About this beam
Ride a Light Beam is the slowest fast thing on the internet. Press launch and a flash leaves Earth at exactly 299,792,458 metres per second. That number is not a measurement any more: since 1983 the metre itself has been defined by how far light travels in 1/299,792,458 of a second. So the clock and the distance on this page are the same quantity in two units.
The first second and a quarter are thrilling. The Moon is behind you before you finish reading this sentence. Then the Sun takes about eight minutes and twenty seconds, Jupiter most of an hour, Neptune an afternoon. After that the page becomes a test of a different kind: the nearest star is more than four years of real time away, and the beam does not slow down or speed up for anyone.
Because of that, this version keeps going after you close the tab. Your launch moment is saved in your browser, so you can come back next week and see what the light passed while you were asleep. If you leave it alone until early 2031, it will reach Proxima Centauri.
Where everything actually is
The planets are never at fixed distances from us. Mars can be under 60 million km away or over 390 million, depending on where both planets are in their orbits. So instead of a fixed table, the page works out where Earth, the Moon and the planets are at the moment you launch, using NASA JPL's published approximate orbital elements for the planets and a shortened version of the standard lunar series for the Moon.
Your flash is a sphere: light from a single flash goes out in every direction at once, so it reaches everything, whichever way it lies. The page also accounts for the fact that planets keep moving while the light is travelling to them. For Neptune that is several thousand kilometres, a rounding error at this scale, but it is the honest way to do it.
| Destination | Light travel time from Earth |
|---|---|
| The Moon | About 1.2 to 1.35 seconds |
| The Sun | About 8 min 10 s to 8 min 27 s through the year |
| Mars | About 3 to 22 minutes |
| Jupiter | About 33 to 54 minutes |
| Saturn | About 67 to 92 minutes |
| Neptune | About 4 to 4.3 hours |
| Voyager 1 | One full day, from 18 November 2026 |
| Proxima Centauri | About 4.25 years |
Voyager 1 and the one light-day mark
Voyager 1 launched in 1977 and is the most distant object humans have made. According to NASA, it will be one light-day from Earth on 18 November 2026: a radio signal sent to it then takes a full day to arrive, and the reply another full day to come back. The Voyager 1 marker here is an estimate, a straight-line model calibrated to that date, because the page has no live link to NASA's tracking data.
Earlier, in August 2012, Voyager 1 crossed the heliopause, the boundary where the Sun's wind gives way to interstellar space, at roughly 121.6 astronomical units. That point is on the milestone list as well.
How to use it
- Launch starts the beam from where Earth is at that instant.
- The map looks down on the solar system and zooms out as the sphere of light grows. The ring is your flash.
- The scale strip under the map is logarithmic, so every step is ten times further than the one before.
- Share this beam copies a link that shows other people the same beam, launched at the same moment.
- New beam abandons the current one. Past beams are listed so you can see how far each one got before you gave up on it.
Questions
What is Ride a Light Beam?
A free real-time space toy. Press launch and a flash of light leaves Earth at the actual speed of light, 299,792.458 km per second. Nothing is sped up: one second on the page is one second of your life and one light-second of distance. A live map and a list of milestones show the flash passing the Moon, the planets where they really are today, Voyager 1, and the nearest stars.
Does the beam keep going if I close the tab?
Yes. Light does not wait for you, so the page saves the moment you launched in your own browser. Come back tomorrow and the beam will be a day further out, with everything it passed while you were away. To start again, choose New beam. Clearing your browser data deletes the saved launch.
Are the planet distances real?
They are calculated for the exact moment, not taken from a fixed table. Planet positions come from NASA JPL's published approximate orbital elements and the Moon from a shortened standard lunar series, which is accurate to well under one percent for these distances. The page also accounts for the planets moving while the light is on its way.
When does Voyager 1 reach one light-day from Earth?
NASA expects Voyager 1 to be one light-day from Earth, about 25.9 billion kilometres, on 18 November 2026. The Voyager 1 position on this page is an estimate: a straight-line model at about 17 km per second, calibrated to that date, so treat it as close rather than exact.
Could anything actually travel this fast?
Not anything with mass. The fastest spacecraft so far, NASA's Parker Solar Probe, reached roughly 192 km per second at its closest pass of the Sun, which is about 0.064 percent of the speed of light. The comparison panel shows how far it and other things would have gone in the time your beam has been flying.
Is anything uploaded or tracked?
No. The launch time is kept in your browser's local storage and the maths runs on your device. If you share your beam, the link contains only the launch time so someone else can watch the same beam. The page uses Google Analytics for anonymous visit and button counts.
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