The point of no return
The boundary beyond which nothing, not even light, can escape. It is not a surface. Its size grows in step with the mass, as Karl Schwarzschild’s 1916 solution of Einstein’s equations showed. Try the sizes below.
- Object
- BH-1
- Field
- this page
- Opens
- where you click
- Lifetime
- until you press Esc
Black hole
A black hole that eats this page, then gives it back.
Click anywhere. Letters tear off one by one, spiral into a glowing disk and fall past the horizon. Throw one hole into another and they merge. Press Esc and a white hole puts every letter back where it was.
Runs entirely in your browser: nothing is sent or saved. Contains fast motion, screen shake and a bright flash on mergers and collapse.
5.1How to use it
Three moves.
- Open a hole. Click anywhere on this page that is not a link or a button, or press Feed this page. If your system asks for reduced motion, only the button works.
- Let it grow. It starts with letters. As it gains mass it tears off images and whole cards. Drag a hole to move it; let go while moving to throw it. Up to seven at once.
- Put it back. Esc fires a white hole and every letter flies home. Enter first collapses everything into one hole and shows a summary card.
5.2What happens
To the page.
- Tidal disruption first moments
- Letters near the hole lift off one by one and are redrawn as particles in this page’s own font and colour. The text around them stays put, so the hole leaves clean gaps.
- Accretion a few seconds
- Particles fall into orbit, stretch along their paths and heat from ember red to blue-white before they cross the horizon.
- Growth
- The hole gains mass from what it swallows. A young hole manages letters and icons; a grown one shatters images, buttons and cards.
- Merger
- Drag one hole into another. They spiral in, merge, and send out a wave that rips letters off along its front.
- Collapse Enter
- Every hole falls to the centre and eats what is left on screen, then a card shows the totals.
- White hole Esc
- Time runs backwards. Every letter flies out and lands where it was. The page underneath was never rewritten.
5.3Controls
Keys and gestures.
| Input | What it does |
|---|---|
| Click | Open a black hole where you clicked. Up to seven at once. |
| Drag a hole | Move it. Let go while moving to throw it. |
| Drag onto another hole | Merge the two. The bigger one keeps its spin. |
| Enter | Collapse everything into one hole and show the summary card. |
| Esc | White hole: restore the page and switch the black hole off. |
| R | Restore the page and keep playing. |
| A | Autopilot: the hole wanders and eats its way down the page. |
| H | Hide or show the panel in the corner. |
| M | Sound on or off. |
| P | Pause. |
| S | On the summary card: save it as a PNG. |
| On a phone | Tap to open a hole, drag a hole to move it, scroll as usual. |
5.4The real thing
What the toy borrows from.
M87* and Sagittarius A*
The Event Horizon Telescope links radio dishes around the world into one Earth-sized telescope observing at 1.3 mm. It released the first image of a black hole, M87*, on 10 April 2019: about 6.5 billion solar masses, about 55 million light-years away. The Milky Way’s own, Sagittarius A*, followed on 12 May 2022: about 4 million solar masses, about 27,000 light-years away.
Why one side is brighter
Gas circling the hole close to the speed of light looks brighter on the side moving toward us and dimmer on the side moving away. This relativistic beaming is how the EHT explains the bright crescent in the M87* ring.
Torn apart
A star that passes too close to a black hole is pulled harder on its near side than its far side and is torn apart. Part of the debris forms a disk around the hole and gives off a bright flare: a tidal disruption event.
The chirp
On 14 September 2015 LIGO detected gravitational waves from two black holes of about 36 and 29 solar masses merging into one of about 62. About three solar masses of energy left as gravitational waves, and the signal swept up from about 35 Hz to about 250 Hz in a fraction of a second. The detection was announced on 11 February 2016.
Pure theory
In general relativity a white hole is the time-reverse of a black hole: nothing can enter it, but matter and light can leave. None has ever been observed, and no known process would form one. The Esc key is the only white hole on this site.
Link
The Event Horizon Telescope is a very-long-baseline interferometer: separate telescopes, each recording against its own clock, combined afterwards. Nikolai Kardashev was among the first to propose that technique in the 1960s, and later led RadioAstron (2011–2019), which used a 10-metre radio telescope in orbit to form baselines of up to about 350,000 km. His biography has more.
5.5How big?
Pick a mass, see the horizon.
A black hole’s horizon grows in step with its mass. Choose one and compare.
ONE SUN
about 6 km across
A black hole with the Sun’s mass would be narrower than many cities.
Sizes are for non-rotating black holes of these masses; spin makes the horizon somewhat smaller. The discs are drawn on a squeezed scale so that all four fit.
5.6Under the hood
How the toy works.
- The page is never rewritten. Eaten letters are hidden with the CSS Custom Highlight API instead of being wrapped in new elements, which is why Esc can put everything back exactly.
- Glyphs keep their fonts. Each particle is drawn on a canvas in the page’s own font, size and colour until the disk heats it up.
- Real lensing, where supported. In Chromium browsers the page bends around each hole through a
backdrop-filterwith an SVG displacement map. Other browsers get the darkness without the bend. - Synthesized sound. The hum and the merger chirp are generated with Web Audio. Sound is off by default here; switch it on before you start, or press M.
- Nothing leaves your browser. No network requests, no cookies, no storage, no eval.
- One file, MIT licensed. The engine is Singularity by @shmidtqq, included with its licence. Changes for this site: the counter and summary card show characters eaten instead of “tokens ingested”, and the panel’s mass row shows images eaten.
5.7Questions
Before you feed it.
Will it break the page?
No. It hides letters and redraws them on a canvas; it does not rewrite the page. Esc restores everything, and reloading always does.
Why do the menu and buttons stop working?
While a hole is open the engine takes over clicks and most keys, so you can drag holes around. Press Esc to put the page back; then everything works again.
Does it send or store anything?
No. The engine makes no network requests, sets no cookies and stores nothing. It runs in your tab and is gone when you press Esc or reload.
Is it safe for people sensitive to flashing?
It has fast motion, screen shake and a bright full-screen flash when holes merge or collapse. If your system asks for reduced motion, clicking the page will not start it; the button still will, so only press it if you are comfortable with that.
What does the counter count?
Characters swallowed, and images. It has nothing to do with the $KARDASHEV token. The original engine counts “tokens ingested”; on this site the labels were changed to avoid confusion.
Is this a physics simulation?
No. It borrows the vocabulary of black holes, not their physics. Orbits, colours and “growth” are artistic. The real numbers are in the section above.
5.8Sources
Sources and credits
- Event Horizon Telescope Collaboration, First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole, The Astrophysical Journal Letters 875, L1 (2019). ESO release
- Event Horizon Telescope Collaboration, Sagittarius A* results, The Astrophysical Journal Letters (2022). ESO overview
- LIGO Scientific Collaboration and Virgo Collaboration, Observation of Gravitational Waves from a Binary Black Hole Merger, Physical Review Letters 116, 061102 (2016).
- NASA Science, black hole anatomy. science.nasa.gov
- Singularity v1.0.0, © 2026 shmidt (@shmidtqq), MIT License. Vendored at
assets/vendor/singularity/. github.com/shmidtqq65/singularity