; motion stops if time stops; a time-stopping character would likely be unable to see anything.
- NASA Glenn Research Center, Beginner's Guide to Aeronautics: speed of sound Sound travels through a gas by collisions between moving molecules; about 1,100 feet per second at sea level.
- National Eye Institute (NIH), How the eyes work Light enters the eye through the pupil and hits the retina.
- NIST CODATA, speed of light in vacuum 299,792,458 m/s (exact). Input to our script.
Stopping time is a thought experiment, and our simulation is a toy model, rounded as shown. Hourwiz is not affiliated with Harvard, Live Science, NASA, the National Eye Institute or NIST, and none of them (nor Lene Hau or Sean Carroll) made, reviewed or endorsed this page or the video.
No sponsor and no affiliate links on this page. Vendors are named so you can check them yourself, not as recommendations.
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